Human-induced changes in animal populations and distributions, and the subsequent effects on fluvial systems

NASA Astrophysics Data System (ADS)

Butler, David R.

2006-09-01

Humans have profoundly altered hydrological pathways and fluvial systems through their near-extirpation of native populations of animal species that strongly influenced hydrology and removal of surface sediment, and through the introduction of now-feral populations of animals that bring to bear a suite of different geomorphic effects on the fluvial system. In the category of effects of extirpation, examples are offered through an examination of the geomorphic effects and former spatial extent of beavers, bison, prairie dogs, and grizzly bears. Beavers entrapped hundreds of billions of cubic meters of sediment in North American stream systems prior to European contact. Individual bison wallows, that numbered in the range of 100 million wallows, each displaced up to 23 m 3 of sediment. Burrowing by prairie dogs displaced more than 5000 kg and possibly up to 67,500 kg of sediment per hectare. In the category of feral populations, the roles of feral rabbits, burros and horses, and pigs are highlighted. Much work remains to adequately quantify the geomorphic effects animals have on fluvial systems, but the influence is undeniable.

From plot to regional scales: Interactions of slope and catchment hydrological and geomorphic processes in the Spanish Pyrenees

NASA Astrophysics Data System (ADS)

García-Ruiz, José M.; Lana-Renault, Noemí; Beguería, Santiago; Lasanta, Teodoro; Regüés, David; Nadal-Romero, Estela; Serrano-Muela, Pilar; López-Moreno, Juan I.; Alvera, Bernardo; Martí-Bono, Carlos; Alatorre, Luis C.

2010-08-01

The hydrological and geomorphic effects of land use/land cover changes, particularly those associated with vegetation regrowth after farmland abandonment were investigated in the Central Spanish Pyrenees. The main focus was to assess the interactions among slope, catchment, basin, and fluvial channel processes over a range of spatial scales. In recent centuries most Mediterranean mountain areas have been subjected to significant human pressure through deforestation, cultivation of steep slopes, fires, and overgrazing. Depopulation commencing at the beginning of the 20th century, and particularly since the 1960s, has resulted in farmland abandonment and a reduction in livestock numbers, and this has led to an expansion of shrubs and forests. Studies in the Central Spanish Pyrenees, based on experimental plots and catchments, in large basins and fluvial channels, have confirmed that these land use changes have had hydrological and geomorphic consequences regardless of the spatial scale considered, and that processes occurring at any particular scale can be explained by such processes acting on other scales. Studies using experimental plots have demonstrated that during the period of greatest human pressure (mainly the 18th and 19th centuries), cultivation of steep slopes caused high runoff rates and extreme soil loss. Large parts of the small catchments behaved as runoff and sediment source areas, whereas the fluvial channels of large basins showed signs of high torrentiality (braided morphology, bare sedimentary bars, instability, and prevalence of bedload transport). Depopulation has concentrated most human pressure on the valley bottoms and specific locations such as resorts, whereas the remainder of the area has been affected by an almost generalized abandonment. Subsequent plant recolonization has resulted in a reduction of overland flow and declining soil erosion. At a catchment scale this has caused a reduction in sediment sources, and channel incision in the secondary streams. At the regional scale, the most important consequences include a reduction in the frequency of floods, reduced sediment yields, increasing stabilization of fluvial channels (colonization of sedimentary bars by riparian vegetation and a reduction in the braiding index), and stabilization of alluvial fans. These results demonstrate the complexity and multiscalar nature of the interactions among land use and runoff generation, soil erosion, sediment transport, and fluvial channel dynamics, and highlight the need to adopt a multiscale approach in other mountain areas of the world.

Variability in fluvial geomorphic response to anthropogenic disturbance

NASA Astrophysics Data System (ADS)

Verstraeten, Gert; Broothaerts, Nils; Van Loo, Maarten; Notebaert, Bastiaan; D'Haen, Koen; Dusar, Bert; De Brue, Hanne

2017-10-01

Humans have greatly impacted the processes and intensities of erosion, sediment transport and storage since the introduction of agriculture. In many regions around the world, accelerated floodplain sedimentation can be related to increases in human pressure on the environment. However, the relation between the intensity of anthropogenic disturbance and the magnitude of change in fluvial sediment dynamics is not straightforward and often non-linear. Here, we review a number of case studies from contrasting environmental settings in the European loess belt, the Eastern Mediterranean mountain ranges and the eastern USA. Detailed field-based sediment archive studies and sediment budgets covering time periods ranging from 200 to over 5000 year, as well as the use of pollen and sediment provenance techniques, show that no overarching concept of changes in floodplain sedimentation following anthropogenic disturbance can be established. Slope-channel (dis)connectivity controls the existence of thresholds or tipping points that need to be crossed before significant changes in downstream sediment dynamics are recorded following human impact. This coupling can be related to characteristics of human pressure such as its duration, intensity and spatial patterns, but also to the geomorphic and tectonic setting. Furthermore, internal feedback mechanisms, such as those between erosion and soil thickness, further complicate the story. All these factors controlling the propagation of sediment from eroding hillslopes to river channels vary between regions. Hence, only unique patterns of fluvial geomorphic response can be identified. As a result, unravelling the human impact from current-day sediment archives and predicting the impact of future human disturbances on fluvial sediment dynamics remain a major challenge. This has important implications for interpreting contemporary sediment yields as well as downstream sediment records in large floodplains, deltas and the marine environment, in terms of changes in the drivers of environmental change.

Fluvio geomorphic set-up of Noctis Fossae in Noctis Labyrinthus of Syria-Planum Provenance, Mars

NASA Astrophysics Data System (ADS)

Chavan, A. A.; Bhandari, S.

2017-12-01

The modern era of planetary exploration has revealed fluvial or fluvial like landforms on the extraterrestrial surfaces of planets and moons of our solar system. This has posed as interesting challenges for advancing our fundamental understanding of fluvial processes and their associated landforms on the planetary surfaces especially on Mars. It has been recognized through earlier studies that the channels and valleys are extensively dissected on Mars. The Valleys are low lying, elongate troughs surrounded by elevated topography. Moreover, valley networks on Mars are the most noticeable features attesting that different geological processes and possibly climatic conditions prevailed in the past and played a vital role in formulating the Martian topography. Channel incisions which are a domino effect both tectonic and surface runoff and groundwater sapping. The components of surface runoff have been deciphered with the help of morphometric exercises. Further, the geomorphological studies of these landforms are critical in understanding the regional tectonics. The present work is an assessment of Fluvio geomorphic set-up of Noctis Fossae in Noctis Labyrinthus of Syria-Planum Provenance, Mars. This study focuses on the fluvio geomorphology of the southern highlands (00 to 400S to 850-1200W) to determine how these features were formed, which process formed these valleys and includes the probable causes resulting into the development of the topography. Keywords: Noctis Fossae; Noctis Labyrinthus; Syria Planum; Mars

Alaskan Permafrost Analogs of Martian Small Valley Networks, Thermokarst, Terrain Softening, Terraces, and Volcanic Craters

NASA Technical Reports Server (NTRS)

Kargel, Jeffrey S.; Wessels, Rick; Beget, James E.; Eddy, Thomas; Lloyd, Sandra; Macaulay, Don; Proch, Mark; Skinner, Jim; Tanaka, Kenneth L.

2004-01-01

A geomorphic landscape analog in the Bering Land Bridge National Preserve (Alaska) offers a model for Mars where (1) fluvial and alluvial deposition, volcanism, and other processes first produced a layered ice-rich upper crust, and then (2) severe permafrost conditions (mild by today's Martian standards) and heterogeneous heat flow and volcanism have modified this terrain to produce a geomorphic areal mosaic that is alternately dominated by (a) geothermal meltwater and sublimation (bottom-up heat flow) and (b) surface-driven meltwater and sublimation (top-down heat flow).

Using Fluvial Geomorphology as a Physical Template in Process-Based and Recovery Enhancement Approaches to River Management

NASA Astrophysics Data System (ADS)

Fryirs, K.

2016-12-01

In an `era of river repair' fluvial geomorphology has emerged as a key science in river management practice. Geomorphologists are ideally placed to use their science in an applied manner to provide guidance on the impact of floods and droughts, landuse and climate change, and water use on river forms, processes and evolution. Increasingly, fluvial geomorphologists are also asked to make forecasts about how systems might adjust in the future, and to work with managers to implement strategies on-the-ground. Using case study material from Eastern Australia (Bega, Hunter, Wollombi and Lockyer catchments) I will focus on how process-based understanding of rivers has developed and evolved to provide a coherent physical template for effective and proactive, river management practice. I will focus on four key principles and demonstrate how geomorphology has been, and should continue to be, used in process-based, recovery enhancement approaches to river management. How understanding the difference between river behaviour and river change is used to determine how a river is `expected' to function, and how to identify anomalous processes requiring a treatment response. How understanding evolutionary trajectory is used to make future forecasts on river condition and recovery potential, and how working with processes can enhance river recovery. How geomorphic information can be used as a physical template atop which to analyse a range of biotic processes and habitat outcomes. How geomorphic information is used to effectively prioritise and plan river conservation and rehabilitation activities as part of catchment and region-scale action plans.

Fluvial geomorphic elements in modern sedimentary basins and their potential preservation in the rock record: A review

NASA Astrophysics Data System (ADS)

Weissmann, G. S.; Hartley, A. J.; Scuderi, L. A.; Nichols, G. J.; Owen, A.; Wright, S.; Felicia, A. L.; Holland, F.; Anaya, F. M. L.

2015-12-01

Since tectonic subsidence in sedimentary basins provides the potential for long-term facies preservation into the sedimentary record, analysis of geomorphic elements in modern continental sedimentary basins is required to understand facies relationships in sedimentary rocks. We use a database of over 700 modern sedimentary basins to characterize the fluvial geomorphology of sedimentary basins. Geomorphic elements were delineated in 10 representative sedimentary basins, focusing primarily on fluvial environments. Elements identified include distributive fluvial systems (DFS), tributive fluvial systems that occur between large DFS or in an axial position in the basin, lacustrine/playa, and eolian environments. The DFS elements include large DFS (> 30 km in length), small DFS (< 30 km in length), coalesced DFS in bajada or piedmont plains, and incised DFS. Our results indicate that over 88% of fluvial deposits in the evaluated sedimentary basins are present as DFS, with tributary systems covering a small portion (1-12%) of the basin. These geomorphic elements are commonly arranged hierarchically, with the largest transverse rivers forming large DFS and smaller transverse streams depositing smaller DFS in the areas between the larger DFS. These smaller streams commonly converge between the large DFS, forming a tributary system. Ultimately, most transverse rivers become tributary to the axial system in the sedimentary basin, with the axial system being confined between transverse DFS entering the basin from opposite sides of the basin, or a transverse DFS and the edge of the sedimentary basin. If axial systems are not confined by transverse DFS, they will form a DFS. Many of the world's largest rivers are located in the axial position of some sedimentary basins. Assuming uniformitarianism, sedimentary basins from the past most likely had a similar configuration of geomorphic elements. Facies distributions in tributary positions and those on DFS appear to display specific morphologic patterns. Tributary rivers tend to increase in size in the downstream direction. Because axial tributary rivers are present in confined settings in the sedimentary basin, they migrate back and forth within a relatively narrow belt (relative to the overall size of the sedimentary basin). Thus, axial tributary rivers tend to display amalgamated channel belt form with minimal preservation potential of floodplain deposits. Chute and neck cutoff avulsions are also common on meandering rivers in these settings. Where rivers on DFS exit their confining valley on the basin margin, sediment transport capacity is reduced and sediment deposition occurs resulting in development of a 'valley exit' nodal avulsion point that defines the DFS apex. Rivers may incise downstream of the basin margin valley because of changes in sediment supply and discharge through climatic variability or tectonic processes. We demonstrate that rivers on DFS commonly decrease in width down-DFS caused by infiltration, bifurcation, and evaporation. In proximal areas, channel sands are amalgamated through repeated avulsion, reoccupation of previous channel belts, and limited accumulation space. When rivers flood on the medial to distal portions of a DFS, the floodwaters spread across a large area on the DFS surface and typically do not re-enter the main channel. In these distal areas, rivers on DFS commonly avulse, leaving a discrete sand body and providing high preservation potential for floodplain deposits. Additional work is needed to evaluate the geomorphic character of modern sedimentary basins in order to construct improved facies models for the continental sedimentary rock record. Specifically, models for avulsion, bifurcation, infiltration, and geomorphic form on DFS are required to better define and subsequently predict facies geometries. Studies of fluvial systems in sedimentary basins are also important for evaluating flood patterns and groundwater distributions for populations in these regions.

Rapid fluvial incision of a late Holocene lava flow: Insights from LiDAR, alluvial stratigraphy, and numerical modeling

USGS Publications Warehouse

Sweeney, Kristin; Roering, Joshua J.

2016-01-01

Volcanic eruptions fundamentally alter landscapes, paving over channels, decimating biota, and emplacing fresh, unweathered material. The fluvial incision of blocky lava flows is a geomorphic puzzle. First, high surface permeability and lack of sediment should preclude geomorphically effective surface runoff and dissection. Furthermore, past work has demonstrated the importance of extreme floods in driving incision via column toppling and plucking in columnar basalt, but it is unclear how incision occurs in systems where surface blocks are readily mobile. We examine rapid fluvial incision of the Collier lava flow, an andesitic Holocene lava flow in the High Cascades of Oregon. Since lava flow emplacement ∼1600 yr ago, White Branch Creek has incised bedrock gorges up to 8 m deep into the coherent core of the lava flow and deposited >0.2 km3 of sediment on the lava flow surface. Field observation points to a bimodal discharge regime in the channel, with evidence for both annual snowmelt runoff and outburst floods from Collier glacier, as well as historical evidence of vigorous glacial meltwater. To determine the range of discharge events capable of incision in White Branch Creek, we used a mechanistic model of fluvial abrasion. We show that the observed incision implies that moderate flows are capable of both initiating channel formation and sustaining incision. Our results have implications for the evolution of volcanic systems worldwide, where glaciation and/or mass wasting may accelerate fluvial processes by providing large amounts of sediment to otherwise porous, sediment-starved landscapes.

Human alterations, dynamic equilibrium, and riparian ecosystem responses along selected rivers in Tuscany, Italy (Invited)

NASA Astrophysics Data System (ADS)

Hupp, C. R.; Rinaldi, M.

2010-12-01

Many, if not most, streams have been mildly to severely affected by human disturbance, which complicates efforts to understand riparian ecosystems. Mediterranean regions have a long history of human influences including: dams, stream channelization, mining of sediment, and levee /canal construction. Typically these alterations reduce the ecosystem services that functioning floodplains provide and may negatively impact the natural ecology of floodplains through reductions in suitable habitats, biodiversity, and nutrient cycling. Additionally, human alterations typically shift affected streams away from a state of natural dynamic equilibrium, where net sediment deposition is approximately in balance with net erosion. Lack of equilibrium typically affects the degree to which floodplain ecosystems are connected to streamflow regime. Low connectivity, usually from human- or climate-induced incision, may result in reduced flow on floodplains and lowered water tables. High connectivity may result in severe sediment deposition. Connectivity has a direct impact on vegetation communities. Riparian vegetation distribution patterns and diversity relative to various fluvial geomorphic channel patterns, landforms, and processes are described and interpreted for selected rivers of Tuscany, Central Italy; with emphasis on channel evolution following human impacts. Multivariate analysis reveals distinct quantitative vegetation patterns related to six fluvial geomorphic surfaces. Analysis of vegetation data also shows distinct associations of plants with adjustment processes related to the stage of channel evolution. Plant distribution patterns coincide with disturbance/landform/soil moisture gradients. Species richness increases from channel bed to terrace and on heterogeneous riparian areas, while species richness decreases from moderate to intense incision and from low to intense narrowing. As a feedback mechanism, woody vegetation in particular may facilitate geomorphic recovery of floodplains by affecting sedimentation dynamics. Identification and understanding of critical fluvial parameters related to floodplain connectivity (e.g. stream gradient, grain-size, and hydrography) and spatial and temporal sediment deposition/erosion process trajectories should facilitate management efforts to retain and/or regain important ecosystem services.

Vegetation as a tool in the interpretation of fluvial geomorphic processes and landforms

USGS Publications Warehouse

Hupp, Cliff R.; Dufour, S; Bornette, G

2016-01-01

This chapter exemplifies that vegetation can be used as a tool for geomorphic interpretation in several major ways. It presents a general overview: through dendrogeomorphic analysis (tree rings) to estimate the timing of important geomorphic events including floods and mass wasting and to estimate rates of erosion and sedimentation; through the documentation and interpretation of species distributional patterns that are established in response to prevailing hydrogeomorphic conditions; and through the role that it plays, depending on size, shape and growth form, in flow rates and subsequent erosion and deposition processes. Floods, from prolonged inundation characteristic of relatively large, low-gradient basins to high-gradient and short-period destructive events, are the most important extrinsic factor in bottomland systems. Vegetation organization, composition and plant community dynamics on river floodplains are controlled by disturbance type and scale, and biological characteristics of plants linked to resistance to disturbance, resilience and competitive ability.

Excursions in fluvial (dis)continuity

NASA Astrophysics Data System (ADS)

Grant, Gordon E.; O'Connor, Jim; Safran, Elizabeth

2017-01-01

Lurking below the twin concepts of connectivity and disconnectivity are their first, and in some ways, richer cousins: continuity and discontinuity. In this paper we explore how continuity and discontinuity represent fundamental and complementary perspectives in fluvial geomorphology, and how these perspectives inform and underlie our conceptions of connectivity in landscapes and rivers. We examine the historical roots of continuum and discontinuum thinking, and how much of our understanding of geomorphology rests on contrasting views of continuity and discontinuity. By continuum thinking we refer to a conception of geomorphic processes as well as geomorphic features that are expressed along continuous gradients without abrupt changes, transitions, or thresholds. Balance of forces, graded streams, and hydraulic geometry are all examples of this perspective. The continuum view has played a prominent role in diverse disciplinary fields, including ecology, paleontology, and evolutionary biology, in large part because it allows us to treat complex phenomena as orderly progressions and invoke or assume equilibrium processes that introduce order and prediction into our sciences. In contrast the discontinuous view is a distinct though complementary conceptual framework that incorporates non-uniform, non-progressive, and non-equilibrium thinking into understanding geomorphic processes and landscapes. We distinguish and discuss examples of three different ways in which discontinuous thinking can be expressed: 1) discontinuous spatial arrangements or singular events; 2) specific process domains generally associated with thresholds, either intrinsic or extrinsic; and 3) physical dynamics or changes in state, again often threshold-linked. In moving beyond the continuous perspective, a fertile set of ideas comes into focus: thresholds, non-equilibrium states, heterogeneity, catastrophe. The range of phenomena that is thereby opened up to scientific exploration similarly expands: punctuated episodes of cutting and filling, discretization of landscapes into hierarchies of structure and control, the work of extreme events. Orderly and progressive evolution towards a steady or ideal state is replaced by chaotic episodes of disturbance and recovery. Recent developments in the field of geomorphology suggest that we may be on the cusp of a new paradigm that recognizes that both continuous and discontinuous processes and mechanisms play a role in fluvial processes and landscape evolution with neither holding sway over the other and both needed to see rivers as they are.

Excursions in fluvial (dis)continuity

USGS Publications Warehouse

Grant, Gordon E.; O'Connor, James E.; Safran, Elizabeth

2017-01-01

Lurking below the twin concepts of connectivity and disconnectivity are their first, and in some ways, richer cousins: continuity and discontinuity. In this paper we explore how continuity and discontinuity represent fundamental and complementary perspectives in fluvial geomorphology, and how these perspectives inform and underlie our conceptions of connectivity in landscapes and rivers. We examine the historical roots of continuum and discontinuum thinking, and how much of our understanding of geomorphology rests on contrasting views of continuity and discontinuity. By continuum thinking we refer to a conception of geomorphic processes as well as geomorphic features that are expressed along continuous gradients without abrupt changes, transitions, or thresholds. Balance of forces, graded streams, and hydraulic geometry are all examples of this perspective. The continuum view has played a prominent role in diverse disciplinary fields, including ecology, paleontology, and evolutionary biology, in large part because it allows us to treat complex phenomena as orderly progressions and invoke or assume equilibrium processes that introduce order and prediction into our sciences.In contrast the discontinuous view is a distinct though complementary conceptual framework that incorporates non-uniform, non-progressive, and non-equilibrium thinking into understanding geomorphic processes and landscapes. We distinguish and discuss examples of three different ways in which discontinuous thinking can be expressed: 1) discontinuous spatial arrangements or singular events; 2) specific process domains generally associated with thresholds, either intrinsic or extrinsic; and 3) physical dynamics or changes in state, again often threshold-linked. In moving beyond the continuous perspective, a fertile set of ideas comes into focus: thresholds, non-equilibrium states, heterogeneity, catastrophe. The range of phenomena that is thereby opened up to scientific exploration similarly expands: punctuated episodes of cutting and filling, discretization of landscapes into hierarchies of structure and control, the work of extreme events. Orderly and progressive evolution towards a steady or ideal state is replaced by chaotic episodes of disturbance and recovery. Recent developments in the field of geomorphology suggest that we may be on the cusp of a new paradigm that recognizes that both continuous and discontinuous processes and mechanisms play a role in fluvial processes and landscape evolution with neither holding sway over the other and both needed to see rivers as they are.

The long-term legacy of geomorphic and riparian vegetation feedbacks on the dammed Bill Williams River, Arizona, USA

USGS Publications Warehouse

Kui, Li; Stella, John C.; Shafroth, Patrick B.; House, P. Kyle; Wilcox, Andrew C.

2017-01-01

On alluvial rivers, fluvial landforms and riparian vegetation communities codevelop as a result of feedbacks between plants and abiotic processes. The influence of vegetation on river channel and floodplain geomorphology can be particularly strong on dammed rivers with altered hydrology and reduced flood disturbance. We used a 56-year series of aerial photos on the dammed Bill Williams River (Arizona, USA) to investigate how (a) different woody riparian vegetation types influence river channel planform and (b) how different fluvial landforms drive the composition of riparian plant communities over time. We mapped vegetation types and geomorphic surfaces and quantified how relations between fluvial and biotic processes covaried over time using linear mixed models. In the decades after the dam was built, woody plant cover within the river's bottomland nearly doubled, narrowing the active channel by 60% and transforming its planform from wide and braided to a single thread and more sinuous channel. Compared with native cottonwood–willow vegetation, nonnative tamarisk locally induced a twofold greater reduction in channel braiding. Vegetation expanded at different rates depending on the type of landform, with tamarisk cover on former high-flow channels increasing 17% faster than cottonwood–willow. Former low-flow channels with frequent inundation supported a greater increase in cottonwood–willow relative to tamarisk. These findings give insight into how feedbacks between abiotic and biotic processes in river channels accelerate and fortify changes triggered by dam construction, creating river systems increasingly distinct from predam ecological communities and landforms, and progressively more resistant to restoration of predam forms and processes.

Preserving geomorphic data records of flood disturbances

USGS Publications Warehouse

Moody, John A.; Martin, Deborah; Meade, Robert H.

2015-01-01

No central database or repository is currently available in the USA to preserve long-term, spatially extensive records of fluvial geomorphic data or to provide future accessibility. Yet, because of their length and continuity these data are valuable for future research. Therefore, we built a public accessible website to preserve data records of two examples of long-term monitoring (40 and 18 years) of the fluvial geomorphic response to natural disturbances. One disturbance was ∼50-year flood on Powder River in Montana in 1978, and the second disturbance was a catastrophic flood on Spring Creek following a ∼100-year rainstorm after a wildfire in Colorado in 1996.Two critical issues arise relative to preserving fluvial geomorphic data. The first is preserving the data themselves, but the second, and just as important, is preserving information about the location of the field research sites where the data were collected so the sites can be re-located and re-surveyed in the future. The latter allows long-term datasets to be extended into the future and to provide critical background data for interpreting future landscape changes. Data were preserved on a website to allow world-wide accessibility and to upload new data to the website as they become available. We describe the architecture of the website, lessons learned in developing the website, future improvements, and recommendations on how also to preserve information about the location of field research sites.

From Hype to an Operational Tool: Efforts to Establish a Long-Term Monitoring Protocol of Alluvial Sandbars using `Structure-from-Motion' Photogrammetry

NASA Astrophysics Data System (ADS)

Rossi, R.; Buscombe, D.; Grams, P. E.; Schmidt, J. C.; Wheaton, J. M.

2016-12-01

Despite recent advances in the use of `Structure-from-Motion' (SfM) photogrammetry to accurately map landforms, its utility for reliably detecting and monitoring geomorphic change from repeat surveys remains underexplored in fluvial environments. It is unclear how the combination of various image acquisition platforms and techniques, survey scales, vegetation cover, and terrain complexities translate into accuracy and precision metrics for SfM-based construction of digital elevation models (DEMs) of fluvial landforms. Although unmanned aerial vehicles offer the potential to rapidly image large areas, they can be relatively costly, require skilled operators, are vulnerable in adverse weather conditions, and often rely on GPS-positioning to improve their stability. This research details image acquisition techniques for an underrepresented SfM platform: the pole-mounted camera. We highlight image acquisition and post-processing limitations of the SfM method for alluvial sandbars (10s to 100s m2) located in Marble and Grand Canyons in a remote, fluvial landscape with limited field access, strong light gradients, highly variable surface texture and limited ground control. We recommend a pole-based SfM protocol and evaluate it by comparing SfM-derived DEMs against concurrent, total station surveys. Error models of the sandbar surfaces are developed for a variety of surface characteristics (e.g., bare sand, steep slopes, and areas of shadow). The Geomorphic Change Detection (GCD) Software is used to compare SfM DEMs from before and after the 2014 high flow release from Glen Canyon Dam. Complementing existing total-station based sandbar surveys with potentially more efficient and cost-effective SfM methods will contribute to the understanding of morphodynamic responses of sandbars to high flow releases from Glen Canyon Dam. In addition, the development and implementation of a SfM-based operational method for monitoring geomorphic change will provide a methodological foundation for extending the approach to other fluvial environments.

From Hype to an Operational Tool: Efforts to Establish a Long-Term Monitoring Protocol of Alluvial Sandbars using 'Structure-from-Motion' Photogrammetry

NASA Astrophysics Data System (ADS)

Rossi, R.; Buscombe, D.; Grams, P. E.; Wheaton, J. M.

2015-12-01

Despite recent advances in the use of 'Structure-from-Motion' (SfM) photogrammetry to accurately map landforms, its utility for reliably detecting and monitoring geomorphic change from repeat surveys remains underexplored in fluvial environments. It is unclear how the combination of various image acquisition platforms and techniques, survey scales, vegetation cover, and terrain complexities translate into accuracy and precision metrics for SfM-based construction of digital elevation models (DEMs) of fluvial landforms. Although unmanned aerial vehicles offer the potential to rapidly image large areas, they can be relatively costly, require skilled operators, are vulnerable in adverse weather conditions, and often rely on GPS-positioning to improve their stability. This research details image acquisition techniques for an underrepresented SfM platform: the pole-mounted camera. We highlight image acquisition and post-processing limitations of the SfM method for alluvial sandbars (10s to 100s m2) located in Marble and Grand Canyons in a remote, fluvial landscape with limited field access, strong light gradients, highly variable surface texture and limited ground control. We recommend a pole-based SfM protocol and evaluate it by comparing SfM-derived DEMs against concurrent, total station surveys and TLS derived DEMs. Error models of the sandbar surfaces are developed for a variety of surface characteristics (e.g., bare sand, steep slopes, and areas of shadow). The Geomorphic Change Detection (GCD) Software is used to compare SfM DEMs from before and after the 2014 high flow release from Glen Canyon Dam. Complementing existing total-station based sandbar surveys with potentially more efficient and cost-effective SfM methods will contribute to the understanding of morphodynamic responses of sandbars to high flow releases from Glen Canyon Dam. In addition, the development and implementation of a SfM-based operational protocol for monitoring geomorphic change will provide a methodological foundation for extending the approach to other fluvial environments.

Geomorphology and soil survey

Treesearch

Laura A. Murray; Bob Eppinette; John H. Thorp

2000-01-01

The Coosawhatchie River, through erosion and downcutting, carved a fluvial valley through the Wicomico and Pamlico marine terraces during the late Pleistocene-Holocene period. The floodplain is relatively small and immature compared to the major river systems of the South Carolina Lower Coastal Plain. Consequently, the classic geomorphic features of a larger fluvial...

Near-census Delineation of Laterally Organized Geomorphic Zones and Associated Sub-width Fluvial Landforms

NASA Astrophysics Data System (ADS)

Pasternack, G. B.; Hopkins, C.

2017-12-01

A river channel and its associated riparian corridor exhibit a pattern of nested, geomorphically imprinted, lateral inundation zones (IZs). Each zone plays a key role in fluvial geomorphic processes and ecological functions. Within each zone, distinct landforms (aka geomorphic or morphological units, MUs) reside at the 0.1-10 channel width scale. These features are basic units linking river corridor morphology with local ecosystem services. Objective, automated delineation of nested inundation zones and morphological units remains a significant scientific challenge. This study describes and demonstrates new, objective methods for solving this problem, using the 35-km alluvial lower Yuba River as a testbed. A detrended, high-resolution digital elevation model constructed from near-census topographic and bathymetric data was produced and used in a hypsograph analysis, a commonly used method in oceanographic studies capable of identifying slope breaks at IZ transitions. Geomorphic interpretation mindful of the river's setting was required to properly describe each IZ identified by the hypsograph analysis. Then, a 2D hydrodynamic model was used to determine what flow yields the wetted area that most closely matches each IZ domain. The model also provided meter-scale rasters of depth and velocity useful for MU mapping. Even though MUs are discharge-independent landforms, they can be revealed by analyzing their overlying hydraulics at low flows. Baseflow depth and velocity rasters are used along with a hydraulic landform classification system to quantitatively delineate in-channel bed MU types. In-channel bar and off-channel flood and valley MUs are delineated using a combination of hydraulic and geomorphic indicators, such as depth and velocity rasters for different discharges, topographic contours, NAIP imagery, and a raster of vegetation. The ability to objectively delineate inundation zones and morphological units in tandem allows for better informed river management and restoration strategies as well as scientific studies about abiotic-biotic linkages.

A fast, parallel algorithm to solve the basic fluvial erosion/transport equations

NASA Astrophysics Data System (ADS)

Braun, J.

2012-04-01

Quantitative models of landform evolution are commonly based on the solution of a set of equations representing the processes of fluvial erosion, transport and deposition, which leads to predict the geometry of a river channel network and its evolution through time. The river network is often regarded as the backbone of any surface processes model (SPM) that might include other physical processes acting at a range of spatial and temporal scales along hill slopes. The basic laws of fluvial erosion requires the computation of local (slope) and non-local (drainage area) quantities at every point of a given landscape, a computationally expensive operation which limits the resolution of most SPMs. I present here an algorithm to compute the various components required in the parameterization of fluvial erosion (and transport) and thus solve the basic fluvial geomorphic equation, that is very efficient because it is O(n) (the number of required arithmetic operations is linearly proportional to the number of nodes defining the landscape), and is fully parallelizable (the computation cost decreases in a direct inverse proportion to the number of processors used to solve the problem). The algorithm is ideally suited for use on latest multi-core processors. Using this new technique, geomorphic problems can be solved at an unprecedented resolution (typically of the order of 10,000 X 10,000 nodes) while keeping the computational cost reasonable (order 1 sec per time step). Furthermore, I will show that the algorithm is applicable to any regular or irregular representation of the landform, and is such that the temporal evolution of the landform can be discretized by a fully implicit time-marching algorithm, making it unconditionally stable. I will demonstrate that such an efficient algorithm is ideally suited to produce a fully predictive SPM that links observationally based parameterizations of small-scale processes to the evolution of large-scale features of the landscapes on geological time scales. It can also be used to model surface processes at the continental or planetary scale and be linked to lithospheric or mantle flow models to predict the potential interactions between tectonics driving surface uplift in orogenic areas, mantle flow producing dynamic topography on continental scales and surface processes.

Tipping Points in Texas Rivers

NASA Astrophysics Data System (ADS)

Phillips, Jonathan

2016-04-01

Anticipating geomorphic tipping points requires that we learn from the past. Major geomorphic changes in coastal plain rivers of Texas resulting in river metamorphosis or regime shifts were identified, and the major driving factors determined. Nine fluvial tipping points were identified from contemporary observations, historical records, and Quaternary reconstructions. Two of the tipping points (between general aggrading and degrading valley states) are associated with reversals in a fundamental system control (sea-level). One (stable or aggrading vs. degrading channels) is associated with an abrupt change in sediment supply due to dam construction, and two others (changes from meandering to anastomosing channel patterns, and different anastomosis styles) are similarly related to changes in sediment supply and/or transport capacity, but with additional elements of historical contingency. Three tipping points are related to avulsions. One, from a regime dominated to reoccupation of former channels to one dominated by progradation into flood basins, is driven by progressive long term filling of incised valleys. Another, nodal avulsions, are driven by disturbances associated with tectonics or listric faults. The third, avulsions and related valley metamorphosis in unfilled incised valleys, is due to fundamental dynamical instabilities within the fluvial system. This synthesis and analysis suggests that geomorphic tipping points are sometimes associated with general extrinsic or intrinsic (to the fluvial system) environmental change, independent of any disturbances or instabilities. Others are associated with natural (e.g., tectonic) or human (dams) disturbances, and still others with intrinsic geomorphic instabilities. This suggests that future tipping points will be equally diverse with respect to their drivers.

Landslide-induced river channel avulsions in mountain catchments of southwest New Zealand

NASA Astrophysics Data System (ADS)

Korup, Oliver

2004-11-01

Pulsed or chronic supply of landslide debris to valley floors has historically caused substantial aggradation and channel instability in several alpine catchments of SW New Zealand. In this regional investigation of landslide impacts on river morphology, three types of landslide-induced channel avulsion are discerned: (i) upstream/backwater avulsions, (ii) contact avulsions, and (iii) downstream/loading avulsions. The basis for this qualitative geomorphic process-response framework is the principal direction of fluvial response with respect to its position relative to the causative landslide emplacement site. Downstream avulsions have the highest damage potential to land use and infrastructure on unconfined mountain-fringe alluvial fans. In the wake of such events, catastrophic aggradation may obliterate up to several km 2 of mature floodplain forests by burial under several metres within a few decades. Estimates of mean aggradation rates are high (<220 mm year -1) and exceed long-term (10 3 year) trends of fluvial degradation by an order of magnitude. Future potential avulsion routeways may be detected by geomorphic mapping of abandoned channels, which are preferentially reactivated in the wake of landslide-induced sediment waves.

Preparing for uncertainty: toward managing fluvial geomorphic assessment of Massachusetts rivers

NASA Astrophysics Data System (ADS)

Hatch, C. E.; Mabee, S. B.; Slovin, N. B.; Vogel, E.

2014-12-01

Climate scientists predict (and have already observed) that in the Northeastern U.S., individual storms may be more intense, and that there will be more precipitation on an annual basis. In steep post-glacial terrain, erosion caused by floodwaters is the largest destructive force during high-intensity storm events, and the force most likely to drive major morphological changes to riverbanks and channels. What remains uncertain is which watersheds or river reaches may be subjected to increased damage from more intense storms. This presents a challenge for scientific outreach and management. Many New England states have developed systems for delineating the potentially geomorphically active zones adjacent to rivers, and Vermont has an excellent assessment and land use management system informed by process-based fluvial geomorphologic science. To date, however, Massachusetts has neither. In this project we survey existing protocols for accurately predicting locations of fluvial erosion hazard, including using LiDAR and DEM models to extract basic morphologic metrics. Particularly in states or landscapes with high river density, and during a time of tight fiscal constraints, managers need automated methods that require a minimum of expert input. We test these methods in the Deerfield river watershed in Massachusetts and Vermont, and integrate our knowledge with that of the basin's agricultural and floodplain stakeholders. The results will inform development of a comprehensive river assessment and land use management system for the state of Massachusetts.

Sediment connectivity at source-bordering aeolian dunefields along the Colorado River in the Grand Canyon, USA

NASA Astrophysics Data System (ADS)

Sankey, Joel; Kasprak, Alan; Caster, Joshua; East, Amy; Fairley, Helen

2017-04-01

Aeolian dunefields that are primarily built and maintained with river-derived sediment are found in many river valleys throughout the world and are impacted by changes in climate, land use, and river regulation. Quantifying the dynamic response of these aeolian dunefields to alterations in river flow is especially difficult given the highly correlated nature of the interacting geomorphic and sediment transport processes that drive their formation and maintenance. We characterize the effects of controlled river floods on changes in sediment connectivity at source-bordering aeolian dunefields in the Grand Canyon, USA. Controlled floods from the Glen Canyon Dam are used to build sandbars along the Colorado River in Grand Canyon which provide the main sediment source for aeolian dunefields. Aeolian dunefields are a primary resource of concern for land managers in the Grand Canyon because they often contain buried archaeological features. To characterize dunefield response to controlled floods, we use a novel, automated approach for the mechanistic segregation of geomorphic change to discern the geomorphic processes responsible for driving topographic change in very high resolution digital elevation models-of-difference (DODs) that span multiple, consecutive controlled river floods at source-bordering dunefields. We subsequently compare the results of mechanistic segregation with modelled estimates of aeolian dunefield evolution in order to understand how dunefields respond to contemporary, anthropogenically-driven variability in sediment supply and connectivity. These methods provide a rapid technique for sediment budgeting and enable the inference of spatial and temporal patterns in sediment flux between the fluvial and aeolian domains. We anticipate that this approach will be adaptable to other river valleys where the interactions of aeolian, fluvial, and hillslope processes drive sediment connectivity for the maintenance of source-bordering aeolian dunefields.

Controls of sediment transfers, sedimentary budgets and relief development in cold environments: Results from four catchment systems in Iceland, Swedish Lapland and Finnish Lapland

NASA Astrophysics Data System (ADS)

Beylich, A. A.

2012-04-01

By the combined, longer-term and quantitative recording of relevant denudative slope processes and stream work in four selected catchment systems in sub-arctic oceanic Eastern Iceland (Hrafndalur and Austdalur), arctic-oceanic Swedish Lapland (Latnjavagge) and sub-arctic oceanic Finnish Lapland (Kidisjoki), information on the absolute and relative importance of the different denudative processes is collected. Direct comparison of the four catchment geo-systems (the catchment sizes range from 7 km2 to 23 km2) allows conclusions on major controls of sediment transfers, sedimentary budgets and relief development in theses cold climate environments. To allow direct comparison of the different processes, all mass transfers are calculated as tonnes multiplied by meter per year, i.e. as the product of the annually transferred mass and the corresponding transport distance. Ranking the different processes according to their annual mass transfers shows that stream work dominates over slope denudation. For Hrafndalur (Eastern Iceland) the following order of denudative processes is found after nine years of process studies (2001 - 2010): (1) Fluvial suspended sediment plus bedload transport, (2) Fluvial solute transport, (3) Rock falls plus boulder falls, (4) Chemical slope denudation, (5) Mechanical fluvial slope denudation (slope wash), (6) Creep processes, (7) Avalanches, (8) Debris flows, (9) Translation slides, (10) Deflation. Compared to that, in Austdalur the following ranking is given after fourten years of process studies (1996 - 2010): (1) Fluvial suspended sediment plus bedload transport, (2) Fluvial solute transport, (3) Mechanical fluvial slope denudation (slope wash), (4) Chemical slope denudation, (5) Avalanches, (6) Rock falls plus boulder falls, (7) Creep processes, (8) Debris flows, (9) Deflation, (10) Translation slides. In the Latnjavagge catchment (Swedish Lapland) the ranking is (eleven-years period of studies, 1999 - 2010): (1) Fluvial solute transport, (2) Fluvial suspended sediment plus bedload transport, (3) Rock falls plus boulder falls, (4) Chemical slope denudation, (5) Mechanical fluvial slope denudation (slope wash), (6) Avalanches, (7) Creep processes and solifluction, (8) Slush flows, (9) Debris flows, (10) Translation slides, (11) Deflation. In Kidisjoki (Finnish Lapland) the order of processes, as determined after a nine-years period (2001 - 2010) of geomorphic process studies, is: (1) Fluvial solute transport, (2) Chemical slope denudation, (3) Fluvial suspended sediment plus bedload transport, (4) Mechanical fluvial slope denudation, (5) Creep processes, (6) Avalanches and slush flows, (7) Debris flows and slides, (8) Rock and boulder falls, (9) Deflation. As a result, in all four selected cold climate study areas the intensity of contemporary denudative processes and mass transfers is altogether rather low, which is in opposition to the earlier postulated oppinion of a generally high intensity of geomorphic processes in cold climate environments. A direct comparison of the annual mass transfers summarises that there are differences between process intensities and the relative importance of different denudative processes within the four study areas. The major controls of these detected differences are: (i) Climate: The higher annual precipitation along with the larger number of extreme rainfall events and the higher frequency of snowmelt and rainfall generated peak runoff events in Eastern Iceland as compared to Swedish Lapland and Finnish Lapland lead to higher mass transfers, (ii) Lithology: The low resistance of rhyolites in Hrafndalur causes especially high weathering rates and connected mass transfers in this catchment. Due to the lower resistance of the rhyolites as compared to the basalts found in Austdalur Postglacial modification of the glacially formed relief is clearly further advanced in Hrafndalur as compared to Austdalur, (iii) Relief: The greater steepness of the Icelandic catchments leads to higher mass transfers here as compared to Latnjavagge and Kidisjoki, (iv) Vegetation cover: The significant disturbance of the vegetation cover by human impacts in Easter Iceland causes higher mass transfers (slope wash) whereas restricted sediment availability is a main reason for lower mass transfers in Swedish Lapland and Finnish Lapland. The applied catchment-based approach seems to be effective for analysing sediment budgets and trends of Postglacial relief development in selected study areas with given environmental settings. Direct comparison of investigated catchments will improve possibilities to model relief development as well as possible effects of projected climate change in cold climate environments.

A drainage basin scale model for earthflow-prone landscapes over geomorphic timescales

NASA Astrophysics Data System (ADS)

Booth, A. M.; Roering, J. J.

2009-12-01

Landscape evolution models can be informative tools for understanding how sediment transport processes, regulated by tectonic and climatic forcing, interact to control fundamental landscape characteristics such as relief, channel network organization, and hillslope form. Many studies have proposed simple mathematical geomorphic transport laws for modeling hillslope and fluvial processes, and these models are capable of generating synthetic landscapes similar to many of those observed in nature. However, deep-seated mass movements dominate the topographic development of many tectonically active landscapes, yet few compelling transport laws exist for accurately describing these processes at the drainage basin scale. Specifically, several detailed field and theoretical studies describe the mechanics of deep-seated earthflows, such as those found throughout the northern California coast ranges, but these studies are often restricted to a single earthflow site. Here, we generalize earthflow behavior to larger spatial and geomorphically significant temporal scales using a mathematical model to determine how interactions between earthflow, weathering, hillslope, and fluvial processes control sediment flux and topographic form. The model couples the evolution of the land surface with the evolution of a weathered zone driven by fluctuations in the groundwater table. The lower boundary of this weathered zone sets the potential failure plane for earthflows, which occur once the shear stress on this plane exceeds a threshold value. Earthflows deform downslope with a non-Newtonian viscous rheology while gullying, modeled with a stream power equation, and soil creep, modeled with a diffusion equation, continuously act on the land surface. To compare the intensities of these different processes, we define a characteristic timescale for each modeled process, and demonstrate how the ratios of these timescales control the steady-state topographic characteristics of the simulated landscapes. As changes in earthflow rheological properties or thickening of the weathered zone increase the intensity of earthflow processes, relief decreases, hillslopes become more planar, and fluvial incision is inhibited at low drainage areas. The model also predicts that earthflows make their most significant contribution to long term lowering of the land surface at mid- and upper-slope locations. Fluvial processes dominate at high drainage area hillslope toes, and soil creep dominates at highly convex ridgelines. We find the predictions of our model in agreement with the following general observations of earthflow prone terrain, drawn from analysis of a 1m resolution LiDAR digital elevation model of terrain adjacent to the main stem of the Eel River, northern California: (1) hillslope profiles tend to be slightly convex at the foot, broadly concave through the mid-slope, and highly convex at the ridgeline, (2) gully incision of earthflow transport zones and toes may be important in delivering sediment from hillslopes to high order streams, and (3) as with shallow landsliding, magnitude-frequency distributions of active earthflows tend to be heavy tailed.

Using HEC-RAS to Enhance Interpretive Capabilities of Geomorphic Assessments

NASA Astrophysics Data System (ADS)

Keefer, L. L.

2005-12-01

The purpose of a geomorphic assessment is to characterize and evaluate a fluvial system for determining the past watershed and channel conditions, current geomorphic character and potential future channel adjustments. The geomorphic assessment approach utilized by the Illinois State Water Survey assesses channel response to disturbance at multiple temporal and spatial scales to help identify the underlying factors and events which led to the existing channel morphology. This is accomplished through two phases of investigation that involve a historical and physical analysis of the watershed, disturbance history, and field work at increasing levels of detail. To infer future channel adjustments, the geomorphic assessment protocol combines two methods of analyses that are dependent on the quantity and detail of the available data. The first method is the compilation of multiple lines of evidence using qualitative information related to the dominant fluvial environment, channel gradient, stream power thresholds, and channel evolution models. The second method is the use of hydraulic models which provide additional interpretative skills to evaluate potential channel adjustments. The structured data collection framework of the geomorphic assessment approach is used for the development of a HEC-RAS model. The model results are then used as another tool to determine the influence of bridges and control structures on channel stability, stream power profiles to identify potential channel bed degradation zones, and provide data for physically-based bank stability models. This poster will demonstrate the advantages of using a hydraulic model, such as HEC-RAS, to expand the interpretive capabilities of geomorphic assessments. The results from applying this approach will be demonstrated for the Big Creek watershed of the Cache River Basin in southern Illinois.

Fluvial geomorphology and aquatic-to-terrestrial Hg export are weakly coupled in small urban streams of Columbus, Ohio

NASA Astrophysics Data System (ADS)

Sullivan, S. Mažeika P.; Boaz, Lindsey E.; Hossler, Katie

2016-04-01

Although mercury (Hg) contamination is common in stream ecosystems, mechanisms governing bioavailability and bioaccumulation in fluvial systems remain poorly resolved as compared to lentic systems. In particular, streams in urbanized catchments are subject to fluvial geomorphic alterations that may contribute to Hg distribution, bioaccumulation, and export across the aquatic-to-terrestrial boundary. In 12 streams of urban Columbus, Ohio, we investigated the influence of fluvial geomorphic characteristics related to channel geometry, streamflow, and sediment size and distribution on (1) Hg concentrations in sediment and body burdens in benthic larval and adult emergent aquatic insects and (2) aquatic-to-terrestrial contaminant transfer to common riparian spiders of the families Pisauridae and Tetragnathidae via changes in aquatic insect Hg body burdens as well as in aquatic insect density and community composition. Hydrogeomorphic characteristics were weakly related to Hg body burdens in emergent insects (channel geometry) and tetragnathid spiders (streamflow), but not to Hg concentrations in sediment or benthic insects. Streamflow characteristics were also related to emergent insect density, while wider channels were associated with benthic insect community shifts toward smaller-bodied and more tolerant taxa (e.g., Chironomidae). Thus, our results provide initial evidence that fluvial geomorphology may influence aquatic-to-terrestrial contaminant Hg transfer through the collective effects on emergent insect body burdens as well as on aquatic insect community composition and abundance.

Hydrodynamic and sedimentological controls governing formation of fluvial levees

NASA Astrophysics Data System (ADS)

Johnston, G. H.; Edmonds, D. A.; David, S. R.; Czuba, J. A.

2017-12-01

Fluvial levees are familiar features found on the margins of river channels, yet we know little about what controls their presence, height, and shape. These attributes of levees are important because they control sediment transfer from channel to floodplain and flooding patterns along a river system. Despite the familiarity and importance of levees, there is a surprising lack of basic geomorphic data on fluvial levees. Because of this we seek to understand: 1) where along rivers do levees tend to occur?; 2) what geomorphic and hydrodynamic variables control cross-sectional shape of levees? We address these questions by extracting levee shape from LiDAR data and by collecting hydrodynamic and sedimentological data from reaches of the Tippecanoe River, the White River, and the Muscatatuck River, Indiana, USA. Fluvial levees are extracted from a 1.5-m resolution LiDAR bare surface model and compared to hydrological, sedimentological, and geomorphological data from USGS stream gages. We digitized banklines and extracted levee cross-sections to calculate levee slope, taper, height, e-folding length, and e-folding width. To answer the research questions, we performed a multivariable regression between the independent variables—channel geometry, sediment grain size and concentration, flooding conditions, and slope—and the dependent levee variables. We find considerable variation in levee presence and shape in our field data. On the Muscatatuck River levees occur on 30% of the banks compared to 10% on the White River. Moreover, levees on the Muscatatuck are on average 3 times wider than the White River. This is consistent with the observation that the Muscatatuck is finer-grained compared to the White River and points to sedimentology being an important control on levee geomorphology. Future work includes building a morphodynamic model to understand how different hydrodynamic and geomorphic conditions control levee geometry.

Geomorphological aspects of road construction in a cold environment, Finland

NASA Astrophysics Data System (ADS)

Seppälä, Matti

1999-12-01

Traditionally, road alignments followed easy landscapes and suitable landforms. When traffic and the size and weight of vehicles increased and higher speeds were used, straighter roads were required; the easygoing relief could not always be used, and problems arose. Road contractors could save money in building and maintenance costs by considering the geomorphic facts. The examples from Finland document why road construction is very expensive in the conditions generated by severe winters. In Finland, more paved roads cross the Arctic Circle than in the whole of North America. This paper gives examples of geomorphic elements affecting road construction in a cold environment: eskers, drumlins, plains of late and postglacial glaciolacustrine and marine sediments, mires, steep rock cliffs, river channels and ice-dams, fluvial erosion, and palsas. Solutions to these problems include removal of frost sensible materials and replacement by more favorable sediments. Road surfaces, kept snow-free in the wintertime, are subjected to deep freezing. The maintenance of roads can be supported with some solutions that affect snowdrift and icing problems, avoidance of geomorphic factors that cause problems, and by using natural processes to help people. Some examples of how road construction affects geomorphic processes and vice versa are provided. For example, bridges block moving river ice, and on special occasions, road banks cause icing.

Incorporating ecogeomorphic feedbacks to better understand resiliency in streams: A review and directions forward

NASA Astrophysics Data System (ADS)

Atkinson, Carla L.; Allen, Daniel C.; Davis, Lisa; Nickerson, Zachary L.

2018-03-01

Decades of interdisciplinary research show river form and function depends on interactions between the living and nonliving world, but a dominant paradigm underlying ecogeomorphic work consists of a top-down, unidirectional approach with abiotic forces driving biotic systems. Stream form and location within the stream network does dictate the habitat and resources available for organisms and overall community structure. Yet this traditional hierarchal framework on its own is inadequate in communicating information regarding the influence of biological systems on fluvial geomorphology that lead to changes in channel morphology, sediment cycling, and system-scale functions (e.g., sediment yield, biogeochemical nutrient cycling). Substantial evidence that organisms influence fluvial geomorphology exists, specifically the ability of aquatic vegetation and lotic animals to modify flow velocities and sediment deposition and transport - thus challenging the traditional hierarchal framework. Researchers recognize the need for ecogeomorphic frameworks that conceptualize feedbacks between organisms, sediment transport, and geomorphic structure. Furthermore, vital ecosystem processes, such as biogeochemical nutrient cycling represent the conversations that are occurring between geomorphological and biological systems. Here we review and synthesize selected case studies highlighting the role organisms play in moderating geomorphic processes and likely interact with these processes to have an impact on an essential ecosystem process, biogeochemical nutrient recycling. We explore whether biophysical interactions can provide information essential to improving predictions of system-scale river functions, specifically sediment transport and biogeochemical cycling, and discuss tools used to study these interactions. We suggest that current conceptual frameworks should acknowledge that hydrologic, geomorphologic, and ecologic processes operate on different temporal scales, generating bidirectional feedback loops over space and time. Hydro- and geomorphologic processes, operating episodically during bankfull conditions, influence ecological processes (e.g., biogeochemical cycling) occurring over longer time periods during base-flow conditions. This ecological activity generates the antecedent conditions that influence the hydro- and geomorphologic processes occurring during the next high flow event, creating a bidirectional feedback. This feedback should enhance the resiliency of fluvial landforms and ecosystem processes, allowing physical and biological processes to pull and push against each other over time.

Optimality approaches to describe characteristic fluvial patterns on landscapes

PubMed Central

Paik, Kyungrock; Kumar, Praveen

2010-01-01

Mother Nature has left amazingly regular geomorphic patterns on the Earth's surface. These patterns are often explained as having arisen as a result of some optimal behaviour of natural processes. However, there is little agreement on what is being optimized. As a result, a number of alternatives have been proposed, often with little a priori justification with the argument that successful predictions will lend a posteriori support to the hypothesized optimality principle. Given that maximum entropy production is an optimality principle attempting to predict the microscopic behaviour from a macroscopic characterization, this paper provides a review of similar approaches with the goal of providing a comparison and contrast between them to enable synthesis. While assumptions of optimal behaviour approach a system from a macroscopic viewpoint, process-based formulations attempt to resolve the mechanistic details whose interactions lead to the system level functions. Using observed optimality trends may help simplify problem formulation at appropriate levels of scale of interest. However, for such an approach to be successful, we suggest that optimality approaches should be formulated at a broader level of environmental systems' viewpoint, i.e. incorporating the dynamic nature of environmental variables and complex feedback mechanisms between fluvial and non-fluvial processes. PMID:20368257

Ridge Orientations of the Ridge-Forming Unit, Sinus Meridiani, Mars-A Fluvial Explanation

NASA Technical Reports Server (NTRS)

Wilkinson, M. Justin; Herridge, A.

2013-01-01

Imagery and MOLA data were used in an analysis of the ridge-forming rock unit (RFU) exposed in Sinus Meridiani (SM). This unit shows parallels at different scales with fluvial sedimentary bodies. We propose the terrestrial megafan as the prime analog for the RFU, and likely for other members of the layered units. Megafans are partial cones of fluvial sediment, with radii up to hundreds of km. Although recent reviews of hypotheses for the RFU units exclude fluvial hypotheses [1], inverted ridges in the deserts of Oman have been suggested as putative analogs for some ridges [2], apparently without appreciating The wider context in which these ridges have formed is a series of megafans [3], a relatively unappreciated geomorphic feature. It has been argued that these units conform to the megafan model at the regional, subregional and local scales [4]. At the regional scale suites of terrestrial megafans are known to cover large areas at the foot of uplands on all continents - a close parallel with the setting of the Meridiani sediments at the foot of the southern uplands of Mars, with its incised fluvial systems leading down the regional NW slope [2, 3] towards the sedimentary units. At the subregional scale the layering and internal discontinuities of the Meridiani rocks are consistent, inter alia, with stacked fluvial units [4]. Although poorly recognized as such, the prime geomorphic environment in which stream channel networks cover large areas, without intervening hillslopes, is the megafan [see e.g. 4]. Single megafans can reach 200,000 km2 [5]. Megafans thus supply an analog for areas where channel-like ridges (as a palimpsest of a prior landscape) cover the intercrater plains of Meridiani [6]. At the local, or river-reach scale, the numerous sinuous features of the RFU are suggestive of fluvial channels. Cross-cutting relationships, a common feature of channels on terrestrial megafans, are ubiquitous. Desert megafans show cemented paleo-channels as inverted topography [4] with all these characteristics.

Application of sedimentary-structure interpretation to geoarchaeological investigations in the Colorado River Corridor, Grand Canyon, Arizona, USA

USGS Publications Warehouse

Draut, A.E.; Rubin, D.M.; Dierker, J.L.; Fairley, H.C.; Griffiths, R.E.; Hazel, J.E.; Hunter, R.E.; Kohl, K.; Leap, L.M.; Nials, F.L.; Topping, D.J.; Yeatts, M.

2008-01-01

We present a detailed geoarchaeological study of landscape processes that affected prehistoric formation and modern preservation of archaeological sites in three areas of the Colorado River corridor in Grand Canyon, Arizona, USA. The methods used in this case study can be applied to any locality containing unaltered, non-pedogenic sediments and, thus, are particularly relevant to geoarchaeology in arid regions. Resolving the interaction of fluvial, aeolian, and local runoff processes in an arid-land river corridor is important because the archaeological record in arid lands tends to be concentrated along river corridors. This study uses sedimentary structures and particle-size distributions to interpret landscape processes; these methods are commonplace in sedimentology but prove also to be valuable, though less utilized, in geoarchaeology and geomorphology. In this bedrock canyon, the proportion of fluvial sediment generally decreases with distance away from the river as aeolian, slope-wash, colluvial, and debris-flow sediments become more dominant. We describe a new facies consisting of 'flood couplets' that include a lower, fine-grained fluvial component and an upper, coarser, unit that reflects subaerial reworking at the land surface between flood events. Grain-size distributions of strata that lack original sedimentary structures are useful within this river corridor to distinguish aeolian deposits from finer-grained fluvial deposits that pre-date the influence of the upstream Glen Canyon Dam on the Colorado River. Identification of past geomorphic settings is critical for understanding the history and preservation of archaeologically significant areas, and for determining the sensitivity of archaeological sites to dam operations. Most archaeological sites in the areas studied were formed on fluvial deposits, with aeolian deposition acting as an important preservation agent during the past millennium. Therefore, the absence of sediment-rich floods in this regulated river, which formerly deposited large fluvial sandbars from which aeolian sediment was derived, has substantially altered processes by which the prehistoric, inhabited landscape formed, and has also reduced the preservation potential of many significant cultural sites.

Geomorphology, active tectonics, and landscape evolution in the Mid-Atlantic region: Chapter

USGS Publications Warehouse

Pazzaglia, Frank J.; Carter, Mark W.; Berti, Claudio; Counts, Ronald C.; Hancock, Gregory S.; Harbor, David; Harrison, Richard W.; Heller, Matthew J.; Mahan, Shannon; Malenda, Helen; McKeon, Ryan; Nelson, Michelle S.; Prince, Phillip; Rittenour, Tammy M.; Spotilla, James; Whittecar, G. Richard

2015-01-01

In 2014, the geomorphology community marked the 125th birthday of one of its most influential papers, “The Rivers and Valleys of Pennsylvania” by William Morris Davis. Inspired by Davis’s work, the Appalachian landscape rapidly became fertile ground for the development and testing of several grand landscape evolution paradigms, culminating with John Hack’s dynamic equilibrium in 1960. As part of the 2015 GSA Annual Meeting, the Geomorphology, Active Tectonics, and Landscape Evolution field trip offers an excellent venue for exploring Appalachian geomorphology through the lens of the Appalachian landscape, leveraging exciting research by a new generation of process-oriented geomorphologists and geologic field mapping. Important geomorphologic scholarship has recently used the Appalachian landscape as the testing ground for ideas on long- and short-term erosion, dynamic topography, glacial-isostatic adjustments, active tectonics in an intraplate setting, river incision, periglacial processes, and soil-saprolite formation. This field trip explores a geologic and geomorphic transect of the mid-Atlantic margin, starting in the Blue Ridge of Virginia and proceeding to the east across the Piedmont to the Coastal Plain. The emphasis here will not only be on the geomorphology, but also the underlying geology that establishes the template and foundation upon which surface processes have etched out the familiar Appalachian landscape. The first day focuses on new and published work that highlights Cenozoic sedimentary deposits, soils, paleosols, and geomorphic markers (terraces and knickpoints) that are being used to reconstruct a late Cenozoic history of erosion, deposition, climate change, and active tectonics. The second day is similarly devoted to new and published work documenting the fluvial geomorphic response to active tectonics in the Central Virginia seismic zone (CVSZ), site of the 2011 M 5.8 Mineral earthquake and the integrated record of Appalachian erosion preserved on the Coastal Plain. The trip concludes on Day 3, joining the Kirk Bryan Field Trip at Great Falls, Virginia/ Maryland, to explore and discuss the dramatic processes of base-level fall, fluvial incision, and knickpoint retreat.

River networks as ecological corridors: A coherent ecohydrological perspective

NASA Astrophysics Data System (ADS)

Rinaldo, Andrea; Gatto, Marino; Rodriguez-Iturbe, Ignacio

2018-02-01

This paper draws together several lines of argument to suggest that an ecohydrological framework, i.e. laboratory, field and theoretical approaches focused on hydrologic controls on biota, has contributed substantially to our understanding of the function of river networks as ecological corridors. Such function proves relevant to: the spatial ecology of species; population dynamics and biological invasions; the spread of waterborne disease. As examples, we describe metacommunity predictions of fish diversity patterns in the Mississippi-Missouri basin, geomorphic controls imposed by the fluvial landscape on elevational gradients of species' richness, the zebra mussel invasion of the same Mississippi-Missouri river system, and the spread of proliferative kidney disease in salmonid fish. We conclude that spatial descriptions of ecological processes in the fluvial landscape, constrained by their specific hydrologic and ecological dynamics and by the ecosystem matrix for interactions, i.e. the directional dispersal embedded in fluvial and host/pathogen mobility networks, have already produced a remarkably broad range of significant results. Notable scientific and practical perspectives are thus open, in the authors' view, to future developments in ecohydrologic research.

The relative importance of physical and biological energy in landscape evolution

NASA Astrophysics Data System (ADS)

Turowski, J. M.; Schwanghart, W.

2017-12-01

Landscapes are formed by the interplay of uplift and geomorphic processes, including interacting and competing physical and biological processes. For example, roots re-inforce soil and thereby stabilize hillslopes and the canopy cover of the forest may mediate the impact of precipitation. Furthermore, plants and animals act as geomorphic agents, directly altering landscape response and dynamics by their actions: tree roots may crack rocks, thus changing subsurface water flows and exposing fresh material for denudation; fungi excrete acids that accelerate rates of chemical weathering, and burrowing animals displace soil and rocks while digging holes for shelter or in search of food. Energetically, landscapes can be viewed as open systems in which topography stores potential energy above a base level. Tectonic processes add energy to the system by uplift and mechanically altering rock properties. Especially in unvegetated regions, erosion and transport by wind can be an important geomorphic process. Advection of atmospheric moisture in high altitudes provides potential energy that is converted by water fluxes through catchments. At the same time, the conversion of solar energy through atmospheric and biological processes drives primary production of living organisms. If we accept that biota influence geomorphic processes, then what is their energetic contribution to landscape evolution relative to physical processes? Using two case studies, we demonstrate that all components of energy input are negligible apart from biological production, quantified by net primary productivity (NPP) and potential energy conversion by water that is placed high up in the landscape as rainfall and leaves it as runoff. Assuming that the former is representative for biological energy and the latter for physical energy, we propose that the ratio of these two values can be used as a proxy for the relative importance of biological and physical processes in landscape evolution. All necessary parameters needed to calculate the ratio (NPP, runoff, elevation) are available globally. We find that biological processes are more important in arid and semiarid regions. The wide-spread lack of water strongly limits the energy available for fluvial erosion, while biota are geomorphic engineers less sensitive to water shortage.

Simulation of ground-water flow of the coastal plain aquifers in parts of Maryland, Delaware, and the District of Columbia

USGS Publications Warehouse

Fleck, W.B.; Vroblesky, D.A.

1996-01-01

Geomorphic processes and the aquatic habitat of the Redwood Creek basin were studied extensively between 1973 and 1983. This volume contains 22 separate articles by 32 investigators who studied geology, major storms, timber harvesting and its role on accelerating erosion, mass movement, fluvial erosion, sediment transport and storage, stream channel response to storms and landuse, stream habitat, and stream chemistry. This research describes a rapidly eroding landscape that is sensitive to effects of both landuse and major storms.

Titan Polar Landscape Evolution

NASA Technical Reports Server (NTRS)

Moore, Jeffrey M.

2016-01-01

With the ongoing Cassini-era observations and studies of Titan it is clear that the intensity and distribution of surface processes (particularly fluvial erosion by methane and Aeolian transport) has changed through time. Currently however, alternate hypotheses substantially differ among specific scenarios with respect to the effects of atmospheric evolution, seasonal changes, and endogenic processes. We have studied the evolution of Titan's polar region through a combination of analysis of imaging, elevation data, and geomorphic mapping, spatially explicit simulations of landform evolution, and quantitative comparison of the simulated landscapes with corresponding Titan morphology. We have quantitatively evaluated alternate scenarios for the landform evolution of Titan's polar terrain. The investigations have been guided by recent geomorphic mapping and topographic characterization of the polar regions that are used to frame hypotheses of process interactions, which have been evaluated using simulation modeling. Topographic information about Titan's polar region is be based on SAR-Topography and altimetry archived on PDS, SAR-based stereo radar-grammetry, radar-sounding lake depth measurements, and superposition relationships between geomorphologic map units, which we will use to create a generalized topographic map.

Characterizing the Iron Wash fault: A fault line scarp in Utah

NASA Astrophysics Data System (ADS)

Kozaci, O.; Ostenaa, D.; Goodman, J.; Zellman, M.; Hoeft, J.; Sowers, J. M.; Retson, T.

2015-12-01

The Iron Wash fault (IWF) is an approximately 30 mile-long, NW-SE trending structure, oriented perpendicular to the San Rafael Monocline near Green River in Utah. IWF exhibits well-expressed geomorphic features such as a linear escarpment with consistently north side down displacement. The fault coincides with an abrupt change in San Rafael Monocline dip angle along its eastern margin. The IWF is exposed in incised drainages where Jurassic Navajo sandstone (oldest) and Lower Carmel Formation (old), are juxtaposed against Jurassic Entrada sandstone (younger) and Quaternary alluvium (youngest). To assess the recency of activity of the IWF we performed detailed geomorphic mapping and a paleoseismic trenching investigation. A benched trench was excavated across a Quaternary fluvial terrace remnant across the mapped trace of the IWF. The uppermost gravel units and overlying colluvium are exposed in the trench across the projection of the fault. In addition, we mapped the basal contact of the Quaternary gravel deposit in relation to the adjacent fault exposures in detail to show the geometry of the basal contact near and across the fault. We find no evidence of vertical displacement of these Quaternary gravels. A preliminary U-series date of calcite cementing unfaulted fluvial gravels and OSL dating of a sand lens within the unfaulted fluvial gravels yielded approximately 304,000 years and 78,000 years, respectively. These preliminary results of independent dating methods constrains the timing of last activity of the IWF to greater than 78,000 years before present suggesting that IWF not an active structure. Its distinct geomorphic expression is most likely the result of differential erosion, forming a fault-line scarp.

Climatic implications of correlated upper Pleistocene glacial and fluvial deposits on the Cinca and Gallego rivers, NE Spain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewis, Claudia J; Mcdonald, Eric; Sancho, Carlos

We correlate Upper Pleistocene glacial and fluvial deposits of the Cinca and Gallego River valleys (south central Pyrenees and Ebro basin, Spain) using geomorphic position, luminescence dates, and time-related trends in soil development. The ages obtained from glacial deposits indicate glacial periods at 85 {+-} 5 ka, 64 {+-} 11 ka, and 36 {+-} 3 ka (from glacial till) and 20 {+-} 3 ka (from loess). The fluvial drainage system, fed by glaciers in the headwaters, developed extensive terrace systems in the Cinca River valley at 178 {+-} 21 ka, 97 {+-} 16 ka, 61 {+-} 4 ka, 47 {+-}more » 4 ka, and 11 {+-} 1 ka, and in the Gallego River valley at 151 {+-} 11 ka, 68 {+-} 7 ka, and 45 {+-} 3 ka. The times of maximum geomorphic activity related to cold phases coincide with Late Pleistocene marine isotope stages and heinrich events. The maximum extent of glaciers during the last glacial occurred at 64 {+-} 11 ka, and the terraces correlated with this glacial phase are the most extensive in both the Cinca (61 {+-} 4 ka) and Gallego (68 {+-} 7 ka) valleys, indicating a strong increase in fluvial discharge and availability of sediments related to the transition to deglaciation. The global Last Glacial Maximum is scarcely represented in the south central Pyrenees owing to dominantly dry conditions at that time. Precipitation must be controlled by the position of the Iberian Peninsula with respect to the North Atlantic atmospheric circulation system. The glacial systems and the associated fluvial dynamic seem sensitive to (1) global climate changes controlled by insolation, (2) North Atlantic thermohaline circulation influenced by freshwater pulses into the North Atlantic, and (3) anomalies in atmospheric circulation in the North Atlantic controlling precipitation on the Iberian peninsula. The model of glacial and fluvial evolution during the Late Pleistocene in northern Spain could be extrapolated to other glaciated mountainous areas in southern Europe.« less

Long-Term Interactions of Streamflow Generation and River Basin Morphology

NASA Astrophysics Data System (ADS)

Huang, X.; Niemann, J.

2005-12-01

It is well known that the spatial patterns and dynamics of streamflow generation processes depend on river basin topography, but the impact of streamflow generation processes on the long-term evolution of river basins has not drawn as much attention. Fluvial erosion processes are driven by streamflow, which can be produced by Horton runoff, Dunne runoff, and groundwater discharge. In this analysis, we hypothesize that the dominant streamflow generation process in a basin affects the spatial patterns of fluvial erosion and that the nature of these patterns changes for storm events with differing return periods. Furthermore, we hypothesize that differences in the erosion patterns modify the topography over the long term in a way that promotes and/or inhibits the other streamflow generation mechanisms. In order to test these hypotheses, a detailed hydrologic model is imbedded into an existing landscape evolution model. Precipitation events are simulated with a Poisson process and have random intensities and durations. The precipitation is partitioned between Horton runoff and infiltration to groundwater using a specified infiltration capacity. Groundwater flow is described by a two-dimensional Dupuit equation for a homogeneous, isotropic, unconfined aquifer with an irregular underlying impervious layer. Dunne runoff occurs when precipitation falls on locations where the water table reaches the land surface. The combined hydrologic/geomorphic model is applied to the WE-38 basin, an experimental watershed in Pennsylvania that has substantial available hydrologic data. First, the hydrologic model is calibrated to reproduce the observed streamflow for 1990 using the observed rainfall as the input. Then, the relative roles of Horton runoff, Dunne runoff, and groundwater discharge are controlled by varying the infiltration capacity of the soil. For each infiltration capacity, the hydrologic and geomorphic behavior of the current topography is analyzed and the long-term evolution of the basin is simulated. The results indicate that the topography can be divided into three types of locations (unsaturated, saturated, and intermittently saturated) which control the patterns of streamflow generation for events with different return periods. The results also indicate that the streamflow generation processes can produce different geomorphic effective events at upstream and downstream locations. The model also suggests that a topography dominated by groundwater discharge evolves over a long period of time to a shape that tends to inhibit the development of saturated areas and Dunne runoff.

Complex response of a midcontinent north America drainage system to late Wisconsinan sedimentation

USGS Publications Warehouse

Bettis, E. Arthur; Autin, W.J.

1997-01-01

The geomorphic evolution of Mud Creek basin in eastern Iowa, U.S.A. serves to illustrate how geomorphic influences such as sediment supply, valley gradient, climate, and vegetation are recorded in the alluvial stratigraphic record. Sediment supply to the fluvial system increased significantly during the late Wisconsinan through a combination of periglacial erosion and loess accumulation. Subsequent evolution of the Holocene alluvial stratigraphic record reflects long-term routing of the late Wisconsinan sediment through the drainage basin in a series of cut-and-fill cycles whose timing was influenced by hydrologic response to change in climate and vegetation. When viewed in a regional context, the alluvial stratigraphic record appears to reflect a long-term complex response of the fluvial system to increased sediment supply during the late Wisconsinan. Hydrologic and sediment-supply changes accompanying the spread of Euroamerican agriculture to the basin in the 180Os dramatically upset trends in sedimentation and channel behavior established during the Holocene. Copyright ?? 1997, SEPM (Society for Sedimentary Geology).

GIS- and field based mapping of geomorphological changes in a glacier retreat area: A case study from the Kromer valley, Silvretta Alps (Austria)

NASA Astrophysics Data System (ADS)

Guttmann, Markus; Pöppl, Ronald

2017-04-01

Global warming results in an ongoing retreat of Alpine glaciers, leaving behind large amounts of easily erodible sediments. As a consequence processes like rockfalls, landslides and debris flows as well as fluvial processes occur more frequently in pro- and paraglacial areas, often involving catastrophic consequences for humans and infrastructure in the affected valleys. The main objective of the presented work was to map and spatially quantify glacier retreat and geomorphological changes in the Kromer valley, Silvretta Alps (Austria) by applying GIS- and field-based geomorphological mapping. In total six geomorphological maps (1950s, 1970s, 2001, 2006, 2012, and 2016) were produced and analyzed in the light of the study aim. First results have shown a significant decrease of total glaciated area from 96 ha to 53 ha which was accompanied by increased proglacial geomorphic activity (i.e. fluvial processes, rockfalls, debris flows, shallow landslides) in the last 15 years. More detailed results will be presented at the EGU General Assembly 2017.

Quaternary Morphodynamics of Fluvial Dispersal Systems Revealed: The Fly River, PNG, and the Sunda Shelf, SE Asia, simulated with the Massively Parallel GPU-based Model 'GULLEM'

NASA Astrophysics Data System (ADS)

Aalto, R. E.; Lauer, J. W.; Darby, S. E.; Best, J.; Dietrich, W. E.

2015-12-01

During glacial-marine transgressions vast volumes of sediment are deposited due to the infilling of lowland fluvial systems and shallow shelves, material that is removed during ensuing regressions. Modelling these processes would illuminate system morphodynamics, fluxes, and 'complexity' in response to base level change, yet such problems are computationally formidable. Environmental systems are characterized by strong interconnectivity, yet traditional supercomputers have slow inter-node communication -- whereas rapidly advancing Graphics Processing Unit (GPU) technology offers vastly higher (>100x) bandwidths. GULLEM (GpU-accelerated Lowland Landscape Evolution Model) employs massively parallel code to simulate coupled fluvial-landscape evolution for complex lowland river systems over large temporal and spatial scales. GULLEM models the accommodation space carved/infilled by representing a range of geomorphic processes, including: river & tributary incision within a multi-directional flow regime, non-linear diffusion, glacial-isostatic flexure, hydraulic geometry, tectonic deformation, sediment production, transport & deposition, and full 3D tracking of all resulting stratigraphy. Model results concur with the Holocene dynamics of the Fly River, PNG -- as documented with dated cores, sonar imaging of floodbasin stratigraphy, and the observations of topographic remnants from LGM conditions. Other supporting research was conducted along the Mekong River, the largest fluvial system of the Sunda Shelf. These and other field data provide tantalizing empirical glimpses into the lowland landscapes of large rivers during glacial-interglacial transitions, observations that can be explored with this powerful numerical model. GULLEM affords estimates for the timing and flux budgets within the Fly and Sunda Systems, illustrating complex internal system responses to the external forcing of sea level and climate. Furthermore, GULLEM can be applied to most ANY fluvial system to explore processes across a wide range of temporal and spatial scales. The presentation will provide insights (& many animations) illustrating river morphodynamics & resulting landscapes formed as a result of sea level oscillations. [Image: The incised 3.2e6 km^2 Sundaland domain @ 431ka

Geomorphic controls on Pleistocene knickpoint migration in Alpine valleys

NASA Astrophysics Data System (ADS)

Leith, Kerry; Fox, Matt; Moore, Jeffrey R.; Brosda, Julian; Krautblatter, Michael; Loew, Simon

2014-05-01

Recent insights into sub-glacial bedrock stress conditions suggest that the erosional efficiency of glaciers may reduce markedly following a major erosional cycle [Leith et al., 2013]. This implies that the formation of large glacial valleys within the Alps is likely to have occurred shortly after the onset of 100 ky glacial-interglacial cycles (at the mid-Pleistocene Revolution (MPR)). The majority of landscape change since this time may have therefore been driven by sub-aerial processes. This hypothesis is supported by observations of hillslope and channel morphology within Canton Valais (Switzerland), where major tributary valleys display a common morphology along their length, hinting at a shared geomorphic history. Glaciers currently occupy the headwaters of many catchments, while the upper reaches of rivers flow across extensive alluvial planes before abruptly transitioning to steep channels consisting of mixed bedrock and talus fan deposits. The rivers then converge to flow out over the alluvial plane of the Rhone Valley. Characteristically rough topographies within the region are suggested to mark the progressive transition from a glacial to fluvially-dominated landscape, and correlate well with steepened river channel sections determined from a 2.5 m resolution LiDAR DEM. We envisage a landscape in which ongoing tectonic uplift drives the emergence of Alpine bedrock through massive sedimentary valley infills (currently concentrated in the Rhone Valley), whose elevation is fixed by the consistent fluvial baselevel at Lake Geneva. As fluvial incision ceases at the onset of glaciation, continued uplift causes the formation of knickpoints at the former transition from bedrock to sedimentary infill. These knickpoints will then propagate upstream during subsequent interglacial periods. By investigating channel morphologies using an approach based on the steady-state form of the stream power equation, we can correlate steepened channel reaches (degraded knickpoints) across most major tributaries south of the Rhone River. The timing of apparent uplift events correlates well with that of cool Marine Isotope Stages derived from global oxygen isotope data up to the beginning of MIS 12. A weak correlation up to the beginning of MIS 18 suggests initial glacial incision may have occurred some time during MIS 14 - 20, and valley development has since been driven by fluvial processes. Leith, K., J. R. Moore, F. Amann, and S. Loew (2013), Sub-glacial extensional fracture development and implications for Alpine valley evolution, J. Geophys. Res. Earth Surf., doi:10.1002/2012JF002691.

Constraints on the Miocene landscape evolution of the Eastern Alps from the Kalkspitze region, Niedere Tauern (Austria)

NASA Astrophysics Data System (ADS)

Dertnig, Florian; Stüwe, Kurt; Woodhead, Jon; Stuart, Finlay M.; Spötl, Christoph

2017-12-01

In order to unravel aspects of the Miocene landscape evolution of the eastern European Alps, we present geomorphic and isotopic data from the western Niedere Tauern region (Austria). The region is critical for such interpretations, because it is one of the few regions along the topographic axis of the Eastern Alps where the highest peaks (up to 2500 m a.s.l.) are dominated by limestone. As such, the region contains a record of Miocene landscape-forming events that survived the Pleistocene glaciations, not preserved elsewhere in the central Eastern Alps. This record includes karst caves, karstified planation surfaces and crystalline fluvial pebbles (Augenstein Formation) preserved on planation surfaces and in karst caves. Caves in the region occur in three distinct levels that correlate with well-known cave levels in the Northern Calcareous Alps, although they are somewhat higher in the Niedere Tauern. In part, these cave elevations also correlate with three planation surfaces and knickpoints of major streams draining the region, testifying their pre-glacial origin. We report details of a karst cave (Durchgangshöhle) from the highest cave level located at 2340 m a.s.l. In this cave, allochthonous fluvial gravels are present, overgrown by speleothems. One speleothem yielded an early middle Pleistocene U-Pb age (682 ± 17 ka). We regard this as a minimum age for the erosion of the fluvial cave deposits during Marine Isotope Stages 17 or 16. Carbon and oxygen isotope data of these speleothems imply a climate that is consistent with this interpretation. Cosmogenic 21Ne data of fluvial quartz clasts collected from the surface on plateaus of the Northern Calcareous Alps suggest minimum exposure durations of 115 and 262 ka. They probably reflect successive exposure since removal of the sediment cover of the Oligocene Augenstein Formation during the Pleistocene. While our geochronological data fail to record aspects of the earlier Miocene uplift history, they are consistent with the overall geomorphic history inferred from the geomorphic markers. This suggests that the Niedere Tauern share a common uplift history with the Northern Calcareous Aps and implies a moderate south-north topographic gradient that has been maintained since the Miocene.

Geomorphic and habitat response to a large-dam removal in a Mediterranean river

NASA Astrophysics Data System (ADS)

Harrison, L.; East, A. E.; Smith, D. P.; Bond, R.; Logan, J. B.; Nicol, C.; Williams, T.; Boughton, D. A.; Chow, K.

2017-12-01

The presence of large dams has fundamentally altered physical and biological processes in riverine ecosystems, and dam removal is becoming more common as a river restoration strategy. We used a before-after-control-impact study design to investigate the geomorphic and habitat response to removal of 32-m-high San Clemente Dam on the Carmel River, CA. The project represents the first major dam removal in a Mediterranean river and is also unique among large dam removals in that most reservoir sediment was sequestered in place. We found that in the first year post-removal, a sediment pulse migrated 3.5 km downstream, filling pools and the interstitial pore spaces of gravels with sand. These sedimentary and topographic changes initially reduced the overall quality of steelhead (O. mykiss) spawning and rearing habitat in impacted reaches. Over the second winter after dam removal, a sequence of high flows flushed large volumes of sand from pools and mobilized the river bed throughout much of the active channel. The floods substantially altered fluvial evolution in the upper part of the reservoir, promoting new avulsion and the subsequent delivery of gravel and large wood to below dam reaches. These geomorphic processes increased the availability of spawning-sized gravel and enhanced channel complexity in reaches within several km of the former dam, which should improve habitat for multiple life stages of steelhead. Results indicate that when most reservoir sediment remains impounded, high flows become more important drivers of geomorphic and habitat change than dam removal alone. In such cases, the rates at which biophysical processes are reestablished will depend largely on post-dam removal flow sequencing and the upstream supply of sediment and large wood.

Scaling relations in mountain streams: colluvial and Quaternary controls

NASA Astrophysics Data System (ADS)

Brardinoni, Francesco; Hassan, Marwan; Church, Michael

2010-05-01

In coastal British Columbia, Canada, the glacial palimpsest profoundly affects the geomorphic structure of mountain drainage basins. In this context, by combining remotely sensed, field- and GIS-based data, we examine the scaling behavior of bankfull width and depth with contributing area in a process-based framework. We propose a novel approach that, by detailing interactions between colluvial and fluvial processes, provides new insights on the geomorphic functioning of mountain channels. This approach evaluates the controls exerted by a parsimonious set of governing factors on channel size. Results indicate that systematic deviations from simple power-law trends in bankfull width and depth are common. Deviations are modulated by interactions between the inherited glacial and paraglacial topography (imposed slope), coarse grain-size fraction, and chiefly the rate of colluvial sediment delivery to streams. Cumulatively, departures produce distal cross-sections that are typically narrower and shallower than expected. These outcomes, while reinforcing the notion that mountain drainage basins in formerly glaciated systems are out of balance with current environmental conditions, show that cross-sectional scaling relations are useful metrics for understanding colluvial-alluvial interactions.

Hydrogeomorphic and hydraulic habitats of the Niobrara River, Nebraska-with special emphasis on the Niobrara National Scenic River

USGS Publications Warehouse

Alexander, Jason S.; Zelt, Ronald B.; Schaepe, Nathan J.

2010-01-01

The Niobrara River is an ecologically and economically important resource in Nebraska. The Nebraska Department of Natural Resources' recent designation of the hydraulically connected surface- and groundwater resources of the Niobrara River Basin as ?fully appropriated? has emphasized the importance of understanding linkages between the physical and ecological dynamics of the Niobrara River so it can be sustainably managed. In cooperation with the Nebraska Game and Parks Commission, the U.S. Geological Survey investigated the hydrogeomorphic and hydraulic attributes of the Niobrara River in northern Nebraska. This report presents the results of an analysis of hydrogeomorphic segments and hydraulic microhabitats of the Niobrara River and its valley for the approximately 330-mile reach from Dunlap Diversion Dam to its confluence with the Missouri River. Two spatial scales were used to examine and quantify the hydrogeomorphic segments and hydraulic microhabitats of the Niobrara River: a basin scale and a reach scale. At the basin scale, digital spatial data and hydrologic data were analyzed to (1) test for differences between 36 previously determined longitudinal hydrogeomorphic segments; (2) quantitatively describe the hydrogeomorphic characteristics of the river and its valley; and (3) evaluate differences in hydraulic microhabitat over a range of flow regimes among three fluvial geomorphic provinces. The statistical analysis of hydrogeomorphic segments resulted in reclassification rates of 3 to 28 percent of the segments for the four descriptive geomorphic elements. The reassignment of classes by discriminant analysis resulted in a reduction from 36 to 25 total hydrogeomorphic segments because several adjoining segments shared the same ultimate class assignments. Virtually all of the segment mergers were in the Canyons and Restricted Bottoms (CRB) fluvial geomorphic province. The most frequent classes among hydrogeomorphic segments, and the dominant classes per unit length of river, are: a width-restricted valley confinement condition, sinuous-planview pattern, irregular channel width, and an alternate bar configuration. The Niobrara River in the study area flows through a diversity of fluvial geomorphic settings in its traverse across northern Nebraska. In the Meandering Bottoms (MB) fluvial geomorphic province, river discharge magnitudes are low, and the valley exerts little control on the channel-planview pattern. Within the CRB province, the river flows over a diversity of geologic formations, and the valley and river narrow and expand in approximate synchronicity. In the Braided Bottoms (BB) fluvial geomorphic province, the river primarily flows over Cretaceous Pierre Shale, the valley and channel are persistently wide, and the channel slope is generally uniform. The existence of vegetated islands and consequent multithread channel environments, indicated by a higher braided index, mostly coincided with reaches having gentler slopes and less unit stream power. Longitudinal hydrology curves indicate that the flow of the Niobrara River likely is dominated by groundwater as far downstream as Norden. Unit stream power values in the study area vary between 0 and almost 2 pounds per foot per second. Within the MB province, unit stream power steadily increases as the Niobrara gains discharge from groundwater inflow, and the channel slope steepens. The combination of steep slopes, a constrained channel width, and persistent flow within the CRB province results in unit stream power values that are between three and five times greater than those in less confined segments with comparable or greater discharges. With the exception of hydrogeomorphic segment 3, which is affected by Spencer Dam, unit stream power values in the BB province are generally uniform. Channel sinuosity values in the study area varied generally between 1 and 2.5, but with locally higher values measured in the MB province and at the entrenched bedrock me

Geomorphic and Aqueous Chemistry of a Portion of the Upper Rio Tinto System, Spain

NASA Technical Reports Server (NTRS)

Osburn, M. R.; Fernandez-Remolar, D. C.; Arvidson, R. E.; Morris, R. V.; Ming, D.; Prieto-Ballesteros, O.; Amils, R.; Stein, T. C.; Heil-Chapdelaine, V.; Friedlander, L. R.;

Geomorphic Segmentation, Hydraulic Geometry, and Hydraulic Microhabitats of the Niobrara River, Nebraska - Methods and Initial Results

USGS Publications Warehouse

Alexander, Jason S.; Zelt, Ronald B.; Schaepe, Nathaniel J.

2009-01-01

The Niobrara River of Nebraska is a geologically, ecologically, and economically significant resource. The State of Nebraska has recognized the need to better manage the surface- and ground-water resources of the Niobrara River so they are sustainable in the long term. In cooperation with the Nebraska Game and Parks Commission, the U.S. Geological Survey is investigating the hydrogeomorphic settings and hydraulic geometry of the Niobrara River to assist in characterizing the types of broad-scale physical habitat attributes that may be of importance to the ecological resources of the river system. This report includes an inventory of surface-water and ground-water hydrology data, surface water-quality data, a longitudinal geomorphic segmentation and characterization of the main channel and its valley, and hydraulic geometry relations for the 330-mile section of the Niobrara River from Dunlap Diversion Dam in western Nebraska to the Missouri River confluence. Hydraulic microhabitats also were analyzed using available data from discharge measurements to demonstrate the potential application of these data and analysis methods. The main channel of the Niobrara was partitioned into three distinct fluvial geomorphic provinces: an upper province characterized by open valleys and a sinuous, equiwidth channel; a central province characterized by mixed valley and channel settings, including several entrenched canyon reaches; and a lower province where the valley is wide, yet restricted, but the river also is wide and persistently braided. Within the three fluvial geomorphic provinces, 36 geomorphic segments were identified using a customized, process-orientated classification scheme, which described the basic physical characteristics of the Niobrara River and its valley. Analysis of the longitudinal slope characteristics indicated that the Niobrara River longitudinal profile may be largely bedrock-controlled, with slope inflections co-located at changes in bedrock type at river level. Hydraulic geometry relations indicated that local (at-a-station) channel adjustments of the Niobrara River to changing discharge are accommodated mainly by changes in velocity, and streamwise adjustments are accommodated through changes in channel width. Downstream hydraulic geometry relations are in general agreement with values previously published for rivers of the Great Plains, but coefficients are likely skewed low because the locations of the streamflow-gaging stations used in this analysis are located at natural or engineered constrictions and may not be accurately representing downstream adjustment processes of the Niobrara River. A demonstration analysis of hydraulic microhabitat attributes at a single station indicated that changes in velocity-related habitat types is the primary microhabitat adjustment over a range of discharges, but the magnitude of that adjustment for any particular discharge is temporally variable.

Geomorphic change in Dingzi Bay, East China since the 1950s: impacts of human activity and fluvial input

NASA Astrophysics Data System (ADS)

Tian, Qing; Wang, Qing; Liu, Yalong

2017-06-01

This study examines the geomorphic evolution of Dingzi Bay, East China in response to human activity and variations in fluvial input since the 1950s. The analysis is based on data from multiple mathematical methods, along with information obtained from Remote Sensing, Geographic Information System and Global Position System technology. The results show that the annual runoff and sediment load discharged into Dingzi Bay display significant decreasing trends overall, and marked downward steps were observed in 1966 and 1980. Around 60%-80% of the decline is attributed to decreasing precipitation in the Wulong River Basin. The landform types in Dingzi Bay have changed significantly since the 1950s, especially over the period between 1981 and 1995. Large areas of tidal flats, swamp, salt fields, and paddy fields have been reclaimed, and aquaculture ponds have been constructed. Consequently, the patterns of erosion and deposition in the bay have changed substantially. Despite a reduction in sediment input of 65.68% after 1966, low rates of sediment deposition continued in the bay. However, deposition rates changed significantly after 1981 owing to large-scale development in the bay, with a net depositional area approximately 10 times larger than that during 1961-1981. This geomorphic evolution stabilized following the termination of large-scale human activity in the bay after 1995. Overall, Dingzi Bay has shown a tendency towards silting-up during 1952-2010, with the bay head migrating seaward, the number of channels in the tidal creek system decreasing, and the tidal inlet becoming narrower and shorter. In conclusion, largescale development and human activity in Dingzi Bay have controlled the geomorphic evolution of the bay since the 1950s.

Geomorphic controls on fluvial carbon exports and emissions from upland swamps in eastern Australia.

PubMed

Cowley, Kirsten; Looman, Arun; Maher, Damien T; Fryirs, Kirstie

2018-03-15

Temperate Highland Peat Swamps on Sandstone (THPSS) are upland wetlands, similar to fens in the Northern Hemisphere and are found at the headwaters of low-order streams on the plateaus of Eastern Australia. They are classified as endangered ecological communities under State and National legislation. Previous works have identified particular geomorphic characteristics that are important to carbon storage in these low energy sediment accumulation zones. Changes in the geomorphic structure of THPSS, such as channelisation, may have profound implications for carbon storage. To assess the effect of channelisation on carbon budgets in these ecosystems it is essential to identify and quantify differences in carbon export, emissions and stocks of carbon of intact swamps and those that have become channelised. We undertook seasonal sampling of the perched swamp aquifers and surface waters of two intact swamps and two channelised fills in the Blue Mountains of New South Wales, Australia, to investigate differences in carbon exports and emissions between the two swamp types. We found that channelised fills' mean CO 2 emissions were almost four times higher than intact swamps with mean CH 4 emissions up to five times higher. Annual fluvial carbon exports for channelised fills were up to 18 times that of intact swamps. Channelised fill exports and emissions can represent up to 2% of the total swamp carbon stocks per annum which is 40 times higher than the intact swamps. This work clearly demonstrates that changes in geomorphic structure brought about by incision and channelisation results in profound changes to the carbon storage function of THPSS. Copyright © 2017 Elsevier B.V. All rights reserved.

Terrain-based Predictive Modeling of a Functional Riparian Corridor in a Coastal Northern California Watershed

NASA Astrophysics Data System (ADS)

Robinson, T.; Davis, J. D.

2016-12-01

Riparian corridors and their associated geomorphic landforms (e.g., channels, floodplains, and terraces) and vegetation communities (e.g., forests and wetlands) have been significantly degraded in California, prompting an expansion of efforts to delineate riparian corridors and identify priorities for conservation via deed restrictions and easements. Current techniques to delineate riparian corridors for these purposes include fixed-width buffers based on stream centerlines and digitization of woody vegetation from aerial photos. Although efficient, these delineation methods do not accurately capture the extent of ecologically functional riparian corridors and result in riparian habitat being excluded from conservation efforts while non-riparian is included. From a physical perspective, ecologically functional riparian corridors have widths that vary with topography and ample space for dynamic fluvial geomorphic processes that create and maintain river morphology and vegetation and sustain ecological interactions that extend from the stream channel laterally into upland ecosystems and up- and downstream ecosystems in longitudinal directions. New terrain-based spatial analysis techniques and high-resolution digital terrain data show promise in delineating ecologically functional riparian corridors. In this study, we compare the efficacy of three terrain-based predictors of riparian corridors that have emerged in the literature—elevation above channel, flow accumulation, and distance from channel. The results of each terrain predictor are compared with field-based indicators of the riparian corridor of an alluvial reach of Mark West Creek in Sonoma County, California (a mediterranean climate). Indicators include soil type, fluvial geomorphic landforms, and vegetation. A one-meter digital terrain model from LiDAR (Light Detection and Ranging) supplied by a NASA ROSES grant is used as the base terrain data for spatial analysis. We discuss in detail the use of regional curves of hydraulic geometry in the calculation of the elevation above channel predictor because it offers the advantage of efficiency while carrying significant potential for error.

Sediment budgets as an organizing framework in fluvial geomorphology

Treesearch

Leslie Reid; Thomas Dunne

2016-01-01

Sediment budgets describe the input, transport, storage, and export of sediment in a geomorphic system. Such budgets can be used to address questions regarding how changes in catchment conditions affect channels, how long the effects will last, and what the sequence of responses will be. This chapter defines and describes budget components, outlines strategies...

100 kyr fluvial cut-and-fill terrace cycles since the Middle Pleistocene in the southern Central Andes, NW Argentina

NASA Astrophysics Data System (ADS)

Tofelde, Stefanie; Schildgen, Taylor F.; Savi, Sara; Pingel, Heiko; Wickert, Andrew D.; Bookhagen, Bodo; Wittmann, Hella; Alonso, Ricardo N.; Cottle, John; Strecker, Manfred R.

2017-09-01

Fluvial fill terraces in intermontane basins are valuable geomorphic archives that can record tectonically and/or climatically driven changes of the Earth-surface process system. However, often the preservation of fill terrace sequences is incomplete and/or they may form far away from their source areas, complicating the identification of causal links between forcing mechanisms and landscape response, especially over multi-millennial timescales. The intermontane Toro Basin in the southern Central Andes exhibits at least five generations of fluvial terraces that have been sculpted into several-hundred-meter-thick Quaternary valley-fill conglomerates. New surface-exposure dating using nine cosmogenic 10Be depth profiles reveals the successive abandonment of these terraces with a 100 kyr cyclicity between 75 ± 7 and 487 ± 34 ka. Depositional ages of the conglomerates, determined by four 26Al/10Be burial samples and U-Pb zircon ages of three intercalated volcanic ash beds, range from 18 ± 141 to 936 ± 170 ka, indicating that there were multiple cut-and-fill episodes. Although the initial onset of aggradation at ∼1 Ma and the overall net incision since ca. 500 ka can be linked to tectonic processes at the narrow basin outlet, the superimposed 100 kyr cycles of aggradation and incision are best explained by eccentricity-driven climate change. Within these cycles, the onset of river incision can be correlated with global cold periods and enhanced humid phases recorded in paleoclimate archives on the adjacent Bolivian Altiplano, whereas deposition occurred mainly during more arid phases on the Altiplano and global interglacial periods. We suggest that enhanced runoff during global cold phases - due to increased regional precipitation rates, reduced evapotranspiration, or both - resulted in an increased sediment-transport capacity in the Toro Basin, which outweighed any possible increases in upstream sediment supply and thus triggered incision. Compared with two nearby basins that record precessional (21-kyr) and long-eccentricity (400-kyr) forcing within sedimentary and geomorphic archives, the recorded cyclicity scales with the square of the drainage basin length.

Reciprocal interactions between fluvial processes and riparian plants at multiple scales: ecogeomorphic feedbacks drive coevolution of floodplain morphology and vegetation communities

NASA Astrophysics Data System (ADS)

Stella, J. C.; Kui, L.; Diehl, R. M.; Bywater-Reyes, S.; Wilcox, A. C.; Shafroth, P. B.; Lightbody, A.

2017-12-01

Fluvial forces interact with woody riparian plants in complex ways to influence the coevolution of river morphology and floodplain plant communities. Here, we report on an integrated suite of multi-disciplinary studies that contrast the responses of plants with different morphologies, tamarisk (Tamarix spp.) and cottonwood (Populus fremontii) in terms of (1) differences in vulnerability to scour and burial during floods; (2) interactions and feedbacks between plants and river morphodynamics; and (3) long-term coevolution of river floodplains and riparian communities following flow regulation from dams. The focus of these studies is sand-bed rivers in arid-land regions where invasion by tamarisk has strongly influenced riverine plant communities and geomorphic processes. We complemented a suite of field-scale flume experiments using live seedlings to quantify the initial stages of plant-river interactions with an analysis of long-term vegetation and geomorphic changes along the dammed Bill Williams River (AZ, USA) using time-series air photographs. Vegetation-fluvial interactions varied with plant characteristics, river hydraulics and sediment conditions, across the wide range of scales we investigated. In the flume studies, tamarisk's denser crowns and stiffer stems induced greater sedimentation compared to cottonwood. This resulted in tamarisk's greater mortality from burial as small seedlings under sediment equilibrium conditions but higher relative survival in larger floods under sediment deficit scenarios, in which more cottonwoods were lost to root scour. Sediment deficit conditions, as occurs downstream of dams, induced both greater scour and greater plant loss. With larger size and at higher densities, plants' vulnerability diminished due to greater root anchoring and canopy effects on hydraulics. At the corridor scale, we observed a pattern of plant encroachment during five decades of flow regulation, in which channel narrowing and simplification was more associated with tamarisk-dominated reaches compared with native woodlands. Together, these multi-scale plant-river dynamics help explain the persistence of tamarisk along regulated rivers where catastrophic floods have been reduced and also highlight limitations of using flow releases for invasive species management.

Flood dependency of cottonwood establishment along the Missouri River, Montana, USA

USGS Publications Warehouse

Scott, M.L.; Auble, G.T.; Friedman, J.M.

1997-01-01

Flow variability plays a central role in structuring the physical environment of riverine ecosystems. However, natural variability in flows along many rivers has been modified by water management activities. We quantified the relationship between flow and establishment of the dominant tree (plains cottonwood, Populus deltoides subsp. monilifera) along one of the least hydrologically altered alluvial reaches of the Missouri River: Coal Banks Landing to Landusky, Montana. Our purpose was to refine our understanding of how local fluvial geomorphic processes condition the relationship between flow regime and cottonwood recruitment. We determined date and elevation of tree establishment and related this information to historical peak stage and discharge over a 112-yr hydrologic record. Of the excavated trees, 72% were established in the year of a flow >1400 m3/s (recurrence interval of 9.3 yr) or in the following 2 yr. Flows of this magnitude or greater create the necessary bare, moist establishment sites at an elevation high enough to allow cottonwoods to survive subsequent floods and ice jams. Almost all cottonwoods that have survived the most recent flood (1978) were established >1.2 m above the lower limit of perennial vegetation (active channel shelf). Most younger individuals were established between 0 and 1.2 m, and are unlikely to survive over the long term. Protection of riparian cottonwood forest along this National Wild and Scenic section of the Missouri River depends upon maintaining the historical magnitude, frequency, and duration of floods > 1400 m3/s. Here, a relatively narrow valley constrains lateral channel movement that could otherwise facilitate cottonwood recruitment at lower flows. Effective management of flows to promote or maintain cottonwood recruitment requires an understanding of locally dominant fluvial geomorphic processes.

Distribution of Early, Middle, and Late Noachian cratered surfaces in the Martian highlands: Implications for resurfacing events and processes

NASA Astrophysics Data System (ADS)

Irwin, Rossman P.; Tanaka, Kenneth L.; Robbins, Stuart J.

2013-02-01

Most of the geomorphic changes on Mars occurred during the Noachian Period, when the rates of impact crater degradation and valley network incision were highest. Fluvial erosion around the Noachian/Hesperian transition is better constrained than the longer-term landscape evolution throughout the Noachian Period, when the highland intercrater geomorphic surfaces developed. We interpret highland resurfacing events and processes using a new global geologic map of Mars (at 1:20,000,000 scale), a crater data set that is complete down to 1 km in diameter, and Mars Orbiter Laser Altimeter topography. The Early Noachian highland (eNh) unit is nearly saturated with craters of 32-128 km diameter, the Middle Noachian highland (mNh) unit has a resurfacing age of ~4 Ga, and the Late Noachian highland unit (lNh) includes younger composite surfaces of basin fill and partially buried cratered terrain. These units have statistically distinct ages, and their distribution varies with elevation. The eNh unit is concentrated in the high-standing Hellas basin annulus and in highland terrain that was thinly mantled by basin ejecta near 180° longitude. The mNh unit includes most of Arabia Terra, the Argyre vicinity, highland plateau areas between eNh outcrops, and the Thaumasia range. The lNh unit mostly occurs within highland basins. Crater depth/diameter ratios do not vary strongly between the eNh and mNh units, although crater losses to Noachian resurfacing appear greater in lower lying areas. Noachian resurfacing was spatially non-uniform, long-lived, and gravity-driven, more consistent with arid-zone fluvial and aeolian erosion and volcanism than with air fall mantling or mass wasting.

Degradation of the Mitchell River fluvial megafan by alluvial gully erosion increased by post-European land use change, Queensland, Australia

NASA Astrophysics Data System (ADS)

Shellberg, J. G.; Spencer, J.; Brooks, A. P.; Pietsch, T. J.

2016-08-01

Along low gradient rivers in northern Australia, there is widespread gully erosion into unconfined alluvial deposits of active and inactive floodplains. On the Mitchell River fluvial megafan in northern Queensland, river incision and fan-head trenching into Pleistocene and Holocene megafan units with sodic soils created the potential energy for a secondary cycle of erosion. In this study, rates of alluvial gully erosion into incipiently-unstable channel banks and/or pre-existing floodplain features were quantified to assess the influence of land use change following European settlement. Alluvial gully scarp retreat rates were quantified at 18 sites across the megafan using recent GPS surveys and historic air photos, demonstrating rapid increases in gully area of 1.2 to 10 times their 1949 values. Extrapolation of gully area growth trends backward in time suggested that the current widespread phase of gullying initiated between 1880 and 1950, which is post-European settlement. This is supported by young optically stimulated luminescence (OSL) dates of gully inset-floodplain deposits, LiDAR terrain analysis, historic explorer accounts of earlier gully types, and archival records of cattle numbers and land management. It is deduced that intense cattle grazing and associated disturbance concentrated in the riparian zones during the dry season promoted gully erosion in the wet season along steep banks, adjacent floodplain hollows and precursor gullies. This is a result of reduced native grass cover, increased physical disturbance of soils, and the concentration of water runoff along cattle tracks, in addition to fire regime modifications, episodic drought, and the establishment of exotic weed and grass species. Geomorphic processes operating over geologic time across the fluvial megafan predisposed the landscape to being pushed by land used change across an intrinsically close geomorphic threshold towards instability. The evolution of these alluvial gullies is discussed in terms of their initiation, development, future growth, and stabilisation, and the numerous natural and anthropogenic factors influencing their erosion.

Making riverscapes real

NASA Astrophysics Data System (ADS)

Carbonneau, Patrice; Fonstad, Mark A.; Marcus, W. Andrew; Dugdale, Stephen J.

2012-01-01

The structure and function of rivers have long been characterized either by: (1) qualitative models such as the River Continuum Concept or Serial Discontinuity Concept which paint broad descriptive portraits of how river habitats and communities vary, or (2) quantitative models, such as downstream hydraulic geometry, which rely on a limited number of measurements spread widely throughout a river basin. In contrast, authors such as Fausch et al. (2002) and Wiens (2002) proposed applying existing quantitative, spatially comprehensive ecology and landscape ecology methods to rivers. This new framework for river sciences which preserves variability and spatial relationships is called a riverine landscape or a 'riverscape'. Application of this riverscape concept requires information on the spatial distribution of organism-scale habitats throughout entire river systems. This article examines the ways in which recent technical and methodological developments can allow us to quantitatively implement and realize the riverscape concept. Using 3-cm true color aerial photos and 5-m resolution elevation data from the River Tromie, Scotland, we apply the newly developed Fluvial Information System which integrates a suite of cutting edge, high resolution, remote sensing methods in a spatially explicit framework. This new integrated approach allows for the extraction of primary fluvial variables such as width, depth, particle size, and elevation. From these first-order variables, we derive second-order geomorphic and hydraulic variables including velocity, stream power, Froude number and shear stress. Channel slope can be approximated from available topographic data. Based on these first and second-order variables, we produce riverscape metrics that begin to explore how geomorphic structures may influence river habitats, including connectivity, patchiness of habitat, and habitat distributions. The results show a complex interplay of geomorphic variable and habitat patchiness that is not predicted by existing fluvial theory. Riverscapes, thus, challenge the existing understanding of how rivers structure themselves and will force development of new paradigms.

Open-water and under-ice seasonal variations in trace element content and physicochemical associations in fluvial bed sediment.

PubMed

Doig, Lorne E; Carr, Meghan K; Meissner, Anna G N; Jardine, Tim D; Jones, Paul D; Bharadwaj, Lalita; Lindenschmidt, Karl-Erich

2017-11-01

Across the circumpolar world, intensive anthropogenic activities in the southern reaches of many large, northward-flowing rivers can cause sediment contamination in the downstream depositional environment. The influence of ice cover on concentrations of inorganic contaminants in bed sediment (i.e., sediment quality) is unknown in these rivers, where winter is the dominant season. A geomorphic response unit approach was used to select hydraulically diverse sampling sites across a northern test-case system, the Slave River and delta (Northwest Territories, Canada). Surface sediment samples (top 1 cm) were collected from 6 predefined geomorphic response units (12 sites) to assess the relationships between bed sediment physicochemistry (particle size distribution and total organic carbon content) and trace element content (mercury and 18 other trace elements) during open-water conditions. A subset of sites was resampled under-ice to assess the influence of season on these relationships and on total trace element content. Concentrations of the majority of trace elements were strongly correlated with percent fines and proxies for grain size (aluminum and iron), with similar trace element grain size/grain size proxy relationships between seasons. However, finer materials were deposited under ice with associated increases in sediment total organic carbon content and the concentrations of most trace elements investigated. The geomorphic response unit approach was effective at identifying diverse hydrological environments for sampling prior to field operations. Our data demonstrate the need for under-ice sampling to confirm year-round consistency in trace element-geochemical relationships in fluvial systems and to define the upper extremes of these relationships. Whether contaminated or not, under-ice bed sediment can represent a "worst-case" scenario in terms of trace element concentrations and exposure for sediment-associated organisms in northern fluvial systems. Environ Toxicol Chem 2017;36:2916-2924. © 2017 SETAC. © 2017 SETAC.

Ecoregions and stream morphology in eastern Oklahoma

USGS Publications Warehouse

Splinter, D.K.; Dauwalter, D.C.; Marston, R.A.; Fisher, W.L.

2010-01-01

Broad-scale variables (i.e., geology, topography, climate, land use, vegetation, and soils) influence channel morphology. How and to what extent the longitudinal pattern of channel morphology is influenced by broad-scale variables is important to fluvial geomorphologists and stream ecologists. In the last couple of decades, there has been an increase in the amount of interdisciplinary research between fluvial geomorphologists and stream ecologists. In a historical context, fluvial geomorphologists are more apt to use physiographic regions to distinguish broad-scale variables, while stream ecologists are more apt to use the concept of an ecosystem to address the broad-scale variables that influence stream habitat. For this reason, we designed a study using ecoregions, which uses physical and biological variables to understand how landscapes influence channel processes. Ecoregions are delineated by similarities in geology, climate, soils, land use, and potential natural vegetation. In the fluvial system, stream form and function are dictated by processes observed throughout the fluvial hierarchy. Recognizing that stream form and function should differ by ecoregion, a study was designed to evaluate how the characteristics of stream channels differed longitudinally among three ecoregions in eastern Oklahoma, USA: Boston Mountains, Ozark Highlands, and Ouachita Mountains. Channel morphology of 149 stream reaches was surveyed in 1st- through 4th-order streams, and effects of drainage area and ecoregion on channel morphology was evaluated using multiple regressions. Differences existed (?????0.05) among ecoregions for particle size, bankfull width, and width/depth ratio. No differences existed among ecoregions for gradient or sinuosity. Particle size was smallest in the Ozark Highlands and largest in the Ouachita Mountains. Bankfull width was larger in the Ozark Highlands than in the Boston Mountains and Ouachita Mountains in larger streams. Width/depth ratios of the Boston Mountains and Ozark Highlands were not statistically different. Significant differences existed, however, between the Boston Mountains and Ozark Highlands when compared individually to the Ouachita Mountains. We found that ecoregions afforded a good spatial structure that can help in understanding longitudinal trends in stream reach morphology surveyed at the reach scale. The hierarchy of the fluvial system begins within a broad, relatively homogenous setting that imparts control on processes that affect stream function. Ecoregions provide an adequate regional division to begin a large-scale geomorphic study of processes in stream channels. ?? 2010 Elsevier B.V.

Kasei Vallis of Mars: Dating the Interplay of Tectonics and Geomorphology

NASA Technical Reports Server (NTRS)

Wise, D. U.

1985-01-01

Crater density age dates on more than 250 small geomorphic surfaces in the Kasei Region of Mars show clusterings indicative of times of peak geomorphic and tectonic activity. Kasei Vallis is part of a 300 km wide channel system breaching a N-S trending ancient basement high (+50,000 crater age) separating the Chryse Basin from the Tharsis Volcanic Province of Mars. The basement high was covered by a least 3 groups of probable volcanic deposits. Major regional fracturing took place at age 4,000 to 5,000 and was immediately followed by deposition of regional volcanics of the Fesenkov Plains (age 3,000 to 4,200). Younger clusterings of dates in the 900 to 1,500 and 500 to 700 range represent only minor modification of the basic tectonic geomorphic landform. The data suggest that Kasei gap is a structurally controlled breach of a buried ridge by a rather brief episode of fluvial activity.

Impact erosion of the primordial atmosphere of Mars.

PubMed

Melosh, H J; Vickery, A M

1989-04-06

Abundant geomorphic evidence for fluvial processes on the surface of Mars suggests that during the era of heavy bombardment, Mars's atmospheric pressure was high enough for liquid water to flow on the surface. Many authors have proposed mechanisms by which Mars could have lost (or sequestered) an earlier, thicker atmosphere but none of these proposals has gained general acceptance. Here we examine the process of atmospheric erosion by impacts and show that it may account for an early episode of atmosphere loss from Mars. On the basis of this model, the primordial atmospheric pressure on Mars must have been in the vicinity of 1 bar, barring other sources or sinks of CO2. Current impact fluxes are too small to erode significantly the present martian atmosphere.

Geomorphic Response to Spatial and Temporal Tectonic uplift on the Kenya Rift of East African Rift System

NASA Astrophysics Data System (ADS)

Xue, L.; Abdelsalam, M. G.

2017-12-01

Tectonic uplifts of the shoulders of the East Africa Rift System (EARS) have significant impact on the geological record by reorganizing drainage systems, increasing sediment supply, and changing climate and biogeography. Recent studies in geochronology, geomorphology and geophysics have provided some understanding of the timing of tectonic uplift and its distribution pattern of the (EARS). We do not know how the vertical motion is localized along the rift axis and the relative roles of upwelling of magma and rift extensional processes play in tectonic uplift history. This work presents detailed morphometric study of the fluvial landscape response to the tectonic uplift and climate shifting of the Kenya Rift shoulders in order to reconstruct their incision history, with special attention to timing, location, and intensity of uplift episodes. This work compiles the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) and Sentinel-2A data, summarized previous 39Ar-40Ar and thermochronology data, and calculates long-term incision rate and geomorphic proxies (normalized steepness and chi-integral) along the Kenya Rift. It also models the age of tectonic/climatic events by using knickpoint celerity model and R/SR integrative approach. It found that the maximum long-term incision rates of 300 mm/kyr to be at the central Kenya Rift, possibly related to the mantle-driven process and rapid tectonic uplift. The geomorphic proxies indicate southward decreasing pattern of the short-term incision rate, possibly related to the migration of the mantle plume.

Early Mars: A regional assessment of denudation chronology

NASA Technical Reports Server (NTRS)

Maxwell, T. A.; Craddock, R. A.

1993-01-01

Within the oldest highland units on Mars, the record of crater degradation indicates that fluvial resurfacing was responsible for modifying the Noachian through middle-Hesperian crater population. Based on crater frequency in the Noachian cratered terrain, age/elevation relations suggest that the highest exposures of Noachian dissected and plateau units became stabilized first, followed by successively lower units. In addition, studies of drainage networks indicate that the frequency of Noachian channels is greatest at high elevations. Together, these observations provide strong evidence of atmospheric involvement in volatile recycling. The long time period of crater modification also suggests that dendritic highland drainage was not simply the result of sapping by release of juvenile water, because the varied geologic units as well as the elevation dependence of stability ages makes it unlikely that subsurface recycling could provide a continuous supply of water for channel formation by sapping. While such geomorphic constraints on volatile history have been established by crater counts and stratigraphic relations using the 1:2M photomosaic series, photogeologic age relationships at the detailed level are needed to establish a specific chronology of erosion and sedimentation. Age relations for discrete erosional slopes and depositional basins will help refine ages of fluvial degradation, assess effectiveness of aeolian processes, and provide a regional chronology of fluvial events.

Computer Simulations of Deltas with Varying Fluvial Input and Tidal Forcing

NASA Astrophysics Data System (ADS)

Sun, T.

2015-12-01

Deltas are important depositional systems because many large hydrocarbon reservoirs in the world today are found in delta deposits. Deltas form when water and sediments carried by fluvial channels are emptied to an open body of water, and form delta shaped deposits. Depending on the relative importance of the physical processes that controls the forming and the growth of deltas, deltas can often be classified into three different types, namely fluvial, tidal and wave dominated delta. Many previous works, using examples from modern systems, tank experiments, outcrops, and 2 and 3D seismic data sets, have studied the shape, morphology and stratigraphic architectures corresponding to each of the deltas' types. However, few studies have focused on the change of these properties as a function of the relative change of the key controls, and most of the studies are qualitative. Here, using computer simulations, the dynamics of delta evolutions under an increasing amount of tidal influences are studied. The computer model used is fully based on the physics of fluid flow and sediment transport. In the model, tidal influences are taken into account by setting proper boundary conditions that varies both temporally and spatially. The model is capable of capturing many important natural geomorphic and sedimentary processes in fluvial and tidal systems, such as channel initiation, formation of channel levees, growth of mouth bars, bifurcation of channels around channel mouth bars, and channel avulsion. By systematically varying tidal range and fluvial input, the following properties are investigated quantitatively: (1) the presence and the form of tidal beds as a function of tidal range, (2) change of stratigraphic architecture of distributary channel mouth bars or tidal bars as tidal range changes, (3) the transport and sorting of different grainsizes and the overall facie distributions in the delta with different tidal ranges, and (4) the conditions and locations of mud drapes with different magnitude of tidal forcing.

On modeling the organization of landscapes and vegetation patterns controlled by solar radiation

NASA Astrophysics Data System (ADS)

Istanbulluoglu, E.; Yetemen, O.

2014-12-01

Solar radiation is a critical driver of ecohydrologic processes and vegetation dynamics. Patterns of runoff generation and vegetation dictate landscape geomorphic response. Distinct patterns in the organization of soil moisture, vegetation type, and landscape morphology have been documented in close relation to aspect in a range of climates. Within catchments, from north to south facing slopes, studies have shown ecotone shifts from forest to shrub species, and steep diffusion-dominated landforms to fluvial landforms. Over the long term differential evolution of ecohydrology and geomorphology leads to observed asymmetric structure in the planform of channel network and valley morphology. In this talk we present examples of coupled modeling of ecohydrology and geomorphology driven by solar radiation. In a cellular automata model of vegetation dynamics we will first show how plants organize in north and south facing slopes and how biodiversity changes with elevation. When vegetation-erosion feedbacks are coupled emergent properties of the coupled system are observed in the modeled elevation and vegetation fields. Integrating processes at a range of temporal and spatial scales, coupled models of ecohydrologic and geomorphic dynamics enable examination of global change impacts on landscapes and ecosystems.

Scaling Laws in Arctic Permafrost River Basins: Statistical Signature in Transition

NASA Astrophysics Data System (ADS)

Rowland, J. C.; Gangodagamage, C.; Wilson, C. J.; Prancevic, J. P.; Brumby, S. P.; Marsh, P.; Crosby, B. T.

2011-12-01

The Arctic landscape has been shown to be fundamentally different from the temperate landscape in many ways. Long winters and cold temperatures have led to the development of permafrost, perennially frozen ground, that controls geomorphic processes and the structure of the Arctic landscape. Climate warming is causing changes in permafrost and the active layer (the seasonally thawed surface layer) that is driving an increase in thermal erosion including thermokarst (collapsed soil), retrogressive thaw slumps, and gullies. These geomorphic anomalies in the arctic landscapes have not been well quantified, even though some of the landscape geomorphic and hydrologic characteristics and changes are detectable by our existing sensor networks. We currently lack understanding of the fundamental fluvio-thermal-erosional processes that underpin Arctic landscape structure and form, which limits our ability to develop models to predict the landscape response to current and future climate change. In this work, we seek a unified framework that can explain why permafrost landscapes are different from temperate landscapes. We use high resolution LIDAR data to analyze arctic geomorphic processes at a scale of less than a 1 m and demonstrate our ability to quantify the fundamental difference in the arctic landscape. We first simulate the arctic hillslopes from a stochastic space-filling network and demonstrate that the flow-path convergent properties of arctic landscape can be effectively captured from this simple model, where the simple model represents a landscape flowpath arrangement on a relatively impervious frozen soil layer. Further, we use a novel data processing algorithm to analyze landscape attributes such as slope, curvature, flow-accumulation, elevation-drops and other geomorphic properties, and show that the pattern of diffusion and advection dominated soil transport processes (diffusion/advection regime transition) in the arctic landscape is substantially different from the pattern in temperate landscapes. Our results suggest that Arctic landscapes are characterized by relatively undissected, long planar hillslopes, which convey sediment to quasi-fluvial valleys through long (~ 1 km) flow-paths. Further, we also document that broad planar hillslopes abruptly converge, forcing rapid subsurface flow accumulation at channel heads. This topographic characteristic can successfully be used to explain the position of erosion features. Finally we estimate the landscape model parameters for the arctic landscape that can be successfully used to model development and validation purposes.

Active shortening, intermontane basin formation, and geomorphic evolution in an orogenic plateau: Central Puna Plateau, NW Argentina (24°37'S, 67°03'W)

NASA Astrophysics Data System (ADS)

Strecker, Manfred R.; Alonso, Ricardo N.; Bookhagen, Bodo; Freymark, Jessica; Pingel, Heiko

2017-04-01

The high-elevation Andean Plateau (Altiplano-Puna; 4km) is a first-order morphotectonic province of the Central Andes and constitutes the world's second largest orogenic plateau. While there are many unifying basin characteristics in this region, including internal drainage, semi-arid to arid climate and associated deposition of evaporites, there are notable differences between the northern and southern parts of the plateau. In contrast to the vast basins of the Altiplano (north) and incipient establishment of fluvial connectivity and sediment transport to the foreland, the Puna (south) comprises numerous smaller basins, bordered by reverse-fault bounded ranges up to 6 km high. The plateau is internally drained and fluvial connectivity with the foreland does not exist leading to thick sedimentary basin fills that comprise continental evaporites, volcanic and clastic deposits, typically between 3 and 5 km thick. However, repeated impacts of climate change and superposed tectonic activity in the southern plateau have resulted in further basin differentiation, abandonment or re-arrangement of fluvial networks and impacts on sediment transport. Here we report evidence for sustained contractional tectonic activity in the Pocitos Basin in the southern plateau. On the western margin of the basin fanning of dipping strata and regraded, steeply inclined gravel-covered pediment surfaces and wind gaps associated with gravel derived from distant sources in the west document late Tertiary to Pleistocene growth of an approximately N-S oriented and N plunging anticline. The growth of the eastern limb of this anticline has caused the isolation of a formerly more extensive basin. In addition, Late Pleistocene and Holocene lake shorelines and lacustrine deposits are tilted eastward along the same structure and InSAR measurements of deformed lake terraces document that the fold is growing. Despite widely reported extensional faulting in the southern Puna, we conclude (1) that the central sectors of the plateau are deformed by active shortening, suggesting that the kinematic changeover from shortening to neotectonic extension on the plateau must be highly disparate in space and time; (2) sustained deformation within the plateau results in a high degree of basin compartmentalization, which impacts the fluvial network and re-distribution of sediments, leading to similar geomorphic and sedimentary processes, although highly disparate in space and time.

Immediate propagation of deglacial environmental change to deep-marine turbidite systems along the Chile convergent margin

NASA Astrophysics Data System (ADS)

Bernhardt, Anne; Schwanghart, Wolfgang; Hebbeln, Dierk; Stuut, Jan-Berend W.; Strecker, Manfred R.

2017-09-01

Understanding how Earth-surface processes respond to past climatic perturbations is crucial for making informed predictions about future impacts of climate change on sediment fluxes. Sedimentary records provide the archives for inferring these processes, but their interpretation is compromised by our incomplete understanding of how sediment-routing systems respond to millennial-scale climate cycles. We analyzed seven sediment cores recovered from marine turbidite depositional sites along the Chile continental margin. The sites span a pronounced arid-to-humid gradient with variable relief and related sediment connectivity of terrestrial and marine environments. These sites allowed us to study event-related depositional processes in different climatic and geomorphic settings from the Last Glacial Maximum to the present day. The three sites reveal a steep decline of turbidite deposition during deglaciation. High rates of sea-level rise postdate the decline in turbidite deposition. Comparison with paleoclimate proxies documents that the spatio-temporal sedimentary pattern rather mirrors the deglacial humidity decrease and concomitant warming with no resolvable lag times. Our results let us infer that declining deglacial humidity decreased fluvial sediment supply. This signal propagated rapidly through the highly connected systems into the marine sink in north-central Chile. In contrast, in south-central Chile, connectivity between the Andean erosional zone and the fluvial transfer zone probably decreased abruptly by sediment trapping in piedmont lakes related to deglaciation, resulting in a sudden decrease of sediment supply to the ocean. Additionally, reduced moisture supply may have contributed to the rapid decline of turbidite deposition. These different causes result in similar depositional patterns in the marine sinks. We conclude that turbiditic strata may constitute reliable recorders of climate change across a wide range of climatic zones and geomorphic conditions. However, the underlying causes for similar signal manifestations in the sinks may differ, ranging from maintained high system connectivity to abrupt connectivity loss.

Pollutant fates in fluvial systems: on need of individual approach to each case study

NASA Astrophysics Data System (ADS)

Matys Grygar, Tomas; Elznicova, Jitka; Novakova, Tereza

2015-04-01

To outline the pollutant fates in fluvial systems it is necessary to combine two main kinds of knowledge: sedimentation and erosion patterns of each individual river with spatio-temporal resolution higher than in most fluvial geomorphology/sedimentology studies and timing and way how the pollutants have entered the fluvial system. Most of these aspects are commonly neglected in environmental geochemistry, a domain to which pollution studies apparently belong. In fact, only when these two main components are established (at least in a qualitative manner), we can start reading (interpretation) of the fluvial sedimentary archives, e.g., decipher the way how the primary pollution signal has been distorted during passing through the fluvial system. We conducted empirical studies on Czech rivers impacted by pollution (by risk elements). We learnt how individual (site-specific) are the main processes responsible for the primary pollution input, spread through each fluvial system and inevitable secondary pollution ("lagged pollution improvement signal"). We will discuss main features of the story on pollutant fates in three different fluvial systems, which have not been impacted by "hard" river engineering and still undergo natural fluvial processes: 1. the Ohre (the Eger) impacted by production of Hg and its compounds, historical mining of Pb and more recent U ore processing, 2. the Ploucnice impacted by U mining, and 3. the Litavka, impacted by Pb-Zn(-Sb) mining and smelting. The Ohre is specific by most pollution having been temporarily deposited in an active channel, only minor reworking of older fluvial deposits diluting pollution during downstream transport, and pollution archives existing practically only in the form of lateral accretion deposits. The deposits of archive value are rare and can be revealed by detailed study of historical maps and well-planned field analysis, best using portable analytical instruments (XRF). The Ploucnice is specific by only transient deposition in a channel belt and subsequent secondary pollution via physical mobilisation, most pollution storing in the floodplain in a surprisingly heterogeneous manner - in hotspots with a size comparable to fragments of abandoned channels (from a few to few tens of metres). The hotspots are hence best revealed by well-designed field analysis using portable instruments (gamma spectrometry or XRF). The Litavka is specific because most pollution is in its floodplain in the form of anthropogenic alluvium, a very thick vertical accretion body of "artificial" material added to the river system in the amount exceeding its normal transport capacity. That situation favours secondary pollution by chemical mobilisation of pollutants under low river discharges revealed by geochemical analysis. Our case studies show that simple "rules" such as continuous decay of pollutant concentrations downstream from the pollution source, existence of a continuous blanket of polluted overbank fines in floodplain, simple change of the pollution extent with growing distance from the river channel and as a consequence of extreme floods, or simple recipes such as low-density sampling to trace point pollution sources are too simplistic to be applicable in real polluted fluvial systems. Each river system represents a nearly unique combination of individual geomorphic processes, and each pollution has been specific by the mode how it entered the fluvial system. We will not offer "magic tools" in our contribution. In literature we can find all pieces we need for the jigsaw puzzle - pollutants fates in fluvial systems. The question is why so rarely researchers put them together. We would like to encourage them to do so.

Vegetation and substrate properties of aeolian dune fields in the Colorado River corridor, Grand Canyon, Arizona

USGS Publications Warehouse

Draut, Amy E.

2011-01-01

This report summarizes vegetation and substrate properties of aeolian landscapes in the Colorado River corridor through Grand Canyon, Arizona, in Grand Canyon National Park. Characterizing these parameters provides a basis from which to assess future changes in this ecosystem, including the spread of nonnative plant species. Differences are apparent between aeolian dune fields that are downwind of where modern controlled flooding deposits new sandbars (modern-fluvial-sourced dune fields) and those that have received little or no new windblown sand since river regulation began in the 1960s (relict-fluvial-sourced dune fields). The most substantial difference between modern- and relict-fluvial-sourced aeolian dune fields is the greater abundance of biologic soil crust in relict dune fields. These findings can be used with similar investigations in other geomorphic settings in Grand Canyon and elsewhere in the Colorado River corridor to evaluate the health of the Colorado River ecosystem over time.

Synthetic river valleys: Creating prescribed topography for form-process inquiry and river rehabilitation design

NASA Astrophysics Data System (ADS)

Brown, R. A.; Pasternack, G. B.; Wallender, W. W.

2014-06-01

The synthesis of artificial landforms is complementary to geomorphic analysis because it affords a reflection on both the characteristics and intrinsic formative processes of real world conditions. Moreover, the applied terminus of geomorphic theory is commonly manifested in the engineering and rehabilitation of riverine landforms where the goal is to create specific processes associated with specific morphology. To date, the synthesis of river topography has been explored outside of geomorphology through artistic renderings, computer science applications, and river rehabilitation design; while within geomorphology it has been explored using morphodynamic modeling, such as one-dimensional simulation of river reach profiles, two-dimensional simulation of river networks, and three-dimensional simulation of subreach scale river morphology. To date, no approach allows geomorphologists, engineers, or river rehabilitation practitioners to create landforms of prescribed conditions. In this paper a method for creating topography of synthetic river valleys is introduced that utilizes a theoretical framework that draws from fluvial geomorphology, computer science, and geometric modeling. Such a method would be valuable to geomorphologists in understanding form-process linkages as well as to engineers and river rehabilitation practitioners in developing design surfaces that can be rapidly iterated. The method introduced herein relies on the discretization of river valley topography into geometric elements associated with overlapping and orthogonal two-dimensional planes such as the planform, profile, and cross section that are represented by mathematical functions, termed geometric element equations. Topographic surfaces can be parameterized independently or dependently using a geomorphic covariance structure between the spatial series of geometric element equations. To illustrate the approach and overall model flexibility examples are provided that are associated with mountain, lowland, and hybrid synthetic river valleys. To conclude, recommended advances such as multithread channels are discussed along with potential applications.

Valley-scale morphology drives differences in fluvial sediment budgets and incision rates during contrasting flow regimes

NASA Astrophysics Data System (ADS)

Weber, M. D.; Pasternack, G. B.

2017-07-01

High-resolution topographic surveys using LiDAR and multibeam sonar can be used to characterize and quantify fluvial change. This study used repeat surveys to explore how topographic change, fluvial processes, sediment budgets, and aggradation and incision rates vary across spatial scales and across two contrasting decadal flow regimes in a regulated gravel/cobble river. A novel method for quantifying digital elevation model uncertainty was developed and applied to a topographic change detection analysis from 2006/2008 to 2014. During this period, which had four modest 3-5 year floods, most sediment was laterally redistributed through bank erosion and channel migration. Erosion primarily occurred in the floodplain (97,000 m3), terraces (80,000 m3), and lateral bars (58,000 m3); while deposition occurred in the adjacent pools (73,000 m3), fast glides (48,000 m3), and runs (36,000 m3). In contrast, significantly higher magnitude and longer duration floods from 1999 to 2006/2008 caused sediment to be displaced longitudinally, with the upstream reaches exporting sediment and the downstream reaches aggrading. The river maintained floodplain connectivity during both periods, despite different processes dominating the type of connectivity. Larger floods promoted overbank scour and avulsion, while smaller floods promoted bank erosion and lateral migration. This study explores and illustrates how the geomorphic response to contrasting flood regimes in a nonuniform river is highly dependent on which landforms are controlling hydraulics.

Geomorphic effectiveness of long profile shape and role of inherent geological controls, Ganga River Basin, India

NASA Astrophysics Data System (ADS)

Sonam, Sonam; Jain, Vikrant

2017-04-01

River long profile is one of the fundamental geomorphic parameters which provides a platform to study interaction of geological and geomorphic processes at different time scales. Long profile shape is governed by geological processes at 10 ^ 5 - 10 ^ 6 years' time scale and it controls the modern day (10 ^ 0 - 10 ^ 1 years' time scale) fluvial processes by controlling the spatial variability of channel slope. Identification of an appropriate model for river long profile may provide a tool to analyse the quantitative relationship between basin geology, profile shape and its geomorphic effectiveness. A systematic analysis of long profiles has been carried for the Himalayan tributaries of the Ganga River basin. Long profile shape and stream power distribution pattern is derived using SRTM DEM data (90 m spatial resolution). Peak discharge data from 34 stations is used for hydrological analysis. Lithological variability and major thrusts are marked along the river long profile. The best fit of long profile is analysed for power, logarithmic and exponential function. Second order exponential function provides the best representation of long profiles. The second order exponential equation is Z = K1*exp(-β1*L) + K2*exp(-β2*L), where Z is elevation of channel long profile, L is the length, K and β are coefficients of the exponential function. K1 and K2 are the proportion of elevation change of the long profile represented by β1 (fast) and β2 (slow) decay coefficients of the river long profile. Different values of coefficients express the variability in long profile shapes and is related with the litho-tectonic variability of the study area. Channel slope of long profile is estimated taking the derivative of exponential function. Stream power distribution pattern along long profile is estimated by superimposing the discharge and long profile slope. Sensitivity analysis of stream power distribution with decay coefficients of the second order exponential equation is evaluated for a range of coefficient values. Our analysis suggests that the amplitude of stream power peak value is dependent on K1, the proportion of elevation change coming under the fast decay exponent and the location of stream power peak is dependent of the long profile decay coefficient (β1). Different long profile shapes owing to litho-tectonic variability across the Himalayas are responsible for spatial variability of stream power distribution pattern. Most of the stream power peaks lie in the Higher Himalaya. In general, eastern rivers have higher stream power in hinterland area and low stream power in the alluvial plains. This is responsible for, 1) higher erosion rate and sediment supply in hinterland of eastern rivers, 2) the incised and stable nature of channels in the western alluvial plains and 3) aggrading channels with dynamic nature in the eastern alluvial plains. Our study shows that the spatial variability of litho-units defines the coefficients of long profile function which in turn controls the position and magnitude of stream power maxima and hence the geomorphic variability in a fluvial system.

Geomorphic Processes and Remote Sensing Signatures of Alluvial Fans in the Kun Lun Mountains, China

NASA Technical Reports Server (NTRS)

Farr, Tom G.; Chadwick, Oliver A.

1996-01-01

The timing of alluvial deposition in arid and semiarid areas is tied to land-surface instability caused by regional climate changes. The distribution pattern of dated deposits provides maps of regional land-surface response to past climate change. Sensitivity to differences in surface roughness and composition makes remote sensing techniques useful for regional mapping of alluvial deposits. Radar images from the Spaceborne Radar Laboratory and visible wavelength images from the French SPOT satellite were used to determine remote sensing signatures of alluvial fan units for an area in the Kun Lun Mountains of northwestern China. These data were combined with field observations to compare surface processes and their effects on remote sensing signatures in northwestern China and the southwestern United States. Geomorphic processes affecting alluvial fans in the two areas include aeolian deposition, desert varnish, and fluvial dissection. However, salt weathering is a much more important process in the Kun Lun than in the southwestern United States. This slows the formation of desert varnish and prevents desert pavement from forming. Thus the Kun Lun signatures are characteristic of the dominance of salt weathering, while signatures from the southwestern United States are characteristic of the dominance of desert varnish and pavement processes. Remote sensing signatures are consistent enough in these two regions to be used for mapping fan units over large areas.

The mid-Holocene to present large-scale morphodynamic and coupled fluvial-tidal sedimentologic evolution of the Lower Columbia River, WA/OR, USA

NASA Astrophysics Data System (ADS)

Prokocki, E.; Best, J.; Ashworth, P. J.; Parsons, D. R.; Sambrook Smith, G.; Nicholas, A. P.; Simpson, C.; Wang, H.; Sandbach, S.; Keevil, C.

2015-12-01

Optically stimulated luminescence (OSL) dating of four deep sediment cores (≤ 20m depth), in conjunction with shallow vibracores (≤ 6m depth), obtained from mid-channel bars in the lower Columbia River (LCR), USA, provides new insights into the mid-Holocene to present geomorphic and coupled sedimentological evolution of the LCR fluvial-tidal zone. These data reveal that the relatively coarse-grained basal sediments of mid-channel bars positioned across the LCR tidal-fluvial hydraulic regime were deposited at c. 2.5 to 2.0 ka, and not at c. 8.0 ka as previously reported. Thus, these younger depositional ages of basal sediments relative to previous studies coupled with the overall sedimentary architecture of these bars, and the absence of a temporal lag in the timing of basal sedimentation between bars located from river kilometer 51.1 to 29.3, challenges existing models that these bars represent: (a) estuarine tidal-bars, or (b) bay-head deltaic deposits. Within the context of post glacial Holocene sea-level rise, our results suggest these bars represent vertical construction of a LCR fluvial top-set from c. 2.5- 2.0 ka to the present, as the regional rate of sea-level rise slowed to ≤ 1.4 mmyr-1. Within this geomorphic context, two tidal-fluvial sedimentological signatures can be identified: (i) in the downstream direction, basal bar deposits incorporate a larger percentage of finer-grained interbeds, and (ii) vertically stacked silt/very-fine sand draped current ripple cross-laminae become prevalent from approximately 5 m in depth to the bar surfaces. The preservation of finer-grained interbeds within basal bar deposits is reasoned to be caused by the flocculation and settling of suspended sediment enhanced by the turbidity maximum. The stacked draped current ripple cross-laminae are interpreted to result from tidal-currents generating asymmetric current ripples that were draped by fine-sediment entrained by wind-waves, which fell-out of suspension during reduced wave activity, slackwater intervals, and periods when the turbidity maximum was active.

Neogeomorphology, prediction, and the anthropic landscape

NASA Astrophysics Data System (ADS)

Haff, P. K.

The surface of the earth is undergoing profound change due to human impact. By some measures the level of human impact is comparable to the effects of major classical geomorphic processes such as fluvial sediment transport. This change is occurring rapidly, has no geologic precedent, and may represent an irreversible transition to a new and novel landscape with which we have no experience. For these reasons prediction of future landscape evolution will be of increasing importance. The combination of physical and social forces that drive modern landscape change represents the Anthropic Force. Neogeomorphology is the study of the Anthropic Force and its present and likely future effects on the landscape. Unique properties associated with the Anthropic Force include consciousness, intention and design. These properties support the occurrence of nonclassical geomorphic phenomena, such as landscape planning, engineering, and management. The occurrence of short time-scale phenomena induced by anthropic landscape change, the direct effects of this change on society, and the ability to anticipate and intentionally influence the future trajectory of the global landscape underscore the importance of prediction in a neogeomorphic world.

Characterizing Feedbacks Between Environmental Forcing and Sediment Characteristics in Fluvial and Coastal Systems

NASA Astrophysics Data System (ADS)

Feehan, S.; Ruggiero, P.; Hempel, L. A.; Anderson, D. L.; Cohn, N.

2016-12-01

Characterizing Feedbacks Between Environmental Forcing and Sediment Characteristics in Fluvial and Coastal Systems American Geophysical Union, 2016 Fall Meeting: San Francisco, CA Authors: Scott Feehan, Peter Ruggiero, Laura Hempel, and Dylan Anderson Linking transport processes and sediment characteristics within different environments along the source to sink continuum provides critical insight into the dominant feedbacks between grain size distributions and morphological evolution. This research is focused on evaluating differences in sediment size distributions across both fluvial and coastal environments in the U.S. Pacific Northwest. The Cascades' high relief is characterized by diverse flow regimes with high peak/flashy flows and sub-threshold flows occurring in relative proximity and one of the most energetic wave climates in the world. Combining analyses of both fluvial and coastal environments provides a broader understanding of the dominant forces driving differences between each system's grain size distributions, sediment transport processes, and resultant evolution. We consider sediment samples taken during a large-scale flume experiment that simulated floods representative of both high/flashy peak flows analogous to runoff dominated rivers and sub-threshold flows, analogous to spring-fed rivers. High discharge flows resulted in narrower grain size distributions while low flows where less skewed. Relative sediment size showed clear dependence on distance from source and the environments' dominant fluid motion. Grain size distributions and sediment transport rates were also quantified in both wave dominated nearshore and aeolian dominated backshore portions of Long Beach Peninsula, Washington during SEDEX2, the Sandbar-aEolian-Dune EXchange Experiment of summer 2016. The distributions showed spatial patterns in mean grain size, skewness, and kurtosis dependent on the dominant sediment transport process. The feedback between these grain size distributions and the predominant driver of sediment transport controls the potential for geomorphic change on societally relevant time scales in multiple settings.

The response of source-bordering aeolian dunefields to sediment-supply changes 1: Effects of wind variability and river-valley morphodynamics

USGS Publications Warehouse

Sankey, Joel B.; Kasprak, Alan; Caster, Joshua; East, Amy; Fairley, Helen C.

2018-01-01

Source-bordering dunefields (SBDs), which are primarily built and maintained with river-derived sediment, are found in many large river valleys and are currently impacted by changes in sediment supply due to climate change, land use changes, and river regulation. Despite their importance, a physically based, applied approach for quantifying the response of SBDs to changes in sediment supply does not exist. To address this knowledge gap, here we develop an approach for quantifying the geomorphic responses to sediment-supply alteration based on the interpretation of dunefield morphodynamics from geomorphic change detection and wind characteristics. We use the approach to test hypotheses about the response of individual dunefields to variability in sediment supply at three SBDs along the Colorado River in Grand Canyon, Arizona, USA during the 11 years between 2002 and 2013 when several river floods rebuilt some river sandbars and channel margin deposits that serve as sediment source areas for the SBDs. We demonstrate that resupply of fluvially sourced aeolian sediment occurred at one of the SBDs, but not at the other two, and attribute this differential response to site-specific variability in geomorphology, wind, and sediment source areas. The approach we present is applied in a companion study to shorter time periods with high-resolution topographic data that bracket individual floods in order to infer the resupply of fluvially sourced aeolian sediment to SBDs by managed river flows. Such an applied methodology could also be useful for measuring sediment connectivity and anthropogenic alterations of connectivity in other coupled fluvial-aeolian environments.

The response of source-bordering aeolian dunefields to sediment-supply changes 1: Effects of wind variability and river-valley morphodynamics

NASA Astrophysics Data System (ADS)

Sankey, Joel B.; Kasprak, Alan; Caster, Joshua; East, Amy E.; Fairley, Helen C.

2018-06-01

Source-bordering dunefields (SBDs), which are primarily built and maintained with river-derived sediment, are found in many large river valleys and are currently impacted by changes in sediment supply due to climate change, land use changes, and river regulation. Despite their importance, a physically based, applied approach for quantifying the response of SBDs to changes in sediment supply does not exist. To address this knowledge gap, here we develop an approach for quantifying the geomorphic responses to sediment-supply alteration based on the interpretation of dunefield morphodynamics from geomorphic change detection and wind characteristics. We use the approach to test hypotheses about the response of individual dunefields to variability in sediment supply at three SBDs along the Colorado River in Grand Canyon, Arizona, USA during the 11 years between 2002 and 2013 when several river floods rebuilt some river sandbars and channel margin deposits that serve as sediment source areas for the SBDs. We demonstrate that resupply of fluvially sourced aeolian sediment occurred at one of the SBDs, but not at the other two, and attribute this differential response to site-specific variability in geomorphology, wind, and sediment source areas. The approach we present is applied in a companion study to shorter time periods with high-resolution topographic data that bracket individual floods in order to infer the resupply of fluvially sourced aeolian sediment to SBDs by managed river flows. Such an applied methodology could also be useful for measuring sediment connectivity and anthropogenic alterations of connectivity in other coupled fluvial-aeolian environments.

Columbia River Estuary ecosystem classification—Concept and application

USGS Publications Warehouse

Simenstad, Charles A.; Burke, Jennifer L.; O'Connor, Jim E.; Cannon, Charles; Heatwole, Danelle W.; Ramirez, Mary F.; Waite, Ian R.; Counihan, Timothy D.; Jones, Krista L.

2011-01-01

This document describes the concept, organization, and application of a hierarchical ecosystem classification that integrates saline and tidal freshwater reaches of estuaries in order to characterize the ecosystems of large flood plain rivers that are strongly influenced by riverine and estuarine hydrology. We illustrate the classification by applying it to the Columbia River estuary (Oregon-Washington, USA), a system that extends about 233 river kilometers (rkm) inland from the Pacific Ocean. More than three-quarters of this length is tidal freshwater. The Columbia River Estuary Ecosystem Classification ("Classification") is based on six hierarchical levels, progressing from the coarsest, regional scale to the finest, localized scale: (1) Ecosystem Province; (2) Ecoregion; (3) Hydrogeomorphic Reach; (4) Ecosystem Complex; (5) Geomorphic Catena; and (6) Primary Cover Class. We define and map Levels 1-3 for the entire Columbia River estuary with existing geospatial datasets, and provide examples of Levels 4-6 for one hydrogeomorphic reach. In particular, three levels of the Classification capture the scales and categories of ecosystem structure and processes that are most tractable to estuarine research, monitoring, and management. These three levels are the (1) eight hydrogeomorphic reaches that embody the formative geologic and tectonic processes that created the existing estuarine landscape and encompass the influence of the resulting physiography on interactions between fluvial and tidal hydrology and geomorphology across 230 kilometers (km) of estuary, (2) more than 15 ecosystem complexes composed of broad landforms created predominantly by geologic processes during the Holocene, and (3) more than 25 geomorphic catenae embedded within ecosystem complexes that represent distinct geomorphic landforms, structures, ecosystems, and habitats, and components of the estuarine landscape most likely to change over short time periods.

Geomorphic Parameters for Developing a Hydrologic Model to Infer Holocene Climate Variability, Middle Snake River near Bliss, Idaho

NASA Astrophysics Data System (ADS)

Bullard, T. F.; Bacon, S. N.; Kimball, V. R.

2015-12-01

The geomorphology and stratigraphy preserved in a canyon reach of the Middle Snake River provide model parameter constraints for estimating Holocene paleohydrology. Channel constrictions, which acted as hydraulic weirs throughout the Holocene, were created in this reach by the Bonneville Flood (~17.5 ka) that left very large (>10 m) slabs of basalt and 2-3 m diameter boulder deposits near the canyon floor. Post-Bonneville Flood landforms and deposits that formed during the Holocene are situated less than ~30 m above river level (arl) in this reach and include fluvial and boulder terraces, alluvial fans, and incised tributary alluvial units. Relative topographic position of these geomorphic features, cross-cutting relations, multiple buried soils, depositional and erosional contacts, and radiocarbon dates from terraces (Qt) and alluvial fans provide a geomorphic and stratigraphic framework and a Holocene chronology for this area. The relative stratigraphic position of a massive silty sand that overlies Bonneville Flood gravel in Qt5 (~20 m arl) and Qt4 (~10 m arl) deposits and comprises all of Qt3 (~5 m arl) deposits indicates changes in Holocene discharge; longitudinal profiles of fluvial terraces graded to hydraulic constrictions provide reasonable estimates of paleo-stage. Fifteen radiocarbon dates yielded ages of ~8670 and ~3500 cal yr BP for Qt4 deposits and ~1100 and ~100 cal yr BP for Qt3 deposits and help define periods of episodic cutting and filling. Timing of Qt4 and Qt3 cut-and-fill episodes and alluvial fan formation correlates well with Holocene global and regional paleoclimate events inferred from Great Basin lake histories including wet periods from ~9.0 to 8.0 ka and ~4.2 to 2.5 ka, the Medieval Climatic Anomaly (~1.2 to 0.8 ka), and the Little Ice Age (~0.3 to 0.6 ka). The fluvial geomorphology documented in this study will be used to develop a watershed-scale hydrologic model to infer paleoprecipitation in the region during the Holocene.

Morphotectonic Index Analysis as an Indicator of Neotectonic Segmentation of the Nicoya Peninsula, Costa Rica

NASA Astrophysics Data System (ADS)

Morrish, S.; Marshall, J. S.

2013-12-01

The Nicoya Peninsula lies within the Costa Rican forearc where the Cocos plate subducts under the Caribbean plate at ~8.5 cm/yr. Rapid plate convergence produces frequent large earthquakes (~50yr recurrence interval) and pronounced crustal deformation (0.1-2.0m/ky uplift). Seven uplifted segments have been identified in previous studies using broad geomorphic surfaces (Hare & Gardner 1984) and late Quaternary marine terraces (Marshall et al. 2010). These surfaces suggest long term net uplift and segmentation of the peninsula in response to contrasting domains of subducting seafloor (EPR, CNS-1, CNS-2). In this study, newer 10m contour digital topographic data (CENIGA- Terra Project) will be used to characterize and delineate this segmentation using morphotectonic analysis of drainage basins and correlation of fluvial terrace/ geomorphic surface elevations. The peninsula has six primary watersheds which drain into the Pacific Ocean; the Río Andamojo, Río Tabaco, Río Nosara, Río Ora, Río Bongo, and Río Ario which range in area from 200 km2 to 350 km2. The trunk rivers follow major lineaments that define morphotectonic segment boundaries and in turn their drainage basins are bisected by them. Morphometric analysis of the lower (1st and 2nd) order drainage basins will provide insight into segmented tectonic uplift and deformation by comparing values of drainage basin asymmetry, stream length gradient, and hypsometry with respect to margin segmentation and subducting seafloor domain. A general geomorphic analysis will be conducted alongside the morphometric analysis to map previously recognized (Morrish et al. 2010) but poorly characterized late Quaternary fluvial terraces. Stream capture and drainage divide migration are common processes throughout the peninsula in response to the ongoing deformation. Identification and characterization of basin piracy throughout the peninsula will provide insight into the history of landscape evolution in response to differential uplift. Conducting this morphotectonic analysis of the Nicoya Peninsula will provide further constraints on rates of segment uplift, location of segment boundaries, and advance the understanding of the long term deformation of the region in relation to subduction.

Beaver damming, fluvial geomorphology, and climate in Yellowstone National Park, Wyoming

NASA Astrophysics Data System (ADS)

Persico, L.; Meyer, G.

2008-12-01

Beaver habitation is an important component of many fluvial landscapes that can impact a variety of hydrologic, geomorphic, and ecologic processes. Beaver damming, via long term valley aggradation, is thought to be important to the postglacial geomorphic evolution of many smaller mountain stream networks in the western United States. Loss of beaver dams can also cause rapid channel incision. Although several studies have documented rapid short-term aggradation of channels behind single beaver dams, there is little actual data on the long-term cumulative effect of beaver damming. In Yellowstone''s Northern Range, field surveys and stratigraphic section along six streams in the Northern Range reveal net thickness of mostly <2 m and patchy distribution of Holocene beaver-pond deposits. We estimate that reaches with clear morphologic and stratigraphic evidence for beaver-related aggradation constitute about 19% of the total stream network length. Reaches with probable and possible beaver-related aggradation make up an additional 8% and 2% of the network, respectively. The remaining 71% of the network has no clear evidence for beaver-related aggradation. Thirty-nine radiocarbon ages on beaver-pond deposits in northern Yellowstone fall primarily within the last 4000 yr, but gaps in dated beaver occupation from 2200-1800 and 950-750 cal yr BP correspond with severe and persistent droughts that likely caused low to ephemeral discharges in smaller streams. In the last two decades, severe drought has also caused streams that were occupied by beaver in the 1920s to become ephemeral. Beaver have been largely absent from the Northern Range since the mid-20th century, probably due to multiple ecological and climatic factors. This loss of beaver is thought to have led to widespread degradation of stream and riparian habitat via channel incision. Although 20th-century beaver loss has caused significant channel incision at some former dam sites, downcutting elsewhere in northern Yellowstone is unrelated to beaver dams or predates historic beaver extirpation. Overall, historic incision affects a 26% of reaches that have experienced beaver related aggradation in the study area. These results highlight the importance of historical and Holocene geomorphic studies in understanding the role of beaver in landscape dynamics.

The Arctic in the Twenty-First Century: Changing Biogeochemical Linkages across a Paraglacial Landscape of Greenland.

PubMed

Anderson, N John; Saros, Jasmine E; Bullard, Joanna E; Cahoon, Sean M P; McGowan, Suzanne; Bagshaw, Elizabeth A; Barry, Christopher D; Bindler, Richard; Burpee, Benjamin T; Carrivick, Jonathan L; Fowler, Rachel A; Fox, Anthony D; Fritz, Sherilyn C; Giles, Madeleine E; Hamerlik, Ladislav; Ingeman-Nielsen, Thomas; Law, Antonia C; Mernild, Sebastian H; Northington, Robert M; Osburn, Christopher L; Pla-Rabès, Sergi; Post, Eric; Telling, Jon; Stroud, David A; Whiteford, Erika J; Yallop, Marian L; Yde, Jacob C

2017-02-01

The Kangerlussuaq area of southwest Greenland encompasses diverse ecological, geomorphic, and climate gradients that function over a range of spatial and temporal scales. Ecosystems range from the microbial communities on the ice sheet and moisture-stressed terrestrial vegetation (and their associated herbivores) to freshwater and oligosaline lakes. These ecosystems are linked by a dynamic glacio-fluvial-aeolian geomorphic system that transports water, geological material, organic carbon and nutrients from the glacier surface to adjacent terrestrial and aquatic systems. This paraglacial system is now subject to substantial change because of rapid regional warming since 2000. Here, we describe changes in the eco- and geomorphic systems at a range of timescales and explore rapid future change in the links that integrate these systems. We highlight the importance of cross-system subsidies at the landscape scale and, importantly, how these might change in the near future as the Arctic is expected to continue to warm.

The Arctic in the Twenty-First Century: Changing Biogeochemical Linkages across a Paraglacial Landscape of Greenland

PubMed Central

Anderson, N. John; Saros, Jasmine E.; Bullard, Joanna E.; Cahoon, Sean M. P.; McGowan, Suzanne; Bagshaw, Elizabeth A.; Barry, Christopher D.; Bindler, Richard; Burpee, Benjamin T.; Carrivick, Jonathan L.; Fowler, Rachel A.; Fox, Anthony D.; Fritz, Sherilyn C.; Giles, Madeleine E.; Hamerlik, Ladislav; Ingeman-Nielsen, Thomas; Law, Antonia C.; Mernild, Sebastian H.; Northington, Robert M.; Osburn, Christopher L.; Pla-Rabès, Sergi; Post, Eric; Telling, Jon; Stroud, David A.; Whiteford, Erika J.; Yallop, Marian L.; Yde, Jacob C.

2017-01-01

Abstract The Kangerlussuaq area of southwest Greenland encompasses diverse ecological, geomorphic, and climate gradients that function over a range of spatial and temporal scales. Ecosystems range from the microbial communities on the ice sheet and moisture-stressed terrestrial vegetation (and their associated herbivores) to freshwater and oligosaline lakes. These ecosystems are linked by a dynamic glacio-fluvial-aeolian geomorphic system that transports water, geological material, organic carbon and nutrients from the glacier surface to adjacent terrestrial and aquatic systems. This paraglacial system is now subject to substantial change because of rapid regional warming since 2000. Here, we describe changes in the eco- and geomorphic systems at a range of timescales and explore rapid future change in the links that integrate these systems. We highlight the importance of cross-system subsidies at the landscape scale and, importantly, how these might change in the near future as the Arctic is expected to continue to warm. PMID:28596614

Geomorphic and geochemical controls on leaf wax biomarker transport and preservation in alluvial river systems: Rio Bermejo, Argentina

NASA Astrophysics Data System (ADS)

Repasch, M. N.; Sachse, D.; Hovius, N.; Scheingross, J. S.; Szupiany, R. N.

2017-12-01

Rivers are the primary conduits for organic carbon (OC) transfer from vegetation-rich uplands to long-term sinks, and thus are responsible for significant fluxes among different reservoirs of the carbon cycle. Fluxes of terrestrial OC out of river systems are generally less than fluxes into the systems, indicating loss of OC either during active fluvial transport, during residence in the active channel belt, or in older deposits outside of the active channel belt. Sedimentary biomarkers can be used to elucidate the mechanisms of transport, preservation, and/or transformation of OC during its passage from source to sink. In this study we evaluate the influence of fluvial sediment transport on preservation of terrestrial leaf wax n-alkanes. Our natural laboratory is the Rio Bermejo in northern Argentina, which transports sediment and organic matter from the central Andes over 700 km across the foreland basin without input of foreign material from tributaries. Rapid channel migration rates in a region of flexural foreland basin uplift (the forebulge) are responsible for remobilization of floodplain sediment and terrestrial OC. By sampling suspended sediment, river bank sediment, and soil from several locations along the length of the Rio Bermejo, and analyzing the dissolved chemistry, biomarker composition, and compound-specific stable isotopes, we can evaluate the geomorphic and geochemical processes that act to influence the preservation of terrestrial biomarkers through the river system. Data suggest that concentrations of long-chain terrestrial (C25-C33) alkanes decrease downstream, while concentrations of short-chain (C15-C19) alkanes increase. This trend is corroborated by a downstream increase in suspended sediment δ13C values, suggesting a replacement of terrestrial OC by microbial OC. It is likely that microbial degradation is responsible for loss of terrestrial biomarkers as their residence time in the river system increases. Controlled laboratory experiments and analysis of modern and aged river bank sediment samples will determine where and over what timescales leaf wax alkanes are oxidized by microorganisms. With these data, we will be able to quantify the loss of OC during fluvial transit and determine the mechanisms responsible, enabling carbon cycle models to account for these losses.

Vegetation-modulated landscape evolution: Effects of vegetation on landscape processes, drainage density, and topography

NASA Astrophysics Data System (ADS)

Istanbulluoglu, Erkan; Bras, Rafael L.

2005-06-01

Topography acts as a template for numerous landscape processes that include hydrologic, ecologic, and biologic phenomena. These processes not only interact with each other but also contribute to shaping the landscape as they influence geomorphic processes. We have investigated the effects of vegetation on thresholds for channel initiation and landform evolution using both analytical and numerical approaches. Vegetation is assumed to form a uniform ground cover. Runoff erosion is modeled based on a power function of excess shear stress, in which shear stress efficiency is inversely proportional to vegetation cover. This approach is validated using data. Plant effect on slope stability is represented by additional cohesion provided by plant roots. Vegetation cover is assumed to reduce sediment transport rates due to physical creep processes (rainsplash, dry ravel, and expansion and contraction of sediments) according to a negative exponential relationship. Vegetation grows as a function of both available cover and unoccupied space by plants and is killed by geomorphic disturbances (runoff erosion and landsliding) and wildfires. Analytical results suggest that in an equilibrium basin with a fixed vegetation cover, plants may cause a transition in the dominant erosion process at the channel head. A runoff erosion-dominated landscape, under none or poor vegetation cover, may become landslide dominated under a denser vegetation cover. The sign of the predicted relationship between drainage density and vegetation cover depends on the relative influence of vegetation on different erosion phenomena. With model parameter values representative of the Oregon Coast Range (OCR), numerical experiments conducted using the Channel Hillslope Integrated Landscape Development (CHILD) model confirm the findings based on the analytical theory. A highly dissected fluvial landscape emerges when surface is assumed bare. When vegetation cover is modeled, landscape relief increases, resulting in hollow erosion dominated by landsliding. Interestingly, our simulations underscore the importance of vegetation disturbances by geomorphic events and wildfires on the landscape structure. Simulated landscapes resemble real-world catchments in the OCR when such disturbances are considered.

Immediate propagation of deglacial environmental change to turbidite systems along the Chilean continental slope

NASA Astrophysics Data System (ADS)

Bernhardt, Anne; Schwanghart, Wolfgang; Hebbeln, Dierk; Stuut, Jan-Berend; Strecker, Manfred

2017-04-01

Understanding how Earth-surface processes respond to past climatic perturbations is crucial for making informed predictions about future impacts of climate change on sediment fluxes. Sedimentary records provide the archives for inferring these processes but their interpretation is compromised by our incomplete understanding of how sediment-routing systems respond to millennial-scale climate cycles. We analyzed seven sediment cores recovered from turbidite depositional sites along the continental slope of the Chile convergent margin. These depositional systems represent the ultimate sedimentary archives before sediment gets recycled during subduction processes and provide relatively continuous and well-dated records. The study sites span a pronounced arid-to-humid gradient with variable topographic gradients and related connectivity of terrestrial and marine landscapes on the continental slope. This setting allowed us to study event-related depositional processes from the Last Glacial Maximum to present in different climatic and geomorphic settings. The turbidite record was quantified in terms of turbidite thickness and frequency. The three studied sites show a steep decline of turbidite deposition during deglaciation. High rates of sea-level rise significantly lag the decline in turbidite deposition by 3-6.5 kyrs. However, comparison to paleoclimate proxies shows that this spatio-temporal sedimentary pattern mirrors the deglacial humidity decrease and concomitant warming with little to no lag times. Our results suggest that the deglacial humidity decrease resulted in a decrease of fluvial sediment supply, which propagated rapidly through the highly connected systems into the marine sink in north-central Chile. In contrast, in south-central Chilean systems, connectivity between the Andean erosional zone and the fluvial transfer zone probably decreased abruptly by the deglaciation of piedmont lakes, resulting in a significant and rapid decrease of sediment supply to the ocean. Additionally, reduced moisture supply may have also contributed to the rapid decline of turbidite deposition. These different causes result in similar depositional patterns in the marine sinks. We conclude that turbiditic strata can act as reliable recorders of climate change across a wide range of climatic zones and geomorphic conditions. However, the underlying causes for similar signal manifestations in the sinks may differ, ranging from maintained high system connectivity to abrupt connectivity loss.

A meeting of the waters: interdisciplinary challenges and opportunities in tidal rivers

USGS Publications Warehouse

Ensign, Scott H.; Noe, Gregory B.; Hupp, Cliff R.; Fagherazzi, Sergio

2012-01-01

At the interface of estuarine tides and freshwater rivers lie wetland and aquatic ecosystems, which experience dramatic effects of sea level rise. There, nontidal channels and riparian floodplains are transforming into tidal ecosystems, and tidal freshwater ecosystems are receiving increasing salinity. These river-floodplain systems have both fluvial characteristics, including meandering channels and expansive floodplain forests, and estuarine characteristics, including tides and intertidal wetlands [see Barendregt et al., 2009; Conner et al., 2007, and references therein]. Because tidal rivers lie at the disciplinary divide between fluvial and estuarine science, a knowledge gap has developed in scientists' understanding of the geomorphic and biogeochemical response of these environments to sea level rise, climate change, and anthropogenically driven variations in watershed exports.

Geomorphic status of regulated rivers in the Iberian Peninsula.

PubMed

Lobera, G; Besné, P; Vericat, D; López-Tarazón, J A; Tena, A; Aristi, I; Díez, J R; Ibisate, A; Larrañaga, A; Elosegi, A; Batalla, R J

2015-03-01

River regulation by dams modifies flow regimes, interrupts the transfer of sediment through channel networks, and alters downstream bed dynamics, altogether affecting channel form and processes. So far, most studies on the geomorphic impacts of dams are restricted to single rivers, or even single river stretches. In this paper we analyse the geomorphic status of 74 river sites distributed across four large basins in the Iberian Peninsula (i.e. 47 sites located downstream of dams). For this purpose, we combine field data with hydrological data available from water agencies, and analyse historical (1970) and current aerial photographs. In particular, we have developed a Geomorphic Status (GS) index that allows us to assess the physical structure of a given channel reach and its change through time. The GS encompasses a determination of changes in sedimentary units, sediment availability, bar stability and channel flow capacity. Sites are statistically grouped in four clusters based on contrasted physical and climate characteristics. Results emphasise that regulation changes river's flow regime with a generalized reduction of the magnitude and frequency of floods (thus flow competence). This, in addition to the decrease downstream sediment supply, results in the loss of active bars as they are encroached by vegetation, to the point that only reaches with little or no regulation maintain exposed sedimentary deposits. The GS of regulated river reaches is negatively correlated with magnitude of the impoundment (regulation). Heavily impacted reaches present channel stabilization and, in contrast to the hydrological response, the distance and number of tributaries do not reverse the geomorphic impact of the dams. Stabilization limits river dynamics and may contribute to the environmental degradation of the fluvial ecosystem. Overall, results describe the degree of geomorphological alteration experienced by representative Iberian rivers mostly because of regulation, challenging the successful long-term implementation of river basin management programmes. Copyright © 2014 Elsevier B.V. All rights reserved.

Eemian and post-Eemian fluvial dynamics in the Lesser Caucasus

NASA Astrophysics Data System (ADS)

von Suchodoletz, Hans; Gärtner, Andreas; Zielhofer, Christoph; Faust, Dominik

2018-07-01

Mountain regions such as the Lesser Caucasus are a focus of ongoing environmental changes. To understand their future evolution, information about their former geomorphic and environmental dynamics is required. The former fluvial dynamics derived from fluvial sediment archives can offer such insights. However, the fluvial dynamics of the Lesser Caucasus since the Eemian interglacial have not been systematically investigated so far. Thus, we have studied late Pleistocene and Holocene sediments of several rivers originating from the central Lesser Caucasus. The studied rivers show a mostly coherent record of fluvial dynamics: Minor aggradation occurred during early Marine Isotope Stage (MIS) 5, incision during late MIS 5 or early MIS 4, intensive silty aggradation at least during late MIS 3, incision during early MIS 2, coarse-grained aggradation probably during some millenia until ca. 19 ka, and aggradation ca. 14-13 ka. Following incision around the Pleistocene/Holocene transition, aggradation resumed around 6.0, 3.4 - 2.0 and 0.5 - 0.15 cal. ka BP. Generally, periods of aggradation, incision and stability could be linked with regional climatic or anthropogenic influences on regional landscape stability and water availability. The fluvial dynamics of the central Lesser Caucasus mostly differed even between neighbouring regions, and only in cases of significant hemispheric climatic fluctuations as around 20 ka, during the Pleistocene/Holocene transition or the Little Ice Age, were similar over-regional fluvial patterns observed. This demonstrates the individual character of river systems especially in mountain regions such as the southern Caucasus with strong geoecological gradients. Thus, to understand the former landscape dynamics of mountain landscapes, investigations of fluvial sediment archives on a regional to sub-regional scale are necessary.

Fluvial Geomorphology and River Restoration: Uneasy Allies (Invited)

NASA Astrophysics Data System (ADS)

Kondolf, G. M.

2009-12-01

A growing body of literature demonstrates that river restoration based on understanding of geomorphic and ecological process is more likely to be sustainable than form-based approaches. In the early days of river ‘restoration’ in North America, most projects involved bank stabilization, habitat structure placement, or construction of rocked meandering channels, at odds with restoration of the dynamic processes we now see as fundamental to effective, sustainable restoration. Recent years have seen a growing body of restoration programs emphasizing restoration of connectivity and geomorphic process. This evolution has been reflected in publications, from the form-based approach advocated in the early 1990s by an NRC panel (which did not include a geomorphologist) to more recent works by interdisciplinary panels emphasizing process restoration. Large-scale river restoration came later to Europe, motivated by the EU Water Framework Directive (2000) requirements that member states implement measures to improve ecological status of degraded rivers. Interestingly, European approaches to restoration have often reflected a more nuanced understanding of process, including deliberate recreation of unstable braided channels, removal of bank protection, and reconnecting floodplains. In part this may reflect a reaction to the more thorough post-war channelization of rivers in western Europe. In part it may also reflect a greater influence of academic and research laboratories upon practitioners than in the US, where a strong anti-intellectual strain, cultural preference for easy fixes, and reluctance to conduct objective post-project assessments have contributed to the adoption of form-based approaches by many public agencies.

Storm and tide influenced depositional architecture of the Pliocene-Pleistocene Chad Formation, Chad Basin (Bornu Sub-basin) NE Nigeria: A mixed fluvial, deltaic, shoreface and lacustrine complex

NASA Astrophysics Data System (ADS)

Shettima, Bukar; Kyari, Aji Maina; Aji, Mallam Musa; Adams, Fatimoh Dupe

2018-07-01

Lithofacies analyses of the upper part of the Chad Formation (Bama Ridge Complex) in the Bornu Sub-basin of the Chad Basin indicated four facies associations; fluvial, deltaic, shoreface and lacustrine sequences. The fluvial sequences are composed of fining upward cycles with successive occurrence of planar crossbedded sandstone facies displaying unimodal paleocurrent system and rare mudstone facies typical of braided river system. The deltaic succession consists of both fining and coarsening upwards cycles with the former depicting fluvial setting of an upper delta plain while the later suggestive of mouth-bar sequences. The setting displays a polymodal current system of fluvial, waves, storms and tides that were primarily induced by complex interactions of seiches and lunar tides. Similar current systems devoid of fluvial patterns were reflected in the coarsening upward packages of the shoreface sequences. Lacustrine succession composed of thick bioturbated mudstone facies generally defines the base of these coarsening upward profiles, giving a fluvio-lacustrine geomorphic relief where complex interaction developed the deltaic and shoreface facies along its shorelines. Clay mineral fractions of the formation are dominantly kaolinitic, indicating a predominantly humid tropical-subtropical climatic condition during their deposition. This climatic regime falls within the African humid period of the early-mid Holocene that led to the third lacustrine transgression of the Lake Mega-Chad, whereas the subordinate smectite mineralization points to aridification that characterizes most of the post humid period to recent.

Geomorphic Units on Titan: constraints on the origin of Undifferentiated Plains

NASA Astrophysics Data System (ADS)

Lopes, R. M. C.; Malaska, M. J.; Solomonidou, A.; LeGall, A.; Janssen, M. A.; Neish, C.; Turtle, E. P.; Birch, S. P. D.; Hayes, A. G.; Radebaugh, J.; Coustenis, A.

2015-10-01

We present the global distribution of the major classes of units and, where there are direct morphological contacts, describe how these classes of units relate to each other in terms of setting and emplacement history (Fig. 1). In particular, we focus on constraining the origin of the Undifferentiated Plains, which cover large expanses of Titan's surface (Fig. 2). We examined and evaluated different formation mechanisms, including (i) cryovolcanic origin, consisting of overlapping flows of low relief or (ii) sedimentary origins, resulting from fluvial/lacustrine or aeolian deposition, or accumulation of photolysis products created in the atmosphere. The results from our analysis suggest that a sedimentary origin is the most likely, with all the aforementioned processes possibly contributing.

Quaternary Geologic Framework of the St. Clair River between Michigan and Ontario, Canada

USGS Publications Warehouse

Foster, David S.; Denny, Jane F.

2009-01-01

Concern about the effect of geomorphic changes in the St. Clair River on water levels in the Upper Great Lakes resulted in the need for information on the geologic framework of the river. A geophysical survey of the Upper St. Clair River between Port Huron, MI, and Sarnia, Ontario, Canada, was conducted to determine the Quaternary geologic framework of the region. Previously available and new sediment samples and photographic and video data support the interpretation of the seismic stratigraphy and surficial geology. Three seismic stratigraphic units and two unconformities were identified. Glacial drift, consisting of interbedded till and glaciolacustrine deposits, overlies shale. Glaciofluvial and modern fluvial processes have eroded the glacial drift. Glaciofluvial, glaciolacustrine, fluvial, and lacustrine deposits overlie this unconformity. Seismic facies were interpreted to identify areas where these geologic facies exist; however, in the absence of distinct boundaries between facies, these deposits were mapped as one undifferentiated unit. This unit is thickest in the northernmost 3 kilometers of the river, where it consists of relatively coarse-grained fluvial, reworked glaciofluvial, and possibly glaciofluvial deposits. To the south, this coarse-grained unit thins or is absent. The undifferentiated unit comprises most of the surficial deposits in the northernmost river area. Some areas of glacial drift, predominantly till, are exposed at the lake and riverbed. The shale is not exposed anywhere in the region. Geophysical surveys at sites downriver, together with the results of previous studies, indicate that the geologic framework is similar to that in the northernmost river area except for the absence or reduced thickness of the coarse-grained fluvial deposits. Instead, glacial drift is exposed at the riverbed or is covered by a veneer of sediment. This information on the substrate is important for ongoing sediment transport studies.

Simulating Lanform Evolution on Mars

NASA Astrophysics Data System (ADS)

Howard, A. D.

2003-12-01

Knowledge of the planet Mars largely derives from remote sensing. Although these data are of increasing resolution and spectral coverage, including global topography at about 1 km2 resolution, interpretations vary widely about past processes and environments. Most uncertain is the environment of early Mars, during the Noachian Period (4.5 to about 3.5 b.y.). Interpretations range from a relatively warm wet climate with lakes and precipitation runoff, to a cold, dry Mars with valley networks originating solely from hydrothermally-driven seepage. Geomorphic analysis has generally been based upon image interpretation and terrestrial analogs. Increasingly, however, quantitative process and landform modeling is being brought to bear, including simulation modeling of landform evolution. A simulation model incorporates geomorphic processes relevant to Mars. Impact cratering is simulated geometrically by randomly-located impacts drawn from a size-frequency distribution. Scaling of crater dimensions is based upon fresh martian crater morphology, and heuristic rules govern inheritance from the pre-existing topography. Simulated cratered landscapes serve as initial conditions for simulated eolian erosion and deposition, inundation by lava flows,and fluvial denudation. The heuristic eolian model assumes that the long-term rate of eolian deposition and erosion is a function of an "exposure index", which is based upon the relative height of a location, such that valleys and crater floors are rapidly filled, level plains either receive no deposition or are slightly eroded, and crater rims and hill summits are eroded. Deposition on Mars is assumed to occur from saltation, deposition of dust from dust storms, and long-distance transport of crater ejecta and volcanic ash. The eolian model predicts that craters should infill at a nearly constant rate. Simulation of lava flow emplacement is also heuristic, based upon flow events of variable duration from specified source vents. The probability of a lava flow extending in a given direction is assumed greatest at the margins of recently active portions of the flow and is proportional to the local topographic gradient. Inundation of a cratered landscape is highly stochastic, with some craters surviving unscathed while neighbors are filled. Sumulation of fluvial erosion largely follows the landform evolution model of Howard [1994], with: 1) weathering rates a function of regolith thickness; 2) mass wasting involving both linear diffusional creep and accelerated motion as slopes approach a limiting angle; 3) detachment-limited fluvial erosion based upon shear stress, unit stream power, or bedload abrasion; and 4) sediment transport and deposition/erosion in alluvial channels, fans, deltas, and pediments. Fluvial erosion of cratered landscapes under assumed desert climate results in short valley systems with enclosed drainages in and between craters that resemble landscapes of the terrestrial Mojave and Basin and Range provinces. Drainage integration increases with time, but continued impact cratering disrupts fluvial networks. Model validation is limited by low resolution of images and topography, lack of stratigraphic information, absence of dating methods, and strong post-Noachian modification of landscapes by wind, mass-wasting, and "gardening" by small impacts. Nevertheless, the profiles of streams and fans are consistent with the gentle sections being sand or fine gravel, and steeper bedrock or boulder-floored sections. Simulated landscapes also compare favorably with the visual appearance of degraded Noachian cratered landscapes and with hypsometry and slope geometry statistics.

Insights into organic carbon oxidation potential during fluvial transport from laboratory and field experiments

NASA Astrophysics Data System (ADS)

Scheingross, J. S.; Dellinger, M.; Eglinton, T. I.; Fuchs, M. C.; Golombek, N.; Hilton, R. G.; Hovius, N.; Lupker, M.; Repasch, M. N.; Sachse, D.; Turowski, J. M.; Vieth-Hillebrand, A.; Wittmann, H.

2017-12-01

Over geologic timescales, the exchange of organic carbon (OC) between the atmosphere, hydropshere, biosphere and geosphere can be a major control on atmospheric carbon dioxide concentrations. The carbon fluxes from the oxidation of rock-derived OC (a CO2 source) and erosion, transport, and burial of biospheric OC (a potential CO2 sink) during fluvial transit are approximately the same order of magnitude or larger than those from silicate weathering. Despite field data showing increasing oxidation of OC moving downstream in lowland rivers, it is unclear if losses occur primarily during active fluvial transport, where OC is in continual motion within an aerated river, or during periods of temporary storage in river floodplains which may be anoxic. The unknown location of OC oxidation (i.e., river vs. floodplain) limits our ability to mechanistically link geochemical and geomorphic processes which are required to develop models capable of predicting OC losses, constrain carbon budgets, and unravel links between climate, tectonics, and erosion. To fill this knowledge gap, we investigated OC oxidation in controlled laboratory experiments and a simplified field setting. We performed experiments in annular flumes that simulate fluvial transport without floodplain storage, allowing mixtures of OC-rich and siliciclastic sediment to be transported for distances of 1000 km. Preliminary experiments exploring both rock-derived and biospheric OC sources show minimal OC oxidation during active river transport, consistent with the idea that the majority of OC loss occurs during transient floodplain storage. These results are also consistent with new field data collected in the Rio Bermejo, Argentina, a lowland river traversing 800 km with no tributary inputs, where aged floodplain deposits have 3 to 10 times lower OC concentrations compared to modern river sediments. Together our field data and experiments support the hypothesis that oxidation of OC occurs primarily during floodplain storage rather than fluvial transport.

Late Pliocene establishment of exorheic drainage in the northeastern Tibetan Plateau as evidenced by the Wuquan Formation in the Lanzhou Basin

NASA Astrophysics Data System (ADS)

Guo, Benhong; Liu, Shanpin; Peng, Tingjiang; Ma, Zhenhua; Feng, Zhantao; Li, Meng; Li, Xiaomiao; Li, Jijun; Song, Chunhui; Zhao, Zhijun; Pan, Baotian; Stockli, Daniel F.; Nie, Junsheng

2018-02-01

The fluvial archives in the upper-reach Yellow River basins provide important information about drainage history of the northeastern Tibetan Plateau (TP) associated with geomorphologic evolution and climate change. However, the Pliocene fluvial strata within this region have not been studied in detail, hence limiting the understanding of the late Cenozoic development of regional fluvial systems. In this paper, we present the results of a study of the geochronology, sedimentology, and provenance of the fluvial sequence of the Wuquan Formation in the Lanzhou Basin in the northeastern TP. Magnetostratigraphic and cosmogenic nuclide burial ages indicate that the Wuquan Formation was deposited during 3.6-2.2 Ma. Furthermore, sedimentary facies, gravel composition, paleocurrent data, and detrital zircon Usbnd Pb age spectra reveal that the fluvial sequence resembles the terraces of the Yellow River in terms of source area, flow direction, and depositional environment. Our results indicate that a paleo-drainage system flowing out of the northeastern TP was established by ca. 3.6 Ma and that the upstream parts of the Yellow River must have developed subsequently from this paleo-drainage system. The late Pliocene drainage system fits well with the dramatic uplift of the northeastern TP, an intensified Asian summer monsoon, and global increase in erosion rates, which may reflect interactions between geomorphic evolution, tectonic deformation, and climate change.

The ecology of methane in streams and rivers: Patterns, controls, and global significance

USGS Publications Warehouse

Stanley, Emily H.; Casson, Nora J.; Christel, Samuel T.; Crawford, John T.; Loken, Luke C.; Oliver, Samantha K.

2016-01-01

Streams and rivers can substantially modify organic carbon (OC) inputs from terrestrial landscapes, and much of this processing is the result of microbial respiration. While carbon dioxide (CO2) is the major end-product of ecosystem respiration, methane (CH4) is also present in many fluvial environments even though methanogenesis typically requires anoxic conditions that may be scarce in these systems. Given recent recognition of the pervasiveness of this greenhouse gas in streams and rivers, we synthesized existing research and data to identify patterns and drivers of CH4, knowledge gaps, and research opportunities. This included examining the history of lotic CH4 research, creating a database of concentrations and fluxes (MethDB) to generate a global-scale estimate of fluvial CH4 efflux, and developing a conceptual framework and using this framework to consider how human activities may modify fluvial CH4 dynamics. Current understanding of CH4 in streams and rivers has been strongly influenced by goals of understanding OC processing and quantifying the contribution of CH4 to ecosystem C fluxes. Less effort has been directed towards investigating processes that dictate in situ CH4 production and loss. CH4 makes a meager contribution to watershed or landscape C budgets, but streams and rivers are often significant CH4 sources to the atmosphere across these same spatial extents. Most fluvial systems are supersaturated with CH4 and we estimate an annual global emission of 26.8 Tg CH4, equivalent to ~15-40% of wetland and lake effluxes, respectively. Less clear is the role of CH4 oxidation, methanogenesis, and total anaerobic respiration to whole ecosystem production and respiration. Controls on CH4 generation and persistence can be viewed in terms of proximate controls that influence methanogenesis (organic matter, temperature, alternative electron acceptors, nutrients) and distal geomorphic and hydrologic drivers. Multiple controls combined with its extreme redox status and low solubility result in high spatial and temporal variance of CH4 in fluvial environments, which presents a substantial challenge for understanding its larger-scale dynamics. Further understanding of CH4 production and consumption, anaerobic metabolism, and ecosystem energetics in streams and rivers can be achieved through more directed studies and comparison with knowledge from terrestrial, wetland, and aquatic disciplines.

Effects of Landscape History and Forest Management on Landslide-Driven Sediment Dynamics in Mountain Drainage Basins of Coastal British Columbia

NASA Astrophysics Data System (ADS)

Brardinoni, F.

2006-12-01

Landslide magnitude-frequency (LMF) and yield-area relations are examined for evaluating landslide-driven sediment dynamics in the Tsitika and Eve Rivers (612 km{2}), British Columbia. Research methods couple field work and air photo interpretation (API) in a GIS environment. API covers a seventy year time window. Results show that the long history of glacial erosion and the more recent forest management affect contemporary landslide activity in many respects. First, the nature and distribution of Quaternary-derived surficial deposits confounds primary lithologic effects; therefore, topographies underlain by less resistant geology are not typically associated with higher rates of landsliding. Second, the stratifications of LMF by landslide and terrain attributes have allowed detecting for the first time characteristic landslide length scales dependent on (i) movement style (i.e., slide, avalanche, and flow); (ii) type of material mobilized (i.e., bedrock and debris); and (iii) land use (i.e., forest clearing). As a conclusion, landscape bio-morphometric controls override the theoretical self-organized criticality of LMF relations. Third, slope-area analysis of landslide initiation and deposition zones reveals that bedrock landslides dominate the landscape on mountain summits and ridges; these processes deliver material to colluvial channels, in which debris is temporarily stored until remobilization occurs via full-scale debris flows. In undisturbed forest, during the seventy years examined, colluvial activity across geomorphic process domains (seen as sediment reservoirs) has generated net volume accumulation in unchannelled valleys, sink colluvial, and fluvially-dominated channels; in contrast, planar slopes and gullies have been degrading. Logging operations have accentuated aggradation in gullies and in unchannelled topographies. Finally, the area-based scaling relation of landslide sediment yield appears to match the spatial organization of geomorphic process domains. In this context, the contemporary, specific fluvial sediment yield (suspended) of British Columbia exceeds the specific landslide yield for drainage areas comprised between 5 and 50 km{2}. Cumulative daily yield indicates that colluvial sediment redistribution across landscape scales is limited to relatively small drainage areas; specifically, 90% of the colluvial load is injected within contributing area of about 0.6 km{2}.

Hydrologic, ecologic, and geomorphic responses of Brewery Creek to construction of a residential subdivision, Dane County, Wisconsin, 1999-2002

USGS Publications Warehouse

Selbig, William R.; Jopke, Peter L.; Marhshall, David W.; Sorge, Michael J.

2004-01-01

Other physical, biological, and ecological surveys including macroinvertebrates, fish, habitat, and geomorphology were done on segments of Brewery Creek affected by the study area. Macroinvertebrate sampling results (Hilsenhoff Biotic Index value, or HBI), on Brewery Creek ranged from 'very good' to 'good' water-quality with no appreciable differences during any phase of construction activity. Results for fish-community composition, however, were within the 'poor' range (Index of Biotic Integrity value, or IBI) during each year of testing. A general absence of intolerant species, with the exception of brown trout, reflects the low IBI values. Habitat values did not change significantly from preconstruction to postconstruction phases. Although installation of a double-celled culvert in Brewery Creek most likely altered the width-to-depth ratio in that reach, the overall habitat rating remained 'fair'. Fluvial geomorphology classifications including channel cross sections, bed- and bank-erosion surveys, and pebble counts did not indicate that stream geomorphic characteristics were altered by home-construction activity in the study area. Increases in fine-grained sediment at various cross sections were attributed to instream erosion processes, such as bank slumping, rather than increases in sediment delivery from the nearby construction site.

Geomorphology and its implication in urban groundwater environment: case study from Mumbai, India

NASA Astrophysics Data System (ADS)

Rani, V. R.; Pandalai, H. S.; Sajinkumar, K. S.; Pradeepkumar, A. P.

2015-06-01

Landforms of Mumbai Island have been largely modified by the urban sprawl and the demand for groundwater will increase exponentially in the future. Quality and quantity of groundwater occurrence in island are highly influenced by the geomorphic units. As this metropolis receives heavy rainfall, the area rarely faces the issue of water scarcity, nevertheless, quality always remains a question. The landforms of Mumbai Island have been shaped by a combination of fluvial, denudational and marine processes. These landforms are categorized into two broad zones on the basis of its influence in groundwater occurrence. Denudational landforms are categorized as runoff zones whereas the other two are categorized as storage zones. This classification is on the basis of occurrence and storage of groundwater. Mumbai Island is exposed to frequent sea water incursion and groundwater quality has deteriorated. The varied hydrogeological conditions prevalent in this area prevent rapid infiltration. This combined with the overextraction of groundwater resources for agriculture and industry has caused serious concern about the continued availability of potable water. This study aims at validating the geomorphic classification of the landforms with hydrogeochemistry and borehole data and it proved that geomorphology corroborates with groundwater chemistry and subsurface geology.

Spatial and temporal sensitivity of hydrogeomorphic responceand recovery to deforestation, Agriculture, and floods

USGS Publications Warehouse

Fitzpatrick, F.A.; Knox, J.C.

2000-01-01

Clear-cut logging followed by agricultural activity caused hydrologic and geomorphic changes in North Fish Creek, a Wisconsin tributary to Lake Superior. Hydro-geomorphic responses to changes in land use were sensitive to the location of reaches along the main stem and to the relative timing of large floods. Hydrologic and sediment-load modeling indicates that flood peaks were three times larger and sediment loads were five times larger during maximum agricultural activity in the 1920s and 1930s than prior to about 1890, when forest cover was dominant. Following logging, overbank sedimentation rates in the lower main stem increased four to six times above pre-settlement rates. Accelerated streambank and channel erosion in the upper main stem have been and continue to be primary sources of sediment to downstream reaches. Extreme floods in 1941 and 1946, followed by frequent moderate floods through 1954, caused extensive geomorphic changes along the entire main stem. Sedimentation rates in the lower main stem may have decreased in the last several decades as agricultural activity declined. However, geomorphic recovery is slow, as incised channels in the upper main stem function as efficient conveyors of watershed surface runoff and thereby continue to promote flooding and sedimentation problems downstream. [Key words: fluvial geomorphology, floods, erosion, sedimentation, deforestation, agriculture.].

Geomorphic Complexity of Sequential Fire and Floods in Mountain Watersheds

NASA Astrophysics Data System (ADS)

Brogan, D. J.; Nelson, P. A.; MacDonald, L. H.; Morgan, J. A.

2017-12-01

Fires and floods are important drivers of fluvial geomorphic changes. While each has been studied independently, there have been almost no situations where the hydrologic and geomorphic effects of fires and extreme floods could be compared at the watershed scale. Following the 2012 High Park fire in montane northcentral Colorado we began intensively monitoring channel changes in two 15 km2 watersheds (Skin Gulch and Hill Gulch) burned primarily at moderate to high severity. Summer thunderstorms resulted in extensive hillslope erosion and deposition in the valley bottoms, and subsequent incision through these deposits occurred due to spring snowmelt and elevated baseflows. The complex response associated with this state change from unburned to burned can be completely disrupted and overwhelmed by the larger changes resulting from extreme floods. Fifteen months after burning, both watersheds experienced an extreme flood resulting from a long-duration rainstorm; however, the geomorphic changes resulting from this flood differed markedly between the two watersheds. In Skin Gulch, sustained high flows from the September 2013 flood excavated nearly all of the accumulated sediment, expanded the active channel, and either scoured to bedrock or armored the bed with coarser substrate. Geomorphic changes in Hill Gulch due to the September 2013 flood, however, were small. The disparity between watersheds is likely the legacy of the catastrophic 1976 Big Thompson flood, which scoured out much of the previously accumulated sediment in Hill Gulch but did not appreciably impact Skin Gulch. These different sequences of disturbances indicate that fires in the Rocky Mountains often generate significant and dynamic geomorphic changes over sub-decadal timescales, while extreme floods can result in much longer lasting geomorphic changes. Our results allow us to compare the geomorphic sensitivity for different sequences of fire and floods, and propose a new conceptual model to explain the complicated interactions between the effects of fires and floods on the landscape.

Fluvial response to abrupt global warming at the Palaeocene/Eocene boundary.

PubMed

Foreman, Brady Z; Heller, Paul L; Clementz, Mark T

2012-11-01

Climate strongly affects the production of sediment from mountain catchments as well as its transport and deposition within adjacent sedimentary basins. However, identifying climatic influences on basin stratigraphy is complicated by nonlinearities, feedback loops, lag times, buffering and convergence among processes within the sediment routeing system. The Palaeocene/Eocene thermal maximum (PETM) arguably represents the most abrupt and dramatic instance of global warming in the Cenozoic era and has been proposed to be a geologic analogue for anthropogenic climate change. Here we evaluate the fluvial response in western Colorado to the PETM. Concomitant with the carbon isotope excursion marking the PETM we document a basin-wide shift to thick, multistoried, sheets of sandstone characterized by variable channel dimensions, dominance of upper flow regime sedimentary structures, and prevalent crevasse splay deposits. This progradation of coarse-grained lithofacies matches model predictions for rapid increases in sediment flux and discharge, instigated by regional vegetation overturn and enhanced monsoon precipitation. Yet the change in fluvial deposition persisted long after the approximately 200,000-year-long PETM with its increased carbon dioxide levels in the atmosphere, emphasizing the strong role the protracted transmission of catchment responses to distant depositional systems has in constructing large-scale basin stratigraphy. Our results, combined with evidence for increased dissolved loads and terrestrial clay export to world oceans, indicate that the transient hyper-greenhouse climate of the PETM may represent a major geomorphic 'system-clearing event', involving a global mobilization of dissolved and solid sediment loads on Earth's surface.

Geomorphic and vegetation changes in a meandering dryland river regulated by a large dam, Sauce Grande River, Argentina

NASA Astrophysics Data System (ADS)

Casado, Ana; Peiry, Jean-Luc; Campo, Alicia M.

2016-09-01

This paper investigates post-dam geomorphic and vegetation changes in the Sauce Grande River, a meandering dryland river impounded by a large water-conservation dam. As the dam impounds a river section with scarce influence of tributaries, sources for fresh water and sediment downstream are limited. Changes were inspected based on (i) analysis of historical photographs/imagery spanning pre- (1961) and post-dam (1981, 2004) channel conditions for two river segments located above and below the dam, and (ii) field survey of present channel conditions for a set of eight reference reaches along the river segments. Whilst the unregulated river exhibited active lateral migration with consequent adjustments of the channel shape and size, the river section below the dam was characterized by (i) marked planform stability (93 to 97%), and by (ii) vegetation encroachment leading to alternating yet localized contraction of the channel width (up to 30%). The present river displays a moribund, stable channel where (i) redistribution of sediment along the river course no longer occurs and (ii) channel forms constitute a remnant of a fluvial environment created before closing the dam, under conditions of higher energy. In addition to providing new information on the complex geomorphic response of dryland rivers to impoundment, this paper represents the very first geomorphic assessment of the regulated Sauce Grande and therefore provides an important platform to underpin further research assessing the geomorphic state of this highly regulated dryland river.

A Dataset of Rock Strength Along the Mixed Bedrock-alluvial Colorado River-Quantifying a Fundamental Control in Geomorphology

NASA Astrophysics Data System (ADS)

Pederson, J. L.; Bursztyn, N.

2014-12-01

Bedrock strength is a key parameter in slope stability, landscape erosion, and fluvial incision, though it is typically ignored or at best indirectly constrained in models, as with the k erodability parameter in stream-power formulations. Indeed, empirical datasets of rock strength suited to address geomorphic questions are rare, in part because of the difficulty in measuring those rocks that are heterolithic, weak, or poorly exposed. We have completed a large dataset of measured bedrock strength organized by rock units exposed along the length of the trunk Colorado-Green river through the Colorado Plateau of the western U.S. Measurements include Selby RMS, fracturing, and field compressive tests at 168 localities, as well as 672 individual-sample tensile-strength tests in the laboratory. These rock strength results are compared to geomorphic metrics of unit stream power, river gradient, valley-bottom width, and local relief through the arid Colorado Plateau. Our measurements trend coherently and logically with bedrock type and age/induration, especially in the case of tensile strength and when the influence of fracturing is also considered, signs that the dataset is robust. Focusing on bedrock (rather than alluvial) reaches of the fluvial transect and tensile strength, there is a positive rank-correlation and a strong power-law correlation between reach-averaged rock strength and unit stream power, as well as an elegant linear relation between tensile strength and river gradient. To address the problem of immeasureable rock types, we utilize the inverse power-law scaling between tensile strength and valley-bottom width to estimate the "effective" tensile strength of heterolithic, shale-rich bedrock in alluvial reaches. These results suggest that tensile strength varies to at least an order-of-magnitude smaller values than evident with directly testable rocks in this landscape, with implications for scaling erodibility parameters. Overall, results lead to the conclusion that bedrock strength is, in fact, the first-order control on large-scale fluvial geomorphology in the Colorado Plateau. On one hand this is intuitive, yet it highlights the erroneous but common assumption that bedrock erodibility is uniform or of secondary importance in fluvial morphology and landscape evolution.

Detrital dating of Asian orogenesis: insights and caveats

NASA Astrophysics Data System (ADS)

Burbank, D. W.

2007-12-01

Technological advances over the past two decades have facilitated increasingly routine application of single- crystal dating and cosmogenic nuclide dating to studies of orogenic erosion. Both approaches commonly utilize grab samples of detrital sediment, either modern or ancient. Whereas detrital cosmogenic data are typically used to define mean erosion rates for upstream catchments, single-crystal ages are used both to discern provenance and to define lag times: interval between isotopic closure and deposition. Recent results from dating modern fluvial sediments illuminate key concepts that underpin interpretations of results from older strata: the fidelity of the detrital signal, its evolution through an orogen, its relationship to discrete source areas, and its temporal evolution. Despite the increasing availability of dates and rates for detrial grains, relatively few studies have addressed the sources of uncertainty that modulate the precision and accuracy with which detrital results should be interpreted. Such uncertainties derive not only from sampling statistics and measurement uncertainties, but also from both geomorphic sources (seasonal variation in sediment supply and source, changes in glacial cover, the impact of stochastic geomorphic events, such as landslides), as well as tectonic ones (time-dependent deformation and thermal models, particle paths through the orogen). A better understanding of the impact of these uncertainties will underpin more reliable and less speculative interpretations of future dating results from both ancient and modern detrital fluvial sediments.

Geologic and geomorphic controls of coal development in some Tertiary Rocky Mountain basins, USA

USGS Publications Warehouse

Flores, R.M.

1993-01-01

Previous investigations have not well defined the controls on the development of minable coals in fluvial environments. This study was undertaken to provide a clearer understanding of these controls, particularly in of the lower Tertiary coal-bearing deposits of the Raton and Powder River basins in the Rocky Mountain region of the United States. In this region, large amounts of coals accumulated in swamps formed in the flow-through fluvial systems that infilled these intermontane basins. Extrabasinal and intrabasinal tectonism partly controlled the stratigraphic and facies distributions of minable coal deposits. The regional accumulation of coals was favored by the rapid basin subsidence coupled with minimal uplift of the source area. During these events, coals developed in swamps associated with anastomosed and meandering fluvial systems and alluvial fans. The extensive and high rate of sediment input from these fluvial systems promoted the formation of ombrotrophic, raised swamps, which produced low ash and anomalously thick coals. The petrology and palynology of these coals, and the paleobotany of the associated sediments, suggest that ombrotrophic, raised swamps were common in the Powder River Basin, where the climate during the early Tertiary was paratropical. The paleoecology of these swamps is identical to that of the modern ombrotrophic, raised swamps of the Baram and Mahakam Rivers of Borneo. ?? 1993.

Considering direct and indirect habitat influences on stream biota in eco-geomorphology research to better understand, model, and manage riverine ecosystems

NASA Astrophysics Data System (ADS)

Cienciala, P.; Nelson, A. D.

2017-12-01

The field of fluvial eco-geomorphology strives to improve the understanding of interactions between physical and biological processes in running waters. This body of research has greatly contributed to the advancement of integrated river science and management. Arguably, the most popular research themes in eco-geomorphology include hydrogemorphic controls of habitat quality and effects of disturbances such as floods, sediment transport events or sediment accumulation. However, in contrast to the related field of ecology, the distinction between direct and indirect mechanisms which may affect habitat quality and biotic response to disturbance has been poorly explored in eco-geomorphic research. This knowledge gap poses an important challenge for interpretations of field observations and model development. In this research, using the examples of benthic invertebrates and fish, we examine the importance of direct and indirect influences that geomorphic and hydraulic processes may exert on stream biota. We also investigate their implications for modeling of organism-habitat relationships. To achieve our goal, we integrate field and remote sensing data from montane streams in the Pacific Northwest region with habitat models. Preliminary results indicate that indirect hydrogeomorphic influences of stream organisms, such as those mediated by altered availability of food resources, can be as important as direct influences (e.g. physical disturbance). We suggest that these findings may also have important implications for modeling of riverine habitat.

Geomorphic Map of Worcester County, Maryland, Interpreted from a LIDAR-Based, Digital Elevation Model

USGS Publications Warehouse

Newell, Wayne L.; Clark, Inga

2008-01-01

A recently compiled mosaic of a LIDAR-based digital elevation model (DEM) is presented with geomorphic analysis of new macro-topographic details. The geologic framework of the surficial and near surface late Cenozoic deposits of the central uplands, Pocomoke River valley, and the Atlantic Coast includes Cenozoic to recent sediments from fluvial, estuarine, and littoral depositional environments. Extensive Pleistocene (cold climate) sandy dune fields are deposited over much of the terraced landscape. The macro details from the LIDAR image reveal 2 meter-scale resolution of details of the shapes of individual dunes, and fields of translocated sand sheets. Most terrace surfaces are overprinted with circular to elliptical rimmed basins that represent complex histories of ephemeral ponds that were formed, drained, and overprinted by younger basins. The terrains of composite ephemeral ponds and the dune fields are inter-shingled at their margins indicating contemporaneous erosion, deposition, and re-arrangement and possible internal deformation of the surficial deposits. The aggregate of these landform details and their deposits are interpreted as the products of arid, cold climate processes that were common to the mid-Atlantic region during the Last Glacial Maximum. In the Pocomoke valley and its larger tributaries, erosional remnants of sandy flood plains with anastomosing channels indicate the dynamics of former hydrology and sediment load of the watershed that prevailed at the end of the Pleistocene. As the climate warmed and precipitation increased during the transition from late Pleistocene to Holocene, dune fields were stabilized by vegetation, and the stream discharge increased. The increased discharge and greater local relief of streams graded to lower sea levels stimulated down cutting and created the deeply incised valleys out onto the continental shelf. These incised valleys have been filling with fluvial to intertidal deposits that record the rising sea level and warmer, more humid climate in the mid-Atlantic region throughout the Holocene. Thus, the geomorphic details provided by the new LIDAR DEM actually record the response of the landscape to abrupt climate change. Holocene trends and land-use patterns from Colonial to modern times can also be interpreted from the local macro- scale details of the landscape. Beyond the obvious utility of these data for land-use planning and assessments of resources and hazards, the new map presents new details on the impact of climate changes on a mid-latitude, outer Coastal plain landscape.

Landscape evolution in south-central Minnesota and the role of geomorphic history on modern erosional processes

USGS Publications Warehouse

Gran, K.B.; Belmont, P.; Day, S.S.; Finnegan, N.; Jennings, C.; Lauer, J.W.; Wilcock, P.R.

2011-01-01

The Minnesota River Valley was carved during catastrophic drainage of glacial Lake Agassiz at the end of the late Pleistocene. The ensuing base-level drop on tributaries created knickpoints that excavated deep valleys as they migrated upstream. A sediment budget compiled in one of these tributaries, the Le Sueur River, shows that these deep valleys are now the primary source of sediment to the Minnesota River. To compare modern sediment loads with pre-European settlement erosion rates, we analyzed incision history using fluvial terrace ages to constrain a valley incision model. Results indicate that even thoughthe dominant sediment sources are derived from natural sources (bluffs, ravines, and streambanks), erosion rates have increased substantially, due in part to pervasive changes in watershed hydrology.

Using graph theory to quantify coarse sediment connectivity in alpine geosystems

NASA Astrophysics Data System (ADS)

Heckmann, Tobias; Thiel, Markus; Schwanghart, Wolfgang; Haas, Florian; Becht, Michael

2010-05-01

Networks are a common object of study in various disciplines. Among others, informatics, sociology, transportation science, economics and ecology frequently deal with objects which are linked with other objects to form a network. Despite this wide thematic range, a coherent formal basis to represent, measure and model the relational structure of models exists. The mathematical model for networks of all kinds is a graph which can be analysed using the tools of mathematical graph theory. In a graph model of a generic system, system components are represented by graph nodes, and the linkages between them are formed by graph edges. The latter may represent all kinds of linkages, from matter or energy fluxes to functional relations. To some extent, graph theory has been used in geosciences and related disciplines; in hydrology and fluvial geomorphology, for example, river networks have been modeled and analysed as graphs. An important issue in hydrology is the hydrological connectivity which determines if runoff generated on some area reaches the channel network. In ecology, a number of graph-theoretical indices is applicable to describing the influence of habitat distribution and landscape fragmentation on population structure and species mobility. In these examples, the mobility of matter (water, sediment, animals) through a system is an important consequence of system structure, i.e. the location and topology of its components as well as of properties of linkages between them. In geomorphology, sediment connectivity relates to the potential of sediment particles to move through the catchment. As a system property, connectivity depends, for example, on the degree to which hillslopes within a catchment are coupled to the channel system (lateral coupling), and to which channel reaches are coupled to each other (longitudinal coupling). In the present study, numerical GIS-based models are used to investigate the coupling of geomorphic process units by delineating the process domains of important geomorphic processes in a high-mountain environment (rockfall, slope-type debris flows, slope aquatic and fluvial processes). The results are validated by field mapping; they show that only small parts of a catchment are actually coupled to its outlet with respect to coarse (bedload) sediment. The models not only generate maps of the spatial extent and geomorphic activity of the aforementioned processes, they also output so-called edge lists that can be converted to adjacency matrices and graphs. Graph theory is then employed to explore ‘local' (i.e. referring to single nodes or edges) and ‘global' (i.e. system-wide, referring to the whole graph) measures that can be used to quantify coarse sediment connectivity. Such a quantification will complement the mainly qualitative appraisal of coupling and connectivity; the effect of connectivity on catchment properties such as specific sediment yield and catchment sensitivity will then be studied on the basis of quantitative measures.

THE IMPACT OF HUMANS ON CONTINENTAL EROSION AND SEDIMENTATION (Invited)

NASA Astrophysics Data System (ADS)

Wilkinson, B.; McElroy, B.

2009-12-01

Tectonic uplift and erosional denudation of orogenic belts have long been the most important geologic processes that serve to shape continental surfaces, but the rate of geomorphic change resulting from these natural phenomena has now been outstripped by human activities associated with agriculture, construction, and mining. Although humans are now the most important geomorphic agent on the planet’s surface, natural and anthropogenic processes serve to modify quite different parts of the Earth landscape. In order to better understand the impact of humans on continental erosion, we have examined both long-term and short-term data on rates of sediment transfer in response to glacio-fluvial and anthropogenic processes. Phanerozoic rates of subaerial denudation inferred from preserved volumes of sedimentary rock require a mean continental erosion rate on the order of 16 meters per million years (m/My), resulting in the accumulation of about 5 giga-tons of sediment per year (Gt/y). Erosion irregularly increased over the ~542 million year span of Phanerozoic time to a Pliocene value of 81 m/My (~19 Gt/y). Current estimates of large river sediment loads are similar to this late Neogene value, and require net denudation of ice-free land surfaces at a rate of about 74 m/My (~25 Gt/y). Consideration of variation in large river sediment loads and the geomorphology of respective river basin catchments suggests that natural erosion is primarily confined to drainage headwaters; ~83% of the global river sediment flux is derived from the highest 10% of the Earth’s surface. Subaerial erosion as a result of human activity, primarily through agricultural practices, has resulted in a sharp increase in net rates of continental denudation; although less well constrained than estimates based on surviving rock volumes or current river loads, available data suggest that present farmland denudation is proceeding at a rate of about 600 m/My (~74 Gt/y), and is largely confined to lower elevations of the Earth’s land surface, primarily along passive continental margins; ~83% of cropland erosion occurs over the lower 65% of the Earth’s surface. The conspicuous disparity between natural sediment fluxes suggested by data on rock volumes and river loads (~25 Gt/y) and anthropogenic fluxes inferred from measured and modeled cropland soil losses (74 Gt/y) is readily resolved by data on thicknesses and ages of alluvial sediment that has been deposited immediately down slope from eroding croplands over the history of human agriculture. Accumulation of post-settlement alluvium on higher order tributary channels and floodplains (mean rate ~12,600 m/My) is the most important geomorphic process in terms of the erosion and deposition of sediment that is currently shaping the landscape of the Earth. It far exceeds even the impact of Pleistocene continental glaciers or the current impact of alpine erosion by glacial and/or fluvial processes. Human beings are therefore the dominant agent of topographic change operating on the surface of the planet today.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fecht, K.R.

Gable Mountain and Gable Butte are two ridges which form the only extensive outcrops of the Columbia River Basalt Group in the central portion of the Pasco Basin. The Saddle Mountains Basalt and two interbedded sedimentary units of the Ellensburg Formation crop out on the ridges. These include, from oldest to youngest, the Asotin Member (oldest), Esquatzel Member, Selah Interbed, Pomona Member, Rattlesnake Ridge Interbed, and Elephant Mountain Member (youngest). A fluvial plain composed of sediments from the Ringold and Hanford (informal) formations surrounds these ridges. The structure of Gable Mountain and Gable Butte is dominated by an east-west-trending majormore » fold and northwest-southeast-trending parasitic folds. Two faults associated with the uplift of these structures were mapped on Gable Mountain. The geomorphic expression of the Gable Mountain-Gable Butte area resulted from the comlex folding and subsequent scouring by post-basalt fluvial systems.« less

Late Holocene lowland fluvial archives and geoarchaeology: Utrecht's case study of Rhine river abandonment under Roman and Medieval settlement

NASA Astrophysics Data System (ADS)

van Dinter, Marieke; Cohen, Kim M.; Hoek, Wim Z.; Stouthamer, Esther; Jansma, Esther; Middelkoop, Hans

2017-06-01

Fluvial lowlands have become attractive human settling areas all around the world over the last few millennia. Because rivers kept changing their course and networks due to avulsion, the sedimentary sequences in these areas are archives of both fluvial geomorphological and archaeological development. We integrated geological and archaeological datasets to demonstrate the concurrence of the gradual abandonment of a major Rhine channel (Utrecht, The Netherlands), the development of human habitation in the area, and the interactions between them. The Utrecht case study highlights the stage-wise abandonment of a natural river channel, due to avulsion, coincident with intensifying human occupation in Roman and Early Medieval times (1st millennium AD). The analyses make maximum use of very rich data sets available for the study area and the tight age control that the geo-archaeological dataset facilitates, offering extra means of time-control to document the pacing of the abandonment process. This allows us to quantify change in river dimensions and meander style and to provide discharge estimates for successive stages of the abandonment phase over a 1000-year period of abandonment succession, from mature river to eventual Late Medieval overbuilt canal when the Rhine branch had lost even more discharge. Continued geomorphic development during this period - which includes the 'Dark Ages' (450-1000 AD) - appears to have been crucial in the development of Utrecht from Roman army fortress to Medieval ecclesial centre. The settlement dynamics in and around the city of Utrecht changed during the various phases of abandonment. In the bifurcating network of river branches forming the Rhine-Meuse delta, the main Rhine branch hosted the Roman limes military border and transport route. The Rhine- Vecht bifurcation at Utrecht provided an excellent location to raise a Roman fort. Continued geomorphic activity during abandonment in Early Medieval times was characterised by enhanced overbank sedimentation and shifts in the position of bifurcations. River flooding became more incidental in this stage, and alluvial-ridge occupancy became sensitive to flooding events for several centuries. We conclude by demonstrating that similar human-river interactions during Roman times occurred in several other deltas within the former Roman empire, with differences depending on the position of a settlement within the delta, the overall hydrological situation, and the ability of societies to control the changing environment.

Large-scale dam removal on the Elwha River, Washington, USA: source-to-sink sediment budget and synthesis

USGS Publications Warehouse

Warrick, Jonathan A.; Bountry, Jennifer A.; East, Amy E.; Magirl, Christopher S.; Randle, Timothy J.; Gelfenbaum, Guy R.; Ritchie, Andrew C.; Pess, George R.; Leung, Vivian; Duda, Jeff J.

2015-01-01

Understanding landscape responses to sediment supply changes constitutes a fundamental part of many problems in geomorphology, but opportunities to study such processes at field scales are rare. The phased removal of two large dams on the Elwha River, Washington, exposed 21 ± 3 million m3, or ~ 30 million tonnes (t), of sediment that had been deposited in the two former reservoirs, allowing a comprehensive investigation of watershed and coastal responses to a substantial increase in sediment supply. Here we provide a source-to-sink sediment budget of this sediment release during the first two years of the project (September 2011–September 2013) and synthesize the geomorphic changes that occurred to downstream fluvial and coastal landforms. Owing to the phased removal of each dam, the release of sediment to the river was a function of the amount of dam structure removed, the progradation of reservoir delta sediments, exposure of more cohesive lakebed sediment, and the hydrologic conditions of the river. The greatest downstream geomorphic effects were observed after water bodies of both reservoirs were fully drained and fine (silt and clay) and coarse (sand and gravel) sediments were spilling past the former dam sites. After both dams were spilling fine and coarse sediments, river suspended-sediment concentrations were commonly several thousand mg/L with ~ 50% sand during moderate and high river flow. At the same time, a sand and gravel sediment wave dispersed down the river channel, filling channel pools and floodplain channels, aggrading much of the river channel by ~ 1 m, reducing river channel sediment grain sizes by ~ 16-fold, and depositing ~ 2.2 million m3 of sand and gravel on the seafloor offshore of the river mouth. The total sediment budget during the first two years revealed that the vast majority (~ 90%) of the sediment released from the former reservoirs to the river passed through the fluvial system and was discharged to the coastal waters, where slightly less than half of the sediment was deposited in the river-mouth delta. Although most of the measured fluvial and coastal deposition was sand-sized and coarser (> 0.063 mm), significant mud deposition was observed in and around the mainstem river channel and on the seafloor. Woody debris, ranging from millimeter-size particles to old-growth trees and stumps, was also introduced to fluvial and coastal landforms during the dam removals. At the end of our two-year study, Elwha Dam was completely removed, Glines Canyon Dam had been 75% removed (full removal was completed 2014), and ~ 65% of the combined reservoir sediment masses—including ~ 8 Mt of fine-grained and ~ 12 Mt of coarse-grained sediment—remained within the former reservoirs. Reservoir sediment will continue to be released to the Elwha River following our two-year study owing to a ~ 16 m base level drop during the final removal of Glines Canyon Dam and to erosion from floods with larger magnitudes than occurred during our study. Comparisons with a geomorphic synthesis of small dam removals suggest that the rate of sediment erosion as a percent of storage was greater in the Elwha River during the first two years of the project than in the other systems. Comparisons with other Pacific Northwest dam removals suggest that these steep, high-energy rivers have enough stream power to export volumes of sediment deposited over several decades in only months to a few years. These results should assist with predicting and characterizing landscape responses to future dam removals and other perturbations to fluvial and coastal sediment budgets.

Anthropogenic disruption to the seismic driving of beach ridge formation: The Sendai coast, Japan.

PubMed

Goff, James; Knight, Jasper; Sugawara, Daisuke; Terry, James P

2016-02-15

The expected geomorphic after-effects of the Mw 9.0 Tōhoku-oki earthquake of 11 March 2011 (eastern Japan) are summarized by a schematic model of seismic driving, which details seismogenic disturbances to sediment systems that affect the rate or timing of sediment delivery to coastlines over timescales of 10(2)-10(4)years. The immediate physical environmental responses to this high-magnitude earthquake included a large tsunami and extensive region-wide slope failures. Normally, slope failures within mountain catchments would have significant impacts on Japan's river and coastal geomorphology in the coming decades with, for example, a new beach ridge expected to form within 20-100 years on the Sendai Plain. However, human activity has significantly modified the rate and timing of geomorphic processes of the region, which will have impacts on likely geomorphic responses to seismic driving. For example, the rivers draining into Sendai Bay have been dammed, providing sediment traps that will efficiently capture bedload and much suspended sediment in transit through the river system. Instead of the expected ~1 km of coastal progradation and formation of a ~3m high beach ridge prior to the next large tsunami, it is likely that progradation of the Sendai Plain will continue to slow or even cease as a result of damming of river systems and capture of river sediments behind dams. The resulting reduction of fluvial sediment delivery to the coast due to modification of rivers inadvertently makes seawalls and other engineered coastal structures even more necessary than they would be otherwise. Copyright © 2015 Elsevier B.V. All rights reserved.

Camera system considerations for geomorphic applications of SfM photogrammetry

USGS Publications Warehouse

Mosbrucker, Adam; Major, Jon J.; Spicer, Kurt R.; Pitlick, John

2017-01-01

The availability of high-resolution, multi-temporal, remotely sensed topographic data is revolutionizing geomorphic analysis. Three-dimensional topographic point measurements acquired from structure-from-motion (SfM) photogrammetry have been shown to be highly accurate and cost-effective compared to laser-based alternatives in some environments. Use of consumer-grade digital cameras to generate terrain models and derivatives is becoming prevalent within the geomorphic community despite the details of these instruments being largely overlooked in current SfM literature. This article is protected by copyright. All rights reserved.A practical discussion of camera system selection, configuration, and image acquisition is presented. The hypothesis that optimizing source imagery can increase digital terrain model (DTM) accuracy is tested by evaluating accuracies of four SfM datasets conducted over multiple years of a gravel bed river floodplain using independent ground check points with the purpose of comparing morphological sediment budgets computed from SfM- and lidar-derived DTMs. Case study results are compared to existing SfM validation studies in an attempt to deconstruct the principle components of an SfM error budget. This article is protected by copyright. All rights reserved.Greater information capacity of source imagery was found to increase pixel matching quality, which produced 8 times greater point density and 6 times greater accuracy. When propagated through volumetric change analysis, individual DTM accuracy (6–37 cm) was sufficient to detect moderate geomorphic change (order 100,000 m3) on an unvegetated fluvial surface; change detection determined from repeat lidar and SfM surveys differed by about 10%. Simple camera selection criteria increased accuracy by 64%; configuration settings or image post-processing techniques increased point density by 5–25% and decreased processing time by 10–30%. This article is protected by copyright. All rights reserved.Regression analysis of 67 reviewed datasets revealed that the best explanatory variable to predict accuracy of SfM data is photographic scale. Despite the prevalent use of object distance ratios to describe scale, nominal ground sample distance is shown to be a superior metric, explaining 68% of the variability in mean absolute vertical error.

Elevation-relief ratio, hypsometric integral, and geomorphic area-altitude analysis.

NASA Technical Reports Server (NTRS)

Pike, R. J.; Wilson, S. E.

1971-01-01

Mathematical proof establishes identity of hypsometric integral and elevation-relief ratio, two quantitative topographic descriptors developed independently of one another for entirely different purposes. Operationally, values of both measures are in excellent agreement for arbitrarily bounded topographic samples, as well as for low-order fluvial watersheds. By using a point-sampling technique rather than planimetry, elevation-relief ratio (defined as mean elevation minus minimum elevation divided by relief) is calculated manually in about a third of the time required for the hypsometric integral.

Spatial Analysis of Large Woody Debris Arrangement in a Midwestern U.S. River System: Geomorphic Implications and Influences

NASA Astrophysics Data System (ADS)

Martin, D. J.

2013-12-01

Large woody debris (LWD) is universally recognized as a key component of the geomorphological and ecological function of fluvial systems and has been increasingly incorporated into stream restoration and watershed management projects. However, 'natural' processes of recruitment and the subsequent arrangement of LWD within the river network are poorly understood and are thus, rarely a management consideration. Additionally, LWD research tends to be regionally biased toward mountainous regions, and scale biased toward the micro-scale. In many locations, the lack of understanding has led to the failure of restoration/rehabilitation projects that involved the use of LWD. This research uses geographic information systems and spatial analysis techniques to investigate longitudinal arrangement patterns of LWD in a low-gradient, Midwestern river. A large-scale GPS inventory of LWD was performed on the Big River, located in the eastern Missouri Ozarks resulting in over 5,000 logged positions of LWD along seven river segments covering nearly 100 km of the 237 km river system. A time series analysis framework was used to statistically identify longitudinal spatial patterns of LWD arrangement along the main stem of the river, and correlation analyses were performed to help identify physical controls of those patterns. Results indicate that upstream segments have slightly lower densities than downstream segments, with the exception of the farthest upstream segment. Results also show lack of an overall longitudinal trend in LWD density; however, periodogram analysis revealed an inherent periodicity in LWD arrangement. Periodicities were most evident in the downstream segments with frequencies ranging from 3 km to 7 km. Additionally, Pearson correlation analysis, performed within the segment displaying the strongest periodic behavior, show that LWD densities are correlated with channel sinuosity (r=0.25). Ongoing research is investigating further relationships between arrangement patterns and geomorphic and riparian variables. Understanding these spatial patterns and relationships will provide valuable insight into the application of LWD-related stream and watershed management practices, and fill a necessary regional knowledge gap in our understanding of LWD's role in fluvial processes.

Physical Drivers Vs. Effects of the Wolf-Elk Trophic Cascade on Fluvial Channel Planform, Olympic National Park, Washington

NASA Astrophysics Data System (ADS)

East, A. E.; Jenkins, K. J.; Happe, P. J.; Bountry, J.; Beechie, T. J.; Mastin, M. C.; Sankey, J. B.; Randle, T. J.

2016-12-01

Identifying the relative contributions of physical and ecological processes to channel evolution remains a substantial challenge in fluvial geomorphology. We use a 74-year aerial photographic record of the Hoh, Queets, Quinault, and Elwha Rivers, Olympic National Park, Washington, U.S.A., to investigate whether physical or trophic-cascade-driven ecological factors—excessive elk impacts after wolves were extirpated a century ago—are the dominant controls on channel planform of these gravel-bed rivers. We find that channel width and braiding show strong relationships with recent flood history; all four rivers have widened significantly in recent decades, consistent with increased flood activity since the 1970s. Channel planform also reflects sediment-supply changes, shown, for example, by the response of the Elwha River to a landslide. We surmise that the Hoh River, which shows a multi-decadal trend toward greater braiding, is adjusting to increased sediment supply associated with rapid glacial retreat. These rivers demonstrate rapid transmission of climatic signals through relatively short sediment-routing systems that lack substantial buffering by sediment storage. We infer no correspondence between channel evolution and elk abundance, suggesting that in this system effects of the wolf-driven trophic cascade are subsidiary to physical controls on channel morphology. Our examinations of stage-discharge history, historical maps, photographs, and descriptions, and empirical geomorphic thresholds do not support a previous conceptual model that these rivers underwent a fundamental geomorphic transition (widening, and a shift from single-thread to braided) resulting from large elk populations in the early 20th century. These findings differ from previous interpretations of Olympic National Park river dynamics, and also contrast with previous findings in Yellowstone National Park, where legacy effects of abundant elk nearly a century ago apparently still affect channel and floodplain morphology and connectivity. Different responses of Olympic and Yellowstone river morphology to trophic-cascade factors are likely due to hydrologic regime and large-wood availability.

Source-To-Sink Perspectives On The Mississippi River System, Miocene To Present, Mountain To Abyss

NASA Astrophysics Data System (ADS)

Bentley, S. J.; Blum, M. D.

2013-12-01

. The objective of this study is to present a synthesis of the Mississippi River source-to-sink system, from montane source to abyssal sink, to elucidate specific geomorphic components and boundaries in the system, controls on mass transfer, and resultant geomorphic and statigraphic development. The Mississippi River source-to-sink system constitutes one of the largest sources, conduits, and depocenters of sediment on Earth, extending from elevations of 3.7 km in the Rocky Mountains to the Gulf of Mexico abyssal plain. Despite being one of the most intensely studied fluvial-marine systems in the world, comprehensive understanding and management of the system's resources remain a challenge. The system is valuable in many ways: it provides navigation and water to the heart of North America, and sustains extensive marine fisheries. The river has built a delta that is home to millions of people and yet is subsiding rapidly. Ancestral Mississippi fluvial-marine deposits continue to yield high-value petroleum resources to exploration. To address the range of temporal and spatial scales over which the system has developed and continues to evolve, we will focus on three geological time spans that display contrasting geologic forcing and response: Miocene, Pleistocene, and late Holocene. The present configuration of source, conduit, and sink were established during the Miocene epoch, when tectonics (via the uplifting southern Rockies, and later the rejuvenated Appalachians) and climate (wet in the east and dry in the west) provided abundant water and sediment to prograde the shelf margin and initiate deep-sea fan growth. Pleistocene continental glaciation, eustasy, and catastrophic drainage events further sculpted the alluvial valley, and extended the shelf margin, and fan. Studies of Modern processes and Holocene delta development have provided keys to both the delta's past and future evolution, in terms of cyclic autogenic lobe-switching, mass-transport events, storm-driven sediment delivery to canyon heads, and allogenic/anthropogenic controls on sediment supply and subsidence.

Repeated catastrophic valley infill following medieval earthquakes in the Nepal Himalaya.

PubMed

Schwanghart, Wolfgang; Bernhardt, Anne; Stolle, Amelie; Hoelzmann, Philipp; Adhikari, Basanta R; Andermann, Christoff; Tofelde, Stefanie; Merchel, Silke; Rugel, Georg; Fort, Monique; Korup, Oliver

2016-01-08

Geomorphic footprints of past large Himalayan earthquakes are elusive, although they are urgently needed for gauging and predicting recovery times of seismically perturbed mountain landscapes. We present evidence of catastrophic valley infill following at least three medieval earthquakes in the Nepal Himalaya. Radiocarbon dates from peat beds, plant macrofossils, and humic silts in fine-grained tributary sediments near Pokhara, Nepal's second-largest city, match the timing of nearby M > 8 earthquakes in ~1100, 1255, and 1344 C.E. The upstream dip of tributary valley fills and x-ray fluorescence spectrometry of their provenance rule out local sources. Instead, geomorphic and sedimentary evidence is consistent with catastrophic fluvial aggradation and debris flows that had plugged several tributaries with tens of meters of calcareous sediment from a Higher Himalayan source >60 kilometers away. Copyright © 2016, American Association for the Advancement of Science.

Geochemical analyses reveal the importance of environmental history for blue carbon sequestration

NASA Astrophysics Data System (ADS)

Kelleway, J. J.; Saintilan, N.; Macreadie, P. I.; Baldock, J. A.; Heijnis, H.; Zawadzki, A.; Gadd, P.; Jacobsen, G.; Ralph, P. J.

2017-07-01

Coastal habitats including saltmarshes and mangrove forests can accumulate and store significant blue carbon stocks, which may persist for millennia. Despite this implied stability, the distribution and structure of intertidal-supratidal wetlands are known to respond to changes imposed by geomorphic evolution, climatic, sea level, and anthropogenic influences. In this study, we reconstruct environmental histories and biogeochemical conditions in four wetlands of similar contemporary vegetation in SE Australia. The objective is to assess the importance of historic factors to contemporary organic carbon (C) stocks and accumulation rates. Results from the four cores—two collected from marine-influenced saltmarshes (Wapengo marine site (WAP-M) and Port Stephens marine site (POR-M)) and two from fluvial influenced saltmarshes (Wapengo fluvial site (WAP-F) and Port Stephens fluvial site (POR-F))—highlight different environmental histories and preservation conditions. High C stocks are associated with the presence of a mangrove phase below the contemporary saltmarsh sediments in the POR-M and POR-F cores. 13C nuclear magnetic resonance analyses show this historic mangrove root C to be remarkably stable in its molecular composition despite its age, consistent with its position in deep sediments. WAP-M and WAP-F cores did not contain mangrove root C; however, significant preservation of char C (up to 46% of C in some depths) in WAP-F reveals the importance of historic catchment processes to this site. Together, these results highlight the importance of integrating historic ecosystem and catchment factors into attempts to upscale C accounting to broader spatial scales.

Episodes of fluvial and volcanic activity in Mangala Valles, Mars.

PubMed

Keske, Amber L; Hamilton, Christopher W; McEwen, Alfred S; Daubar, Ingrid J

2015-01-01

A new mapping-based study of the 900-km-long Mangala Valles outflow system was motivated by the availability of new high-resolution images and continued debates about the roles of water and lava in outflow channels on Mars. This study uses photogeologic analysis, geomorphic surface mapping, cratering statistics, and relative stratigraphy. Results show that Mangala Valles underwent at least two episodes of fluvial activity and at least three episodes of volcanic activity during the Late Amazonian. The occurrence of scoured bedrock at the base of the mapped stratigraphy, in addition to evidence provided by crater retention ages, suggests that fluvial activity preceded the deposition of two of the volcanic units. Crater counts performed at 30 locations throughout the area have allowed us to construct the following timeline: (1) formation of Noachian Highlands and possible initial flooding event(s) before ~1 Ga, (2) emplacement of Tharsis lava flows in the valley from ~700 to 1000 Ma, (3) a megaflooding event at ~700-800 Ma sourced from Mangala Fossa, (4) valley fill by a sequence of lava flows sourced from Mangala Fossa ~400-500 Ma, (5) another megaflooding event from ~400 Ma, (6) a final phase of volcanism sourced from Mangala Fossa ~300-350 Ma, and (7) emplacement of eolian sedimentary deposits in the northern portion of the valley ~300 Ma. These results are consistent with alternating episodes of aqueous flooding and volcanism in the valles. This pattern of geologic activity is similar to that of other outflow systems, such as Kasei Valles, suggesting that there is a recurring, and perhaps coupled, nature of these processes on Mars.

Evidence of a low-latitude glacial buzzsaw: Progressive hypsometry reveals height-limiting glacial erosion in tropical mountain belts

NASA Astrophysics Data System (ADS)

Cunningham, M.; Stark, C. P.; Kaplan, M. R.; Schaefer, J. M.; Winckler, G.

2017-12-01

It has been widely demonstrated that glacial erosion limits the height of mid-latitude mountain ranges—a phenomenon commonly referred to as the "glacial buzzsaw." The strength of the buzzsaw is thought to diminish, or die out completely, at lower latitudes, where glacial landscapes occupy only a small part of mountain belts affected by Pleistocene glaciation. Here we argue that glacial erosion has actually truncated the rise of many tropical orogens. To elicit signs of height-limiting glacial erosion in the tropics, we employ a new take on an old tool: we identify transient geomorphic features by tracking the evolution of (sub)catchment hypsometry with increasing elevation above base level, a method we term "progressive hypsometry." In several tropical mountain belts, including the Central Range of Taiwan, the Talamanca of Costa Rica, the Finisterres of Papua New Guinea, and the Rwenzoris of East Africa, progressive hypsometry reveals transient landscapes perched at various elevations, but the highest of these transient features are consistently glacial landscapes near the lower limit of late-Pleistocene glacial equilibrium line altitude (ELA) fluctuation. We attribute this pattern to an efficient glacial buzzsaw. In many cases, these glacial landscapes are undergoing contemporary destruction by headward propagating, fluvially-driven escarpments. We deduce that a duel between glacial buzzcutting and fluvially-driven scarp propagation has been ongoing throughout the Pleistocene in these places, and that the preservation potential of tropical glacial landscapes is low. To this end, we have identified possible remnants of glacial landscapes in the final stages of scarp consumption, and use 3He surface exposure age dating of boulders and bedrock surfaces in two of these landscapes to constrain major geomorphic activity to before the onset of the Last Glacial Maximum. Our work points to a profound climatic influence on the evolution of these warm, tectonically active, tropical mountain ranges and identifies glaciation as a trigger of autogenic behavior in flanking fluvial landscapes.

Temporal dynamics of instream wood in headwater streams draining mixed Carpathian forests

NASA Astrophysics Data System (ADS)

Galia, Tomáš; Šilhán, Karel; Ruiz-Villanueva, Virginia; Tichavský, Radek; Stoffel, Markus

2017-09-01

Instream wood can reside in fluvial systems over varying periods depending on its geographical context, instream position, tree species, piece size, and fluvial environment. In this paper, we investigate the residence time of two typical species representing a majority of instream wood in steep headwaters of the Carpathians and located under mixed forest canopy. Residence times of individual logs were then confronted with other wood parameters (i.e., wood dimensions, mean annual increment rate, tree age, class of wood stabilisation and decay, geomorphic function of wood pieces, and the proportion of the log length within the active channel). Norway spruce (Picea abies (L.) Karst.) samples indicated more than two times longer mean and maximal residence times as compared to European beech (Fagus sylvatica L.) based on the successful cross-dating of 127 logs. Maximum residence time in the headwaters was 128 years for P. abies and 59 years for F. sylvatica. We demonstrate that log age and log diameter played an important role in the preservation of wood in the fluvial system, especially in the case of F. sylvatica instream wood. By contrast, we did not observe any significant trends between wood residence time and total wood length. Instream wood with geomorphic functions (i.e., formation of steps and jams) did not show any differences in residence time as compared to nonfunctional wood. Nevertheless, we found shorter residence times for hillslope-stabilised pieces when compared to pieces located entirely in the channel (either unattached or stabilised by other wood or bed sediments). We also observed changes of instream wood orientation with respect to wood residence time. This suggests some movement of instream wood (i.e., its turning or short-distance transport), including pieces longer than channel width in the steep headwaters studied here (1.5 ≤ W ≤ 3.5 m), over the past few decades.

Fluvial wood function downstream of beaver versus man-made dams in headwater streams in Massachusetts, USA

NASA Astrophysics Data System (ADS)

David, G. C.; DeVito, L. F.; Munz, K. T.; Lisius, G.

2014-12-01

Fluvial wood is an essential component of stream ecosystems by providing habitat, increasing accumulation of organic matter, and increasing the processing of nutrients and other materials. However, years of channel alterations in Massachusetts have resulted in low wood loads despite the afforestation that has occurred since the early 1900s. Streams have also been impacted by a large density of dams, built during industrialization, and reduction of the beaver population. Beavers were reintroduced to Massachusetts in the 1940s and they have since migrated throughout the state. Beaver dams impound water, which traps sediment and results in the development of complex channel patterns and more ecologically productive and diverse habitats than those found adjacent to man-made dams. To develop better management practices for dam removal it is essential that we understand the geomorphic and ecologic function of wood in these channels and the interconnections with floodplain dynamics and stream water chemistry. We investigate the connections among fluvial wood, channel morphology, floodplain soil moisture dynamics, and stream water chemistry in six watersheds in Massachusetts that have been impacted by either beaver or man-made dams. We hypothesize that wood load will be significantly higher below beaver dams, subsequently altering channel morphology, water chemistry, and floodplain soil moisture. Reaches are surveyed up- and downstream of each type of dam to better understand the impact dams have on the fluvial system. Surveys include a longitudinal profile, paired with dissolved oxygen and ammonium measurements, cross-section and fluvial wood surveys, hydraulic measurements, and floodplain soil moisture mapping. We found that dissolved oxygen mirrored the channel morphology, but did not vary significantly between reaches. Wood loads were significantly larger downstream of beaver dams, which resulted in significant changes to the ammonium levels. Floodplain soil moisture dynamics revealed that wood loads increased the channel complexity and strengthened connections between the stream channel and floodplain. Future work will continue to explore the complex interconnections between beaver dams, channel morphology, hydraulics, floodplain dynamics and water chemistry.

Innovative Applications of Laser Scanning and Rapid Prototype Printing to Rock Breakdown Experiments

NASA Technical Reports Server (NTRS)

Bourke, Mary; Viles, Heather; Nicoll, Joe; Lyew-Ayee, Parris; Ghent, Rebecca; Holmlund, James

2008-01-01

We present the novel application of two technologies for use in rock breakdown experiments, i.e. close-range, ground-based 3D triangulation scanning and rapid prototype printing. These techniques aid analyses of form-process interactions across the range of scales relevant to breakdown (micron-m). This is achieved through (a) the creation of DEMs (which permit quantitative description and analysis of rock surface morphology and morphological change) and (b) the production of more realistically-shaped experimental blocks. We illustrate the use of these techniques, alongside appropriate data analysis routines, in experiments designed to investigate the persistence of fluvially-derived features in the face of subsequent wind abrasion and weathering. These techniques have a range of potential applications in experimental field and lab-based geomorphic studies beyond those specifically outlined here.

Detection and Mapping of the Geomorphic Effects of Flooding Using UAV Photogrammetry

NASA Astrophysics Data System (ADS)

Langhammer, Jakub; Vacková, Tereza

2018-04-01

In this paper, we present a novel technique for the objective detection of the geomorphological effects of flooding in riverbeds and floodplains using imagery acquired by unmanned aerial vehicles (UAVs, also known as drones) equipped with an panchromatic camera. The proposed method is based on the fusion of the two key data products of UAV photogrammetry, the digital elevation model (DEM), and the orthoimage, as well as derived qualitative information, which together serve as the basis for object-based segmentation and the supervised classification of fluvial forms. The orthoimage is used to calculate textural features, enabling detection of the structural properties of the image area and supporting the differentiation of features with similar spectral responses but different surface structures. The DEM is used to derive a flood depth model and the terrain ruggedness index, supporting the detection of bank erosion. All the newly derived information layers are merged with the orthoimage to form a multi-band data set, which is used for object-based segmentation and the supervised classification of key fluvial forms resulting from flooding, i.e., fresh and old gravel accumulations, sand accumulations, and bank erosion. The method was tested on the effects of a snowmelt flood that occurred in December 2015 in a montane stream in the Sumava Mountains, Czech Republic, Central Europe. A multi-rotor UAV was used to collect images of a 1-km-long and 200-m-wide stretch of meandering stream with fresh traces of fluvial activity. The performed segmentation and classification proved that the fusion of 2D and 3D data with the derived qualitative layers significantly enhanced the reliability of the fluvial form detection process. The assessment accuracy for all of the detected classes exceeded 90%. The proposed technique proved its potential for application in rapid mapping and detection of the geomorphological effects of flooding.

Geomorphic and sedimentary responses of the Bull Creek Valley (Southern High Plains, USA) to Pleistocene and Holocene environmental change

NASA Astrophysics Data System (ADS)

Arauza, Hanna M.; Simms, Alexander R.; Bement, Leland C.; Carter, Brian J.; Conley, Travis; Woldergauy, Ammanuel; Johnson, William C.; Jaiswal, Priyank

2016-01-01

Fluvial geomorphology and stratigraphy often reflect past environmental and climate conditions. This study examines the response of Bull Creek, a small ephemeral creek in the Oklahoma panhandle, to environmental conditions through the late Pleistocene and Holocene. Fluvial terraces were mapped and their stratigraphy and sedimentology documented throughout the course of the main valley. Based on their elevations, terraces were broadly grouped into a late-Pleistocene fill terrace (T3) and two Holocene fill-cut terrace sets (T2 and T1). Terrace systems are marked by similar stratigraphies recording the general environmental conditions of the time. Sedimentary sequences preserved in terrace fills record the transition from a perennial fluvial system during the late glacial period and the Younger Dryas to a semiarid environment dominated by loess accumulation and punctuated by flood events during the middle to late Holocene. The highest rates of aeolian accumulation within the valley occurred during the early to middle Holocene. Our data provide significant new information regarding the late-Pleistocene and Holocene environmental history for this region, located between the well-studied Southern and Central High Plains of North America.

Implications of the fluvial history of the Wacheqsa River for hydrologic engineering and water use at Chavín de Húntar, Peru

USGS Publications Warehouse

Contreras, Daniel A.; Keefer, David K.

2009-01-01

Channeling of water through a variety of architectural features represents a significant engineering investment at the first millennium B.C. ceremonial center of Chavín de Huántar in the Peruvian Central Andes. The site contains extensive evidence of the manipulation of water, apparently for diverse purposes. The present configuration of the two local rivers, however, keeps available water approximately 9m below the highest level of water-bearing infrastructure in the site. Geomorphic and archaeological investigation of the fluvial history of the Wacheqsa River has revealed evidence that the Chavín-era configuration of the Wacheqsa River was different. A substantially higher water level, likely the result of a local impoundment of river water caused by a landslide dam, made the provision of water for the hydrologic system within the site a more readily practical possibility. We review what is known of that system and argue that the fluvial history of the Wacheqsa River is critical to understanding this aspect of hydrologic engineering and ritual practice at Chavín. This study demonstrates the relative rapidity and archaeological relevance of landscape change in a dynamic environment.

Application of a new genetic classification and semi-automated geomorphic mapping approach in the Perth submarine canyon, Australia

NASA Astrophysics Data System (ADS)

Picard, K.; Nanson, R.; Huang, Z.; Nichol, S.; McCulloch, M.

2017-12-01

The acquisition of high resolution marine geophysical data has intensified in recent years (e.g. multibeam echo-sounding, sub-bottom profiling). This progress provides the opportunity to classify and map the seafloor in greater detail, using new methods that preserve the links between processes and morphology. Geoscience Australia has developed a new genetic classification approach, nested within the Harris et al (2014) global seafloor mapping framework. The approach divides parent units into sub-features based on established classification schemes and feature descriptors defined by Bradwell et al. (2016: http://nora.nerc.ac.uk/), the International Hydrographic Organization (https://www.iho.int) and the Coastal Marine and Ecological Classification Standard (https://www.cmecscatalog.org). Owing to the ecological significance of submarine canyon systems in particular, much recent attention has focused on defining their variation in form and process, whereby they can be classified using a range of topographic metrics, fluvial dis/connection and shelf-incising status. The Perth Canyon is incised into the continental slope and shelf of southwest Australia, covering an area of >1500 km2 and extending from 4700 m water depth to the shelf break in 170 m. The canyon sits within a Marine Protected Area, incorporating a Marine National Park and Habitat Protection Zone in recognition of its benthic and pelagic biodiversity values. However, detailed information of the spatial patterns of the seabed habitats that influence this biodiversity is lacking. Here we use 20 m resolution bathymetry and acoustic backscatter data acquired in 2015 by the Schmidt Ocean Institute plus sub-bottom datasets and sediment samples collected Geoscience Australia in 2005 to apply the new geomorphic classification system to the Perth Canyon. This presentation will show the results of the geomorphic feature mapping of the canyon and its application to better defining potential benthic habitats.

Slopes, Fans, Terraces and their Soils - A three Systems Approach for Estimating Future Climate and Land-Use Change

NASA Astrophysics Data System (ADS)

Voelkel, J.; Bens, O.; Eden, M.; Ramisch, A.

2015-12-01

Semiarid and arid landscapes in Namibia and the South African Republic (RAS) are sensitive to changes in the vegetation that covers and protects the surface. Climatic changes or anthropogenic influences such as farming, grazing and ploughing can degrade the landscape if the natural stability of the landscape and its capacity potential is exceeded. This will directly cause sediment mobilisation and deposition. We intend to examine the connections between earth-surface processes on slopes such as sheet wash, colluvial sediment transport, and eolian movements and their links to the fluvial system via three major geomorphic forms: slopes, fans, and terraces. This novel approach will be undertaken at three study sites in Namibia and RSA In their combination the geomorphic forms have the potential of being high-resolution geoarchives of surface changes ranging from the local to the regional scale. The source and depositional environments of the sediments will be characterised and a chronology of the erosion and deposition within these three geomorphic systems will be established using absolute dating techniques. Thus, activity and stability phases will be worked out mainly for the last three centuries up to a maximum of ~ 1000 years. This offers the possibility to compare the time scales with low human impact to those with intensive human impact (farming/grazing) on the landscape together with known climatic variation and analyze major forcings of the formation of slopes-fans-terraces-systems. Our results will provide answers on how much ecosystem services are and have been influenced either by climate or land use changes in the example regions, to better enable the decision and policy makers to select better managerial options and development plans. - The project "GeoArchives" is funded within the "SPACES" program (Science Partnerships for the Assessment of Complex Earth System Processes) by the Federal Ministry of Education and Research BMBF.

Late Quaternary landscape evolution, climate, and neotectonism along the eastern margin of the Puna Plateau: Pucará Valley, NW Argentina

NASA Astrophysics Data System (ADS)

McCarthy, J. A.; Schoenbohm, L. M.; Bierman, P. R.; Rood, D. H.

2013-12-01

The eastern margin of the Puna Plateau has been the focus of many studies seeking to link climatically-moderated surface processes and tectonism through dynamic feedbacks. However, evaluating any theories regarding climatic-tectonic feedbacks requires the determination of tectonic, climatic, and geomorphic chronologies across a wide region, from plateau to wedge-top to foreland. In this study, we contribute to that effort by examining Quaternary landscape evolution of a single intermontane basin of spatially uniform climate, adjacent to the plateau margin. The semi-arid Pucará Valley contains eight abandoned and incised geomorphic surfaces, most of which are deformed by active structures. These geomorphic surfaces - thin alluvial fans and strath terraces - dominate the landscape and record multiple pulses of incision in the late Quaternary. We find no evidence for significant depositional intervals and valley incision continues currently. Substantial accumulations of pedogenic carbonate and pedogenic gypsum within abandoned surfaces indicate that arid or semi-arid conditions are long lived in this valley. Conversely, relict periglacial morphology in adjacent ranges supports cooler temperatures in the past. River incision is enhanced across active structures, but preliminary observations suggest that the magnitude of deformation cannot fully explain the magnitude of incision. As a result, we argue that extrabasinal base-level lowering is the primary driver of incision in the Pucará Valley, but Quaternary deformation is significant enough to spatially influence erosion. Cooler climatic intervals may influence the sedimentology of alluvial and fluvial deposits, but we find no evidence for significant climatic changes that could change rates or styles of landscape evolution over this time frame. Pending cosmogenic nuclide analysis of fan deposits and river sediments will permit the derivation of fault slip rates, surface ages, modern and paleo-erosion rates, and sediment transport histories. These results will further refine our understanding of tectonic and climatic forcing of surface processes in the Quaternary.

Bottomland Hardwood Forests along the Upper Mississippi River

USGS Publications Warehouse

Yin, Y.; Nelson, J.C.; Lubinski, S.J.

1997-01-01

Bottomland hardwood forests along the United States' Upper Mississippi River have been drastically reduced in acreage and repeatedly logged during the nineteenth and twentieth centuries. Conversion to agricultural land, timber harvesting, and river modifications for flood prevention and for navigation were the primary factors that caused the changes. Navigation structures and flood-prevention levees have altered the fluvial geomorphic dynamics of the river and floodplain system. Restoration and maintenance of the diversity, productivity, and natural regeneration dynamics of the bottomland hardwood forests under the modified river environment represent a major management challenge.

Landform evolution modeling of fine-grained sedimentation on alluvial fans on Mars and Earth

NASA Astrophysics Data System (ADS)

Morgan, A. M.; Howard, A. D.; Moore, J. M.; Swander, Z. J.; Fink, D.; Korup, O.; Hesse, P. P.; Singh, T.; Srivastava, P.

2017-12-01

Reconstructing how rivers respond to changes in runoff or sediment supply by incising or aggrading has been pivotal in gauging the role of the Indian Summer Monsoon (ISM) as a geomorphic driver in the Himalayas. Here we present new data on how the fluvial systems of the Lesser Himalaya of India has responded to late Quaternary climate change. Our study is based on new chronological data for fluvial aggradation and incision from the Donga alluvial fan and several reaches of the upper Alaknanda River, as well as a meta-analysis of previous work. Fluvial sediments in the Himalayas in general, and quartz from the region in particular, have been previously noted for a number of unsuitable OSL properties including large recuperation and the existence of unremovable feldspar signals, leading to controversial discussions with regard to the reliability of existing OSL chronologies in this region. In order to improve the applicability and validity of OSL in the Lesser Himalaya, we have tested and applied pulsed OSL signals (POSL) to quartz grains from alluvial terrace and fan sediments, and propose a new chronology of regional fluvial aggradation. For previously dated terraces and alluvial fan sections, our POSL ages are systematically older than previously reported OSL ages. These results suggest periods of aggradation in the Alaknanda and Dehradun Valleys mainly between 20 and 50 ka. This most likely reflects decreased stream power during periods of weakened monsoon. The concentration of in-situ cosmogenic beryllium-10 from fluvial bedrock surfaces was also used to infer bedrock surface exposure ages, which should inform about episodes of active fluvial erosion. Resulting exposure ages span between 1.3 and 9.0 ka, suggesting that strath terraces were exposed relatively recently, and incision was dominant through most of the Holocene. In combination, our results support a precipitation-driven climatic control on fluvial dynamics, which regulates the balance between stream power and sediment supply. On a larger spatial scale, however, fluvial dynamics are probably not homogeneous as aggradation was taking place in adjacent catchments while incision dominated in the study area.

Quantitative analysis of geomorphic processes using satellite image data at different scales

NASA Technical Reports Server (NTRS)

Williams, R. S., Jr.

1985-01-01

When aerial and satellite photographs and images are used in the quantitative analysis of geomorphic processes, either through direct observation of active processes or by analysis of landforms resulting from inferred active or dormant processes, a number of limitations in the use of such data must be considered. Active geomorphic processes work at different scales and rates. Therefore, the capability of imaging an active or dormant process depends primarily on the scale of the process and the spatial-resolution characteristic of the imaging system. Scale is an important factor in recording continuous and discontinuous active geomorphic processes, because what is not recorded will not be considered or even suspected in the analysis of orbital images. If the geomorphic process of landform change caused by the process is less than 200 m in x to y dimension, then it will not be recorded. Although the scale factor is critical, in the recording of discontinuous active geomorphic processes, the repeat interval of orbital-image acquisition of a planetary surface also is a consideration in order to capture a recurring short-lived geomorphic process or to record changes caused by either a continuous or a discontinuous geomorphic process.

Episodes of fluvial and volcanic activity in Mangala Valles, Mars

PubMed Central

Keske, Amber L.; Hamilton, Christopher W.; McEwen, Alfred S.; Daubar, Ingrid J.

2017-01-01

A new mapping-based study of the 900-km-long Mangala Valles outflow system was motivated by the availability of new high-resolution images and continued debates about the roles of water and lava in outflow channels on Mars. This study uses photogeologic analysis, geomorphic surface mapping, cratering statistics, and relative stratigraphy. Results show that Mangala Valles underwent at least two episodes of fluvial activity and at least three episodes of volcanic activity during the Late Amazonian. The occurrence of scoured bedrock at the base of the mapped stratigraphy, in addition to evidence provided by crater retention ages, suggests that fluvial activity preceded the deposition of two of the volcanic units. Crater counts performed at 30 locations throughout the area have allowed us to construct the following timeline: (1) formation of Noachian Highlands and possible initial flooding event(s) before ~1 Ga, (2) emplacement of Tharsis lava flows in the valley from ~700 to 1000 Ma, (3) a megaflooding event at ~700–800 Ma sourced from Mangala Fossa, (4) valley fill by a sequence of lava flows sourced from Mangala Fossa ~400–500 Ma, (5) another megaflooding event from ~400 Ma, (6) a final phase of volcanism sourced from Mangala Fossa ~300–350 Ma, and (7) emplacement of eolian sedimentary deposits in the northern portion of the valley ~300 Ma. These results are consistent with alternating episodes of aqueous flooding and volcanism in the valles. This pattern of geologic activity is similar to that of other outflow systems, such as Kasei Valles, suggesting that there is a recurring, and perhaps coupled, nature of these processes on Mars. PMID:29176911

The sedimentary record of Carboniferous rivers: Continuing influence of land plant evolution on alluvial processes and Palaeozoic ecosystems

NASA Astrophysics Data System (ADS)

Davies, Neil S.; Gibling, Martin R.

2013-05-01

Evidence from modern rivers and the deep-time geological record attests to the fundamental importance of plant life for the construction of physical habitats within fluvial environments. Data from an extensive literature review and original fieldwork demonstrates that many landforms and geomorphic features of modern river systems appear in the Palaeozoic stratigraphic record once terrestrial vegetation had adopted certain evolutionary advances. For example, stable point bars are associated with the onset of rooted plants in the Siluro-Devonian and avulsive and anabranching fluvial systems become common at the same time as extensive arborescent vegetation in the Carboniferous. In this paper, we demonstrate a correlation between the diversification of physical fluvial environments and the expansion of terrestrial fauna and flora, with an emphasis on the culmination of these trends within Carboniferous alluvial systems. Many extrinsic factors have been considered as possible controls on the evolutionary timelines of terrestrialization for organisms. However, a fundamental prerequisite for achieving terrestrial biodiversity was the variety of physical habitats, especially riparian systems, available for newly evolved organisms. In association with abundant lowland meandering systems, the widespread appearance across Carboniferous alluvial plains of fixed-channel and anabranching reaches created further physical landforms for colonization and would have promoted increasingly complex hyporheic flow regimes. Furthermore the associated increase in arborescent vegetation and supply of large woody debris to inland and coastal rivers would have created a wealth of microhabitats for continental organisms. We argue that the expanding extent and diversity of physical alluvial niches during the Palaeozoic is an underappreciated driver of the terrestrialization of early continental life. The study of the deep-time fossil and stratigraphic record also illustrates that vegetation is a fundamental prerequisite for the creation of biogeomorphic alluvial landforms and physical habitats and microhabitats.

Channel morphology and bed-load yield in fluvial, formerly-glaciated headwater streams of the Columbia Mountains, Canada

NASA Astrophysics Data System (ADS)

Green, K. C.; Brardinoni, F.; Alila, Y.

2013-04-01

This study examines channel-reach morphology and bedload yield dynamics in relation to landscape structure and snowmelt hydrology in headwater streams of the Columbia Mountains, Canada. Data collection relies on field surveys and geographic information systems analysis in conjunction with a nested monitoring network of water discharge and bedload transfer. The landscape is characterized by subdued, formerly-glaciated upland topography in which the geomorphic significance of landslides and debris flows is negligible and fluvial processes prevail. While the spatial organization of channel morphology is chiefly controlled by glacially imposed local slope in conjunction with wood abundance and availability of glacigenic deposits, downstream patterns of the coarse grain-size fraction, bankfull width, bankfull depth, and stream power are all insensitive to systematic changes of local slope along the typically stepped long profiles. This is an indication that these alluvial systems have adjusted to the contemporary snowmelt-driven water and sediment transport regimes, and as such are able to compensate for the glacially-imposed boundary conditions. Bedload specific yield increases with drainage area suggesting that fluvial re-mobilization of glacial and paraglacial deposits dominate the sedimentary dynamics of basins as small as 2 km2. Stepwise multiple regression analysis shows that annual rates of sediment transfer are mainly controlled by the number of peak events over threshold discharge. During such events, repeated destabilization of channel bed armoring and re-mobilization of sediment temporarily stored behind LWD structures can generate bedload transport across the entire snowmelt season. In particular, channel morphology controls the variability of bedload response to hydrologic forcing. In the present case studies, we show that the observed spatial variability in annual bedload yield appears to be modulated by inter-basin differences in morphometric characteristics, among which slope aspect plays a critical part.

Connections between transport in events and transport at landscape-structuring timescales

NASA Astrophysics Data System (ADS)

Harman, C. J.; Lohse, K. A.; Troch, P. A.; Sivapalan, M.

2012-12-01

Complex spatial and temporal variability can arise in the critical zone when feedbacks occur at multiple time scales between transported materials and the landscape and soils through which it is transported. This is clearly illustrated where geomorphic transport processes, soil development, and vegetation interact in semi-arid shrublands. Here we use soil and terrain data and a numerical model of overland flow on semi-arid hillslopes to show that microtopography can generate spatial variations in the dominance of transport processes operating at different timescales, with consequences for the direction of resource redistribution between functional units within these ecosystems. Conceptual and numerical models of the redistribution of mineral, organic and water have mostly been developed on low-gradient alluvial fans and pediments. These have focused on the fluvial transport of resources from the inter-spaces between shrub canopies to the areas below the canopy in those few storm events that generate significant run-off. These processes are believed to produce a mosaic of resource islands in which biota are concentrated. We investigated the spatial distribution of soil properties (including organic matter and soil hydraulic properties), vegetation, and microtopography on two steeper hillslopes of contrasting lithology (one granite, one schist) in the Sonoran desert foothills of the Catalina Mountains. Three hypotheses were developed through iteration between fieldwork and data analysis. These tested whether there were significant differences in soil composition and hydraulic properties below- and between-canopy, whether the surface soil organic matter was directly associated with above-ground biomass, and whether soil organic matter distributions measured along transects below shrubs showed downslope asymmetries indicative of the processes that create them. Data from these sites were used in a numerical model to investigate how these structures could be related to the population of runoff events and processes that generate them. The results suggest that over the long term, slope-dependent transport processes (such as rainsplash, bioturbation and trampling) seem to play an important role in these steeper hillslopes in inverting the flow of resources. Over many storm and inter-storm periods, soil organic matter is transported downslope in plumes extending at least two canopy radii downslope from below woody-shrub canopies into the inter-space. This pattern was particularly evident where microtopography and soil properties create micro-sites protected from fluvial transport. While many of the patterns observed are similar to those from more stable geomorphic surfaces, the results suggest that long-term downslope transport processes in sloping terrain can disrupt the autogenic processes that reinforce the redistribution of resources under shrubs. This result has important implications for our understanding of the relationship between ecosystem function and landscape-scale transport in these environments.

100-kyr fluvial fill terrace cycles since the Middle Pleistocene in the southern Central Andes, Toro Basin, NW Argentina

NASA Astrophysics Data System (ADS)

Tofelde, Stefanie; Schildgen, Taylor F.; Bookhagen, Bodo; Savi, Sara; Pingel, Heiko; Wickert, Andrew D.; Wittmann, Hella; Alonso, Ricardo N.; Strecker, Manfred R.

2017-04-01

Fluvial fill terraces in intermontane basins are valuable sedimentary and geomorphic archives that record tectonic and/or climate- driven changes of river networks and their adjacent hillslopes. However, the rarely complete preservation of such geomorphic features, often combined with large distances from sediment source areas, complicates the identification of causal links between tectonic/climatic forcing mechanisms and landscape response, especially over timescales of 105 to 106 years. The intermontane Quebrada del Toro Basin in the Eastern Cordillera of NW Argentina contains at least five fluvial terrace-surface remnants that have been sculpted into a succession of several-hundred-meter-thick Quaternary gravel conglomerate. These terraces can be followed over several tens of kilometers and are located in the higher part of the basin, close to the sediment source areas. In this study, we determined the onset of multiple river incision phases by dating the abandonment of the three most extensive and best preserved terrace surfaces with nine cosmogenic 10Be-depth profiles. The timing of terrace-gravel deposition is based on four cosmogenic 26Al/10Be burial ages and U-Pb zircon age estimates of three intercalated volcanic ashes in the conglomeratic fill. The 10Be depth profile ages suggest a successive abandonment of these terrace surfaces with a 100-kyr-cyclicity between 487 ± 34 ka and 75 ± 7 ka. Depositional ages of the conglomerates, determined by 26Al/10Be burial samples and U-Pb zircon ages, range from 936 ± 170 ka to 18 ± 141ka. They show a clear overlap with the terrace-surface abandonment ages and thus indicate the existence of multiple cut-and-fill cycles. Although the initial onset of aggradation of the Quaternary gravel conglomerate at ˜1 Ma and the overall net fluvial incision since ˜0.5 Ma can be linked to tectonic processes affecting the narrow basin outlet, the superimposed 100-kyr-cycles of aggradation and incision are best explained by eccentricity-driven climate change. Within these cycles, the onset of river incision can be correlated with global cold periods that are linked with regional humid phases recorded on the Bolivian Altiplano, 1000 km north of the Toro Basin. Deposition, on the other hand, occurs mainly during more arid conditions on the Altiplano (regional) and global interglacial periods. We suggest that enhanced runoff during global cold phases - due to increased regional precipitation, reduced evapotranspiration, or both - resulted in increased sediment-transport capacity in the Toro Basin, which outweighed any possible increases in upstream sediment supply and thus triggered incision. On the other hand during arid phases, the river runoff decreases and the still high sediment supply rates result in overall aggradation. Although located far from major ice-sheets, our study shows that global eccentricity-driven glacial-interglacial cycles also result in significant variations in the sediment-transport system in high mountains of the sub-tropics.

Geomorphic and geologic evidence for slip along the San Bernardino strand of the San Andreas Fault System through the San Gorgonio Pass structural knot, southern California

NASA Astrophysics Data System (ADS)

Kendrick, K. J.; Matti, J. C.

2017-12-01

The San Gorgonio Pass (SGP) region of southern California represents an extraordinarily complex section of the San Andreas Fault (SAF) zone, often referred to as a structural knot. Complexity is expressed both structurally and geomorphically, and arises because multiple strands of the SAF have evolved here in Quaternary time. Our integration of geologic and geomorphic analyses led to recognition of multiple fault-bounded blocks characterized by crystalline rocks that have similar physical properties. Hence, any morphometric differences in hypsometric analysis, slope, slope distribution, texture, and stream-power measurements and discontinuities reflect landscape response to tectonic processes rather than differences in lithology. We propose that the differing morphometry of the two blocks on either side of the San Bernardino strand (SBS) of the SAF, the high-standing Kitching Peak block to the east and the lower, more subdued Pisgah Peak block to the west, strongly suggests that the blocks experienced different uplift histories. This difference in uplift histories, in turn suggests that dextral slip occurred over a long time interval on the SBS—despite long-lived controversy raised by the fact that, at the surface, a throughgoing trace of the SBS is not present at this location. A different tectonic history between the two blocks is consistent with the gravity data which indicate that low-density rocks underthrusting the Kitching Peak block are absent below the Pisgah Peak block (Langenheim et al., 2015). Throughgoing slip on the SBS implied by geomorphic differences between the two blocks is also consistent with displaced geologic and geomorphic features. We find compelling evidence for discrete offsets of between 0.6 and 6 km of dextral slip on the SBS, including offset of fluvial and landslide deposits, and beheaded drainages. Although we lack numerical age control for the offset features, the degree of soil development associated with displaced landforms suggests that the SBS has had a longer geologic history than previously proposed, and that this fault strand may have experienced episodic activity. Landscape evolution and geologic evidence together require that dextral slip on the SAF must have continued through the SGP structural knot during an extended interval in the past.

On the Application of an Enthalpy Method to the Evolution of Fluvial Deltas Under Sea-Level Changes

NASA Astrophysics Data System (ADS)

Anderson, W.; Lorenzo-Trueba, J.; Voller, V. R.

2017-12-01

Fluvial deltas are composites of two primary sedimentary environments: a depositional fluvial region and an offshore region. The fluvial region is defined by two geomorphic moving boundaries: an alluvial-bedrock transition (ABT), which separates the sediment prism from the non-erodible bedrock basement, and the shoreline (SH), where the delta meets the ocean. The trajectories of these boundaries in time and space define the evolution of the shape of the sedimentary prism, and are often used as stratigraphic indicators, particularly in seismic studies, of changes in relative sea level and the identification of stratigraphic sequences. In order to better understand the relative role of sea-level variations, tectonics, and sediment supply on the evolution of these boundaries, we develop a forward stratigraphic model that captures the dynamic behavior of the fluvial surface and treats the SH and ABT as moving boundaries (i.e., internal boundaries whose location must be determined as part of the solution to the overall morphological evolution problem). This forward model extends a numerical technique from heat transfer (i.e., enthalpy method), previously applied to the evolution of sedimentary basins, to account for sea-level changes. The mathematics of the approach are verified by comparing predictions from the numerical model with both existing and newly developed closed form analytical solutions. Model results support previous work, which suggests that the migration of the ABT can respond very differently to the sea-level signal. This response depends on factors such as sediment supply and delta length, which can vary greatly between basins. These results can have important implications for the reconstruction of past sea-level changes from the stratigraphic record of sedimentary basins.

A new surface-process model for landscape evolution at a mountain belt scale

NASA Astrophysics Data System (ADS)

Willett, Sean D.; Braun, Jean; Herman, Frederic

2010-05-01

We present a new surface process model designed for modeling surface erosion and mass transport at an orogenic scale. Modeling surface processes at a large-scale is difficult because surface geomorphic processes are frequently described at the scale of a few meters, and such resolution cannot be represented in orogen-scale models operating over hundreds of square kilometers. We circumvent this problem by implementing a hybrid numerical -- analytical model. Like many previous models, the model is based on a numerical fluvial network represented by a series of nodes linked by model rivers in a descending network, with fluvial incision and sediment transport defined by laws operating on this network. However we only represent the largest rivers in the landscape by nodes in this model. Low-order rivers and water divides between large rivers are determined from analytical solutions assuming steady-state conditions with respect to the local river channel. The analytical solution includes the same fluvial incision law as the large rivers and a channel head with a specified size and mean slope. This permits a precise representation of the position of water divides between river basins. This is a key characteristic in landscape evolution as divide migration provides a positive feedback between river incision and a consequent increase in drainage area. The analytical solution also provides an explicit criterion for river capture, which occurs once a water divide migrates to its neighboring channel. This algorithm avoids the artificial network organization that often results from meshing and remeshing algorithms in numerical models. We demonstrate the use of this model with several simple examples including uniform uplift of a block, simultaneous uplift and shortening of a block, and a model involving strike slip faulting. We find a strong dependence on initial condition, but also a surprisingly strong dependence on channel head height parameters. Low channel heads, as expected, lead to more fluvial capture, but with low initial relief initial and a small channel-head height, runaway capture is common, with a few rivers capturing much of the available drainage area. With larger channel-head relief, lateral capture of rivers is less common, resulting in evenly spaced river basins. Basin spacing ratios matching those observed in nature are obtained for specific channel head parameters. These models thus demonstrate the mixed control on basin characteristics by antecedent river networks and channel-head parameters, which control the mobility of drainage basin water divides.

Do deglaciated mountainslopes contribute significantly to paraglacial sediment fluxes?

NASA Astrophysics Data System (ADS)

Cossart, Etienne

2013-04-01

Current models of paraglacial sediment generation and transport (Ballantyne, 2002 & 2003) are general in nature; they are probably inaccurate for many specific locations because of the wide range in local or regional geomorphic conditions encountered around the globe. One of the conditions that varies from place to place is the pattern of paraglacial landsliding; it varies in both the magnitude, scale, and timing, and therefore has variable influence on sediment generation. Another condition that varies is the sediment connectivity between slopes and the fluvial system; this can vary due to differences in topography, hydrologic regimes, or transient sediment buffers such as landslide dams. In this paper, we examine the extent to which variability in paraglacial landslide patterns and sediment connectivity may affect the applicability of the general paraglacial model. To achieve this we draw on both existing literature and our field experience from the European Alps and Iceland. Sediment generation and pathways, as influenced by post-glacial collapse of mountain slopes in particular, are studied in three steps. First, the processes involved in rock failure are identified and their possible influence on mass-movement locations at different spatial scales in various places is discussed. This comparison reveals a variable pattern of paraglacial landslide distribution, and allows the local/regional controlling parameters to be identified. Second, the rate of triggering of mass-movement over time is roughly assessed in various settings based on a review of recently published data. This comparison aims to identify typical temporal-models for slope evolution through the time elapsed since deglaciation. Third, an attempt is made to assess the contribution of landsliding to the whole paraglacial cascading system by evaluating the somewhat contradictory findings and assertions from previous authors: Some authors have argued for a high sediment yield at catchment sinks in relation to paraglacial landsliding (Church & Ryder, 1972; Ritter & Ten Brink, 1986), whereas others have identified that some long-lived sediment dams can occur after the deposition of a landslide mass, so that no or little sediment exportation occurs (Korup, 2009; Cossart & Fort, 2008). We add to this debate by developing a typology of geomorphic couples, between paraglacial landslides and other geomorphic processes, and present simulations of sediment yield evolution since glacier disappearance. BALLANTYNE C.K., 2002 - A general model of paraglacial landscape response. The Holocene, 12, 371-376. BALLANTYNE C.K., 2003 - Paraglacial landform succession and sediment storage in deglaciated mountain valleys: theory and approaches to calibration. Zeitschrift für Geomorphologie, 32, 1-18. CHURCH M., & RYDER J.M., 1972 - Paraglacial sedimentation: a consideration of fluvial processes conditioned by glaciation. Geological Society of America Bulletin, 83, 3059-3072. COSSART É., & FORT M., 2008 - Sediment release and storage in early deglaciated areas: Towards an application of the exhaustion model from the case of Massif des Écrins (French Alps) since the Little Ice Age. Norsk Geografisk Tidsskrift - Norwegian Journal of Geography, 62, 115-131. KORUP O., 2009 - Linking landslides, hillslope erosion, and landscape evolution. Earth Surface Processes and Landforms, 34, 1315-1317. RITTER D.F., & TEN BRINK N.W., 1986 - Alluvial fan development and the glacial-glaciofluvial cycle. Nenana Valley, Alaska. Journal of Geology, 94, 613-615.

Sediment tracing by `customised' magnetic fingerprinting: from the sub-catchment to the ocean scale

NASA Astrophysics Data System (ADS)

Maher, B.

2009-04-01

Robust identification of catchment suspended sediment sources is a prerequisite both for understanding sediment delivery processes and targeting of effective mitigation measures. Fine sediment delivery can pose management problems, especially with regard to nutrient run-off and siltation of water courses and bodies. Suspended sediment load constitutes the dominant mode of particulate material loss from catchments but its transport is highly episodic. Identification of suspended sediment sources and fluxes is therefore a prerequisite both for understanding of fluvial geomorphic process and systems and for designing strategies to reduce sediment transport, delivery and yields. Here will be discussed sediment ‘fingerprinting', using the magnetic properties of soils and sediments to characterise sediment sources and transport pathways over a very wide variety of spatial scales, from Lake Bassenthwaite in the English Lake District to the Burdekin River in Queensland and even the North Atlantic Ocean during the last glacial maximum. The applicability of magnetic ‘fingerprinting' to such a range of scales and environments has been significantly improved recently through use of new and site-appropriate magnetic measurement techniques, statistical processing and sample treatment options.

Geomorphology and the Restoration Ecology of Salmon

NASA Astrophysics Data System (ADS)

Montgomery, D. R.

2005-05-01

Natural and anthropogenic influences on watershed processes affect the distribution and abundance of salmon across a wide range of spatial and temporal scales, from differences in species use and density between individual pools and riffles to regional patterns of threatened, endangered, and extinct runs. The specific impacts of human activities (e.g., mining, logging, and urbanization) vary among regions and watersheds, as well as between different channel reaches in the same watershed. Understanding of both disturbance history and key biophysical processes are important for diagnosing the nature and causes of differences between historical and contemporary fluvial and watershed conditions based on evaluation of both historical and spatial contexts. In order to be most effective, the contribution of geomorphologic insight to salmon recovery efforts requires both assessment protocols commensurate with providing adequate knowledge of historical and spatial context, and experienced practitioners well versed in adapting general theory to local settings. The historical record of salmon management in Europe, New England and the Pacific Northwest indicates that there is substantial need to incorporate geomorphic insights on the effects of changes in watershed processes on salmon habitat and salmon abundance into salmon recovery efforts.

The efficacy of stream power and flow duration on geomorphic responses to catastrophic flooding

NASA Astrophysics Data System (ADS)

Magilligan, F. J.; Buraas, E. M.; Renshaw, C. E.

2015-01-01

Geomorphologists have long studied the impacts of extreme floods, yet the association between the magnitude of flow parameters (discharge, velocity, shear stress, or stream power) and resulting geomorphic effectiveness remains vague and non-deterministic. Attempts have been made to include flow duration and total expenditure of stream power, in combination with peak unit stream power, as important variables, but there has been minimal exploration of this hydraulic combination. Taking advantage of Tropical Storm Irene's rapid track through eastern Vermont (USA) in late summer 2011, this paper presents the array of geomorphic responses to a short duration (time to peak of < 8 h) but high magnitude flood that was the twentieth century flood of record for numerous watersheds. We present herein the geomorphic imprint of Tropical Storm Irene flooding within a larger context of fluvial theory concerning the role of, and trade-off between, the magnitude of energy expenditure during a flood and its duration. Focusing on a detailed field effort within the 187-km2 Saxtons River basin in southeastern VT, augmented by select sites along the adjacent lower gradient Williams River (291-km2), we elucidate (1) the geomorphic effects of a short duration flood in a humid, well-vegetated landscape; (2) the relationship between geomorphic response and (a) peak stream power, (b) total stream power, and (c) flow duration of stream power above a critical threshold; and (3) the spatial variation of geomorphic effects relative to reach-scale geologic and geomorphic controls. Flooding associated with Tropical Storm Irene ranged from the 1000 year recurrence interval (RI) flood (based on Weibull flood frequency analysis) to the 300 year RI flood (log Pearson Type III). Discharges spawned a peak unit stream power of 712 W/m2 (Saxtons River) and 361 W/m2 (Williams River), with total energy expenditure throughout the event of ~ 16,000 × 103 and 15,000 × 103 J, respectively. For the Saxtons River, channel widening was spatially infrequent and limited in magnitude; however, other geomorphic effects were profound (1) the entrainment, transport, and deposition of extremely coarse material; (2) stripping of floodplain surfaces; (3) channel avulsions and incision into Pleistocene-aged material; and (4) deposition of coarse material across floodplains. Based on our extensive field data and hydrologic/hydraulic analyses, we contend that short duration, high energy flows can have profound sedimentological effects but have limited erosive, channel widening impacts. Gravel entrainment and deposition of a catastrophic nature can certainly occur under these flow regimes, but the impacts of these extreme flows on channel geometry may have limited expression.

High Resolution Mapping and Interpretation of Channel and Floodplain Topography With a Narrow-Beam Terrestrial-Aquatic Lidar

NASA Astrophysics Data System (ADS)

McKean, J.; Isaak, D.; Tonina, D.; Wright, W.; Kinzel, P.

2007-12-01

Basic description of channel and floodplain topography remains a fundamental challenge for modeling flow and sediment transport or even simply mapping habitat. Standard field wading and boat surveys of stream topography are limited by costs and logistics to relatively small sample reaches and floodplain maps are seldom well- integrated with channel bathymetry. We used the NASA Experimental Advanced Airborne Research Lidar (EAARL) to map channel and floodplain topography and investigate geomorphic controls on physical habitat in two diverse channels in the watershed of the Middle Fork Salmon River, Idaho. Bear Valley Creek is a small low-gradient gravel-bed stream flowing across an unconfined valley filled with glacial outwash materials. A hierarchy of nested geomorphic features is evident in this channel with the broadest fluvial domains a legacy of ~15,000 years of post-glacial valley evolution. Contemporary hydraulics operate on this broad template and control two smaller scales of pool-riffle morphology. Salmon spawning patterns closely reflect these nested physical domains, demonstrating how geomorphic history can influence modern distributions of aquatic habitat and organisms. In contrast, Big Creek is a higher-gradient stream predominately confined by steep side slopes in a deep valley. Here, the distribution of geomorphic domains and physical habitat is controlled by modern erosion processes and rock quality. Tributaries and valley walls contribute coarse debris, up to large boulders, to the channel, resulting in very rough and poorly organized bed topography. Tributary fans also function as local grade control with sediment deposition in lower-gradient reaches upstream of fans. A GIS toolkit is under development to extract at-a-station channel metrics from EAARL data, including for example, cross section and longitudinal profile characteristics. A new investigation has also begun to further investigate the quality of EAARL data. This study will explore the question of how well we must describe channel topography to adequately: i) map the spatial distribution of physical habitat for management purposes and in support of organism population growth models, and ii) define boundary conditions for flow and sediment transport predictions using the USGS model MD SWMS.

The Use of a Geomorphometric Classification to Estimate Subsurface Heterogeneity in the Unconsolidated Sediments of Mountain Watersheds

NASA Astrophysics Data System (ADS)

Cairns, D.; Byrne, J. M.; Jiskoot, H.; McKenzie, J. M.; Johnson, D. L.

2013-12-01

Groundwater controls many aspects of water quantity and quality in mountain watersheds. Groundwater recharge and flow originating in mountain watersheds are often difficult to quantify due to challenges in the characterization of the local geology, as subsurface data are sparse and difficult to collect. Remote sensing data are more readily available and are beneficial for the characterization of watershed hydrodynamics. We present an automated geomorphometric model to identify the approximate spatial distribution of geomorphic features, and to segment each of these features based on relative hydrostratigraphic differences. A digital elevation model (DEM) dataset and predefined indices are used as inputs in a mountain watershed. The model uses periglacial, glacial, fluvial, slope evolution and lacustrine processes to identify regions that are subsequently delineated using morphometric principles. A 10 m cell size DEM from the headwaters of the St. Mary River watershed in Glacier National Park, Montana, was considered sufficient for this research. Morphometric parameters extracted from the DEM that were found to be useful for the calibration of the model were elevation, slope, flow direction, flow accumulation, and surface roughness. Algorithms were developed to utilize these parameters and delineate the distributions of bedrock outcrops, periglacial landscapes, alluvial channels, fans and outwash plains, glacial depositional features, talus slopes, and other mass wasted material. Theoretical differences in sedimentation and hydrofacies associated with each of the geomorphic features were used to segment the watershed into units reflecting similar hydrogeologic properties such as hydraulic conductivity and thickness. The results of the model were verified by comparing the distribution of geomorphic features with published geomorphic maps. Although agreement in semantics between datasets caused difficulties, a consensus yielded a comparison Dice Coefficient of 0.65. The results can be used to assist in groundwater model calibration, or to estimate spatial differences in near-surface groundwater behaviour. Verification of the geomorphometric model would be augmented by evaluating its success after use in the calibration of the groundwater simulation. These results may also be used directly in momentum-based equations to create a stochastic routing routine beneath the soil interface for a hydrometeorological model.

Quantification of Fluvial Response to Tectonic Deformation and Climate in the Central Pontides, Turkey; Inferences from OSL Dating of Fluvial Terraces

NASA Astrophysics Data System (ADS)

McClain, K.; Yildirim, C.; Çiner, A.; Sahin, S.; Sarıkaya, A.; Ozturk, T.; Kıyak, N. G.; Ozcan, O.

2016-12-01

This study intends to improve the understanding of the topographic evolution and fluvial processes responding to tectonics and climate within the high-relief and deeply-incised Karabük Range of the Central Pontides, a large transpressional wedge at the northern margin of the Central Anatolian Plateau. Insight into these interactions can be obtained through the dating of fluvial sediment and understanding of geomorphic features. From Late Miocene to present, Anatolia's rapid counterclockwise movement, which increases in velocity towards the Hellenic Arc, has formed the North Anatolian Fault (NAF), a dextral transform fault along the Anatolia-Eurasia boundary. North of the transpressional zone of the NAF's massive restraining bend, an area that had experienced previous uplift due to the closure of the Intra-Pontide Ocean, the landscape experienced further uplift and the development of a detached flower structure. In the west side of this zone of transpression, the Filyos River deeply incises a gorge while bisecting the Karabük Range. This created an area with an abundance of indicators of tectonic deformation to map, such as hanging valleys, wind gaps, bedrock gorges, landslides, steep v-shaped channels, as well as an abundance of fluvial strath terraces. In particular, the village of Bolkuş lies among strath terraces of at least 8 ages within just 1.5 km of horizontal distance. In Bolkuş, we used optically stimulated luminescence dating (OSL dating) to estimate five deposition ages of fluvial strath terrace sediment, or their last exposure to daylight, leading to an estimation of incision and uplift rates over time. After collecting three samples from each terrace, with strath elevations of 246, 105.49, 43.6, 15.3 and 3.6 m.a.s.l., we determined corresponding ages of 841 ±76, 681 ±49, 386 ±18, 88 ±5.1 and 50.9 ±2.8 ka. These ages are older than expected for an area of active vertical deformation. Incision rates over time (highest/oldest terrace to lowest/youngest) suggest uplift of 0.29, 0.15, 0.12, 0.17 and 0.07 mm/y. When compared to the mean 0.06 mm/y uplift rate of the Central Anatolian Plateau, the results suggest not only that uplift has slowed, but that the restraining bend transpression of the NAF may no longer cause vertical deformation at this location within the Central Pontides.

Estimating Earthquake Magnitude from the Kentucky Bend Scarp in the New Madrid Seismic Zone Using Field Geomorphic Mapping and High-Resolution LiDAR Topography

NASA Astrophysics Data System (ADS)

Kelson, K. I.; Kirkendall, W. G.

2014-12-01

Recent suggestions that the 1811-1812 earthquakes in the New Madrid Seismic Zone (NMSZ) ranged from M6.8-7.0 versus M8.0 have implications for seismic hazard estimation in the central US. We more accurately identify the location of the NW-striking, NE-facing Kentucky Bend scarp along the northern Reelfoot fault, which is spatially associated with the Lake County uplift, contemporary seismicity, and changes in the Mississippi River from the February 1812 earthquake. We use 1m-resolution LiDAR hillshades and slope surfaces, aerial photography, soil surveys, and field geomorphic mapping to estimate the location, pattern, and amount of late Holocene coseismic surface deformation. We define eight late Holocene to historic fluvial deposits, and delineate younger alluvia that are progressively inset into older deposits on the upthrown, western side of the fault. Some younger, clayey deposits indicate past ponding against the scarp, perhaps following surface deformational events. The Reelfoot fault is represented by sinuous breaks-in-slope cutting across these fluvial deposits, locally coinciding with shallow faults identified via seismic reflection data (Woolery et al., 1999). The deformation pattern is consistent with NE-directed reverse faulting along single or multiple SW-dipping fault planes, and the complex pattern of fluvial deposition appears partially controlled by intermittent uplift. Six localities contain scarps across correlative deposits and allow evaluation of cumulative surface deformation from LiDAR-derived topographic profiles. Displacements range from 3.4±0.2 m, to 2.2±0.2 m, 1.4±0.3 m, and 0.6±0.1 m across four progressively younger surfaces. The spatial distribution of the profiles argues against the differences being a result of along-strike uplift variability. We attribute the lesser displacements of progressively younger deposits to recurrent surface deformation, but do not yet interpret these initial data with respect to possible earthquake magnitudes. Additional efforts hopefully will address shallow subsurface evidence of single- or multiple-deformational events at selected localities.

Geomorphic response to large-dam removal: Impacts of a massive sediment release to the Elwha River, Washington

NASA Astrophysics Data System (ADS)

Magirl, C. S.; Ritchie, A.; Bountry, J.; Randle, T. J.; East, A. E.; Hilldale, R. C.; Curran, C. A.; Pess, G. R.

2015-12-01

The 2011-2014 staged removals of two nearly century-old dams on the Elwha River in northwest Washington State, the largest dam-removal project in the United States, exposed 21 million m3 of reservoir-trapped sand and gravel to potential fluvial transport. The river downstream from the dams is gravel bedded with a pool-riffle morphology. The river flows 20 km to the marine environment through a riparian corridor lined with large wood and having relatively few anthropogenic alterations. This moderately natural pre-dam-removal condition afforded an unprecedented opportunity to study river response to an anticipated massive sediment release. Four years into the project, 12 million m3 of sediment eroded from the former reservoirs with about 90% of the total load transported to the marine environment. Annualized sediment discharge was as great as 20 times the background natural load. Initial river response to the arrival of the first large sediment pulse was the nearly complete filling of the river's previously sediment-starved pools, widespread filling of side channels, and increased braiding index. In year 2, during maximum aggradation, the river graded to a plane-bedded system, efficiently conveying sediment to the marine environment. Modest peak flows (<2-yr return period) in year 2 promoted sediment transport but caused little large-scale geomorphic disturbance by channel migration or avulsions. As the river processed the sediment pulse, pools returned and the braiding index decreased in years 3-4. Higher peak flows in year 4 caused localized channel widening and migration but no major avulsions. Gauging indicated sand dominated the first stages of sediment release, but fluvial loads coarsened through time with progressive arrival of larger material. The literature suggests the Elwha River sediment wave should have evolved through dispersion with little translation. However, morphologic measurements and data from a stage-gauge network indicated patterns of deposition, sediment transport, and sediment-wave evolution were heterogeneously complex, challenging our efforts to classify the sediment wave in terms of simple dispersion or translation.

A field experiment on the controls of sediment transport on bedrock erosion

NASA Astrophysics Data System (ADS)

Beer, A. R.; Turowski, J. M.; Fritschi, B.; Rieke-Zapp, D.; Campana, L.; Lavé, J.

2012-12-01

The earth`s surface is naturally shaped by interactions of physical and chemical processes. In mountainous regions with steep topography river incision fundamentally controls the geomorphic evolution of the whole landscape. There, erosion of exposed bedrock sections by fluvial sediment transport is an important mechanism forming mountain river channels. The links between bedload transport and bedrock erosion has been firmly established using laboratory experiments. However, there are only few field datasets linking discharge, sediment transport, impact energy and erosion that can be used for process understanding and model evaluation. To fill this gap, a new measuring setup has been commissioned to raise an appropriate simultaneous dataset of hydraulics, sediment transport and bedrock erosion at high temporal and spatial resolution. Two natural stone slabs were installed flush with the streambed of the Erlenbach, a gauged stream in the Swiss Pre-Alps. They are mounted upon force sensors recording vertical pressure und downstream shear caused by passing sediment particles. The sediment transport rates can be assessed using geophone plates and an automated moving basket system taking short-term sediment samples. These devices are located directly downstream of the stone slabs. Bedrock erosion rates are measured continuously with erosion sensors at sub-millimeter accuracy at three points on each slab. In addition, the whole slab topography is surveyed with photogrammetry and a structured-light 3D scanner after individual flood events. Since the installation in 2011, slab bedrock erosion has been observed during several transport events. We discuss the relation between hydraulics, bedload transport, resulting pressure forces on the stone slabs and erosion rates. The aim of the study is the derivation of an empirical process law for fluvial bedrock erosion driven by moving sediment particles.

Collection, processing and error analysis of Terrestrial Laser Scanning data from fluvial gravel surfaces

NASA Astrophysics Data System (ADS)

Hodge, R.; Brasington, J.; Richards, K.

2009-04-01

The ability to collect 3D elevation data at mm-resolution from in-situ natural surfaces, such as fluvial and coastal sediments, rock surfaces, soils and dunes, is beneficial for a range of geomorphological and geological research. From these data the properties of the surface can be measured, and Digital Terrain Models (DTM) can be constructed. Terrestrial Laser Scanning (TLS) can collect quickly such 3D data with mm-precision and mm-spacing. This paper presents a methodology for the collection and processing of such TLS data, and considers how the errors in this TLS data can be quantified. TLS has been used to collect elevation data from fluvial gravel surfaces. Data were collected from areas of approximately 1 m2, with median grain sizes ranging from 18 to 63 mm. Errors are inherent in such data as a result of the precision of the TLS, and the interaction of factors including laser footprint, surface topography, surface reflectivity and scanning geometry. The methodology for the collection and processing of TLS data from complex surfaces like these fluvial sediments aims to minimise the occurrence of, and remove, such errors. The methodology incorporates taking scans from multiple scanner locations, averaging repeat scans, and applying a series of filters to remove erroneous points. Analysis of 2.5D DTMs interpolated from the processed data has identified geomorphic properties of the gravel surfaces, including the distribution of surface elevations, preferential grain orientation and grain imbrication. However, validation of the data and interpolated DTMs is limited by the availability of techniques capable of collecting independent elevation data of comparable quality. Instead, two alternative approaches to data validation are presented. The first consists of careful internal validation to optimise filter parameter values during data processing combined with a series of laboratory experiments. In the experiments, TLS data were collected from a sphere and planes with different reflectivities to measure the accuracy and precision of TLS data of these geometrically simple objects. Whilst this first approach allows the maximum precision of TLS data from complex surfaces to be estimated, it cannot quantify the distribution of errors within the TLS data and across the interpolated DTMs. The second approach enables this by simulating the collection of TLS data from complex surfaces of a known geometry. This simulated scanning has been verified through systematic comparison with laboratory TLS data. Two types of surface geometry have been investigated: simulated regular arrays of uniform spheres used to analyse the effect of sphere size; and irregular beds of spheres with the same grain size distribution as the fluvial gravels, which provide a comparable complex geometry to the field sediment surfaces. A series of simulated scans of these surfaces has enabled the magnitude and spatial distribution of errors in the interpolated DTMs to be quantified, as well as demonstrating the utility of the different processing stages in removing errors from TLS data. As well as demonstrating the application of simulated scanning as a technique to quantify errors, these results can be used to estimate errors in comparable TLS data.

Late Cenozoic flexural deformation of the middle U.S. Atlantic passive margin

NASA Technical Reports Server (NTRS)

Pazzaglia, Frank J.; Gardner, Thomas, W.

1994-01-01

Despite the century-long recognition of regional epeirogeny along the middle Atlantic passive margin, relatively few studies have focused on understanding postrift uplift mechanisms. Here, we demonstrate that epeirogenic uplift of the central Appalachian Piedmont and subsidence of the Salisbury Embayment represent first-order, flexural isostatic processes driven by continental denudation and offshore deposition. Our results show that regional epeirogenic processes, present on all Atlantic-type passive margins, are best resolved by specific stratigraphic and geomorphic relationships, rather than topography. A simple one-dimensional geodynamic model, constrained by well-dated Baltimore Canyon trough, Coastal Plain, and lower Susquehanna River (piedmont) stratigraphy, simulates flexural deforamtion of the U.S. Atlantic margin. The model represents the passive margin lithosphree as a uniformly thick elastic plate, without horizontal compressive stresses, that deforms flexurally under the stress of strike-averaged, vertically applied line loads. Model results illustrate a complex interaction among margin stratigraphy and geomorphology, the isostatic repsonse to denudational and depositional processes, and the modulating influence of exogenic forces such as eustasy. The current elevation, with respect to modern sea level, of fluvial terraces and correlateive Coastal Plain deposits or unconformities is successfully predicted through the synthesis of paleotopography, eustatic change, and margin flexure. Results suggest that the middle U.S. Atlantic margin landward of East Coast Magnetic Anomaly is underlain by lithoshpere with an average elastic thickness of 40 km (flexural rigidity, D = 4 X 10(exp 23) N m), the margin experience an average, long-term denudation rate of approximately 10m/m.y., and the Piedmont has been flexurally upwaped between 35 and 130 meters in the last 15 m.y. Long term isostatic continental uplift resulting rom denudation and basin subsidence resulting rom sediment loading are accomodated primately by a convex-up flexural hinge, physiographically represented by the Fall Zone. Our results elucidate an inherent danger in using topography alone to constrain late-stage passive margin deformation mechanisms. Only through careful synthesis of field stratigraphic and geomorphic elements such as fluvial terraces, Coastal Plain deposits, and offshore stratigraphy can age control be extended from the offshore depositional setting to the erosionally dominated continent. This sudy demonstrates that despite a relatively subdued topography, the middle U.S. Atlantic margin experiences progressive flexural isostatic deformation similar to that proposed for high-relief margins characterized by great escarpments. Thus margin topographic diversity remains a function of other factors, such as lithospheric composition and/or structure, supracrustal stratigraphy and structure, degree of drainage integration, drainage divide migration and climate.

Geomorphic Proxies to Test Strain Accommodation in Southwestern Puerto Rico from Digital Elevation Models

NASA Astrophysics Data System (ADS)

Barrios Galindez, I. M.; Xue, L.; Laó-Dávila, D. A.

2017-12-01

The Puerto Rico and the Virgin Island microplate is located in at the northeastern corner of the Caribbean plate boundary with North America is placed within an oblique subduction zone in which strain patterns remain unresolved. Seismic hazard is a major concern in the region as seen from the seismic history of the Caribbean-North America plate boundary zone. Most of the tectonic models of the microplate show the accommodation of strain occurring offshore, despite evidence from seismic activity, trench studies, and geodetic studies suggesting the existence of strain accomodation in southwest Puerto Rico. These studies also suggest active faulting specially in the western part of the island, but limited work has been done regarding their mechanism. Therefore, this work aims to define and map these active faults in western Puerto Rico by integrating data from analysis of fluvial terrains, and detailed mapping using digital elevation model (DEM) extracted from Shuttle Radar Topography Mission (SRTM) and LIDAR data. The goal is to (1) identify structural features such as surface lineaments and fault scarps for the Cerro Goden fault, South Lajas fault, and other active faults in the western of Puerto Rico, (2) correlate these information with the distribution pattern and values of the geomorphic proxies, including Chi integral (χ), normalized steepness (ksn) and Asymmetric factor (AF). Our preliminary results from geomorphic proxies and Lidar data provide some insight of the displacement and stage of activities of these faults (e.g. Boqueron-Punta Malva Fault and Cerro Goden fault). Also, the anomaly of the geomorphic proxies generally correlate with the locations of the landslides in the southwestern Puerto Rico. The geomorphic model of this work include new information of active faulting fundamental to produce better seismic hazards maps. Additionally, active tectonics studies are vital to issue and adjust construction buildings codes and zonification codes.

Characterizing the transient geomorphic response to base level fall in the northeastern Tibetan Plateau

NASA Astrophysics Data System (ADS)

Zhang, H.; Zhang, P.; Kirby, E.; Pitlick, J.; Anderson, R. S.

2015-12-01

Analyses of hillslope gradient, landscape relief, and channel steepness in the Daxiahe drainage basin along the northeastern margin of the Tibetan Plateau provides evidence of a transient geomorphic response to base level fall along the main stem Yellow River. The upper portions of the watershed are characterized by low-gradient channels and gentle hillslopes and are separated from a steeper, high relief landscape by a series of convex knickzones along channel profiles. Downstream projection of the upper channel profiles implies ~500-600 m of incision, consistent with terrace records of post ~1.7 Ma incision in the Linxia basin. We characterize erosion rates across this transient landscape using both optically-stimulated dating of fluvial terraces and catchment-averaged 10Be concentrations in modern sediment. Both data sets are consistent and suggest erosion/incision rates of ~300 m/Myr below knickpoints and ~50-100 m/Myr above. Field measurements of channel width (n=48) and bankfull discharge (n=9) allow us to determine local scaling relations among channel hydraulic geometry, discharge, and contributing area that we employ to estimate basal shear stress, unit stream power and bedload transport along the main stem of the Daxiahe River. We find a clear downstream increase of incision potential across this transient landscape, consistent with topographic observations and erosion rates. In contrast to recent studies, we find no evidence for adjustment of channel width across the transition from slowly eroding to rapidly eroding portions of the watershed. We hypothesize that this behavior is consistent with detachment-limited models of fluvial incision, despite the presence of significant sediment in channel bed and banks. Our results imply that the controls on hydraulic geometry along actively incising rivers remain incompletely understood.

Mapping process and age of Quaternary deposits on Santa Rosa Island, Channel Islands National Park, California

NASA Astrophysics Data System (ADS)

Schmidt, K. M.; Minor, S. A.; Bedford, D.

2016-12-01

Employing a geomorphic process-age classification scheme, we mapped the Quaternary surficial geology of Santa Rosa (SRI) within the Channel Islands National Park. This detailed (1:12,000 scale) map represents upland erosional transport processes and alluvial, fluvial, eolian, beach, marine terrace, mass wasting, and mixed depositional processes. Mapping was motivated through an agreement with the National Park Service and is intended to aid natural resource assessments, including post-grazing disturbance recovery and identification of mass wasting and tectonic hazards. We obtained numerous detailed geologic field observations, fossils for faunal identification as age control, and materials for numeric dating. This GPS-located field information provides ground truth for delineating map units and faults using GIS-based datasets- high-resolution (sub-meter) aerial imagery, LiDAR-based DEMs and derivative raster products. Mapped geologic units denote surface processes and Quaternary faults constrain deformation kinematics and rates, which inform models of landscape change. Significant findings include: 1) Flights of older Pleistocene (>120 ka) and possibly Pliocene marine terraces were identified beneath younger alluvial and eolian deposits at elevations as much as 275 m above modern sea level. Such elevated terraces suggest that SRI was a smaller, more submerged island in the late Neogene and (or) early Pleistocene prior to tectonic uplift. 2) Structural and geomorphic observations made along the potentially seismogenic SRI fault indicate a protracted slip history during the late Neogene and Quaternary involving early normal slip, later strike slip, and recent reverse slip. These changes in slip mode explain a marked contrast in island physiography across the fault. 3) Many of the steeper slopes are dramatically stripped of regolith, with exposed bedrock and deeply incised gullies, presumably due effects related to past grazing practices. 4) Surface water presence is spatially discontinuous and correlated with major fault traces and geologic unit boundaries.

Late Quaternary stream piracy and strath terrace formation along the Belle Fourche and lower Cheyenne Rivers, South Dakota and Wyoming

USGS Publications Warehouse

Stamm, John F.; Hendricks, Robert R.; Sawyer, J. Foster; Mahan, Shannon; Zaprowski, Brent J.; Geibel, Nicholas M.; Azzolini, David C.

2013-01-01

Stream piracy substantially affected the geomorphic evolution of the Missouri River watershed and drainages within, including the Little Missouri, Cheyenne, Belle Fourche, Bad, and White Rivers. The ancestral Cheyenne River eroded headward in an annular pattern around the eastern and southern Black Hills and pirated the headwaters of the ancestral Bad and White Rivers after ~ 660 ka. The headwaters of the ancestral Little Missouri River were pirated by the ancestral Belle Fourche River, a tributary to the Cheyenne River that currently drains much of the northern Black Hills. Optically stimulated luminescence (OSL) dating techniques were used to estimate the timing of this piracy event at ~ 22–21 ka. The geomorphic evolution of the Cheyenne and Belle Fourche Rivers is also expressed by regionally recognized strath terraces that include (from oldest to youngest) the Sturgis, Bear Butte, and Farmingdale terraces. Radiocarbon and OSL dates from fluvial deposits on these terraces indicate incision to the level of the Bear Butte terrace by ~ 63 ka, incision to the level of the Farmingdale terrace at ~ 40 ka, and incision to the level of the modern channel after ~ 12–9 ka. Similar dates of terrace incision have been reported for the Laramie and Wind River Ranges. Hypothesized causes of incision are the onset of colder climate during the middle Wisconsinan and the transition to the full-glacial climate of the late-Wisconsinan/Pinedale glaciation. Incision during the Holocene of the lower Cheyenne River is as much as ~ 80 m and is 3 to 4 times the magnitude of incision at ~ 63 ka and ~ 40 ka. The magnitude of incision during the Holocene might be due to a combined effect of three geomorphic processes acting in concert: glacial isostatic rebound in lower reaches (~ 40 m), a change from glacial to interglacial climate, and adjustments to increased watershed area resulting from piracy of the ancestral headwaters of the Little Missouri River.

Recently active contractile deformation in the forearc of southern Peru

NASA Astrophysics Data System (ADS)

Hall, S. R.; Farber, D.; Audin, L.; Finkel, R. C.

2010-12-01

In the Precordillera and Western Cordillera of southern Peru (14°-18°S), vast pediment surfaces have been abandoned through drainage diversion and river incision, with the major drainages carving deep canyons. Within this region, we have identified range-sub-parallel contractile structures that accommodate significant distributed crustal deformation. Young geomorphic features document both the presence and youthfulness of these contractile structures. Here, we determine exposure ages on geomorphic features such as pediment surfaces and fluvial terraces using in situ produced cosmogenic radionuclides, in conjunction with field and remote mapping. This chronologic data reveals that ancient surfaces have been preserved as a result of very low erosion rates. We measure this rate to be <0.5m/Ma on genetically similar surfaces spanning over 4 degrees of latitude throughout this region. While many ancient surfaces are preserved in forearc localities, we also observe young (30ka-1Ma) low-relief pediment surfaces modified by recent processes. Specifically, active structures accommodating compressional stresses locally displace active drainages and offset river terraces leading to their abandonment. Based on our chronology and geomorphic mapping, we calculate a Pleistocene river incision rate of ~0.3mm/yr determined from data collected along exoreic rivers. This rate is consistent with longer-term incision rates measured in other localities along this margin. We suggest that, in this region of southern Peru, the steep western wedge of the Andean margin supports the high topography of the Altiplano through a combination of uplift along steeply dipping contractile west-vergent structures and isostatic responses to the focused removal of large amounts of crustal material through canyon incision. Further, that these range sub-parallel structures are related at depth to a thrust system that plays a role in not only the maintenance of the Andean margin, but potentially in its formation as well.

Late Quaternary stream piracy and strath terrace formation along the Belle Fourche and lower Cheyenne Rivers, South Dakota and Wyoming

NASA Astrophysics Data System (ADS)

Stamm, John F.; Hendricks, Robert R.; Sawyer, J. Foster; Mahan, Shannon A.; Zaprowski, Brent J.; Geibel, Nicholas M.; Azzolini, David C.

2013-09-01

Stream piracy substantially affected the geomorphic evolution of the Missouri River watershed and drainages within, including the Little Missouri, Cheyenne, Belle Fourche, Bad, and White Rivers. The ancestral Cheyenne River eroded headward in an annular pattern around the eastern and southern Black Hills and pirated the headwaters of the ancestral Bad and White Rivers after ~ 660 ka. The headwaters of the ancestral Little Missouri River were pirated by the ancestral Belle Fourche River, a tributary to the Cheyenne River that currently drains much of the northern Black Hills. Optically stimulated luminescence (OSL) dating techniques were used to estimate the timing of this piracy event at ~ 22-21 ka. The geomorphic evolution of the Cheyenne and Belle Fourche Rivers is also expressed by regionally recognized strath terraces that include (from oldest to youngest) the Sturgis, Bear Butte, and Farmingdale terraces. Radiocarbon and OSL dates from fluvial deposits on these terraces indicate incision to the level of the Bear Butte terrace by ~ 63 ka, incision to the level of the Farmingdale terrace at ~ 40 ka, and incision to the level of the modern channel after ~ 12-9 ka. Similar dates of terrace incision have been reported for the Laramie and Wind River Ranges. Hypothesized causes of incision are the onset of colder climate during the middle Wisconsinan and the transition to the full-glacial climate of the late-Wisconsinan/Pinedale glaciation. Incision during the Holocene of the lower Cheyenne River is as much as ~ 80 m and is 3 to 4 times the magnitude of incision at ~ 63 ka and ~ 40 ka. The magnitude of incision during the Holocene might be due to a combined effect of three geomorphic processes acting in concert: glacial isostatic rebound in lower reaches (~ 40 m), a change from glacial to interglacial climate, and adjustments to increased watershed area resulting from piracy of the ancestral headwaters of the Little Missouri River.

Evidence for precipitation on Mars from dendritic valleys in the Valles Marineris area.

PubMed

Mangold, Nicolas; Quantin, Cathy; Ansan, Véronique; Delacourt, Christophe; Allemand, Pascal

2004-07-02

Dendritic valleys on the plateau and canyons of the Valles Marineris region were identified from Thermal Emission Imaging System (THEMIS) images taken by Mars Odyssey. The geomorphic characteristics of these valleys, especially their high degree of branching, favor formation by atmospheric precipitation. The presence of inner channels and the maturity of the branched networks indicate sustained fluid flows over geologically long periods of time. These fluvial landforms occur within the Late Hesperian units (about 2.9 to 3.4 billion years old), when Mars was thought to have been cold. Our results suggest a period of warmer conditions conducive to hydrological activity.

Yangon River Geomorphology Identification and its Enviromental Imapacts Analsysi by Optical and Radar Sensing Techniques

NASA Astrophysics Data System (ADS)

Lwin, A.; Khaing, M. M.

2012-07-01

The Yangon river, also known as the Rangoon river, is about 40 km long (25miles), and flows from southern Myanmar as an outlet of the Irrawaddy (Ayeyarwady) river into the Ayeyarwady delta. The Yangon river drains the Pegu Mountains; both the Yangon and the Pathein rivers enter the Ayeyarwady at the delta. Fluvial geomorphology is based primarily on rivers of manageable dimensions. The emphasis is on geomorphology, sedimentology of Yangon river and techniques for their identification and management. Present techniques such as remote sensing have made it easier to investigate and interpret in details analysis of river geomorphology. In this paper, attempt has been made the complicated issues of geomorphology, sedimentation patterns and management of river system and evolution studied. The analysis was carried out for the impact of land use/ land cover (LULC) changes on stream flow patterns. The hydrologic response to intense, flood producing rainfall events bears the signatures of the geomorphic structure of the channel network and of the characteristic slope lengths defining the drainage density of the basin. The interpretation of the hydrologic response as the travel time distribution of a water particle randomly injected in a distributed manner across the landscape inspired many geomorphic insights. In 2008, Cyclone Nargis was seriously damaged to mangrove area and its biodiversity system in and around of Yangon river terraces. A combination of digital image processing techniques was employed for enhancement and classification process. It is observed from the study that middle infra red band (0.77mm - 0.86mm) is highly suitable for mapping mangroves. Two major classes of mangroves, dense and open mangroves were delineated from the digital data.

Quantifying the scale- and process- dependent reorganization of landscape under climatic change: inferences from an experimental landscape

NASA Astrophysics Data System (ADS)

Singh, A.; Tejedor, A.; Grimaud, J. L.; Zaliapin, I. V.; Foufoula-Georgiou, E.

2016-12-01

Knowledge of the dynamics of evolving landscapes in terms of their geomorphic and topologic re-organization in response to changing climatic or tectonic forcing is of scientific and practical interest. Although several studies have addressed the large-scale response (e.g., change in mean relief), studies on the smaller-scale drainage pattern re-organization and quantification of landscape vulnerability to the timing, magnitude, and frequency of changing forcing are lacking. The reason is the absence of data for such an analysis. To that goal, a series of controlled laboratory experiments were conducted at the St. Anthony Falls laboratory of the University of Minnesota to study the effect of changing precipitation patterns on landscape evolution at the short and long-time scales. High resolution digital elevation (DEM) both in space and time were measured for a range of rainfall patterns and uplift rates. Results from our study show a distinct signature of the precipitation increase on the probabilistic and geometrical structure of landscape features, evident in widening and deepening of channels and valleys, change in drainage patterns within sub-basins and change in the space-time structure of erosional and depositional events. A spatially explicit analysis of the locus of these erosional and depositional events suggests a regime shift, during the onset of the transient state, from supply-limited to transport-limited fluvial channels. We document a characteristic scale-dependent signature of erosion at steady state (which we term the "E50-area curve") and show that during reorganization, its evolving shape reflects process and scales of geomorphic change. Finally, we document changes in the longitudinal river profiles, in response to increased precipitation rate, with the formation of abrupt gradient (knickpoints) that migrate upstream as time proceeds.

Geomorphic Change Induced by 100 years of Flow Alteration on the Diamond Fork River, Central Utah

NASA Astrophysics Data System (ADS)

Jones, J.; Belmont, P.; Wilcock, P. R.

2017-12-01

Changes in hydrology and sediment supply affect the form of rivers. The rate of change of fluvial form is controlled by a variety of factors, including valley confinement, sediment size, and antecedent condition. The Diamond Fork River in central Utah has been altered by trans-basin flows delivered from the Colorado River system for over a century. Beginning in 1915, water used for irrigation was delivered through a tributary, Sixth Water Creek, with daily summer flows regularly exceeding the 50 - 100 year flood. Elevated flows caused drastic geomorphic change - resulting in incision and widening of the channel, and the destruction of riparian vegetation. Beginning in 1997, the outlet for the trans-basin diversion was moved downstream on Sixth Water, bypassing a large landslide, and flows were drastically reduced in 2004 through management actions. We delineated eight distinct process domains for the Sixth Water-Diamond Fork system and examined the response of each process domain to the altered flow and sediment regimes through the analysis of aerial photographs and repeat cross-sections. We measured a variety of channel metrics, including channel width, areal extent of bars and islands, and sinuosity in ArcGIS. Results indicate that unconfined reaches that were wide and braided during the period of elevated flows have narrowed to become single threaded and meandering in response to the reduced flows. Confined reaches have experienced minor changes since the reduction in flows, suggesting that confinement is a primary control on the degree of channel response. These findings and complimentary studies will provide managers of Sixth Water and Diamond Fork with a greater understanding of the physical response of the streams, and the resulting effects on ecological communities.

Holocene evolution of Dahab coastline - Gulf of Aqaba, Sinai Peninsula, Egypt

NASA Astrophysics Data System (ADS)

Magdy, Torab

2016-04-01

Dahab was a little Bedouin-village in Sinai Peninsula at the mid-western coast of Gulf of Aqaba approx. 90 km north of Sharm-el-Sheikh City and it means "gold" in Arabic language. But in the past 20 years ago it becomes one of the most tourist sites in Egypt. The basement complex is composed mostly of biotiteaplite-granite, mica-aplitegranite, granodiorite, quartzdiorite, alaskite, and diorite. Based on correlation with similar igneous in the most southern part of Sinai and the Red Sea area. Wadi Dahab composed of igneous and metamorphic rocks and the coastline is formed of the fragments of its rocks, mixed with fragments of coral reef and fluvial deposits of Wadi Dahab. The morphology of Dahab coastline is characterized by hooked marine spit, which composed of fluvial sediments carried by marine current from wadi Dahab mouth, this spit encloses shallow lagoon, but the active deposition on the lagoon bottom will evaluate it into saline marsh. This paper dealing with the evolution of Dahab spit and lagoon during the Holocene in addition to the recent time for last 100 years, and it impacts of the future management of the coast area. The coastline mapping during the period of study depends upon GIS technique for data were collected during field measuring by using total station, aerial photo and satellite image interpretation as well as soil sample dating. Suggested geomorphological evolution of Dahab area during the Holocene depending upon geomorphic investigation of the sedimentological process into 6 stages.

Holocene evolution of the western Orinoco Delta, Venezuela

USGS Publications Warehouse

Aslan, A.; White, W.A.; Warne, A.G.; Guevara, E.H.

2003-01-01

The pristine nature of the Orinoco Delta of eastern Venezuela provides unique opportunities to study the geologic processes and environments of a major tropical delta. Remote-sensing images, shallow cores, and radiocarbon-dating of organic remains form the basis for describing deltaic environments and interpreting the Holocene history of the delta. The Orinoco Delta can be subdivided into two major sectors. The southeast sector is dominated by the Rio Grande-the principal distributary-and complex networks of anastomosing fluvial and tidal channels. The abundance of siliciclastic deposits suggests that fluvial processes such as over-bank flooding strongly influence this part of the delta. In contrast, the northwest sector is represented by few major distributaries, and overbank sedimentation is less widespread relative to the southeast sector. Peat is abundant and occurs in herbaceous and forested swamps that are individually up to 200 km2 in area. Northwest-directed littoral currents transport large volumes of suspended sediment and produce prominent mudcapes along the northwest coast. Mapping of surface sediments, vegetation, and major landforms identified four principal geomorphic systems within the western delta plain: (1) distributary channels, (2) interdistributary flood basins, (3) fluvial-marine transitional environments, and (4) marine-influenced coastal environments. Coring and radiocarbon dating of deltaic deposits show that the northern delta shoreline has prograded 20-30 km during the late Holocene sea-level highstand. Progradation has been accomplished by a combination of distributary avulsion and mudcape progradation. This style of deltaic progradation differs markedly from other deltas such as the Mississippi where distributary avulsion leads to coastal land loss, rather than shoreline progradation. The key difference is that the Orinoco Delta coastal zone receives prodigious amounts of sediment from northwest-moving littoral currents that transport sediment from as far away as the Amazon system (???1600 km). Late Holocene progradation of the delta has decreased delta-plain gradients, increased water levels, and minimized over-bank flooding and siliciclastic sedimentation in the northwest sector. These conditions, coupled with large amounts of direct precipitation, have led to widespread peat accumulation in interdistributary basins. Because peat-forming environments cover up to 5000 km2 of the delta plain, the Orinoco may be an excellent analogue for interpreting ancient deltaic peat deposits.

A Conceptual Framework and Classification for the Fluvial-Backwater-Marine Transition in Coastal Rivers Globally

NASA Astrophysics Data System (ADS)

Howes, N. C.; Georgiou, I. Y.; Hughes, Z. J.; Wolinsky, M. A.

2012-12-01

Channels in fluvio-deltaic and coastal plain settings undergo a progressive series of downstream transitions in hydrodynamics and sediment transport, which is consequently reflected in their morphology and stratigraphic architecture. Conditions progress from uniform fluvial flow to backwater conditions with non-uniform flow, and finally to bi-directional tidal flow or estuarine circulation at the ocean boundary. While significant attention has been given to geomorphic scaling relationships in purely fluvial settings, there have been far fewer studies on the backwater and tidal reaches, and no systematic comparisons. Our study addresses these gaps by analyzing geometric scaling relationships independently in each of the above hydrodynamic regimes and establishes a comparison. To accomplish this goal we have constructed a database of planform geometries including more than 150 channels. In terms of hydrodynamics studies, much of the work on backwater dynamics has concentrated on the Mississippi River, which has very limited tidal influence. We will extend this analysis to include systems with appreciable offshore tidal range, using a numerical hydrodynamic model to study the interaction between backwater dynamics and tides. The database is comprised of systems with a wide range of tectonic, climatic, and oceanic forcings. The scale of these systems, as measured by bankfull width, ranges over three orders of magnitude from the Amazon River in Brazil to the Palix River in Washington. Channel centerlines are extracted from processed imagery, enabling continuous planform measurements of bankfull width, meander wavelength, and sinuosity. Digital terrain and surface models are used to estimate floodplain slopes. Downstream tidal boundary conditions are obtained from the TOPEX 7.1 global tidal model, while upstream boundary conditions such as basin area, relief, and discharge are obtained by linking the databases of Milliman and Meade (2011) and Syvitski (2005). Backwater and tidal length-scales are computed from published data as well as from numerical simulations. An analysis of the database combined with numerical hydrodynamic simulations allows us to organize the results into a process-based classification of coastal rivers. The classification describes the scale, shape, and flow field transitions of coastal rivers as a function of discharge, floodplain slope, and offshore tidal range.

Residence times and alluvial architecture of a sediment superslug in response to different flow regimes

USGS Publications Warehouse

Moody, John A.

2017-01-01

A superslug was deposited in a basin in the Colorado Front Range Mountains as a consequence of an extreme flood following a wildfire disturbance in 1996. The subsequent evolution of this superslug was measured by repeat topographic surveys (31 surveys from 1996 through 2014) of 18 cross sections approximately uniformly spaced over 1500 m immediately above the basin outlet. These surveys allowed the identification within the superslug of chronostratigraphic units deposited and eroded by different geomorphic processes in response to different flow regimes.Over the time period of the study, the superslug went through aggradation, incision, and stabilization phases that were controlled by a shift in geomorphic processes from generally short-duration, episodic, large-magnitude floods that deposited new chronostratigraphic units to long-duration processes that eroded units. These phases were not contemporaneous at each channel cross section, which resulted in a complex response that preserved different chronostratigraphic units at each channel cross section having, in general, two dominant types of alluvial architecture—laminar and fragmented. Age and transit-time distributions for these two alluvial architectures evolved with time since the extreme flood. Because of the complex shape of the distributions they were best modeled by two-parameter Weibull functions. The Weibull scale parameter approximated the median age of the distributions, and the Weibull shape parameter generally had a linear relation that increased with time since the extreme flood. Additional results indicated that deposition of new chronostratigraphic units can be represented by a power-law frequency distribution, and that the erosion of units decreases with depth of burial to a limiting depth. These relations can be used to model other situations with different flow regimes where vertical aggradation and incision are dominant processes, to predict the residence time of possible contaminated sediment stored in channels or on floodplains, and to provide insight into the interpretation of recent or ancient fluvial deposits.

Residence times and alluvial architecture of a sediment superslug in response to different flow regimes

NASA Astrophysics Data System (ADS)

Moody, John A.

2017-10-01

A superslug was deposited in a basin in the Colorado Front Range Mountains as a consequence of an extreme flood following a wildfire disturbance in 1996. The subsequent evolution of this superslug was measured by repeat topographic surveys (31 surveys from 1996 through 2014) of 18 cross sections approximately uniformly spaced over 1500 m immediately above the basin outlet. These surveys allowed the identification within the superslug of chronostratigraphic units deposited and eroded by different geomorphic processes in response to different flow regimes. Over the time period of the study, the superslug went through aggradation, incision, and stabilization phases that were controlled by a shift in geomorphic processes from generally short-duration, episodic, large-magnitude floods that deposited new chronostratigraphic units to long-duration processes that eroded units. These phases were not contemporaneous at each channel cross section, which resulted in a complex response that preserved different chronostratigraphic units at each channel cross section having, in general, two dominant types of alluvial architecture-laminar and fragmented. Age and transit-time distributions for these two alluvial architectures evolved with time since the extreme flood. Because of the complex shape of the distributions they were best modeled by two-parameter Weibull functions. The Weibull scale parameter approximated the median age of the distributions, and the Weibull shape parameter generally had a linear relation that increased with time since the extreme flood. Additional results indicated that deposition of new chronostratigraphic units can be represented by a power-law frequency distribution, and that the erosion of units decreases with depth of burial to a limiting depth. These relations can be used to model other situations with different flow regimes where vertical aggradation and incision are dominant processes, to predict the residence time of possible contaminated sediment stored in channels or on floodplains, and to provide insight into the interpretation of recent or ancient fluvial deposits.

Breaking rocks made easy: subcritical processes and tectonic predesign

NASA Astrophysics Data System (ADS)

Voigtlaender, Anne; Krautblatter, Michael

2017-04-01

In geomorphic studies, to change in landforms, e.g. by rock slope failure, fluvial or glacial erosion, a threshold is commonly assumed, which is crossed either by an increase in external driving or a decrease of internal resisting forces, respectively. If the threshold is crossed, bedrock breaks and slope fails, rivers incise and glaciers plug and sew their bed. Here we put forward a focus on the decrease of the resisting forces, as an increase in the driving forces, to match the strength of bedrock, is not that likely. We suggest that the degradation of resisting forces of bedrock can be better explained by subcritical processes like creep, fatigue and stress corrosion interplaying with tectonic predesign. Both concepts, subcritical processes and tectonic predesign have been issued in the last century, but have not been widely accepted nor have their assumptions been explicitly stressed in recent case studies. Moreover both concepts profit especially on scale issues if merged. Subcritical crack growth, includes different mechanisms promoting fractures well below the ultimate strength. Single infinitesimal but irreversible damage and deformations are induced in the material over time. They interact with inherent microstructural flaws and low applied stresses, limiting local strength and macroscopic behavior of bedrock. This reissues the concept of tectonic predesigned, as proposed by A.E. Scheidegger, which not only encompasses structural features that determine the routing of drainage patterns and shear planes, e.g. joints, faults and foliations, but also the (neo)tectonic stress-field and the (in-situ) strain state of bedrocks and mountains. Combining subcritical processes and tectonic predesign we can better explain, why and where we see a dissected, eroded and geomorphic divers' landscape. In this conceptual framework actual magnitudes of the driving forces are accounted for and so is the nature of the bedrock material, to better understand the trajectories of the forms we study, and break rocks easily.

Local efficiency in fluvial systems: Lessons from Icicle Bend

NASA Astrophysics Data System (ADS)

Jerin, Tasnuba; Phillips, Jonathan

2017-04-01

Development of fluvial systems is often described and modeled in terms of principles related to maxima, minima, or optima of various hydraulic or energy parameters that can generally be encompassed by a principle of efficiency selection (more efficient flow routes tend to be preferentially selected and enhanced). However, efficiency selection is highly localized, and the cumulative effects of these local events may or may not produce more efficient pathways at a broader scale. This is illustrated by the case of Icicle Bend on Shawnee Run, a limestone bedrock stream in central Kentucky. Field evidence indicates that a paleochannel was abandoned during downcutting of the stream, and the relocation was analyzed using a flow partitioning model. The bend represents abandonment of a steeper, straighter, more efficient channel at the reach scale in favor of a longer, currently less steep and less efficient flow path. This apparently occurred owing to capture of Shawnee Run flow by a subsurface karst flow path that was subsequently exhumed. The development of Icicle Bend illustrates the local nature of efficiency selection and the role of historical contingency in geomorphic evolution.

Relief Evolution in Tectonically Active Mountain Ranges

NASA Technical Reports Server (NTRS)

Whipple, Kelin X.

2004-01-01

The overall aims of this 3-yr project, as originally proposed were to: (1) investigate quantitatively the roles of fluvial and glacial erosion in the evolution of relief in mountainous regions, and (2) test rigorously the quality and accuracy of SRTM topographic data in areas of rugged relief - both the most challenging and of greatest interest to geomorphic, neotectonic, and hazards applications. Natural laboratories in both the western US and the Southern Alps of New Zealand were identified as most promising. The project has been both successful and productive, despite the fact that no SRTM data for our primary field sites in New Zealand were released on the time frame of the work effort. Given the delayed release of SRTM data, we pursued the scientific questions of the roles of fluvial and, especially, glacial erosion in the evolution of relief in mountainous regions using available digital elevation models (DEMs) for the Southern Alps of New Zealand (available at both 25m and 50m pixel sizes), and USGS 10m and 30m DEMs within the Western US. As emphasized in the original proposal, we chose the emphasis on the role of glacial modification of topographic relief because there has been little quantitative investigation of glacial erosion processes at landscape scale. This is particularly surprising considering the dramatic sculpting of most mid- and high-latitude mountain ranges, the prodigious quantities of glacially-derived sediment in terrestrial and marine basins, and the current cross-disciplinary interest in the role of denudational processes in orogenesis and the evolution of topography in general. Moreover, the evolution of glaciated landscapes is not only a fundamental problem in geomorphology in its own right, but also is at the heart of the debate over Late Cenozoic linkages between climate and tectonics.

The contribution of total suspended solids to the Bay of Biscay by Cantabrian Rivers (northern coast of the Iberian Peninsula)

NASA Astrophysics Data System (ADS)

Prego, Ricardo; Boi, Paola; Cobelo-García, Antonio

2008-07-01

Information of suspended sediments fluxes of small rivers to the coastal zone is sparse, and this is particularly so for the Iberian Rivers. To help address this shortage of information, the relationship between fluvial discharge and total suspended solids (TSS) for the main 28 Cantabrian Rivers using data from 22 years monitoring by the COCA network has been analysed, and their particulate material fluxes to the Bay of Biscay coasts have been quantified. The Cantabrian Fluvial System (drainage basin area of 20,333 km 2) may be considered as a quasi-homogeneous fluvial system with an average discharge of 561 m - 3 s - 1 and average loads of 35 kg TSS s - 1 with rivers showing similar average yields of 56 t km - 2 a - 1 . The average TSS contribution is 1.2 ± 0.2 10 9 kg a - 1 . This seaward flux of sediment is dispersed along the entire North Iberian coast and is rather modest (25% of the total supply) in comparison with the output from the French Rivers to the Bay of Biscay. The TSS loads of Cantabrian Rivers indicate they are similar to world upland rivers and those of other parts of Northern Europe according to Milliman and Syvistki [Milliman and Syvistki, 1992. Geomorphic/tectonic control of sediment discharge to the ocean: the importance of small mountainous rivers. Journal of Geology, 100: 525-544] and Milliman [Milliman, 2001. Delivery and fate of fluvial water and sediment to the sea: a marine geologist's view of European rivers. Scientia Marina, 65: 121-132]. Although their TSS flux is practically negligible (13,000 times lower) when compared to the world average flux, they provide a good example of the role of small Atlantic temperate rivers.

Knickpoint formation and retreat: stairway to heaven or pathway to declivity

NASA Astrophysics Data System (ADS)

Rengers, Francis; Tucker, Gregory

2016-04-01

The importance of knickpoints in shaping fluvial systems has been observed in laboratory settings, small experimental plots, and at the landscape scale. By creating a step in a river's longitudinal profile, knickpoints can shield upstream tributaries from a much lower base level, and therefore represent a buffer in the energy transfer of a stream system. Knickpoints are located at a transition point between the potential energy of material stored upstream and the kinetic energy of erosion processes and sediment transport below the knickpoint. We hypothesize that the long-term persistence of a discrete, retreating knickpoint requires a balance between the fluvial erosion of the feature, and sedimentation rates downstream. Here we present the results of a short-term (four year) study of knickpoint morphology in a natural gully system to better constrain the conditions necessary to preserve distinct knickpoints over time. We monitored knickpoint erosion using time-lapse photography, repeat terrestrial lidar, soil moisture monitoring, and rainfall-runoff measurements. Our results indicate that shallow subsurface hydrology leads to knickpoint erosion via mass failure, and produces a stable and predictable morphological signature of knickpoint erosion (amphitheater shaped heads). We generalized these observations into a numerical model of erosion/sedimentation to understand the geomorphic legacy of knickpoints in deeply incised gullies. Modeling showed that knickpoints can maintain an incisional step for hundreds to thousands of years when knickpoints retreat via mass failure and sediment is removed from the knickpoint base by fluvial scour. To test simulations of long-term stability generated by the numerical model, we used Optically Stimulated Luminesence to date alluvial deposits at existing gully knickpoints. This geochronological dating confirmed that gully knickpoints have been active in our study area for hundreds to thousands of years, particularly during drought periods. Therefore, numerical modeling and field data support our hypothesis that knickpoint preservation during upstream retreat represents a delicate balance between erosion and sediment transport, and given ideal conditions, a steep knickpoint may persist in long-term dynamic equilibrium.

Human and natural impacts on fluvial and karst depressions of the Maya Lowlands

NASA Astrophysics Data System (ADS)

Beach, Timothy; Luzzadder-Beach, Sheryl; Dunning, Nicholas; Cook, Duncan

2008-10-01

This paper begins to differentiate the major drivers and chronology of erosion and aggradation in the fluvial and fluviokarst landscapes of the southern and central Maya Lowlands. We synthesize past research on erosion and aggradation and add new data from water, soils, radiocarbon dating, and archaeology to study the quantity, timing, and causes of aggradation in regional landscape depressions. Geomorphic findings come from many excavations across a landscape gradient from upland valleys, karst sinks, and fans into the coastal plain floodplains and depressions. Findings from water chemistry show that sources in the uplands have low quantities of dissolved ions but water in the coastal plains has high amounts of dissolved ions, often nearly saturated in calcium and sulfate. We found significant geomorphic complexity in the general trends in upland karst sinks. In a few instances, sediments preserve Late Pleistocene paleosols, buried 2-3 m, though many more have distinct middle to late Holocene paleosols, buried 1-2 m, after c. 2300 BP (Maya Early to Late Preclassic). From 2300-1100 BP (Late Preclassic to Classic Periods), the landscape aggraded from five main mechanisms: river flooding, climatic instability, accelerated erosion, ancient Maya landscape manipulation, and gypsum precipitation from a rise in a water table nearly saturated in calcium and sulfate ions. Evidence exists for two or three high magnitude floods, possibly driven by hurricanes. Moreover, lake-core and geophysical studies from the Petén Lakes region have shown high rates of deposition of silicate clays ('Maya Clays') starting and peaking during the Maya Preclassic and continuing to be high through the Late Classic. The main driver on upland karst depressions, the Petén lakes, upland valleys, and fans was accelerated soil erosion, but water table rise, probably driven by sea-level rise, was the main driver on the wetlands of the coastal plain because the aggraded sediments here are dominantly composed of gypsum, precipitated from the groundwater. This latter mechanism represents a little recognized mechanism of aggradation over a large region. These large scale environmental changes occurred during periods of intensive ancient Maya land use and climatic instability, both of which may have contributed to erosion by increasing runoff. Despite these geomorphic changes, ancient Maya farmers adapted in several key cases.

Old River Control Complex Sedimentation Investigation

DTIC Science & Technology

2015-06-01

efforts to describe the shoaling processes and sediment transport in the two-river system. Geomorphic analysis The geomorphic assessment utilized...District, New Orleans. The investigation was conducted via a combination of field data collection and laboratory analysis, geomorphic assessments, and...6 Geomorphic analysis

Constructing a Sediment Budget for the Johnsbach, Styria - Adding up numbers and drawing arrows?

NASA Astrophysics Data System (ADS)

Rascher, Eric; Sass, Oliver

2016-04-01

Understanding the evolution and functions of a river system and interpreting the morphology and the dynamics of the channel is a key factor in fluvial geomorphology. For this purpose it is essential to analyse the processes of sediment input and output within and between river reaches and to detect the various forms of storage types on hillslopes and in the channel network. From these processes, catchment scale sediment fluxes are derived and result in sediment budgets showing the amount and motion of sediment through the system. This study aims at developing a sediment budget for the so called "Zwischenmäuerstrecke" in the Johnsbach Valley, a typical, non-glaciated alpine catchment in the eastern Austrian Alps. The valley covers an area of 65 km² with altitudes ranging from 584 m a.s.l. at the outlet to 2369 m a.s.l. (Hochtor). The valley is drained by the Johnsbach River which originates in a crystalline bedrock dominated part of the catchment. After approximately 10 km of the distance downstream the lithology changes to calcareous bedrock. In this part of the Johnsbach Valley ("Zwischenmäuerstrecke") most of the sediment contributing areas are located on both sides of the river along a 5 km river reach. Initial activities included geomorphological mapping and a GIS based connectivity analysis. Building on this survey, test sites were selected for detailed investigations, and an activity classification of all side channels in the "Zwischenmäuerstrecke" using different criteria was achieved from which the sediment budget will be extrapolated. Despite (or rather because of) the extensive dataset this is still a challenging task since geomorphic processes are highly variable in time and space. Our applied methods in the field are associated to the geomorphic process chain from source to sink. Sediment input from rock falls was investigated using TLS measurements to determine the spatial distribution of rock fall rates. The quantification of erosion and debris flow processes on the hillslopes was achieved by means of TLS surveys two times a year from 2013-2015. The precedent mapping and the ALS overview surveys (DEMs from 2010 and 2015) ensure that the measured processes are representative for wider areas. The thickness and structure of important sediment storage bodies at the slopes and in the side valleys were investigated using geophysical methods (ERT, GPR, seismics). The fluvial sediment transport was analyzed using impact sensors, geophone installations and mobile basket samplers. The results of all steps of quantification will later be transferred to the entire study area (Johnsbach catchment) using the mapping results and GIS analyses. The output will be a sediment budget model of the Johnsbachtal. The step towards application comprises the analysis of current management problems (amount of "missing" sediment for ecological purposes, and effects on hydropower plants) and the possible consequences of artificial barriers being altered or removed.

High-resolution topography and geomorphology of select archeological sites in Glen Canyon National Recreation Area, Arizona

USGS Publications Warehouse

Collins, Brian D.; Corbett, Skye C.; Sankey, Joel B.; Fairley, Helen C.

2014-01-01

Along the Colorado River corridor between Glen Canyon Dam and Lees Ferry, Arizona, located some 25 km downstream from the dam, archaeological sites dating from 8,000 years before present through the modern era are located within and on top of fluvial and alluvial terraces of the prehistorically undammed river. These terraces are known to have undergone significant erosion and retreat since emplacement of Glen Canyon Dam in 1963. Land managers and policy makers associated with managing the flow of the Colorado River are interested in understanding how the operations of Glen Canyon Dam have affected the archeological sites associated with these terraces and how dam-controlled flows currently interact with other landscape-shaping processes. In 2012, the U.S. Geological Survey initiated a research project in Glen Canyon to study the types and causes of erosion of the terraces. This report provides the first step towards this understanding by presenting comparative analyses on several types of high-resolution topographic data (airborne lidar, terrestrial lidar, and airborne photogrammetry) that can be used in the future to document and analyze changes to terrace-based archaeological sites. Herein, we present topographic and geomorphologic data of four archaeological sites within a 14 km segment of Glen Canyon using each of the three data sources. In addition to comparing each method’s suitability for adequately representing the topography of the sites, we also analyze the data within each site’s context and describe the geomorphological processes responsible for erosion. Our results show that each method has its own strengths and weaknesses, and that terrestrial and airborne lidar are essentially interchangeable for many important topographic characterization and monitoring purposes. However, whereas terrestrial lidar provides enhanced capacity for feature recognition and gully morphology delineation, airborne methods (whether by way of laser or optical sensors) are better suited for reach- and regional-scale mapping. Our site-specific geomorphic analyses of the four archeological sites indicate that their current topographical conditions are a result of different and sometimes competing erosional agents, including bedrock- and terrace-based overland flow, fluvial-induced terrace bank collapse, and alluvial-fan-generated debris flows. Although the influences of anthropogenic-induced erosion from dam operations are not specifically analyzed in this report, we do identify geomorphic settings where dam operations are either more or less likely to affect archeological site stability. This information can be used to assist with future monitoring efforts of these sites and identification of similar conditions for other archeological sites along the Colorado River corridor in Glen Canyon.

Quaternary Sedimentary and Geomorphic History of River Valleys in the Lake Titicaca Basin, Peru and Bolivia

NASA Astrophysics Data System (ADS)

Rigsby, C. A.; Farabaugh, R. L.; Baker, P. A.

2002-12-01

Lacustrine sediments have become important archives of paleoclimatic history in the tropical Andes of South America. The history of lake level of Lake Titicaca (LT) has played a central role in these reconstructions. Here we report on our ongoing studies of the late Quaternary sedimentary and geomorphic histories of two of the major tributaries to LT (the Rios Ramis and Ilave) and on our earlier studies of LT's only outlet (the Rio Desaguadero). The strata and fluvial terraces in these valleys record large-scale aggradation and downcutting events that are apparently correlative with both climate changes in the LT basin and local complex response mechanisms (changes in sediment source, topographic variability, etc.). Both the Ramis and Ilave valleys have 5 terrace tracts, ranging from less than 1 m to approximately 53 m above the river level and occurring as both paired and unpaired tracts and as cut-fill, fill-, and strath terraces. The Rio Desaguadero valley has 4, locally paired, cut-fill and fill terrace tracts that range in height from approximately 2 m to 40 m above river level. In all three valleys, the terraces are underlain by meandering- and braided-river sands and gravels and by lacustrine muds. Radiocarbon dates from the Ilave and Desaguadero valleys suggest that strata in these valleys aggraded during periods of high or rising levels of LT, high or increasing sedimentation rates in the Rio Ilave delta, high (but variable) regional precipitation, and lacustrine sedimentation in the upstream-most reaches of the Rio Desaguadero valley. These same strata were downcut during periods of low or falling levels of LT, low or rapidly decreasing sedimentation rates in the Rio Ilave delta, and lower regional precipitation and runoff. In all three valleys, aggradational periods are punctuated by equilibrium periods of soil formation, downcutting events are episodic, and the most recent events are aggradation and subsequent downcutting of a low, young fill-terrace. Radiocarbon dates from the Ramis valley (in progress) will allow us to compare the timing of fluvial events in all three valleys with the timing of climatic events recorded in LT and elsewhere on the Peruvian and Bolivian Altiplano and to better understand the climatic effects on both fluvial landscapes and regional cultural evolution.

Luminescence dating of river terrace formation - methodological challenges and complexity of result interpretation: a case study from the headwaters of the River Main, Germany

NASA Astrophysics Data System (ADS)

Kolb, Thomas; Fuchs, Markus; Zöller, Ludwig

2015-04-01

River terraces are widespread geomorphic features of Quaternary landscapes. Besides tectonics, their formation is predominantly controlled by climatic conditions. Changes in either conditions cause changes in fluvial discharge and sediment load. Therefore, fluvial terraces are widely used as important non-continuous sedimentary archives for paleotectonic and paleoenvironmental reconstruction. The informative value of fluvial archives and their significance for paleoenvironmental research, however, strongly depend on a precise dating of the terrace formation. Over the last decades, various luminescence dating techniques have successfully been applied on fluvial deposits and were able to provide reliable age information. In contrast to radiocarbon dating, modern luminescence dating techniques provide an extended dating range, which enables the determination of age information for fluvial and other terrestrial archives far beyond the last glacial-interglacial cycle. Due to the general abundance of quartz and feldspar minerals, there is almost no limitation of dateable material, so that luminescence dating methods can be applied on a wide variety of deposits. When using luminescence dating techniques, however, some methodological difficulties have to be considered. Due to the mechanism of fluvial transport, this is especially true for fluvial sediments, for which two major problems have been identified to be the main reasons of incorrect age estimations: (1) incomplete resetting of the luminescence signal during transport and (2) dosimetric inaccuracies as a result of the heterogeneity of terrace gravels. Thus, luminescence dating techniques are still far from being standard methods for dating fluvial archives and the calculated sedimentation ages always demand a careful interpretation. This contribution reveals some of the difficulties that may occur when luminescence dating techniques are applied on river terraces and illustrates several strategies used for overcoming these problems and for determining correct sedimentation ages. The presented results are based on a case study, located in the headwaters of the River Main, the longest right bank tributary of the Rhine drainage system. Here, within an oversized dry valley in Northern Bavaria (Germany), five Pleistocene terraces are distinguished. The terraces are interpreted as the result of a complex landscape evolution, which is characterized by multiple river deflections. The need for a careful interpretation of luminescence results is illustrated by some optically stimulated luminescence (OSL) ages calculated for the youngest of these five Pleistocene terraces. These results show different sedimentation ages of samples originating from the same morphological unit. Thus, these ages may be interpreted as evidence for a diachronic character of river incision and, hence, point to the complexity of fluvial systems' response to climatically and/or tectonically forced changes in local and regional paleoenvironmental conditions.

Deep Time Ecosystem Engineers: The Correlation between Palaeozoic Vegetation, Evolution of Physical Riverine Habitats, and Plant and Animal Terrestrialization

NASA Astrophysics Data System (ADS)

Davies, N. S.; Gibling, M. R.

2012-04-01

Evidence from the deep time geological record attests to the fundamental importance of plant life to the construction of physical habitats within fluvial environments. Data from an extensive literature review and original fieldwork has demonstrated that many landforms and geomorphic features present in modern river systems do not appear in the deep time stratigraphic record until terrestrial vegetation had adopted certain evolutionary advances that enabled them: for example, stable point bars are associated with the development of deep rooting in the Siluro-Devonian and avulsive anabranching fluvial systems appear at the same time as extensive arborescent vegetation in the Carboniferous. In this presentation, we demonstrate a correlation between the diversification of physical fluvial sedimentary environments and the expansion of terrestrial fauna and flora throughout the Cambrian to Carboniferous, and offer an explanation for this observation that considers plants as ecosystem engineers on an evolutionary timescale. Many extrinsic factors have been considered when attempting to identify controls on the evolutionary timelines of terrestrialization for various different organisms. Factors such as O2 and CO2 levels in the atmosphere, climatic events, global tectonic organisation, sea-level changes, extinction events, weathering rates and nutrient supply are all known to have played a role. However, another factor is likely to have been a fundamental prerequisite for achieving terrestrial biodiversity: the variety of physical habitats available for newly evolved organisms. In fluvial environments, this is a function of the diversity of hydrodynamic regimes (both temporal and spatial) within the world's river systems. In a world where only sheet-like ephemeral braided rivers existed, such as appears to be the case in pre-vegetation settings, both the geographic extent of riparian margins and the diversity of hydrodynamic regimes would be minimal. However, as fluvial corridors narrowed throughout the Ordovician and Silurian, the potential importance of riparian zones as a global biome would have increased as they became more extensive in continental environments. Furthermore, the move towards climatic controls on the ephemeral or perennial nature of streams would have boosted the diversity of temporally diverse hydrodynamic regimes. As single-thread meandering channels and extensive muddy floodplains, stabilised by vegetation, became significant components of the global suite of alluvial geomorphic components throughout the Siluro-Devonian, further diversification of the extent and diversity of physical habitats within the global riparian biome occurred. Into the Carboniferous, the evolution of the anabranching habit within alluvial systems created further new physical landforms for colonization and would have promoted increasingly complex hyporheic flow regimes. Furthermore the associated advent of arborescent vegetation and, specifically, the large woody debris supplied by this, would have created a wealth of new microhabitats for continental organisms. The expanding extent and diversity of physical alluvial niches during the Palaeozoic can be argued to be an underappreciated driver of the terrestrialization of early continental life. The study of the deep time fossil and stratigraphic record also illustrates that vegetation is a fundamental prerequisite for the creation of biogeomorphic alluvial landforms and physical habitats and microhabitats.

Effects of large deep-seated landslides on hillslope morphology, western Southern Alps, New Zealand

NASA Astrophysics Data System (ADS)

Korup, Oliver

2006-03-01

Morphometric analysis and air photo interpretation highlight geomorphic imprints of large landslides (i.e., affecting ≥1 km2) on hillslopes in the western Southern Alps (WSA), New Zealand. Large landslides attain kilometer-scale runout, affect >50% of total basin relief, and in 70% are slope clearing, and thus relief limiting. Landslide terrain shows lower mean local relief, relief variability, slope angles, steepness, and concavity than surrounding terrain. Measuring mean slope angle smoothes out local landslide morphology, masking any relationship between large landslides and possible threshold hillslopes. Large failures also occurred on low-gradient slopes, indicating persistent low-frequency/high-magnitude hillslope adjustment independent of fluvial bedrock incision. At the basin and hillslope scale, slope-area plots partly constrain the effects of landslides on geomorphic process regimes. Landslide imprints gradually blend with relief characteristics at orogen scale (102 km), while being sensitive to length scales of slope failure, topography, sampling, and digital elevation model resolution. This limits means of automated detection, and underlines the importance of local morphologic contrasts for detecting large landslides in the WSA. Landslide controls on low-order drainage include divide lowering and shifting, formation of headwater basins and hanging valleys, and stream piracy. Volumes typically mobilized, yet still stored in numerous deposits despite high denudation rates, are >107 m3, and theoretically equal to 102 years of basin-wide debris production from historic shallow landslides; lack of absolute ages precludes further estimates. Deposit size and mature forest cover indicate residence times of 101-104 years. On these timescales, large landslides require further attention in landscape evolution models of tectonically active orogens.

Geomorphic response to flow regulation and channel and floodplain alteration in the gravel-bedded Cedar River, Washington, USA

USGS Publications Warehouse

Gendaszek, Andrew S.; Magirl, Christopher S.; Czuba, Christiana R.

2012-01-01

Decadal- to annual-scale analyses of changes to the fluvial form and processes of the Cedar River in Washington State, USA, reveal the effects of flow regulation, bank stabilization, and log-jam removal on a gravel-bedded river in a temperate climate. During the twentieth century, revetments were built along ~ 60% of the lower Cedar River's length and the 2-year return period flow decreased by 47% following flow regulation beginning in 1914. The formerly wide, anastomosing channel narrowed by over 50% from an average of 47 m in 1936 to 23 m in 1989 and became progressively single threaded. Subsequent high flows and localized revetment removal contributed to an increase in mean channel width to about 34 m by 2011. Channel migration rates between 1936 and 2011 were up to 8 m/year in reaches not confined by revetments or valley walls and less than analysis uncertainty throughout most of the Cedar River's length where bank armoring restricted channel movement. In unconfined reaches where large wood and sediment can be recruited, contemporary high flows, though smaller in magnitude than preregulation high flows, form and maintain geomorphic features such as pools, gravel bars, and side channels. Reaches confined by revetments remain mostly unmodified in the regulated flow regime. While high flows are important for maintaining channel dynamics in the Cedar River, their effectiveness is currently reduced by revetments, limited sediment supply, the lack of large wood available for recruitment to the channel, and decreased magnitude since flow regulation.

Fish Communities and Habitat of Geomorphically Stable Reference Reaches in Streams of the Catskill Mountain Region, New York

USGS Publications Warehouse

Mulvihill, Christiane I.; Baldigo, Barry P.; Ernst, Anne G.

2009-01-01

In 2002, the U.S. Geological Survey, in cooperation with the New York City Department of Environmental Protection, began a 5-year study to develop a database that documents the physical and biological characteristics of nine stable reference reaches from seven streams in the New York City West of Hudson Water Supply Watershed in the Catskill Mountain region of New York State. Primary objectives of this study were to (1) develop a reference-reach database of morphology, aquatic biology, and fluvial processes, and (2) summarize the relations between fish communities, aquatic habitat, and stable stream morphology in streams in the Catskill Mountain region. Secondary objectives included documenting year-to-year variability in fish populations and stream habitat in geomorphically stable streams and demonstrating how reliably Habitat Suitability Index models can be used to characterize habitat conditions and predict the presence and abundance of populations of trout species. Fish and habitat databases were developed, and several important relations were identified. Fish-community indices differed considerably among sites where trout were present and where they were either absent or present in very low numbers; these differences were reflected in higher Habitat Suitability Index scores at trout-dominated sites. Several fish- community and habitat variables were found to be strongly associated with indices of stability and, therefore, determined to be useful tools for evaluating stream condition. Lastly, preliminary results suggest Rosgen stream type data can help refine fish and habitat relations and assist in our ability to predict habitat potential and fish-community composition.

Altered hydrologic and geomorphic processes and bottomland hardwood plant communities of the lower White River Basin

USGS Publications Warehouse

King, Sammy L.; Keim, Richard F.; Hupp, Cliff R.; Edwards, Brandon L.; Kroschel, Whitney A.; Johnson, Erin L.; Cochran, J. Wesley

2016-09-12

Determine stand establishment patterns of bottomland hardwoods within selected plant communities along three sections of the floodplain. This study provides baseline information on the current geomorphic and hydrologic conditions of the river and can assist in the interpretation of forest responses to past hydrologic and geomorphic processes. Understanding the implications for floodplain forests of geomorphic adjustment in the Lower Mississippi Alluvial Valley is key to managing the region’s valuable resources for a sustainable future.

An Early Pennsylvanian threshold for the influence of vegetation on fluvial landscapes, based on the geological record of Atlantic Canada

NASA Astrophysics Data System (ADS)

Gibling, Martin; Ielpi, Alessandro; Bashforth, Arden; Davies, Neil

2015-04-01

Vegetation profoundly influences modern fluvial systems, depending on plant life-history strategies, tolerance to disturbance, and habitat drainage. However, direct evidence for these dynamic relationships is cryptic and has commonly been overlooked in ancient deposits. We report evidence for profound interactions between channels, in situ and transported vegetation in Lower Pennsylvanian formations of Atlantic Canada (~310 Ma), attributed to braided, meandering and fixed-channel (anastomosing) systems. Plant groups include lycopsids that preferred stable wetland settings, disturbance-tolerant calamitaleans, and deeply rooted cordaitaleans (early gymnosperms) that originated in the late Mississippian and colonised both wetland and dryland settings. For the meandering and anastomosing channel deposits, upright vegetation was observed within channel-based bedforms and bars and on channel margins. Lycopsids and calamitalean groves colonized the channel bed and bank-attached bars during periods of reduced flow, nucleating bar growth after flow resumed. Upright lycopsids and cordaitaleans are common along channel cutbanks and are locally tilted towards the channel, implying involvement in bank stabilization. Rhizoconcretions that formed around deep cordaitalean roots may have aided bank reinforcement. Tetrapod and arthropod trackways in the channel deposits indicate a close linkage between riparian and aquatic ecosystems. In the braided systems, sediments that contain abundant cordaitalean logs constitute nearly 20% of channel deposits, and the logs form channel-base lags, fill channels up to 6 m deep, and form nuclei for shallow sandbars. Log accumulations overlain by shale lenses imply a contribution to channel avulsion. Rooted channel-sandstones containing upright trees are interpreted as vegetated islands in an island-braided system. Anastomosing systems are abundant in these Lower Pennsylvanian formations but rare in older strata, and the multi-channel island-braided systems are the oldest yet described. The rise to prominence of these two anabranching styles, broadly coinciding with the rise of cordaitaleans, implies that fluvial landscapes had crossed a threshold from a geomorphic and biogeomorphic mode of operation into a fully ecological mode with feedback loops between vegetation and fluvial processes. Thereafter, patterns of interaction between rivers and vegetation broadly resembled those of today, with prominent riparian corridors and profound consequences for aquatic, soil and other terrestrial ecosystems. Our field observations confirm the co-evolution of river systems, vegetation and animals, and highlight a need to incorporate vegetation more fully into earth-system and landscape models.

The topographic signature of anthropogenic geomorphic processes

NASA Astrophysics Data System (ADS)

Tarolli, P.; Sofia, G.

2014-12-01

Within an abiotic-dominated context, geomorphologic patterns and dynamics are single expressions of trade-offs between the physical resistance forces, and the mechanical and chemical forces related to climate and erosion. Recently, however, it has become essential for the geomorphological community to take into account also biota as a fundamental geomorphologic agent acting from local to regional scales. However, while there is a recent flourishing literature about the impacts of vegetation on geomorphic processes, the study of anthropogenic pressure on geomorphology is still at its early stages. Humans are indeed among the most prominent geomorphic agents, redistributing land surface, and causing drastic changes to the geomorphic organization of the landscape (e.g. intensive agriculture, urbanization), with direct consequences on land degradation and watershed response. The reconstruction or identification of artificial or anthropogenic topographies, therefore, provides a mechanism for quantifying anthropogenic changes to the landscape systems in the context of the Anthropocene epoch. High-resolution topographic data derived from the recent remote sensing technologies (e.g. lidar, SAR, SfM), offer now new opportunities to recognize better understand geomorphic processes from topographic signatures, especially in engineered landscapes where the direct anthropic alteration of processes is significant. It is possible indeed to better recognize human-induced geomorphic and anthropogenic features (e.g. road networks, agricultural terraces), and the connected erosion. The study presented here may allow improved understanding and targeted mitigation of the processes driving geomorphic changes during urban development and help guide future research directions for development-based watershed studies. Human society is deeply affecting the environment with consequences on the landscape. It is therefore fundamental to establish greater management control over the Earth's rapidly changing ecosystems. Tarolli, P. (2014). High-resolution topography for understanding Earth surface processes: opportunities and challenges, Geomorphology, 216, 295-312, doi:10.1016/j.geomorph.2014.03.008.

Geomorphic Controls on Floodplain Soil Organic Carbon in the Yukon Flats, Interior Alaska, From Reach to River Basin Scales

NASA Astrophysics Data System (ADS)

Lininger, K. B.; Wohl, E.; Rose, J. R.

2018-03-01

Floodplains accumulate and store organic carbon (OC) and release OC to rivers, but studies of floodplain soil OC come from small rivers or small spatial extents on larger rivers in temperate latitudes. Warming climate is causing substantial change in geomorphic process and OC fluxes in high latitude rivers. We investigate geomorphic controls on floodplain soil OC concentrations in active-layer mineral sediment in the Yukon Flats, interior Alaska. We characterize OC along the Yukon River and four tributaries in relation to geomorphic controls at the river basin, segment, and reach scales. Average OC concentration within floodplain soil is 2.8% (median = 2.2%). Statistical analyses indicate that OC varies among river basins, among planform types along a river depending on the geomorphic unit, and among geomorphic units. OC decreases with sample depth, suggesting that most OC accumulates via autochthonous inputs from floodplain vegetation. Floodplain and river characteristics, such as grain size, soil moisture, planform, migration rate, and riverine DOC concentrations, likely influence differences among rivers. Grain size, soil moisture, and age of surface likely influence differences among geomorphic units. Mean OC concentrations vary more among geomorphic units (wetlands = 5.1% versus bars = 2.0%) than among study rivers (Dall River = 3.8% versus Teedrinjik River = 2.3%), suggesting that reach-scale geomorphic processes more strongly control the spatial distribution of OC than basin-scale processes. Investigating differences at the basin and reach scale is necessary to accurately assess the amount and distribution of floodplain soil OC, as well as the geomorphic controls on OC.

Hydrological responses to channelization and the formation of valley plugs and shoals

USGS Publications Warehouse

Pierce, Aaron R.; King, Sammy L.

2017-01-01

Rehabilitation of floodplain systems focuses on restoring interactions between the fluvial system and floodplain, however, there is a paucity of information on the effects of valley plugs and shoals on floodplain hydrological processes. We investigated hydrologic regimes in floodplains at three valley plug sites, two shoal sites, and three unchannelized sites. Valley plug sites had altered surface and sub-surface hydrology relative to unchannelized sites, while only sub-surface hydrology was affected at shoal sites. Some of the changes were unexpected, such as reduced flood duration and flood depth in floodplains associated with valley plugs. Our results emphasize the variability associated with hydrologic processes around valley plugs and our rudimentary understanding of the effects associated with these geomorphic features. Water table levels were lower at valley plug sites compared to unchannelized sites, however, valley plug sites had a greater proportion of days when water table inundation was above mean root collar depth than both shoal and unchannelized sites as a result of lower root collar depths and higher deposition rates. This study has provided evidence that valley plugs can affect both surface and sub-surface hydrology in different ways than previously thought and illustrates the variability in hydrological responses to valley plug formation.

Drainage evolution in the debris avalanche deposits near Mount Saint Helens, Washington

NASA Technical Reports Server (NTRS)

Beach, G. L.; Dzurisin, D.

1984-01-01

The 18 May 1980 eruption of Mount St. Helens was initiated by a massive rockslide-debris avalanche which completely transformed the upper 25 km of the North Fork Toutle River valley. The debris was generated by one of the largest gravitational mass movements ever recorded on Earth. Moving at an average velocity of 35 m/s, the debris avalanche buried approximately 60 sq km of terrain to an average depth of 45 m with unconsolidated, poorly sorted volcaniclastic material, all within a period of 10 minutes. Where exposed and unaltered by subsequent lahars and pyroclastic flows, the new terrain surface was characterized predominantly by hummocks, closed depressions, and the absence of an identifiable channel network. Following emplacement of the debris avalanche, a complex interrelationship of fluvial and mass wasting processes immediately began operating to return the impacted area to an equilibrium status through the removal of material (potential energy) and re-establishment of graded conditions. In an attempt to chronicle the morphologic evolution of this unique environmental setting, a systematic series of interpretative maps of several selected areas was produced. These maps, which document the rate and character of active geomorphic processes, are discussed.

Erosional dynamics, flexural isostasy, and long-lived escarpments: A numerical modeling study

NASA Technical Reports Server (NTRS)

Tucker, Gregory E.; Slingerland, Rudy L.

1994-01-01

Erosional escarpments common features of high-elevation rifted continets. Fission track data suffest that these escarpments form by base level lowering and/or marginal uplift during rifting, followed by lateral retreat of an erosion front across tens to hundreds of kioometers. Previous modeling studies have shown that this characteristic pattern of denudation can have a profound impact upon marginal isostatic uplift and the evolution of offshore sedimentary basins. Yet at present there is only a rudimentary understanding of the geomorphic mechanisms capable of driving such prolonged escarpment retreat. In this study we present a nonlinear, two-dimensional landscape evolution model tha tis used to asses the necessary and sufficient conditions for long-term retreat of a rift-generated escarpment. The model represents topography as a grid of cells, with drainage networkds evolving as water flows across the grid in the direction of steepest descent. The model accounts for sediment production by weathering, fluvial sediment transport, bedrock channel erosion, and hillslope sediment transport by diffusive mechanisms and by mass failure. Numerical experiments presented explore the effects of different combinations of erosion processes and of dynamic coupling between denudation and flexural isostatic uplift. Model results suggest that the necessary and sufficient conditions for long-term escarpment retreat are (1) incising bedrock channels in which the erosion rate increases with increasing drainage area, so that the channels steepen and propagate headward; (2) a low rate of sediment production relative to sediment transport efficiency, which promotes relief-generating processes over diffusive ones; (3) high continental elevation, which allows greater freedom for fluvial dissection; and (4) any process, including flexural isostatic uplift, that helps to maintain a drainage divide near an escarpment crest. Flexural isostatic uplift also facilitates escarpment, thereby increasing channel gradients and accelerating erosion which in turn generates additional isostatic uplift. Of all the above conditions, high continental elevation is common ot most rift margin escarpments and may ultimately be the most important factor.

Aspects of late Quaternary geomorphological development in the Khangai Mountains and the Gobi Altai Mountains (Mongolia)

NASA Astrophysics Data System (ADS)

Lehmkuhl, Frank; Nottebaum, Veit; Hülle, Daniela

2018-07-01

The reconstruction of geomorphological processes as a result of environmental change is approached by investigating and dating some fluvial, aeolian and lacustrine archives at specific locations that form a N-S basin and range transect across the Khangai Mountains south to the eastern Gobi Altai mountains in Mongolia. Geomorphological processes varied a) spatially with different climatic conditions and vegetation cover in relation to different elevation and latitude and b) temporally due to climatic shifts during the late Quaternary. In total, 15 sections from three distinct sub-regions along that transect were dated by 22 OSL ages. The Khangai Mountain sub-region exhibits mainly late Glacial to Holocene aeolian silty to sandy cover sediments mainly in the upper catchment reaches (>1800 m a.s.l.). Sections in the northern and central Gobi represent river terraces and alluvial fans in basin areas as well as aeolian sediments in the mountains above 2200 m a.s.l. The oldest terrace surface found in this study (T2; NGa1) dates to the penultimate Glacial cycle. The T1 terrace surfaces, on the northern Khangai Mountain front and in the central Gobi sub-region yield a maximum accumulation during the global Last Glacial Maximum (gLGM) and late Glacial time. During the gLGM phase represents rather sheetflow dominated transport built the alluvial fans and in late Glacial times the sediments exhibit more debrisflow controlled accumulation. Incision, forming the T1-terrace edges is therefore, supposed for the Pleistocene-Holocene transition and subsequent early Holocene. The geomorphic evidence is interpreted as stronger fluvial morphodynamics induced by enhanced humidity under beginning interglacial conditions. These processes coincided with the development of aeolian mantles at higher altitudes in the Khangai and Gobi Altai mountains where higher temperatures and humidities supported the formation of a vegetation cover, that served as a dust trap at least since late Glacial times and reduced the sediment supply on the alluvial fans.

The importance of stochasticity and internal variability in geomorphic erosion system

NASA Astrophysics Data System (ADS)

Kim, J.; Ivanov, V. Y.; Fatichi, S.

2016-12-01

Understanding soil erosion is essential for a range of studies but the predictive skill of prognostic models and reliability of national-scale assessments have been repeatedly questioned. Indeed, data from multiple environments indicate that fluvial soil loss is highly non-unique and its frequency distributions exhibit heavy tails. We reveal that these features are attributed to the high sensitivity of erosion response to micro-scale variations of soil erodibility - `geomorphic internal variability'. The latter acts as an intermediary between forcing and erosion dynamics, augmenting the conventionally emphasized effects of `external variability' (climate, topography, land use, management form). Furthermore, we observe a reduction of erosion non-uniqueness at larger temporal scales that correlates with environment stochasticity. Our analysis shows that this effect can be attributed to the larger likelihood of alternating characteristic regimes of sediment dynamics. The corollary of this study is that the glaring gap - the inherently large uncertainties and the fallacy of representativeness of central tendencies - must be conceded in soil loss assessments. Acknowledgement: This research was supported by a grant (16AWMP-B083066-03) from Water Management Research Program funded by Ministry of Land, Infrastructure and Transport of Korean government, and by the faculty research fund of Sejong University in 2016.

A centennial tribute to G.K. Gilbert's Hydraulic Mining Débris in the Sierra Nevada

NASA Astrophysics Data System (ADS)

James, L. A.; Phillips, J. D.; Lecce, S. A.

2017-10-01

G.K. Gilbert's (1917) classic monograph, Hydraulic-Mining Débris in the Sierra Nevada, is described and put into the context of modern geomorphic knowledge. The emphasis here is on large-scale applied fluvial geomorphology, but other key elements-e.g., coastal geomorphology-are also briefly covered. A brief synopsis outlines key elements of the monograph, followed by discussions of highly influential aspects including the integrated watershed perspective, the extreme example of anthropogenic sedimentation, computation of a quantitative, semidistributed sediment budget, and advent of sediment-wave theory. Although Gilbert did not address concepts of equilibrium and grade in much detail, the rivers of the northwestern Sierra Nevada were highly disrupted and thrown into a condition of nonequilibrium. Therefore, concepts of equilibrium and grade-for which Gilbert's early work is often cited-are discussed. Gilbert's work is put into the context of complex nonlinear dynamics in geomorphic systems and how these concepts can be used to interpret the nonequilibrium systems described by Gilbert. Broad, basin-scale studies were common in the period, but few were as quantitative and empirically rigorous or employed such a range of methodologies as PP105. None demonstrated such an extreme case of anthropogeomorphic change.

Channel-planform evolution in four rivers of Olympic National Park, Washington, U.S.A.: The roles of physical drivers and trophic cascades

USGS Publications Warehouse

East, Amy E.; Jenkins, Kurt J.; Happe, Patricia J.; Bountry, Jennifer A.; Beechie, Timothy J.; Mastin, Mark C.; Sankey, Joel B.; Randle, Timothy J.

2017-01-01

Identifying the relative contributions of physical and ecological processes to channel evolution remains a substantial challenge in fluvial geomorphology. We use a 74-year aerial photographic record of the Hoh, Queets, Quinault, and Elwha Rivers, Olympic National Park, Washington, U.S.A., to investigate whether physical or trophic-cascade-driven ecological factors—excessive elk impacts after wolves were extirpated a century ago—are the dominant controls on channel planform of these gravel-bed rivers. We find that channel width and braiding show strong relationships with recent flood history. All four rivers have widened significantly in recent decades, consistent with increased flood activity since the 1970s. Channel planform also reflects sediment-supply changes, evident from landslide response on the Elwha River. We surmise that the Hoh River, which shows a multi-decadal trend toward greater braiding, is adjusting to increased sediment supply associated with rapid glacial retreat. In this sediment-routing system with high connectivity, such climate-driven signals appear to propagate downstream without being buffered substantially by sediment storage. Legacy effects of anthropogenic modification likely also affect the Quinault River planform. We infer no correspondence between channel geomorphic evolution and elk abundance, suggesting that trophic-cascade effects in this setting are subsidiary to physical controls on channel morphology. Our findings differ from previous interpretations of Olympic National Park fluvial dynamics and contrast with the classic example of Yellowstone National Park, where legacy effects of elk overuse are apparent in channel morphology; we attribute these differences to hydrologic regime and large-wood availability.

Protracted fluvial recovery from medieval earthquakes, Pokhara, Nepal

NASA Astrophysics Data System (ADS)

Stolle, Amelie; Bernhardt, Anne; Schwanghart, Wolfgang; Andermann, Christoff; Schönfeldt, Elisabeth; Seidemann, Jan; Adhikari, Basanta R.; Merchel, Silke; Rugel, Georg; Fort, Monique; Korup, Oliver

2016-04-01

River response to strong earthquake shaking in mountainous terrain often entails the flushing of sediments delivered by widespread co-seismic landsliding. Detailed mass-balance studies following major earthquakes in China, Taiwan, and New Zealand suggest fluvial recovery times ranging from several years to decades. We report a detailed chronology of earthquake-induced valley fills in the Pokhara region of western-central Nepal, and demonstrate that rivers continue to adjust to several large medieval earthquakes to the present day, thus challenging the notion of transient fluvial response to seismic disturbance. The Pokhara valley features one of the largest and most extensively dated sedimentary records of earthquake-triggered sedimentation in the Himalayas, and independently augments paleo-seismological archives obtained mainly from fault trenches and historic documents. New radiocarbon dates from the catastrophically deposited Pokhara Formation document multiple phases of extremely high geomorphic activity between ˜700 and ˜1700 AD, preserved in thick sequences of alternating fluvial conglomerates, massive mud and silt beds, and cohesive debris-flow deposits. These dated fan-marginal slackwater sediments indicate pronounced sediment pulses in the wake of at least three large medieval earthquakes in ˜1100, 1255, and 1344 AD. We combine these dates with digital elevation models, geological maps, differential GPS data, and sediment logs to estimate the extent of these three pulses that are characterized by sedimentation rates of ˜200 mm yr-1 and peak rates as high as 1,000 mm yr-1. Some 5.5 to 9 km3 of material infilled the pre-existing topography, and is now prone to ongoing fluvial dissection along major canyons. Contemporary river incision into the Pokhara Formation is rapid (120-170 mm yr-1), triggering widespread bank erosion, channel changes, and very high sediment yields of the order of 103 to 105 t km-2 yr-1, that by far outweigh bedrock denudation rates inferred from cosmogenic 10Be inventories in river sands. The rapid infill of about a dozen tributary valleys displaced river channels, and caused them to re-incise into bedrock along steep epigenetic gorges. We conclude that the Pokhara Formation offers a unique archive of medieval earthquakes as well as the associated protracted fluvial response that may have been ongoing for up to 900 years.

Tectonic and climatic significance of a late Eocene low-relief, high-level geomorphic surface, Colorado

NASA Technical Reports Server (NTRS)

Gregory, Kathryn M.; Chase, Clement G

1994-01-01

New paleobotanical data suggest that in the late Eocene the erosion surface which capped the Front Range, Colorado was 2.2-2.3 km in elevation, which is similar to the 2.5-km present elevation of surface remnants. This estimated elevation casts doubt on the conventional belief that the low-relief geomorphic surface was formed by lateral planation of streams to a base level not much higher than sea level and that the present deeply incised canyons must represent Neogene uplift of Colorado. Description of the surface, calculations of sediment volume, and isostatic balance and fluvial landsculpting models demonstrate that while the high elevation of the erosion surface was due to tectonic forces, its smoothness was mostly a result of climatic factors. A sediment balance calculated for the Front Range suggests that from 2 to 4 km of material were eroded by the late Eocene, consistent with fission track ages. This amount of erosion would remove a significant portionof the 7 km of Laramide upper crustal thickening. Isostatic modeling implies that the 2.2-3.3 km elevation was most likely created by lower crustal thickening during the Laramide. A numerical model of fluvial erosion and deposition suggests a way that a late Eocene surface could have formed at this high elevation without incision. A humid climate with a preponderance of small storm events will diffusively smooth topography and is a possible mechanism for formation oflow-relief, high-level surfaces. Paleoclimate models suggest a lack of large strom events in the late Eocene because of cool sea surface temperatures in the equatorial region. Return to a drier but stormier climate post-Eocene could have caused the incision of the surface by young canyons. By this interpretation, regional erosion surfaces may represent regional climatic rather than tectonic conditions.

Geomorphic origin of Merritt Island-Cape Canaveral, Florida, USA: A paleodelta of the reversed St. Johns River?

NASA Astrophysics Data System (ADS)

Adams, Peter N.

2018-04-01

The Merritt Island-Cape Canaveral (MICCSC) sedimentary complex consists of a series of adjacent, non-conformable, beach ridge sets that suggest a multi-phase constructional history, but the feature's geomorphic and sedimentary origins are not well-understood. In spite of its notable sedimentary volume (surface area = 1200 km2), the MICCSC lacks a clear sediment source, or supply mechanism, to explain its presence today. Previously published U/Th, radiocarbon and OSL dates indicate that beach ridge deposition was active during MIS 5 (130-80 ka) on Merritt Island, but has occurred over a shorter, younger time interval on Cape Canaveral proper (6 ka to present). In this paper, it is proposed that the MICCSC is an abandoned paleodelta whose fluvial source provided a sediment supply sufficient for coastal progradation. Although the MICCSC, today, does not receive an appreciable sediment supply, the nearly 23,000 km2 drainage basin of the St. Johns River may well have provided such a sediment supply during MIS 5 times. This low-gradient fluvial system currently empties to the Atlantic Ocean some 200 km north of the MICCSC (near Jacksonville, Florida) but may have flowed southward during the time of MICCSC sedimentary construction, then experienced flow reversal since MIS 5 times. Three possible uplift mechanisms are proposed to explain the northward down-tilting that may have reversed the flow direction of the St. Johns, abandoning deltaic construction of the MICCSC: (1) karst-driven, flexural isostatic uplift in response to carbonate rock dissolution in central Florida, (2) glacio-hydro-isostatic tilting/back-tilting cycles during loading and unloading of the Laurentide ice sheet during the Pleistocene, and (3) mantle convection-driven dynamic topography operating within southeastern North America since the Pliocene. This example testifies to the sensitivity of low-gradient, low-relief landscapes to various sources of uplift, be they isostatic or otherwise.

Integrating Geomorphic and Social Dynamics in the Analysis of Anthropogenic Landforms: Examining Landscape Evolution of Terrain Modified by Agricultural Terracing

NASA Astrophysics Data System (ADS)

Glaubius, J.; Maerker, M.

2016-12-01

Anthropogenic landforms, such as mines and agricultural terraces, are impacted by both geomorphic and social processes at varying intensities through time. In the case of agricultural terraces, decisions regarding terrace maintenance are intertwined with land use, such as when terraced fields are abandoned. Furthermore, terrace maintenance and land use decisions, either jointly or separately, may be in response to geomorphic processes, as well as geomorphic feedbacks. Previous studies of these complex geomorphic systems considered agricultural terraces as static features or analyzed only the geomorphic response to landowner decisions. Such research is appropriate for short-term or binary landscape scenarios (e.g. the impact of maintained vs. abandoned terraces), but the complexities inherent in these socio-natural systems requires an approach that includes both social and geomorphic processes. This project analyzes feedbacks and emergent properties in terraced systems by implementing a coupled landscape evolution model (LEM) and agent-based model (ABM) using the Landlab and Mesa modeling libraries. In the ABM portion of the model, agricultural terraces are conceptualized using a life-cycle stages schema and implemented using Markov Decision Processes to simulate the changing geomorphic impact of terracing based on human decisions. This paper examines the applicability of this approach by comparing results from a LEM-only model against the coupled LEM-ABM model for a terraced region. Model results are compared by quantify and spatial patterning of sediment transport. This approach fully captures long-term landscape evolution of terraced terrain that is otherwise lost when the life-cycle of terraces is not considered. The coupled LEM-ABM approach balances both environmental and social processes so that the socio-natural feedbacks in such anthropogenic systems can be disentangled.

The geomorphic influences of beaver dams and failures of beaver dams

NASA Astrophysics Data System (ADS)

Butler, David R.; Malanson, George P.

2005-10-01

Uncounted millions of beaver ponds and dams existed in North America prior to European contact and colonization. These ponds acted as sediment traps that contained tens to hundreds of billions of cubic meters of sediment that would otherwise have passed through the fluvial system. Removal of beavers by overtrapping in the 16th-19th centuries severely reduced their number and the number of ponds and dams. Dam removal altered the fluvial landscape of North America, inducing sediment evacuation and entrenchment in concert with widespread reduction in the wetlands environments. Partial recovery of beaver populations in the 20th century has allowed reoccupation of the entirety of the pre-contact range, but at densities of only one-tenth the numbers. Nevertheless, modern beaver ponds also trap large volumes of sediment in the high hundred millions to low billions of cubic meters range. Failure of beaver dams is a more common phenomenon than often assumed in the literature. During the past 20 years, numerous cases of dam failure have been documented that resulted in outburst floods. These floods have been responsible for 13 deaths and numerous injuries, including significant impacts on railway lines.

Fluvial archives, a valuable record of vertical crustal deformation

NASA Astrophysics Data System (ADS)

Demoulin, A.; Mather, A.; Whittaker, A.

2017-06-01

The study of drainage network response to uplift is important not only for understanding river system dynamics and associated channel properties and fluvial landforms, but also for identifying the nature of crustal deformation and its history. In recent decades, geomorphic analysis of rivers has proved powerful in elucidating the tectonic evolution of actively uplifting and eroding orogens. Here, we review the main recent developments that have improved and expanded qualitative and quantitative information about vertical tectonic motions (the effects of horizontal deformation are not addressed). Channel long profiles have received considerable attention in the literature, and we briefly introduce basic aspects of the behaviour of bedrock rivers from field and numerical modelling perspectives, before describing the various metrics that have been proposed to identify the information on crustal deformation contained within their steady-state characteristics. Then, we review the literature dealing with the transient response of rivers to tectonic perturbation, through the production of knickpoints propagating through the drainage network. Inverse modelling of river profiles for uplift in time and space is also shown to be very effective in reconstructing regional tectonic histories. Finally, we present a synthetic morphometric approach for deducing the tectonic record of fluvial landscapes. As well as the erosional imprint of tectonic forcing, sedimentary deposits, such as fluvial terrace staircases, are also considered as a classical component of tectonic geomorphology. We show that these studies have recently benefited from rapid advances in dating techniques, allowing more reliable reconstruction of incision histories and estimation of incision rates. The combination of progress in the understanding of transient river profiles and larger, more rigorous data sets of terrace ages has led to improved understanding of river erosion and the implications for terrace profile correlation, i.e., extrapolation of local data to entire profiles. Finally, planform changes in fluvial systems are considered at the channel scale in alluvial rivers and regional level in terms of drainage reorganisation. Examples are given of how numerical modelling can efficiently combine with topographic data to shed new light on the (dis)equilibrium state of drainage systems across regional drainage divides.

Biogeomorphic feedbacks in the Southwestern USA: exploring the mechanisms of geomorphic change and the effectiveness of mitigation measures

NASA Astrophysics Data System (ADS)

Dean, D. J.; Diehl, R. M.; Topping, D. J.

2017-12-01

Water development and the proliferation of riparian plants have resulted in extensive geomorphic change to rivers worldwide. In many dryland rivers of the Southwestern U.S., these phenomena have contributed to conditions of sediment accumulation leading to channel narrowing, floodplain aggradation, and loss of fluvial habitat. Using a series of field and laboratory measurements, we demonstrate how biogeomorphic feedbacks have promoted channel contraction. Experimental evidence shows that vegetation can have a substantial effect on local hydraulics and sediment-transport fields, depending on plant morphology, but that the impact of plants on physical processes is mediated by flow and sediment supply. In the Little Colorado River in Arizona, water management practices, variations in climate/hydrology, and the resultant expansion of riparian vegetation have resulted in channel narrowing, increases in sinuosity and drag, and decreases in channel slope. These changes have created a biogeomorphic feedback by disrupting downstream flood conveyance; flood travel time has increased resulting in flow attenuation, declines in peak discharge, and continued sediment accumulation at large scales. In the Rio Grande in Big Bend National Park, channel narrowing and floodplain aggradation has led to the loss of channel capacity and an increase in overbank flooding even though discharges have declined. Vegetation expansion into channel environments has exacerbated this condition by reducing channel-margin flow velocities, increasing sediment deposition, and reducing bank erosion thereby creating a biogeomorphic feedback leading to additional narrowing. An understanding of the mechanisms that have driven geomorphic changes in river channels may help to formulate effective mitigation measures. Vegetation removal can have local and reach-scale effects on channel morphology; however, the effectiveness of these actions is dependent upon many variables including the flow regime and upstream sediment supply. At larger scales, the construction of continuous mass-balance sediment budgets, such as on the Rio Grande and the Yampa and Green rivers in Dinosaur National Monument, can help managers tailor upstream water releases required to maintain sufficient channel complexity or to maximize sediment export.

Geomorphic consequences of rapid deglaciation at Pasterze Glacier, Hohe Tauern Range, Austria, between 2010 and 2013 based on repeated terrestrial laser scanning data

NASA Astrophysics Data System (ADS)

Avian, M.; Kellerer-Pirklbauer, A.; Lieb, G. K.

2018-06-01

Since the end of the Little Ice Age around 1850 CE glaciers in the Alps have been receding dramatically. This study aimed to quantify and characterize the geomorphic and landform changes of a 0.9 km2 large proglacial area at the largest glacier in Austria (Pasterze Glacier, Austria, N 47°04‧, E 12°44‧). Point clouds from multiple terrestrial laserscanning (TLS) and different image data were used to quantify surface elevation changes and distinguish different types of erosional and depositional landforms during the period 2010-2013. Results indicate that the study area is characterized by a total volume loss of 1,309,000 m3. Excluding the area which was deglaciated, the volume loss equals 275,000 m3 in the period 2010-13. The decrease is related to sediment transfer out of study area and due to sediment-buried glacier ice which is slowly melting. The landform classification reveals that drift mantled slopes are most frequent (20.9% of the study area in 2013) next to ice contact terrace landforms (19.7%). In terms of vertical surface elevation changes, our results suggest distinguishing between 3 distinct domains within the study area: (i) a flat valley bottom area consisting of water/sandur areas and ice-cored landforms dominated by widespread subsurface ice melting and lateral fluvial (and thermal) erosion; (ii) a gently-sloping footslope area consisting of ice-contact sediments, former ice marginal channels and deep incised gullies with corresponding debris cones dominated by linear erosion and corresponding deposition; and (iii) a steep lateral slope area mainly built up of consolidated drift material with incised gullies dominated by linear erosion. Our results not only confirm the previously revealed high geomorphic activity for proglacial areas of alpine glaciers in terms of surface elevation variations, they also highlight that landforms might change substantially from one year to the next not only because of erosional/depositional processes, but also because of the melting of buried dead-ice bodies.

In-Situ Dating on Mars: The Potential of OSL Dating

NASA Technical Reports Server (NTRS)

Blair, M. W.; Kalchgruber, R.; Yukihara, E. G.; Bulur, E.; Kim, S. S.; McKeever, W. S.

2004-01-01

More and more evidence is being accumulated that Mars has experienced aeolian, fluvial, and periglacial activity in the (relatively) recent past [1, 2, 3]. However, the temporal scale on which these processes took place is very poorly constrained since crater counting has errors comparable to the age for younger terrains (approx. 1 Ma). Consequently, many researchers have called for methods to establish the climatic and geomorphic history of Mars [4]. Lepper and McKeever [5] suggested developing optically stimulated luminescence (OSL) dating techniques for in-situ dating of martian sediments. Electron paramagnetic resonance (EPR) is closely related to OSL and could easily be incorporated on the same instrument platform [6]. These two methods can aid in developing a geological and climatic history of Mars over the last approx. one million years. Since the initial investigations, work has been carried out to develop OSL instrumentation and dating procedures that are suitable to the unique challenges of the martian environment. In this paper, we highlight the advances made in this project, focusing on OSL dating principles, assumptions, and procedures.

Geomorphic evidence for an eolian contribution to the formation of the Martian northern plains

NASA Technical Reports Server (NTRS)

Zimbelman, J. R.

1993-01-01

The northern plains of Mars have many morphologic characteristics that are uncommon or absent on the rest of the planet. Mariner 9 and Viking images obtained north of latitude 30 deg N revealed 'smooth' and 'mottled' plains of an uncertain origin. Some or all of the northern plains were interpreted to consist of lava plains intermixed with eolian and volcanic materials thick eolian mantles that buried portions of the mid latitudes periglacial deposits resulting from the presence of ground ice and as water-transported sediments derived from fluvial runoff, lacustrine deposition in standing bodies of water, or glacial runoff. The highest-resolution Viking images show many intriguing details that may provide clues to the origin of this complex and distinctive terrain. Some of the informative features present in the best Viking images, comparing the observations to what may be expected from various hypotheses of formation, are reviewed. While the results are not conclusive for any single hypothesis, eolian processes have played a major role in the erosion (and possibly deposition) of the materials that make up the surface exposures in the Martian northern plains.

The Importance of Long Wavelength Processes in Generating Landscapes

NASA Astrophysics Data System (ADS)

Roberts, Gareth G.; White, Nicky

2017-04-01

The processes responsible for generating landscapes observed on Earth and elsewhere are poorly understood. For example, the relative importance of long (>10 km) and short wavelength erosional processes in determining the evolution of topography is debated. Much work has focused on developing an observational and theoretical framework for evolution of longitudinal river profiles (i.e. elevation as a function of streamwise distance), which probably sets the pace of erosion in low-mid latitude continents. A large number of geomorphic studies emphasis the importance of short wavelength processes in sculpting topography (e.g. waterfall migration, interaction of biota and the solid Earth, hill slope evolution). However, it is not clear if these processes scale to generate topography observed at longer (>10 km) wavelengths. At wavelengths of tens to thousands of kilometers topography is generated by modification of the lithosphere (e.g. shortening, extension, flexure) and by sub-plate processes (e.g. dynamic support). Inversion of drainage patterns suggests that uplift rate histories can be reliably recovered at these long wavelengths using simple erosional models (e.g. stream power). Calculated uplift and erosion rate histories are insensitive to short wavelength (<10 km) or rapid (<100 ka) environmental changes (e.g. biota, precipitation, lithology). One way to examine the relative importance of short and long wavelength processes in generating topography is to transform river profiles into distance-frequency space. We calculate the wavelet power spectrum of a suite of river profiles and examine their spectral content. Big rivers in North America (e.g. Colorado, Rio Grande) and Africa (e.g. Niger, Orange) have a red noise spectrum (i.e. power inversely proportional to wavenumber-squared) at wavelengths > 100 km. More than 90% of river profile elevations in our inventory are determined at these wavelengths. At shorter wavelengths spectra more closely resemble pink noise (power inversely proportional to wavenumber). These observations suggest that short wavelength processes do not simply scale to generate the long wavelength changes in elevation. Instead we suggest that long wavelength processes (e.g. regional uplift, knickzone migration) determine the shape and evolution of nearly all topography. These results suggest that the erosional complexity observed in local geomorphic studies and the relative simplicity of erosional models required to fit continental-scale drainage patterns are not mutually exclusive. Rather that the problem of fluvial erosion is being tackled at different and probably unrelated scales.

An optical age chronology of late Quaternary extreme fluvial events recorded in Ugandan dambo soils

USGS Publications Warehouse

Mahan, S.A.; Brown, D.J.

2007-01-01

There is little geochonological data on sedimentation in dambos (seasonally saturated, channel-less valley floors) found throughout Central and Southern Africa. Radiocarbon dating is problematic for dambos due to (i) oxidation of organic materials during dry seasons; and (ii) the potential for contemporary biological contamination of near-surface sediments. However, for luminescence dating the equatorial site and semi-arid climate facilitate grain bleaching, while the gentle terrain ensures shallow water columns, low turbidity, and relatively long surface exposures for transported grains prior to deposition and burial. For this study, we focused on dating sandy strata (indicative of high-energy fluvial events) at various positions and depths within a second-order dambo in central Uganda. Blue-light quartz optically stimulated luminescences (OSL) ages were compared with infrared stimulated luminescence (IRSL) and thermoluminescence (TL) ages from finer grains in the same sample. A total of 8 samples were dated, with 6 intervals obtained at ???35, 33, 16, 10.4, 8.4, and 5.9 ka. In general, luminescence ages were stratigraphically, geomorphically and ordinally consistent and most blue-light OSL ages could be correlated with well-dated climatic events registered either in Greenland ice cores or Lake Victoria sediments. Based upon OSL age correlations, we theorize that extreme fluvial dambo events occur primarily during relatively wet periods, often preceding humid-to-arid transitions. The optical ages reported in this study provide the first detailed chronology of dambo sedimentation, and we anticipate that further dambo work could provide a wealth of information on the paleohydrology of Central and Southern Africa. ?? 2006 Elsevier Ltd. All rights reserved.

Estuarine abandoned channel sedimentation rates record peak fluvial discharge magnitudes

NASA Astrophysics Data System (ADS)

Gray, A. B.; Pasternack, G. B.; Watson, E. B.

2018-04-01

Fluvial sediment deposits can provide useful records of integrated watershed expressions including flood event magnitudes. However, floodplain and estuarine sediment deposits evolve through the interaction of watershed/marine sediment supply and transport characteristics with the local depositional environment. Thus extraction of watershed scale signals depends upon accounting for local scale effects on sediment deposition rates and character. This study presents an examination of the balance of fluvial sediment dynamics and local scale hydro-geomorphic controls on alluviation of an abandoned channel in the Salinas River Lagoon, CA. A set of three sediment cores contained discrete flood deposits that corresponded to the largest flood events over the period of accretion from 1969 to 2007. Sedimentation rates scaled with peak flood discharge and event scale sediment flux, but were not influenced by longer scale hydro-meteorological activities such as annual precipitation and water yield. Furthermore, the particle size distributions of flood deposits showed no relationship to event magnitudes. Both the responsiveness of sedimentation and unresponsiveness of particle size distributions to hydro-sedimentological event magnitudes appear to be controlled by aspects of local geomorphology that influence the connectivity of the abandoned channel to the Salinas River mainstem. Well-developed upstream plug bar formation precluded the entrainment of coarser bedload into the abandoned channel, while Salinas River mouth conditions (open/closed) in conjunction with tidal and storm surge conditions may play a role in influencing the delivery of coarser suspended load fractions. Channel adjacent sediment deposition can be valuable records of hydro-meteorological and sedimentological regimes, but local depositional settings may dominate the character of short term (interdecadal) signatures.

Riparian soil development linked to forest succession above and below dams along the Elwha River, Washington, USA

USGS Publications Warehouse

Perry, Laura G; Shafroth, Patrick B.; Perakis, Steven

2017-01-01

Riparian forest soils can be highly dynamic, due to frequent fluvial disturbance, erosion, and sediment deposition, but effects of dams on riparian soils are poorly understood. We examined soils along toposequences within three river segments located upstream, between, and downstream of two dams on the Elwha River to evaluate relationships between riparian soil development and forest age, succession, and channel proximity, explore dam effects on riparian soils, and provide a baseline for the largest dam removal in history. We found that older, later-successional forests and geomorphic surfaces contained soils with finer texture and greater depth to cobble, supporting greater forest floor mass, mineral soil nutrient levels, and cation exchange. Forest stand age was a better predictor than channel proximity for many soil characteristics, though elevation and distance from the channel were often also important, highlighting how complex interactions between fluvial disturbance, sediment deposition, and biotic retention regulate soil development in this ecosystem. Soils between the dams, and to a lesser extent below the lower dam, had finer textures and higher mineral soil carbon, nitrogen, and cation exchange than above the dams. These results suggested that decreased fluvial disturbance below the dams, due to reduced sediment supply and channel stabilization, accelerated soil development. In addition, reduced sediment supply below the dams may have decreased soil phosphorus. Soil δ15N suggested that salmon exclusion by the dams had no discernable effect on nitrogen inputs to upstream soils. Recent dam removal may alter riparian soils further, with ongoing implications for riparian ecosystems.

Sedimentology of new fluvial deposits on the Elwha River, Washington, USA, formed during large-scale dam removal

USGS Publications Warehouse

Draut, Amy; Ritchie, Andrew C.

2015-01-01

Removal of two dams 32 m and 64 m high on the Elwha River, Washington, USA, provided the first opportunity to examine river response to a dam removal and controlled sediment influx on such a large scale. Although many recent river-restoration efforts have included dam removal, large dam removals have been rare enough that their physical and ecological effects remain poorly understood. New sedimentary deposits that formed during this multi-stage dam removal result from a unique, artificially created imbalance between fluvial sediment supply and transport capacity. River flows during dam removal were essentially natural and included no large floods in the first two years, while draining of the two reservoirs greatly increased the sediment supply available for fluvial transport. The resulting sedimentary deposits exhibited substantial spatial heterogeneity in thickness, stratal-formation patterns, grain size and organic content. Initial mud deposition in the first year of dam removal filled pore spaces in the pre-dam-removal cobble bed, potentially causing ecological disturbance but not aggrading the bed substantially at first. During the second winter of dam removal, thicker and in some cases coarser deposits replaced the early mud deposits. By 18 months into dam removal, channel-margin and floodplain deposits were commonly >0.5 m thick and, contrary to pre-dam-removal predictions that silt and clay would bypass the river system, included average mud content around 20%. Large wood and lenses of smaller organic particles were common in the new deposits, presumably contributing additional carbon and nutrients to the ecosystem downstream of the dam sites. Understanding initial sedimentary response to the Elwha River dam removals will inform subsequent analyses of longer-term sedimentary, geomorphic and ecosystem changes in this fluvial and coastal system, and will provide important lessons for other river-restoration efforts where large dam removal is planned or proposed.

Great Basin paleoenvironmental studies project; Third quarterly technical progress report, December 1993--February 1994

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1994-04-01

Examination of the paleolithic and geomorphic records to determine the local and regional impact of past climates will advance assessment of Yucca Mountain`s suitability as a high-level nuclear waste repository. The project includes the integration of botanical, faunal, and geomorphic components to accomplish this goal. Paleobotanical studies will reconstruct the response of vegetation to climate change at the community and the organismal levels by integrating data obtained from nearly continuous sediment records of pollen, plant macrofossils, and stable isotopes from fossil woodrat middens. The goal of the paleofaunas study is to construct a history of Great Basin vertebrates, particularly mammals,more » that will provide empirical evidence of past environmental and climatic conditions within the Great Basin as it is recorded by the animals. Taxonomic composition of archaeological and paleontological faunas from various areas within the Great Basin and morphological change within individual mammalian taxa at specific localities are being investigated to monitor faunal response to changing environmental conditions. The objective of the geomorphology component of the paleoenvironmental program is to document the responses of surficial processes and landforms to the climatic changes documented by studies of packrat middens, pollen, and faunal distributions. The project will focus on: (1) stratigraphic relationships between lake deposits and aeolian or fluvial sediments and landforms; (2) cut and fill sequences in floodplain and river-channel deposits; (3) identification of periods of dune mobility and stability; (4) documentation of episodes of alluvial fan and terrace development and erosion; and (5) correlation of (3) and (4) to climatically driven lake-level fluctuation as revealed by shoreline features such as strandlines and beach ridges. Accomplishments for this period are presented for these studies.« less

Observations of Near-Bed Deposition and Resuspension Processes at the Fluvial-Tidal Transition Using High Resolution Adcp, Adv, and Lisst

NASA Astrophysics Data System (ADS)

Haught, D. R.; Stumpner, P.

2012-12-01

Processes that determine deposition and resuspension of sediment in fluvial and tidal systems are complicated and difficult to predict because of turbulence-sediment interaction. In fluvial systems net sediment deposition rates near the bed are determined by shear stresses that occur when turbulence interacts with the bed and the entrained sediment above. In tidal systems, processes are driven primarily by the confounding factors of slack water and reversing flow. In this study we investigate near-bed sediment fluxes, settling velocities and sediment size distributions during a change from a fluvial signal to a tidal signal. In order to examine these processes a high resolution, high frequency ADCP, ADV, water quality sonde and LISST data were collocated at the fluvial-tidal transition in the Sacramento River at Freeport, CA. Data were collected at 15-30 minute increments for a month`. Data were dissevered into fluvial and tidal components. Acoustic backscatterence was used as a surrogate to sediment concentration and sediment flux () was calculated from the turbulence properties. Settling velocities were computed from the diffusion-advection equation assuming equilibrium of settling and re-suspension fluxes. Particle density was back-calculated from median particle diameter and calculated settling velocities (Reynolds number<0.5) using Stokes' law. Preliminary results suggest that during peak fluvial discharge that the diffusion-advection gives poor estimates of settling velocities as inferred from particle densities above 3500 kg/m3. During the transition from fluvial to tidal signal and throughout the tidal signal particle densities range from 2650 kg/m3 to 1000 kg/m3, suggesting that settling velocities were accurately estimated. Thus the equilibrium assumption appears poor during high fluvial discharge and reasonable during low fluvial discharge when tidal signal is dominant.

Present Permafrost Thaw in Central Yakutia, North-East Siberia: Surficial Geology and Hydrology Evidence

NASA Astrophysics Data System (ADS)

Czerniawska, Jolanta; Chlachula, Jiri

2017-04-01

Current climate change in the high-latitudes of Eurasia is a generally accepted phenomenon characterized by increased annual temperature values and marked weather anomalies observed in the sub-polar and polar regions. In the northern and NE Siberia, this trend of the MAT rise, documented particularly over the last three decades, is believed to account for the territorial lowland as well as insular mountain frozen ground thaw that in turn has triggered ecosystem feedbacks on the local as well as regional scales. In the northern regions of Yakutia, this is principally witnessed by accelerated near-surface dynamics of seasonally activated de-freezing grounds and inter-linked geomorphic and hydrological actions affecting large-scale tundra landscape settings. In the southern and central taiga-forest areas with perennial alpine and continuous permafrost conditions, respectively, an increased depth of the seasonally melted top-soil layers has become evident accompanied by thermokarst lake expansion and ground surface collapsing. Some cryogenic depressions generated from small gullies over the past decades eloquently demonstrate the intensity and scales of the current permafrost degradation in the Siberian North. The fluvial discharge is most dynamic in late spring to mid-summer because of the cumulative effect of snow-melting because of a high solar radiation and short intervals of torrential rains. Yet, the climate-change-dependent and most active geomorphic agent is the accelerated permafrost thaw seen in landslides and tundra-forest cover decay due to a higher water table. Numerous preserved biotic fossiliferous records Pleistocene and early Holocene in age are being exposed in this process providing unique palaeoecology evidence at particular sites. These climate-generated processes have mostly highly negative effects to the natural habitats (migratory animal routes and riverine biota due to an earlier ice-melting) as well as the local settlement communities (infrastructure destruction resulting from the top-ground melt-water saturation, road-base disintegration, slope slumping, drinking water supply, etc.).

Geomorphic predictors of riparian vegetation in small mountain watersheds

Treesearch

Blake M. Engelhardt; Jeanne C. Chambers; Peter J. Weisberg

2015-01-01

Hydrogeomorphic processes operating at watershed, process zone and site scales influence the distribution of riparian vegetation. However, most studies examining the relationships between hydrogeomorphic processes and riparian vegetation are conducted at site scales. We quantified the relative importance of watershed, process zone and site geomorphic characteristics...

Human-induced shifts in geomorphic process rates: An example of landslide activity following forest cover change.

NASA Astrophysics Data System (ADS)

Guns, Marie; Balthazar, Vincent; Vanacker, Veerle

2013-04-01

Mountain regions present unique challenges and opportunities to land use change research. Very few, if any, mountain ecosystems remain unaffected by human impact. Based on the exemplary evidence from local case studies, it is not yet possible to have an overall assessment of the extent and impact of human activities on mountain erosion as mountain regions are typically characterized by rapid changes in geomorphic, cryospheric, climatic, hydrologic, ecological and socio-economic conditions over relatively short distances. Here, we present a conceptual model that allows evaluating human-induced shifts in geomorphic process rates. The basic idea behind this model is that the magnitude-frequency distribution of geomorphic processes is dependent on the intensity of human disturbance. The conceptual model is here applied for characterising landslide activity following forest cover change. We selected a tropical Andean catchment with a deforestation rate of 1.4% over the last 45 years. Landslide inventories were established based on historical aerial photographs (1963, 1977, and 1989) and very high-resolution satellite images (2010). Statistical analyses show that the total number of landslides is rising, and that they are increasingly associated with human disturbances (deforestation, road construction). This is particularly the case for shallow landslides that become more frequent after clearcutting. As the human-induced shifts in landslide activity are significant for the low-magnitude events only, the total impact on geomorphic process rates is rather limited in this particular area. This work shows that including information on the magnitude-frequency of geomorphic events before, during and after human disturbances offers new possibilities to quantify the complex response of geomorphic processes to human disturbances.

Multi-scale interactions affecting transport, storage, and processing of solutes and sediments in stream corridors (Invited)

NASA Astrophysics Data System (ADS)

Harvey, J. W.; Packman, A. I.

2010-12-01

Surface water and groundwater flow interact with the channel geomorphology and sediments in ways that determine how material is transported, stored, and transformed in stream corridors. Solute and sediment transport affect important ecological processes such as carbon and nutrient dynamics and stream metabolism, processes that are fundamental to stream health and function. Many individual mechanisms of transport and storage of solute and sediment have been studied, including surface water exchange between the main channel and side pools, hyporheic flow through shallow and deep subsurface flow paths, and sediment transport during both baseflow and floods. A significant challenge arises from non-linear and scale-dependent transport resulting from natural, fractal fluvial topography and associated broad, multi-scale hydrologic interactions. Connections between processes and linkages across scales are not well understood, imposing significant limitations on system predictability. The whole-stream tracer experimental approach is popular because of the spatial averaging of heterogeneous processes; however the tracer results, implemented alone and analyzed using typical models, cannot usually predict transport beyond the very specific conditions of the experiment. Furthermore, the results of whole stream tracer experiments tend to be biased due to unavoidable limitations associated with sampling frequency, measurement sensitivity, and experiment duration. We recommend that whole-stream tracer additions be augmented with hydraulic and topographic measurements and also with additional tracer measurements made directly in storage zones. We present examples of measurements that encompass interactions across spatial and temporal scales and models that are transferable to a wide range of flow and geomorphic conditions. These results show how the competitive effects between the different forces driving hyporheic flow, operating at different spatial scales, creates a situation where hyporheic fluxes cannot be accurately estimated without considering multi-scale effects. Our modeling captures the dominance of small-scale features such as bedforms that drive the majority of hyporheic flow, but it also captures how hyporheic flow is substantially modified by relatively small changes in streamflow or groundwater flow. The additional field measurements add sensitivity and power to whole stream tracer additions by improving resolution of the relative importance of storage at different scales (e.g. bar-scale versus bedform-scale). This information is critical in identifying hot spots where important biogeochemical reactions occur. In summary, interpreting multi-scale interactions in streams requires models that are physically based and that incorporate non-linear process dynamics. Such models can take advantage of increasingly comprehensive field data to integrate transport processes across spatially variable flow and geomorphic conditions. The most useful field and modeling approaches will be those that are simple enough to be easily implemented by users from various disciplines but comprehensive enough to produce meaningful predictions for a wide range of flow and geomorphic scenarios. This capability is needed to support improved strategies for protecting stream ecological health in the face of accelerating land use and climate change.

Fish and fire: Post-wildfire sediment dynamics and implications for the viability of trout populations

NASA Astrophysics Data System (ADS)

Murphy, B. P.; Czuba, J. A.; Belmont, P.; Budy, P.; Finch, C.

2017-12-01

Episodic events in steep landscapes, such as wildfire and mass wasting, contribute large pulses of sediment to rivers and can significantly alter the quality and connectivity of fish habitat. Understanding where these sediment inputs occur, how they are transported and processed through the watershed, and their geomorphic effect on the river network is critical to predicting the impact on ecological aquatic communities. The Tushar Mountains of southern Utah experienced a severe wildfire in 2010, resulting in numerous debris flows and the extirpation of trout populations. Following many years of habitat and ecological monitoring in the field, we have developed a modeling framework that links post-wildfire debris flows, fluvial sediment routing, and population ecology in order to evaluate the impact and response of trout to wildfire. First, using the Tushar topographic and wildfire parameters, as well as stochastic precipitation generation, we predict the post-wildfire debris flow probabilities and volumes of mainstem tributaries using the Cannon et al. [2010] model. This produces episodic hillslope sediment inputs, which are delivered to a fluvial sediment, river-network routing model (modified from Czuba et al. [2017]). In this updated model, sediment transport dynamics are driven by time-varying discharge associated with the stochastic precipitation generation, include multiple grain sizes (including gravel), use mixed-size transport equations (Wilcock & Crowe [2003]), and incorporate channel slope adjustments with aggradation and degradation. Finally, with the spatially explicit adjustments in channel bed elevation and grain size, we utilize a new population viability analysis (PVA) model to predict the impact and recovery of fish populations in response to these changes in habitat. Our model provides a generalizable framework for linking physical and ecological models and for evaluating the extirpation risk of isolated fish populations throughout the Intermountain West to the increasing threat of wildfire.

Land Use and Climate Impacts on Fluvial Systems (LUCIFS): A PAGES - Focus 4 (PHAROS) research activity

NASA Astrophysics Data System (ADS)

Dearing, John; Hoffmann, Thomas

2010-05-01

LUCIFS is a global research program which is concerned with understanding past interactions between climate, human activity and fluvial systems. Its focus is on evaluating the geomorphic impact of humans on landscapes, with a strong emphasis on geomorphological and sedimentological perspectives on mid- to long-term man-landscape interactions. Of particular relevance are aspects of sediment redistribution systems such as non-linear behaviour, the role of system configuration, scale effects, and emergent properties Over the last decade the LUCIFS program has been investigating both contemporary and long-term river response to global change with the principal aims of i)quantifying land use and climate change impacts of river-borne fluxes of water, sediment, C, N and P; ii) identification of key controls on these fluxes at the catchment scale; and iii) identification of the feedback on both human society and biogeochemical cycles of long-term changes in the fluxes of these materials The major scientific tasks of the LUCIFS-program are: • synthesising results of regional case studies • identify regional gaps and encouraging new case studies • addressing research gaps and formulating new research questions • organising workshops and conferences In this paper we present the LUCIFS program within the new PAGES structure. LUCIFS is located in the Focus 4 (PHAROS) dealing with how a knowledge of human-climate-ecosystem interactions in the past can help inform understanding and management today. In conjunction with the other working groups HITE (Human Impacts on Terrestrial Ecosystems), LIMPACS (Human Impacts on Lake Ecosystems) and IHOPE (Integrated History of People on Earth) PHAROS aims to compare regional-scale reconstructions of environmental and climatic processes using natural archives, documentary and instrumental data, with evidence of past human activity obtained from historical, paleoecological and archaeological records.

James Dwight Dana and John Strong Newberry in the US Pacific Northwest: The roots of American fluvialism

USGS Publications Warehouse

O'Connor, Jim E.

2018-01-01

Recognition of the power of rivers to carve landscapes transformed geology and geomorphology in the late nineteenth century. Wide acceptance of this concept—then known as “fluvialism”—owes to many factors and people, several associated with exploration of western North America. Especially famous are the federal geographic and geologic surveys of the US Southwest with John Wesley Powell and Grove Karl Gilbert, which produced key insights regarding river processes. Yet earlier and less-known surveys also engaged young geologists embarking on tremendously influential careers, particularly the 1838–1842 US Exploring Expedition with James Dwight Dana and the 1853–1855 railroad surveys including John Strong Newberry. Informed but little constrained by European and British perspectives on landscape formation, Dana and Newberry built compelling cases for the erosive power of rivers, largely from observations in the US Pacific Northwest. They seeded the insights of the later southwestern surveys, Dana by his writings and station at Yale and his hugely influential Manual of Geology, published in 1863, and Newberry by becoming the first geologist to explore the dramatic river-carved canyons of the Southwest and then a forceful proponent of the federal surveys spotlighting the erosional landscapes. Newberry also gave Gilbert his start as a geologist. Although Dana and Newberry are renowned early American geologists, their geomorphic contributions were overshadowed by the works of Powell, Gilbert, and William Morris Davis. Yet Dana and Newberry were the first ardent American proponents of fluvialism, providing strong roots that in just a few decades transformed western geology, roots nourished in large measure by the geologically fertile landscapes of the US Pacific Northwest.

Hydrated mineral stratigraphy of Ius Chasma, Valles Marineris

USGS Publications Warehouse

Roach, L.H.; Mustard, J.F.; Swayze, G.; Milliken, R.E.; Bishop, J.L.; Murchie, S.L.; Lichtenberg, K.

2010-01-01

New high-resolution spectral and morphologic imaging of deposits on walls and floor of Ius Chasma extend previous geomorphic mapping, and permit a new interpretation of aqueous processes that occurred during the development of Valles Marineris. We identify hydrated mineralogy based on visible-near infrared (VNIR) absorptions. We map the extents of these units with CRISM spectral data as well as morphologies in CTX and HiRISE imagery. Three cross-sections across Ius Chasma illustrate the interpreted mineral stratigraphy. Multiple episodes formed and transported hydrated minerals within Ius Chasma. Polyhydrated sulfate and kieserite are found within a closed basin at the lowest elevations in the chasma. They may have been precipitates in a closed basin or diagenetically altered after deposition. Fluvial or aeolian processes then deposited layered Fe/Mg smectite and hydrated silicate on the chasma floor, postdating the sulfates. The smectite apparently was weathered out of Noachian-age wallrock and transported to the depositional sites. The overlying hydrated silicate is interpreted to be an acid-leached phyllosilicate transformed from the underlying smectite unit, or a smectite/jarosite mixture. The finely layered smectite and massive hydrated silicate units have an erosional unconformity between them, that marks a change in surface water chemistry. Landslides transported large blocks of wallrock, some altered to contain Fe/Mg smectite, to the chasma floor. After the last episode of normal faulting and subsequent landslides, opal was transported short distances into the chasma from a few m-thick light-toned layer near the top of the wallrock, by sapping channels in Louros Valles. Alternatively, the material was transported into the chasma and then altered to opal. The superposition of different types of hydrated minerals and the different fluvial morphologies of the units containing them indicate sequential, distinct aqueous environments, characterized by alkaline, then circum-neutral, and finally very acidic surface or groundwater chemistry. ?? 2009 Elsevier Inc. All rights reserved.

A pan-Arctic Assessment of Hydraulic Geometry

NASA Astrophysics Data System (ADS)

Chen, H. Z. D.; Gleason, C. J.

2016-12-01

Arctic Rivers are a crucial part of the global hydrologic cycle, especially as our climate system alters toward an uncertain future. These rivers have many ecological and societal functions, such as funneling meltwater to the ocean and act as critical winter transport for arctic communities. Despite this importance, their fluvial geomorphology, in particular their hydraulic geometry (HG) is not fully understood due to their often remote locations. HG, including at-a-station (AHG), downstream (DHG), and the recently discovered At-many-stations (AMHG), provides the empirical basis between gauging measurements and how rivers respond to varying flow conditions, serving as an indicator to the critical functions mentioned above. Hence, a systematic cataloging of the AHG, DHG, and AMHG, of Arctic rivers is needed for a pan-Arctic view of fluvial geomorphic behavior. This study will document the width-based AHG, DHG, and AMHG for rivers wider than 120m with an Arctic Ocean drainage and gauge data with satellite records. First, we will make time-series width measurements from classified imagery at locations along all such rivers from Landsat archive since 1984, accessed within the Google Earth Engine cloud computing environment. Second, we will run available gauge data for width-based AHG, DHG, and AMHG over large river reaches. Lastly, we will assess these empirical relationships, seek regional trends, and changes in HG over time as climate change has on the Arctic system. This is part of an ongoing process in the larger scope of data calibration/validation for the Surface Water and Ocean Topography (SWOT) satellite planned for 2020, and HG mapping will aid the selection of field validation sites. The work showcase an unprecedented opportunity to process and retrieve scientifically significant HG data in the often inaccessible Arctic via Google Earth Engine. This unique platform makes such broad scale study possible, providing a blueprint for future large-area HG research.

Geologic map of MTM -40252 and -40257 quadrangles, Reull Vallis region of Mars

USGS Publications Warehouse

Mest, Scott C.; Crown, David A.

2002-01-01

Mars Transverse Mercator (MTM) quadrangles -40252 and -40257 cover a portion of the highlands of Promethei Terra northeast of the Hellas basin. The map area consists of heavily cratered ancient highland materials of moderate to high relief, isolated knobs and massifs of rugged mountainous materials, extensive tracts of smooth and channeled plains, and other surficial deposits. Reull Vallis, an approximately 1,500 km-long outflow channel system, cuts through the southeast corner of the map area. Regional slopes are to the southwest, toward the Hellas basin, as indicated by Martian topographic maps and the orientations of channels along the northeast rim of the Hellas basin. The Martian highlands cover more than 60 percent of the planet's surface and are primarily in the southern hemisphere. Most of the highlands consist of rugged, densely cratered terrains believed to represent the final phase of heavy bombardment in the inner solar system about 4.0 billion years ago. Parts of the Martian highlands show evidence of extensive degradation and modification. The map area shows landforms created by numerous geologic processes, including tectonism, fluvial activity, and mass wasting. The occurrence of fluvial features, such as outflow channels and valley networks, has significant implications for past Martian conditions. Determining the geology of the highlands northeast of the Hellas basin provides a better understanding of the role and timing of volatile-driven activity in the evolution of the highlands. Photogeologic mapping at 1:500,000 scale from analysis of Viking Orbiter images complements geomorphic studies of Reull Vallis and other highland outflow systems, of drainage networks, and of highland debris aprons and regional geologic mapping studies of the highlands at the 1:2,000,000 scale and 1:1,000,000 scale. Crater size-frequency distributions have been compiled to constrain the relative ages of geologic units and determine the timing and extents of the observed geologic processes.

Monitoring morphological changes in an arid zone by spaceborne images and aerial photography between 1945 - 2009; the Yamin Plateau, Israel

NASA Astrophysics Data System (ADS)

Hetz, Guy; Blumberg, Dan; Avraham, Dody; Cohen, Hai

2010-05-01

This research focuses on a geomorphic mapping of the Yamin Plateau in southern Israel which is part of the Yamin-Rotem Syncline and covers about 200 km2. This area has been restricted since the 1950s and therefore, provides a unique opportunity to study undisturbed geomorphic processes. Nowadays, the national nuclear waste depository is located in this area accepting waste from industrial factories, research institutes and hospitals. This is the main reason why environmental processes are of major interest in terms of landform changes in space and time. The exposed geology section of the Yamin Plateau mostly consists of the Miocene Hazeva Group where sedimentary processes started 20 million years ago and continued for 12-14 million years. Two formations of the Miocene Hazeva Group appear in the study area Zefa and Rotem. The compositions of these two formations are similar and sometimes defined as "the main sand body" in the Hazeva Group. The restriction of the area stopped the grazing and let the development of a biological soil crust on the surface. The research objective was to document and characterize landform changes from 1945 until 2009 within the Yamin Plateau based on spaceborne images and aerial photography. All the parameters we extracted in the laboratory were validated with field measurements. A combination of the spaceborne images, aerial photography and field measurements leads us to the following conclusions: The research results show that soil stabilization processes took place earlier than the area closure. Inspite of decreasing precipitation tendencies as measured during the last 50 years in Yamin Plateau, the vegetation cover increased from 55% in 1945 to 67% in 2009. The main reason for this is the area closure and reduction in grazing along with developing of vegetation and biological soil crusts. Field studies and image processing of aerial photographs and recent QuickBird images alongside grain-size distribution show that in the past there were active zibar morphologies in the region. The most frequent grain-size of 350 μm supports this. Although the current geology map of the Yamin Plateau is characterized by sand soil texture, nowadays the study area surface contains 50% of clay minerals, which were probably trapped by soil crusts during dust storms. A grain size analysis shows the dominance of medium-coarse sand (350 μm) that partially mantle the Yamin Plateau surface. Aeolian activity that took place in the past and was concentrated in the southern and eastern parts of the plateau and included linear zibars. We also present a new index, the Clay Crust Index (CCI) that includes the combination of the Crust Index and the 7-th band of the Landsat TM that covers the clay absorption range. The idea behind this combination is based on trapping of clays by biological soil crusts which deepens the absorption feature in the spectrum of 7-th band of the Landsat TM. From 1945 to 2004 there were no evidence that indicate aeolian nor fluvial activities. Yet, a single extreme rain event that took place in 29 October 2004 caused the largest landform changes in the past 60 years. The runoff widened in the eastern channel streams. To summarize, the study area's closure in the late 1950's had contributed to the decrease of aeolian processes. The fluvial processes are very limited, yet, when there is an unusually large rainstorm event there is a risk of undermining and extreme erosion processes, especially when the surface is covered by soil crusts and clay.

Scaling Considerations Related to Interactions of Hydrologics, Pedologic and Geomorphic Processes

EPA Science Inventory

Hydrologic, pedologic, and geomorphic processes are strongly interrelated and affected by scale. These interactions exert important controls on runoff generation, preferential flow, contaminant transport, surface erosion, and mass wasting. Measurement of hydraulic conductivity (K...

Aeolian and fluvial processes in dryland regions: the need for integrated studies

USGS Publications Warehouse

Belnap, Jayne; Munson, Seth M.; Field, Jason P.

2011-01-01

Aeolian and fluvial processes play a fundamental role in dryland regions of the world and have important environmental and ecological consequences from local to global scales. Although both processes operate over similar spatial and temporal scales and are likely strongly coupled in many dryland systems, aeolian and fluvial processes have traditionally been studied separately, making it difficult to assess their relative importance in drylands, as well as their potential for synergistic interaction. Land degradation by accelerated wind and water erosion is a major problem throughout the world's drylands, and although recent studies suggest that these processes likely interact across broad spatial and temporal scales to amplify the transport of soil resources from and within drylands, many researchers and land managers continue to view them as separate and unrelated processes. Here, we illustrate how aeolian and fluvial sediment transport is coupled at multiple spatial and temporal scales and highlight the need for these interrelated processes to be studied from a more integrated perspective that crosses traditional disciplinary boundaries. Special attention is given to how the growing threat of climate change and land-use disturbance will influence linkages between aeolian and fluvial processes in the future. We also present emerging directions for interdisciplinary needs within the aeolian and fluvial research communities that call for better integration across a broad range of traditional disciplines such as ecology, biogeochemistry, agronomy, and soil conservation.

Geomorphic effects and sedimentological record of flash floods in the Copiapó River salt marsh (Atacama coast, Northern Chile)

NASA Astrophysics Data System (ADS)

Abad, Manuel; Fernández, Rolando; Izquierdo, Tatiana

2017-04-01

The Copiapó River is located South of the Atacama Desert (northern Chile) that is considered one of the most arid areas of the planet. On March 25 2015 this fluvial valley experienced one the largest hydrometeorological events recorded in historical times. The rain, unusually high, favored the run off in fluvial channels and alluvial fans that were dry for decades and triggered the rise and overflow of the Copiapó River at different points along the valley causing severe damages. In this work, we realize a characterization of the geomorphic configuration of the Copiapó River before and after this event with the aim of analyzing the main changes produced in the river mouth, where and extent coastal wetland of high ecological value is developed. The geomorphological mapping show a drastic change in the river mouth with the development of forms related with the river overflow and the flooding of the coastal plain such as levees, activation of abandoned channels, flooding lagoons, widening and deepening of the main channel, foredune rupture and, more importantly, a large mud sheet that covers almost the 80% of the study area, including the wetland and the main coastal dune systems. Just a small area of the wetland, far from the main channel, was not affected by this process as it was protected by the levees formed during the first stages of the overflow. The mud flow facies are homogeneous and consist of a layer of massive silty sands with a maximum thickness of 10-75 cm overlied by 5-20 cm of clay with wavy top and carbonaceous rest. It also presents a wide development of mud cracks and salt crusts. At the same time, 4 stages have been differentiated along the event: 1) arrival to the wetland of the first surge that flows in the channel and flooding of the southern sector of the wetland; 2) flooding of the complete mouth area because of the peak discharge arrival and generalize overflow with and associate muddy facies deposition; 3) erosional stage of the channel due to the formation of confined and turbulent flows in the channel; and 4) water logging of the wetland and adjacent areas that lasted several weeks. Using geostatistic technics, we have estimated a minimum volume of mud of 48,892 m3 (37,600 m3/km2) that accumulated during this event in the river mouth.

Palaeohydrological and palaeoecological studies on South Cameroonian alluvial sedimentary basins - New evidence on the palaeoenvironmental evolution of western Central Africa since the Late Pleistocene

NASA Astrophysics Data System (ADS)

Sangen, M.

2009-04-01

A new valuable and innovative contribution will be presented to ascertain the timing and extension of climatic and ecological changes in western equatorial Africa. Main focus is laid on the dynamics of climate, fluvial systems and the high sensitive tropical ecosystems (dense evergreen and semi-deciduous rain forest and savanna-rain forest margin) since the Late Pleistocene (~50 kyrs. BP). For this purpose extended fieldworks were carried out in South Cameroon (2004-2008) by the ReSaKo-Project (sub-project of DFG-Project 510) with abundant investigations on alluvial sedimentary basins of equatorial tropical fluvial systems. Suitable alluvial sediment-archives for palaeoenvironmental research were uncovered along selected braiding, meandering and anabranching/anastomosing reaches of major southwestern, into the Gulf of Guinea (Ntem, Nyong and Sanaga) and southeastern, into the Congo basin (Boumba, Dja and Ngoko) draining rivers (RUNGE et al. 2006, SANGEN 2008). Among geomorphological investigations and cross section discussions, 150 corings (Edelman, 20 cm layers) reaching maximum depths of 550 cm were carried out on river benches, levees, cut-off and periodical branches, islands and terraces as well as in seasonal inundated floodplains and backswamps. Corresponding sedimentary profiles and catenae recovered multilayered, sandy to clayey alluvia containing sedimentary form-units and palaeosurfaces which contribute to the reconstruction of palaeoenvironmental conditions in western equatorial Africa. Several (59) radiocarbon (AMS) dated samples (Erlangen and Lecce) from fossil organic layers and macro-rests embedded in these units yielded Late Pleistocene to recent ages (14C-ages around 48 to 0.2 kyrs. BP), spanning also the Last Glacial Maximum (LGM) and Holocene record. Abrupt grain-size modifications and alternating form-units (sandy and clayey layers, palaeosurfaces) in the stratigraphic records display fluctuations in the fluvial-morphological response of the fluvial systems to climatic variability and other extrinsic and intrinsic impacts. Although the sedimentary record varies among the studied river reaches, fossil organic sediment layers (palaeosurfaces) containing valuable proxy data were found in almost all alluvia basins of examined southern Cameroonian rivers. Around 56 ^13C-values corresponding to the dated samples (-31.4 to -18.0 ) evidence that despite major disturbances of the African rain forest over geological times (MALEY 2001) mainly rain forest ecosystems have prevailed during the corresponding time periods, presumably as gallery forests, which were able to persist in this fluvial habitat ("fluvial refuge"), even during arid periods (e.g. LGM). The results are consistent with earlier findings from lacustrine (SERVANT & SERVANT-VILDARY 2000), marine (WELDEAB et al. 2007) and additional sediment archives (GASSE et al. 2008) and will add additional insights and information to the unravelling of the complex respond of the African monsoon, the Central African ecosystems and fluvial systems to Late Quaternary climatic and environmental fluctuations within a globally teleconnected system. References: GASSE, F., CHALIé, F., VINCENS, A., WILLIAMS, M.A.J. & WILLIAMSON, D. (2008): Climatic patterns in equatorial and southern Africa from 30,000 to 10,000 years ago reconstructed from terrestrial and near-shore proxy data. Quaternary Science Reviews, 27 (25-26), 2316-2340. MALEY, J. (2001): The impact of arid phases on the African rain forest through geological history. In: WEBER, W., WHITE, L., VEDDER, A., NAUGHTON-TREVES, L. (Eds.): African rain forest ecology and conservation - An interdisciplinary perspective. Yale University Press, New Haven, 68-87. RUNGE, J., EISENBERG, J., SANGEN, M. (2006): Geomorphic evolution of the Ntem alluvial basin and physiogeographic evidence for Holocene environmental changes in the rain forest of SW Cameroon (Central Africa) - preliminary results. Z. Geomorph. N.F., Suppl. Bd. 145, 63-79. SERVANT, M. & SERVANT-VILDARY, S. (2000): Dynamique à long terme des écosystèmes forestiers intertropicaux. Publications issues du Symposium international « Dynamique à long terme des écosystèmes forestiers intertropicaux », Paris, 20-22 mars 1996. Paris, UNESCO, 1-434. WELDEAB, S., LEA, D.W., SCHNEIDER, R.R. & ANDERSEN, N. (2007): 155,000 years of West African monsoon ocean thermal evolution. Science, 316, 1303-1307.

Landform Evolution Modeling of Specific Fluvially Eroded Physiographic Units on Titan

NASA Technical Reports Server (NTRS)

Moore, J. M.; Howard, A. D.; Schenk, P. M.

2015-01-01

Several recent studies have proposed certain terrain types (i.e., physiographic units) on Titan thought to be formed by fluvial processes acting on local uplands of bedrock or in some cases sediment. We have earlier used our landform evolution models to make general comparisons between Titan and other ice world landscapes (principally those of the Galilean satellites) that we have modeled the action of fluvial processes. Here we give examples of specific landscapes that, subsequent to modeled fluvial work acting on the surfaces, produce landscapes which resemble mapped terrain types on Titan.

Aircraft and satellite remote sensing of desert soils and landscapes

NASA Technical Reports Server (NTRS)

Petersen, G. W.; Connors, K. F.; Miller, D. A.; Day, R. L.; Gardner, T. W.

1987-01-01

Remote sensing data on desert soils and landscapes, obtained by the Landsat TM, Heat Capacity Mapping Mission (HCMM), Simulated SPOT, and Thermal IR Multispectral Scanner (TIMS) aboard an aircraft, are discussed together with the analytical techniques used in the studies. The TM data for southwestern Nevada were used to discriminate among the alluvial fan deposits with different degrees of desert pavement and varnish, and different vegetation cover. Thermal-IR data acquired from the HCMM satellite were used to map the spatial distribution of diurnal surface temperatures and to estimate mean annual soil temperatures in central Utah. Simulated SPOT data for northwestern New Mexico identified geomorphic features, such as differences in eolian sand cover and fluvial incision, while the TIMS data depicted surface geologic features of the Saline Valley in California.

Sediment Budget Analysis and Hazard Assessment in the Peynin, a Small Alpine Catchment (Upper Guil River, Southern Alps, France)

NASA Astrophysics Data System (ADS)

Carlier, Benoit; Arnaud-Fassetta, Gilles; Fort, Monique; Bouccara, Fanny; Sourdot, Grégoire; Tassel, Adrien; Lissak, Candide; Betard, François; Cossart, Etienne; Madelin, Malika; Viel, Vincent; Charnay, Bérengère; Bletterie, Xavier

2014-05-01

The upper Guil catchment (Southern Alps) is prone to hydro-geomorphic hazards. Major hazards are related to catastrophic floods, with an amplification of their impacts due to strong hillslope-channel connectivity as observed in 1957 and 2000. In both cases, the rainfall intensity, aggravated by the pre-existing saturated soils, explained the instantaneous response of the fluvial system, such as destabilisation of slopes, high sediment discharge, and subsequent damages to exposed structures and settlements present in the floodplain and at confluence sites. The Peynin junction with the Guil River is one of these sites, where significant land-use change during the last decades in relation to the development of handicraft and tourism economy has increased debris flow threat to population. Here, we adopt a sediment budget analysis aimed at better understanding the functioning of this small subcatchment. This latter offers a combination of factors that favour torrential and gravitational activity. It receives abundant and intense rainfall during "Lombarde" events (moist air mass from Mediterranean Sea). Its elongated shape and small surface area (15 km²) together with asymmetric slopes (counter dip slope on the left bank) accelerate runoff on a short response time. In addition highly tectonised shaly schists supply a large volume of debris (mostly platy clasts and fine, micaceous sediment). The objectives of this study, carried out in the frame of SAMCO (ANR) project, are threefold: Identify the different sediment storages; Characterise the processes that put sediment into motion; Quantify volumes of sediment storages. We produced a geomorphic map using topographic surveys and aerial photos in order to locate the different sediment storage types and associated processes. This analysis was made with respect to geomorphic coupling and sediment flux activity. In terms of surface area, the dominant landforms in the valley were found to be mass wasting, talus slopes and alluvial fans and plains. Most of these forms are relict landforms, decoupled from the present geomorphic system. Notable sediment transport is limited to avalanche tracks, debris flows, and along floodplains. Sediment volumes were calculated using a combination of polynomial functions of cross sections and GIS modelling. We calculated the overall sediment volume of the valley fill deposits to be 1.05 km3. This corresponds to a mean sediment thickness of 90.2 m. Landslides appear as the major sediment storage, representing more than 35% of the sediment volume stored in the Peynin subcatchment. For some locations, the polynomial-generated cross sections resulted in overestimations of sediment thickness, therefore, these results have to be considered as an order of magnitude. Future investigations will include seismic refraction profiles that may provide bedrock depth, hence a better control on sediment thickness (estimates generated thanks to GIS). Eventually, we expect our results to be used to better model, hence prevent future debris-flow events at the confluence of Peynin stream with the Guil River.

Connectivity of earthquake-triggered landslides with the fluvial network: Implications for landslide sediment transport after the 2008 Wenchuan earthquake

NASA Astrophysics Data System (ADS)

Li, Gen; West, A. Joshua; Densmore, Alexander L.; Hammond, Douglas E.; Jin, Zhangdong; Zhang, Fei; Wang, Jin; Hilton, Robert G.

2016-04-01

Evaluating the influence of earthquakes on erosion, landscape evolution, and sediment-related hazards requires understanding fluvial transport of material liberated in earthquake-triggered landslides. The location of landslides relative to river channels is expected to play an important role in postearthquake sediment dynamics. In this study, we assess the position of landslides triggered by the Mw 7.9 Wenchuan earthquake, aiming to understand the relationship between landslides and the fluvial network of the steep Longmen Shan mountain range. Combining a landslide inventory map and geomorphic analysis, we quantify landslide-channel connectivity in terms of the number of landslides, landslide area, and landslide volume estimated from scaling relationships. We observe a strong spatial variability in landslide-channel connectivity, with volumetric connectivity (ξ) ranging from ~20% to ~90% for different catchments. This variability is linked to topographic effects that set local channel densities, seismic effects (including seismogenic faulting) that regulate landslide size, and substrate effects that may influence both channelization and landslide size. Altogether, we estimate that the volume of landslides connected to channels comprises 43 + 9/-7% of the total coseismic landslide volume. Following the Wenchuan earthquake, fine-grained (<~0.25 mm) suspended sediment yield across the Longmen Shan catchments is positively correlated to catchment-wide landslide density, but this correlation is statistically indistinguishable whether or not connectivity is considered. The weaker-than-expected influence of connectivity on suspended sediment yield may be related to mobilization of fine-grained landslide material that resides in hillslope domains, i.e., not directly connected to river channels. In contrast, transport of the coarser fraction (which makes up >90% of the total landslide volume) may be more significantly affected by landslide locations.

Controls on sinuosity in the sparsely vegetated Fossálar River, southern Iceland

NASA Astrophysics Data System (ADS)

Ielpi, Alessandro

2017-06-01

Vegetation exerts strong controls on fluvial sinuosity, providing bank stability and buffering surface runoff. These controls are manifest in densely vegetated landscapes, whereas sparsely vegetated fluvial systems have been so far overlooked. This study integrates remote sensing and gauging records of the meandering to wandering Fossálar River, a relatively steep-sloped (< 2.5%) Icelandic river featuring well-developed point bars (79%-85% of total active bar surface) despite the lack of thick, arborescent vegetation. Over four decades, fluctuations in the sinuosity index (1.15-1.43) and vegetation cover (63%-83%) are not significantly correlated (r = 0.28, p > 0.05), suggesting that relationships between the two are mediated by intervening variables and uncertain lag times. By comparison, discharge regime and fluvial planform show direct correlation over monthly to yearly time scales, with stable discharge stages accompanying the accretion of meander bends and peak floods related to destructive point-bar reworking. Rapid planform change is aided by the unconsolidated nature of unrooted alluvial banks, with recorded rates of lateral channel-belt migration averaging 18 m/yr. Valley confinement and channel mobility also control the geometry and evolution of individual point bars, with the highest degree of spatial geomorphic variability recorded in low-gradient stretches where lateral migration is unimpeded. Point bars in the Fossálar River display morphometric values comparable to those of other sparsely vegetated rivers, suggesting shared scalar properties. This conjecture prompts the need for more sophisticated integrations between remote sensing and gauging records on modern rivers lacking widespread plant life. While a large volume of experimental and field-based work maintains that thick vegetation has a critical role in limiting braiding, thus favouring sinuosity, this study demonstrates the stronger controls of discharge regime and alluvial morphology on sparsely vegetated sinuous rivers.

Analysis of Fluvial Bed Sediments Along the Apalachicola River, Florida through Field Reconnaissance Studies

NASA Astrophysics Data System (ADS)

Passeri, D.; Hagen, S. C.; Daranpob, A.; Smar, D. E.

2011-12-01

River competence is an important parameter in understanding sediment transport in fluvial systems. Competence is defined as the measure of a stream's ability to transport a certain maximum grain size of sediment. Studies have shown that bed sediment particle size in rivers and streams tends to vary spatially along the direction of stream flow. Over a river section several reaches long, variability of sediment particle sizes can be seen, often becoming finer downstream. This phenomenon is attributed to mechanisms such as local control of stream gradient, coarse tributary sediment supply or particle breakdown. Average particle size may also be smaller in tributary sections of rivers due to river morphology. The relationship between river mean velocity and particle size that can be transported has also been explored. The Hjulstrom curve classifies this relationship by relating particle size to velocity, dividing the regions of sedimentation, transportation, and erosion. The curve can also be used to find values such as the critical erosion velocity (the velocity required to transport particles of various sizes in suspension) and settling velocity (the velocity at which particles of a given size become too heavy to be transported and fall out of suspension, consequently causing deposition). The purpose of this research is to explore the principles of river competence through field reconnaissance collection and laboratory analysis of fluvial sediment core samples along the Apalachicola River, FL and its distributaries. Sediment core samples were collected in the wetlands and estuarine regions of the Apalachicola River. Sieve and hydrometer analyses were performed to determine the spatial distribution of particle sizes along the river. An existing high resolution hydrodynamic model of the study domain was used to simulate tides and generate river velocities. The Hjulstrom curve and the generated river velocities were used to define whether sediment was being transported, eroded or deposited at the different locations in the river and its distributaries. Parameters such as critical erosion velocity and settling velocity were also calculated to describe sediment transport along the channel. This research provides a better understanding of the fluvial geomorphic system, particularly sediment transport in channels. It also provides excellent validation data for future sediment transport studies in similar fluvial study domains.

Redistribution of radioactive mine wastes by slushflows and other processes in small mountain river basin in Russian Subarctics

NASA Astrophysics Data System (ADS)

Garankina, Ekaterina; Belyaev, Vladimir; Ivanov, Maxim; Romanenko, Fedor; Gurinov, Artem; Tulyakov, Egor; Kuzmenkova, Natalia

2017-04-01

The Khibiny Mountains located in central part of the Kola Peninsula (Northern European Russia) are characterized by harsh climatic conditions and frequent occurrence of hazardous or even catastrophic processes. Most widespread of those are snow avalanches taking place every year and slushflows with average recurrence interval of about 10 years. The latter represent specific type of hyperconcentrated gravitational flow of oversaturated mixture of snow and water (20 to 70%) with relatively low sediment concentration (up to 10-15%). Most often slushflows form during spring snowmelt in small mountainous basins (in most cases up to 3-6 km2) with thick snowpacks or snow dams caused by avalanches in stream channels. Typically observed volumes vary in a range of 20000-40000 m3, while rare catastrophic events can reach 200000-500000 m3. Kinetic energy of frontal wave that can be up to several meters high and concentrates most of the largest debris is most likely lower than that of typical debris flow of similar size, mainly because of much lower slushflow density (900-1200 kg m-3). Nevertheless, rare occasional measurements of front wave velocity gave dramatic values of 20-25 m s-1 maximum. Such characteristics combined with unpredictable rapid formation make slushflows definitely hazardous processes that can cause serious damage to industrial and residential infrastructure as well as injuries or causalities to people. For example, the Khibiny Mountains have at least 200 locations where formation of slushflows was detected at least ones over the last 50 years. Widespread constructions and communications associated with intensive exploration of mineral resources as well as growing interest to the area as touristic attraction for skiing and other wintertime activities make the Khibiny Mountains an area of serious geomorphic hazards associated with slushflows. In this particular study, we considered the Hackman basin where heavy debris flows occur at least ones per several decades. One of the unique features of that basin is that there was radioactive ore mine active in late 1930s on one of the steep valley sides. The mine was active only for several years as the production of radioactive minerals appeared to be much lower than expected. However, mine wastes are still remaining there as scree slopes on right valley side in its middle reach under several mine entrances. Colluvial material on these screes is highly enriched by several natural radionuclides including members of the 232Th decay chain. We have made an attempt to use this feature for fingerprinting sediment redistribution along the valley by slushflows and fluvial processes. Results of gamma-spectrometric analysis of finer sediment fractions from different geomorphic settings within the Hackman basin have shown that there is a systematic non-uniform spatial distribution of 232Th decay chain natural radionuclides closely related to its geological background and geomorphological structure. It proves that natural lithogenic radionuclide content in clastic sediments can be used for fingerprinting of slushflows debris sources and sinks and, possibly for distinguishing between in situ slushflow deposits and those partly reworked by later fluvial activities.

Microbial Biomass and Activity in Geomorphic Features in Forested and Urban Restored and Degraded Streams

EPA Science Inventory

Geomorphic spatial heterogeneity affects sediment denitrification, an anaerobic microbial process that results in the loss of nitrogen (N), and other anaerobic microbial processes such as methanogenesis in urban streams. We measured sediment denitrification potential (DEA), metha...

A Geomorphic Analysis of Floodplain Lakes along the Embanked Lower Mississippi River for Managing Hydrologic Connectivity

NASA Astrophysics Data System (ADS)

Hudson, Paul; Boot, Dax; Sounny-Slitinne, M. Anwar; Kristensen, Kristiaan

2015-04-01

A Geomorphic Analysis of Floodplain Lakes along the Embanked Lower Mississippi River for Managing Hydrologic Connectivity Floodplain lakes are vital to the environmental integrity of lowland rivers. Embankment by levees (dikes) for flood control greatly reduces the size of lowland floodplains and is detrimental to the quality and functioning of floodplain water bodies, presenting a challenge to government agencies charged with environmental management. The embanked floodplain of the Lower Mississippi River is an enormous surface which includes a variety of lake types formed by geomorphic and anthropogenic processes. While much is known about the channel and hydrologic regime, very little is known about the physical structure and functioning of the embanked floodplain of the lower Mississippi. Importantly, management agencies do not have an inventory of the basic characteristics (e.g., type, frequency, location, size, shape) of water bodies within the lower Mississippi embanked floodplain. An analysis of lakes along the Lower Mississippi River embanked floodplain is performed by utilizing the National Hydrographic Dataset (NHD) from the U.S. Geological Survey, a LiDAR digital elevation model (DEM), as well as streamflow data from the USGS. The vector NHD data includes every official mapped water body (blue line polygons) on USGS topographic maps at scales of 1:100,000 and 1:24,000. Collectively, we identify thousands of discreet water bodies within the embanked floodplain. Utilizing planimetric properties the water bodies were classified into the following lake types: cutoffs (neck and chute), sloughs, crevasse (scour), local drainage (topographic), and borrow pits. The data is then statistically analyzed to examine significant differences in the spatial variability in lake types along the entire lower Mississippi embanked floodplain in association with geomorphic divisions and hydrologic regime. The total embanked floodplain area of the LMR is 7,303 km2,. The total area of floodplain lakes within the embanked floodplain is 382 km2, or 5.2% of the embanked floodplain surface area. Considerable variability in embanked floodplain area along the lower Mississippi, however, results in spatial variability in the frequency of specific lake types. Meander cutoff lakes represent the largest proportion of lake area, at 49%, with approximately half of this area comprised of artificial cutoff lakes. The next largest class of lakes are borrow pit lakes (at 16%), which are anthropogenic water bodies created for the process of levee (dike) construction and maintenance, but which represent valuable environmental habitat. Meander cutoff lakes are especially dominant in the upper reaches of the Lower Mississippi and diminish moving downstream, where the area of embanked floodplain also decreases. Interestingly, anthropogenic lakes (borrow pits) become increasingly prevalent further downstream and dominate over natural formed lakes. The location of lake types along the Lower Mississippi does not correspond with recent historic geomorphic and hydrologic activity. The highest frequency of meander cutoff and crevasse lakes are not located within floodplain sections which historically had the highest rates of lateral migration (m/yr) and flooding (duration). Although overbank hydrologic connectivity varies along the river, it does not vary necessarily where it would be most advantageous to the connectivity of specific types of lakes. The research results provide government agencies with a spatial inventory and methodological approach to improve the management of floodplain water bodies for sustaining valuable aquatic habitat, whether by artificially restricting or enhancing hydrologic connectivity. Key words: floodplain lakes, fluvial geomorphology, hydrologic connectivity, anthropogenic impacts, Lower Mississippi River

Effect of Sediment Availability in Bedload-Dominated Rivers on Fluvial Geomorphic Equilibrium

NASA Astrophysics Data System (ADS)

Marti, M.

2016-12-01

Channels are known to compensate for changes in sediment supply via covariate changes in channel properties, yet the timescale for adjustment remains poorly constrained. We propose that reductions in sediment flux inhibit equilibrium re-establishment and thus impact the timescale of system adjustment. Using run-of-river dams as natural experiments, this study quantifies the geomorphic response of channels to sediment supply reduction. Channel traits that facilitate increased sediment trapping behind the dam, such as large reservoir storage capacity relative to annual inflow and low slope, were expected to inhibit a channel's ability to re-establish equilibrium following impoundment, lengthening the equilibrium establishment timescale to tens or hundreds of years. Reaches associated with increased trapping were therefore anticipated to exhibit non-equilibrium forms. Channel equilibrium was evaluated downstream of 8 ROR dams in New England with varying degrees of sediment trapping. Sites cover a range of watershed sizes (3-155 km2), channel slopes (.05-5%), 2-year discharges (1.5-60 m3/s) and storage capacity volumes. Because equilibrium channel form is just sufficient to mobilize grains under bankfull conditions in bedload-dominated rivers, the Shields parameter was used to assess equilibrium form. Unregulated, upstream Shields values and regulated, downstream values were calculated at 14 total cross-sections extending 300-450 m upstream and downstream of each dam. Sediment trapping was estimated using Brune's curve (1953). On the Charles Brown Brook (VT), a marginally significant (p=0.08) increase in Shields values from a mean of 0.14 upstream to 0.41 downstream of a 100+ year old dam was observed. In contrast, reaches downstream of the 100+ year old Pelham dam (MA) exhibit significantly lower Shields values. This suggests that trapping behind the dam inhibits the downstream channel from reaching an equilibrium state, but not always in the same way. Better understanding of geomorphic response to reduced sediment flux as a control on equilibrium establishment will broaden the knowledge of geomorphic equilibrium and aid in management of regulated, bedload-dominated rivers.

Development of Envelope Curves for Predicting Void Dimensions from Overturned Trees

DTIC Science & Technology

2014-07-01

transport due to tree root throw: integrating tree population dynamics, wildfire, and geomorphic response (Gallaway et al. 2009...Johnson. 2009. Sediment transport due to tree root throw: Integrating tree population dynamics, wildfire and geomorphic response. Earth Surface Processes...environment, but not vegetation (Peterson and Leach 2008) ............................................................ 17 4.7 Pedologic and geomorphic impacts

EFFECTS OF GEOMORPHIC PROCESSES AND HYDROLOGIC REGIMES ON RIPARIAN VEGETATION

EPA Science Inventory

In this chapter, the relationships among riparian vegetation and geomorphic and hydrologic processes in central Great Basin watersheds are evaluated over a range of scales. These relationships are examined through a series of case studies that have been conducted by the Great Ba...

Comprehensive Seismological Monitoring of Geomorphic Processes in Taiwan

NASA Astrophysics Data System (ADS)

Chao, W. A.; Chen, C. H.

2016-12-01

Geomorphic processes such as hillslope mass wasting and river sediment transport are important for studying landscape dynamics. Mass movements induced from geomorphic events can generate seismic waves and be recorded by seismometers. Recent studies demonstrate that seismic monitoring techniques not only fully map the spatiotemporal patterns of geomorphic activity but also allow for exploration of the dynamic links between hillslope failures and channel processes, which may not be resolved by conventional techniques (e.g., optical remote sensing). We have recently developed a real-time landquake monitoring system (RLMS, here we use the term `landquake' to represent all hillslope failures such as rockfall, rock avalanche and landslide), which has been continuously monitoring landquake activities in Taiwan since June 2015 based on broadband seismic records, yielding source information (e.g., location, occurrence time, magnitude and mechanism) for large-sized events (http://140.112.57.117/main.html). Several seismic arrays have also been deployed over the past few years around the catchments and along the river channels in Taiwan for monitoring erosion processes at catchment scale, improving the spatiotemporal resolution in exploring the interaction between geomorphic events and specific meteorological conditions. Based on a forward model accounting for the impulsive impacts of saltating particles, we can further invert for the sediment load flux, a critical parameter in landscape evolution studies, by fitting the seismic observations only. To test the validity of the seismologically determined sediment load flux, we conduct a series of controlled dam breaking experiments that are advantageous in well constraining the spatiotemporal variations of the sediment transport. Incorporating the seismological constrains on geomorphic processes with the effects of tectonic and/or climate perturbations can provide valuable and quantitative information for more fully understanding and modeling of the dynamics of erosional mountain landscapes. Comprehensive seismic monitoring also yields important information for the evaluation, assessment and emergency response of hazardous geomorphic events.

Constructing a sequence of palaeoDEMs to obtain erosion rates in a drainage basin.N

NASA Astrophysics Data System (ADS)

Castelltort, F. Xavier; Carles Balasch, J.; Cirés, Jordi; Colombo, Ferran

2017-04-01

DEMs made in a present-day drainage basin, considering it as a geomorphic unit, represent the end result of a landscape evolution. This process has had to follow a model of erosion. Trying to establish a conceptual erosion model in landscape evolution represents the first difficulty in constructing a sequence of palaeoDEMs. But if one is able to do it, the result will be easier and believable. The next step to do is to make a catalogue of base level types present in the drainage basin. The list has to include elements with determinate position and elevation (x, y, z) from the centre of the basin until hillslopes. A list of base level types may contain fluvial terrace remnants, erosive surfaces, palaeosols, alluvial covers of glacis, alluvial fans, rockfalls, landslides and scree zones. It is very important to know the spatial and temporal relations between the elements of the list, even if they are disconnected by erosion processes. Relative chronologies have to be set for all elements of the catalogue, and as far as possible absolute chronologies. To do it,it is essential to have established first the spatial relations between them, including those elements that are gone. Moreover, it is also essential to have adapted all the elements to the conceptual erosion model proposed. In this step, it has to be kept in mind that erosion rates can be very different in determinate areas within the same geomorphic unit. Erosion processes are focused in specific zones while other areas are maintained in stability. A good technique to construct a palaeoDEM is to start making, by hand, a map of contour lines. At this point, it is valuable to use the elements' catalogue. The use of those elements belonging to the same palaeosurface will result in a map. Several maps can be obtained from a catalogue. Contour maps can be gridded into a 3D surface by means of a specific application and a set of surfaces will be obtained. Algebraic operations can be done with palaeoDEMs obtaining positive or negative volumes corresponding to processes of erosion or aggradation. A case study of the application of palaeoDEMs is presented in the process of homoclinal shifting that is the origin of the strike valley of La Plana de Vic in the NE of Iberian Peninsula.

3D morphometry of valley networks on Mars from HRSC/MEX DEMs: Implications for climatic evolution through time

NASA Astrophysics Data System (ADS)

Ansan, V.; Mangold, N.

2013-09-01

valley networks have been identified mainly in the Noachian heavily cratered uplands. Eight dense branching valley networks were studied in Noachian terrains of Huygens, Newcomb and Kepler craters, south Tyrrhena Terra, and Thaumasia, in Hesperian terrains of Echus Plateau and west Eberswalde craters, and in Amazonian terrains of Alba Patera, using images and digital elevation models from the Mars Express High Resolution Stereo Camera to determine 2D and 3D morphometric parameters. Extracted geomorphic parameters show similar geometry to terrestrial valleys: drainage densities, organization from bifurcation ratios and lengths ratios, Hack exponent consistent with terrestrial values of ~0.6, and progressive deepening of valleys with increasing Strahler order. In addition, statistics on valley depths indicate a deeper incision of Noachian valleys compared to younger post-Noachian valleys (<25 m for Amazonian ones compared to >100 m for Noachian ones), showing a strong difference in fluvial erosion. These characteristics show that dense Martian valley networks formed by overland flows in relation to a global atmospheric water cycle in Noachian epoch and confirm that the later stages of activity may be related to shorter duration of activity, distinct climatic conditions, and/or regional processes, or conditions.

A multiscale investigation of habitat use and within-river distribution of sympatric sand darter species

USGS Publications Warehouse

Thompson, Patricia A.; Welsh, Stuart A.; Strager, Michael P.; Rizzo, Austin A.

2018-01-01

The western sand darter Ammocrypta clara, and eastern sand darter Ammocrypta pellucida, are sand-dwelling fishes of conservation concern. Past research has emphasized the importance of studying individual populations of conservation concern, while recent research has revealed the importance of incorporating landscape scale processes that structure habitat mosaics and local populations. We examined habitat use and distributions of western and eastern sand darters in the lower Elk River of West Virginia. At the sandbar habitat use scale, western sand darters were detected in sandbars with greater area, higher proportions of coarse grain sand and faster bottom current velocity, while the eastern sand darter used a wider range of sandbar habitats. The landscape scale analysis revealed that contributing drainage area was an important predictor for both species, while sinuosity, which presumably represents valley type, also contributed to the western sand darter’s habitat suitability. Sandbar quality (area, grain size, and velocity) and fluvial geomorphic variables (drainage area and valley type) are likely key driving factors structuring sand darter distributions in the Elk River. This multiscale study of within-river species distribution and habitat use is unique, given that only a few sympatric populations are known of western and eastern sand darters.

Geology of Holden Crater and the Holden and Ladon Multi-Ring Impact Basins, Margaritifer Terra, Mars

NASA Technical Reports Server (NTRS)

Irwin, R. P., III; Grant, J. A.

2008-01-01

Geologic mapping at 1:500K scale of Mars quads 15s027, 20s027, 25s027, and 25s032 (Fig. 1) is in progress to constrain the geologic and geomorphic history of southwestern Margaritifer Terra. This work builds on earlier maps at 1:5M [1] and 1:15M scales [2], recent to concurrent 1:500Kscale mapping of adjacent areas to the east [3-5], and studies of drainage basin evolution along the Uzboi-Ladon-M (ULM; the third valley in the sequence has no formal name) Valles basin overflow system and nearby watersheds [6-9]. Two of the six landing sites under consideration for the Mars Science Laboratory rover are in this map area, targeting finely layered, phyllosilicate-rich strata and alluvial fans in Holden crater [10-12] (26degS, 34degW, 150 km diameter) or deposits southeast of a likely delta in Eberswalde crater [13-16] (24degS, 33degW, 50 km in diameter). Diverse processes including larger and smaller impacts, a wide range in fluvial activity, and local to regional structural influences have all affected the surface morphology.

Dramatic undercutting of piedmont rivers after the 2008 Wenchuan Ms 8.0 Earthquake

PubMed Central

Fan, Niannian; Nie, Ruihua; Wang, Qiang; Liu, Xingnian

2016-01-01

Changes in river channel erosion or deposition affect the geomorphic evolution, aquatic ecosystems, and river regulation strategies. Fluvial processes are determined by the flow, sediment and boundary conditions, and it has long been expected that increasing sediment supply will induce aggradation. Here, based on thorough field surveys, we show the unexpected undercutting of the piedmont rivers influenced by the 2008 Wenchuan (Ms 8.0) Earthquake. The rivers flow from the Longmen Mountain with significant topographic relief to the flat Chengdu plain. In the upstreams, sediment supply increased because of the landslides triggered by the earthquake, causing deposition in the upstream mountain reaches. However, the downstream plain reaches suffered undercutting instead of deposition, and among those rivers, Shiting River was the most seriously affected, with the largest undercutting depth exceeding 20 m. The reasons for this unexpected undercutting are proposed herein and relate to both natural and anthropogenic causes. In addition, we also demonstrate, at least for certain conditions, such as rivers flowing from large-gradient mountain regions to low-gradient plain regions, that upstream sediment pulses may induce aggradation in upstream and degradation in downstream, causing the longitudinal profile to steepen to accommodate the increasing sediment flux. PMID:27857220

Debris flow hazards mitigation--Mechanics, prediction, and assessment

USGS Publications Warehouse

Chen, C.-L.; Major, J.J.

2007-01-01

These proceedings contain papers presented at the Fourth International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction, and Assessment held in Chengdu, China, September 10-13, 2007. The papers cover a wide range of topics on debris-flow science and engineering, including the factors triggering debris flows, geomorphic effects, mechanics of debris flows (e.g., rheology, fluvial mechanisms, erosion and deposition processes), numerical modeling, various debris-flow experiments, landslide-induced debris flows, assessment of debris-flow hazards and risk, field observations and measurements, monitoring and alert systems, structural and non-structural countermeasures against debris-flow hazards and case studies. The papers reflect the latest devel-opments and advances in debris-flow research. Several studies discuss the development and appli-cation of Geographic Information System (GIS) and Remote Sensing (RS) technologies in debris-flow hazard/risk assessment. Timely topics presented in a few papers also include the development of new or innovative techniques for debris-flow monitoring and alert systems, especially an infra-sound acoustic sensor for detecting debris flows. Many case studies illustrate a wide variety of debris-flow hazards and related phenomena as well as their hazardous effects on human activities and settlements.

Autogenic geomorphic processes determine the resolution and fidelity of terrestrial paleoclimate records.

PubMed

Foreman, Brady Z; Straub, Kyle M

2017-09-01

Terrestrial paleoclimate records rely on proxies hosted in alluvial strata whose beds are deposited by unsteady and nonlinear geomorphic processes. It is broadly assumed that this renders the resultant time series of terrestrial paleoclimatic variability noisy and incomplete. We evaluate this assumption using a model of oscillating climate and the precise topographic evolution of an experimental alluvial system. We find that geomorphic stochasticity can create aliasing in the time series and spurious climate signals, but these issues are eliminated when the period of climate oscillation is longer than a key time scale of internal dynamics in the geomorphic system. This emergent autogenic geomorphic behavior imparts regularity to deposition and represents a natural discretization interval of the continuous climate signal. We propose that this time scale in nature could be in excess of 10 4 years but would still allow assessments of the rates of climate change at resolutions finer than the existing age model techniques in isolation.

Autogenic geomorphic processes determine the resolution and fidelity of terrestrial paleoclimate records

PubMed Central

Foreman, Brady Z.; Straub, Kyle M.

2017-01-01

Terrestrial paleoclimate records rely on proxies hosted in alluvial strata whose beds are deposited by unsteady and nonlinear geomorphic processes. It is broadly assumed that this renders the resultant time series of terrestrial paleoclimatic variability noisy and incomplete. We evaluate this assumption using a model of oscillating climate and the precise topographic evolution of an experimental alluvial system. We find that geomorphic stochasticity can create aliasing in the time series and spurious climate signals, but these issues are eliminated when the period of climate oscillation is longer than a key time scale of internal dynamics in the geomorphic system. This emergent autogenic geomorphic behavior imparts regularity to deposition and represents a natural discretization interval of the continuous climate signal. We propose that this time scale in nature could be in excess of 104 years but would still allow assessments of the rates of climate change at resolutions finer than the existing age model techniques in isolation. PMID:28924607

Recent (1999-2003) Canadian research on contemporary processes of river erosion and sedimentation, and river mechanics

NASA Astrophysics Data System (ADS)

de Boer, D. H.; Hassan, M. A.; MacVicar, B.; Stone, M.

2005-01-01

Contributions by Canadian fluvial geomorphologists between 1999 and 2003 are discussed under four major themes: sediment yield and sediment dynamics of large rivers; cohesive sediment transport; turbulent flow structure and sediment transport; and bed material transport and channel morphology. The paper concludes with a section on recent technical advances. During the review period, substantial progress has been made in investigating the details of fluvial processes at relatively small scales. Examples of this emphasis are the studies of flow structure, turbulence characteristics and bedload transport, which continue to form central themes in fluvial research in Canada. Translating the knowledge of small-scale, process-related research to an understanding of the behaviour of large-scale fluvial systems, however, continues to be a formidable challenge. Models play a prominent role in elucidating the link between small-scale processes and large-scale fluvial geomorphology, and, as a result, a number of papers describing models and modelling results have been published during the review period. In addition, a number of investigators are now approaching the problem by directly investigating changes in the system of interest at larger scales, e.g. a channel reach over tens of years, and attempting to infer what processes may have led to the result. It is to be expected that these complementary approaches will contribute to an increased understanding of fluvial systems at a variety of spatial and temporal scales. Copyright

TerraceM: A Matlab® tool to analyze marine terraces from high-resolution topography

NASA Astrophysics Data System (ADS)

Jara-Muñoz, Julius; Melnick, Daniel; Strecker, Manfred

2015-04-01

To date, Light detection and ranging (LiDAR), high- resolution topographic data sets enable remote identification of submeter-scale geomorphic features bringing valuable information of the landscape and geomorphic markers of tectonic deformation such as fault-scarp offsets, fluvial and marine terraces. Recent studies of marine terraces using LiDAR data have demonstrated that these landforms can be readily isolated from other landforms in the landscape, using slope and roughness parameters that allow for unambiguously mapping regional extents of terrace sequences. Marine terrace elevation has been used since decades as geodetic benchmarks of Quaternary deformation. Uplift rates may be estimated by locating the shoreline angle, a geomorphic feature correlated with the high-stand position of past sea levels. Indeed, precise identification of the shoreline-angle position is an important requirement to obtain reliable tectonic rates and coherent spatial correlation. To improve our ability to rapidly assess and map different shoreline angles at a regional scale we have developed the TerraceM application. TerraceM is a Matlab® tool that allows estimating the shoreline angle and its associated error using high-resolution topography. For convenience, TerraceM includes a graphical user interface (GUI) linked with Google Maps® API. The analysis starts by defining swath profiles from a shapefile created on a GIS platform orientated orthogonally to the terrace riser. TerraceM functions are included to extract and analyze the swath profiles. Two types of coastal landscapes may be analyzed using different methodologies: staircase sequences of multiple terraces and rough, rocky coasts. The former are measured by outlining the paleo-cliffs and paleo-platforms, whereas the latter are assessed by picking the elevation of sea-stack tops. By calculating the intersection between first-order interpolations of the maximum topography of swath profiles we define the shoreline angle in staircase terraces. For rocky coasts, the maximum stack peaks for a defined search ratio as well as a defined inflection point on the adjacent main cliff are interpolated to calculate the shoreline angle at the intersection with the cliff. Error estimates are based on the standard deviation of the linear regressions. The geomorphic age of terraces (Kt) can be also calculated by the linear diffusion equation (Hanks et al., 1989), with a best-fitting model found by minimizing the RMS. TerraceM has the ability to efficiently process several profiles in batch-mode run. Results may be exported in various formats, including Google Earth and ArcGis, basic statistics are automatically computed. Test runs have been made at Santa Cruz, California, using various topographic data sets and comparing results with published field measurements (Anderson and Menking, 1994). Repeatability was evaluated using multiple test runs made by students in a classroom setting.

Quantification of fluvial response to tectonic deformation in the Central Pontides, Turkey; inferences from OSL dating of fluvial terraces

NASA Astrophysics Data System (ADS)

McClain, Kevin; Yıldırım, Cengiz; Çiner, Attila; Akif Sarıkaya, M.; Şahin, Sefa; Özcan, Orkan; Güneç Kıyak, Nafiye; Öztürk, Tuǧba

2017-04-01

From Late Miocene to present, Anatolia's rapid counterclockwise movement, which increases in velocity towards the Hellenic Arc, has formed the North Anatolian Fault (NAF), a dextral transform fault along the Anatolia-Eurasia plate boundary and the northern margin of the Central Anatolian Plateau (CAP). A zone of transpression referred to as the Central Pontides exists between the broad restraining bend of the NAF and the Black Sea Basin, uplifting what is interpreted as a detached flower structure. Dating of Quaternary landforms in the eastern flank of the Central Pontides has helped to understand its recent deformation. However, in the western flank of the Central Pontides there is an absence of Quaternary studies, relatively quiet modern seismicity, and difficulties locating or observing fault scarps. This led us to use optically stimulated luminescence dating (OSL-dating) of fluvial terrace sediments and the study of geomorphic features to gain insight into the influence of climate and tectonics on landscape evolution of this area. In this area, the Filyos River crosses the Karabük Fault (reverse fault) and deeply incises a gorge through the Karabük Range before flowing towards the Black Sea. In the gorge an abundance of indicators of tectonic deformation were mapped, such as hanging valleys, wind gaps, bedrock gorges, landslides, steep V-shaped channels, tilted basins, as well as fluvial strath terraces. In particular, strath terraces of at least 8 levels within just 1.5 km of horizontal distance were examined. We used OSL-dating to estimate five deposition ages of fluvial strath terrace sediments, leading to an estimation of incision and uplift rates over time. Using three samples per terrace with strath elevations of 246 ± 0.2 m, 105.49 ± 0.2 m, 43.6 ± 0.2 m, 15.3 ± 0.2 m and 3.6 ± 0.2 m above the Filyos River, we determined corresponding ages of 841 ± 76 ka, 681 ± 49 ka, 386 ± 18 ka, 88 ± 5.1 ka and 50.9 ± 2.8 ka. Incision rates over time (oldest terrace to youngest) suggest uplift of 0.29 ± 0.03 mm/y, 0.16 ± 0.01 mm/y, 0.10 ± 0.01 mm/y, 0.17 ± 0.01 mm/y and 0.07 ± 0.004 mm/y. Collectively, our ages infer decelerating fluvial incision and rock uplift rates in the Karabük Range of the Central Pontides. The highest rate that belongs to oldest terrace level (841 ± 76 ka) also implies long-term mean uplift, which is well correlated with long term ( 350 ka) mean uplift rate obtained from fluvial terraces in the eastern flank of the (Gökırmak Basin) Central Pontides. These results indicate Quaternary activity of the Karabük Fault despite the fact that very low modern seismicity and partition of strain in the north of the North Anatolian Fault. Keywords: Tectonics, Geomorphology, Fluvial Terrace, OSL Dating, Central Pontides, North Anatolian Fault, Filyos River, Turkey, Central Anatolian Plateau

Unravelling recent environmental change in a lowland river valley, eastern Ireland: geoarchaeological applications

NASA Astrophysics Data System (ADS)

Foster, Gez; Turner, Jonathan

2010-05-01

This paper reports the preliminary findings of an Irish Heritage Council INSTAR funded research project on the geoarchaeology and fluvial geomorphology of the lower River Boyne valley, eastern Ireland. The nature and evolution of the contemporary Boyne floodplain at Dunmoe, Co. Meath (53° 40' 22.8" N, 6° 37' 54.7" W) has been investigated using a multi-technique approach combining field and terrestrial LiDAR-based geomorphological mapping, radiocarbon dating of channel migration activity, electrical resistivity tomography surveys of sub-surface topography and high-resolution X-ray and XRF geochemical characterisation of fine-grained sediment fill sequences. All of these lines of evidence support a tripartite sub-division of the floodplain. Valley marginal floodplain Zone 1 is characterised by a colluvial sediment fill which has buried an irregular ditch-basin-platform surface containing recent archaeological material. Subtle variations in mapped elevation suggest that the buried surface may represent the site of an abandoned river-side complex, possibly a small docking area or port. Geomorphological field relationships suggest that the possible archaeological site was connected to a former bank line position of the main River Boyne (floodplain Zone 2) via a small canal. Radiocarbon dating of Zone 2 channel gravels suggests that the channel associated with this bank position was abandoned some time before 1490-1610 AD. Subsequent vertical and lateral channel migration, the onset of which has been radiocarbon dated to the 17th or 18th century AD, led to the development of the lowest and most recent floodplain surface (Zone 3). The sedimentology and geochemistry of the Zone 2 and 3 fluvial sediment sequences suggests that recent centuries have involved an increase in fluvial flood risk, evidenced by the burial of alluvial soils by bedded, shell-rich sands. A more complete understanding of the timing and environmental drivers of increasing flood risk is anticipated from ongoing radionuclide (Pb-210 and Cs-137) and pollen analysis of the fluvial sediment sequences. However, based on the established chronology and geomorphic field relationships, it is plausible that the archaeological complex represents a late medieval site linked to Dunmoe Castle (14th to 17th century AD), which overlooks the floodplain.

The Topographic Design of River Channels for Form-Process Linkages.

PubMed

Brown, Rocko A; Pasternack, Gregory B; Lin, Tin

2016-04-01

Scientists and engineers design river topography for a wide variety of uses, such as experimentation, site remediation, dam mitigation, flood management, and river restoration. A recent advancement has been the notion of topographical design to yield specific fluvial mechanisms in conjunction with natural or environmental flow releases. For example, the flow convergence routing mechanism, whereby shear stress and spatially convergent flow migrate or jump from the topographic high (riffle) to the low point (pool) from low to high discharge, is thought to be a key process able to maintain undular relief in gravel bedded rivers. This paper develops an approach to creating riffle-pool topography with a form-process linkage to the flow convergence routing mechanism using an adjustable, quasi equilibrium synthetic channel model. The link from form to process is made through conceptualizing form-process relationships for riffle-pool couplets into geomorphic covariance structures (GCSs) that are then quantitatively embedded in a synthetic channel model. Herein, GCSs were used to parameterize a geometric model to create five straight, synthetic river channels with varying combinations of bed and width undulations. Shear stress and flow direction predictions from 2D hydrodynamic modeling were used to determine if scenarios recreated aspects of the flow convergence routing mechanism. Results show that the creation of riffle-pool couplets that experience flow convergence in straight channels requires GCSs with covarying bed and width undulations in their topography as supported in the literature. This shows that GCSs are a useful way to translate conceptualizations of form-process linkages into quantitative models of channel form.

Relationships between woody vegetation and geomorphological patterns in three gravel-bed rivers with different intensities of anthropogenic disturbance

NASA Astrophysics Data System (ADS)

Sitzia, T.; Picco, L.; Ravazzolo, D.; Comiti, F.; Mao, L.; Lenzi, M. A.

2016-07-01

We compared three gravel-bed rivers in north-eastern Italy (Brenta, Piave, Tagliamento) having similar bioclimate, geology and fluvial morphology, but affected by different intensities of anthropogenic disturbance related particularly to hydropower dams, training works and instream gravel mining. Our aim was to test whether a corresponding difference in the interactions between vegetation and geomorphological patterns existed among the three rivers. In equally spaced and sized plots (n = 710) we collected descriptors of geomorphic conditions, and presence-absence of woody species. In the less disturbed river (Tagliamento), spatial succession of woody communities from the floodplain to the channel followed a profile where higher elevation floodplains featured more developed tree communities, and lower elevation islands and bars were covered by pioneer communities. In the intermediate-disturbed river (Piave), islands and floodplains lay at similar elevation and both showed species indicators of mature developed communities. In the most disturbed river (Brenta), all these patterns were simplified, all geomorphic units lay at similar elevations, were not well characterized by species composition, and presented similar persistence age. This indicates that in human-disturbed rivers, channel and vegetation adjustments are closely linked in the long term, and suggests that intermediate levels of anthropogenic disturbance, such as those encountered in the Piave River, could counteract the natural, more dynamic conditions that may periodically fragment vegetated landscapes in natural rivers.

Geomorphic investigation of the Late-Quaternary landforms in the southern Zanskar Valley, NW Himalaya

NASA Astrophysics Data System (ADS)

Sharma, Shubhra; Hussain, Aadil; Mishra, Amit K.; Lone, Aasif; Solanki, Tarun; Khan, Mohammad Khatib

2018-02-01

The Suru, Doda and Zanskar river valleys in the semi-arid region of Southern Zanskar Ranges (SZR) preserve a rich repository of the glacial and fluvial landforms, alluvial fans, and lacustrine deposits. Based on detailed field observations, geomorphic mapping and limited optical ages, we suggest four glaciations of decreasing magnitude in the SZR. The oldest Southern Zanskar Glaciation Stage (SZS-4) is inferred from glacially polished bedrock and tillite pinnacles. The SZS-4 is ascribed to the Marine Isotopic Stage (MIS)-4/3. The subsequent SZS-3 is represented by obliterated and dissected moraines, and is assigned to MIS-2/Last Glacial Maximum. The multiple recessional moraines of SZS-2 glaciation are assigned the early to mid Holocene age whereas, the youngest SZS-1 moraines were deposited during the Little Ice Age. We suggest that during the SZS-2 glaciation, the Drang-Drung glacier shifted its course from Suru Valley (west) to the Doda Valley (east). The study area has preserved three generations of outwash gravel terraces, which broadly correlate with the phases of deglaciation associated with SZS-3, 2, and 1. The alluvial fan aggradation, lacustrine sedimentation, and loess deposition occurred during the mid-to-late Holocene. We suggest that glaciation was driven by a combination of the mid-latitude westerlies and the Indian Summer Monsoon during periods of cooler temperature, while phases of deglaciation occurred during enhanced temperature.

Morphodynamics of the Kulsi River Basin in the northern front of Shillong Plateau: Exhibiting episodic inundation and channel migration

NASA Astrophysics Data System (ADS)

Imsong, Watinaro; Choudhury, Swapnamita; Phukan, Sarat; Duarah, Bhagawat Pran

2018-02-01

The present study is undertaken in the Kulsi River valley, a tributary of the Brahmaputra River that drains through the tectonically active Shillong Plateau in northeast India. Based on the fluvial geomorphic parameters and Landsat satellite images, it has been observed that the Kulsi River migrated 0.7-2 km westward in its middle course in the past 30 years. Geomorphic parameters such as longitudinal profile analysis, stream length gradient index ( SL), ratio of valley floor width to valley height ( Vf), steepness index (ks) indicate that the upstream segment of the Kulsi River is tectonically more active than the downstream segment which is ascribed to the tectonic activities along the Guwahati Fault. ^{14}C ages obtained from the submerged tree trunks of the Chandubi Lake, which is located in the central part of the Kulsi River catchment suggests inundation (high lake levels) during 160 ± 50 AD, 970 ± 50 AD, 1190 ± 80 AD and 1520 ± 30 AD, respectively. These periods broadly coincide with the late Holocene strengthened Indian Summer Monsoon (ISM), Medieval Warm Period (MWP) and the early part of the Little Ice Age (LIA). The debris which clogged the course of the river in the vicinity of the Chandubi Lake is attributed to tectonically induced increase in sediment supply during high magnitude flooding events.

Detachment-limited erosion, alluvial transport, and relief in decaying landscapes

NASA Astrophysics Data System (ADS)

Johnstone, S. A.; Hilley, G. E.

2013-12-01

The correspondence between relief and erosion rates in tectonically active orogens suggests that erosion rates and relief adjust relatively rapidly to changes in the rates of tectonic processes. This rapid landscape response is at odds with the preservation of ancient orogens for 10s to 100s of millions of years after orogenesis has ceased. We hypothesize that this hysteresis in response times to the acceleration versus deceleration of tectonic rates results from a geomorphic process transition in fluvial networks. In steep landscapes found in tectonically active environments erosion is largely controlled by detachment-limited incision, whereas the increasing importance of alluvial transport in decaying landscapes controls relief and response time-scales in these situations. We present results from one-dimensional (profile) numerical modeling of channels undergoing topographic decay from an initial steady state following a cessation in uplift to understand process transitions that may reconcile the large differences in response times implied by active versus ancient mountain-belts. We performed dimensional analysis on the governing equations such that relief in the channels, process transitions between alluvial transport and detachment-limited erosion, and response times could be viewed in terms of dimensionless numbers that capture the relative strength of sediment transport, bedrock incision, and the initial uplift rate. We found that the form of the decaying profile is dictated by the relative ability of a system to incise vs. transport sediment. When sediment transport is inefficient relative to bedrock incision, models suggest that relief decays in a manner that preserves the overall channel profile geometry as channel slopes decline. In contrast, when the ability of a system to transport sediment greatly exceeds its ability to incise bedrock, decay will be dominated by the consumption of topography by slope retreat. We find that the declivity of the surface along which slopes retreat is set by the sediment transport slope of the fluvial network. As slope retreat progresses, the fraction of area undergoing rapid erosion (and therefore the sediment flux) decreases, which causes a perpetual decline in the sediment transport slope itself. This is manifest as a headward migrating transition from areas dominated by slope retreat to slope decline. While this behavior occurs to some degree in all simulations undergoing slope retreat, it is only clearly observed when steady state alluvial transport slopes are comparable to, but smaller than, bedrock incision slopes. For a given length scale we find that the evolution of relief through time, measured as the fraction of initial relief preserved, is independent of dimensionless fluvial erosion and transport coefficients. High sediment transport slopes can act to limit the rate of decay of relief in landscapes evolving by slope retreat. However, because slope decline occupies only the downstream portion of drainage networks in these cases, the majority of the relief reduction is typically accomplished by slope retreat. These results highlight the importance of erosional process transitions in shaping the relief of decaying landscapes.

Recent formation of arroyos in the Little Missouri Badlands of southwestern North Dakota

USGS Publications Warehouse

Gonzalez, M.A.

2001-01-01

In the Little Missouri Badlands of southwestern North Dakota, the channels of ephemeral streams are incised 2 to 10 m or more into mid-to-late Holocene alluvium. The objectives of this study were to determine the timing and cause(s) of the most recent episodes of fluvial incision and to develop a process-response model that illustrates the formation and evolution of arroyos in this region. The purpose was to distinguish natural from anthropogenic changes to the landscape and to discriminate allogenic from autogenic causes of incision, thereby gaining a greater sense of how steep, relatively small, ephemeral streams evolve. Dendrochronologic and dendrogeomorphic analyses of riparian cottonwoods provide an inexpensive, high-resolution dating method to constrain the time of incision, thereby permitting determination of the cause(s) of incision by evaluating environmental conditions prior to and at the onset of fluvial incision. An examination of seven small (10 to 100 km2) drainage basins indicated ephemeral streams have undergone a four-stage cycle of change within the past 200 years, comprising(i) an initial period of relative geomorphic stability with pedogenesis on the flood plain and low rates of lateral channel migration, (ii) a period of channel incision with subsequent widening of the flood plain through lateral corrasion along middle and upstream reaches, (iii) a concomitant period of aggradation along downstream reaches and, finally, (iv) a period of downstream incision. Dendrochronologic data and dendrogeomorphic relations indicate there have been three distinct periods of fluvial incision in the past 200 years. The first period of incision began in the 1860s and 1870s prior to the onset of European settlement and intensive grazing by domesticated cattle in the area. This period of incision occurred along the middle reaches of all seven of the streams examined and coincided with a severe, protracted drought, suggesting an allogenic cause. The second period of incision occurred during the end of the 19th century and into the 20th century along the upstream reaches of streams. This period of incision was mentioned in some written accounts of early settlers and coincided with the introduction of cattle and historical overgrazing of the region. However, overgrazing may not have caused the incision of this period, but instread exacerbated or accelerated the upstream migration of knickpoints formed earlier along middle reaches. A third period of incision has occurred in the past 20 years along the lower reaches of two of the seven streams examined. This incision was caused by the process of meander cutoff. This autogenic process decreases sinuosity and increases channel slope, stream power, and the potential to incise along adjacent stream reaches. ?? 2001 Elsevier Science B.V. All rights reserved.

Geomorphic change along a gravel bed river affected by volcanic eruption: Rio Blanco - Volcan Chaiten (South Chile)

NASA Astrophysics Data System (ADS)

Picco, Lorenzo; Ravazzolo, Diego; Ulloa, Hector; Iroumé, Andres; Aristide Lenzi, Mario

2014-05-01

Gravel bed rivers are environments shaped by the balance of flow, sediment regimes, large wood (LW) and vegetation. Geomorphic changes are response to fluctuations and changes of runoff and sediment supply involving mutual interactions among these factors. Typically, many natural disasters (i.e. debris flows, floods and forest fires) can affect the river basin dynamics. Explosive volcanic eruptions present, instead, the potential of exerting severe impacts as, for example, filling river valleys or changing river network patterns thanks to massive deposition of tephra and volcanic sediment all over the main channel and over the basin. These consistent impacts can strongly affect both hydrology and sediment transport dynamics, all over the river system, producing huge geomorphic changes. During the last years there has been a consistent increase in the survey technologies that permit to monitor geomorphic changes and to estimate sediment budgets through repeat topographic surveys. The calculation of differences between subsequent DEMs (difference of DEMs, DoD) is a commonly applied method to analyze and quantify these dynamics. Typically the higher uncertainty values are registered in areas with higher topographic variability and lower point density. This research was conducted along a ~ 2.2 km-long sub-reach of the Blanco River (Southern Chile), a fourth-order stream that presents a mainly rainfall regime with winter peak flows. The May 2008 Chaitén volcanic eruption strongly affected the entire Rio Blanco basin. The entire valley was highly exposed to the pyroclastic and fluvial flows, which affected directly a consistent area of evergreen forests. Extreme runoff from the upper Blanco catchment aggraded the channel and deposited up to several meters of tephra, alluvium, and LW along the entire river system. Aims of this contribution are to define and quantify the short term evolution of the Blanco River after the big eruption event and a subsequent consistent flood that happened in 2013. A post eruption airborne LiDAR data set (2009) and two different Terrestrial Laser Scanner (TLS) surveys carried out in 2013 and 2014 have been used to investigate this. We applied an approach to assessing spatially variable uncertainty in DoDs computation that is based on the creation of an ad hoc fuzzy inference system (FIS) that permits us to combine individually errors of different sources. Particularly attention was applied to define a new approach that permit to filter the huge amount of LW present into the active channel, depending on the superficial roughness values. After the LW filtering, the very high point clouds density allowed us to derive three high resolution DEMs. Topographic data were more accurate for exposed surfaces than those collected in wet areas. Two DoDs were computed, showing consistent erosion processes and deposition within the study area, and changes in geomorphic characteristics of channel and bars could also be detected, demonstrating a strong dynamicity of the study reach. This research is been developed within the framework of Project FONDECYT 1110609. Project "SedAlp: sediment management in Alpine basins, integrating sediment continuum, risk mitigation and hydropower", 83-4-3-AT, in the framework of the European Territorial Cooperation Program "Alpine Space" 2007-2013.

Geomorphic processes affecting meadow ecosystems [chapter 3

Treesearch

Jerry R. Miller; Dru Germanoski; Mark L. Lord

2011-01-01

Three geomorphic processes are of primary concern with respect to the current and future state of wet meadow ecosystems: channel incision, avulsion (the abrupt movement of the channel to a new location on the valley floor), and gully formation. Gully formation often is accompanied by upvalley headcut migration and a phenomenon referred to as "groundwater sapping...

Warming-induced upslope advance of subalpine forest is severely limited by geomorphic processes

PubMed Central

Macias-Fauria, Marc; Johnson, Edward A.

2013-01-01

Forests are expected to expand into alpine areas because of climate warming, causing land-cover change and fragmentation of alpine habitats. However, this expansion will only occur if the present upper treeline is limited by low-growing season temperatures that reduce plant growth. This temperature limitation has not been quantified at a landscape scale. Here, we show that temperature alone cannot realistically explain high-elevation tree cover over a >100-km2 area in the Canadian Rockies and that geologic/geomorphic processes are fundamental to understanding the heterogeneous landscape distribution of trees. Furthermore, upslope tree advance in a warmer scenario will be severely limited by availability of sites with adequate geomorphic/topographic characteristics. Our results imply that landscape-to-regional scale projections of warming-induced, high-elevation forest advance into alpine areas should not be based solely on temperature-sensitive, site-specific upper-treeline studies but also on geomorphic processes that control tree occurrence at long (centuries/millennia) timescales. PMID:23569221

Geomorphic degradations on the surface of venus: an analysis of venera 9 and venera 10 data.

PubMed

Florensky, C P; Ronca, L B; Basilevsky, A T

1977-05-20

On the basis of the physical and chemical measurements made on the surface of Venus and transmitted back to Earth by the Soviet automatic landers Venera 9 and Venera 10, a geomorphically inactive environment should be expected. An analysis of the television photographs reveals, however, that at least two processes of degradation occur. One operates on a scale of decimeters to meters and is responsible for the fracturing of a layered source rock and the subsequent downslope movement of the fragments. Mass-wasting, perhaps activated by venusian quakes or by unknown geological processes, is likely to be the agent. Another geomorphic degradation process occurs on the scale of a centimeter or less and is responsible for the rounding of edges and the pitting of rock surfaces. The agents of this process are not known, but atmospheric action, perhaps in connection with volcanic episodes, may be the cause. From a geomorphic point of view, the landscape of the Venera 9 landing site can be considered young and that of the Venera 10 landing site, mature.

Analyzing post-wildfire erosional processes and topographic change using hydrologic monitoring and Structure-from-Motion photogrammetry at the storm event scale

NASA Astrophysics Data System (ADS)

Leeper, R. J.; Barth, N. C.; Gray, A. B.

2017-12-01

Hydro-geomorphic response in recently burned watersheds is highly dependent on the timing and magnitude of subsequent rainstorms. Recent advancements in surveying and monitoring techniques using Unmanned Aerial Vehicles (UAV) and Structure-from-Motion (SfM) photogrammetry can support the rapid estimation of near cm-scale topographic response of headwater catchments (ha to km2). However, surface change due to shallow erosional processes such as sheetwash and rilling remain challenging to measure at this spatial extent and the storm event scale. To address this issue, we combined repeat UAV-SfM surveys with hydrologic monitoring techniques and field investigations to characterize post-wildfire erosional processes and topographic change on a storm-by-storm basis. The Las Lomas watershed ( 15 ha) burned in the 2016 San Gabriel Complex Fire along the front range of the San Gabriel Mountains, southern California. Surveys were conducted with a consumer grade UAV; twenty-six SfM control markers; two rain gages, and two pressure transducers were installed in the watershed. The initial SfM-derived point cloud generated from 422 photos contains 258 million points; the DEM has a resolution of 2.42 cm/pixel and a point density of 17.1 pts/cm2. Rills began forming on hillslopes and minor erosion occurred within the channel network during the first low intensity storms of the rainy season. Later more intense storms resulted in substantial geomorphic change. Hydrologic data indicate that during one of the intense storms total cumulative rainfall was 58.20 mm and peak 5-min intensity was 38.4 mm/hr. Poststorm field surveys revealed evidence of debris flows, flash flooding, erosion, and fluvial aggradation in the channel network, and rill growth and gully formation on hillslopes. Analyses of the SfM models indicate erosion dominated topographic change in steep channels and on hillslopes; aggradation dominated change in low gradient channels. A contrast of 5 cm exists between field measurements and change detected by differencing the SfM models. The quantitative and qualitative data sets obtained indicate that low-cost hydrologic monitoring techniques can be combined with SfM-derived high-resolution models to rapidly characterize post-wildfire hydrologic response and erosional processes on a storm event basis.

Fluvial processes in Puget Sound rivers and the Pacific Northwest [Chapter 3

Treesearch

John M. Buffington; Richard D. Woodsmith; Derek B. Booth; David R. Montgomery

2003-01-01

The variability of topography, geology, climate; vegetation, and land use in the Pacific Northwest creates considerable spatial and temporal variability of fluvial processes and reach-scale channel type. Here we identify process domains of typical Pacific Northwest watersheds and examine local physiographic and geologic controls on channel processes and response...

Orbital and Rover-based Exploration of Perseverance Valley, Endeavour Crater, Mars

NASA Astrophysics Data System (ADS)

Morgan, A. M.; Arvidson, R. E.; Duran Vinent, O.; Craddock, R. A.; Holo, S.; Gadal, C.; Blois, G.; Palucis, M. C.; Goudge, T. A.; Morgan, A. M.; Day, M.; Sullivan, R. J., Jr.; Umurhan, O. M.; Pähtz, T.; Birch, S.; Morgan, A. M.; Goudge, T. A.; Palucis, M. C.; Arvidson, R. E.; Duran Vinent, O.; Craddock, R. A.; Holo, S.; Blois, G.; Gadal, C.; Morgan, A. M.; Sullivan, R. J., Jr.; Day, M.; Arvidson, R. E.

2017-12-01

Perseverance Valley, based on orbital observations from the Mars Reconnaisance Orbiter HiRISE image data, is a 180 m long, 20 m wide anastomosing shallow channel system superimposed on the Cape Byron rim segment of the 22 km diameter Noachian-age Endeavour Crater on Mars. Several impact craters are superimposed on the valley system, indicating antiquity, although the valley's high degree of preservation indicates that it formed after significant regional-scale fluvial erosion and diffusive smoothing of Endeavour and its rim segments. The valley cuts into the inner, eastern rim on a 10˚ to 15˚ slope, and starts at a local low area on the rim crest. A set of shallow channels, some lined with perimeter rocks, extends from the west to meet the entrance to the valley. The western rim tilts to the west 0.8˚ and thus the channels tilt away from the valley entrance. The Mars Rover Opportunity has explored the western shallow channels leading up to the entrance to the valley. As of this writing Opportunity is located on the southern side of the valley entrance, with the Athena Science Team waiting until after solar conjunction to command the rover to descend into the valley to search for geomorphic and sedimentologic evidence related to valley formation. Wind erosion along radial fractures extending into and down Cape Byron is a possibility. Debris flows are also under consideration, perhaps enabled by melting ice at the rim crest. Dry avalanches are unlikely due to the low slopes. A fluvial origin is a strong contender based on models that show it is possible to have had a western catchment present when the Burns formation hydrated sulfates were being emplaced, followed by self-compaction of these sediments that tilted the western plains away from the rim crest. The key to testing among the various hypotheses for formation of the valley and shallow channels leading into the entrance will be the detailed stereo and multispectral imaging observations Opportunity will make of morphology and deposits at 20 m intervals during its descent along the valley floor. This will in fact be the first ground-based exploration of a candidate fluvial valley system on Mars, and will provide unique information on formation processes, including the role of water in shaping valley landforms.

On the control of riverbed incision induced by run-of-river power plant

NASA Astrophysics Data System (ADS)

Bizzi, Simone; Dinh, Quang; Bernardi, Dario; Denaro, Simona; Schippa, Leonardo; Soncini-Sessa, Rodolfo

2015-07-01

Water resource management (WRM) through dams or reservoirs is worldwide necessary to support key human-related activities, ranging from hydropower production to water allocation and flood risk mitigation. Designing of reservoir operations aims primarily to fulfill the main purpose (or purposes) for which the structure has been built. However, it is well known that reservoirs strongly influence river geomorphic processes, causing sediment deficits downstream, altering water, and sediment fluxes, leading to riverbed incision and causing infrastructure instability and ecological degradation. We propose a framework that, by combining physically based modeling, surrogate modeling techniques, and multiobjective (MO) optimization, allows to include fluvial geomorphology into MO optimization whose main objectives are the maximization of hydropower revenue and the minimization of riverbed degradation. The case study is a run-of-the-river power plant on the River Po (Italy). A 1-D mobile-bed hydro-morphological model simulated the riverbed evolution over a 10 year horizon for alternatives operation rules of the power plant. The knowledge provided by such a physically based model is integrated into a MO optimization routine via surrogate modeling using the response surface methodology. Hence, this framework overcomes the high computational costs that so far hindered the integration of river geomorphology into WRM. We provided numerical proof that river morphologic processes and hydropower production are indeed in conflict but that the conflict may be mitigated with appropriate control strategies.

Interpretation of recent alpine landscape system evolution using geomorphic mapping and L-band InSAR analyses

NASA Astrophysics Data System (ADS)

Imaizumi, Fumitoshi; Nishiguchi, Takaki; Matsuoka, Norikazu; Trappmann, Daniel; Stoffel, Markus

2018-06-01

Alpine landscapes are typically characterized by inherited features of past glaciations and, for the more recent past, by the interplay of a multitude of types of geomorphic processes, including permafrost creep, rockfalls, debris flows, and landslides. These different processes usually exhibit large spatial and temporal variations in activity and velocity. The understanding of these processes in a wide alpine area is often hindered by difficulties in their surveying. In this study, we attempt to disentangle recent changes in an alpine landscape system using geomorphic mapping and L-band DInSAR analyses (ALOS-PALSAR) in the Zermatt Valley, Swiss Alps. Geomorphic mapping points to a preferential distribution of rock glaciers on north-facing slopes, whereas talus slopes are concentrated on south-facing slopes. Field-based interpretation of ground deformation in rock glaciers and movements in talus slopes correlates well with the ratio of InSAR images showing potential ground deformation. Moraines formed during the Little Ice Age, rock glaciers, and talus slopes on north-facing slopes are more active than landforms on south-facing slopes, implying that the presence of permafrost facilitates the deformation of these geomorphic units. Such deformations of geomorphic units prevail also at the elevation of glacier termini. For rock cliffs, the ratio of images indicating retreat is affected by slope orientation and elevation. Linkages between sediment supply from rock cliffs and sediment transport in torrents are different among tributaries, affected by relative locations between sediment supply areas and the channel network. We conclude that the combined use of field surveys and L-band DInSAR analyses can substantially improve process understanding in steep, high-mountain terrain.

Spatial and temporal patterns of bank failure during extreme flood events: Evidence of nonlinearity and self-organised criticality at the basin scale?

NASA Astrophysics Data System (ADS)

Thompson, C. J.; Croke, J. C.; Grove, J. R.

2012-04-01

Non-linearity in physical systems provides a conceptual framework to explain complex patterns and form that are derived from complex internal dynamics rather than external forcings, and can be used to inform modeling and improve landscape management. One process that has been investigated previously to explore the existence of self-organised critical system (SOC) in river systems at the basin-scale is bank failure. Spatial trends in bank failure have been previously quantified to determine if the distribution of bank failures at the basin scale exhibit the necessary power law magnitude/frequency distributions. More commonly bank failures are investigated at a small-scale using several cross-sections with strong emphasis on local-scale factors such as bank height, cohesion and hydraulic properties. Advancing our understanding of non-linearity in such processes, however, requires many more studies where both the spatial and temporal measurements of the process can be used to investigate the existence or otherwise of non-linearity and self-organised criticality. This study presents measurements of bank failure throughout the Lockyer catchment in southeast Queensland, Australia, which experienced an extreme flood event in January 2011 resulting in the loss of human lives and geomorphic channel change. The most dominant form of fluvial adjustment consisted of changes in channel geometry and notably widespread bank failures, which were readily identifiable as 'scalloped' shaped failure scarps. The spatial extents of these were mapped using high-resolution LiDAR derived digital elevation model and were verified by field surveys and air photos. Pre-flood event LiDAR coverage for the catchment also existed allowing direct comparison of the magnitude and frequency of bank failures from both pre and post-flood time periods. Data were collected and analysed within a GIS framework and investigated for power-law relationships. Bank failures appeared random and occurred throughout the basin but plots of magnitude and frequency did display power-law scaling of failures. In addition, there was a lack of site specific correlations between bank failure and other factors such channel width, bank height and stream power. The data are used here to discuss the existence of SOC in fluvial systems and the relative role of local and basin-wide processes in influencing their distribution in space and time.

Experimental investigation into the impact of vegetation on fan morphology and flow

NASA Astrophysics Data System (ADS)

Clarke, Lucy; McLelland, Stuart; Coulthard, Tom

2013-04-01

Riparian vegetation can significantly influence the geomorphology of fluvial systems, affecting channel geometry and flow dynamics. However, there is still limited understanding of the role vegetation plays in the development of alluvial fans, despite the large number of vegetated fans located in temperate and humid climates. An understanding of the feedback loops between water flow, sediment dynamics and vegetation is key to understanding the geomorphological response of alluvial fans. But it is difficult to investigate these relationships in the natural world due to the complexity of the geomorphic and biological processes and timescales involved. To examine the effects of vegetation on channel form, flow dynamics and morphology during fan evolution, a series of experiments were conducted using the Total Environment Simulator at the Deep, an experimental facility operated by the University of Hull. The experiments followed a 'similarity of processes' approach and so were not scaled to a specific field prototype. Live vegetation (alfalfa) was used to simulate the influence of vegetation on the fan development. A range of experiments were conducted on fan plots 2x2m in size, the same initial conditions and constant water discharge and sediment feed rates were used, but the vegetation density and amount of geomorphic time (when the sediment and water were running and there was active fan development) between seeding / vegetation growth varied between runs. The fan morphology was recorded at regular intervals using a laser scanner (at 1mm resolution) and high resolution video recording and overhead photography was also used to gain near-continuous data quantifying fan topography, flow patterns, channel migration and avulsion frequency. Image analysis also monitored the spatial extent of vegetation establishment. The use of these techniques allowed collection of high resolution spatial and temporal data on fan development with minimal disruption to the experiments. The results of the preliminary experiments showed that vegetation did influence the morphology and flow conditions during fan evolution. Vegetation reduced the number of active channels, and increasing the vegetation density also led to lower lateral migration rates, the formation of narrower and deeper channels and an increase in fan slope.

Fluvial erosion as a mechanism for crater modification on Titan

USGS Publications Warehouse

Neish, Catherine D.; Molaro, J. L.; Lora, J. M.; Howard, A.D.; Kirk, Randolph L.; Schenk, P.; Bray, V.J.; Lorenz, R.D.

2016-01-01

There are few identifiable impact craters on Titan, especially in the polar regions. One explanation for this observation is that the craters are being destroyed through fluvial processes, such as weathering, mass wasting, fluvial incision and deposition. In this work, we use a landscape evolution model to determine whether or not this is a viable mechanism for crater destruction on Titan. We find that fluvial degradation can modify craters to the point where they would be unrecognizable by an orbiting spacecraft such as Cassini, given enough time and a large enough erosion rate. A difference in the erosion rate between the equator and the poles of a factor of a few could explain the latitudinal variation in Titan’s crater population. Fluvial erosion also removes central peaks and fills in central pits, possibly explaining their infrequent occurrence in Titan craters. Although many craters on Titan appear to be modified by aeolian infilling, fluvial modification is necessary to explain the observed impact crater morphologies. Thus, it is an important secondary modification process even in Titan’s drier equatorial regions.

Biosorption behavior and mechanism of cesium-137 on Rhodosporidium fluviale strain UA2 isolated from cesium solution.

PubMed

Lan, Tu; Feng, Yue; Liao, Jiali; Li, Xiaolong; Ding, Congcong; Zhang, Dong; Yang, Jijun; Zeng, Junhui; Yang, Yuanyou; Tang, Jun; Liu, Ning

2014-08-01

In order to identify a more efficient biosorbent for (137)Cs, we have investigated the biosorption behavior and mechanism of (137)Cs on Rhodosporidium fluviale (R. fluviale) strain UA2, one of the dominant species of a fungal group isolated from a stable cesium solution. We observed that the biosorption of (137)Cs on R. fluviale strain UA2 was a fast and pH-dependent process in the solution composed of R. fluviale strain UA2 (5 g/L) and cesium (1 mg/L). While a Langmuir isotherm equation indicated that the biosorption of (137)Cs was a monolayer adsorption, the biosorption behavior implied that R. fluviale strain UA2 adsorbed cesium ions by electrostatic attraction. The TEM analysis revealed that cesium ions were absorbed into the cytoplasm of R. fluviale strain UA2 across the cell membrane, not merely fixed on the cell surface, which implied that a mechanism of metal uptake contributed largely to the cesium biosorption process. Moreover, PIXE and EPBS analyses showed that ion-exchange was another biosorption mechanism for the cell biosorption of (137)Cs, in which the decreased potassium ions were replaced by cesium ions. All the above results implied that the biosorption of (137)Cs on R. fluviale strain UA2 involved a two-step process. The first step is passive biosorption that cesium ions are adsorbed to cells surface by electrostatic attraction; after that, the second step is active biosorption that cesium ions penetrate the cell membrane and accumulate in the cytoplasm. Copyright © 2014 Elsevier Ltd. All rights reserved.

Anthropogenic features and hillslope processes interaction

NASA Astrophysics Data System (ADS)

Tarolli, Paolo; Sofia, Giulia

2016-04-01

Topography emerges as a result of natural driving forces, but some human activities (such as mining, agricultural practices and the construction of road networks) directly or indirectly move large quantities of soil, which leave clear topographic signatures embedded on the Earth's morphology. These signatures can cause drastic changes to the geomorphological organization of the landscape, with direct consequences on Earth surface processes (Tarolli and Sofia, 2016). To this point, the present research investigates few case studies highlighting the influences of anthropogenic topographic signatures on hillslope processes, and it shows the effectiveness of High-Resolution Topography (HRT) derived from the recent remote sensing technologies (e.g. lidar, satellite, structure from motion photogrammetry), to better understand this interaction. The first example is related to agricultural terraces. In recent times, terraced areas acquired a new relevance to modern concerns about erosion and land instability, being the agricultural land mostly threatened by abandonment or intensification and specialization of agriculture, resulting in more landslide-prone bench terraces, or heavy land levelling with increased erosion. The second case study discusses about the role of agricultural and forest roads on surface erosion and landslides. The third case study investigates geomorphic processes in an open pit mine. In all case studies, HRT served as the basis for the development of new methodologies able to recognize and analyze changes on Earth surface processes along hillslopes. The results show how anthropogenic elements have crucial effects on sediment production and sediment delivery, also influencing the landscape connectivity. The availability of HRT can improve our ability to actually model anthropogenic morphologies, quantify them, and analyse the links between anthropogenic elements and geomorphic processes. The results presented here, and the creation and dissemination of HR datasets might allow the transfer the knowledge of geomorphic processes from the scientific to the practical world. Thus, it may allow an improved understanding and targeted mitigation of geomorphic changes during anthropogenic development and help guide future research directions for development-based watershed studies. References Tarolli, P., Sofia, G. (2016). Human topographic signatures and derived geomorphic processes across landscapes, Geomorphology, 255, 140-161, 10.1016/j.geomorph.2015.12.007.

Hillslope to fluvial process domain transitions in headwater catchments

NASA Astrophysics Data System (ADS)

Williams, Karen Mary

The landscape is partitioned into hillslopes and unchanneled valleys (hollows), and colluvial (hillslope controlled) and alluvial (self-formed) channels. The key issue for any study of headwater catchments is the rational distinction between these elements. Accurate identification of process domain transitions from hillslopes to hollows, hollows to colluvial channels and colluvial to alluvial channels, are not obvious either in the field or from topographic data derived from remotely sensed data such as laser derived (LIDAR) digital elevation models. The research in this dissertation investigates the spatial arrangement of these landforms and how hillslope and fluvial process domains interact in two pairs of headwater catchments in southwest and central Montana, using LIDAR data. This dissertation uses digital terrain analysis of LIDAR-derived topography and field studies to investigate methods of detection, modeling, and prediction of process transitions from the hillslope to fluvial domains and within the fluvial domain, from colluvial to alluvial channel reaches. Inflections in the scaling relationships between landscape parameters such as flowpath length, unit stream power (a metric of the energy expended by the channel in doing work), and drainage area were used to detect transitions in flow regimes characteristic of hillslope, unchanneled valleys, and channeled landforms. Using the scale-invariant properties of fluvial systems as a threshold condition, magnitude-frequency distributions of curvature and the derivative of aspect were also used to detect hillslope, fluvial, and transitional process domains. Finally, within the classification of channeled landforms, the transition from colluvial to alluvial channels was detected using the presence/absence of repeating patterns in the power spectra of fluvial energy and channel form parameters. LIDAR-derived scaling relations and magnitude-frequency distributions successfully detected and predicted locations of mapped channel heads and hollows and spatial regions of process transitions. Subreaches of arguably alluvial channel conditions were also identified in power spectra. However, extrinsic forcing limits ability to detect a clear transition from colluvial to fully alluvial conditions. Headwater catchments present a mosaic of process domains, in large determined by local structure and lithology. However, process domain transitions appear detectable and statistically, though not deterministically, predictable, irrespective of setting.

Hydrograph Shape Controls Channel Morphology and Organization in a Sand-Gravel Flume

NASA Astrophysics Data System (ADS)

Hempel, L. A.; Grant, G.; Hassan, M. A.; Eaton, B. C.

2016-12-01

A fundamental research question in fluvial geomorphology is to understand what flows shape river channels. Historically, the prevailing view has been that channel dimensions adjust to a so-termed "dominant discharge", which is often approximated as the bankfull flow. But using a single flow to reference the geomorphic effectiveness of an entire flow regime discounts many observations showing that different flows control different channel processes. Some flows entrain fine sediment, some entrain the full size distribution of bed sediment; some destabilize or build bars, some erode the banks, and so forth. To explore the relation between the full flow regime and channel morphology, we conducted a series of flume experiments to examine how hydrographs with different shapes, durations, and magnitudes result in different degrees of channel organization, which we define in terms of the regularity, spacing and architecture of self-formed channel features, such as bed patches, geometry and spacing of bedforms, and channel planform. Our experiments were run in a 12m long adjustable-width flume that developed a self-formed meandering, pool-riffle pattern. We found that hydrograph shape does control channel organization. In particular, channels formed by hydrographs with slower rising limbs and broader peaks were more organized than those formed by flashier hydrographs. To become organized, hydrographs needed to exceed a minimum flow threshold, defined by the intensity of sediment transport; below which the channel lacked bedforms and a regular meander pattern. Above an upper flow threshold, bars became disorganized and the channel planform transitioned towards braiding. Field studies of channels with different flow regimes but located in a similar physiographic setting support our experimental findings. Taken together, this work points to the importance of the hydrograph as a fundamental control on channel morphology, and offers the prospect of better understanding how changing hydrologic regimes, either through climate, land use, or dams, translates into geomorphic changes.

Characterizing the transient geomorphic response to base-level fall in the northeastern Tibetan Plateau

NASA Astrophysics Data System (ADS)

Zhang, Huiping; Kirby, Eric; Pitlick, John; Anderson, Robert S.; Zhang, Peizhen

2017-02-01

Analysis of hillslope gradient, landscape relief, and channel steepness in the Daxia River basin provides evidence of a transient geomorphic response to base-level fall on the northeastern Tibetan Plateau. Low-gradient channels and gentle hillslopes of the upper watershed are separated from a steeper, high-relief landscape by a series of convex knickzones along channel longitudinal profiles. Downstream projection of the "relict" portions of the profiles implies 800-850 m of incision, consistent with geologic and geomorphic records of post 1.7 Ma incision in the lower watershed. We combine optically stimulated luminescence dating of fluvial terrace deposits to constrain incision rates downstream of knickpoints with catchment-averaged 10Be concentrations in modern sediment to estimate erosion rates in tributary basins both above and below knickpoints. Both sources of data imply landscape lowering rates of 300 m Ma-1 below the knickpoint and 50-100 m Ma-1 above. Field measurements of channel width (n = 48) and calculations of bankfull discharge (n = 9) allow determination of scaling relations among channel hydraulic geometry, discharge, and contributing area that we employ to estimate the patterns of basal shear stress, unit stream power, and bed load transport rate throughout the channel network. Our results imply a clear downstream increase of incision potential; this result would appear to be consistent with a detachment-limited response to imposed base-level fall, in which steepening of channels drives an increase in erosion rates. In contrast, however, we do not observe apparent narrowing of channels across the transition from slowly eroding to rapidly eroding portions of the watershed. Rather, the present-day channel morphology as well as its scaling of hydraulic geometry imply that the river is primarily adjusted to transport its sediment load and suggest that channel morphology may not always reflect the presence of knickpoints and differences in landscape relief.

Quaternary landscape development, alluvial fan chronology and erosion of the Mecca Hills at the southern end of the San Andreas Fault zone

USGS Publications Warehouse

Gray, Harrison J.; Owen, Lewis A.; Dietsch, Craig; Beck, Richard A.; Caffee, Marc A.; Finkelman, Robert B.; Mahan, Shannon

2014-01-01

Quantitative geomorphic analysis combined with cosmogenic nuclide 10Be-based geochronology and denudation rates have been used to further the understanding of the Quaternary landscape development of the Mecca Hills, a zone of transpressional uplift along the southern end of the San Andreas Fault, in southern California. The similar timing of convergent uplifts along the San Andreas Fault with the initiation of the sub-parallel San Jacinto Fault suggest a possible link between the two tectonic events. The ages of alluvial fans and the rates of catchment-wide denudation have been integrated to assess the relative influence of climate and tectonic uplift on the development of catchments within the Mecca Hills. Ages for major geomorphic surfaces based on 10Be surface exposure dating of boulders and 10Be depth profiles define the timing of surface stabilization to 2.6 +5.6/–1.3 ka (Qyf1 surface), 67.2 ± 5.3 ka (Qvof2 surface), and 280 ± 24 ka (Qvof1 surface). Comparison of 10Be measurements from active channel deposits (Qac) and fluvial terraces (Qt) illustrate a complex history of erosion, sediment storage, and sediment transport in this environment. Beryllium-10 catchment-wide denudation rates range from 19.9 ± 3.2 to 149 ± 22.5 m/Ma and demonstrate strong correlations with mean catchment slope and with total active fault length normalized by catchment area. The lack of strong correlation with other geomorphic variables suggests that tectonic uplift and rock weakening have the greatest control. The currently measured topography and denudation rates across the Mecca Hills may be most consistent with a model of radial topographic growth in contrast to a model based on the rapid uplift and advection of crust.

Geologic map of MTM -45252 and-45257 quadrangles, Reull Vallis region of Mars

USGS Publications Warehouse

Mest, Scott C.; Crown, David A.

2003-01-01

Mars Transverse Mercator (MTM) quadrangles -45252 and -45257 (latitude 42.5° S. to 47.5°S., longitude 250° W. to 260° W.) cover a portion of the highlands of Promethei Terra east of Hellas basin. The map area consists of heavily cratered ancient highland materials having moderate to high relief, isolated knobs and massifs of rugged mountainous material, and extensive tracts of smooth and channeled plains. Part of the ~1,500-km-long Reull Vallis outflow system is within the map area. The area also contains surficial deposits, such as the prominent large debris aprons that commonly surround highland massifs. Regional slopes are to the west, toward the Hellas basin, as indicated by topographic maps of Mars. Approximately 60 percent of the surface of Mars is covered by rugged, heavily cratered terrains believed to represent the effects of heavy bombardment in the inner solar system about 4.0 billion years ago. Much of this terrain, including that within the map area, records a long history of modification by tectonism, fluvial processes, mass wasting, and eolian activity. The presence of fluvial features to the east of Hellas basin, including Reull Vallis and other smaller channels, has significant implications for past environmental conditions. The degraded terrains surrounding Hellas basin provide constraints on the role and timing of volatile-driven activity in the evolution of the highlands. Current photogeologic mapping at 1:500,000 scale (see also Mest and Crown, 2002) from analysis of Viking Orbiter images complements previous geomorphic studies of Reull Vallis and other highland outflow systems, drainage networks, and highland debris aprons, as well as regional geologic mapping studies and geologic mapping of Hellas basin as a whole at 1:5,000,000 scale. Viking Orbiter image coverage of the map area generally ranges from 160 to 220 m/pixel; the central part of the map area is covered by higher resolution images of about 47 m/pixel. Crater size-frequency distributions have been compiled to constrain the relative ages of geologic units and determine the timing and duration of inferred geologic processes.

Geomorphic mapping to support river restoration on the Trinity River downstream from Lewiston Dam, California, 1980-2011

USGS Publications Warehouse

Curtis, Jennifer A.; Guerrero, Timothy M.

2015-01-01

Historic land use, dam construction, water storage, and flow diversions in the Trinity River watershed have resulted in downstream geomorphic change, loss of salmonid habitat, and declines in salmonid populations. The USGS in cooperation with the Trinity River Restoration Program, a multi-agency partnership tasked with implementing federally mandated restoration, completed a geomorphic change assessment to inform the planning process for future restoration work. This report documents an ARCMAP geodatabase (v.10.0) containing geomorphic features digitized from a series of rectified orthophotographs (http://dx.doi.org/10.5066/F7TT4P04). Upland, riparian, and channel features were digitized from six available base images (1980, 1997, 2001, 2006, 2009, and 2011). This report describes the structure of the geodatabase and the methods used to delineate individual geomorphic features.

Anthropogenic control on geomorphic process rates: can we slow down the erosion rates? (Geomorphology Outstanding Young Scientist Award & Penck Lecture)

NASA Astrophysics Data System (ADS)

Vanacker, V.

2012-04-01

The surface of the Earth is changing rapidly, largely in response to anthropogenic perturbation. Direct anthropogenic disturbance of natural environments may be much larger in many places than the (projected) indirect effects of climate change. There is now large evidence that humans have significantly altered geomorphic process rates, mainly through changes in vegetation composition, density and cover. While much attention has been given to the impact of vegetation degradation on geomorphic process rates, I suggest that the pathway of restoration is equally important to investigate. First, vegetation recovery after crop abandonment has a rapid and drastic impact on geomorphic process rates. Our data from degraded catchments in the tropical Andes show that erosion rates can be reduced by up to 100 times when increasing the protective vegetation cover. During vegetation restoration, the combined effects of the reduction in surface runoff, sediment production and hydrological connectivity are stronger than the individual effects together. Therefore, changes in erosion and sedimentation during restoration are not simply the reverse of those observed during degradation. Second, anthropogenic perturbation causes a profound but often temporary change in geomorphic process rates. Reconstruction of soil erosion rates in Spain shows us that modern erosion rates in well-vegetated areas are similar to long-term rates, despite evidence of strong pulses in historical erosion rates after vegetation clearance and agriculture. The soil vegetation system might be resilient to short pulses of accelerated erosion (and deposition), as there might exist a dynamic coupling between soil erosion and production also in degraded environments.

Numerical simulation of geomorphic, climatic and anthropogenic drivers of soil distribution on semi-arid hillslopes

NASA Astrophysics Data System (ADS)

Willgoose, G. R.; Cohen, S.; Svoray, T.; Sela, S.; Hancock, G. R.

2010-12-01

Numerical models are an important tool for studying landscape processes as they allow us to isolate specific processes and drivers and test various physics and spatio-temporal scenarios. Here we use a distributed physically-based soil evolution model (mARM4D) to describe the drivers and processes controlling soil-landscape evolution on a field-site at the fringe between the Mediterranean and desert regions of Israel. This study is an initial effort in a larger project aimed at improving our understanding of the mechanisms and drivers that led to the extensive removal of soils from the loess covered hillslopes of this region. This specific region is interesting as it is located between the Mediterranean climate region in which widespread erosion from hillslopes was attributed to human activity during the Holocene and the arid region in which extensive removal of loess from hillslopes was shown to have been driven by climatic changes during the late-Pleistocene. First we study the sediment transport mechanism of the soil-landscape evolution processes in our study-site. We simulate soil-landscape evolution with only one sediment transport process (fluvial or diffusive) at a time. We find that diffusive sediment transport is likely the dominant process in this site as it resulted in soil distributions that better corresponds to current observations. We then simulate several realistic climatic/anthropogenic scenarios (based on the literature) in order to quantify the sensitivity of the soil-landscape evolution process to temporal fluctuations. We find that this site is relatively insensitive to short term (several thousands of years) sharp, changes. This suggests that climate, rather then human activity, was the main driver for the extensive removal of loess from the hillslopes.

Characterization of geomorphic units in the alluvial valleys and channels of Gulf Coastal Plain rivers in Texas, with examples from the Brazos, Sabine, and Trinity Rivers, 2010

USGS Publications Warehouse

Coffman, David K.; Malstaff, Greg; Heitmuller, Franklin T.

2011-01-01

The U.S. Geological Survey, in cooperation with the Texas Water Development Board, described and characterized examples of geomorphic units within the channels and alluvial valleys of Texas Gulf Coastal Plain rivers using a geomorphic unit classification scale that differentiates geomorphic units on the basis of their location either outside or inside the river channel. The geomorphic properties of a river system determine the distribution and type of potential habitat both within and adjacent to the channel. This report characterizes the geomorphic units contained in the river channels and alluvial valleys of Texas Gulf Coastal Plain rivers in the context of the River Styles framework. This report is intended to help Texas Instream Flow Program practitioners, river managers, ecologists and biologists, and others interested in the geomorphology and the physical processes of the rivers of the Texas Gulf Coastal Plain (1) gain insights into how geomorphic units develop and adjust spatially and temporally, and (2) be able to recognize common geomorphic units from the examples cataloged in this report. Recent aerial imagery (high-resolution digital orthoimagery) collected in 2008 and 2009 were inspected by using geographic information system software to identify representative examples of the types of geomorphic units that occurred in the study area. Geomorphic units outside the channels of Texas Gulf Coastal Plain rivers are called \\"valley geomorphic units\\" in this report. Valley geomorphic units for the Texas Gulf Coastal Plain rivers described in this report are terraces, flood plains, crevasses and crevasse splays, flood-plain depressions, tie channels, tributaries, paleochannels, anabranches, distributaries, natural levees, neck cutoffs, oxbow lakes, and constructed channels. Channel geomorphic units occur in the river channel and are subject to frequent stresses associated with flowing water and sediment transport; they adjust (change) relatively quickly in response to short-term variations in flow. Channel geomorphic units described in this report are channel banks, benches and ledges, bank failures, point bars, cross-bar channels, channel bars, exposed bedrock, pools, runs, and crossovers.

Including Deposition Rate in Models of Cosmogenic Nuclide Accumulation in Fluvial Sediments to Improve Terrace Abandonment Ages

NASA Astrophysics Data System (ADS)

Norton, K. P.; Wang, N.; Van Dissen, R. J.; Little, T.

2017-12-01

Fluvial sediments are archives of the erosional, transport, and depositional processes occurring in the catchment. Terraces become robust markers for geomorphic analysis if their time of abandonment can be determined. Methods such as OSL can determine burial ages for fine grained sediments within the terrace fill but may not be directly related to the terrace abandonment age. Cosmogenic nuclides can be used to determine exposure ages for geologically young terraces but the surface being dated may have been subsequently eroded and the material itself may have been deposited with an inherited nuclide concentration. To deal with this problem, many researchers collect multiple samples with depth to model the depth-dependent nuclide concentration to help constrain inheritance and post-depositional erosion. It is often, however, assumed that the entire sediment pile accumulated instantaneously. In this submission, we present the results of a depth profile model that incorporates sediment accumulation rate to improve terrace age estimates. We test this model on fault-offset river terraces near Kaikoura, New Zealand. We measured depth profiles of OSL ages and cosmogenic nuclide concentrations of two late Quaternary terraces that are offset by up to 800 m across the Kekerengu Fault. OSL ages and dated tephras in the overlying loess provide minimum age constraints for both terraces while OSL ages of fine-grained sediments within the fill provide depositional ages. The predicted sedimentation rates for the terraces are as high as 0.5m/yr, consistent with geologically instantaneous deposition. Modelled abandonment ages from cosmogenic nuclides for the terraces are consistent with OSL and tephra constraints at 9.7 +/- 3.8 ka and 30.4 +/- 2.1 ka, respectively. These terrace abandonment ages yield dextral slip rates of 18.5-20.5 mm/yr and 25-28 mm/yr, respectively, consistent with the rapid slip rate on the adjacent Hope Fault.

Temporal and spatial scales of geomorphic adjustments to reduced competency following flow regulation in bedload-dominated systems

NASA Astrophysics Data System (ADS)

Curtis, Katherine E.; Renshaw, Carl E.; Magilligan, Francis J.; Dade, William B.

2010-05-01

Because of the combined effects of reduced sediment transport capacity and competency following flow regulation, morphological changes are expected to occur in channels downstream from dams and, specifically, at tributary junctions where local inputs of water and sediment occur. Using a combination of historical aerial photographs, mainstem- and tributary-channel pebble counts, and HEC-RAS flow modeling for two watersheds in south-central VT, one unregulated and the other regulated since 1961, we document the time series of post-regulation channel narrowing and associated bar growth due to the influx of tributary sediment. Channel adjustments at regulated tributary junctions have been significant in ca. 50 years following impoundment, with channels downstream of the confluences narrowing over 15% after an initial ca. 20-year lag before the onset of accelerated narrowing. Moreover, flow modeling suggests that downstream of regulated confluences, the modern median grain size ( d50) along the channel bed is immobile. No significant channel narrowing has occurred either above or below unregulated tributary junctions or on the mainstem upstream of regulated confluences. However, greater channel sediment fining is observed upstream of regulated confluences than above unregulated confluences. Thus, the primary mode of mainstem channel adjustment differs up- and downstream of regulated tributaries. These confluence effects have occurred where the tributary drainage area is only 0.2 times that of the mainstem, well below the threshold ratio of 0.6 required for significant geomorphic effects at unregulated confluences, highlighting the geomorphic scale shift of dams. Lastly, we evaluate the downstream length required for a river to recover from the impacts of impoundment and demonstrate that even distal locations are impacted by flow regulation. Unlike the impacts of flow regulation in the western US where channel incision and bar erosion predominate following impoundment, we find that in situations where bed incision is minimal and where sediment loads are low but bed caliber high, bar growth and channel narrowing are significant adjustments at tributary junctions following impoundment. Therefore, at our sites the effects of dams on reduced competency may be more profound than on reduced sediment transport capacity, highlighting the importance of geologic and geomorphic settings in understanding fluvial responses to impoundment.

Basin Wide Erosion and Soil Production Rates of a High Altitude Plateau in the Korean Peninsula Considered as an Uplifted Paleo Erosional Surface: Implications for Its Development Process and the Tectonics

NASA Astrophysics Data System (ADS)

Byun, J.; Seong, Y.

2012-12-01

The development process of High Altitude Plateaus (HAPs) has been a controversial issue in geomorphology. HAPs have been interpreted as uplifted erosional surfaces mainly controlled by fluvial processes. Recent studies, however, argued that the definition of the Paleo Erosional Surfaces (PESs) is ambiguous and HAPs, considered as the uplifted PESs, could be formed under various local lithologic, tectonic and climatic conditions. But these suggestions were severely limited by the lack of quantitative data in the field. Here, we investigate this issue of the development process of HAPs through estimating both basin wide erosion rates and soil production rates of the Daegwanryeong area in the Korean Peninsula (KP), where a HAP with low-relief hilly landscape is found. Study area has been known as a typical one of PESs in the KP, which have been uplifted since the early Miocene. Particularly deeply weathered saprolites, easily found in the study area, have also been believed to be resulted from the Tertiary deep weathering under higher temperature at the paleo sea level. First, analysis of 10Be in saprolite from the base of the soil column, except one under no soil mantle, shows that soil production rates decline linearly with increasing soil depth. These data provide a soil production function with a maximum soil production rate of 70.6m/m.y. under 24cm of soil and a minimum of 22m/m.y. under 75cm of soil. Accordingly it means that the interface between soil and saprolite have gone down maximum 141.2 m since the Quaternary. Thus it suggests that the saprolites are the results under current local climatic and geomorphic conditions rather than the relict of the Tertiary deep weathering. Second, measurements of 10Be in alluvial sediments show that the average erosion rate (70.7m/m.y.) of the study area is close to the maximum soil production rate, thus basin wide erosion rates of the study area are controlled by the current soil production rates. It means that about 1,400m has been eroded off since the early Miocene, when uplift of the KP seems to begin. Consequently it is difficult to think the HAP of the study area as the PES as well as one, which has been eroded keeping the original form of the PES. Furthermore, the erosion rates are lower than the uplift rates during the late Quaternary (about 300m/m.y.), but similar to the uplift rates before the early Miocene (about 100m/m.y.). Therefore, it suggests that the HAP of the study area has been uplifted since the early Miocene, but has not approached the steady state with the neotectonics of the KP. In summary, we suggest that the HAP of the study area is the result of the geomorphic process under current climatic and geomorphic condition rather than the relict of the PES.

Occurrence and Distribution of Ordinary High Water Mark (OHWM) Indicators in Non-Perennial Streams in the Western Mountains, Valleys, and Coast Region of the United States

DTIC Science & Technology

2014-08-01

1 Common hydrogeomorphic units that form in stream systems in response to spatially and temporally varying hydrologic and geomorphic processes... geomorphic , and vegetative indica- tors for use in OHWM delineations in arid streams and categorized their typical landscape positions with respect...the presence of a bed and banks. Hydrogeomorphic units are distinct macro- scale geomorphic features formed within stream systems in response to

GEOMORPHIC THRESHOLDS AND CHANNEL MORPHOLOGY IN LARGE RIVERS

EPA Science Inventory

Systematic changes in channel morphology occur as channel gradient, streamflow, and sediment character change and interact. Geomorphic thresholds of various kinds are useful metrics to define these changes along the river network, as they are based on in-channel processes that d...

Using Mars's Sulfur Cycle to Constrain the Duration and Timing of Fluvial Processes

NASA Technical Reports Server (NTRS)

Blaney, D. L.

2002-01-01

Sulfur exists in high abundances at diverse locations on Mars. This work uses knowledge of the Martian sulfate system to discriminate between leading hypotheses and discusses the implications for duration and timing of fluvial processes. Additional information is contained in the original extended abstract.

Influences of geomorphology and geology on alpine treeline in the American West - More important than climatic influences?

USGS Publications Warehouse

Butler, D.R.; Malanson, G.P.; Walsh, S.J.; Fagre, D.B.

2007-01-01

The spatial distribution and pattern of alpine treeline in the American West reflect the overarching influences of geological history, lithology and structure, and geomorphic processes and landforms, and geologic and geomorphic factors—both forms and processes—can control the spatiotemporal response of the ecotone to climate change. These influences occur at spatial scales ranging from the continental scale to fine scale processes and landforms at the slope scale. Past geomorphic influences, particularly Pleistocene glaciation, have also left their impact on treeline, and treelines across the west are still adjusting to post-Pleistocene conditions within Pleistocene-created landforms. Current fine scale processes include solifluction and changes on relict solifluction and digging by animals. These processes should be examined in detail in future studies to facilitate a better understanding of where individual tree seedlings become established as a primary response of the ecotone to climate change.

Geomorphic considerations for erosion prediction

USGS Publications Warehouse

Osterkamp, W.R.; Toy, T.J.

1997-01-01

Current soil-erosion prediction technology addresses processes of rainsplash, overland-flow sediment transport, and rill erosion in small watersheds. The effects of factors determining sediment yield from larger-scale drainage basins, in which sediment movement is controlled by the combined small-scale processes and a complex set of channel and other basin-scale sediment-delivery processes, such as soil creep, bioturbation, and accelerated erosion due to denudation of vegetation, have been poorly evaluated. General suggestions are provided for the development of erosion-prediction technology at the geomorphic or drainage-basin scale based on the separation of sediment-yield data for channel and geomorphic processes from those of field-scale soil loss. An emerging technology must consider: (1) the effects on sediment yield of climate, geology and soils, topography, biotic interactions with other soil processes, and land-use practices; (2) all processes of sediment delivery to a channel system; and (3) the general tendency in most drainage basins for progressively greater sediment storage in the downstream direction.

Landform-related permafrost characteristics in the source area of the Yellow River, eastern Qinghai-Tibet Plateau

NASA Astrophysics Data System (ADS)

Li, Jing; Sheng, Yu; Wu, Jichun; Feng, Ziliang; Ning, Zuojun; Hu, Xiaoying; Zhang, Xiumin

2016-09-01

The source area of the Yellow River (SAYR) lies in the eastern part of the Qinghai-Tibet Plateau (QTP). Glaciers are absent in the area, but permafrost is widespread because of the high elevations, typically 4200-5000 m a.s.l. Landforms in the SAYR were classified into seven basic types, based on their morphological characteristics and genesis, and further divided into 12 sub-classes based on geomorphic processes. Permafrost development and ground temperature in boreholes were analyzed on representative landforms in the SAYR. Permafrost was discontinuously distributed at 4300-4400 m a.s.l. in fluvial plains because of variations in local topography, sediments, vegetation and water content. In hills and low-relief mountains in the western part of the study area, permafrost is continuous above 4400 m a.s.l. even on unshaded south-facing slopes. In contrast, permafrost in the central part of the study area is discontinuous over this elevation range. Analysis of ground temperature measurements revealed that three macro-scale factors, latitude, longitude, and elevation, explain 72.8% of the variation in the measured mean annual ground temperature (MAGT). The remaining 27.2% can potentially be explained by variations in topography and land cover within the SAYR.

Glacier retreat and associated sediment dynamics in proglacial areas: a case study from the Silvretta Alps, Austria

NASA Astrophysics Data System (ADS)

Felbauer, Lucia; Pöppl, Ronald

2016-04-01

Global warming results in an ongoing retreat of glaciers in the Alps, leaving behind large amounts of easily erodible sediments. In addition, the debuttressing of rock-walls and the decay of permafrost in the high mountain regions facilitates mass movements of potential disastrous consequences, such as rock falls, landslides and debris flows. Therefore, it is highly important to quantify the amount of sediments that are supplied from the different compartments and to investigate how glacial retreat influences sediment dynamics in proglacial areas. In the presented work glacier retreat and associated sediment dynamics were investigated in the Kromer valley (Silvretta Alps, Austria) by analyzing remote sensing data. Glacial retreat from the period of 1950 to 2012 was documented by interpreting aerial photographs. By digitizing the different stages of the glaciers for six time frames, changes in glacier area and length were mapped and quantified. In order to identify, characterize and quantify sediment dynamics in the proglacial areas a high resolution DEM of difference (DoD) between 2007 and 2012 was created and analyzed, further differentiating between different zones (e.g. valley bottom, hillslope) and types of geomorphic processes (e.g. fluvial, gravitational). First results will be presented at the EGU General Assembly 2016.

Middle and Late Pleistocene glaciations in the southwestern Pamir and their effects on topography

USGS Publications Warehouse

Stubner, Konstanze; Grin, Elena; Hidy, Alan J.; Schaller, Mirjam; Gold, Ryan D.; Ratschbacher, Lothar; Ehlers, Todd

2017-01-01

Glacial chronologies provide insight into the evolution of paleo-landscapes, paleoclimate, topography, and the erosion processes that shape mountain ranges. In the Pamir of Central Asia, glacial morphologies and deposits indicate extensive past glaciations, whose timing and extent remain poorly constrained. Geomorphic data and 15 new 10Be exposure ages from moraine boulders and roches moutonnées in the southwestern Pamir document multiple Pleistocene glacial stages. The oldest exposure ages, , underestimate the age of the earliest preserved glacial advance and imply that the modern relief of the southwestern Pamir (peaks at ∼5000–6000 m a.s.l.; valleys at ∼2000–3000 m a.s.l.) already existed in the late Middle Pleistocene. Younger exposure ages (∼40–80 ka, ∼30 ka) complement the existing Central Asian glacial chronology and reflect successively less extensive Late Pleistocene glaciations. The topography of the Pamir and the glacial chronologies suggest that, in the Middle Pleistocene, an ice cap or ice field occupied the eastern Pamir high-altitude plateau, whereas westward flowing valley glaciers incised the southwestern Pamir. Since the Late Pleistocene deglaciation, the rivers of the southwestern Pamir adjusted to the glacially shaped landscape. Localized rapid fluvial incision and drainage network reorganization reflect the transient nature of the deglaciated landscape.

The demographic response of bank-dwelling beavers to flow regulation: A comparison on the Green and Yampa rivers

USGS Publications Warehouse

Breck, S.W.; Wilson, K.R.; Andersen, D.C.

2001-01-01

We assessed the effects of flow regulation on the demography of beavers (Castor canadensis) by comparing the density, home-range size, and body size of bank-dwelling beavers on two sixth-order alluvial river systems, the flow-regulated Green River and the free-flowing Yampa River, from 1997 to 2000. Flow regulation on the Green River has altered fluvial geomorphic processes, influencing the availability of willow and cottonwood, which, in turn, has influenced the demography of beavers. Beaver density was higher on the Green River (0.5–0.6 colonies per kilometre of river) than on the Yampa River (0.35 colonies per kilometre of river). Adult and subadult beavers on the Green River were in better condition, as indicated by larger body mass and tail size. There was no detectable difference in home-range size, though there were areas on the Yampa River that no beavers used. We attribute the improved habitat quality on the Green River to a greater availability of willow. We suggest that the sandy flats and sandbars that form during base flows and the ice cover that forms over winter on the Yampa River increase the energy expended by the beavers to obtain food and increase predation risk and thus lowers the availability of woody forage.

Establishment area and biogeomorphic feedback window of three pioneer riparian Salicaceae species within a dynamic riparian corridor (Allier River, France)

NASA Astrophysics Data System (ADS)

Hortobágyi, Borbála; Corenblit, Dov; Steiger, Johannes; Peiry, Jean-Luc

2017-04-01

Within riparian corridors, biotic-abiotic feedback mechanisms occur between woody vegetation which is highly influenced by hydrogeomorphic constraints (e.g. sediment transport and deposition, shear stress, hydrological variability), fluvial landforms and morphodynamics, which in turn are modulated by established vegetation. During field investigations in spring 2015 we analysed on 16 alluvial bars (e.g. point and lateral bars) within the dynamic riparian corridor of the Allier River, France, the aptitude of three pioneer riparian Salicaceae tree species (Populus nigra L., Salix purpurea L. and Salix alba L.) to establish and to act as ecosystem engineers by trapping sediment and constructing fluvial landforms. Our aim was to empirically identify the preferential establishment area (EA; i.e. the local areas where species establish) and the preferential biogeomorphic feedback window (BFW; i.e. where and to what extent the species affect geomorphology) of these three species on alluvial bars within a river reach of a length of 20 km. Our results show that the EA and BFW of all three species significantly varied along the longitudinal, i.e. upstream-downstream exposure on the alluvial bars, and the transverse gradient, i.e. main channel-floodplain gradient of hydrological connectivity. In the current context of the Allier River it appeared that P. nigra, which is the most abundant species, acts as the main engineer species affecting landform dynamics at the bar scale; S. purpurea establishes and acts as an ecosystem engineer in the locations on the alluvial bars which are the most exposed to hydrosedimentary flow dynamics, while S. alba establishes on the bar tail in the vicinity of secondary channels and affects geomorphology in mixed patches with P. nigra. Thus, our study underlines the role of functional trait diversity of riparian engineer species in controlling the extent of fluvial landform construction along geomorphic gradients within riparian corridors exposed to frequent hydrogeomorphic disturbances.

Niche construction within riparian corridors. Part I: Exploring biogeomorphic feedback windows of three pioneer riparian species (Allier River, France)

NASA Astrophysics Data System (ADS)

Hortobágyi, Borbála; Corenblit, Dov; Steiger, Johannes; Peiry, Jean-Luc

2018-03-01

Within riparian corridors, biotic-abiotic feedback mechanisms occur between woody vegetation strongly influenced by hydrogeomorphic constraints (e.g., sediment transport and deposition, shear stress, hydrological variability), fluvial landforms, and morphodynamics, which in turn are modulated by the established vegetation. During field investigations in spring 2015, we studied 16 alluvial bars (e.g., point and lateral bars) within the dynamic riparian corridor of the Allier River (France) to assess the aptitude of three pioneer riparian Salicaceae species (Populus nigra L., Salix purpurea L., and Salix alba L.) to establish and act as ecosystem engineers by trapping sediment and constructing fluvial landforms. Our aim is to empirically identify the preferential establishment area (EA; i.e., the local areas where species become established) and the preferential biogeomorphic feedback window (BFW; i.e., where and to what extent the species and geomorphology interact) of these three species on alluvial bars within a 20-km-long river reach. Our results show that the EA and BFW of all three species vary significantly along the longitudinal profile, i.e., upstream-downstream exposure on the alluvial bars, as well as transversally, i.e., the main hydrological connectivity gradient from the river channel toward the floodplain. In the present-day context of the Allier River, P. nigra is the most abundant species, appearing to act as the main engineer species affecting landform dynamics at the bar scale; S. purpurea is established and acts as an ecosystem engineer at locations on alluvial bars that are most exposed to hydrosedimentary flow dynamics, while S. alba is established on the bar tail close to secondary channels and affects the geomorphology in mixed patches along with P. nigra. Our study highlights the role of functional trait diversity of riparian engineer species in controlling the extent of fluvial landform construction along geomorphic gradients within riparian corridors exposed to frequent hydrogeomorphic disturbances.

Glaciolacustrine deposits formed in an ice-dammed tributary valley in the south-central Pyrenees: New evidence for late Pleistocene climate

NASA Astrophysics Data System (ADS)

Sancho, Carlos; Arenas, Concha; Pardo, Gonzalo; Peña-Monné, José Luis; Rhodes, Edward J.; Bartolomé, Miguel; García-Ruiz, José M.; Martí-Bono, Carlos

2018-04-01

Combined geomorphic features, stratigraphic characteristics and sedimentologic interpretation, coupled with optically stimulated luminescence (OSL) dates, of a glacio-fluvio-lacustrine sequence (Linás de Broto, northern Spain) provide new information to understand the palaeoenvironmental significance of dynamics of glacier systems in the south-central Pyrenees during the Last Glacial Cycle (≈130 ka to 14 ka). The Linás de Broto depositional system consisted of a proglacial lake fed primarily by meltwater streams emanating from the small Sorrosal glacier and dammed by a lateral moraine of the Ara trunk glacier. The resulting glacio-fluvio-lacustrine sequence, around 55 m thick, is divided into five lithological units consisting of braided fluvial (gravel deposits), lake margin (gravel and sand deltaic deposits) and distal lake (silt and clay laminites) facies associations. Evolution of the depositional environment reflects three phases of progradation of a high-energy braided fluvial system separated by two phases of rapid expansion of the lake. Fluvial progradation occurred during short periods of ice melting. Lake expansion concurred with ice-dam growth of the trunk glacier. The first lake expansion occurred over a time range between 55 ± 9 ka and 49 ± 11 ka, and is consistent with the age of the Viu lateral moraine (49 ± 8 ka), which marks the maximum areal extent of the Ara glacier during the Last Glacial Cycle. These dates confirm that the maximum areal extent of the glacier occurred during Marine Isotope Stages 4 and 3 in the south-central Pyrenees, thus before the Last Glacial Maximum. The evolution of the Linás de Broto depositional system during this maximum glacier extent was modulated by climate oscillations in the northern Iberian Peninsula, probably related to latitudinal shifts of the atmospheric circulation in the southern North-Atlantic Ocean, and variations in summer insolation intensity.

Quantifying Late Quaternary Deformation along the Santa Ynez River, Santa Maria Basin, California

NASA Astrophysics Data System (ADS)

Slatten, C. L.; Onderdonk, N.

2017-12-01

The fault bounded Santa Maria Basin, located on the Central Coast of California, is positioned in an area of convergence between the rotating Western Transverse Ranges and the non-rotated Southern Coast Ranges. The Santa Ynez River Fault (SYRF) is an east-west trending fault that parallels the Santa Ynez River west of Lake Cachuma, California and defines the southern structural boundary of the Santa Maria Basin. However, the rate and style of Late Quaternary deformation and uplift in this region and the potential for seismic hazard along the fault is lacking. Fluvial terraces are key geomorphological components of fluvial systems that can be used to provide insights into regional and local uplift and deformation. The Santa Ynez River delineates the northern edge of the Santa Ynez Mountains and flows west through the Santa Ynez Valley to its mouth at the Pacific Ocean. The Santa Ynez River Field Area is a 10 km stretch of the Santa Ynez River just west of Lake Cachuma where terraces are well developed and the SYRF cuts through terraces and the active river (Figure 1). If there has been Quaternary movement of the SYRF we expect to find deformation in these areas. An initial survey of the area identified five terrace levels ranging from 8 m to 135 m above modern river level. The fluvial terraces are being mapped as separate units, surveyed for deformation with GPS based transects, and sampled for optically stimulated luminescence (OSL) dating. These combined methods will allow us to document the geomorphic characteristics and landform evolution of the lower Santa Ynez River, evaluate the possibility of Late Quaternary activity of the SYRF, and determine the rate of Late Quaternary regional uplift along the western Santa Ynez River in the Santa Maria Basin providing a possible basis for augmentation of the seismic hazards for Santa Barbara County.

Formation of outflow channels on Mars: Testing the origin of Reull Vallis in Hesperia Planum by large-scale lava-ice interactions and top-down melting

NASA Astrophysics Data System (ADS)

Cassanelli, James P.; Head, James W.

2018-05-01

The Reull Vallis outflow channel is a segmented system of fluvial valleys which originates from the volcanic plains of the Hesperia Planum region of Mars. Explanation of the formation of the Reull Vallis outflow channel by canonical catastrophic groundwater release models faces difficulties with generating sufficient hydraulic head, requiring unreasonably high aquifer permeability, and from limited recharge sources. Recent work has proposed that large-scale lava-ice interactions could serve as an alternative mechanism for outflow channel formation on the basis of predictions of regional ice sheet formation in areas that also underwent extensive contemporaneous volcanic resurfacing. Here we assess in detail the potential formation of outflow channels by large-scale lava-ice interactions through an applied case study of the Reull Vallis outflow channel system, selected for its close association with the effusive volcanic plains of the Hesperia Planum region. We first review the geomorphology of the Reull Vallis system to outline criteria that must be met by the proposed formation mechanism. We then assess local and regional lava heating and loading conditions and generate model predictions for the formation of Reull Vallis to test against the outlined geomorphic criteria. We find that successive events of large-scale lava-ice interactions that melt ice deposits, which then undergo re-deposition due to climatic mechanisms, best explains the observed geomorphic criteria, offering improvements over previously proposed formation models, particularly in the ability to supply adequate volumes of water.

Palaeoflood evidence on the River Nore, South East Ireland

NASA Astrophysics Data System (ADS)

Fleming, Ciara; Turner, Jonathan; Bourke, Mary

2017-04-01

Past geomorphic changes can be detected in sediment sinks, through the investigation of natural sediment archives. Since the advent of palaeoflood hydrology in the 1980s, numerous authors have demonstrated that such sediment deposits record valuable evidence of past flooding events. Many of these studies have focussed on fluvial systems in arid environments, with bedrock channels proving to be particularly successful field sites. In some districts, the collected datasets are now routinely employed to augment analyses of flood frequency and magnitude, which have traditionally relied on extrapolation of short hydrometric datasets. This study targets river reaches in a temperate humid environment, with a predominantly alluvial channel. The River Nore is one of the largest catchments draining South East Ireland. It is situated in a valley with an inherited glacial legacy and is principally a lowland river catchment. Specific morphological zones have been targeted which are optimal for flood deposit preservation, including palaeochannels, tributary junctions and floodplain overbank settings.There are a variety of anthropogenic pressures evident in this landscape. Among them are channelisation of select tributaries, a legacy of coal mining in the upland Carboniferous limestones, and the installation of man-made obstacles or modifications along the length of the river channel such as sluices and weirs. Regarding land-use, the majority of the catchment is dominated by agriculture, mainly pasture with some tillage. This study investigates palaeoflood evidence in the River Nore catchment and examines the development of the river floodplain using a variety of complementary field and desk-based methods. The sub-surface and micro-topography of river reaches are investigated using Ground Penetrating Radar (GPR) and Unmanned Aerial Vehicle (UAV) technology. Flood deposits have been characterised by examination of bank exposures and sediment cores. Installation of sediment traps at discrete locations will enable quantification of sedimentation rates of individual flood events over the winter period 2016/17. Historical Ordnance Survey maps, aerial and satellite imagery have been digitised in a GIS (Geographic Information System) to document channel change over time. Previous authors have noted a paucity of research in fluvial geomorphology in Ireland, particularly in lowland catchments, and this study endeavours to start addressing that gap. Furthermore, in terms of developments in palaeoflood hydrology, this is the first study of its kind in Ireland, attempting to understand and utilise geomorphic evidence of previous flood events in an Irish river catchment.

Paleo ice-cap surfaces and extents

NASA Astrophysics Data System (ADS)

Gillespie, A.; Pieri, D.

2008-12-01

The distribution, equilibrium-line altitude (ELA) and timing of Pleistocene alpine glaciers are used to constrain paleoclimatic reconstructions. Attention has largely focused on the geomorphic evidence for the former presence of simple valley glaciers; paleo alpine ice caps and their outlet glaciers have proven to be more problematical. This is especially so in the remote continental interior of Asia, where the research invested in the Alps or Rocky Mountains has yet to be duplicated. Even the putative existence and size of paleo ice caps in Tibet and the Kyrgyz Tien Shan is controversial. Remote sensing offers the opportunity to assess vast tracts of land quickly, with images and co-registered digital elevation models (DEMs) offering the most information for studies of paleoglaciers. We pose several questions: (1) With what confidence can nunataks be identified remotely? (2) What insights do their physiographic characteristics offer? (3) What characteristics of the bed of a paleo ice cap can be used to identify its former presence remotely? and (4) Can the geomorphic signatures of the edges of paleo ice caps be recognized and mapped? Reconstruction of the top surface of a paleo ice cap depends on the recognition of nunataks, typically rougher at 1 m to 100 m scales than their surroundings. Nunataks in southern Siberia are commonly notched by multiple sub- horizontal bedrock terraces. These step terraces appear to originate from freeze-thaw action on the rock-ice interface during periods of stability, and presence of multiple terraces suggests stepwise lowering of ice surfaces during deglaciation. An older generation of step-terraced nunataks, distinguished by degraded and eroded terraces, delineates a larger paleo ice cap in the Sayan Range (Siberian - Mongolian border) that significantly pre-dates the last glacial maximum (LGM). Large ice caps can experience pressure melting at their base and can manifest ice streams within the ice cap. Valleys left behind differ from fluvial valleys in their width/depth profiles: the channels maintain width but get shallower near their sources. Link junction angle distributions within superimposed drainage networks are broader and distinct from those of evolved fluvial networks, and their character and statistics can be used to identify the perimeters of large paleo ice caps. (This work was carried out in part at the Jet Propulsion Laboratory of the California Institute of Technology under contract to NASA.)

How Do River Meanders Change with Sea Level Rise and Fall?

NASA Astrophysics Data System (ADS)

Scamardo, J. E.; Kim, W.

2016-12-01

River meander patterns are controlled by numerous factors, including variations in water discharge, sediment input, and base level. However, the effect of sea level rise and fall on meandering rivers has not been thoroughly quantified. This study examines geomorphic changes to meandering rivers as a result of sea level rise and fall. Twenty experimental runs using coarse-grained walnut shell sediment (D50= 500 microns) in a flume tank (2.4m x 0.6m x 0.1m) tested the optimal initial conditions for creating meandering rivers in a laboratory setting as well as variations in base level rise and fall rates. Geomorphic changes were recorded by camera images every 20 seconds for a duration of 4 hours per experiment. Seventeen experiments tested the effects of changes in initial base levels, water discharge between 200 and 400 mL/min, and sediment to water input ratios between 1:1000 and 1:250 while measuring sinuosity, channel geometry, and the timescale of the channel to reach a stable form. Sinuosity and channel activity increased with increasing water discharge, initial base level, and the sediment to water ratio to a point after which the activity decreased with increasing sediment input. Base-level change experiments used initial conditions of 400 mL/min, a 1:750 sediment to water input ratio, and a 6 cm initial base-level to induce river meanders for the initial 2 hours before base-level change occurred. Three separate experiments investigated the effects of increasing rates of sea level change: 0.07 cm/min, 0.1 cm/min, and 0.2 cm/min. Experimental sea level was decreased constantly from a high-stand of 6 cm to a low-stand of 2 cm back to the high-stand base-level in each experiment. The rates of change in the experiments scale roughly from central to glacial cycles. In all three experiments, sea level fall induced meander cut-off while sea level rise prompted greater rates of meander bend erosion and meander growth. Sinuosity increased by 12%, 13.5%, and 24%, respectively in the three experiments, with most sinuosity changes occurring in the downstream reach of the channel. These experiments could provide insight into long term effects of sea level change on modern meandering fluvial systems as well as provide a key to interpreting past fluvial changes in the stratigraphic record.

Tracking geomorphic signatures of watershed suburbanization with multi-temporal LiDAR

USGS Publications Warehouse

Jones, Daniel K.; Baker, Matthew E.; Miller, Andrew J.; Jarnagin, S. Taylor; Hogan, Dianna M.

2014-01-01

Urban development practices redistribute surface materials through filling, grading, and terracing, causing drastic changes to the geomorphic organization of the landscape. Many studies document the hydrologic, biologic, or geomorphic consequences of urbanization using space-for-time comparisons of disparate urban and rural landscapes. However, no previous studies have documented geomorphic changes from development using multiple dates of high-resolution topographic data at the watershed scale. This study utilized a time series of five sequential light detection and ranging (LiDAR) derived digital elevation models (DEMs) to track watershed geomorphic changes within two watersheds throughout development (2002–2008) and across multiple spatial scales (0.01–1 km2). Development-induced changes were compared against an undeveloped forested watershed during the same time period. Changes in elevations, slopes, hypsometry, and surface flow pathways were tracked throughout the development process to assess watershed geomorphic alterations. Results suggest that development produced an increase in sharp topographic breaks between relatively flat surfaces and steep slopes, replacing smoothly varying hillslopes and leading to greater variation in slopes. Examinations of flowpath distributions highlight systematic modifications that favor rapid convergence in unchanneled upland areas. Evidence of channel additions in the form of engineered surface conduits is apparent in comparisons of pre- and post-development stream maps. These results suggest that topographic modification, in addition to impervious surfaces, contributes to altered hydrologic dynamics observed in urban systems. This work highlights important considerations for the use of repeat LiDAR flights in analyzing watershed change through time. Novel methods introduced here may allow improved understanding and targeted mitigation of the processes driving geomorphic changes during development and help guide future research directions for development-based watershed studies.

Engineered channel controls limiting spawning habitat rehabilitation success on regulated gravel-bed rivers

NASA Astrophysics Data System (ADS)

Brown, Rocko A.; Pasternack, Gregory B.

2008-05-01

In efforts to rehabilitate regulated rivers for ecological benefits, the flow regime has been one of the primary focal points of management strategies. However, channel engineering can impact channel geometry such that hydraulic and geomorphic responses to flow reregulation do not yield the sought for benefits. To illustrate and assess the impacts of structural channel controls and flow reregulation on channel processes and fish habitat quality in multiple life stages, a highly detailed digital elevation model was collected and analyzed for a river reach right below a dam using a suite of hydrologic, hydraulic, geomorphic, and ecological methods. Results showed that, despite flow reregulation to produce a scaled-down natural hydrograph, anthropogenic boundary controls have severely altered geomorphic processes associated with geomorphic self-sustainability and instream habitat availability in the case study. Given the similarity of this stream to many others, we concluded that the potential utility of natural flow regime reinstatement in regulated gravel-bed rivers is conditional on concomitant channel rehabilitation.

Coastal system mapping: a new approach to formalising and conceptualising the connectivity of large-scale coastal systems

NASA Astrophysics Data System (ADS)

French, J.; Burningham, H.; Whitehouse, R.

2010-12-01

The concept of the coastal sediment cell has proved invaluable as a basis for estimating sediment budgets and as a framework for coastal management. However, whilst coastal sediment cells are readily identified on compartmentalised coastlines dominated by beach-grade material, the cell concept is less suited to handling broader linkages between estuarine, coastal and offshore systems, and for incorporating longer-range suspended sediment transport. We present a new approach to the conceptualisation of large-scale coastal geomorphic systems based on a hierarchical classification of component landforms and management interventions and mapping of the interactions between them. Coastal system mapping is founded on a classification that identifies high-level landform features, low-level landform elements and engineering interventions. Geomorphic features define the large-scale organisation of a system and include landforms that define gross coastal configuration (e.g. headland, bay) as well as fluvial, estuarine and offshore sub-systems that exchange sediment with and influence the open coast. Detailed system structure is mapped out with reference to a larger set of geomorphic elements (e.g. cliff, dune, beach ridge). Element-element interactions define cross-shore linkages (conceptualised as hinterland, backshore and foreshore zones) and alongshore system structure. Both structural and non-structural engineering interventions are also represented at this level. Element-level mapping is rationalised to represent alongshore variation using as few elements as possible. System linkages include both sediment transfer pathways and influences not associated with direct mass transfer (e.g. effect of a jetty at an inlet). A formal procedure for capturing and graphically representing coastal system structure has been developed around free concept mapping software, CmapTools (http://cmap.ihmc.us). Appended meta-data allow geographic coordinates, data, images and literature pertaining to specific locations to be embedded in system maps. Exported maps can be analysed separately to quantify abundance of system components and their scales of interaction. Our approach is demonstrated for different scales and geomorphic contexts in the UK, including Alnmouth Bay (NE England; 15km), Lowestoft to Felixstowe (E England; 73km) and Cardigan Bay (Wales; 267km). Aerial imagery provides the primary basis for identifying features and elements and likely modes of interaction. This interpretation is then checked against relevant research literature and site data. Coastal system mapping is a kind of knowledge formalisation that generalises disparate sources of information (‘plain data’) into usable knowledge. Consensus-derived system maps are highly effective as a catalyst for structured discussion of geomorphic system behaviour and its implications for coastal management. They also function as a repository for results from quantitative analyses and modelling.

Soil-geomorphic significance of land surface characteristics in an arid mountain range, Mojave Desert, USA

USGS Publications Warehouse

Hirmas, D.R.; Graham, R.C.; Kendrick, K.J.

2011-01-01

Mountains comprise an extensive and visually prominent portion of the landscape in the Mojave Desert, California. Landform surface properties influence the role these mountains have in geomorphic processes such as dust flux and surface hydrology across the region. The primary goal of this study was to describe and quantify land surface properties of arid-mountain landforms as a step toward unraveling the role these properties have in soil-geomorphic processes. As part of a larger soil-geomorphic study, four major landform types were identified within the southern Fry Mountains in the southwestern Mojave Desert on the basis of topography and landscape position: mountaintop, mountainflank, mountainflat (intra-range low-relief surface), and mountainbase. A suite of rock, vegetation, and morphometric land surface characteristic variables was measured at each of 65 locations across the study area, which included an associated piedmont and playa. Our findings show that despite the variation within types, landforms have distinct land surface properties that likely control soil-geomorphic processes. We hypothesize that surface expression influences a feedback process at this site where water transports sediment to low lying areas on the landscape and wind carries dust and soluble salts to the mountains where they are washed between rocks, incorporated into the soil, and retained as relatively long-term storage. Recent land-based video and satellite photographs of the dust cloud emanating from the Sierra Cucapá Mountains in response to the 7.2-magnitude earthquake near Mexicali, Mexico, support the hypothesis that these landforms are massive repositories of dust.

Spatial analysis of the impacts of the Chaitén volcano eruption (Chile) in three fluvial systems

NASA Astrophysics Data System (ADS)

Ulloa, H.; Iroumé, A.; Picco, L.; Mohr, C. H.; Mazzorana, B.; Lenzi, M. A.; Mao, L.

2016-08-01

The eruption of the Chaitén volcano in May 2008 generated morphological and ecological disturbances in adjacent river basins, and the magnitude of these disturbances depended on the type of dominant volcanic process affecting each of them. The aim of this study is to analyse the morphological changes in different periods in river segments of the Blanco, El Amarillo and Rayas river basins located near the Chaitén volcano. These basins suffered disturbances of different intensity and spatial distribution caused by tephra fall, dome collapses and pyroclastic density currents that damaged hillslope forests, widened channels and destroyed island and floodplain vegetation. Changes continued to occur in the fluvial systems in the years following the eruption, as a consequence of the geomorphic processes indirectly induced by the eruption. Channel changes were analyzed by comparing remote images of pre and post-eruption conditions. Two periods were considered: the first from 2008 to 2009-2010 associated with the explosive and effusive phases of the eruption and the second that correspond to the post-eruption stage from 2009-2010 to 2013. Following the first phases channel segments widened 91% (38 m/yr), 6% (7 m/yr) and 7% (22 m/yr) for Blanco, Rayas and El Amarillo Rivers, respectively, compared to pre-eruption condition. In the second period, channel segments additionally widened 42% (8 m/yr), 2% (2 m/yr) and 5% (4 m/yr) for Blanco, Rayas and El Amarillo Rivers, respectively. In the Blanco River 62 and 82% of the islands disappeared in the first and second period, respectively, which is 6-8 times higher than in the El Amarillo approximately twice the Rayas. Sinuosity increased after the eruption only in the Blanco River but the three study channels showed a high braiding intensity mainly during the first post-eruption period. The major disturbances occurred during the eruptive and effusive phases of Chaitén volcano, and the intensity of these disturbances reflects the magnitude of the dominant volcanic processes affecting each basin. Inputs of sediment from dome collapses and pyroclastic density currents and not ash fall seem to explain morphologic channel change magnitudes in the study segments. The resulting knowledge can facilitate land use planning and design of river restoration projects in areas affected by volcanic eruptions disturbances.

Integrated stratigraphy of Paleocene lignite seams of the fluvial Tullock Formation, Montana (USA).

NASA Astrophysics Data System (ADS)

Noorbergen, Lars J.; Kuiper, Klaudia F.; Hilgen, Frederik J.; Krijgsman, Wout; Dekkers, Mark J.; Smit, Jan; Abels, Hemmo A.

2015-04-01

Coal-bearing fluvial sedimentation is generally thought to be dominated by autogenic processes that are processes intrinsic to the sedimentary system. Ongoing research however suggests that several fluvial processes such as floodplain inundation and avulsion, can also be controlled by external forcing such as orbital climate change. Still, the exact role of orbital climate forcing in fluvial sediments is difficult to decipher since riverine deposits are complicated by variable sedimentation rates including erosion of previously deposited material, by lateral heterogeneity of sedimentation, and by scarcity of independent dating methods. The early Paleocene lignite-bearing Tullock Formation of the Williston Basin in eastern Montana represents a record of fluvial sedimentation that is perfectly exposed and, displays a seemingly regular alternation of sandstones and lignite seams. These coal beds contain multiple volcanic ash layers. Here, we use an integrated stratigraphic approach (litho- and magnetostratigraphy, geochemical fingerprinting and radio-isotope dating of volcanic ash layers) to establish a high-resolution time frame for the early Paleocene fluvial sediments. First age estimations indicate that the Tullock Formation in Eastern Montana was deposited over a time span of ~ 1000 kyr subsequent to the Cretaceous - Paleogene boundary, dated at ~ 65.95 Ma [1]. Initial high-resolution magnetostratigraphy revealed the occurrence of the C29r/C29n polarity reversal which was stratigraphic consistent at different field locations. We investigate the regional significance of sedimentary change at multiple sites of the same age in order to provide improved insight on the role of orbital forcing in fluvial coal formation. References: [1] Kuiper, K.F., Deino, A., Hilgen, F.J., Krijgsman, W., Renne, P.R., Wijbrans, J.R. (2008). Synchronizing Rock Clocks of Earth History. Science 320, 500-504.

Two decades of numerical modelling to understand long term fluvial archives: Advances and future perspectives

NASA Astrophysics Data System (ADS)

Veldkamp, A.; Baartman, J. E. M.; Coulthard, T. J.; Maddy, D.; Schoorl, J. M.; Storms, J. E. A.; Temme, A. J. A. M.; van Balen, R.; van De Wiel, M. J.; van Gorp, W.; Viveen, W.; Westaway, R.; Whittaker, A. C.

2017-06-01

The development and application of numerical models to investigate fluvial sedimentary archives has increased during the last decades resulting in a sustained growth in the number of scientific publications with keywords, 'fluvial models', 'fluvial process models' and 'fluvial numerical models'. In this context we compile and review the current contributions of numerical modelling to the understanding of fluvial archives. In particular, recent advances, current limitations, previous unexpected results and future perspectives are all discussed. Numerical modelling efforts have demonstrated that fluvial systems can display non-linear behaviour with often unexpected dynamics causing significant delay, amplification, attenuation or blurring of externally controlled signals in their simulated record. Numerical simulations have also demonstrated that fluvial records can be generated by intrinsic dynamics without any change in external controls. Many other model applications demonstrate that fluvial archives, specifically of large fluvial systems, can be convincingly simulated as a function of the interplay of (palaeo) landscape properties and extrinsic climate, base level and crustal controls. All discussed models can, after some calibration, produce believable matches with real world systems suggesting that equifinality - where a given end state can be reached through many different pathways starting from different initial conditions and physical assumptions - plays an important role in fluvial records and their modelling. The overall future challenge lies in the development of new methodologies for a more independent validation of system dynamics and research strategies that allow the separation of intrinsic and extrinsic record signals using combined fieldwork and modelling.

Coupled Landscape and Channel Dynamics in the Ganges-Brahmaputra Tidal Deltaplain, Southwest Bangladesh

NASA Astrophysics Data System (ADS)

Bomer, J.; Wilson, C.; Hale, R. P.

2017-12-01

In the Ganges-Brahmaputra Delta (GBD) and other tide-dominated systems, periodic flooding of the land surface during the tidal cycle promotes sediment accretion and surface elevation gain over time. However, over the past several decades, anthropogenic modification of the GBD tidal deltaplain through embankment construction has precluded sediment delivery to catchment areas, leading to widespread channel siltation and subsidence in poldered landscapes. Amongst the current discussion on GBD sustainability, the relationship between tidal inundation period and resultant sedimentation in natural and embanked settings remains unclear. Moreover, an evaluation of how riparian sedimentology and stratigraphic architecture changes across the GBD tidal-fluvial spectrum is notably absent, despite its critical importance in assessing geomorphic change in human-impacted transitional environments. To provide local-scale, longitudinal trends of coupled landscape-channel dynamics, an array of surface elevation tables, groundwater piezometers, and sediment traps deployed in natural and embanked settings have been monitored seasonally over a time span of 4 years. This knowledge base will be extended across the GBD tidal-fluvial transition by collecting sediment cores from carefully selected point bars along the Gorai River. Sediments will be analyzed for lithologic, biostratigraphic, and geochemical properties to provide an integrated framework for discerning depositional zones and associated facies assemblages across this complex transitional environment. Preliminary comparisons of accretion and hydroperiod data suggest that inundation duration strongly governs mass accumulation on the intertidal platform, though other factors such as mass extraction from sediment source and vegetation density may play secondary roles.

Solar radiation as a global driver of hillslope asymmetry: Insights from an ecogeomorphic landscape evolution model

NASA Astrophysics Data System (ADS)

Yetemen, Omer; Istanbulluoglu, Erkan; Duvall, Alison R.

2015-12-01

Observations at the field, catchment, and continental scales across a range of arid and semiarid climates and latitudes reveal aspect-controlled patterns in soil properties, vegetation types, ecohydrologic fluxes, and hillslope morphology. Although the global distribution of solar radiation on earth's surface and its implications on vegetation dynamics are well documented, we know little about how variation of solar radiation across latitudes influence landscape evolution and resulting geomorphic difference. Here, we used a landscape evolution model that couples the continuity equations for water, sediment, and aboveground vegetation biomass at each model element in order to explore the controls of latitude and mean annual precipitation (MAP) on the development of hillslope asymmetry (HA). In our model, asymmetric hillslopes emerged from the competition between soil creep and vegetation-modulated fluvial transport, driven by spatial distribution of solar radiation. Latitude was a primary driver of HA because of its effects on the global distribution of solar radiation. In the Northern Hemisphere, north-facing slopes (NFS), which support more vegetation cover and have lower transport efficiency, get steeper toward the North Pole while south-facing slopes (SFS) get gentler. In the Southern Hemisphere, the patterns are reversed and SFS get steeper toward the South Pole. For any given latitude, MAP is found to have minor control on HA. Our results underscore the potential influence of solar radiation as a global control on the development of asymmetric hillslopes in fluvial landscapes.

Palaeoseismological evidence for the 1570 Ferrara earthquake, Italy

NASA Astrophysics Data System (ADS)

Caputo, R.; Poli, M. E.; Minarelli, L.; Rapti, D.; Sboras, S.; Stefani, M.; Zanferrari, A.

2016-06-01

In May 2012, two earthquakes (Mw 6.1 and 5.9) affected the Po Plain, Italy. The strongest shock produced extensive secondary effects associated with liquefaction phenomena. Few weeks after the earthquakes, an exploratory trench was excavated across a levee of the palaeo-Reno reach, where a system of aligned ground ruptures was observed. The investigated site well preserves the geomorphic expression of a fluvial body that mainly formed in the fifteenth to sixteenth centuries as historical sources and radiometric data testify. In the trench several features pinpointed the occurrence of past liquefaction events: (i) dikes filled with overpressured injected sand and associated with vertical displacements have no correspondence with the fractures mapped at the surface; (ii) thick dikes are buried by the plowed level or even by fluvial deposits; (iii) although some of the 2012 ground fractures characterized by vertical displacement and opening occurred in correspondence of thick dikes observed in the trench, sand and water ejection did not occur; (iv) some seismites (load casts) were observed in the trench well above the 2012 water level. The results strongly suggest that shaking has locally occurred in the past producing a sufficient ground motion capable of triggering liquefaction phenomena prior to, and likely stronger than, the May 2012 earthquake. Historical seismicity documents three seismic events that might have been able to generate liquefaction in the broader investigated area. Based on the analysis of their macroseismic fields, the 17 November 1570 Ferrara earthquake is the most likely causative event of the observed palaeoliquefactions.

Process regime, salinity, morphological, and sedimentary trends along the fluvial to marine transition zone of the mixed-energy Mekong River delta, Vietnam

NASA Astrophysics Data System (ADS)

Gugliotta, Marcello; Saito, Yoshiki; Nguyen, Van Lap; Ta, Thi Kim Oanh; Nakashima, Rei; Tamura, Toru; Uehara, Katsuto; Katsuki, Kota; Yamamoto, Seiichiro

2017-09-01

The fluvial to marine transition zone (FMTZ) is the area of coastal rivers in which sedimentation is controlled by the interaction of fluvial and marine processes. This study examines the FMTZ of the Mekong River delta, along a total channel length of 660 km. Methods consist of collection and analysis of channel bed sediment samples, measurements of channel morphological parameters, and recognition of mangrove, molluscan, and diatom species. The process regime, salinity, morphological, and sedimentary trends recognized were used to define two main tracts for this FMTZ: an upstream, fluvial-dominated tract and a downstream, tide-dominated tract. In more detail, they allow the identification of four subzones, from upstream to downstream: 1) fluvial-dominated, tide-affected; 2) fluvial-dominated, tide-influenced; 3) tide-dominated, fluvial-influenced; and 4) tide-dominated, fluvial-affected. Tide-induced water-level changes affect the entire study area and extend into Cambodia. Measured salinity intrusion extends 15 km upstream of the river mouth during wet season, and 50 km during dry season. Brackish water species of mangroves, mollusks, and diatoms, however, occur landward of these limits, suggesting that highly diluted brackish water may reach 160 km upstream of the river mouth during the dry season. In the fluvial-dominated tract, channels are sinuous and show a seaward-deepening trend, whereas width is relatively constant. In the tide-dominated tract, channels are straight, and show seaward-widening and seaward-shallowing trends. Natural levees are present in the fluvial-dominated, tide-affected subzone, but are replaced by mangroves elsewhere along the FMTZ. In the fluvial-dominated tract, mud content is low, sand grain size fines seaward, and gravelly sand and sand are the dominant facies. In the tide-dominated tract, mud content is high, sand grain size is constant, recycled sand is common, and tidal rhythmites are the dominant facies. Mud pebbles are common in sediments throughout a large part of the FMTZ. These trends characterizing the FMTZ of the Mekong River delta seem to be present in other systems and likely represent a general FMTZ pattern. Nonetheless, minor differences may be observed between different types of systems, or because of differences in local conditions. The comprehensive description of trends and their mutual relationships along the FMTZ presented herein provides critical information that can form the basis of a general conceptual model and can help to better understand these complex zones.

Geomorphic Classification and Assessment of Channel Dynamics in the Missouri National Recreational River, South Dakota and Nebraska

USGS Publications Warehouse

Elliott, Caroline M.; Jacobson, Robert B.

2006-01-01

A multiscale geomorphic classification was established for the 39-mile, 59-mile, and adjacent segments of the Missouri National Recreational River administered by the National Park Service in South Dakota and Nebraska. The objective of the classification was to define naturally occurring clusters of geomorphic characteristics that would be indicative of discrete sets of geomorphic processes, with the intent that such a classification would be useful in river-management and rehabilitation decisions. The statistical classification was based on geomorphic characteristics of the river collected from 1999 orthophotography and the persistence of classified units was evaluated by comparison with similar datasets for 2003 and 2004 and by evaluating variation of bank erosion rates by geomorphic class. Changes in channel location and form were also explored using imagery and maps from 1993-2004, 1941 and 1894. The multivariate classification identified a hierarchy of naturally occurring clusters of reach-scale geomorphic characteristics. The simplest level of the hierarchy divides the river from segments into discrete reaches characterized by single and multithread channels and additional hierarchical levels established 4-part and 10-part classifications. The classification system presents a physical framework that can be applied to prioritization and design of bank stabilization projects, design of habitat rehabilitation projects, and stratification of monitoring and assessment sampling programs.

Modern Pearl River Delta and Permian Huainan coalfield, China: A comparative sedimentary facies study

USGS Publications Warehouse

Suping, P.; Flores, R.M.

1996-01-01

Sedimentary facies types of the Pleistocene deposits of the Modern Pearl River Delta in Guangdong Province, China and Permian Member D deposits in Huainan coalfield in Anhui Province are exemplified by depositional facies of anastomosing fluvial systems. In both study areas, sand/sandstone and mud/mudstone-dominated facies types formed in diverging and converging, coeval fluvial channels laterally juxtaposed with floodplains containing ponds, lakes, and topogenous mires. The mires accumulated thin to thick peat/coal deposits that vary in vertical and lateral distribution between the two study areas. This difference is probably due to attendant sedimentary processes that affected the floodplain environments. The ancestral floodplains of the Modern Pearl River Delta were reworked by combined fluvial and tidal and estuarine processes. In contrast, the floodplains of the Permian Member D were mainly influenced by freshwater fluvial processes. In addition, the thick, laterally extensive coal zones of the Permian Member D may have formed in topogenous mires that developed on abandoned courses of anastomosing fluvial systems. This is typified by Seam 13-1, which is a blanket-like body that thickens to as much as 8 in but also splits into thinner beds. This seam overlies deposits of diverging and converging, coeval fluvial channels of the Sandstone D, and associated overbank-floodplain deposits. The limited areal extent of lenticular Pleistocene peat deposits of the Modern Pearl River Delta is due to their primary accumulation in topogenous mires in the central floodplains that were restricted by contemporaneous anastomosing channels.

Coupled stream and population dynamics: Modeling the role beaver (Castor canadensis) play in generating juvenile steelhead (Oncorhynchus mykiss) habitat

NASA Astrophysics Data System (ADS)

Jordan, C.; Bouwes, N.; Wheaton, J. M.; Pollock, M.

2013-12-01

Over the past several centuries, the population of North American Beaver has been dramatically reduced through fur trapping. As a result, the geomorphic impacts long-term beaver occupancy and activity can have on fluvial systems have been lost, both from the landscape and from our collective memory such that physical and biological models of floodplain system function neither consider nor have the capacity to incorporate the role beaver can play in structuring the dynamics of streams. Concomitant with the decline in beaver populations was an increasing pressure on streams and floodplains through human activity, placing numerous species of stream rearing fishes in peril, most notably the ESA listing of trout and salmon populations across the entirety of the Western US. The rehabilitation of stream systems is seen as one of the primary means by which population and ecosystem recovery can be achieved, yet the methods of stream rehabilitation are applied almost exclusively with the expected outcome of a static idealized stream planform, occasionally with an acknowledgement of restoring processes rather than form and only rarely with the goal of a beaver dominated riverscape. We have constructed an individual based model of trout and beaver populations that allows the exploration of fish population dynamics as a function of stream habitat quality and quantity. We based the simulation tool on Bridge Creek (John Day River basin, Oregon) where we have implemented a large-scale restoration experiment using wooden posts to provide beavers with stable platforms for dam building and to simulate the dams themselves. Extensive monitoring captured geomorphic and riparian changes, as well as fish and beaver population responses; information we use to parameterize the model as to the geomorphic and fish response to dam building beavers. In the simulation environment, stream habitat quality and quantity can be manipulated directly through rehabilitation actions and indirectly through the dynamics of the co-occurring beaver population. The model allowed to us to ask questions critical for designing restoration strategies based on dam building beaver activity, such as what beaver population growth rate is required to develop and maintain floodplain connectivity in an incised system, or what beaver population size is required to increase juvenile steelhead production? The model was sensitive to several variables including beaver colony size, dams and colony dynamics and site fidelity, and thus highlights further research needs to fill critical information gaps.

Fluvial-system response to climate change: The Paleocene-Eocene Tremp Group, Pyrenees, Spain

NASA Astrophysics Data System (ADS)

Colombera, Luca; Arévalo, Oscar J.; Mountney, Nigel P.

2017-10-01

The Tremp Group of the Tremp-Graus Basin (Southern Pyrenees, Spain) is a succession of predominantly continental origin that records the Paleocene-Eocene Thermal Maximum (PETM), a transient episode of extreme global warming that occurred across the Paleocene-Eocene boundary. For this succession, the stratigraphic position of the PETM is accurately determined, and histories of tectonic and sea-level controls are well constrained. Building upon previous studies, this work assesses changes in sedimentary architecture through the PETM in the Tremp Group, based on quantitative sedimentological analyses documented over a km-scale strike-oriented transect in the Arén area, with the scope to better understand the response of this alluvial system to the hyperthermal event. The analysed features represent a partial record of the geomorphic organization and processes of the system at the time of deposition, and are therefore interpretable in terms of geomorphic change in alluvial landscapes caused by the PETM. The record of the PETM, as previously recognized, begins at a time when erosional palaeotopographic relief was developed and deposition was confined in valleys. A shift between valley back-filling and widespread aggradation is observed at the onset of the PETM interval, which demonstrates uniquely the impact of the hyperthermal on both depositional loci and interfluves. Compared to underlying strata, the interval that embodies the onset and main phase of the PETM is characterized by: (i) higher proportion of channel deposits; (ii) channel complexes of greater average thickness and width; (iii) barforms and channel fills that are slightly thicker; (iv) increased thickness of sets of cross-stratified sandstones; (v) similar values of maximum extraclast size, by architectural element. An evident change in the facies organization of channel deposits is also seen through the stratigraphy, though this appears to predate the PETM. Increased channel-body density in the PETM interval can be explained in terms of increased channel mobility, which itself can be related to changes in the stream catchments (e.g., greater bedload delivery, increased water discharge or discharge variability), or to changes in the nature of the depositional basin that would permit the channels to be more mobile (e.g., increased bank erodibility due to variations in vegetation type and density). Interfluve planation is inferred to have occurred immediately prior to, or penecontemporaneously with, accumulation of PETM deposits, which is in accord with inferences of increased erodibility of the interfluves or increased stream erosive power. These observations offer insight into the potential geomorphic metamorphosis of river systems in mid-latitude regions experiencing conditions of rapid global warming.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gulick, V.C.; Baker, V.R.

Morphological analyses of six Martian volcanoes, Ceraunius Tholus, Hecates Tholus, Alba Patera, Hadriaca Patera, Apollinaris Patera, and Tyrrhena Patera, indicate that fluvial processes were the dominant influence in the initiation and subsequent development of many dissecting valleys. Lava processes and possibly volcanic density flows were also important as valley-forming processes. Fluvial valleys are especially well developed on Alba Patera, Ceraunius Tholus, and Hecates Tholus. These valleys are inset into the surrounding landscape. They formed in regions of subdued lava flow morphology, contain tributaries, and tend to widen slightly in the downstream direction. Lava channels on Alba Patera are located onmore » the crest of lava flows and have a discontinuous, irregular surface morphology, and distributary patterns. These channels sometimes narrow toward their termini. Possible volcanic density flow channels are located on the northern flank of Ceraunius Tholus. Valleys dissecting Apollinaris Patera, Hadriaca Patera, and Tyrrhena Patera appear to have a complex evolution, probably a mixed fluvial and lava origin. They are inset into a subdued (possibly mantled) surface, lack tributaries, and either have fairly constant widths or widen slightly downvalley. Valleys surrounding the caldera of Apollinaris appear to have formed by fluvial and possibly by volcanic density flow processes, while those on the Apollinaris fan structure may have a mixed lava and fluvial origin. Valleys on Tyrrhena have broad flat floors and theater heads, which have been extensively enlarged, probably by sapping.« less

River history.

PubMed

Vita-Finzi, Claudio

2012-05-13

During the last half century, advances in geomorphology-abetted by conceptual and technical developments in geophysics, geochemistry, remote sensing, geodesy, computing and ecology-have enhanced the potential value of fluvial history for reconstructing erosional and depositional sequences on the Earth and on Mars and for evaluating climatic and tectonic changes, the impact of fluvial processes on human settlement and health, and the problems faced in managing unstable fluvial systems. This journal is © 2012 The Royal Society

Effects of Fault Segmentation, Mechanical Interaction, and Structural Complexity on Earthquake-Generated Deformation

ERIC Educational Resources Information Center

Haddad, David Elias

2014-01-01

Earth's topographic surface forms an interface across which the geodynamic and geomorphic engines interact. This interaction is best observed along crustal margins where topography is created by active faulting and sculpted by geomorphic processes. Crustal deformation manifests as earthquakes at centennial to millennial timescales. Given that…

Combining Mechanistic Approaches for Studying Eco-Hydro-Geomorphic Coupling

NASA Astrophysics Data System (ADS)

Francipane, A.; Ivanov, V.; Akutina, Y.; Noto, V.; Istanbullouglu, E.

2008-12-01

Vegetation interacts with hydrology and geomorphic form and processes of a river basin in profound ways. Despite recent advances in hydrological modeling, the dynamic coupling between these processes is yet to be adequately captured at the basin scale to elucidate key features of process interaction and their role in the organization of vegetation and landscape morphology. In this study, we present a blueprint for integrating a geomorphic component into the physically-based, spatially distributed ecohydrological model, tRIBS- VEGGIE, which reproduces essential water and energy processes over the complex topography of a river basin and links them to the basic plant life regulatory processes. We present a preliminary design of the integrated modeling framework in which hillslope and channel erosion processes at the catchment scale, will be coupled with vegetation-hydrology dynamics. We evaluate the developed framework by applying the integrated model to Lucky Hills basin, a sub-catchment of the Walnut Gulch Experimental Watershed (Arizona). The evaluation is carried out by comparing sediment yields at the basin outlet, that follows a detailed verification of simulated land-surface energy partition, biomass dynamics, and soil moisture states.

Root tensile strength assessment of Dryas octopetala L. and implications for its engineering mechanism on lateral moraine slopes (Turtmann Valley, Switzerland)

NASA Astrophysics Data System (ADS)

Eibisch, Katharina; Eichel, Jana; Dikau, Richard

2015-04-01

Geomorphic processes and properties are influenced by vegetation. It has been shown that vegetation cover intercepts precipitation, enhances surface detention and storage, traps sediment and provides additional surface roughness. Plant roots impact the soil in a mechanical and hydrological manner and affect shear strength, infiltration capacity and moisture content. Simultaneously, geomorphic processes disturb the vegetation development. This strong coupling of the geomorphic and ecologic system is investigated in Biogeomorphology. Lateral moraine slopes are characterized by a variety of geomorphic processes, e. g. sheet wash, solifluction and linear erosion. However, some plant species, termed engineer species, possess specific functional traits which allow them to grow under these conditions and also enable them to influence the frequency, magnitude and even nature of geomorphic processes. For lateral moraine slopes, Dryas octopetala L., an alpine dwarf shrub, was identified as a potential engineer species. The engineering mechanism of D. octopetala, based on its morphological (e.g., growth form) and biomechanical (e.g., root strength) traits, yet remains unclear and only little research has been conducted on alpine plant species. The objectives of this study are to fill this gap by (A) quantifying D. octopetala root tensile strength as an important trait considering anchorage in and stabilization of the slope and (B) linking plant traits to the geomorphic process they influence on lateral moraine slopes. D. octopetala traits were studied on a lateral moraine slope in Turtmann glacier forefield, Switzerland. (A) Root strength of single root threads of Dryas octopetala L. were tested using the spring scale method (Schmidt et al., 2001; Hales et al., 2013). Measurement equipment was modified to enable field measurements of roots shortly after excavation. Tensile strength of individual root threads was calculated and statistically analyzed. First results show that Dryas roots appear to be quite strong compared to other alpine species with a mean tensile strength of 22,63 N mm -². (B) On a micro scale, morphological and biomechanical features of above and below-ground biomass were qualitatively studied through field observations on D. octopetala individuals. Findings indicate that D. octopetala's dense cushions, covering many square meters of the moraines surface, traps fine sediment, stores moisture and significantly reduces erosion through wind and water. Furthermore, Dryas is well adapted to rock fall or burial by forming stabilized patches of ground despite steep slope inclinations and strong, episodic surface runoff and creep processes. Anchorage is provided by its strong root, which in all studied cases grew upslope parallel to the moraines surface. Insights from this study allow to relate root tensile strength and other specific plant traits of Dryas octopetala to an engineering mechanism and effect on geomorphic processes on lateral moraine slopes. Knowledge about Dryas as an engineering species may help to understand its biotic influence on the geomorphic system of a lateral moraine and aid in the selection of species for erosion control or rehabilitation of ecosystems, where Dryas is native.

Andrean examples of mega-geomorphology themes

NASA Technical Reports Server (NTRS)

Bloom, A. L.

1985-01-01

Geomorphic (or physiographic) provinces have been a well known and useful method of regional landform classification for a century. Every earth scientist will recognize a phrase such as Appalachian Plateau or Southern Rocky Mountains as defining a discrete region of consistent geologic structure that has experienced a similar interval of erosion by a similar process or set of processes. The geomorphic provinces formalized in the United States by Fenneman in the 1920's continue to be highly satisfactory even though some boundaries were only vaguely drawn. Mosaics of LANDSAT images illustrate better than any earlier maps the validity and coherence of Fenneman's provinces. The concept of geomorphic provinces has been used subconsciously or intuitively, to describe the relief of the ocean floor and the topography of the Moon and other planets.

Legacy effects in linked ecological-soil-geomorphic systems of drylands

USGS Publications Warehouse

Monger, Curtis; Sala, Osvaldo E.; Duniway, Michael C.; Goldfus, Haim; Meir, Isaac A.; Poch, Rosa M.; Throop, Heather L.; Vivoni, Enrique R.

2015-01-01

A legacy effect refers to the impacts that previous conditions have on current processes or properties. Legacies have been recognized by many disciplines, from physiology and ecology to anthropology and geology. Within the context of climatic change, ecological legacies in drylands (eg vegetative patterns) result from feedbacks between biotic, soil, and geomorphic processes that operate at multiple spatial and temporal scales. Legacy effects depend on (1) the magnitude of the original phenomenon, (2) the time since the occurrence of the phenomenon, and (3) the sensitivity of the ecological–soil–geomorphic system to change. Here we present a conceptual framework for legacy effects at short-term (days to months), medium-term (years to decades), and long-term (centuries to millennia) timescales, which reveals the ubiquity of such effects in drylands across research disciplines.

GEOMORPHIC CONTROLS ON MEADOW ECOSYSTEMS – INSIGHTS INTO LOCAL PROCESSES USING NEAR-SURFACE SEISMIC TECHNIQUES AND GROUND PENETRATING RADAR

EPA Science Inventory

Geomorphic controls on riparian meadows in the Central Great Basin of Nevada are an important aspect in determining the formation of and planning the management of these systems. The current hypothesis is that both alluvial fan sediment and faulted bedrock steps interact to cont...

Application of Terrestrial Geomorphic Threshold Theory to the Analysis of Small Channels on Mars

NASA Technical Reports Server (NTRS)

Rosenshein, E. B.; Greeley, R.; Arrowsmith, J. R.

2001-01-01

New terrestrial work on the geomorphic thresholds for channel initiation use the drainage area above a channel head vs. the slope at the channel head to delineate surface process types. This method has been used to characterize martian landscapes. Additional information is contained in the original extended abstract.

Reconstructing Sediment Supply, Transport and Deposition Behind the Elwha River Dams

NASA Astrophysics Data System (ADS)

Beveridge, C.

2017-12-01

The Elwha River watershed in Olympic National Park of Washington State, USA is predominantly a steep, mountainous landscape where dominant geomorphic processes include landslides, debris flows and gullying. The river is characterized by substantial variability of channel morphology and fluvial processes, and alternates between narrow bedrock canyons and wider alluvial reaches for much of its length. Literature suggests that the Elwha watershed is topographically and tectonically in steady state. The removal of the two massive hydropower dams along the river in 2013 marked the largest dam removal in history. Over the century long lifespan of the dams, approximately 21 million cubic meters of sediment was impounded behind them. Long term erosion rates documented in this region and reservoir sedimentation data give unprecedented opportunities to test watershed sediment yield models and examine dominant processes that control sediment yield over human time scales. In this study, we aim to reconstruct sediment supply, transport and deposition behind the Glines Canyon Dam (most upstream dam) over its lifespan using a watershed modeling approach. We developed alternative models of varying complexity for sediment production and transport at the network scale driven by hydrologic forcing. We simulate sediment supply and transport in tributaries upstream of the dam. The modeled sediment supply and transport dynamics are based on calibrated formulae (e.g., bedload transport is simulated using Wilcock-Crowe 2003 with modification based on observed bedload transport in the Elwha River). Observational data that aid in our approach include DEM, channel morphology, meteorology, and streamflow and sediment (bedload and suspended load) discharge. We aim to demonstrate how the observed sediment yield behind the dams was influenced by upstream transport supply and capacity limitations, thereby demonstrating the scale effects of flow and sediment transport processes in the Elwha River watershed.

Orographic Barriers, Rainshadows, and Earth Surface Processes in the Central Andes

NASA Astrophysics Data System (ADS)

Bookhagen, B.; Strecker, M. R.

2016-12-01

The Central Andes of NW Argentina, northern Chile, and SW Bolivia are characterized by a steep E-W topographic, climatic and environmental gradient. The first windward topographic rise in the eastern Central Andes forces high orographic rainfall and dense vegetation. In contrast, the higher-elevation areas of the windward flanks become progressively drier, until arid conditions are attained in the orogen interior. On seasonal, annual, and inter-annual timescales, large rainstorms may propagate into the semi-arid to arid high-elevation sectors and cause erosion and mass-transport processes that impact infrastructure and the natural environment. Similar to these present-day effects of climate variability the Central Andes experienced pronounced paleoclimatic changes with deeper penetration of moisture into the orogen and thus an orogenward shift of the climate gradient during Pleistocene and Holocene times, lasting several millennia. In this presentation, we demonstrate the impact of climate change on Earth surface processes at different timescales ranging from the late Pleistocene to the past decade. For millennial timescales and beyond, we rely on field observations, dating of geomorphic markers, erosion rates from cosmogenic nuclide dating, and the analysis of sedimentary archives to reconstruct past environmental conditions. For the last decades we use, satellite-derived rainfall and landcover observations, climate models, hydrometeorologic data, and riverbed-elevation changes are used to characterize environmental and atmospheric conditions. Decadal-scale climate variability shows statistically significant hydrometeorologic trends and exhibits changes of fluvial-transport magnitudes. Hydrometeorologic data, their trends and change points suggest that highest rainfall magnitudes have increased most in the past decades, resulting in large, event-driven mass-transport processes with fundamental impacts on population and infrastructure.

A manual to identify sources of fluvial sediment

USGS Publications Warehouse

Gellis, Allen C.; Fitzpatrick, Faith A.; Schubauer-Berigan, Joseph

2016-01-01

Sediment is an important pollutant of concern that can degrade and alter aquatic habitat. A sediment budget is an accounting of the sources, storage, and export of sediment over a defined spatial and temporal scale. This manual focuses on field approaches to estimate a sediment budget. We also highlight the sediment fingerprinting approach to attribute sediment to different watershed sources. Determining the sources and sinks of sediment is important in developing strategies to reduce sediment loads to water bodies impaired by sediment. Therefore, this manual can be used when developing a sediment TMDL requiring identification of sediment sources.The manual takes the user through the seven necessary steps to construct a sediment budget:Decision-making for watershed scale and time period of interestFamiliarization with the watershed by conducting a literature review, compiling background information and maps relevant to study questions, conducting a reconnaissance of the watershedDeveloping partnerships with landowners and jurisdictionsCharacterization of watershed geomorphic settingDevelopment of a sediment budget designData collectionInterpretation and construction of the sediment budgetGenerating products (maps, reports, and presentations) to communicate findings.Sediment budget construction begins with examining the question(s) being asked and whether a sediment budget is necessary to answer these question(s). If undertaking a sediment budget analysis is a viable option, the next step is to define the spatial scale of the watershed and the time scale needed to answer the question(s). Of course, we understand that monetary constraints play a big role in any decision.Early in the sediment budget development process, we suggest getting to know your watershed by conducting a reconnaissance and meeting with local stakeholders. The reconnaissance aids in understanding the geomorphic setting of the watershed and potential sources of sediment. Identifying the potential sediment sources early in the design of the sediment budget will help later in deciding which tools are necessary to monitor erosion and/or deposition at these sources. Tools can range from rapid inventories to estimate the sediment budget or quantifying sediment erosion, deposition, and export through more rigorous field monitoring. In either approach, data are gathered and erosion and deposition calculations are determined and compared to the sediment export with a description of the error uncertainty. Findings are presented to local stakeholders and management officials.Sediment fingerprinting is a technique that apportions the sources of fine-grained sediment in a watershed using tracers or fingerprints. Due to different geologic and anthropogenic histories, the chemical and physical properties of sediment in a watershed may vary and often represent a unique signature (or fingerprint) for each source within the watershed. Fluvial sediment samples (the target sediment) are also collected and exhibit a composite of the source properties that can be apportioned through various statistical techniques. Using an unmixing-model and error analysis, the final apportioned sediment is determined.

Drainage development and incision rates in an Upper Pleistocene Basalt-Limestone Boundary Channel: The Sa'ar Stream, Golan Heights, Israel

NASA Astrophysics Data System (ADS)

Shtober-Zisu, N.; Inbar, M.; Mor, D.; Jicha, B. R.; Singer, B. S.

2018-02-01

Long-term fluvial incision processes and corresponding geomorphic evolution are difficult to quantify, especially in complex systems affected by lithological and tectonic factors. Volcanic landscapes offer the most appropriate environment for the study of landscape evolution, as there is a clear starting time of formation and the lithology is homogenous. In the present study we aim to: (1) analyse the interplay of construction and incision processes throughout eruptive activity; (2) study fluvial erosion processes; (3) analyse sedimentary and volcanic lithological responses to channel erosion; and (4) calculate the incision rates in young basaltic bedrock. We have integrated existing and new 40Ar/39Ar ages of lava flows with estimates of channel geometry and tectonic activity, and considered process geomorphology concepts, to fully understand evolution of a bedrock channel incised at the boundary between basalts and sedimentary rocks with coeval active volcanic processes forcing drainage evolution. Our findings indicate that the Sa'ar basin evolution is controlled by: (1) rock strength of the mixed lithology; (2) alternating cycles of volcanic activity followed by erosion and incision; and (3) the Plio-Pleistocene uplift of Mt. Hermon. The carbonate slopes composing the southern flank of Mt. Hermon are moderate (18-26%) while the basalt slopes deriving from the Golan Heights are much steeper (26-51%). The highly erodible sedimentary rocks at Mt. Hermon's piedmont accelerated river incision, shaping a 650 m wide by 100 m deep canyon. Inside the canyon, the steep channel slope (8.6%) enables downstream movement of large boulders, including autochthonous mega-blocks (D90 size > 2.5 m); 24 knickpoints were identified using DS plots, developed within a knick zone over a distance of 6 km. The brittle and porous structure of the rubbly and blocky interflow layers (clinkers), interbedded between two massive basalt flows, enhances erosion and accelerates scouring of the plunge-pool bottom and walls. Three volcanic phases shaped the Sa'ar basin: (1) The 3.25 Ma Cover Basalt flowed over large areas of the Levant and reached up to the northern Golan; (2) Dalwe Basalt was emplaced between 1.2 Ma and 750 ka, from vents including Mt. Qatzaa and Mt. Odem, and extended to Mt. Hermon covering sedimentary cuestas; (3) Ein Zivan Basalt (including the Sa'ar Lava Flow - the youngest basalt flow known in Israel) erupted before 110-120 ka and quickly accumulated at least three distinct flows into the deeply incised Paleo-Sa'ar canyon, refilling the canyon to a height of 50 m. Rates of incision are consistent with other rivers draining the Golan Heights. The total incision rate of the Sa'ar channel during the last 760 ka is at least 19.7 cm/ka. Over the past 100 ka, the incision rate was 22-30 cm/ka and the back-erosion of the Sa'ar highest knickpoint occurred at 68 cm/ka. Our findings reflect the latest evolution history of a special, mixed lithology channel, developed at the border of a large basaltic province, in an active tectonic environment. The results suggest that fluvial adjustment of basalt-limestone rivers is determined first by the interplay of construction and incision processes throughout alternating cycles of volcanic activity and quiescence. The lithology is an extremely important factor determining the type and rate of erosion. While the tectonic factor might determine the basin relief and slope, the lithological factor accelerates erosion and river incision.

An assessment of anthropogenic and climatic stressors on estuaries using a spatio-temporal GIS-modelling approach for sustainability: Towamba estuary, southeastern Australia.

PubMed

Al-Nasrawi, Ali K M; Hamylton, Sarah M; Jones, Brian G

2018-06-03

Monitoring estuarine ecological-geomorphological dynamics has become a crucial aspect of studying the impacts of climate change and worldwide infrastructure development in coastal zones. Together, these factors have changed the natural eco-geomorphic processes that affect estuarine regimes and comprehensive modelling of coastal resources can assist managers to make appropriate decisions about their sustainable use. This study has utilised Towamba estuary (southeastern NSW, Australia), to demonstrate the value and priority of modelling estuarine dynamism as a measure of the rates and consequences of eco-geomorphic changes. This research employs several geoinformatic modelling approaches over time to investigate and assess how climate change and human activities have altered this estuarine eco-geomorphic setting. Multitemporal trend/change analysis of sediment delivery, shoreline positions and land cover, determined from fieldwork and GIS analysis of remote sensing datasets, shows significant spatio-temporal changes to the elevation and areal extent of sedimentary facies in the Towamba estuary over the past 65 years. Geomorphic growth (~ 2600 m 2 annually) has stabilised the estuarine habitats, particularly within native vegetation, salt marsh and mangrove areas. Geomorphic changes have occurred because of a combination of sediment runoff from the mostly unmodified terrestrial catchment, nearshore processes (ocean dynamics) and human activities. The construction of GIS models, verified with water and sediment samples, can characterise physical processes and quantify changes within the estuarine ecosystem. Such robust models will allow resource managers to evaluate the potential effects of changes to the current coastal ecosystems.

Sedimentary Processes on Earth, Mars, Titan, and Venus

NASA Astrophysics Data System (ADS)

Grotzinger, J. P.; Hayes, A. G.; Lamb, M. P.; McLennan, S. M.

The production, transport and deposition of sediment occur to varying degrees on Earth, Mars, Venus, and Titan. These sedimentary processes are significantly influenced by climate that affects production of sediment in source regions (weathering), and the mode by which that sediment is transported (wind vs. water). Other, more geological, factors determine where sediments are deposited (topography and tectonics). Fluvial and marine processes dominate Earth both today and in its geologic past, aeolian processes dominate modern Mars although in its past fluvial processes also were important, Venus knows only aeolian processes, and Titan shows evidence of both fluvial and aeolian processes. Earth and Mars also feature vast deposits of sedimentary rocks, spanning billions of years of planetary history. These ancient rocks preserve the long-term record of the evolution of surface environments, including variations in climate state. On Mars, sedimentary rocks record the transition from wetter, neutral-pH weathering, to brine-dominated low-pH weathering, to its dry current state.

Deconvolving regional and fault-driven uplift in Calabria using drainage inversion techniques and field observations

NASA Astrophysics Data System (ADS)

Quye-Sawyer, Jennifer; Whittaker, Alexander; Roberts, Gareth; Rood, Dylan

2017-04-01

A key challenge in the Earth Sciences is to understand the timing and extent of the coupling between geodynamics, tectonics, and surface processes. In principle, the landscape adjusts to surface uplift or tectonic events, and present-day topography records a convolution of these processes. The inverse problem, the ability to find the 'best fit' theoretical scenario to match present day observations, is particularly desirable as it makes use of real data, encompasses the complexity of natural systems and quantifies model uncertainty through misfit. The region of Calabria, Italy, is known to have experienced geologically rapid uplift ( 1 mm/yr) since the Early Pleistocene, inferred from widespread marine terraces (ca. 1 Myr old) at elevations greater than 1 km. In addition, this is a tectonically active area of normal faulting with several highly destructive earthquakes in recent centuries. Since there has been some debate about the relative magnitudes of the uplift caused by regional processes or by faulting, the ability to model these effects on a regional scale may help resolve this problem. Therefore, Calabria is both a suitable and important site to model large magnitude recent geomorphic change. 1368 river longitudinal profiles have been generated from satellite digital elevation models (DEMs). These longitudinal profiles were compared to aerial photography to confirm the accuracy of this automated process. The longitudinal profiles contain numerous non-lithologically controlled knickpoints. Field observations support the presence of knickpoints extracted from the DEM and measurements of pebble imbrication from fluvial terraces suggest the planform stability of the drainage network in the last 1 Myr. By assuming fluvial erosion obeys stream power laws with an exponent of upstream area of 0.5 ± 0.1, the evolution of the landscape is computed using a linearized joint inversion of the longitudinal profiles. This has produced a spatially and temporally continuous model of cumulative uplift for the Calabria region. We have used independently-collated stratigraphic data to provide absolute ages for the inversion model. In particular, uplift rates of well-dated marine terraces constrain the inversion near the coastline and we are using cosmogenic isotope isochron burial dating to refine the timing of the onset of uplift. Preliminary inversion results show the initiation of uplift at approximately 1.9 Ma. The model output is consistent with field observations of regional uplift, later combined with fault related extension. Furthermore, these results are consistent with an increase in regional uplift rate prior to fault initiation.

Gully evolution and geomorphic adjustments of badlands to recent afforestation

NASA Astrophysics Data System (ADS)

Ballesteros-Cánovas, Juan Antonio; Stoffel, Markus; Francisco Martín-Duque, Jose; Corona, Christophe; Lucia, Ana; María Bodoque, Jose

2016-04-01

Badlands and gullied areas are among the geomorphic environments with the highest erosion rates worldwide, however records on their evolution are very scarce and often limited to presumed initial conditions and the known present state. In this communication, we present a unique and very dense and annual record and outstanding example of erosion processes in a Mediterranean environment in Central Spain, where badland and gullying processes on sandy slopes of a set of mesas have been presumably triggered by quarrying activities since Medieval times. The gully channel evolution here analyzed provides an exceptional example of a larger setting of geomorphic. Besides the analysis of geomorphic adjustments to historical land-use changes induced by historical quarrying and gullying dynamics, we also quantified the impact of current geomorphic adjustments to 20th century afforestation by combining multiproxy such as aerial photography, historical archives, and large dataset of exposed roots to date, quantify, and reconstruct the morphology of a rapidly evolving channel in a gullied catchment. In this analysis, more than 150 exposed roots were analyzed to quantify and report channel incision; widening and gully retreatment rates during the last decades, as well as to quantify sheet erosion on different soil units. Our results suggest that, rather than stabilizing gully evolution, the afforestation carried out during 1960s has played an important role in water-sediment balance and connectivity and would have triggered the initiation of channel incision processes in the 1980s. Therefore, we observe that the channel incision match with a significant increase of the vegetation cover, which leads a significant decrease in sheet erosion rates. Based on our long-term annual gully reconstruction, we observed that sediment delivery does not correlate with the estimated intensity of precipitation (Fourier index). Instead, we observe abrupt morphological changes in the gully are presumably related with changes in connectivity after a specific intense event. Consequently, we hypothesize that the gullying process-vegetation interactions are subsidiary of the geomorphic adjustments and connectivity states of the system; and speculate that this understanding is essential for suitable restoration and management plans.

A geomorphological approach to sustainable planning and management of the coastal zone of Kuwait

NASA Astrophysics Data System (ADS)

Al Bakri, Dhia

1996-10-01

The coastal zone in Kuwait has been under a considerable pressure from conflicting land uses since the early 1960s, as well as from the destruction and oil pollution caused by the Gulf War. To avoid further damage and to protect the coastal heritage it is essential to adopt an environmentally sustainable management process. This paper shows how the study of coastal geomorphology can provide a sound basis for sustainable planning and management. Based on coastal landforms, sediments and processes, the coastline of Kuwait was divided into nine geomorphic zones. These zones were grouped into two main geomorphic provinces. The northern province is marked by extensive muddy intertidal flats and dominated by a depositional and low-energy environment. The southern geomorphic province is characterised by relatively steep beach profiles, rocky/sandy tidal flats and a moderate to high-energy environment. The study has demonstrated that pollution, benthic ecology and other environmental conditions of the coast are a function of coastline geomorphology, sedimentology and related processes. The geomorphological information was used to determine the coastal vulnerability and to assess the environmental impacts of development projects and other human activities. Several strategies were outlined to integrate the geomorphic approach into the management of the coastal resources.

Morphology of fluvial levee series along a river under human influence, Maros River, Hungary

NASA Astrophysics Data System (ADS)

Kiss, Tímea; Balogh, Márton; Fiala, Károly; Sipos, György

2018-02-01

The development and morphometry of fluvial levees reflect the connection between channel and overbank processes, which can be altered by various human activities. The aims of this study are to investigate the morphology and spatial characteristics of fluvial levees and evaluate the role of some local- and catchment-scale human activities on their medium-term (150 years) development. This study applies LiDAR data along a 53-km-long reach of the Maros River in Hungary. Six fluvial levee types are identified based on the beginning and end of their evolution. These levee types were generated by local nineteenth century channel regulation works (cutoffs) and mid-twentieth century channel narrowing, which was caused by gravel mining and water impoundment in the upstream sections. However, other human activities also influenced the development of active fluvial levees because their horizontal evolution could have been limited by embanked flood-protection levees or the widening of low-lying floodplain benches that were generated by channel narrowing. Additionally, revetment constructions influenced their vertical parameters as higher fluvial levees developed along the fixed banks. Generally, the older active fluvial levees are wider, while the younger active levees are narrower with steeper slopes but not always lower. On the low-lying floodplain levels (benches), the youngest fluvial levees evolved quite rapidly and consist of coarser material. Currently, only 9.8- to 38-year return-period floods could cover the fluvial levees, contributing to their evolution. This fact and the development of fluvial levee series with two-three members reflect a gradual decoupling of the channel from the floodplain.

Drainage-basis-scale geomorphic analysis to determine refernce conditions for ecologic restoration-Kissimmee River, Florida

USGS Publications Warehouse

Warne, A.G.; Toth, L.A.; White, W.A.

2000-01-01

Major controls on the retention, distribution, and discharge of surface water in the historic (precanal) Kissimmee drainage basin and river were investigated to determine reference conditions for ecosystem restoration. Precanal Kissimmee drainage-basin hydrology was largely controlled by landforms derived from relict, coastal ridge, lagoon, and shallow-shelf features; widespread carbonate solution depressions; and a poorly developed fluvial drainage network. Prior to channelization for flood control, the Kissimmee River was a very low gradient, moderately meandering river that flowed from Lake Kissimmee to Lake Okeechobee through the lower drainage basin. We infer that during normal wet seasons, river discharge rapidly exceeded Lake Okeechobee outflow capacity, and excess surface water backed up into the low-gradient Kissimmee River. This backwater effect induced bankfull and peak discharge early in the flood cycle and transformed the flood plain into a shallow aquatic system with both lacustrine and riverine characteristics. The large volumes of surface water retained in the lakes and wetlands of the upper basin maintained overbank flow conditions for several months after peak discharge. Analysis indicates that most of the geomorphic work on the channel and flood plain occurred during the frequently recurring extended periods of overbank discharge and that discharge volume may have been significant in determining channel dimensions. Comparison of hydrogeomorphic relationships with other river systems identified links between geomorphology and hydrology of the precanal Kissimmee River. However, drainage-basin and hydraulic geometry models derived solely from general populations of river systems may produce spurious reference conditions for restoration design criteria.

Evaluation of Geomorphic Changes, Using Landsat Data and its Impact on Coastal Community

NASA Astrophysics Data System (ADS)

Mahar, G. A.

2017-12-01

temporal study with the help of landsat satellite image has been carried out to assess the degree of the geomorphic degradation of different deltaic features and its consequent impact on the demography and socioeconomics of the people. Interactive correlation of the present analyses of the Indus water-flow in relation to the manmade water divergent structures reveals that the massive water divergence to upstream areas by depleting water availability into the downstream areas have caused severe imbalance in the equilibrium between the fluvial and marine hydrodynamics. The dominance of the marine hydrodynamic conditions have caused irreversible damage to the physical environment due to the rapid landward sea invasion. Based on the results of the present study it has been identified that i) the coastline is rapidly retreating; ii) individual creeks and the creeks' network are enlarging by the erosional phenomenon laterally as well as longitudinally; iii) tidally influenced areas are rapidly expanding; iv) overall area of the deltaic lakes is reducing but the frequency of the lakes occurrences is increasing; v) the course and the thalweg of the Indus river is widening seaward and narrowing landward; vi) populated areas along the coastline have been evacuated due to the massive seawater intrusions; vii) agricultural and fishing activities are tremendously declining and viii) food productivity per acre is decreasing. Moreover, it is also revealed that i) the shelf slope is steeping and retreating faster and ii) geometry of the Indus canyon is also rapidly changing. This phenomenon has affected the socio-economic of the coastal community and from many place force them to move from their native places.

Landscape Evolution of Titan

NASA Technical Reports Server (NTRS)

Moore, Jeffrey

2012-01-01

Titan may have acquired its massive atmosphere relatively recently in solar system history. The warming sun may have been key to generating Titan's atmosphere over time, starting from a thin atmosphere with condensed surface volatiles like Triton, with increased luminosity releasing methane, and then large amounts of nitrogen (perhaps suddenly), into the atmosphere. This thick atmosphere, initially with much more methane than at present, resulted in global fluvial erosion that has over time retreated towards the poles with the removal of methane from the atmosphere. Basement rock, as manifested by bright, rough, ridges, scarps, crenulated blocks, or aligned massifs, mostly appears within 30 degrees of the equator. This landscape was intensely eroded by fluvial processes as evidenced by numerous valley systems, fan-like depositional features and regularly-spaced ridges (crenulated terrain). Much of this bedrock landscape, however, is mantled by dunes, suggesting that fluvial erosion no longer dominates in equatorial regions. High midlatitude regions on Titan exhibit dissected sedimentary plains at a number of localities, suggesting deposition (perhaps by sediment eroded from equatorial regions) followed by erosion. The polar regions are mainly dominated by deposits of fluvial and lacustrine sediment. Fluvial processes are active in polar areas as evidenced by alkane lakes and occasional cloud cover.

Geomorphic change in the Limitrophe reach of the Colorado River in response to the 2014 delta pulse flow, United States and Mexico

USGS Publications Warehouse

Mueller, Erich R.; Schmidt, John C.; Topping, David; Grams, Paul E.

2015-01-01

A pulse of water was released from Morelos Dam into the dry streambed of the Colorado River in its former delta on March 23, 2014. Although small in relation to delta floods of a century ago, this was the first flow to reach the sea in nearly two decades. The pulse flow was significant in that it resulted from an international agreement, Minute 319, which allowed Colorado River water to be used for environmental restoration. Here we present a historical perspective of channel change and the results of geomorphic and sediment transport monitoring during the pulse flow between Yuma, Arizona and San Luis Rio Colorado, Sonora. This reach is known as the Limitrophe, because the river channel is the legal border between the United States and Mexico. Peak discharge of the pulse flow was 120 m3/s at Morelos Dam, but decreased to 71 m3/s at the southern border because of infiltration losses to the dry streambed. In contrast, flood flows in the 1980s and 1990s peaked above 600 m3/s at the southern border, and high flows above 200 m3/s were common. The sustained high flows in the 1980s caused widening and reworking of the river channel downstream through the delta. In the Limitrophe, flooding in 1993 from the Gila River basin dissected the 1980s flood surfaces, and smaller floods in the late 1990s incised the modern “active” channel within these higher surfaces. Field observations show that most geomorphic change during the pulse flow was confined to this pre-pulse, active channel. Relatively little bank erosion was evident, particularly in upstream reaches where vegetation is most dense, but new sandbars formed in areas of flow expansion. Farther downstream, localized bed scour and deposition ranged from 10s of centimeters to more than a meter, and fluvial dunes aggraded the bed in several locations. Measurable suspended-sediment transport occurred throughout the Limitrophe. Sediment concentrations peaked during the rising limb, and suspended sand concentrations suggest deposition in the lower 7 km of the Limitrophe as the channel gradient decreases by an order of magnitude. The pulse flow was small compared to historic floods, and flood magnitudes greater than the 2014 pulse flow are therefore necessary to significantly rework stable geomorphic surfaces or induce channel widening.

Climate and local geomorphic interactions drive patterns of riparian forest decline along a Mediterranean Basin river

NASA Astrophysics Data System (ADS)

Stella, John C.; Riddle, Jess; Piégay, Hervé; Gagnage, Matthieu; Trémélo, Marie-Laure

2013-11-01

Dynamic fluvial processes strongly influence ecological communities and ecosystem health in riverine and riparian ecosystems, particularly in drought-prone regions. In these systems, there is a need to develop tools to measure impacts from local and regional hydrogeomorphic changes on the key biological and physical processes that sustain riparian ecosystem health and potential recovery. We used dendrochronology of Populus nigra, a riparian tree that is vulnerable to changes in local hydrology, to analyze ecosystem response following channel incision due to gravel mining along the Drôme River, a Mediterranean Basin stream in southern France. We cored 55 trees at seven floodplain sites, measured ring widths, and calculated basal area growth to compare the severity and timing of local growth decline along the river. Current basal area increment (BAI) growth per tree ranged almost 10-fold among sites (7.7 ± 1.3 to 63.9 ± 15.2 cm2 year- 1, mean ± SE) and these differences were significant. Mean BAI was correlated positively with the proportion of healthy trees at a site, and negatively with proportion of dead canopy area. Regime shift analysis of the tree-ring series indicates that tree growth declined significantly at four sites since 1978, coincident with documented channel incision. In addition, patterns of low growth and crown dieback are consistent with stress due to reduced water supply. The most impaired sites were not directly adjacent to local mining pits visible on aerial photographs, nor did the sequence of growth regime shifts suggest a pattern of channel incision progressing from these areas. The initiation of site growth declines was most typically associated with drought years, and the most impaired sites were spatially distributed to suggest the influence of local bedrock controls on soil depth. Climate in the Drôme basin and in the Mediterranean region is trending significantly toward hotter growing seasons with a decrease in summer river discharge, and this will increase both chronic and acute water shortage for riparian trees. This study shows that drought-prone riparian forests are vulnerable to hydrogeomorphological changes, but the severity of impacts is conditioned by interactions between drivers at different scales, including regional climate variability, reach-based geomorphic alteration, and local lithological controls.

A landscape scale valley confinement algorithm: Delineating unconfined valley bottoms for geomorphic, aquatic, and riparian applications

Treesearch

David E. Nagel; John M. Buffington; Sharon L. Parkes; Seth Wenger; Jaime R. Goode

2014-01-01

Valley confinement is an important landscape characteristic linked to aquatic habitat, riparian diversity, and geomorphic processes. This report describes a GIS program called the Valley Confinement Algorithm (VCA), which identifies unconfined valleys in montane landscapes. The algorithm uses nationally available digital elevation models (DEMs) at 10-30 m resolution to...

Synergies between geomorphic hazard and risk and sediment cascade research fields: exploiting geomorphic processes' susceptibility analyses to derive potential sediment sources in the Oltet, river catchment, southern Romania

NASA Astrophysics Data System (ADS)

Jurchescu, Marta-Cristina

2015-04-01

Identifying sediment sources and sediment availability represents a major problem and one of the first concerns in the field of sediment cascade. This paper addresses the on-site effects associated with sediment transfer, investigating the degree to which studies pertaining to the field of geomorphic hazard and risk research could be exploited in sediment budget estimations. More precisely, the paper investigates whether results obtained in assessing susceptibility to various geomorphic processes (landslides, soil erosion, gully erosion) could be transferred to the study of sediment sources within a basin. The study area is a medium-sized catchment (> 2400 km2) in southern Romania encompassing four different geomorphic units (mountains, hills, piedmont and plain). The region is highly affected by a wide range of geomorphic processes which supply sediments to the drainage network. The presence of a reservoir at the river outlet emphasizes the importance of estimating sediment budgets. The susceptibility analyses are conducted separately for each type of the considered processes in a top-down framework, i.e. at two different scales, using scale-adapted methods and validation techniques in each case, as widely-recognized in the hazard and risk research literature. The analyses start at a regional scale, which has in view the entire catchment, using readily available data on conditioning factors. In a second step, the suceptibility analyses are carried out at a medium scale for selected hotspot-compartments of the catchment. In order to appraise the extent to which susceptibility results are relevant in interpreting sediment sources at catchment scale, scale-induced differences are analysed in the case of each process. Based on the amount of uncertainty revealed by each regional-scale analysis in comparison to the medium-scale ones, decisions are made on whether the first are acceptable to the aim of identifying potential sediment source areas or if they should be refined using more precise methods and input data. The three final basin-wide susceptibility maps are eventually coverted, on a threshold basis, to maps showing the potential areas of sediment production by landslides, soil erosion and gully erosion respectively. These are then combined into one single map of potential sediment sources. The susceptibility assessments indicate that the basin compartments most prone to landslides and soil erosion correspond to the Subcarpathian hills, while the one most threatened by gully erosion corresponds to the piedmont relief. The final map of potential sediment sources shows that approximately 34% of the study catchment is occupied by areas potentially generating sediment through landslides and gully erosion, extending over most of the high piedmont and Subcarpathian hills. The results prove that there is an important link between the two research fields, i.e. geomorphic hazard and risk and sediment cascade, by allowing the transfer of knowledge from geomorphic processes' susceptibility analyses to the estimation of potential sediment sources within catchments. The synergy between the two fields raises further challenges to be tackled in future (e.g. how to derive sediment transfer rates from quantitative hazard estimates).

Sapping Features of the Colorado Plateau: a Comparative Planetary Geology Field Guide

NASA Technical Reports Server (NTRS)

Howard, Alan D. (Editor); Kochel, R. Craig (Editor); Holt, Henry E. (Editor)

1987-01-01

This book is an attempt to determine geomorphic criteria to be used to distinguish between channels formed predominantly by sapping and seepage erosion and those formed principally by surface runoff processes. The geologic nature of the Colorado Plateau has resulted in geomorphic features that show similarities to some areas on Mars, especially certain valley networks within thick sandstone formations. Where spring sapping is an effective process, the valleys that develop are unique in terms of their morphology and network pattern.

Channel morphology and bed-sediment characteristics before and after riparian vegetation clearing in the Cottonwood Ranch, Platte River, Nebraska, water years 2001-2004

USGS Publications Warehouse

Kinzel, Paul J.; Nelson, Jonathan M.; Heckman, Ashley K.

2006-01-01

Riparian areas along a reach of Platte River passing through Nebraska Public Power District's Cottonwood Ranch Property were modified during 2002 to 2004 to enhance in-channel habitats for endangered and threatened avian species. A component of this alteration involved the removal of riparian vegetation from riverbanks and islands to provide roosting habitat for the endangered whooping crane and to provide nesting and foraging habitat for the endangered least tern and threatened piping plover. It was hypothesized that the removal of riparian vegetation could have the effect of stimulating channel widening in this reach by increasing the potential of these surfaces to erode under natural fluvial action. It also was hypothesized that as a direct or indirect consequence of the alterations, a local increase in sediment supply also might occur, potentially resulting in geomorphic change downstream and possibly initiating negative third-party effects. The cumulative effects of the management activities on the channel morphology and sediment transport in this reach were monitored during water years 2001-2004 by measuring transect elevation profiles and bed-sediment-size gradations upstream, within, and downstream from the managed area before and after the development activities. An analysis of variance (ANOVA) was performed to determine if the geomorphic variables measured before and after the development activities were significantly different. Although statistically significant differences were detected in some of the variables, increases in mean bed elevation did not occur in a greater percentage of the monitoring sections measured downstream compared to upstream from the management activities. This result suggests that the management activities did not have a substantial effect on the downstream river channel morphology and sediment transport. However, it is important to place these short-term and site-specific results in the context that river flows following the management activities were at historical low rates, and therefore the potential to affect and the opportunity to detect possible geomorphic change within and downstream from the managed reach were limited.

Rivers and valleys of Pennsylvania, revisited

NASA Astrophysics Data System (ADS)

Morisawa, Marie

1989-09-01

The 1889 paper by William Morris Davis on the "Rivers and Valleys of Pennsylvania" is a landmark in the history of geomorphology. It was in this manuscript that he set forth what came to be known as the Davisian system of landscape. It is important to understand that Davis' interpretation of landforms was restricted by the geologic paradigms of his day. Uniformitarianism was strongly entrenched and Darwin's theory of evolution had become popularly accepted. The concept of the landmass Appalachia and then current theories on mountain building affected the approach that Davis took in hypothesizing the origin and development of the Folded Appalachian drainage. All of these geologic precepts influenced the formulation and explanation of his theories. In his exposition he adapted, synthesized and embellished on ideas he derived from fellow geologists such as Gilbert, Dutton, Powell, and McGee. A number of the concepts he proposed in the 1889 paper quickly became the bases for geomorphic studies by others: the cycles of river erosion and landscape evolution and the peneplain (here called base level erosion). The cycle of erosion became the model for subsequent geomorphic analyses, and peneplain hunting became a popular sport for geomorphologists. Davis' hypothesis of the origin and development of Pennsylvanian drainage stimulated subsequent discussion and further hypotheses by others. In fact, many of the later theories were refinements and/or elaborations of ideas mentioned in this paper of Davis. He proposed the origin of the drainage as consequent streams, then antecedence, superposition, headward extension of divides by piracy, erosion along lines of weaknesses (faults, easily erodible beds) through resistant ridges and normal fluvial erosion. Thus, the hypotheses of regional superposition (Johnson), extended consequents (Ruedemann), consequents and local superposition (Meyerhoff and Olmstead), the utilization of structural weaknesses in development of transverse drainage (Thompson; Meyerhoff; Oberlander, among others), and migration of divides (Thompson), all had been suggested by Davis in 1889. Although the concepts of erosion cycles and peneplaination have waned in popularity in recent geomorphic research, the principles of formation of water and wind gaps, headward migration of divides, stream piracy and adjustment to streams to structure, so clearly and minutely explained in his 1889 publication, are still viable today.

Constraints on the topographic evolution of Corsica and Sardinia from geological and geomorphic analyses

NASA Astrophysics Data System (ADS)

Quye-Sawyer, Jennifer; Whittaker, Alexander; Roberts, Gareth; Rood, Dylan

2017-04-01

The western Mediterranean Sea and its surroundings form part of a well-studied region whose geodynamic history is broadly known. However, how the topography of this area has responded to its tectonic and geodynamic influences is not fully understood. In particular, the relative importance of convergent, extensional and dynamic process is not known. Here we focus on the islands of Corsica, France, and Sardinia, Italy, which have played an important role in Alpine-Apennine system. They experienced a similar kinematic history during the Cenozoic, however their different positions on the Tethyan margin allow the relative effects of Alpine collision and rates of back-arc stretching to be compared. In particular, the two stages of back-arc extension (Liguro-Provençal basin to the west and Tyrrhenian Sea on the east) can provide information about how rollback-induced extension developed with time from the late Oligocene to the present. The two islands are historically tectonically quiescent, however they still preserve evidence of collision and subsequent extension from slab roll-back. In this study we have used a combination of geological and geomorphic techniques to provide new constraints into the vertical motions of Corsica and Sardinia. To quantify the spatial and temporal landscape evolution we have integrated stratigraphic, structural and thermochronological data and re-evaluated these alongside present-day geomorphic and geophysical observations. In addition, we have used digital elevation models to acquire 2030 fluvial longitudinal profiles for both islands. Knickpoints identified on these longitudinal profiles have been compared to geological maps to test the influence of rock strength on erosion. Our analysis reveals the presence of non-lithologically controlled knickpoints which we interpret to have been created by Miocene to Recent changes in uplift rate of the landscape. The longitudinal profiles were subsequently used in drainage inversion modelling, whose results show a spatially and temporally variable evolution of topography. Our results show that the initiation of normal fault bounded sedimentary basins, and the evolution from terrestrial to marine environments, is in agreement with progressive extension with eastward directed slab roll-back. However, observations including angular unconformities alongside terrestrial sedimentation and basalt eruptions during the Pliocene, imply basin inversion and uplift that is broadly simultaneous across both islands from the late Miocene. The magnitude of this uplift was probably variable, reaching several hundred metres in north-central Sardinia. Extension then recommenced as normal faults offset Pliocene units in Sardinia. Many of the islands' major faults have pronounced triangular facets with thick Quaternary alluvium in the hangingwall. Several knickpoints may relate to these fault movements. We evaluate potential causes of the landscape development and we suggest our data are consistent with long-lived tectonic processes in a migrating back-arc since the Oligocene, with minor inversion and uplift to expose the Miocene marine basins.

Influence of Fault-Controlled Topography on Fluvio-Deltaic Sedimentary Systems in Eberswalde Crater, Mars

NASA Technical Reports Server (NTRS)

Rice, Melissa S.; Gupta, Sanjeev; Bell, James F., III; Warner, Nicholas H.

2011-01-01

Eberswalde crater was selected as a candidate landing site for the Mars Science Laboratory (MSL) mission based on the presence of a fan-shaped sedimentary deposit interpreted as a delta. We have identified and mapped five other candidate fluvio -deltaic systems in the crater, using images and digital terrain models (DTMs) derived from the Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX). All of these systems consist of the same three stratigraphic units: (1) an upper layered unit, conformable with (2) a subpolygonally fractured unit, unconformably overlying (3) a pitted unit. We have also mapped a system of NNE-trending scarps interpreted as dip-slip faults that pre-date the fluvial -lacustrine deposits. The post-impact regional faulting may have generated the large-scale topography within the crater, which consists of a Western Basin, an Eastern Basin, and a central high. This topography subsequently provided depositional sinks for sediment entering the crater and controlled the geomorphic pattern of delta development.

Large wood in the Snowy River estuary, Australia

NASA Astrophysics Data System (ADS)

Hinwood, Jon B.; McLean, Errol J.

2017-02-01

In this paper we report on 8 years of data collection and interpretation of large wood in the Snowy River estuary in southeastern Australia, providing quantitative data on the amount, sources, transport, decay, and geomorphic actions. No prior census data for an estuary is known to the authors despite their environmental and economic importance and the significant differences between a fluvial channel and an estuarine channel. Southeastern Australian estuaries contain a significant quantity of large wood that is derived from many sources, including river flood flows, local bank erosion, and anthropogenic sources. Wind and tide are shown to be as important as river flow in transporting and stranding large wood. Tidal action facilitates trapping of large wood on intertidal bars and shoals; but channels are wider and generally deeper, so log jams are less likely than in rivers. Estuarine large wood contributes to localised scour and accretion and hence to the modification of estuarine habitat, but in the study area it did not have large-scale impacts on the hydraulic gradients nor the geomorphology.

Lunar and Planetary Science XXXV: Mars: Wind, Dust Sand, and Debris

NASA Technical Reports Server (NTRS)

2004-01-01

The session "Mars: Wind, Dust Sand, and Debris" included: Mars Exploration Rovers: Laboratory Simulations of Aeolian Interactions; Thermal and Spectral Analysis of an Intracrater Dune Field in Amazonis Planitia; How High is that Dune? A Comparison of Methods Used to Constrain the Morphometry of Aeolian Bedforms on Mars; Dust Devils on Mars: Scaling of Dust Flux Based on Laboratory Simulations; A Close Encounter with a Terrestrial Dust Devil; Interpretation of Wind Direction from Eolian Features: Herschel Crater, Mars Erosion Rates at the Viking 2 Landing Site; Mars Dust: Characterization of Particle Size and Electrostatic Charge Distributions; Simple Non-fluvial Models of Planetary Surface Modification, with Application to Mars; Comparison of Geomorphically Determined Winds with a General Circulation Model: Herschel Crater, Mars; Analysis of Martian Debris Aprons in Eastern Hellas Using THEMIS; Origin of Martian Northern Hemisphere Mid-Latitude Lobate Debris Aprons; Debris Aprons in the Tempe/Mareotis Region of Mars;and Constraining Flow Dynamics of Mass Movements on Earth and Mars.

Discussion on Ubeid, K.A., 2016. Quaternary alluvial deposits of Wadi Gaza in the middle of the Gaza Strip (Palestine): Facies, granulometric characteristics, and their paleoflow direction. JAES 118: 274-283

NASA Astrophysics Data System (ADS)

Roskin, Joel

2017-10-01

The location of the Gaza Strip at the southeastern corner of the Mediterranean Sea along a transition zone between Mediterranean and arid climate zones at the meeting point between fluvial, coastal, and aeolian sediments makes the Strip an important region for Quaternary, hydrogeologic, geomorphic, and palaeoclimatic studies (Aish, 2004). Wadi Gaza, the only water course that fully crosses the Gaza Strip into the southeastern Mediterranean Sea is an important water source for the proliferating and dense population of the Gaza Strip (Zaineldeen and Aish, 2012), is an indispensable part of natural life in Gaza and has an interesting history and rich vegetation (Abd Rabou et al., 2016). As such, the hydrogeologic conditions of Wadi Gaza need to be fully resolved. This includes the study of the wadi's palaeohydrology and the current anthropogenic impact upon flow and deposition along the watercourse.

Active tectonics in the Mygdonia basin (northern Greece): a combined seismological and remote-sensed geomorphology approach

NASA Astrophysics Data System (ADS)

Gkarlaouni, Charikleia; Andreani, Louis; Pennos, Chris; Gloaguen, Richard; Papadimitriou, Eleftheria; Kilias, Adamantios; Michail, Maria

2014-05-01

In Greek mainland, active extensional deformation resulted in the development of numerous seismogenic E- to SE-trending basins. The Mygdonia graben located in central Macedonia produced major historical earthquakes and poses a serious threat to the neighbouring city of Thessaloniki. Our aim is to determine which active seismic sources have the potential to generate strong events. Active tectonics shape the landscape, control the evolution of the fluvial network and cause the occurrence of strong and frequent earthquakes generated by fault populations. Thus, our approach combined both seismology and remote-sensed geomorphology. Seismological investigation and more especially relocation analysis was performed for recent seismicity in the area (2000-2012). Low magnitude earthquakes not exceeding 4.8 constitute the seismicity pattern for this period. Accurately determined focal parameters indicate that seismicity is not only localized along major fault zones. Smaller faults seem also to be activated. Temporal and spatial investigation show that seismicity is clustered and seismic bursts often migrate to adjacent faults. The hypocentral distribution of precisely determined microearthquake foci reveals the existence of high-angle (> 60º) normal faults dipping both south and north. This is consistent with fault plane solutions of stronger earthquakes. The largest amount of earthquakes is generated along the NW-SE sub-basin bounded from "Assiros-Analipsi" and "Lagina" fault zone, as well as in "Sochos" fault in the north which dips with approximately 70º-80º to the south. All these structures played an important role in the seismotectonic evolution of the area. We used geomorphic indices in order to analyse the landscapes of the Mygdonia region. Geomorphic indices were derived from DEM and computed using MATLAB scripts. We classified the landscapes according to their erosional stages using hypsometric integral and surface roughness. Both indices suggest stronger erosion along the southern flank of the Mygdonia graben. Observed differences may be related to a diachronic evolution. River profiles crossing the Thessaloniki-Gerakarou fault system (TGFS) south of the Mygdonia basin display anomalies such as knickpoints or convex segments. These anomalies reflect significant changes in river base-levels possibly triggered by uplift/subsidence processes. We also computed the normalized steepness index (ksn) for concave segments in rivers. We observe an increase of ksn values towards the south while the lithology remains almost constant. These changes in ksn values may be thus related to an increase in deformation rates along the southern TGFS. Our geomorphic analysis also highlighted several flat paleo-surfaces located on top of main ranges at elevations comprised between 300 and 450m above the basin infill. Finally, we produced thematic maps combining present-day seismicity, historical earthquakes and geomorphic features derived from DEM. The combined use of both seismology and remote-sensed geomorphology allowed us to better understand the at-depth and surface expressions of active structures within the Mygdonia basin. It also provided further insights into the tectonic evolution of the study area. This project is funded by the German Academic Exchange Service (DAAD) and the Greek State Scholarschips Foundation (IKY) under the IKYDA initiative.

Spatial and temporal variations in the sediment state of North American dune fields

NASA Astrophysics Data System (ADS)

Halfen, Alan F.; Lancaster, Nicholas; Wolfe, Stephen

2015-04-01

This research evaluates geomorphic and chronologic data from the INQUA Dune Atlas for three areas of North America: 1) the Prairie, Parkland and Boreal ecozones of the northern Great Plains in Canada; 2) the Central Great Plains of the USA; and 3) the deserts of southwestern USA and northern Mexico. Chronometric data for periods of dune activity and stability are compared with palaeoenvironment reconstructions to assess dune system response to changes in sediment supply, availability, and mobility. Dune fields in the northern Great Plains were formed from glaciofluvial or glaciolacustrine sediments deposited during deglaciation 16-11 ka. Subsequent aeolian deposition occurred in Parkland and Prairie dune fields as a result of mid-Holocene (8-5 ka) and late-Holocene (< 3.5 ka) activity related to drought conditions. In the Central Great Plains, many dune fields are closely linked to fluvial sediment sources. Sediment supply was high in these dune fields during deglaciation of the Rocky Mountains and resulted in widespread dune construction 16-10 ka. Multiple periods of Holocene reactivation are recorded and reflect increased sediment availability during drought episodes. Dune fields in the southwestern deserts experienced periods of construction as a result of enhanced supply of sediment from fluvial and lacustrine sources during the period 11.8 - 8 ka and at short but repeated intervals during the late Holocene. Despite spatial and temporal gaps in chronometric data, the record from North American dune fields indicates the strong influence of sediment supply on dune construction, with changes in sediment availability, as a result of drought, being the primary driver of dune activity during the Holocene.

The source of naturally occurring arsenic in a coastal sand aquifer of eastern Australia.

PubMed

O'Shea, Bethany; Jankowski, Jerzy; Sammut, Jesmond

2007-07-01

The discovery of dissolved arsenic in a coastal aquifer used extensively for human consumption has led to widespread concern for its potential occurrence in other sandy coastal environments in eastern Australia. The development of an aquifer specific geomorphic model (herein) suggests that arsenic is regionally derived from erosion of arsenic-rich stibnite (Sb(2)S(3)) mineralisation present in the hinterland. Fluvial processes have transported the eroded material over time to deposit an aquifer lithology elevated in arsenic. Minor arsenic contribution to groundwater is derived from mineralised bedrock below the unconsolidated aquifer. An association with arsenic and pyrite has been observed in the aquifer in small discrete arsenian pyrite clusters rather than actual acid sulfate soil horizons. This association is likely to influence arsenic distribution in the aquifer, but is not the dominant control on arsenic occurrence. Arsenic association with marine clays is considered a function of their increased adsorptive capacity for arsenic and not solely on the influence of sea level inundation of the aquifer sediments during the Quaternary Period. These findings have implications for, but are not limited to, coastal aquifers. Rather, any aquifer containing sediments derived from mineralised provenances may be at risk of natural arsenic contamination. Groundwater resource surveys should thus incorporate a review of the aquifer source provenance when assessing the likely risk of natural arsenic occurrence in an aquifer.

The Modification of Mars Fluvial Surfaces

NASA Technical Reports Server (NTRS)

Bourke, M. C.; Zimbelman, J. R.; Finnegan, D.; Banerdt, B.

2001-01-01

The identification of fluvial deposits on Mars is impaired by modifying geological processes. An analysis of surface patterns of superimposed dunes and channels in paleoflood environments in Washington State and Australia can yield information on buried surfaces. Additional information is contained in the original extended abstract.

Volcanic or Fluvial Channels on Ascraeus Mons: Focus on the Source Area of Sinuous Channels on the Southeast Rift Apron

NASA Astrophysics Data System (ADS)

Signorella, J. D.; de Wet, A. P.; Bleacher, J. E.; Collins, A.; Schierl, Z. P.; Schwans, B.

2012-03-01

This study focuses on the source area of sinuous channels on the southeast rift apron on Ascraeus Mons, Mars and attempts to understand whether the channels were formed through volcanic or fluvial processes.

(dis)connectivity in Catchment-Scale Sediment Cascades: Forecasting Responses in Sediment Flux Associated with Various Forms of Environmental Change

NASA Astrophysics Data System (ADS)

Fryirs, K.

2010-12-01

Fluvial systems are key elements that drive Earth surface change because they convey most of the global fluxes of water and sediment from land to oceans. Fluvial fluxes of water and sediment also drive a significant proportion of the terrestrial biochemical cycling of carbon, nutrients and pollutants. Understanding the internal dynamics of the sediment cascade is therefore critical to forecasting how environmental change, whether driven by extrinsic climate change, or intrinsic human-disturbance, might affect biochemical fluxes. To understand the internal dynamics of sediment flux requires a framework that can incorporate the various processes involved in the movement of sediment from the source area through the basin system to the outlet, and can take account of spatial variability within the system and the timeframes over which these processes operate. Traditionally a sediment budget approach has been used to quantify the sediment being supplied, transported and stored in various parts of catchments. In more recent years, a more sophisticated approach to analysis of catchment linkages and (dis)connectivity has been developed that incorporates both spatial and temporal variability in the operation of the sediment cascade. This framework is based on an understanding of longitudinal, lateral and vertical linkages in sediment flux in catchments, and where blockages occur to disrupt these linkages. These blockages have been termed buffers, barriers and blankets (Fryirs et al 2007). Depending on the position of these blockages, and their sediment residence time, various parts of catchment may be actively contributing sediment to the catchment sediment cascade and be switched on, or inactive and switched off. The degree of spatial connectivity determines the effective catchment area. The breaching capacity of buffers, barriers and blankets determines the effective timescale over which certain parts of a catchment are switched on. The sediment residence time and thresholds of stability dictate the timeframe over which certain parts of catchments are actively contributing sediment to the cascade. The manifestation of geomorphic change, and response times to disturbance can be modeled within such a framework. The notion that certain sediment sources and transport mechanisms may be switched on or switched off under various climate change scenarios can also be examined using this framework. Fryirs, K., Brierley, G. J., Preston, N. J. and Kasai, M. 2007. Buffers, barriers and blankets: The (dis)connectivity of catchment-scale sediment cascades. Catena, 70, 49-67

Don't fight the site: three geomorphic considerations in catchment-scale river rehabilitation planning.

PubMed

Brierley, Gary; Fryirs, Kirstie

2009-06-01

Three geomorphic considerations that underpin the design and implementation of realistic and strategic river conservation and rehabilitation programs that work with the nature are outlined. First, the importance of appreciating the inherent diversity of river forms and processes is discussed. Second, river dynamics are appraised, framing the contemporary behavioral regime of a reach in relation to system evolution to explain changes to river character and behavior over time. Third, the trajectory of a reach is framed in relation to downstream patterns of river types, analyzing landscape connectivity at the catchment scale to interpret geomorphic river recovery potential. The application of these principles is demonstrated using extensive catchment-scale analyses of geomorphic river responses to human disturbance in the Bega and Upper Hunter catchments in southeastern Australia. Differing implications for reach- and catchment-scale rehabilitation planning prompt the imperative that management practices work with nature rather than strive to 'fight the site.'

Ancient fluvial processes in the equatorial highlands of Mars

NASA Technical Reports Server (NTRS)

Craddock, Robert A.; Maxwell, Ted A.

1991-01-01

Martian highland craters typically lack ejecta deposits, have no noticeable rim, and are flat floored. In addition, crater size frequency distribution curves show that highland craters have depleted populations less than 20 km in diameter. A variety of processes have been suggested to explain these observations including deposition of aeolian or volcanic materials up to the crater rim crests, thermal creep, terrain softening, and mass wasting. However, none of these processes adequately explains both the crater morphology and population distribution. In order to explain both the Martian highland crater morphology and population distribution, a fluvial process is proposed which is capable of removing the loose crater rim material. The resulting effect is to decrease the crater diameter, thereby causing the population curves to bendover. The eroded material is redistributed, burying or partially burying smaller diameter craters before complete erosion. This material may also be deposited into local topographic lows, creating the depositional basins observed. A fluvial process explains both sets of observations: crater morphology and crater population distribution curves.

Development and Application of Flow Duration Curves for Stream Restoration

DTIC Science & Technology

2016-02-01

hydrograph (TNC 2009). Colorado State University’s GeoTools offers an FDC computation focusing on the geomorphic implications of hydrology (Bledsoe...processes • Assessment of changes in stream metabolism using temperature duration curves • Evaluation of pollutant or contaminant transport using...major concern associated with stream restoration projects, due to the many chemical, ecological, and geomorphic advantages a robust riparian buffer

The Geomorphic Road Analysis and Inventory Package (GRAIP) Volume 2: Office Procedures

Treesearch

Richard M. Cissel; Thomas A. Black; Kimberly A. T. Schreuders; Ajay Prasad; Charles H. Luce; David G. Tarboton; Nathan A. Nelson

2012-01-01

An important first step in managing forest roads for improved water quality and aquatic habitat is the performance of an inventory. The Geomorphic Roads Analysis and Inventory Package (GRAIP) was developed as a tool for making a comprehensive inventory and analysis of the effects of forest roads on watersheds. This manual describes the data analysis and process of a...

Geomorphic effectiveness of a long profile shape and the role of inherent geological controls in the Himalayan hinterland area of the Ganga River basin, India

NASA Astrophysics Data System (ADS)

Sonam; Jain, Vikrant

2018-03-01

Long profiles of rivers provide a platform to analyse interaction between geological and geomorphic processes operating at different time scales. Identification of an appropriate model for river long profile becomes important in order to establish a quantitative relationship between the profile shape, its geomorphic effectiveness, and inherent geological characteristics. This work highlights the variability in the long profile shape of the Ganga River and its major tributaries, its impact on stream power distribution pattern, and role of the geological controls on it. Long profile shapes are represented by the sum of two exponential functions through the curve fitting method. We have shown that coefficients of river long profile equations are governed by the geological characteristics of subbasins. These equations further define the spatial distribution pattern of stream power and help to understand stream power variability in different geological terrains. Spatial distribution of stream power in different geological terrains successfully explains spatial variability in geomorphic processes within the Himalayan hinterland area. In general, the stream power peaks of larger rivers lie in the Higher Himalaya, and rivers in the eastern hinterland area are characterised by the highest magnitude of stream power.

Gully evolution and geomorphic adjustments of badlands to reforestation

PubMed Central

Ballesteros Cánovas, J. A.; Stoffel, M.; Martín-Duque, J. F.; Corona, C.; Lucía, A.; Bodoque, J. M.; Montgomery, D. R.

2017-01-01

Badlands and gullied areas are among those geomorphic environments with the highest erosion rates worldwide. Nevertheless, records of their evolution and their relations with anthropogenic land transformation are scarcer. Here we combine historical data with aerial photographs and tree-ring records to reconstruct the evolution of a badland in a Mediterranean environment of Central Spain. Historical sources suggest an anthropogenic origin of this badland landscape, caused by intense quarrying activities during the 18th century. Aerial photographs allowed detection of dramatic geomorphic changes and the evolution of an emerging vegetation cover since the 1960s, due to widespread reforestation. Finally, tree-ring analyses of exposed roots allowed quantification of recent channel incision of the main gully, and sheet erosion processes. Our results suggest that reforestation practices have influenced the initiation of an episode of incision in the main channel in the 1980s, through the hypothesized creation of disequilibrium in water-sediment balance following decoupling of hillslopes from channel processes. These findings imply an asymmetry in the geomorphic response of badlands to erosion such that in the early evolution stages, vegetation removal results in gullying, but that reforestation alone does not necessarily stabilize the landforms and may even promote renewed incision. PMID:28327591

Modeling In-Stream Hydro-Geomorphic Processes After 2012 Waldo Canyon Fire, Colorado

NASA Astrophysics Data System (ADS)

Nourbakhshbeidokhti, S.; Kinoshita, A. M.; Chin, A.

2016-12-01

Wildfires can have significant impacts on hydrologic and geomorphic processes. Post-fire sediment transport and runoff generation vary by burn severity, precipitation, and vegetation. A need exists to understand these variable relationships and improve parameterization of post-fire hydro-geomorphic models. This research aims to model pre-fire geomorphic and hydrologic processes in Williams Canyon, a watershed burned by the 2012 Waldo Canyon Fire in Colorado. We develop the KINematic Runoff and EROSion (KINEROS) model with Geographical Information System (GIS)-based information, including a Digital Elevation Model, land cover, soil classification, precipitation, and soil burn severity for a local reference watershed that is unburned. We transfer these parameters to a channel reach in Williams Canyon (Williams Downstream) and adjust them toward post-fire conditions. We model runoff and sediment yield for several storms following the fire. Three post-fire terrestrial Light Detection and Ranging (LiDAR) images (21 April 2013, 14 September 2013, and 16 September 2014) are used to estimate total erosion and deposition at the reach scale. We use the LiDAR-based information to calibrate the post-fire model. Preliminary modeling results indicate 3870-125 kg/ha of sediment in the Williams Downstream reach. The uncalibrated model overestimated (410% in the first year) and underestimated (87.2% in the second year) the erosion. Model calibration reduced the Root Mean Square Error (RMSE) of sediment to 0.016% for the first year and 0.09% for the second year. The parameters calibrated for the Williams Downstream channel reach will be used to develop models for seven other channel reaches within the area burned by the Waldo Canyon Fire, where the performance can be evaluated with LiDAR estimates. Results of this research will enhance our understanding of wildfire disturbance on coupled hydrologic and geomorphic processes. Findings will also improve model parameterization that can be used to guide post-fire management and predictions.

Forecasting the response of Earth's surface to future climatic and land use changes: A review of methods and research needs

DOE PAGES

Pelletier, Jon D.; Murray, A. Brad; Pierce, Jennifer L.; ...

2015-07-14

In the future, Earth will be warmer, precipitation events will be more extreme, global mean sea level will rise, and many arid and semiarid regions will be drier. Human modifications of landscapes will also occur at an accelerated rate as developed areas increase in size and population density. We now have gridded global forecasts, being continually improved, of the climatic and land use changes (C&LUC) that are likely to occur in the coming decades. However, besides a few exceptions, consensus forecasts do not exist for how these C&LUC will likely impact Earth-surface processes and hazards. In some cases, we havemore » the tools to forecast the geomorphic responses to likely future C&LUC. Fully exploiting these models and utilizing these tools will require close collaboration among Earth-surface scientists and Earth-system modelers. This paper assesses the state-of-the-art tools and data that are being used or could be used to forecast changes in the state of Earth's surface as a result of likely future C&LUC. We also propose strategies for filling key knowledge gaps, emphasizing where additional basic research and/or collaboration across disciplines are necessary. The main body of the paper addresses cross-cutting issues, including the importance of nonlinear/threshold-dominated interactions among topography, vegetation, and sediment transport, as well as the importance of alternate stable states and extreme, rare events for understanding and forecasting Earth-surface response to C&LUC. Five supplements delve into different scales or process zones (global-scale assessments and fluvial, aeolian, glacial/periglacial, and coastal process zones) in detail.« less

Power of Streams and Power of Management: How Community and Fluvial Science Work Together for Massachusetts Rivers

NASA Astrophysics Data System (ADS)

Hatch, C. E.; Mabee, S. B.; Slovin, N. B.; Vogel, E.; Gartner, J. D.; Gillett, N.; Warner, B. P.

2015-12-01

In the Northeastern U.S., the most costly damages from intense storm events were impacts to road-stream crossings. In steep post-glacial terrain, erosion by floodwater and entrained sediment is the largest destructive force during intense storms, and the most likely driver of major morphological changes to riverbanks and channels. Steam power analysis is a tool that can successfully quantify floodwater energy that caused damage afterward, however, prediction of which reaches or watersheds may experience future impacts remains uncertain. We must better determine how states with thousands of river miles may better prioritize flood mitigation studies, crossing replacements, or other infrastructure upgrades for future flood resilience within resource constraints. This challenged us to develop a statewide-scale scientific method for screening waterways and translating the results into effective policies for river corridor management. Here we present a method based on stream power analysis using widely-available 10-m DEMs and stream flow data to identify locations with extreme high or low stream power values (i.e., >300 W⁄m2 or <60 W⁄m2) or abrupt changes in these values. We used this information to identify potential areas of erosion or deposition in the Deerfield River watershed in Massachusetts and Vermont, then compared it to areas where damage occurred during Tropical Storm Irene. We show that areas of increasing (with respect to distance downstream) and high stream power are prone to landslides, bank failures, and other pulse sediment inputs in flood events. These are also the focal points of wood input to rivers, which combined with increased sediment load, makes culverts in these reaches especially prone to failure. Integration of this information into state databases allows communities to prioritize and make land-use decisions that are informed by the fluvial geomorphic workings of the larger watershed, but that have powerful local implications. Outreach and educational programs focused on stream power and fluvial systems for river practitioners and politicians at all levels align communities' attitudes about their rivers and result in ecologically sound, more flood resilient policies and practices.

Geomorphic Consequences of Volcanic Eruptions in Alaska: A Review

USGS Publications Warehouse

Waythomas, Christopher F.

2015-01-01

Eruptions of Alaska volcanoes have significant and sometimes profound geomorphic consequences on surrounding landscapes and ecosystems. The effects of eruptions on the landscape can range from complete burial of surface vegetation and preexisting topography to subtle, short-term perturbations of geomorphic and ecological systems. In some cases, an eruption will allow for new landscapes to form in response to the accumulation and erosion of recently deposited volcaniclastic material. In other cases, the geomorphic response to a major eruptive event may set in motion a series of landscape changes that could take centuries to millennia to be realized. The effects of volcanic eruptions on the landscape and how these effects influence surface processes has not been a specific focus of most studies concerned with the physical volcanology of Alaska volcanoes. Thus, what is needed is a review of eruptive activity in Alaska in the context of how this activity influences the geomorphology of affected areas. To illustrate the relationship between geomorphology and volcanic activity in Alaska, several eruptions and their geomorphic impacts will be reviewed. These eruptions include the 1912 Novarupta–Katmai eruption, the 1989–1990 and 2009 eruptions of Redoubt volcano, the 2008 eruption of Kasatochi volcano, and the recent historical eruptions of Pavlof volcano. The geomorphic consequences of eruptive activity associated with these eruptions are described, and where possible, information about surface processes, rates of landscape change, and the temporal and spatial scale of impacts are discussed.A common feature of volcanoes in Alaska is their extensive cover of glacier ice, seasonal snow, or both. As a result, the generation of meltwater and a variety of sediment–water mass flows, including debris-flow lahars, hyperconcentrated-flow lahars, and sediment-laden water floods, are typical outcomes of most types of eruptive activity. Occasionally, such flows can be quite large, with flow volumes in the range of 107–109 m3. A review of the lahars generated during the 2009 eruption of Redoubt volcano will illustrate the geomorphic impacts of lahars on stream channels and riparian habitat. Although much work is needed to develop a comprehensive understanding of the geomorphic consequences of volcanic activity in Alaska, this review provides a synthesis of some of the best-studied eruptions and perhaps will serve as a starting point for future work on this topic.

Geomorphic consequences of volcanic eruptions in Alaska: A review

USGS Publications Warehouse

Waythomas, Christopher F.

2015-01-01

Eruptions of Alaska volcanoes have significant and sometimes profound geomorphic consequences on surrounding landscapes and ecosystems. The effects of eruptions on the landscape can range from complete burial of surface vegetation and preexisting topography to subtle, short-term perturbations of geomorphic and ecological systems. In some cases, an eruption will allow for new landscapes to form in response to the accumulation and erosion of recently deposited volcaniclastic material. In other cases, the geomorphic response to a major eruptive event may set in motion a series of landscape changes that could take centuries to millennia to be realized. The effects of volcanic eruptions on the landscape and how these effects influence surface processes has not been a specific focus of most studies concerned with the physical volcanology of Alaska volcanoes. Thus, what is needed is a review of eruptive activity in Alaska in the context of how this activity influences the geomorphology of affected areas. To illustrate the relationship between geomorphology and volcanic activity in Alaska, several eruptions and their geomorphic impacts will be reviewed. These eruptions include the 1912 Novarupta–Katmai eruption, the 1989–1990 and 2009 eruptions of Redoubt volcano, the 2008 eruption of Kasatochi volcano, and the recent historical eruptions of Pavlof volcano. The geomorphic consequences of eruptive activity associated with these eruptions are described, and where possible, information about surface processes, rates of landscape change, and the temporal and spatial scale of impacts are discussed.A common feature of volcanoes in Alaska is their extensive cover of glacier ice, seasonal snow, or both. As a result, the generation of meltwater and a variety of sediment–water mass flows, including debris-flow lahars, hyperconcentrated-flow lahars, and sediment-laden water floods, are typical outcomes of most types of eruptive activity. Occasionally, such flows can be quite large, with flow volumes in the range of 107–109 m3. A review of the lahars generated during the 2009 eruption of Redoubt volcano will illustrate the geomorphic impacts of lahars on stream channels and riparian habitat. Although much work is needed to develop a comprehensive understanding of the geomorphic consequences of volcanic activity in Alaska, this review provides a synthesis of some of the best-studied eruptions and perhaps will serve as a starting point for future work on this topic.

Enhancing the hydrogeological landscape (HGL) characterisation of the Greater Launceston area (GLA) through better understanding of dolerite weathering, stream water properties and a revised landscape evolution model

NASA Astrophysics Data System (ADS)

Moore, Leah; Nicholson, Allan; Cook, Wayne; Sweeney, Margaret

2014-05-01

In the Greater Launceston Area (GLA) in northern Tasmania, Australia, there is a widespread urban salinity problem with severe impacts on urban/peri-urban infrastructure in localised areas. Salinity patterns in the landscape (elevated flux to waterways; salt efflorescence at the land surface) could be related to: the underlying rock type, the thickness of regolith materials and hence the volume of the salt store, the landforms present and the amount of water passing over and through the landscape. In northern Tasmania secondary mineralogy on dolerite typically includes formation of Fe/Ca smectite phases (e.g. nontronite, saponite) and Fe-Ti oxides/sesquioxides (e.g. hematite, goethite) with some primary phases (e.g. Ca-plagioclase feldspar, augite) weathering through to a suite dominated by kaolinite clay and Fe-Ti oxides/sesquioxides. Deeply weathered profiles in the GLA have weathered to the kaolintite-clay dominant mineralogy and in places there are gibbsite/beidellite/hematite/goethite bauxites developed. Most existing salinity mapping emphasises salt manifestation over paleo-estuarine sediments of the Paleogene Tamar-Esk River system, so incorporation of deeply weathered Jurassic dolerite materials into the salt budget considerably augments the estimated potential hazard. Rapid stream surveys provide a snapshot of stream electrical conductivity (EC) over the study area at regular intervals allowing a broad evaluation of salt flux patterns in surfaces waters. Higher EC readings were obtained from selected streams draining: deeply weathered dolerite profiles (0.37 1.86 dS/m) and deeply weathered Paleogene paleo-estuarine sediments (0.49 to 1.16 dS/m). Lower values were measured on up-faulted dolerite blocks (<0.10 dS/m); moderately weathered, high relief dolerite (<0.03 dS/m), and in incised streams flowing over a rocky dolerite substrate (<0.03 dS/m). The patterns of stream EC reflect the nature of the regolith materials the streams drain, and match mapped patterns for distribution of deeply weathered Jurassic dolerite and moderately to deeply weathered bedded paleo-estuarine sediments of the Paleogene Tamar-Esk river system, some Quaternary terrace deposits along the Tamar and Esk Rivers; and some Holocene estuarine sediments. Recent geomorphic mapping has enabled development of a more comprehensive and consistent landscape evolution model that builds on existing knowledge. This model describes the influence of a progressively incising Tamar-Esk river system in response to episodic lowering of the local base level, with multiple episodes of valley widening as the river system stabilised after incision. Successive lowering events dissected earlier landforms, but locally remnant surfaces are preserved that represent former fluvial plain and terrace features. These processes were partially controlled by the structural configuration and contrasting resistance of the underlying lithologies, influencing the planform geometries of the rivers, and consequently the potential to preserve paleo-fluvial features. Because the Tamar River is an estuarine system, some of the lowermost preserved surfaces are likely to reflect marine processes (e.g. 5-7m; 10-12m ASL). The geomorphic mapping was conducted independently of the hydrogeological landscape (HGL) characterisation in the GLA, but there is strong correlation between the areas identified as having elevated salinity hazard (HGL) and newly mapped remnant surfaces in this landscape. This work complements HGL research and supports development of an increasingly rigorous evidence-based framework for GLA salinity hazard management.

Distribution of Holocene Sediment in Chesapeake Bay as Interpreted from Submarine Geomorphology of the Submerged Landforms, Selected Core Holes, Bridge Borings and Seismic Profiles

USGS Publications Warehouse

Newell, Wayne L.; Clark, Inga; Bricker, Owen

2004-01-01

Overview -- We have interpreted the geomorphology of the submerged landforms to show thick Holocene sediment that accumulated from three different sources during on-going sea level rise that began 10,000 - 12,000 years ago at the end of Pleistocene. We used a variety of subsurface data from the literature and unpublished information to document thicknesses, materials, dates and duration of processes. Although the details of the true extent and thicknesses are unknown, the deposits of different sources have affinity for particular geographic and submerged geomorphic regions of the Chesapeake Bay and its tidal tributaries. During the last Pleistocene glacial event (Wisconsian), the area now occupied by the Chesapeake Bay was exposed, sea level being about 100 m lower than present. The Susquehanna River valley extended beyond the Bay well out on the exposed Atlantic Shelf. The Susquehanna transported glacial outwash from northern Pennsylvania and New York; the glacio-fluvial deposits were graded to the edge of the continental shelf (Colman et al., 1990; Hack, 1957). Other Piedmont and Appalachian Rivers including the Potomac and James Rivers transported large volumes of sediment to confluence with the Susquehanna channel. Locally, across the encompasing coastal plain landscape, intensive headward erosion, gullies, and slope failure, generated extensive debris flows, sheet wash, and terraces of braided alluvial channel deposits. Large volumes of sediment were moved through the river system to the continental shelf. This was accomplished by a cold, wet climate that included much freezing and thawing; steep eroding slopes resulted from the lowering of sea level from the previous high stand (Stage 5e) between glacial events. Across the Delmarva peninsula extensive wind-blown deposits of sand and loess were recycled onto low terraces and uplands from the unvegetated glacio-fluvial sediments moving through the system (Denny et al., 1979). The volume and distribution of sediment eroded and transported from the watershed surrounding the area of the Bay was several orders of magnitude greater than generally observed in transport and storage on the present day landscape.

Luminescence profiling of loess-dominated archaeological layers of a Chalcolithic site, Northern Negev Desert fringe, Israel

NASA Astrophysics Data System (ADS)

López, Gloria I.; Roskin, Joel; Bee'ri, Ron

2017-04-01

This study applies a pulsed-photon Portable OSL Reader (PPSL) in investigating the palaeoenviroment and stages of development of a Chalcolithic site revealed during a salvage excavation. The (Shoqet Junction) site, within late Pleistocene loess-dominated sediment, is adjacent to the meandering and ephemeral Hebron Wadi in the Beer-Sheva Valley, at the fringe of the Northern Negev Desert (Israel). The site intermittently covers approximately 8 hectares and was exposed at 0.3 - 0.5 m depths beneath a plowed field. Five areas were excavated down to 4 meters. The site was dominated by an array of underground facilities: tunnels, (capped) shafts, walls, floors and infilled cavities were found within four main layers. The site includes a mixture of sediments: large amounts of organic material, weathered bricks, a powdery loess-like unit and thin Bk horizons. The artifact assemblage is associated with the Ghassulian culture. The objectives of this multi-parameter study, which combines PPSL luminescence profiling with sedimentological and geomorphic analyses, are to (1) analyze the Chalcolithic palaeoenvironments, aeolian and fluvial processes and location and morphology of streambeds, (2) identify possible deterministic physical influences upon the occupations (3) decipher the natural stratigraphic archive and discriminate between human and natural (aeolian/fluvial) induced sedimentation (4) create relative age profiles based on portable OSL measurements and OSL ages, in order to minimize OSL dating. Three main sections were profiled: a natural section - in order to identify the natural sedimentological regime and two walls of two excavation squares down to the sites' alluvial base. A small section above a prominent Bk horizon was also profiled. Altogether 58 samples were obtained for sediment and PPSL analyses. Luminescence profiles in general fit the stratigraphic breaks and enable discrimination between layers. Plowed and surface loess give low reads. Inverse reads along the profile are partly understood to be due to anthropogenic intervention with the sediment. The study highlights the potential and some of the complexities involved with portable OSL profiling of multi-layer prehistoric sites.

Geospatial Characterization of Fluvial Wood Arrangement in a Semi-confined Alluvial River

NASA Astrophysics Data System (ADS)

Martin, D. J.; Harden, C. P.; Pavlowsky, R. T.

2014-12-01

Large woody debris (LWD) has become universally recognized as an integral component of fluvial systems, and as a result, has become increasingly common as a river restoration tool. However, "natural" processes of wood recruitment and the subsequent arrangement of LWD within the river network are poorly understood. This research used a suite of spatial statistics to investigate longitudinal arrangement patterns of LWD in a low-gradient, Midwestern river. First, a large-scale GPS inventory of LWD, performed on the Big River in the eastern Missouri Ozarks, resulted in over 4,000 logged positions of LWD along seven river segments that covered nearly 100 km of the 237 km river system. A global Moran's I analysis indicates that LWD density is spatially autocorrelated and displays a clustering tendency within all seven river segments (P-value range = 0.000 to 0.054). A local Moran's I analysis identified specific locations along the segments where clustering occurs and revealed that, on average, clusters of LWD density (high or low) spanned 400 m. Spectral analyses revealed that, in some segments, LWD density is spatially periodic. Two segments displayed strong periodicity, while the remaining segments displayed varying degrees of noisiness. Periodicity showed a positive association with gravel bar spacing and meander wavelength, although there were insufficient data to statistically confirm the relationship. A wavelet analysis was then performed to investigate periodicity relative to location along the segment. The wavelet analysis identified significant (α = 0.05) periodicity at discrete locations along each of the segments. Those reaches yielding strong periodicity showed stronger relationships between LWD density and the geomorphic/riparian independent variables tested. Analyses consistently identified valley width and sinuosity as being associated with LWD density. The results of these analyses contribute a new perspective on the longitudinal distribution of LWD in a river system, which should help identify physical and/or riparian control mechanisms of LWD arrangement and support the development of models of LWD arrangement. Additionally, the spatial statistical tools presented here have shown to be valuable for identifying longitudinal patterns in river system components.

Geomorphic evolution of the San Luis Basin and Rio Grande in southern Colorado and northern New Mexico

USGS Publications Warehouse

Ruleman, Chester A.; Machette, Michael; Thompson, Ren A.; Miggins, Dan M; Goehring, Brent M; Paces, James B.

2016-01-01

The San Luis Basin encompasses the largest structural and hydrologic basin of the Rio Grande rift. On this field trip, we will examine the timing of transition of the San Luis Basin from hydrologically closed, aggrading subbasins to a continuous fluvial system that eroded the basin, formed the Rio Grande gorge, and ultimately, integrated the Rio Grande from Colorado to the Gulf of Mexico. Waning Pleistocene neotectonic activity and onset of major glacial episodes, in particular Marine Isotope Stages 11–2 (~420–14 ka), induced basin fill, spillover, and erosion of the southern San Luis Basin. The combined use of new geologic mapping, fluvial geomorphology, reinterpreted surficial geology of the Taos Plateau, pedogenic relative dating studies, 3He surface exposure dating of basalts, and U-series dating of pedogenic carbonate supports a sequence of events wherein pluvial Lake Alamosa in the northern San Luis Basin overflowed, and began to drain to the south across the closed Sunshine Valley–Costilla Plain region ≤400 ka. By ~200 ka, erosion had cut through topographic highs at Ute Mountain and the Red River fault zone, and began deep-canyon incision across the southern San Luis Basin. Previous studies indicate that prior to 200 ka, the present Rio Grande terminated into a large bolson complex in the vicinity of El Paso, Texas, and systematic, headward erosional processes had subtly integrated discontinuously connected basins along the eastern flank of the Rio Grande rift and southern Rocky Mountains. We propose that the integration of the entire San Luis Basin into the Rio Grande drainage system (~400–200 ka) was the critical event in the formation of the modern Rio Grande, integrating hinterland basins of the Rio Grande rift from El Paso, Texas, north to the San Luis Basin with the Gulf of Mexico. This event dramatically affected basins southeast of El Paso, Texas, across the Chisos Mountains and southeastern Basin and Range province, including the Rio Conchos watershed and much of the Chihuahuan Desert, inducing broad regional landscape incision and exhumation.

Quantifying the influence of sediment source area sampling on detrital thermochronometer data

NASA Astrophysics Data System (ADS)

Whipp, D. M., Jr.; Ehlers, T. A.; Coutand, I.; Bookhagen, B.

2014-12-01

Detrital thermochronology offers a unique advantage over traditional bedrock thermochronology because of its sensitivity to sediment production and transportation to sample sites. In mountainous regions, modern fluvial sediment is often collected and dated to determine the past (105 to >107 year) exhumation history of the upstream drainage area. Though potentially powerful, the interpretation of detrital thermochronometer data derived from modern fluvial sediment is challenging because of spatial and temporal variations in sediment production and transport, and target mineral concentrations. Thermochronometer age prediction models provide a quantitative basis for data interpretation, but it can be difficult to separate variations in catchment bedrock ages from the effects of variable basin denudation and sediment transport. We present two examples of quantitative data interpretation using detrital thermochronometer data from the Himalaya, focusing on the influence of spatial and temporal variations in basin denudation on predicted age distributions. We combine age predictions from the 3D thermokinematic numerical model Pecube with simple models for sediment sampling in the upstream drainage basin area to assess the influence of variations in sediment production by different geomorphic processes or scaled by topographic metrics. We first consider a small catchment from the central Himalaya where bedrock landsliding appears to have affected the observed muscovite 40Ar/39Ar age distributions. Using a simple model of random landsliding with a power-law landslide frequency-area relationship we find that the sediment residence time in the catchment has a major influence on predicted age distributions. In the second case, we compare observed detrital apatite fission-track age distributions from 16 catchments in the Bhutan Himalaya to ages predicted using Pecube and scaled by various topographic metrics. Preliminary results suggest that predicted age distributions scaled by the rock uplift rate in Pecube are statistically equivalent to the observed age distributions for ~75% of the catchments, but may improve when scaled by local relief or specific stream power weighted by satellite-derived precipitation. Ongoing work is exploring the effect of scaling by other topographic metrics.

River corridor science: Hydrologic exchange and ecological consequences from bedforms to basins

USGS Publications Warehouse

Harvey, Judson; Gooseff, Michael

2015-01-01

Previously regarded as the passive drains of watersheds, over the past 50 years, rivers have progressively been recognized as being actively connected with off-channel environments. These connections prolong physical storage and enhance reactive processing to alter water chemistry and downstream transport of materials and energy. Here we propose river corridor science as a concept that integrates downstream transport with lateral and vertical exchange across interfaces. Thus, the river corridor, rather than the wetted river channel itself, is an increasingly common unit of study. Main channel exchange with recirculating marginal waters, hyporheic exchange, bank storage, and overbank flow onto floodplains are all included under a broad continuum of interactions known as “hydrologic exchange flows.” Hydrologists, geomorphologists, geochemists, and aquatic and terrestrial ecologists are cooperating in studies that reveal the dynamic interactions among hydrologic exchange flows and consequences for water quality improvement, modulation of river metabolism, habitat provision for vegetation, fish, and wildlife, and other valued ecosystem services. The need for better integration of science and management is keenly felt, from testing effectiveness of stream restoration and riparian buffers all the way to reevaluating the definition of the waters of the United States to clarify the regulatory authority under the Clean Water Act. A major challenge for scientists is linking the small-scale physical drivers with their larger-scale fluvial and geomorphic context and ecological consequences. Although the fine scales of field and laboratory studies are best suited to identifying the fundamental physical and biological processes, that understanding must be successfully linked to cumulative effects at watershed to regional and continental scales.

River corridor science: Hydrologic exchange and ecological consequences from bedforms to basins

NASA Astrophysics Data System (ADS)

Harvey, Jud; Gooseff, Michael

2015-09-01

Previously regarded as the passive drains of watersheds, over the past 50 years, rivers have progressively been recognized as being actively connected with off-channel environments. These connections prolong physical storage and enhance reactive processing to alter water chemistry and downstream transport of materials and energy. Here we propose river corridor science as a concept that integrates downstream transport with lateral and vertical exchange across interfaces. Thus, the river corridor, rather than the wetted river channel itself, is an increasingly common unit of study. Main channel exchange with recirculating marginal waters, hyporheic exchange, bank storage, and overbank flow onto floodplains are all included under a broad continuum of interactions known as "hydrologic exchange flows." Hydrologists, geomorphologists, geochemists, and aquatic and terrestrial ecologists are cooperating in studies that reveal the dynamic interactions among hydrologic exchange flows and consequences for water quality improvement, modulation of river metabolism, habitat provision for vegetation, fish, and wildlife, and other valued ecosystem services. The need for better integration of science and management is keenly felt, from testing effectiveness of stream restoration and riparian buffers all the way to reevaluating the definition of the waters of the United States to clarify the regulatory authority under the Clean Water Act. A major challenge for scientists is linking the small-scale physical drivers with their larger-scale fluvial and geomorphic context and ecological consequences. Although the fine scales of field and laboratory studies are best suited to identifying the fundamental physical and biological processes, that understanding must be successfully linked to cumulative effects at watershed to regional and continental scales.

Ecohydrologic role of solar radiation on landscape evolution

NASA Astrophysics Data System (ADS)

Yetemen, Omer; Istanbulluoglu, Erkan; Flores-Cervantes, J. Homero; Vivoni, Enrique R.; Bras, Rafael L.

2015-02-01

Solar radiation has a clear signature on the spatial organization of ecohydrologic fluxes, vegetation patterns and dynamics, and landscape morphology in semiarid ecosystems. Existing landscape evolution models (LEMs) do not explicitly consider spatially explicit solar radiation as model forcing. Here, we improve an existing LEM to represent coupled processes of energy, water, and sediment balance for semiarid fluvial catchments. To ground model predictions, a study site is selected in central New Mexico where hillslope aspect has a marked influence on vegetation patterns and landscape morphology. Model predictions are corroborated using limited field observations in central NM and other locations with similar conditions. We design a set of comparative LEM simulations to investigate the role of spatially explicit solar radiation on landscape ecohydro-geomorphic development under different uplift scenarios. Aspect-control and network-control are identified as the two main drivers of soil moisture and vegetation organization on the landscape. Landscape-scale and long-term implications of these short-term ecohdrologic patterns emerged in modeled landscapes. As north facing slopes (NFS) get steeper by continuing uplift they support erosion-resistant denser vegetation cover which leads to further slope steepening until erosion and uplift attains a dynamic equilibrium. Conversely, on south facing slopes (SFS), as slopes grow with uplift, increased solar radiation exposure with slope supports sparser biomass and shallower slopes. At the landscape scale, these differential erosion processes lead to asymmetric development of catchment forms, consistent with regional observations. Understanding of ecohydrogeomorphic evolution will improve to assess the impacts of past and future climates on landscape response and morphology.

Coastal knickpoints and the competition between fluvial and wave-driven erosion on rocky coastlines

NASA Astrophysics Data System (ADS)

Limber, Patrick W.; Barnard, Patrick L.

2018-04-01

Active margin coastlines are distinguished by rock erosion that acts in two different directions: waves erode the coast horizontally or landwards, a process that creates sea cliffs; and rivers and streams erode the landscape vertically via channel incision. The relative rates of each process exert a dominant control on coastline morphology. Using a model of river channel incision and sea-cliff retreat, we explore how terrestrial and marine erosion compete to shape coastal topography, and specifically what conditions encourage the development of coastal knickpoints (i.e., a river or stream channels that end at a raised sea-cliff edge). We then compare results to actual landscapes. Model results and observations show that coastal knickpoint development is strongly dependent on drainage basin area, where knickpoints typically occur in drainage basins smaller than 5 × 105-6 × 106 m2, as well as channel geometry and sea-cliff retreat rate. In our study area, coastal knickpoints with persistent flow (waterfalls) are uncommon and form only within a small morphological window when 1) drainage basin area is large enough to sustain steady stream discharge, but not large enough to out-compete sea-cliff formation, 2) sea-cliff retreat is rapid, and 3) channel concavity is low so that channel slopes at the coast are high. This particular geomorphic combination can sustain sea-cliff formation even when streams tap into larger drainage basins with greater discharge and more stream power, and provides an initial explanation of why persistent coastal waterfalls are, along many coastlines, relatively rare features.

Coastal knickpoints and the competition between fluvial and wave-driven erosion on rocky coastlines

USGS Publications Warehouse

Limber, Patrick; Barnard, Patrick

2018-01-01

Active margin coastlines are distinguished by rock erosion that acts in two different directions: waves erode the coast horizontally or landwards, a process that creates sea cliffs; and rivers and streams erode the landscape vertically via channel incision. The relative rates of each process exert a dominant control on coastline morphology. Using a model of river channel incision and sea-cliff retreat, we explore how terrestrial and marine erosion compete to shape coastal topography, and specifically what conditions encourage the development of coastal knickpoints (i.e., a river or stream channels that end at a raised sea-cliff edge). We then compare results to actual landscapes. Model results and observations show that coastal knickpoint development is strongly dependent on drainage basin area, where knickpoints typically occur in drainage basins smaller than 5 × 105–6 × 106 m2, as well as channel geometry and sea-cliff retreat rate. In our study area, coastal knickpoints with persistent flow (waterfalls) are uncommon and form only within a small morphological window when 1) drainage basin area is large enough to sustain steady stream discharge, but not large enough to out-compete sea-cliff formation, 2) sea-cliff retreat is rapid, and 3) channel concavity is low so that channel slopes at the coast are high. This particular geomorphic combination can sustain sea-cliff formation even when streams tap into larger drainage basins with greater discharge and more stream power, and provides an initial explanation of why persistent coastal waterfalls are, along many coastlines, relatively rare features.

Linking high-resolution geomorphic mapping, sediment sources, and channel types in a formerly glaciated basin of northeastern Alto-Adige/Sudtirol, Italy

NASA Astrophysics Data System (ADS)

Brardinoni, F.; Perina, E.; Bonfanti, G.; Falsitta, G.; Agliardi, F.

2012-04-01

To characterize channel-network morphodynamics and response potential in the Gadria-Strimm basin (14.8 km^2) we conduct a concerted effort entailing: (i) high-resolution mapping of landforms, channel reaches, and sediment sources; and (ii) historical evolution of colluvial channel disturbance through sequential aerial photosets (1945-59-69-82-90-00-06-11). The mapping was carried out via stereographic inspection of aerial photographs, examination of 2.5-m gridded DTM and DSM, and extensive field work. The study area is a formerly glaciated basin characterized by peculiar landform assemblages imposed by a combination of tectonic and glacial first-order structures. The most striking feature in Strimm Creek is a structurally-controlled valley step separating an upper hanging valley, dominated by periglacial and fluvial processes, and a V-notched lower part in which lateral colluvial channels are directly connected to Strimm's main stem. In Gadria Creek, massive kame terraces located in proximity of the headwaters provide virtually unlimited sediment supply to frequent debris-flow activity, making this sub-catchment an ideal site for monitoring, hence studying the mechanics of these processes. Preliminary results point to a high spatial variability of the colluvial channel network, in which sub-sectors have remained consistently active during the study period while others have become progressively dormant with notable forest re-growth. In an attempt to link sediment flux to topography and substrate type, future work will involve photogrammetric analysis across the sequential aerial photosets as well as a morphometric/geomechanical characterization of the surficial materials.

High-resolution urban flood modelling - a joint probability approach

NASA Astrophysics Data System (ADS)

Hartnett, Michael; Olbert, Agnieszka; Nash, Stephen

2017-04-01

The hydrodynamic modelling of rapid flood events due to extreme climatic events in urban environment is both a complex and challenging task. The horizontal resolution necessary to resolve complexity of urban flood dynamics is a critical issue; the presence of obstacles of varying shapes and length scales, gaps between buildings and the complex geometry of the city such as slopes affect flow paths and flood levels magnitudes. These small scale processes require a high resolution grid to be modelled accurately (2m or less, Olbert et al., 2015; Hunter et al., 2008; Brown et al., 2007) and, therefore, altimetry data of at least the same resolution. Along with availability of high-resolution LiDAR data and computational capabilities, as well as state of the art nested modelling approaches, these problems can now be overcome. Flooding and drying, domain definition, frictional resistance and boundary descriptions are all important issues to be addressed when modelling urban flooding. In recent years, the number of urban flood models dramatically increased giving a good insight into various modelling problems and solutions (Mark et al., 2004; Mason et al., 2007; Fewtrell et al., 2008; Shubert et al., 2008). Despite extensive modelling work conducted for fluvial (e.g. Mignot et al., 2006; Hunter et al., 2008; Yu and Lane, 2006) and coastal mechanisms of flooding (e.g. Gallien et al., 2011; Yang et al., 2012), the amount of investigations into combined coastal-fluvial flooding is still very limited (e.g. Orton et al., 2012; Lian et al., 2013). This is surprising giving the extent of flood consequences when both mechanisms occur simultaneously, which usually happens when they are driven by one process such as a storm. The reason for that could be the fact that the likelihood of joint event is much smaller than those of any of the two contributors occurring individually, because for fast moving storms the rainfall-driven fluvial flood arrives usually later than the storm surge (Divoky et al., 2005). Nevertheless, such events occur and in Ireland alone there are several cases of serious damage due to flooding resulting from a combination of high sea water levels and river flows driven by the same meteorological conditions (e.g. Olbert et al. 2015). A November 2009 fluvial-coastal flooding of Cork City bringing €100m loss was one such incident. This event was used by Olbert et al. (2015) to determine processes controlling urban flooding and is further explored in this study to elaborate on coastal and fluvial flood mechanisms and their roles in controlling water levels. The objective of this research is to develop a methodology to assess combined effect of multiple source flooding on flood probability and severity in urban areas and to establish a set of conditions that dictate urban flooding due to extreme climatic events. These conditions broadly combine physical flood drivers (such as coastal and fluvial processes), their mechanisms and thresholds defining flood severity. The two main physical processes controlling urban flooding: high sea water levels (coastal flooding) and high river flows (fluvial flooding), and their threshold values for which flood is likely to occur, are considered in this study. Contribution of coastal and fluvial drivers to flooding and their impacts are assessed in a two-step process. The first step involves frequency analysis and extreme value statistical modelling of storm surges, tides and river flows and ultimately the application of joint probability method to estimate joint exceedence return periods for combination of surges, tide and river flows. In the second step, a numerical model of Cork Harbour MSN_Flood comprising a cascade of four nested high-resolution models is used to perform simulation of flood inundation under numerous hypothetical coastal and fluvial flood scenarios. The risk of flooding is quantified based on a range of physical aspects such as the extent and depth of inundation (Apel et al., 2008) The methodology includes estimates of flood probabilities due to coastal- and fluvial-driven processes occurring individually or jointly, mechanisms of flooding and their impacts on urban environment. Various flood scenarios are examined in order to demonstrate that this methodology is necessary to quantify the important physical processes in coastal flood predictions. Cork City, located on the south of Ireland subject to frequent coastal-fluvial flooding, is used as a study case.

The Geomorphic Road Analysis and Inventory Package (GRAIP) Volume 1: Data Collection Method

Treesearch

Thomas A. Black; Richard M. Cissel; Charles H. Luce

2012-01-01

An important first step in managing forest roads for improved water quality and aquatic habitat is the performance of an inventory. The Geomorphic Roads Analysis and Inventory Package (GRAIP) was developed as a tool for making a comprehensive inventory and analysis of the effects of forest roads on watersheds. This manual describes the data collection and process of a...

Geomorphic characteristics and classification of Duluth-area streams, Minnesota

USGS Publications Warehouse

Fitzpatrick, Faith A.; Peppler, Marie C.; DePhilip, Michele M.; Lee, Kathy E.

2006-01-01

In 2003 and 2004, a geomorphic assessment of streams in 20 watersheds in the Duluth, Minn., area was conducted to identify and summarize geomorphic characteristics, processes, disturbance mechanisms, and potential responses to disturbance. Methods used to assess the streams included watershed characterization, descriptions of segment slopes and valley types, historical aerial photograph interpretation, and rapid field assessments and intensive field surveys of stream reaches. Geomorphic conditions were summarized into a segment-scale classification with 15 categories mainly based on drainage-network position and slope, and, secondarily, based on geologic setting, valley type, and dominant geomorphic processes. Main causes of geomorphic disturbance included historical logging and agriculture, and ongoing urban development, human-caused channel alterations, road and storm sewer drainage, ditching, hiking trails, and gravel pits or quarries. Geomorphic responses to these disturbances are dependent on a combination of drainage-network position, slope, and geologic setting. Geologic setting is related to drainage-network position because the geologic deposits parallel the Lake Superior shoreline. Headwater streams in large watersheds flow over glacial deposits above altitudes of about 1,200 feet (ft). Headwater tributaries and upper main stems have ditch-like channels with gentle slopes and no valleys. Urban development and road drainage cause increased runoff and flood peaks in these segments resulting in channel widening. Below about 1,200 ft, main-stem segments generally are affected by bedrock type and structure and have steep slopes and confined or entrenched valleys. Increases in flood peaks do not cause incision or widening in the bedrock-controlled valleys; instead, the flow and scour areas are expanded. Feeder tributaries to these main stems have steep, confined valleys and may be sources for sediment from urban areas, road runoff, or storm sewer outfalls. Main-stem segments near the glacial deposits/surficial bedrock contact (1,000–1,200 ft) have the most potential for response to disturbance because they tend to have narrow valleys with sandy glacial lakeshore deposits and moderate slopes. Increases in flood peaks (from upstream increases in runoff) increase the potential for landslides and mass wasting from valley sides as well as channel widening.

Using a conceptual model to assess the role of flow regulation in the hydromorphological evolution of riparian corridors

NASA Astrophysics Data System (ADS)

Martínez-Fernández, Vanesa; Gonzalez del Tánago, Marta; García de Jalón, diego

2017-04-01

Riparian corridors result from active vegetation-fluvial interactions, which are highly dependent on flow regime conditions and sediment dynamics. Colonization, establishment and survival of species are constrained by fluvial processes which vary according to topographic and sedimentological complexity of the corridor. In order to manage these dynamic and complex riparian systems there is a need for practical tools based on conceptual models. The objective of this study was to apply the conceptual model of riparian corridors lateral zonation in response to the dominant fluvial processes established by Gurnell et al. (2015) and verify its usefulness as a tool for assessing the effect of flow regulation. Two gravel rivers have been selected for this purpose from the north of Spain, the Porma River regulated by Boñar large dam and the unregulated Curueño River. The historical series of flows and the aerial photographs of 1956 and 2011 on which the river corridor has been delimited have been analyzed and identified the permanent inundated zone (1) and four areas of riparian vegetation dominated respectively by fluvial disturbance with coarse sediment erosion and deposition (zone 2), fluvial disturbance with finer sediment deposition (zone 3), inundation (zone 4) and soil moisture regime (zone 5). Likewise, a two-dimensional hydraulic simulation was performed with avenues of different return periods and calculated the prevailing hydraulic conditions (depths, velocities and drag forces) to characterize each of the vegetation zones mentioned in both rivers. The results show that the most active zone 2 (fluvial disturbance dominated showing coarse sediment erosion and deposition) disappears due to the regulation of flows and vegetation encroachment, while the riparian corridor is dominated by the less active zone where the vegetation is maintained by the humidity of sporadic floods and underground runoff. Moreover, by means of the hydraulic simulation we have found a close relationship between the different areas of fluvial processes recognized through its vegetation and hydraulic conditions, which predicts the expected evolution of vegetation at different scenarios of regulation.

Effects of Land-Cover Change, Floods, and Stream Position on Geomorphic Processes - Implications for Restoration Activities

USGS Publications Warehouse

Fitzpatrick, F.A.; ,

2001-01-01

A geomorphic study for North Fish Creek, a northern Wisconsin tributary to Lake Superior was analyzed to determine the hydrologic and geomorphic changes caused by clear-cut logging and agricultural activity. Discharge magnitude estimated with HEC-2 for full-channel capacities indicate that modern full-channel discharges are about twice as large as pre-1946 full-channel discharges. Flood-plain deposition rates were high along the transitional main stem after European settlement. Restoration and protection activities would be most effective if focused on watershed practices to reduce runoff and on channel restoration that reduce buff and bank erosion in the upper and transitional main stems.

Geomorphic control of radionuclide diffusion in desert soils

USGS Publications Warehouse

Pelletier, J.D.; Harrington, C.D.; Whitney, J.W.; Cline, M.; DeLong, S.B.; Keating, G.; Ebert, T.K.

2005-01-01

Diffusion is a standard model for the vertical migration of radionuclides in soil profiles. Here we show that diffusivity values inferred from fallout 137CS profiles in soils on the Fortymile Wash alluvial fan, Nye County, Nevada, have a strong inverse correlation with the age of the geomorphic surface. This result suggests that radionuclide-bound particles are predominantly transported by infiltration rather than by bulk-mixing processes such as wetting/ drying, freeze/thaw, and bioturbation. Our results provide a preliminary basis for using soil-geomorphic mapping, point-based calibration data, and the diffusion model to predict radionuclide trans desert soils within a pedotransfer-function approach. Copyright 2005 by the American Geophysical Union.

Heavy mineral analyses as a powerful tool in fluvial geomorphology

NASA Astrophysics Data System (ADS)

von Suchodoletz, Hans; Gärtner, Andreas; Faust, Dominik

2014-05-01

The Marneuli depression is a tectonic sub-basin of the Transcaucasian depression in eastern Georgia, filled with several decametres of fluvial, lacustrine and aeolian Quaternary sediments. In order to reconstruct past landscape evolution of the region we studied Late Quaternary fluvial sediments found along several rivers that flow through that depression. Whereas Holocene river sediments could generally easily be assigned to corresponding rivers, this was not always the case for older fluvial sediments. For this reason, we studied the heavy mineral contents of five recent rivers and of four sedimentary deposits of potential precursors. A total of 4088 analysed heavy mineral grains enabled us to set up the characteristic heavy mineral distribution pattern for each sample. Using these data, we were able to reconstruct the most likely source areas of the Late Pleistocene fluvial sediments and to link them with the catchment areas of recent rivers. This allowed us to identify and to substantiate significant Late Quaternary river diversions that could at least partly be assigned to ongoing tectonic processes.

Field migration rates of tidal meanders recapitulate fluvial morphodynamics

NASA Astrophysics Data System (ADS)

Finotello, Alvise; Lanzoni, Stefano; Ghinassi, Massimiliano; Marani, Marco; Rinaldo, Andrea; D'Alpaos, Andrea

2018-02-01

The majority of tidal channels display marked meandering features. Despite their importance in oil-reservoir formation and tidal landscape morphology, questions remain on whether tidal-meander dynamics could be understood in terms of fluvial processes and theory. Key differences suggest otherwise, like the periodic reversal of landscape-forming tidal flows and the widely accepted empirical notion that tidal meanders are stable landscape features, in stark contrast with their migrating fluvial counterparts. On the contrary, here we show that, once properly normalized, observed migration rates of tidal and fluvial meanders are remarkably similar. Key to normalization is the role of tidal channel width that responds to the strong spatial gradients of landscape-forming flow rates and tidal prisms. We find that migration dynamics of tidal meanders agree with nonlinear theories for river meander evolution. Our results challenge the conventional view of tidal channels as stable landscape features and suggest that meandering tidal channels recapitulate many fluvial counterparts owing to large gradients of tidal prisms across meander wavelengths.

Human geomorphic footprint and global geomorphic change: implications for hydrogeomorphic hazards

NASA Astrophysics Data System (ADS)

Remondo, Juan

2010-05-01

The human geomorphic footprint (HGF), expressed as the area affected by the construction of new 'anthropogeoforms' or the volume of geologic materials directly or indirectly displaced by human action has grown considerably in the last decades. Available data suggest that the present HGF is roughly 50,000 km2 a-1 of new anthropogeoforms and 300 x109 t a-1 of solid materials transferred from one part of the earth's surface to another. The latter represents a 'technological denudation' that could be 1-2 orders of magnitude greater than denudation by natural agents or sediment transport by the world's rivers. This implies a profound modification of geomorphic processes that produces a series of often disregarded environmental consequences. Some of those can by directly linked to excavation/accumulation activities and are essentially local, but in other cases the possible relationship appears to be more indirect and could have a widespread character. The transformation of land surface by human action is shown not only by landform construction and transfer of geologic materials, but also by land-use change in general and modification of the characteristics of the surface layer. This seems to affect both the hydrologic response and the sensitivity of that surface layer to different geomorphic agents. The magnitude of the above mentioned modification is logically related to the intensity of human activities, themselves related to the number of people on the planet and their economic and technological capabilities, which grow practically in all regions of the planet. It is thus reasonable to expect that the HGF and its effects should grow with time. If this were so, we should expect to find evidences of a general acceleration of geomorphic processes in the world that could represent a 'global geomorphic change'. The final expression of geomorphic processes, which could be used to test that hypothesis, is sediment generation and deposition. Data are presented on sedimentation rates in different areas showing that in most of them sedimentation has increased significantly during the last century (by about one order of magnitude in most cases) and that such increase does not seem to be related to climate but rather to human activity. If a global geomorphic change is indeed taking place, an increase in the frequency/intensity of related hazards, such as landslides or floods, should be expected. Data are presented indicating that it could be so. If what the data presented suggest is confirmed by further and deeper analyses, existing hazard and risk assessments for those processes should be reconsidered, because they would likely represent underestimates. The CAMGEO Team is formed by the following persons: Antonio Cendrero1, Gonzalo Méndez2, Jaime Bonachea1, José Gómez-Arozamena1, José Luis Cavallotto5, José Manuel Naredo3, Juan Remondo1, Lazaro V. Zuquette6, Luis Salas1, Luis M. Forte4, Marcilene Dantas-Ferreira6, Maria Angélica de O. Bezerra7, Mario da Silva, Martín A. Hurtado4, Osni J. Pejon6, Victoria Rivas1, Viola M. Bruschi1. 1) Universidad de Cantabria, Spain; 2) Universidad de Vigo, Spain; 3) Universidad Politécnica de Madrid, Spain; 4) Universidad Nacional de La Plata, Argentina; 5) Servicio de Hidrografía Naval, Argentina; 6) Universidade de Sao Paulo, Sao Carlos, Brazil; 7) Universidade Federal de Mato Grosso do Sul, Brazil.

Mars: Noachian hydrology by its statistics and topology

NASA Technical Reports Server (NTRS)

Cabrol, N. A.; Grin, E. A.

1993-01-01

Discrimination between fluvial features generated by surface drainage and subsurface aquifer discharges will provide clues to the understanding of early Mars' climatic history. Our approach is to define the process of formation of the oldest fluvial valleys by statistical and topological analyses. Formation of fluvial valley systems reached its highest statistical concentration during the Noachian Period. Nevertheless, they are a scarce phenomenom in Martian history, localized on the craterized upland, and subject to latitudinal distribution. They occur sparsely on Noachian geological units with a weak distribution density, and appear in reduced isolated surface (around 5 x 10(exp 3)(sq km)), filled by short streams (100-300 km length). Topological analysis of the internal organization of 71 surveyed Noachian fluvial valley networks also provides information on the mechanisms of formation.

Geologic Map of MTM 35337, 40337, and 45337 Quadrangles, Deuteronilus Mensae Region of Mars

USGS Publications Warehouse

Chuang, Frank C.; Crown, David A.

2009-01-01

Deuteronilus Mensae, first defined as an albedo feature at lat 35.0 deg N., long 5.0 deg E., by U.S. Geological Survey (USGS) and International Astronomical Union (IAU) nomenclature, is a gradational zone along the dichotomy boundary in the northern mid-latitudes of Mars. The boundary in this location includes the transition from the rugged cratered highlands of Arabia Terra to the northern lowland plains of Acidalia Planitia. Within Deuteronilus Mensae, polygonal mesas are prominent along with features diagnostic of Martian fretted terrain, including lobate debris aprons, lineated valley fill, and concentric crater fill. Lobate debris aprons, as well as the valley and crater fill deposits, are geomorphic indicators of ground ice, and their concentration in Deuteronilus Mensae is of great interest because of their potential association with Martian climate change. The paucity of impact craters on the surfaces of debris aprons and the presence of ice-cemented mantle material imply young (for example, Amazonian) surface ages that are consistent with recent climate change in this region of Mars. North of Deuteronilus Mensae are the northern lowlands, a potential depositional sink that may have had large standing bodies of water or an ocean in the past. The northern lowlands have elevations that are several kilometers below the ancient cratered highlands with significantly younger surface ages. The morphologic and topographic characteristics of the Deuteronilus Mensae region record a diverse geologic history, including significant modification of the ancient highland plateau and resurfacing of low-lying regions. Previous studies of this region have interpreted a complex array of geologic processes, including eolian, fluvial and glacial activity, coastal erosion, marine deposition, mass wasting, tectonic faulting, effusive volcanism, and hydrovolcanism. The origin and age of the Martian crustal dichotomy boundary are fundamental questions that remain unresolved at the present time. Several scenarios for its formation, including single and multiple large impact events, have been proposed and debated in the literature. Endogenic processes whereby crust is thinned by internal mantle convection and tectonic processes have also been proposed. Planetary accretion models and isotopic data from Martian meteorites suggest that the crust formed very early in Martian history. Using populations of quasi-circular depressions extracted from the topography of Mars, other studies suggest that the age difference between the highlands and lowlands could be ~100 m.y.. Furthermore, understanding the origin and age of the dichotomy boundary has been made more complicated due to significant erosion and deposition that have modified the boundary and its adjacent regions. The resulting diversity of terrains and features is likely a combined result of ancient and recent events. Detailed geologic analyses of dichotomy boundary zones are important for understanding the spatial and temporal variations in highland evolution. This information, and comparisons to other highland regions, can help elucidate the scale of potential environmental changes. Previous geomorphic and geologic mapping investigations of the Deuteronilus Mensae region have been completed at local to global scales. The regional geology was first mapped by Lucchitta (1978) at 1:5,000,000 scale using Mariner 9 data. This study concluded that high crater flux early in Martian history formed overlapping craters and basins that were later filled by voluminous lava flows that buried the impacted surface, creating the highlands. After this period of heavy bombardment, fluvial erosion of the highlands formed the canyons and valleys, followed by dissection that created the small mesas and buttes, and later, formation of the steep escarpment marking the present-day northern highland margin. After valley dissection, mass wasting and eolian processes caused lateral retreat of mesas and buttes

Combined fluvial and pluvial urban flood hazard analysis: concept development and application to Can Tho city, Mekong Delta, Vietnam

NASA Astrophysics Data System (ADS)

Apel, Heiko; Martínez Trepat, Oriol; Nghia Hung, Nguyen; Thi Chinh, Do; Merz, Bruno; Viet Dung, Nguyen

2016-04-01

Many urban areas experience both fluvial and pluvial floods, because locations next to rivers are preferred settlement areas and the predominantly sealed urban surface prevents infiltration and facilitates surface inundation. The latter problem is enhanced in cities with insufficient or non-existent sewer systems. While there are a number of approaches to analyse either a fluvial or pluvial flood hazard, studies of a combined fluvial and pluvial flood hazard are hardly available. Thus this study aims to analyse a fluvial and a pluvial flood hazard individually, but also to develop a method for the analysis of a combined pluvial and fluvial flood hazard. This combined fluvial-pluvial flood hazard analysis is performed taking Can Tho city, the largest city in the Vietnamese part of the Mekong Delta, as an example. In this tropical environment the annual monsoon triggered floods of the Mekong River, which can coincide with heavy local convective precipitation events, causing both fluvial and pluvial flooding at the same time. The fluvial flood hazard was estimated with a copula-based bivariate extreme value statistic for the gauge Kratie at the upper boundary of the Mekong Delta and a large-scale hydrodynamic model of the Mekong Delta. This provided the boundaries for 2-dimensional hydrodynamic inundation simulation for Can Tho city. The pluvial hazard was estimated by a peak-over-threshold frequency estimation based on local rain gauge data and a stochastic rainstorm generator. Inundation for all flood scenarios was simulated by a 2-dimensional hydrodynamic model implemented on a Graphics Processing Unit (GPU) for time-efficient flood propagation modelling. The combined fluvial-pluvial flood scenarios were derived by adding rainstorms to the fluvial flood events during the highest fluvial water levels. The probabilities of occurrence of the combined events were determined assuming independence of the two flood types and taking the seasonality and probability of coincidence into account. All hazards - fluvial, pluvial and combined - were accompanied by an uncertainty estimation taking into account the natural variability of the flood events. This resulted in probabilistic flood hazard maps showing the maximum inundation depths for a selected set of probabilities of occurrence, with maps showing the expectation (median) and the uncertainty by percentile maps. The results are critically discussed and their usage in flood risk management are outlined.

Scaling considerations related to interactions of hydrologic, pedologic and geomorphic processes (Invited)

NASA Astrophysics Data System (ADS)

Sidle, R. C.

2013-12-01

Hydrologic, pedologic, and geomorphic processes are strongly interrelated and affected by scale. These interactions exert important controls on runoff generation, preferential flow, contaminant transport, surface erosion, and mass wasting. Measurement of hydraulic conductivity (K) and infiltration capacity at small scales generally underestimates these values for application at larger field, hillslope, or catchment scales. Both vertical and slope-parallel saturated flow and related contaminant transport are often influenced by interconnected networks of preferential flow paths, which are not captured in K measurements derived from soil cores. Using such K values in models may underestimate water and contaminant fluxes and runoff peaks. As shown in small-scale runoff plot studies, infiltration rates are typically lower than integrated infiltration across a hillslope or in headwater catchments. The resultant greater infiltration-excess overland flow in small plots compared to larger landscapes is attributed to the lack of preferential flow continuity; plot border effects; greater homogeneity of rainfall inputs, topography and soil physical properties; and magnified effects of hydrophobicity in small plots. At the hillslope scale, isolated areas with high infiltration capacity can greatly reduce surface runoff and surface erosion at the hillslope scale. These hydropedologic and hydrogeomorphic processes are also relevant to both occurrence and timing of landslides. The focus of many landslide studies has typically been either on small-scale vadose zone process and how these affect soil mechanical properties or on larger scale, more descriptive geomorphic studies. One of the issues in translating laboratory-based investigations on geotechnical behavior of soils to field scales where landslides occur is the characterization of large-scale hydrological processes and flow paths that occur in heterogeneous and anisotropic porous media. These processes are not only affected by the spatial distribution of soil physical properties and bioturbations, but also by geomorphic attributes. Interactions among preferential flow paths can induce rapid pore water pressure response within soil mantles and trigger landslides during storm peaks. Alternatively, in poorly developed and unstructured soils, infiltration occurs mainly through the soil matrix and a lag time exists between the rainfall peak and development of pore water pressures at depth. Deep, slow-moving mass failures are also strongly controlled by secondary porosity within the regolith with the timing of activation linked to recharge dynamics. As such, understanding both small and larger scale processes is needed to estimate geomorphic impacts, as well as streamflow generation and contaminant migration.

Catastrophic valley fills record large Himalayan earthquakes, Pokhara, Nepal

NASA Astrophysics Data System (ADS)

Stolle, Amelie; Bernhardt, Anne; Schwanghart, Wolfgang; Hoelzmann, Philipp; Adhikari, Basanta R.; Fort, Monique; Korup, Oliver

2017-12-01

Uncertain timing and magnitudes of past mega-earthquakes continue to confound seismic risk appraisals in the Himalayas. Telltale traces of surface ruptures are rare, while fault trenches document several events at best, so that additional proxies of strong ground motion are needed to complement the paleoseismological record. We study Nepal's Pokhara basin, which has the largest and most extensively dated archive of earthquake-triggered valley fills in the Himalayas. These sediments form a 148-km2 fan that issues from the steep Seti Khola gorge in the Annapurna Massif, invading and plugging 15 tributary valleys with tens of meters of debris, and impounding several lakes. Nearly a dozen new radiocarbon ages corroborate at least three episodes of catastrophic sedimentation on the fan between ∼700 and ∼1700 AD, coinciding with great earthquakes in ∼1100, 1255, and 1344 AD, and emplacing roughly >5 km3 of debris that forms the Pokhara Formation. We offer a first systematic sedimentological study of this formation, revealing four lithofacies characterized by thick sequences of mid-fan fluvial conglomerates, debris-flow beds, and fan-marginal slackwater deposits. New geochemical provenance analyses reveal that these upstream dipping deposits of Higher Himalayan origin contain lenses of locally derived river clasts that mark time gaps between at least three major sediment pulses that buried different parts of the fan. The spatial pattern of 14C dates across the fan and the provenance data are key to distinguishing these individual sediment pulses, as these are not evident from their sedimentology alone. Our study demonstrates how geomorphic and sedimentary evidence of catastrophic valley infill can help to independently verify and augment paleoseismological fault-trench records of great Himalayan earthquakes, while offering unparalleled insights into their long-term geomorphic impacts on major drainage basins.

Balanced sediment fluxes in southern California’s Mediterranean-climate zone salt marshes

USGS Publications Warehouse

Rosencranz, Jordan A.; Ganju, Neil K.; Ambrose, Richard F.; Brosnahan, Sandra M.; Dickhudt, Patrick J.; Guntenspergen, Glenn R.; MacDonald, Glen M.; Takekawa, John Y.; Thorne, Karen M.

2016-01-01

Salt marsh elevation and geomorphic stability depends on mineral sedimentation. Many Mediterranean-climate salt marshes along southern California, USA coast import sediment during El Niño storm events, but sediment fluxes and mechanisms during dry weather are potentially important for marsh stability. We calculated tidal creek sediment fluxes within a highly modified, sediment-starved, 1.5-km2 salt marsh (Seal Beach) and a less modified 1-km2marsh (Mugu) with fluvial sediment supply. We measured salt marsh plain suspended sediment concentration and vertical accretion using single stage samplers and marker horizons. At Seal Beach, a 2014 storm yielded 39 and 28 g/s mean sediment fluxes and imported 12,000 and 8800 kg in a western and eastern channel. Western channel storm imports offset 8700 kg exported during 2 months of dry weather, while eastern channel storm imports augmented 9200 kg imported during dry weather. During the storm at Mugu, suspended sediment concentrations on the marsh plain increased by a factor of four; accretion was 1–2 mm near creek levees. An exceptionally high tide sequence yielded 4.4 g/s mean sediment flux, importing 1700 kg: 20 % of Mugu’s dry weather fluxes. Overall, low sediment fluxes were observed, suggesting that these salt marshes are geomorphically stable during dry weather conditions. Results suggest storms and high lunar tides may play large roles, importing sediment and maintaining dry weather sediment flux balances for southern California salt marshes. However, under future climate change and sea level rise scenarios, results suggest that balanced sediment fluxes lead to marsh elevational instability based on estimated mineral sediment deficits.

Geomorphic response of rivers to glacial retreat and increasing peak flows downstream from Mount Rainier, Washington

NASA Astrophysics Data System (ADS)

Czuba, J. A.; Barnas, C. R.; Magirl, C. S.; Voss, F. D.

2010-12-01

On Mount Rainier, Washington, the National Park Service has documented widespread aggradation of as much as 10 m since the early 20th century, of rivers draining the glaciated stratovolcano. This rapid sedimentation appears to be related to glacial retreat and also may be a function of the increased magnitude and timing of peak flows that mobilize and transport sediment. We are conducting an assessment of the Puget Lowland rivers that drain Mount Rainier, 25-100 km downstream from the park boundary, to document the geomorphic response of the downstream reaches given the widespread aggradation upstream. These downstream reaches provide critical aquatic habitat for spawning and rearing of several species of salmonids, including endangered Chinook salmon and steelhead. Fluvial sedimentation can have both deleterious and beneficial effects on aquatic habitat depending on sediment particle size, river slope and width, and river management. To date, our work shows sedimentation of as much as 2 m between 1984 and 2009 in these lowland rivers. Aggradation rates that were calculated by comparing channel change at 156 cross sections, ranged between 4.8 and 9.1 cm/yr in reaches where rivers exit the mountain front and enter the lowland. Analysis of streamflow-gaging station data from throughout the watersheds draining Mount Rainier show rapid incision and aggradation, suggesting pulses of coarse-grained bedload may be moving down the mountainous rivers as kinetic waves. Preliminary results, however, seem to indicate that the rivers in the Puget Lowland have not yet experienced significant widespread sedimentation directly related to glacial retreat. Estimating the time of arrival of mobilized alluvium is a critical need for resource managers given the potential effects of sedimentation on river flood-conveyance capacity, fish habitat, and estuarine wetlands.

Channel dynamics and geomorphic resilience in an ephemeral Mediterranean river affected by gravel mining

NASA Astrophysics Data System (ADS)

Calle, Mikel; Alho, Petteri; Benito, Gerardo

2017-05-01

Gravel mining has been a widespread activity in ephemeral rivers worldwide whose long-lasting hydrogeomorphological impacts preclude effective implementation of water and environmental policies. This paper presents a GIS-based method for temporal assessment of morphosedimentary changes in relation to in-channel gravel mining in a typical ephemeral Mediterranean stream, namely the Rambla de la Viuda (eastern Spain). The aims of this work were to identify morphosedimentary changes and responses to human activities and floods, quantify river degradations and analyze factors favoring fluvial recovery for further applications in other rivers. Aerial photographs and LiDAR topography data were studied to analyze geomorphic evolution over the past 70 years along a 7.5-km reach of an ephemeral gravel stream that has been mined intensively since the 1970s. To evaluate changes in the riverbed, we mapped comparable units applying morphological, hydraulic, and stability (based on vegetation density and elevation) criteria to 13 sets of aerial photographs taken from 1946 to 2012. A detailed spatiotemporal analysis of comparable units revealed a 50% reduction in the active section and a 20% increase in stable areas, compared to the conditions observed prior to gravel mining. Instream mining was first observed in 1976 aerial photograph covering already up to 50% of the 1956 riverbed area. River degradation since then was quantified by means of a LiDAR DTM and RTK-GPS measurements, which revealed a 3.5-m incision that had started simultaneously with gravel mining. Climate and land use changes were present but the effects were completely masked by changes produced by instream gravel mining. Therefore, river incision/degradation was triggered by scarcity of sediment and lack of longitudinal sedimentary connection, creating an unbalanced river system that is still adjusting to the present hydrosedimentary conditions.

Ten years after the flood: a case of extended geomorphic convalescence in an upland stream

NASA Astrophysics Data System (ADS)

Milan, D. J.; Schwendel, A.; Heritage, G. L.; Entwistle, N. S.; Skinner, C. J.

2017-12-01

Long-term data monitoring the response of fluvial systems to geomorphically effective events is often lacking. In July 2007 a severe event affected the Thinhope Burn, a small (12 km2) tributary to the South Tyne, in Cumbria, UK. The 24-hr rainfall for a 5-km2 radar grid cell located in the headwaters of Thinhope Burn was 236 mm, with maximum hourly rainfall of 30 mm h-1. The event generated peak discharges in the order of 60 m3s-1 and shear stresses of 533 Nm-2, capable of mobilsing metre-size boulders. The Thinhope Burn catchment showed `responsive' behaviour to the event resulting in a substantial net delivery of 3077 m3 of gravel to a 500 m reach, and fully activated the valley floor and slopes, including evidence of peat slides in the headwaters. Since 2007 we have monitored the reach using a combination of dGPS and terrestrial LiDAR data to derive DEMs, and difference these to estimate spatial volumetric patterns of erosion and deposition. Ten years on, there appears to be limited evidence of recovery of the valley floor system, possibly due to the effects of several wet winters (e.g. 2013 and 2015). Sediments remain unconsolidated and free of vegetation, and are easily mobilised during floods. Climate change scenarios for the UK suggest wetter winters, that could prevent recovery of upland rivers where the sediment system has already been fully activated by a large flood, resulting in increased sediment supply to areas downstream and a commensurate increase in flood risk.

Implications of sedimentological studies for environmental pollution assessment and management: Examples from fluvial systems in North Queensland and Western Australia

NASA Astrophysics Data System (ADS)

Eyre, Bradley; McConchie, David

1993-05-01

Sedimentology is of increasing importance in environmental research, particularly environmental pollution studies, where past trends in environmental processes need to be combined with data on present conditions to predict likely future changes—the past and present as a key to the future. Two examples are used to illustrate the role of sedimentology in assessing the influence of major processes on the transport, accumulation, deposition and modification of contaminants in fluvial/estuarine systems and in developing environmental management plans. Example 1 shows that when assessing nutrient behaviour in fluvial/estuarine depositional settings, it is important to examine the partitioning of phosphorus between grain size fractions to evaluate the sedimentological processes which control the dispersion and trapping of these contaminants. Example 2 shows that in studies of anthropogenic metal inputs to modern depositional settings, lateral and stratigraphic trends in sediment texture and mineralogy should be examined, in addition to trends in metal loads and evaluation of the prevailing physical, chemical and biological processes that may influence metal mobility and dispersion. Clearly, basic sedimentological data should form part of any assessment of potentially contaminated sites and part of investigations into the dispersion and trapping of contaminants in fluvial systems. These data are also required for rational environmental management to ensure that planning decisions are compatible with natural environmental constraints.

Human impact on the geomorphic evolution of the HOAL catchment, Lower Austria

NASA Astrophysics Data System (ADS)

Pöppl, Ronald; Kraushaar, Sabine; Strauss, Peter; Fuchs, Markus

2016-04-01

Since the beginning of human settlement extensive land cover and land use changes have induced significant geomorphic landscape changes as water and sediment dynamics have been transformed. The presented project focuses on the reconstruction of Holocene geomorphic landscape evolution and the assessment of recent geomorphic processes in the Northern foothills of the Eastern Alps in Austria - an area intensively agriculturally used since the middle ages and often overlooked in its geomorphic evolution. The study area is a small catchment (ca. 66 ha) which is located in the western part of Lower Austria comprising a land use history as well as environmental settings typical for wide regions across the Northern foothills of the Eastern Alps in Austria. The catchment elevation ranges from 268 to 323 m a.s.l. and has a mean slope angle of 8%. The climate in this region can be characterized as humid. The lithology mainly consists of Tertiary marly to sandy deposits which are superimposed by Quaternary sediments (e.g. loesses). Dominant soil types are Cambisols, Luvisols, and Planosols. Furthermore, the catchment is used as a Hydrological Open Air Laboratory (HOAL) implemented for the long-term research of water-related flow and transport processes in the landscape (http://hoal.hydrology.at). The main objective of this research project is to reconstruct Holocene landscape evolution by analyzing physical parameters of sediment cores taken from colluvial and alluvial sediment archives with additional 14C and OSL dating as well as by the measurement of truncated and covered standardized Luvisol profiles. First results will be presented at the EGU General Assembly 2016.

Precambrian fluvial deposits: Enigmatic palaeohydrological data from the c. 2 1.9 Ga Waterberg Group, South Africa

NASA Astrophysics Data System (ADS)

Eriksson, Patrick G.; Bumby, Adam J.; Brümer, Jacobus J.; van der Neut, Markus

2006-08-01

Precambrian fluvial systems, lacking the influence of rooted vegetation, probably were characterised by flashy surface runoff, low bank stability, broad channels with abundant bedload, and faster rates of channel migration; consequently, a braided fluvial style is generally accepted. Pre-vegetational braided river systems, active under highly variable palaeoclimatic conditions, may have been more widespread than are modern, ephemeral dry-land braided systems. Aeolian deflation of fine fluvial detritus does not appear to have been prevalent. With the onset of large cratons by the Neoarchaean-Palaeoproterozoic, very large, perennial braided river systems became typical. The c. 2.06-1.88 Ga Waterberg Group, preserved within a Main and a smaller Middelburg basin on the Kaapvaal craton, was deposited largely by alluvial/braided-fluvial and subordinate palaeo-desert environments, within fault-bounded, possibly pull-apart type depositories. Palaeohydrological data obtained from earlier work in the Middelburg basin (Wilgerivier Formation) are compared to such data derived from the correlated Blouberg Formation, situated along the NE margin of the Main basin. Within the preserved Blouberg depository, palaeohydrological parameters estimated from clast size and cross-bed set thickness data, exhibit rational changes in their values, either in a down-palaeocurrent direction, or from inferred basin margin to palaeo-basin centre. In both the Wilgerivier and Blouberg Formations, calculated palaeoslope values (derived from two separate formulae) plot within the gap separating typical alluvial fan gradients from those which characterise rivers (cf. [Blair, T.C., McPherson, J.G., 1994. Alluvial fans and their natural distinction from rivers based on morphology, hydraulic processes, sedimentary processes, and facies assemblages. J. Sediment. Res. A64, 450-489.]). Although it may be argued that such data support possibly unique fluvial styles within the Precambrian, perhaps related to a combination of major global-scale tectono-thermal and atmospheric-palaeoclimatic events, a simpler explanation of these apparently enigmatic palaeoslope values may be pertinent. Of the two possible palaeohydrological formulae for calculating palaeoslope, one provides results close to typical fluvial gradients; the other formula relies on preserved channel-width data. We suggest that the latter will not be reliable due to problematic preservation of original channel-widths within an active braided fluvial system. We thus find no unequivocal support for a unique fluvial style for the Precambrian, beyond that generally accepted for that period and discussed briefly in the first paragraph.

Deciphering Fluvial-Capture-Induced Erosional Patterns at the Continental Scale on the Iberian Peninsula

NASA Astrophysics Data System (ADS)

Anton, L.; Munoz Martin, A.; De Vicente, G.; Finnegan, N. J.

2017-12-01

The process of river incision into bedrock dictates the landscape response to changes in climate and bedrock uplift in most unglaciated settings. Hence, understanding processes of river incision into bedrock and their topographic signatures are a basic goal of geomorphology. Formerly closed drainage basins provide an exceptional setting for the quantification of long term fluvial dissection and landscape change, making them valuable natural laboratories. Internally drained basins are peculiar because they trap all the sediment eroded within the watershed; as closed systems they do not respond to the base level of the global ocean and deposition is the dominant process. In that context, the opening of an outward drainage involves a sudden lowering of the base level, which is transmitted upstream along fluvial channels in the form of erosional waves, leading to high incision and denudation rates within the intrabasinal areas. Through digital topographic analysis and paleolandscape reconstruction based on relict deposits and landscapes on the Iberian Peninsula, we quantify the volume of sediments eroded from formerly internally drained basins since capture. Mapping of fluvial dissection patterns reveals how, and how far, regional waves of incision have propagated upstream. In our analysis, erosional patterns are consistent with the progressive establishment of an outward drainage system, providing a relative capture chronology for the different studied basins. Divide migration inferred from chi maps supports the interpretations based on fluvial dissection patterns and volumes, providing clues on how landscaped changed and how drainage integration occurred within the studied watersheds. [Funded by S2013/MAE-2739 and CGL2014-59516].

Ecohydro-geomorphic implications of orographic precipitation on landform evolution using a landscape evolution model

NASA Astrophysics Data System (ADS)

Yetemen, O.; Saco, P. M.

2016-12-01

Orography induced precipitation and its implications on vegetation dynamics and landscape morphology have long been documented in the literature. However a numerical framework that integrates a range of ecohydrologic and geomorphic processes to explore the coupled ecohydro-geomorphic landscape response of catchments where pronounced orographic precipitation prevails has been missing. In this study, our aim is to realistically represent orographic-precipitation-driven ecohydrologic dynamics in a landscape evolution model (LEM). The model is used to investigate how ecohydro-geomorphic differences caused by differential precipitation patterns on the leeward and windward sides of low-relief landscapes lead to differences in the organization of modelled topography, soil moisture and plant biomass. We use the CHILD LEM equipped with a vegetation dynamics component that explicitly tracks above- and below-ground biomass, and a precipitation forcing component that simulates rainfall as a function of elevation and orientation. The preliminary results of the model show how the competition between an increased shear stress through runoff production and an enhanced resistance force due to denser canopy cover shape the landscape. Moreover, orographic precipitation leads to not only the migration of the divide between leeward and windward slopes but also a change in the concavity of streams. These results clearly demonstrate the strong coupling between landform evolution and climate processes.

Geomorphic controls on floodplain organic carbon storage in sediment along five rivers in interior Alaska

NASA Astrophysics Data System (ADS)

Lininger, K.; Wohl, E.; Rose, J. R.

2016-12-01

High latitude permafrost regions contain large amounts of organic carbon (OC) in the subsurface, but little work has quantified OC storage in floodplain sediment in the high latitudes. Floodplains influence the export of OC to the ocean by temporarily storing OC at timescales of 101 to 103 years. To fully understand terrestrial carbon cycling, the storage and residence time of OC in floodplains, and the geomorphic controls on OC storage, must be taken into account. Small-scale spatial variations in OC storage within floodplains likely reflect geomorphic processes of deposition and floodplain development. We present results of floodplain OC storage and residence time in sediment along 5 rivers in the Yukon Flats National Wildlife Refuge in interior Alaska, a region with discontinuous permafrost. We collected sediment samples within the active layer along tributaries to the Yukon River and the mainstem Yukon River and analyzed the sediment samples for OC content. We classified sample locations by geomorphic type (filled secondary channels, levees, point bars) and vegetation type (herbaceous, deciduous/shrub, white spruce, and black spruce wetlands), and found that both geomorphology and vegetation influence OC concentration and OC mass per area. Preliminary results suggest that filled secondary channels contain more OC per area compared to other geomorphic types. We present results of radiocarbon dates from river cutbanks associated with our sampling sites, which give a maximum age for residence times of OC in sediment before erosion and transport. The radiocarbon dates also provide estimates of long-term OC accretion within the Yukon Flats floodplains. Small-scale variations within floodplains as a result of floodplain depositional processes and vegetation communities shed light on the geomorphic controls on OC storage. This work will help constrain the spatial variation in OC storage and OC residence time across the landscape in a region experiencing rapid climate change and permafrost thaw.

The application of remotely sensed data to pedologic and geomorphic mapping on alluvial fan and playa surfaces in Saline Valley, California

NASA Technical Reports Server (NTRS)

Miller, D. A.; Petersen, G. W.; Kahle, A. B.

1986-01-01

Arid and semiarid regions yield excellent opportunities for the study of pedologic and geomorphic processes. The dominance of rock and soil exposure over vegetation not only provides the ground observer with observational possibilities but also affords good opportunities for measurement by aircraft and satellite remote sensor devices. Previous studies conducted in the area of pedologic and geomorphic mapping in arid regions with remotely sensed data have utilized information obtained in the visible to near-infrared portion of the spectrum. Thermal Infrared Multispectral Scanner (TIMS) and Thematic Mapping (TM) data collected in 1984 are being used in comjunction with maps compiled during a Bureau of Land Management (BLM) soil survey to aid in a detailed mapping of alluvial fan and playa surfaces within the valley. The results from this study may yield valuable information concerning the application of thermal data and thermal/visible data combinations to the problem of dating pedologic and geomorphic features in arid regions.

Origins of Sinuous and Braided Channels on Ascraeus Mons, Mars - A Keck Geology Consortium Undergraduate Research Project

NASA Technical Reports Server (NTRS)

de Wet, A. P.; Bleacher, J. E.; Garry, W. B.

2012-01-01

Water has clearly played an important part in the geological evolution of Mars. There are many features on Mars that were almost certainly formed by fluvial processes -- for example, the channels Kasei Valles and Ares Vallis in the Chryse Planitia area of Mars are almost certainly fluvial features. On the other hand, there are many channel features that are much more difficult to interpret -- and have been variously attributed to volcanic and fluvial processes. Clearly unraveling the details of the role of water on Mars is extremely important, especially in the context of the search of extinct or extant life. In this project we built on our recent work in determining the origin of one channel on the southwest rift apron of Ascraeus Mons. This project, funded by the Keck Geology Consortium and involving 4 undergraduate geology majors took advantage of the recently available datasets to map and analyze similar features on Ascraeus Mons and some other areas of Mars. A clearer understanding of how these particular channel features formed might lead to the development of better criteria to distinguish how other Martian channel features formed. Ultimately this might provide us with a better understanding of the role of volcanic and fluvial processes in the geological evolution of Mars.

Geomorphic and Hydrological challenges in Africa: implications for soil and water conservation

NASA Astrophysics Data System (ADS)

Vanmaercke, Matthias; Poesen, Jean

2017-04-01

Expected scenarios of climate change and population growth confront Africa with various important challenges related to food, water and energy security. Many of these challenges are closely linked to the impacts of soil erosion and other geomorphic processes, such as reduced crop yields, sedimentation of reservoirs and reduced freshwater quality. Despite the urgency and extent of many of these challenges, the causes and dynamics of these processes and their impacts remain severely understudied. This becomes apparent when the availability of e.g. soil erosion and catchment sediment export measurements for Africa is compared to that of other continents. Nonetheless, a substantial amount of geomorphic research has been conducted in Africa. Many of this work dates back from several decades ago, and were often only reported in 'gray literature' (e.g. internal reports). Here we present an overview of our current state of knowledge on soil erosion and its implications in Africa. We discuss which geomorphic process rate measurements are currently available and what can be learned from these with respect to the challenged raised above. We especially focus on our current understanding about the effectiveness of soil and water conservation techniques at various spatial and temporal scales. Based on specific case-studies (e.g. in Ethiopia and Uganda) and a meta-analysis of previous work, we highlight some research gaps, research needs and research opportunities when aiming to use Africa's soil and water resources sustainably and efficiently.

The waterfall paradox: How knickpoints disconnect hillslope and channel processes, isolating salmonid populations in ideal habitats

NASA Astrophysics Data System (ADS)

May, Christine; Roering, Josh; Snow, Kyle; Griswold, Kitty; Gresswell, Robert

2017-01-01

Waterfalls create barriers to fish migration, yet hundreds of isolated salmonid populations exist above barriers and have persisted for thousands of years in steep mountainous terrain. Ecological theory indicates that small isolated populations in disturbance-prone landscapes are at greatest risk of extirpation because immigration and recolonization are not possible. On the contrary, many above-barrier populations are currently thriving while their downstream counterparts are dwindling. This quandary led us to explore geomorphic knickpoints as a mechanism for disconnecting hillslope and channel processes by limiting channel incision and decreasing the pace of base-level lowering. Using LiDAR from the Oregon Coast Range, we found gentler channel gradients, wider valleys, lower gradient hillslopes, and less shallow landslide potential in an above-barrier catchment compared to a neighboring catchment devoid of persistent knickpoints. Based on this unique geomorphic template, above-barrier channel networks are less prone to debris flows and other episodic sediment fluxes. These above-barrier catchments also have greater resiliency to flooding, owing to wider valleys with greater floodplain connectivity. Habitat preference models further indicate that salmonid habitat is present in greater quantity and quality in these above-barrier networks. Therefore the paradox of the persistence of small isolated fish populations may be facilitated by a geomorphic mechanism that both limits their connectivity to larger fish populations yet dampens the effect of disturbance by decreasing connections between hillslope and channel processes above geomorphic knickpoints.

Geomorphic characterization of hilly relief in the north alpine foreland basin: The Hausruck- and Kobernaußerwald region

NASA Astrophysics Data System (ADS)

Baumann, Sebastian; Robl, Jörg; Keil, Melanie; Salcher, Bernhard

2014-05-01

The area of the Hausruck and Kobernaußerwald represents the highest relief of the Molasse Basin in Upper Austria. The region is characterized by a dissected landscape with elevation differences of 400 m and peaks reaching up to 800 m. The latest marine influence of this realm is dated to 11 Ma before present and constrains the onset of the inversion of the peripheral alpine foreland basin. Since that time the relief evolution is controlled by surface uplift and fluvial erosion. The Hausruck-Kobernaußerwald region forms a local watershed and is drained by three drainage systems that are tributaries of the Inn River, the Traun River and the Trattnach River. The Danube River represents the base level for all these streams. In contrary to the nearby Eastern Alps the study area shows no evidence for local deformation or glacial overprint. Therefore, the Hausruck- Kobernaußerwald region represents a perfect testing ground to explore the evolution of relief in a setting of regional uplift and relative base level lowering. This is done by characterizing the fluvial and hillslope system and exploring the effect of contrasting lithology and different base levels. We further give constraints on the geomorphological state of equilibrium and provide a discussion about the spatial position of the highest relief within the Molasse Basin in Upper Austria. Therefore, we have performed a series of morphometric analyses on a high resolution LiDAR digital elevation model. This includes longitudinal channel profiles, the best fit concavity index, the steepness and the normalized steepness index, the slope-area relationship, the slope elevation distribution and hypsometric curves of all individual catchments. All longitudinal channel profiles are graded and show a concave form without any natural knickpoints with best fit concavity indices in the range of 0.35 and 0.55. All observed knick points in the channel profiles could be traced back to an anthropogenic impact like bridges or culverts. Interestingly, the transition from one lithological unit to another does not influence the channel slopes in the profiles suggesting that the erodibility of different rock types is in the same order of magnitude. The contributing drainage area and channel slope for all catchments of the study area follow a power law relationship as proposed by Hack. The transition from hillslope- to fluvial processes is observed in channel slope-drainage area plots and is consistently identified in longitudinal channel profiles at very small drainage areas (A < 0.05 km²). Hypsometric curves commonly show a S-shaped form with hypsometric integrals close to 0.5 suggesting a topographic steady-state of the study area.

Proglacial deltaic landforms and stratigraphic architecture as a proxy for reconstructing past ice-sheet margin positions

NASA Astrophysics Data System (ADS)

Dietrich, Pierre; Ghienne, Jean-François; Normandeau, Alexandre; Lajeunesse, Patrick

2016-04-01

Deltaic landforms and related stratigraphic architectures are frequently used as proxy for reconstruction of past continental or marine environmental evolutions. Indeed, in addition to autocyclic processes, emplacement of deltaic systems is primarily controlled by changes in sediment supply and relative sea-level (RSL). In our study, we investigated several proglacial deltaic complexes emplaced since the last deglaciation over more than 700 km along the St. Lawrence North Shore (Québec, Canada). Their geomorphic and stratigraphic records allowed us to infer the retreat pattern of the Laurentide Ice Sheet fronts. Field investigation of representative deltaic complexes revealed an archetypal morphostratigraphic evolution forced by the retreat of the ice margin in a context of falling RSL (glacio-isostatic rebound). The base of the stratigraphic successions consists of outwash fan deposits emplaced in the early deglaciation when ice margin stillstanded immediately beyond the depositional area. The middle part of the succession consists of proglacial delta deposits corresponding to the retreat of the ice margin in the hinterland. At that time, glaciogenic supplies allowed an active progradation preventing fluvial entrenchment in spite of the forced regressive context. The upper part of the succession consists of staged shoreline deposits reworking the rim of the proglacial deltas. These deposits mark the retreat of the ice margin from the drainage basin and the subsequent drop in glaciogenics. Important fluvial entrenchment occurred in the same time, though rates of RSL fall were reduced. We generalize this stratigraphic framework by using solely the landforms (from DEM, aerial photographs or satellite images) tied to deltaic complex developments along the St. Lawrence North Shore. This approach permits an integrated study at the scale of the whole basin even where no field data is available. Recognizing the three steps evidenced from the stratigraphic record ads constrains on the successive ice margin positions through deglaciation. Top surface of the outwash fans, marking the deglaciation of the area, lies at or near the marine limit (highest altitude reached by the post-glacial sea) and is commonly flat; the top surface of the proglacial deltas, recording the upland recession of the ice margin, is gently-sloped basinward, without evidence of fluvial entrenchment; finally, the top surface of coastal deposits, marking the retreat of the ice margin from the drainage basin, is characterized by raised beaches incised by meandering rivers. Determining ages of these successive landforms (14C dating, sea-level curves) allowed us to reconstruct the pattern of ice-sheet retreat since the Younger Dryas up to almost the final disappearance of the Quebec Ice Dome at ~6 kyr BP.

The response of source-bordering aeolian dunefields to sediment-supply changes 2: Controlled floods of the Colorado River in Grand Canyon, Arizona, USA

USGS Publications Warehouse

Sankey, Joel B.; Caster, Joshua; Kasprak, Alan; East, Amy

2018-01-01

In the Colorado River downstream of Glen Canyon Dam in the Grand Canyon, USA, controlled floods are used to resupply sediment to, and rebuild, river sandbars that have eroded severely over the past five decades owing to dam-induced changes in river flow and sediment supply. In this study, we examine whether controlled floods, can in turn resupply aeolian sediment to some of the large source-bordering aeolian dunefields (SBDs) along the margins of the river. Using a legacy of high-resolution lidar remote-sensing and meteorological data, we characterize the response of four SBDs (a subset of 117 SBDs and other aeolian-sand-dominated areas in the canyon) during four sediment-laden controlled floods of the Colorado River in 2012, 2013, 2014, and 2016. We find that aeolian sediment resupply unambiguously occurred in 8 of the 16 instances of controlled flooding adjacent to SBDs. Resupply attributed to individual floods varied substantially among sites, and occurred with four, three, one, and zero floods at the four sites, respectively. We infer that the relative success of controlled floods as a regulated-river management tool for resupplying sediment to SBDs is analogous to the frequency of resupply observed for fluvial sandbars in this setting, in that sediment resupply was estimated to have occurred for roughly half of the instances of recent controlled flooding at sandbars monitored separately from this study. We find the methods developed in this, and a companion study, are effective tools to quantify geomorphic changes in sediment storage, along linked fluvial and aeolian pathways of sedimentary systems.

The response of source-bordering aeolian dunefields to sediment-supply changes 2: Controlled floods of the Colorado River in Grand Canyon, Arizona, USA

NASA Astrophysics Data System (ADS)

Sankey, Joel B.; Caster, Joshua; Kasprak, Alan; East, Amy E.

2018-06-01

In the Colorado River downstream of Glen Canyon Dam in the Grand Canyon, USA, controlled floods are used to resupply sediment to, and rebuild, river sandbars that have eroded severely over the past five decades owing to dam-induced changes in river flow and sediment supply. In this study, we examine whether controlled floods, can in turn resupply aeolian sediment to some of the large source-bordering aeolian dunefields (SBDs) along the margins of the river. Using a legacy of high-resolution lidar remote-sensing and meteorological data, we characterize the response of four SBDs (a subset of 117 SBDs and other aeolian-sand-dominated areas in the canyon) during four sediment-laden controlled floods of the Colorado River in 2012, 2013, 2014, and 2016. We find that aeolian sediment resupply unambiguously occurred in 8 of the 16 instances of controlled flooding adjacent to SBDs. Resupply attributed to individual floods varied substantially among sites, and occurred with four, three, one, and zero floods at the four sites, respectively. We infer that the relative success of controlled floods as a regulated-river management tool for resupplying sediment to SBDs is analogous to the frequency of resupply observed for fluvial sandbars in this setting, in that sediment resupply was estimated to have occurred for roughly half of the instances of recent controlled flooding at sandbars monitored separately from this study. We find the methods developed in this, and a companion study, are effective tools to quantify geomorphic changes in sediment storage, along linked fluvial and aeolian pathways of sedimentary systems.

Geomorphological assessment of sediment contamination in an urban stream system

USGS Publications Warehouse

Rhoads, B.L.; Cahill, R.A.

1999-01-01

Little is known about the influence of fluvial-geomorphological features on the dispersal of sediment-related contaminants in urban drainage systems. This study investigates the relation between reach-scale geomorphological conditions and network-scale patterns of trace-element concentrations in a partially urbanized stream system in East-Central Illinois, USA Robust statistical analysis of bulk sediment samples reveals levels of Cr, Cu, Pb, Ni, and Zn exceed contamination thresholds in the portion of the watershed in close proximity to potential sources of pollution-in this case storm-sewer outfalls. Although trace-element concentrations decrease rapidly downstream from these sources, substantial local variability in metal levels exists within contaminated reaches. This local variability is related to reach-scale variation in fluvial-geomorphic conditions, which in turn produces variation in the degree of sorting and organic-matter content of bed material. Metal concentrations at contaminated sites also exhibit considerable variability over time. Analytical tests on specific size fractions of material collected at a highly contaminated site indicate that Cr and Ni are concentrated in the 0.063 to 0.250 mm fraction of the sediment. This fraction also has elevated concentration of Zr. SEM analysis shows that the fine sand fraction contains shards of stainless steel within a matrix of zircon sand, an industrial material associated with a nearby alloy casting operation. Samples of suspended load and bedload at the contaminated site also have elevated amounts of trace metals, but concentrations of Ni and Cr in the bedload are less than concentrations in the bed material, suggesting that these trace elements are relatively immobile. Off the other hand, amounts of CU and Zn in the bedload exceed concentrations in the bed material, implying that these trace metals are preferentially mobilized during transport events.

Boundary Conditions for Aeolian Activity in North American Dune Fields

NASA Astrophysics Data System (ADS)

Halfen, A. F.; Lancaster, N.; Wolfe, S.

2014-12-01

Geomorphic and chronological data for dune fields are evaluated for three contrasting areas of North America: 1) the Prairie-Parkland-Boreal ecozones of the northern Great Plains in Canada; 2) the Central Great Plains of the USA; and 3) the deserts of southwestern USA and northern Mexico. Luminescence and radiocarbon ages for periods of dune accumulation and stability are compared with palaeoenvironment proxies to provide an assessment of the boundary conditions of dune system response to changes in sediment supply, availability, and mobility. Dune fields in the northern Great Plains were formed from sediment originating from glaciofluvial or glaciolacustrine sediments deposited during deglaciation 16-11 ka. Subsequent aeolian deposition occurred in Parkland and Prairie dune fields as a result of mid-Holocene (8-5 ka) and late-Holocene (< 3.5 ka) activity related to drought conditions that reworked pre-existing aeolian sands. In the Central Great Plains, dune fields are closely linked to fluvial sediment sources. Sediment supply was high during deglaciation of the Rocky Mountains and resulted in widespread dune construction 16-10 ka. Multiple periods of Holocene reactivation are recorded and reflect increased sediment availability during drought episodes. Dune fields in the southwestern deserts experienced periods of construction as a result of enhanced supply of sediment from fluvial and lacustrine sources during the period 11.8-8 ka and at multiple intervals during the late Holocene. Despite spatial and temporal gaps in chronometric data as a result of sampling biases, the record from North American dune fields indicates the strong influence of sediment supply on dune construction, with changes in sediment availability as a result of drought episodes resulting in dune field reactivation and reworking of pre-existing sediment.

Fluvial processes in Ma'adim Vallis and the potential of Gusev crater as a high priority site

NASA Technical Reports Server (NTRS)

Cabrol, Nathalie; Landheim, Ragnild; Greeley, Ronald; Farmer, Jack

1994-01-01

According to exobiology site selection criteria for Mars, the search for potential extinct/extant water dependent life should focus on sites were water flowed and ponded. The Ma'adim Vallis/Gusev crater system is of high priority for exobiology research, because it appears to have involved long term flooding, different periods and rates of sedimentation, and probable episodic ponding. The topics covered include the following: evidence of nonuniform fluvial processes and early overflooding of the plateau and ponding.

Natural and human forcing in recent geomorphic change; case studies in the Rio de la Plata basin.

PubMed

Bonachea, Jaime; Bruschi, Viola M; Hurtado, Martín A; Forte, Luis M; da Silva, Mario; Etcheverry, Ricardo; Cavallotto, José L; Dantas, Marcilene F; Pejon, Osni J; Zuquette, Lázaro V; Bezerra, Maria Angélica de O; Remondo, Juan; Rivas, Victoria; Gómez-Arozamena, José; Fernández, Gema; Cendrero, Antonio

2010-06-01

An analysis of geomorphic system's response to change in human and natural drivers in some areas within the Río de la Plata basin is presented. The aim is to determine whether an acceleration of geomorphic processes has taken place in recent years and, if so, to what extent it is due to natural (climate) or human (land-use) drivers. Study areas of different size, socio-economic and geomorphic conditions have been selected: the Río de la Plata estuary and three sub-basins within its watershed. Sediment cores were extracted and dated ((210)Pb) to determine sedimentation rates since the end of the 19th century. Rates were compared with time series on rainfall as well as human drivers such as population, GDP, livestock load, crop area, energy consumption or cement consumption, all of them related to human capacity to disturb land surface. Data on river discharge were also gathered. Results obtained indicate that sedimentation rates during the last century have remained essentially constant in a remote Andean basin, whereas they show important increases in the other two, particularly one located by the São Paulo metropolitan area. Rates in the estuary are somewhere in between. It appears that there is an intensification of denudation/sedimentation processes within the basin. Rainfall remained stable or varied very slightly during the period analysed and does not seem to explain increases of sedimentation rates observed. Human drivers, particularly those more directly related to capacity to disturb land surface (GDP, energy or cement consumption) show variations that suggest human forcing is a more likely explanation for the observed change in geomorphic processes. It appears that a marked increase in denudation, of a "technological" nature, is taking place in this basin and leading to an acceleration of sediment supply. This is coherent with similar increases observed in other regions. Copyright (c) 2010 Elsevier B.V. All rights reserved.

A GIS-Based Model for the analysis of an urban flash flood and its hydro-geomorphic response. The Valencia event of 1957

NASA Astrophysics Data System (ADS)

Portugués-Mollá, I.; Bonache-Felici, X.; Mateu-Bellés, J. F.; Marco-Segura, J. B.

2016-10-01

Flash floods are recurrent events around the Mediterranean region. Extreme episodes activate hydro-geomorphic high-intensity processes with low frequency. In urban environments, the complexity becomes higher due to the existence of very quick-response runoff. However, immediate recovery works remove the urban marks. After a short time both the significance and magnitude of the hydro-geomorphic event become completely unrecognizable. Nevertheless, these episodes generate extensive documentation which is testimony of the processes in almost real time. It is necessary to exploit this source typology in order to draw flood sketches when events far in time may lack a sufficiently rich database. This is particularly the case for the Valencia flash flood (October 1957), located in the lower Turia River basin (Eastern Spain). It left numerous pieces of hydro-geomorphic evidence, but its tracks were covered a short while after the flood. In any case, it remains part of a non-systematic legacy that has not yet been exploited, consisting of immediate aerial and oblique high resolution photography, pictures at street level, water marks and administrative records. Paradoxically, despite being considered a milestone in metropolitan territorial planning (the river was definitely diverted), an accurate reconstruction of the hydraulic behaviour was required from an integrated point of view. To this aim, the development of a GIS-Based Model enabled the utilisation of the above-mentioned materials. This non-conventional information was treated jointly from a new perspective. It provided database support through a vast amount of organised, structured and georeferenced information about the 1957 event. In a second stage, the GBM made it possible to characterise the Turia urban reach and interpret both the hydro-geomorphic (trenches along barrier beaches, erosion, deposition, etc.) and hydraulic (urban streams along the streets, flow directions, flood extent, levees breaks, overflows and inflows, etc.) processes mainly through photo-interpretation.

River Sensitivity and Catchment Connectivity: Key Controls on Geomorphic Response and Effectiveness

NASA Astrophysics Data System (ADS)

Lisenby, P.; Fryirs, K.; Croke, J.

2016-12-01

The sensitivity of river channels to adjustment and the dynamics of sediment connectivity along a channel network are key controls on the capacity (ability) for a river system to adjust, i.e. the severity, distribution, and type of geomorphic response to disturbance events. In turn, the cumulative impact of geomorphic responses compared with event magnitude will determine the geomorphic effectiveness of a single disturbance event. River sensitivity and sediment connectivity can change significantly over space and time, and vary with changes in internal factors such as channel type and geomorphic landform and external factors such as event sequencing and lithological controls. Correspondingly, the capacity for a geomorphic system to respond to disturbance events will also vary, so that geomorphic effectiveness is not definitively characterized by a static relationship between event magnitude and geomorphic response, but rather is a dynamic comparison between geomorphic response and an actively changing capacity for geomorphic adjustment. Herein, we use the Lockyer Valley, Queensland as a case study to illustrate the variability of river sensitivity and sediment connectivity. We relate this variability to the potential and capacity for geomorphic channel response. We find that the sensitivity to and capacity for geomorphic adjustment varies significantly with channel morphometry and valley position. Additionally, the nature of bedload sediment connectivity changes with the distribution of geomorphic landforms and channel weirs that can impede sediment transference through the system. This variability of river sensitivity and sediment connectivity will control the nature of geomorphic response to disturbance events within the Lockyer Valley. Ultimately, determinations of geomorphic effectiveness for disturbance events will depend on comparisons of their geomorphic impacts with the capacity of the Lockyer geomorphic system to respond.

Controls and variability of solute and sedimentary fluxes in Antarctic and sub-Antarctic Environments

NASA Astrophysics Data System (ADS)

Zwolinski, Zbigniew

2015-04-01

The currently prepared SEDIBUD Book on "Source-to-Sink Fluxes in Undisturbed Cold Environments" (edited by Achim A. Beylich, John C. Dixon and Zbigniew Zwolinski and published by Cambridge University Press) is summarizing and synthesizing the achievements of the International Association of Geomorphologists` (I.A.G./A.I.G.) Working Group SEDIBUD (Sediment Budgets in Cold Environments), which has been active since 2005 (http://www.geomorph.org/wg/wgsb.html). The book comprises five parts. One of them is part about sub-Antarctic and Antarctic Environments. This part "Sub-Antarctic and Antarctic Environments" describes two different environments, namely oceanic and continental ones. Each part contains results of research on environmental drivers and rates of contemporary solute and sedimentary fluxes in selected sites. Apart from describing the environmental conditions of the whole continent of Antarctica and sub-Antarctic islands (Zb.Zwolinski, M.Kejna, A.N.Lastochkin, A.Zhirov, S.Boltramovich) this part of the book characterizes terrestrial polar oases free from multi-year ice and snow covers (Zb.Zwolinski). The detailed results of geoecological and sedimentological research come from different parts of Antarctica. Antarctic continental shelf (E.Isla) is an example of sub-Antarctic oceanic environment. South Shetlands, especially King George Island (Zb.Zwolinski, M.Kejna, G.Rachlewicz, I.Sobota, J.Szpikowski), is an example of sub-Antarctic terrestrial environment. Antarctic Peninsula (G.Vieira, M.Francelino, J.C.Fernandes) and surroundings of McMurdo Dry Valleys (W.B.Lyons, K.A.Welch, J.Levy, A.Fountain, D.McKnight) are examples of Antarctic continental environments. The key goals of the Antarctic and sub-Antarctic book chapters are following: (i) identify the main environmental drivers and rates of contemporary solute and sedimentary fluxes, and (ii) model possible effects of projected climate change on solute and sedimentary fluxes in cold climate environments. Solute and sediment transport in the streams of analyzed environments are constrained by the relatively short water runoff season that typically lasts from a few weeks to maximum of four months during the austral summer, for Antarctic and sub-Antarctic regions respectively. Because of high intensity of mechanical and chemical weathering processes solute and sediment transport are rather high within Antarctic environments. Weathering rates on slopes and magnitude of fluvial transport in relatively short streams control the intensity of denudational processes. Both mechanical and chemical denudation varies highly through sub-Antarctic and Antarctic environments. To generate accurate predictions of fluvial and denudational processes we must fully understand the actual geoecological processes, which in some places are under rapid change, e.g., the Antarctic Peninsula and sub-Antarctic islands.

Modelling the impact of dam removal on geomorphic channel response and sediment delivery: an Austrian case study

NASA Astrophysics Data System (ADS)

Pöppl, Ronald; Coulthard, Tom; Keesstra, Saskia; Keiler, Margreth

2015-04-01

Dams are often considered to have the most significant impact on rivers as dam construction generally reduces downstream sediment fluxes which further involves geomorphic changes in the affected river reaches. Since many dams no longer fulfill their intended purpose (e.g. due to siltation), are dangerous (e.g. catastrophic dam failures) and/or are ecologically damaging (e.g. habitat destruction), within the last two decades several dams have been removed and many more are already proposed for removal. Unfortunately, there is still only little empirical knowledge about the geomorphic consequences of dam removals and the related sediment release which represents a big challenge for river management. Modelling is one way to approach this problem. In the presented study we modelled the impacts of dam removal on geomorphic channel processes, channel morphology and sediment delivery further considering the role of channel engineering measures and reservoir excavation within a river reach impacted by a series of dams using the landscape evolution model CAESAR-Lisflood. The model was run with data from a small catchment located in Lower Austria. Modelled geomorphic channel changes and sediment fluxes were spatio-temporally analyzed, related to real-world data and are discussed in the context of river management issues.

Coastal geomorphology through the looking glass

NASA Astrophysics Data System (ADS)

Sherman, Douglas J.; Bauer, Bernard O.

1993-07-01

Coastal geomorphology will gain future prominence as environmentally sound coastal zone management strategies, requiring scientific information, begin to supplant engineered shoreline stabilization schemes for amelioration of coastal hazards. We anticipate substantial change and progress over the next two decades, but we do not predict revolutionary advances in theoretical understanding of coastal geomorphic systems. Paradigm shifts will not occur; knowledge will advance incrementally. We offer predictions for specific coastal systems delineated according to scale. For the surf zone, we predict advances in wave shoaling theory, but not for wave breaking. We also predict greater understanding of turbulent processes, and substantive improvements in surf-zone circulation and radiation stress models. Very few of these improvements are expected to be incorporated in geomorphic models of coastal processes. We do not envision improvements in the theory of sediment transport, although some new and exciting empirical observations are probable. At the beach and nearshore scale, we predict the development of theoretically-based, two- and three-dimensional morphodynamical models that account for non-linear, time-dependent feedback processes using empirically calibrated modules. Most of the geomorphic research effort, however, will be concentrated at the scale of littoral cells. This scale is appropriate for coastal zone management because processes at this scale are manageable using traditional geomorphic techniques. At the largest scale, little advance will occur in our understanding of how coastlines evolve. Any empirical knowledge that is gained will accrue indirectly. Finally, we contend that anthropogenic influences, directly and indirectly, will be powerful forces in steering the future of Coastal Geomorphology. "If you should suddenly feel the need for a lesson in humility, try forecasting the future…" (Kleppner, 1991, p. 10).

Experimental evidence of reorganizing landscape under changing climatic forcing

NASA Astrophysics Data System (ADS)

Singh, A.; Tejedor, A.; Zaliapin, I. V.; Reinhardt, L.; Foufoula-Georgiou, E.

2015-12-01

Quantification of the dynamics of landscape reorganization under changing climatic forcing is important to understand geomorphic transport laws under transient conditions, assess response of landscapes to external perturbations for future predictive modeling, and for interpreting past climate from stratigraphic record. For such an analysis, however, real landscape observations are limited. To this end, a series of controlled laboratory experiments on evolving landscape were conducted at the St. Anthony Falls laboratory at the University of Minnesota. High resolution elevation data at a temporal resolution of 5 mins and spatial resolution of 0.5 mm were collected as the landscape approached steady state (constant uplift and precipitation rate) and in the transient state (under the same uplift and 5 times precipitation rate). Our results reveal rapid topographic re-organization under a five-fold increase in precipitation with the fluvial regime encroaching into the previously debris dominated regime, widening and aggradation of channels and valleys, and accelerated erosion happening at hillslope scales. To better understand the initiation of the observed reorganization, we perform a connectivity and clustering analysis of the erosional and depositional events, showing strikingly different spatial patterns on landscape evolution under steady-state (SS) and transient-state (TS), even when the time under SS is renormalized to match the total volume of eroded and deposited sediment in TS. Our results suggest a regime shift in the behavior of transport processes on the landscape at the intermediate scales i.e., from supply-limited to transport-limited.

Potential interaction between transport and stream networks over the lowland rivers in Eastern India.

PubMed

Roy, Suvendu; Sahu, Abhay Sankar

2017-07-15

Extension of transport networks supports good accessibility and associated with the development of a region. However, transport lines have fragmented the regional landscape and disturbed the natural interplay between rivers and their floodplains. Spatial analysis using multiple buffers provides information about the potential interaction between road and stream networks and their impact on channel morphology of a small watershed in the Lower Gangetic Plain. Present study is tried to understand the lateral and longitudinal disconnection in headwater stream by rural roads with the integration of geoinformatics and field survey. Significant (p < 0.001) growth of total road length and number of road-stream crossing in the last five decades (1970s-2010s) contribute to making longitudinal and lateral disconnection in the fluvial system of Kunur River Basin. Channel geometry from ten road-stream crossings shows significant (p = 0.01) differences between upstream and downstream of crossing structure and created problems like downstream scouring, increased drop height at outlet, formation of stable bars, severe bank erosion, and make barriers for river biota. The hydro-geomorphic processes are also adversely affected due to lateral disconnection and input of fine to coarse sediments from the river side growth of unpaved road (1922%). Limited streamside development, delineation of stream corridor, regular monitoring and engineering efficiency for the construction of road and road-stream crossing might be effective in managing river geomorphology and riverine landscape. Copyright © 2017 Elsevier Ltd. All rights reserved.

Middle and Late Pleistocene glaciations in the southwestern Pamir and their effects on topography [Topography of the SW Pamir shaped by middle-late Pleistocene glaciation

DOE PAGES

Stübner, Konstanze; Grin, Elena; Hidy, Alan J.; ...

2017-03-27

Glacial chronologies provide insight into the evolution of paleo-landscapes, paleoclimate, topography, and the erosion processes that shape mountain ranges. In the Pamir of Central Asia, glacial morphologies and deposits indicate extensive past glaciations, whose timing and extent remain poorly constrained. Geomorphic data and 15 new 10Be exposure ages from moraine boulders and roches moutonnées in the southwestern Pamir document multiple Pleistocene glacial stages. The oldest exposure ages, View the MathML source113 ± 10ka, underestimate the age of the earliest preserved glacial advance and imply that the modern relief of the southwestern Pamir (peaks at ~5000–6000 m a.s.l.; valleys at ~2000–3000more » m a.s.l.) already existed in the late Middle Pleistocene. Younger exposure ages (~40–80 ka, ~30 ka) complement the existing Central Asian glacial chronology and reflect successively less extensive Late Pleistocene glaciations. The topography of the Pamir and the glacial chronologies suggest that, in the Middle Pleistocene, an ice cap or ice field occupied the eastern Pamir high-altitude plateau, whereas westward flowing valley glaciers incised the southwestern Pamir. Since the Late Pleistocene deglaciation, the rivers of the southwestern Pamir adjusted to the glacially shaped landscape. As a result, localized rapid fluvial incision and drainage network reorganization reflect the transient nature of the deglaciated landscape.« less

Middle and Late Pleistocene glaciations in the southwestern Pamir and their effects on topography [Topography of the SW Pamir shaped by middle-late Pleistocene glaciation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stübner, Konstanze; Grin, Elena; Hidy, Alan J.

Glacial chronologies provide insight into the evolution of paleo-landscapes, paleoclimate, topography, and the erosion processes that shape mountain ranges. In the Pamir of Central Asia, glacial morphologies and deposits indicate extensive past glaciations, whose timing and extent remain poorly constrained. Geomorphic data and 15 new 10Be exposure ages from moraine boulders and roches moutonnées in the southwestern Pamir document multiple Pleistocene glacial stages. The oldest exposure ages, View the MathML source113 ± 10ka, underestimate the age of the earliest preserved glacial advance and imply that the modern relief of the southwestern Pamir (peaks at ~5000–6000 m a.s.l.; valleys at ~2000–3000more » m a.s.l.) already existed in the late Middle Pleistocene. Younger exposure ages (~40–80 ka, ~30 ka) complement the existing Central Asian glacial chronology and reflect successively less extensive Late Pleistocene glaciations. The topography of the Pamir and the glacial chronologies suggest that, in the Middle Pleistocene, an ice cap or ice field occupied the eastern Pamir high-altitude plateau, whereas westward flowing valley glaciers incised the southwestern Pamir. Since the Late Pleistocene deglaciation, the rivers of the southwestern Pamir adjusted to the glacially shaped landscape. As a result, localized rapid fluvial incision and drainage network reorganization reflect the transient nature of the deglaciated landscape.« less

Post Impact Mars Climate Simulations Using a GCM

NASA Technical Reports Server (NTRS)

Colaprete, A.; Haberle, R. M.; Segura, T. L.; Toon, O. B.; Zahnle, K.

2003-01-01

The first images returned by the Mariner 7 spacecraft of the Martian surface showed a landscape heavily scared by impacts. Mariner 9 imaging revealed geomorphic features including valley networks and outflow channels that suggest liquid water once flowed at the surface of Mars. Further evidence for water erosion and surface modification has come from the Viking Spacecraft, Mars Pathfinder and Mars Global Surveyor's (MGS) Mars Obiter Camera (MOC). This evidence includes apparent paleolake beds, fluvial fans and sedimentary layers (Cabrol and Grinn, 1999; Heberle et al., 2001). There is evidence for subsurface water as well. Rampart crates suggest an abundance of water in the near surface regolith (Mouginis-Mark, 1986). The estimated erosion rates necessary to explain the observed surface morphologies (Golombek and Bridges, 2000) present a conundrum. The rates of erosion appear to be highest when the early sun was fainter and only 75% as luminous as it is today. Furthermore the rates of erosion appear to correlate with the rate at which Mars was impacted (Carr and Waenke, 1992). All of this evidence suggests to a very different climate than what exists on Mars today.

Relict drainages, conical hills, and the eolian veneer in southwest Egypt - Applications to Mars

NASA Technical Reports Server (NTRS)

Breed, C. S.; Mccauley, J. F.; Grolier, M. J.

1982-01-01

The fluvial and mass wasting origin of the particles in the eolian deposits, the segregation of these materials on the basis of grain size, and the migration of those particles capable of saltation to areas of accumulation in lowland basins of the Sahara are suggested as analogs for the formation and accumulation of 'sand' sheets and dunes on the northern plains and in the polar erg on Mars. Outliers of the Martian plateau in the fretted terrain are seen as having been dissected, at least initially, by channels whose upstream portions are incised in the uplands. The Martian 'wadis' possess many geomorphic peculiarities similar to those of the Gilf (Gilf Kebir Plateau, southwest Egypt) wadis, and like the Egyptian features they have been attributed to mass wasting. Even though basal sapping and removal of debris by wind have almost certainly modified the Martian features, their deep incision in the plateau and their inferred northward extensions in the northern plains are thought to require not only initial downcutting by fairly energetic streams but also prolonged and long-distance flow of water.

The geologic history of Margaritifer basin, Mars

USGS Publications Warehouse

Salvatore, M. R.; Kraft, M. D.; Edwards, Christopher; Christensen, P.R.

2016-01-01

In this study, we investigate the fluvial, sedimentary, and volcanic history of Margaritifer basin and the Uzboi-Ladon-Morava (ULM) outflow channel system. This network of valleys and basins spans more than 8000 km in length, linking the fluvially dissected southern highlands and Argyre Basin with the northern lowlands via Ares Vallis. Compositionally, thermophysically, and morphologically distinct geologic units are identified and are used to place critical relative stratigraphic constraints on the timing of geologic processes in Margaritifer basin. Our analyses show that fluvial activity was separated in time by significant episodes of geologic activity, including the widespread volcanic resurfacing of Margaritifer basin and the formation of chaos terrain. The most recent fluvial activity within Margaritifer basin appears to terminate at a region of chaos terrain, suggesting possible communication between surface and subsurface water reservoirs. We conclude with a discussion of the implications of these observations on our current knowledge of Martian hydrologic evolution in this important region.

The geologic history of Margaritifer basin, Mars

NASA Astrophysics Data System (ADS)

Salvatore, M. R.; Kraft, M. D.; Edwards, C. S.; Christensen, P. R.

2016-03-01

In this study, we investigate the fluvial, sedimentary, and volcanic history of Margaritifer basin and the Uzboi-Ladon-Morava outflow channel system. This network of valleys and basins spans more than 8000 km in length, linking the fluvially dissected southern highlands and Argyre basin with the northern lowlands via Ares Vallis. Compositionally, thermophysically, and morphologically distinct geologic units are identified and are used to place critical relative stratigraphic constraints on the timing of geologic processes in Margaritifer basin. Our analyses show that fluvial activity was separated in time by significant episodes of geologic activity, including the widespread volcanic resurfacing of Margaritifer basin and the formation of chaos terrain. The most recent fluvial activity within Margaritifer basin appears to terminate at a region of chaos terrain, suggesting possible communication between surface and subsurface water reservoirs. We conclude with a discussion of the implications of these observations on our current knowledge of Martian hydrologic evolution in this important region.

Long term landscape evolution within central Apennines (Italy): Marsica and Peligna region morphotectonics and surface processes

NASA Astrophysics Data System (ADS)

Miccadei, E.; Piacentini, T.; Berti, C.

2010-12-01

The relief features of the Apennines have been developed in a complex geomorphological and geological setting from Neogene to Quaternary. Growth of topography has been driven by active tectonics (thrust-related crustal shortening and high-angle normal faulting related to crustal extension), regional rock uplift, and surface processes, starting from Late Miocene(?) - Early Pliocene. At present a high-relief landscape is dominated by morphostructures including high-standing, resistant Mesozoic and early Tertiary carbonates ridges (i.e. thrust ridges, faulted homocline ridges) and intervening, erodible Tertiary siliciclastics valleys (i.e. fault line valleys) and Quaternary continental deposits filled basins (i.e. tectonic valleys, tectonic basins). This study tries to identify paleo-uplands that may be linked to paleo-base levels and aims at the reconstruction of ancient landscapes since the incipient phases of morphogenesis. It analyzes the role of tectonics and morphogenic processes in the long term temporal scale landscape evolution (i.e. Mio?-Pliocene to Quaternary). It is focused on the marsicano-peligna region, located along the main drainage divide between Adriatic side and Tyrrhenian side of Central Apennines, one of the highest average elevation area of the whole chain. The work incorporates GIS-based geomorphologic field mapping of morphostructures and Quaternary continental deposits, and plano-altimetric analysis and morphometry (DEM-, map-based) of the drainage network (i.e. patterns, hypsometry, knick points, Ks). Field mapping give clues on the definition of paleo-landscapes related to different paleo-morpho-climatic environments (i.e. karst, glacial, slope, fluvial). Geomorphological evidence of tectonics and their cross-cutting relationships with morphostructures, continental deposits and faults, provide clues on the deciphering of the reciprocal relationship of antecedence of the paleo-landscapes and on the timing of morphotectonics. Morphotectonic features are related to Neogene thrusts, reactivated or displaced by complex kinematic strike slip and followed by extensional tectonic features (present surface evidence given by fault line scarps, fault line valleys, fault scarps, fault slopes, wind gaps, etc.). Geomorphic evidence of faults is provided also by morphometry of the drainage network: highest long slope of the main streams (knick points and Ks) are located where the streams cut across or run along recent faults. Correlation of tectonic elements, paleosurfaces, Quaternary continental deposits, by means of morphotectonic cross sections, lead to the identification, in the marsicano-peligna region, of areas in which morphotectonics acted in the same period, becoming younger moving from the West to the East. In conclusion, recognition of different morphotectonic features, identification of different paleo-landscapes, and reconstruction of their migration history, contribute to define the main phases of syn and post orogenic, Apennine chain landscape evolution: it results from the link of alternating morphotectonics and surface processes, due to migrating fault activity, rock uplift processes and alternating karst, glacial, slope, fluvial processes.

Developing a post-fire flood chronology and recurrence probability from alluvial stratigraphy in the Buffalo Creek watershed, Colorado, USA

USGS Publications Warehouse

Elliott, J.G.; Parker, R.S.

2001-01-01

Stratigraphic and geomorphic evidence indicate floods that occur soon after forest fires have been intermittent but common events in many mountainous areas during the past several thousand years. The magnitude and recurrence of these post-fire flood events reflects the joint probability between the recurrence of fires and the recurrence of subsequent rainfall events of varying magnitude and intensity. Following the May 1996 Buffalo Creek, Colorado, forest fire, precipitation amounts and intensities that generated very little surface runoff outside of the burned area resulted in severe hillslope erosion, floods, and streambed sediment entrainment in the rugged, severely burned, 48 km2 area. These floods added sediment to many existing alluvial fans, while simultaneously incising other fans and alluvial deposits. Incision of older fans revealed multiple sequences of fluvially transported sandy gravel that grade upward into charcoal-rich, loamy horizons. We interpret these sequences to represent periods of high sediment transport and aggradation during floods, followed by intervals of quiescence and relative stability in the watershed until a subsequent fire occurred. An alluvial sequence near the mouth of a tributary draining a 0??82 km2 area indicated several previous post-fire flood cycles in the watershed. Dendrochronologic and radiocarbon ages of material in this deposit span approximately 2900 years, and define three aggradational periods. The three general aggradational periods are separated by intervals of approximately nine to ten centuries and reflect a 'millennium-scale' geomorphic response to a closely timed sequence of events: severe and intense, watershed-scale, stand-replacing fires and subsequent rainstorms and flooding. Millennium-scale aggradational units at the study site may have resulted from a scenario in which the initial runoff from the burned watershed transported and deposited large volumes of sediment on downstream alluvial surfaces and tributary fans. Subsequent storm runoff may have produced localized incision and channelization, preventing additional vertical aggradation on the sampled alluvial deposit for several centuries. Two of the millennium-scale aggradational periods at the study site consist of multiple gravel and loam sequences with similar radiocarbon ages. These closely dated sequences may reflect a 'multidecade-scale' geomorphic response to more frequent, but aerially limited and less severe fires, followed by rainstorms of relatively common recurrence. Published in 2001 by John Wiley and Sons, Ltd.

Field Investigation of Flow Structure and Channel Morphology at Confluent-Meander Bends

NASA Astrophysics Data System (ADS)

Riley, J. D.; Rhoads, B. L.

2007-12-01

The movement of water and sediment through drainage networks is inevitably influenced by the convergence of streams and rivers at channel confluences. These focal components of fluvial systems produce a complex hydrodynamic environment, where rapid changes in flow structure and sediment transport occur to accommodate the merging of separate channel flows. The inherent geometric and hydraulic change at confluences also initiates the development of distinct geomorphic features, reflected in the bedform and shape of the channel. An underlying assumption of previous experimental and theoretical models of confluence dynamics has been that converging streams have straight channels with angular configurations. This generalized conceptualization was necessary to establish confluence planform as symmetrical or asymmetrical and to describe subsequent flow structure and geomorphic features at confluences. However, natural channels, particularly those of meandering rivers, curve and bend. This property and observation of channel curvature at natural junctions have led to the hypothesis that natural stream and river confluences tend to occur on the concave outer bank of meander bends. The resulting confluence planform, referred to as a confluent-meander bend, was observed over a century ago but has received little scientific attention. This paper examines preliminary data on three-dimensional flow structure and channel morphology at two natural confluent-meander bends of varying size and with differing tributary entrance locations. The large river confluence of the Vermilion River and Wabash River in west central Indiana and the comparatively small junction of the Little Wabash River and Big Muddy Creek in southeastern Illinois are the location of study sites for field investigation. Measurements of time-averaged three-dimensional velocity components were obtained at these confluences with an acoustic Doppler current profiler for flow events with differing momentum ratios. Bed and channel morphology were also surveyed with a digital fathometer to document geomorphic change. Preliminary analysis of the velocity data reveals the presence of a well-defined shear layer between the converging flows and secondary circulation in the main channel. The tributary channel appears to oppose high velocity flow directed toward the outer bank by centrifugal acceleration through the meander bend of the main channel, thereby diminishing erosion along the cut bank and possibly stabilizing the meander bend channel. The flow structure and channel morphology of the study sites are compared to consider the effect of spatial scale and geometric characteristics on confluent-meander bend dynamics.

A Guide to Ordinary High Water Mark (OHWM) Delineation for Non-Perennial Streams in the Western Mountains, Valleys, and Coast Region of the United States

DTIC Science & Technology

2014-08-01

in vegetation characteristics. This guide addresses the underlying hydrologic and geomorphic concepts per- taining to the OHWM and the field...temporally varying hydrologic and geomorphic processes .............................. 12 4 The distribution of rankings for each of the three primary...define, amend, or replace any existing regulations, laws , or legal guidance related to the OHWM or to the regulation of WoUS. Furthermore, determining

Role of river flow and sediment mobilization in riparian alder establishment along a bedrock-gravel river, South Fork Eel River, California

NASA Astrophysics Data System (ADS)

Jablkowski, P.; Johnson, E. A.; Martin, Y. E.

2017-10-01

Climatic, hydraulics, hydrologic, and fluvial geomorphic processes are the main drivers of riparian white alder (Alnus rhombifolia Nutt.) distribution in northern California. The Mediterranean climate and canyon bound, bedrock-gravel morphology of the South Fork Eel have a distinct effect on these processes. White alder seeds are preferentially deposited on river bars where river hydraulics create eddies coinciding with the downstream part of riffles and the upstream part of pools. Seeds are generally deposited below bankfull elevations by the descending hydrograph during the spring season in this Mediterranean climate. For successful germination and establishment, the seeds must be deposited at a location such that they are not remobilized by late spring flows. The summer establishment period is defined from the date of seed deposition and germination to the fall/winter date of river sediment mobilization. Seedling root growth rate decreases exponentially with decreasing water potential. However, seedlings are shown not to be generally limited by water availability at the elevations they are most commonly deposited. The establishment of white alder seedlings following the first summer will therefore depend on their ability to resist fall/winter high flows. The method proposed here compares the predicted rooting depth to predicted sediment scour rates. The length of the establishment period rather than water availability determines final seedling rooting depth. Over the past 40 years, very few years had establishment periods that were long enough or had fast enough alder growth rates to survive winter floods that often scour deeper than the total root length. The low survival of seedlings in the first autumn season following germination is believed to be a principal reason for the missing age classes often found in alder distributions along rivers.

A probabilistic approach to quantifying spatial patterns of flow regimes and network-scale connectivity

NASA Astrophysics Data System (ADS)

Garbin, Silvia; Alessi Celegon, Elisa; Fanton, Pietro; Botter, Gianluca

2017-04-01

The temporal variability of river flow regime is a key feature structuring and controlling fluvial ecological communities and ecosystem processes. In particular, streamflow variability induced by climate/landscape heterogeneities or other anthropogenic factors significantly affects the connectivity between streams with notable implication for river fragmentation. Hydrologic connectivity is a fundamental property that guarantees species persistence and ecosystem integrity in riverine systems. In riverine landscapes, most ecological transitions are flow-dependent and the structure of flow regimes may affect ecological functions of endemic biota (i.e., fish spawning or grazing of invertebrate species). Therefore, minimum flow thresholds must be guaranteed to support specific ecosystem services, like fish migration, aquatic biodiversity and habitat suitability. In this contribution, we present a probabilistic approach aiming at a spatially-explicit, quantitative assessment of hydrologic connectivity at the network-scale as derived from river flow variability. Dynamics of daily streamflows are estimated based on catchment-scale climatic and morphological features, integrating a stochastic, physically based approach that accounts for the stochasticity of rainfall with a water balance model and a geomorphic recession flow model. The non-exceedance probability of ecologically meaningful flow thresholds is used to evaluate the fragmentation of individual stream reaches, and the ensuing network-scale connectivity metrics. A multi-dimensional Poisson Process for the stochastic generation of rainfall is used to evaluate the impact of climate signature on reach-scale and catchment-scale connectivity. The analysis shows that streamflow patterns and network-scale connectivity are influenced by the topology of the river network and the spatial variability of climatic properties (rainfall, evapotranspiration). The framework offers a robust basis for the prediction of the impact of land-use/land-cover changes and river regulation on network-scale connectivity.

A comparison of avian communities and habitat characteristics in floodplain forests associated with valley plugs and unchannelized streams

USGS Publications Warehouse

Pierce, Aaron R.; King, Sammy L.

2011-01-01

Channelization of streams associated with floodplain forested wetlands has occurred extensively throughout the world and specifically in the southeastern United States. Channelization of fluvial systems alters the hydrologic and sedimentation processes that sustain these systems. In western Tennessee, channelization and past land-use practices have caused drastic geomorphic and hydrologic changes, resulting in altered habitat conditions that may affect avian communities. The objective of this study was to determine if there were differences in avian communities utilizing floodplain forests along unchannelized streams compared to channelized streams with valley plugs, areas where sediment has completely filled the channel. During point count surveys, 58 bird species were observed at unchannelized sites and 60 species were observed at valley plug sites. Species associated with baldcypress-tupelo (Taxodium-Nyssa) swamps (e.g. Great Egret (Ardea albus) and Black-crowned Night Heron (Nycticorax nycticorax)) and mature hardwood forests with open midstories (e.g. Eastern Wood-Pewee (Contopus virens), Yellow-throated Vireo (Vireo flavifrons), Cerulean Warbler (Dendroica cerulea) and Scarlet Tanager (Piranga olivacea)) were either only found at unchannelized sites or were more abundant at unchannelized sites. Conversely, species associated with open and early successional habitats (e.g. Tree Swallow (Tachycineta bicolor), Northern Mockingbird (Mimus polyglottos) and Blue Grosbeak (Passerina caerulea)) were either only found at valley plug sites or were more abundant at valley plug sites. Results of habitat modelling suggest that the habitat characteristics of floodplain forests at unchannelized sites are more suitable for Neotropical migrant bird species of conservation concern in the region than at valley plug sites. This study, in combination with previous research, demonstrates the ecological impacts of valley plugs span across abiotic and biotic processes and tropic levels.

Anthropocene landscape change and the legacy of nineteenth- and twentieth-century mining in the Fourmile Catchment, Colorado Front Range

USGS Publications Warehouse

Dethier, David P.; Ouimet, William B.; Murphy, Sheila F.; Kotikian, Maneh; Wicherski, Will; Samuels, Rachel M.

2018-01-01

Human impacts on earth surface processes and materials are fundamental to understanding the proposed Anthropocene epoch. This study examines the magnitude, distribution, and long-term context of nineteenth- and twentieth-century mining in the Fourmile Creek catchment, Colorado, coupling airborne LiDAR topographic analysis with historical documents and field studies of river banks exposed by 2013 flooding. Mining impacts represent the dominant Anthropocene landscape change for this basin. Mining activity, particularly placer operations, controls floodplain stratigraphy and waste rock piles related to mining cover >5% of hillslopes in the catchment. Total rates of surface disturbance on slopes from mining activities (prospecting, mining, and road building) exceed pre-nineteenth-century rates by at least fifty times. Recent flooding and the overprint of human impacts obscure the record of Holocene floodplain evolution. Stratigraphic relations indicate that the Fourmile valley floor was as much as two meters higher in the past 2,000 years and that placer reworking, lateral erosion, or minor downcutting dominated from the late Holocene to present. Concentrations of As and Au in the fine fraction of hillslope soil, mining-related deposits, and fluvial deposits serve as a geochemical marker of mining activity in the catchment; reducing As and Au values in floodplain sediment will take hundreds of years to millennia. Overall, the Fourmile Creek catchment provides a valuable example of Anthropocene landscape change for mountainous regions of the Western United States, where hillslope and floodplain markers of human activity vary, high rates of geomorphic processes affect mixing and preservation of marker deposits, and long-term impact varies by landscape location.

Transfer of fallout radionuclides derived from Fukushima NPP accident: 1 year study on transfer of radionuclides through geomorphic processes

NASA Astrophysics Data System (ADS)

Onda, Y.; Kato, H.; Fukushima, T.; Wakahara, T.; Kita, K.; Takahashi, Y.; Sakaguchi, A.; Tanaka, K.; Yamashiki, Y.; Yoshida, N.

2012-12-01

After the Fukushima Daiichi Nuclear Power Plant acciden, fallout radionuclides on the ground surface will transfer through geomorphic processes. Therefore, in order to estimate future changes in radionuclide deposition, migration process of radionuclides in forests, soils, ground water, rivers, and entrainment from trees and soils should be confirmed. We (FMWSE group) was funded by MEXT, Japanese government, and 1 year following monitoring has been conducted about 1 year. 1 Migration study of radionuclides in natural environment including forests and rivers 1) Study on depth distribution of radiocaesium in soils within forests, fields, and grassland. 2) Confirmation of radionuclide distribution and investigation on migration in forests. 3) Study on radionuclide migration due to soil erosion under different land use. 4) Measurement of radionuclides entrained from natural environment including forests and soils. 2 Migration study of radionuclides through hydrological cycle such as soil water, rivers, lakes and ponds, ground water. 1) Investigation on radionuclide migration through soil water, ground water, stream water, spring water under different land use. 2) Study on paddy-to-river transfer of radionuclides through suspended sediment. 3) Study on river-to-ocean transfer of radionuclides via suspended sediment. 4) Confirmation of radionuclide deposition in ponds and reservoirs. We will present how and where the fallout radionulides transfter through geomorphic processes.

Non-equilibrium freezing of water-ice in sandy basaltic regoliths and implications for fluidized debris flows on Mars

NASA Technical Reports Server (NTRS)

Gooding, J. L.

1987-01-01

Many geomorphic features on Mars were attributed to Earth-analogous, cold-climate processes involving movement of water or ice lubricated debris. Clearly, knowledge of the behavior of water in regolith materials under Martian conditions is essential to understanding the postulated geomorphic processes. Experiments were performed with sand-sized samples of natural basaltic regoliths in order to further elucidate how water/regolith interactions depend upon grain size and mineralogy. The data reveal important contrasts with data for clay-mineral substrates and suggest that the microphysics of water/mineral interactions might affect Martian geomorphic processes in ways that are not fully appreciated. Sand and silt sized fractions of two soils from the summit of Mauna Kea were used as Mars-analogous regolith materials. Temperatures were measured for water/ice phase transitions as wet slurries of individual soil fractions which were cooled or heated at controlled rates under a carbon dioxide atmosphere. Freezing and melting of ice was studied as a function of water/soil mass ratio, soil particle size, and thermal-cycle rate. Comparison tests were done under the same conditions with U.S. Geological Survey standard rock powders.

Assessing processes and timescales of sandstone 'peak forest' formation at Wulingyuan (Hunan, China)

NASA Astrophysics Data System (ADS)

Fink, David; May, Henne; Huang, He-quing; Fujioka, Toshiyuki; Wray, Robert

2013-04-01

Sandstone landscapes around the globe exhibit a surprising variety in terms of their landforms and formative processes. Ultimately, this reflects the wide range of geomorphic controls that dominate on regional scales, such as lithology, physical and chemical weathering, tectonics, and climate . At Wulingyuan, Hunan Province, China, a unique landscape has developed in Devonian sandstone over an area of ~400 km2, the "Wulingyuan peak forest", which is characterized by sheer vertical sandstone pillars over 3000 m in relief, overlayed with a substructure of peaks and walls of up to 350 m height. Due to these spectacular features, the area has become a major tourist attraction, and has recently been declared an UNESCO Global Geopark. Uplift, a densely spaced joint pattern, and the uniformity of sandstone beds have been suggested as major prerequisites for the formation and preservation of the unique morphology around Wulingyuan. We aim to investigate the underlying processes and controls responsible for the "peak forest" by determining a chronological framework for its age, rate of formation and rates of surface erosion. The initiation of uplift ~ 1 Ma ago and subsequent stepwise evolution of the "peak forest" has been inferred from cave sediments and surrounding alluvial terraces. No direct information, however, is available on the shorter-term evolution of the vertical sandstone walls, peaks and pillars. In this study , we (i) consider sampling strategies for applying surface exposure dating (SED) in this challenging morphological setting. (ii) present some first results, and (iii) discuss their significance in providing first estimates on rates of catchment-wide denudation, weathering, retreat of the vertical sandstone walls, and bedrock incision. In combination with a GIS-based assessment of sediment volumes stored in and eroded from the catchment, our data will help to elucidate the relative roles of fluvial, mass-wasting, and weathering processes in the longer-term, late Quaternary formation of the "peak forest".

Effects of simultaneous climate change and geomorphic evolution on thermal characteristics of a shallow Alaskan lake

USGS Publications Warehouse

Griffiths, Jennifer R.; Schindler, Daniel E.; Balistrieri, Laurie S.; Ruggerone, Gregory T.

2011-01-01

We used a hydrodynamics model to assess the consequences of climate warming and contemporary geomorphic evolution for thermal conditions in a large, shallow Alaskan lake. We evaluated the effects of both known climate and landscape change, including rapid outlet erosion and migration of the principal inlet stream, over the past 50 yr as well as future scenarios of geomorphic restoration. Compared to effects of air temperature during the past 50 yr, lake thermal properties showed little sensitivity to substantial (~60%) loss of lake volume, as the lake maximum depth declined from 6 m to 4 m driven by outlet erosion. The direction and magnitude of future lake thermal responses will be driven largely by the extent of inlet stream migration when it occurs simultaneously with outlet erosion. Maintaining connectivity with inlet streams had substantial effects on buffering lake thermal responses to warming climate. Failing to account for changing rates and types of geomorphic processes under continuing climate change may misidentify the primary drivers of lake thermal responses and reduce our ability to understand the consequences for aquatic organisms.

Mountain rivers may need centuries to adjust to earthquake-triggered sediment pulses, Pokhara, Nepal

NASA Astrophysics Data System (ADS)

Stolle, Amelie; Korup, Oliver; Schwanghart, Wolfgang; Bernhardt, Anne; Adhikari, Basanta Raj; Andermann, Christoff; Wittmann, Hella; Merchel, Silke

2017-04-01

Mountain rivers respond to strong earthquakes by not only adjusting to changes in local base level, but also by rapidly aggrading to accommodate excess sediment delivered by co- and post-seismic landslides. A growing number of detailed sediment budgets suggests that it takes rivers several years to decades to recover from such seismic disturbances, depending on how recovery is defined. We test this notion and study how rivers adjusted to catastrophic sedimentation triggered by at least three medieval earthquakes in the central Nepal Himalaya. In the vicinity of Pokhara, the nation's second largest city, rapid aggradation formed a large fan covering 150 km2 of mountainous terrain over a length of some 70 km. The fan prograded into several tributary valleys, rapidly infilling their lower reaches with several tens of meters of sediment from a major point source tens of kilometers away. A robust radiocarbon chronology of these valley fills provides an ideal framework for gauging average rates of fluvial incision and adjustment. We use high-resolution digital elevation data, geodetic field surveys, aerial photos documenting historic channel changes, and several re-exhumed tree trunks in growth position to define dated geomorphic marker surfaces. We compare various methods of computing the volumes lost from these surfaces to arrive at net sediment yields averaged over decades to centuries. We find that contemporary rates of river incision into the medieval earthquake debris are between 160 and 220 mm yr-1, with corresponding sediment yields of 103 to 105 t km-2 yr-1, several hundred years after the last traceable seismic disturbance. These rates greatly exceed the density-adjusted background rates of catchment-wide denudation inferred from concentrations of cosmogenic 10Be in river sands sampled in different tributaries. The lithological composition of active channel-bed load differs largely from local bedrock and confirms that rivers are still busy with excavating medieval valley fills. Pronounced knickpoints and epigenetic gorges at tributary junctions add to the picture of a drawn-out fluvial response, while the re-exhumed tree trunks indicate that some distal portions of the earthquake-derived sediment wedge have been incised to near their base. Our results challenge the notion that mountain rivers recover within years or even decades following earthquake disturbance. We caution against generalizing the spectrum of fluvial response in this context, as the valley fills around Pokhara document the possibility of a more protracted fluvial response that may have been ongoing for as long as 900 years despite the high and aggressive erosion that characterizes Himalayan rivers. Beyond the scientific community, our results may motivate some rethinking of post-seismic hazard appraisals and infrastructural planning during the rehabilitation phase in earthquake-struck regions.

Spreading Geodiversity awareness in schools through field trips and ICT

NASA Astrophysics Data System (ADS)

Magagna, Alessandra; Giardino, Marco; Ferrero, Elena

2014-05-01

Geodiversity, unlike Biodiversity, is not a topic included in the Italian schools curriculum. Nevertheless, Geomorphology is taught at all levels, and it seems to be the right tool for introducing the students to the concepts related to Geodiversity. In this context, a research on the use of field trips and Information and Communication Technologies (ICT) is being carried out for spreading the value of Geodiversity in Secondary Schools. Relevant international literature states that field trips are effective didactic tools for Earth Science education, because they stimulate an active learning process and allow students to appreciate the geological complexity of an area. On the other side, ICT allow students to get knowledge about the variety of landforms of their own territory by staying indoor, using virtual field trips and free software like Google Earth, Google Maps, Bing etc. In order to connect the two strategies, an innovative educational project is proposed here; it involves both the indoor and the outdoor activities, by enhancing a critical approach to the complexity of geological processes. As a starting point, a multimedia product on 20 Italian geological tours, designed for analyzing Geodiversity at a regional scale, has been tested with teachers and students, in order to understand its effectiveness by using it solely indoor. In a second phase, teachers and students have been proposed to compare and integrate indoor and outdoor activities to approach Geodiversity directly at a local scale, by means of targeted field trips. For achieving this goal, during the field trips, students used their mobile devices (smartphone and tablet) equipped with free and/or open source applications (Epicollect, Trimble Outdoor Navigator). These tools allow to track field trips, to gather data (geomorphological observations and related photographs), and to elaborate them in the laboratory; a process useful for reasoning on concepts such as spatial and temporal scales and for comparing the real and the virtual experience. Particularly, the geological history of an Alpine Piedmont area West of Torino (NW Italy) has been investigated. A one-day educational field trip has been performed starting from the man-made features of the Sangano town, walking on the present-day, historical and pre-historical fluvial landforms of the Sangone River, and finally climbing up the Pleistocene glacial landforms of the Rivoli-Avigliana Morainic Amphitheatre. The track offers samples of the Geodiversity of the area by showing a variety of landforms and including panoramic views to the Alpine chain. Students collected geomorphological data and carried out research-type activities, such as mapping and describing landforms, making hypotheses on geomorphic processes and gathering useful elements for the reconstruction of the geological history of the area. By taking awareness of the spatial and temporal scales related to landforms and geomorphic processes, as well as to the Man-Nature interactions, students realize the "dynamic dimension" of Geodiversity. As a consequence, students can perceive the geomorphological landscape as a changeable system over time, and therefore worthy of protection.

Sediment depositions upstream of open check dams: new elements from small scale models

NASA Astrophysics Data System (ADS)

Piton, Guillaume; Le Guern, Jules; Carbonari, Costanza; Recking, Alain

2015-04-01

Torrent hazard mitigation remains a big issue in mountainous regions. In steep slope streams and especially in their fan part, torrential floods mainly result from abrupt and massive sediment deposits. To curtail such phenomenon, soil conservation measures as well as torrent control works have been undertaken for decades. Since the 1950s, open check dams complete other structural and non-structural measures in watershed scale mitigation plans1. They are often built to trap sediments near the fan apexes. The development of earthmoving machinery after the WWII facilitated the dredging operations of open check dams. Hundreds of these structures have thus been built for 60 years. Their design evolved with the improving comprehension of torrential hydraulics and sediment transport; however this kind of structure has a general tendency to trap most of the sediments supplied by the headwaters. Secondary effects as channel incision downstream of the traps often followed an open check dam creation. This sediment starvation trend tends to propagate to the main valley rivers and to disrupt past geomorphic equilibriums. Taking it into account and to diminish useless dredging operation, a better selectivity of sediment trapping must be sought in open check dams, i.e. optimal open check dams would trap sediments during dangerous floods and flush them during normal small floods. An accurate description of the hydraulic and deposition processes that occur in sediment traps is needed to optimize existing structures and to design best-adjusted new structures. A literature review2 showed that if design criteria exist for the structure itself, little information is available on the dynamic of the sediment depositions upstream of open check dams, i.e. what are the geomorphic patterns that occur during the deposition?, what are the relevant friction laws and sediment transport formula that better describe massive depositions in sediment traps?, what are the range of Froude and Shields numbers that the flows tend to adopt? New small scale model experiments have been undertaken focusing on depositions processes and their related hydraulics. Accurate photogrammetric measurements allowed us to better describe the deposition processes3. Large Scale Particle Image Velocimetry (LS-PIV) was performed to determine surface velocity fields in highly active channels with low grain submersion4. We will present preliminary results of our experiments showing the new elements we observed in massive deposit dynamics. REFERENCES 1.Armanini, A., Dellagiacoma, F. & Ferrari, L. From the check dam to the development of functional check dams. Fluvial Hydraulics of Mountain Regions 37, 331-344 (1991). 2.Piton, G. & Recking, A. Design of sediment traps with open check dams: a review, part I: hydraulic and deposition processes. (Accepted by the) Journal of Hydraulic Engineering 1-23 (2015). 3.Le Guern, J. Ms Thesis: Modélisation physique des plages de depot : analyse de la dynamique de remplissage.(2014) . 4.Carbonari, C. Ms Thesis: Small scale experiments of deposition processes occuring in sediment traps, LS-PIV measurments and geomorphological descriptions. (in preparation).

Finding the lost arches of the Medieval Avignon's Bridge (Avignon, Provence, South France): a geoarchaeological approach

NASA Astrophysics Data System (ADS)

Ghilardi, M.; Vella, M. A.; Hermitte, D.; Parisot, J. C.; Dussouillez, P.; Fleury, T. J.; Provansal, M.; Delanghe-Sabatier, D.; Demory, F.; Mathé, P. E.; Quesnel, Y.; Danos, S.; Balossino, S.; Delpey, Y.; Hartmann-Virnich, A.; Berthelot, M.

2012-04-01

This papers aims to precisely locate the medieval arches of the so called Avignon's (Saint Bénézet) Bridge (South France) and to reconstruct the fluvial dynamics of the Rhone River from Early Medieval Times to the 19th century. Until now, just four remnant arches are still visible (near Avignon) and it is estimated that 22 arches (which represents a total length of approximately 920 meters) were built to span over one of the largest French Rivers. The late roman and early mediaeval dates of several foundation poles extracted from the river bed might suggest the existence of an earlier bridge, though it remains uncertain if any of such an earlier structure was still visible when the first mediaeval bridge was built. The mediaeval bridge was erected from 1177 until 1185 (in less than 10 years), but modified a few decades later when stone arches were erected, thus raising the road level substantially. The structure of the bridge being vulnerable, seasonal floods proved a neverending threat and cause of damage which was frequently repaired with masonry or wood. Final abandon of the edifice could be placed in the late 1660s - Early 1670s according to historical sources. Questions arose about the location of the "lost arches" and evident flood events dated back to the Little Ice Age (e.g. 1500 to 1850) could be responsible of the partial destruction of the bridge. Few archaeological, architectural, historical and palaeoenvironmental works have been undertaken in order to determine the precise shape of the Saint Bénézet Bridge at certain stages of its history. Since 2010, a joint team composed by laboratories affiliated to the French Public Research Centre (CNRS) and to Universities of Avignon and of Aix-Marseille 1 is trying to link the different phases of constructions/destructions of the monument with the fluvial dynamics of the Rhone River for the concerned period (ANR PAVAGE). The geoarchaeological approach adopted comprises bathymetric surveys (SONAR and Acoustic camera techniques) together with geophysical prospections (Electric Resistivity Tomography and Magnetic Cartography methods) in order to reveal potential locations of arches within the modern Rhone River channels (Villeneuve Lez Avignon and Avignon's arms) and on the Barthelasse fluvial island. In addition historical sources, such as maps, were integrated together with the acquired geophysical data in a Geographic Information System in order to identify possible remnant arches. Finally, boreholes have been drilled and later linked with the geophysical data, to reveal the alluvial litho-stratigraphy and describe the geomorphic the changes in the fluvial system. Results clearly reveal the presence of large carved stone accumulation at a regular interval in the Villeneuve-Lez-Avignon and Avignon's branches. An interpretation concerning the shape of the Saint Bénézet Bridge, in a changing morpho-dynamic context, can be assumed and fits well with various sketches and maps established from the 16th to the 17th Centuries. Keywords: Rhone River, Saint Bénézet Medieval Bridge, city of Avignon, Geoarchaeology, Fluvial palaeoenvironments, bathymetric surveys, geophysics, coring, building techniques, building archaeology, iconography

Topographic Structure from Motion

NASA Astrophysics Data System (ADS)

Fonstad, M. A.; Dietrich, J. T.; Courville, B. C.; Jensen, J.; Carbonneau, P.

2011-12-01

The production of high-resolution topographic datasets is of increasing concern and application throughout the geomorphic sciences, and river science is no exception. Consequently, a wide range of topographic measurement methods have evolved. Despite the range of available methods, the production of high resolution, high quality digital elevation models (DEMs) generally requires a significant investment in personnel time, hardware and/or software. However, image-based methods such as digital photogrammetry have steadily been decreasing in costs. Initially developed for the purpose of rapid, inexpensive and easy three dimensional surveys of buildings or small objects, the "structure from motion" photogrammetric approach (SfM) is a purely image based method which could deliver a step-change if transferred to river remote sensing, and requires very little training and is extremely inexpensive. Using the online SfM program Microsoft Photosynth, we have created high-resolution digital elevation models (DEM) of rivers from ordinary photographs produced from a multi-step workflow that takes advantage of free and open source software. This process reconstructs real world scenes from SfM algorithms based on the derived positions of the photographs in three-dimensional space. One of the products of the SfM process is a three-dimensional point cloud of features present in the input photographs. This point cloud can be georeferenced from a small number of ground control points collected via GPS in the field. The georeferenced point cloud can then be used to create a variety of digital elevation model products. Among several study sites, we examine the applicability of SfM in the Pedernales River in Texas (USA), where several hundred images taken from a hand-held helikite are used to produce DEMs of the fluvial topographic environment. This test shows that SfM and low-altitude platforms can produce point clouds with point densities considerably better than airborne LiDAR, with horizontal and vertical precision in the centimeter range, and with very low capital and labor costs and low expertise levels. Advanced structure from motion software (such as Bundler and OpenSynther) are currently under development and should increase the density of topographic points rivaling those of terrestrial laser scanning when using images shot from low altitude platforms such as helikites, poles, remote-controlled aircraft and rotocraft, and low-flying manned aircraft. Clearly, the development of this set of inexpensive and low-required-expertise tools has the potential to fundamentally shift the production of digital fluvial topography from a capital-intensive enterprise of a low number of researchers to a low-cost exercise of many river researchers.

Persistence of Salmonid Redds

NASA Astrophysics Data System (ADS)

Buffington, J. M.; Buxton, T.; Fremier, A. K.; Hassan, M. A.; Yager, E.

2013-12-01

The construction of redds by spawning salmonids modifies fluvial processes in ways that are beneficial to egg and embryo survival. Redd topography induces hyporheic flow that oxygenates embryos incubating within the streambed and creates form drag that reduces bed mobility and scour of salmonid eggs. Winnowing of fine material during redd construction also coarsens the streambed, increasing bed porosity and hyporheic flow and reducing bed mobility. In addition to the biological benefits, redds may influence channel morphology by altering channel hydraulics and bed load transport rates depending on the size and extent of redds relative to the size of the channel. A key question is how long do the physical and biological effects of redds last? Field observations indicate that in some basins redds are ephemeral, with redd topography rapidly erased by subsequent floods, while in other basins, redds can persist for years. We hypothesize that redd persistence is a function of basin hydrology, sediment supply, and characteristics of the spawning fish. Hydrology controls the frequency and magnitude of bed mobilizing flows following spawning, while bed load supply (volume and caliber) controls the degree of textural fining and consequent bed mobility after spawning, as well as the potential for burial of redd features. The effectiveness of flows in terms of their magnitude and duration depend on hydroclimate (i.e., snowmelt, rainfall, or transitional hydrographs), while bed load supply depends on basin geology, land use, and natural disturbance regimes (e.g., wildfire). Location within the stream network may also influence redd persistence. In particular, lakes effectively trap sediment and regulate downstream flow, which may promote long-lived redds in stream reaches below lakes. These geomorphic controls are modulated by biological factors: fish species (size of fish controls size of redds and magnitude of streambed coarsening); life history (timing of spawning and incubation relative to high flows); and population size (density of redds and extent of streambed alteration within a given reach). Species and life history also control the location of spawning within the basin, dictating the flow and sediment supply regimes. A theoretical framework is developed for predicting redd persistence as a function of the above physical and biological factors. We expect that long-lived redds will indicate either that the river is not competent to re-work the effects of spawning or that spawning occurs after peak flow events that are capable of modifying redd features. The longevity of redds and their associated effects on fluvial processes also provides a measure of the degree of potential ecological conditioning for future generations of fish. Future work will test the framework in field and laboratory settings.

Late Pleistocene dune-sourced alluvial fans in coastal settings: Sedimentary facies and related processes (Mallorca, Western Mediterranean)

NASA Astrophysics Data System (ADS)

Pomar, F.; del Valle, L.; Fornós, J. J.; Gómez-Pujol, L.

2018-05-01

Aeolian-alluvial sedimentary interaction results in the formation of deposits characterized by typical alluvial sedimentary structures, but is composed of conspicuous amounts of aeolian sediments. The literature on this topic is limited and most works relate more with continental aeolian dunes or fluvial dune interference with fan bodies. Furthermore, there is a lack of examples of aeolian-alluvial sedimentary interference in coastal settings. In the western Mediterranean, there are many Pleistocene alluvial fan deposits built up partly by sediment originating from coastal dunes dismantled by alluvial streams. Very often, these deposits show a continuous sedimentary sequence through which we can derive the contribution and predominance of coastal, alluvial-colluvial and aeolian processes and their controls on landscape formation. This is an outstanding feature within coastal systems since it shows marine sediments reworked and integrated within coastal dune fields by aeolian transport, and the latter built up into alluvial fan bodies. In this sense, aeolian-alluvial interaction is the geomorphic-sedimentary expression of the coexistence and overlapping of alluvial and aeolian environments resulting in deposits sharing sedimentary features from both environments. The aim of this paper is to unravel the contribution of coastal dunes in the construction of alluvial fans bodies and identify the main sedimentary facies that constitute these deposits, as well as their climatic controls. For this reason, Es Caló fan (northern Mallorca) has been selected due to its well-exposed deposits exhibiting the alternation of aeolian, alluvial and colluvial deposits. Sedimentological and stratigraphic analyses based on 33 logs and complementary analyses demonstrate that most of the facies constituting the fan body are made up completely of marine bioclastic sands. These deposits record an alluvial fan sedimentary environment characterized by sediments inputs that do not proceed from non-alluvial/fluvial/colluvial systems. In fact they relate with a marine source. Chronologies on aeolianites of northern Mallorca indicate that up to four periods of aeolian deposition took place during cooling stages and marine regressions over the last 100 kyr. Moreover, the alternation of short warming-cooling fluctuations between the cooling stages may have provided the conditions necessary to generate stormy weather in the western Mediterranean, resulting in aeolian-alluvial interactions. Additionally, the dynamics of this sedimentary environment were only possible because during the Last Glacial Maximum, the sea level remained low enough to allow for the formation of coastal dune fields and fans.

Bend-scale geomorphic classification and assessment of the Lower Missouri River from Sioux City, Iowa, to the Mississippi River for application to pallid sturgeon management

USGS Publications Warehouse

Jacobson, Robert B.; Colvin, Michael E.; Bulliner, Edward A.; Pickard, Darcy; Elliott, Caroline M.

2018-06-07

Management actions intended to increase growth and survival of pallid sturgeon (Scaphirhynchus albus) age-0 larvae on the Lower Missouri River require a comprehensive understanding of the geomorphic habitat template of the river. The study described here had two objectives relating to where channel-reconfiguration projects should be located to optimize effectiveness. The first objective was to develop a bend-scale (that is, at the scale of individual bends, defined as “cross-over to cross-over”) geomorphic classification of the Lower Missouri River to help in the design of monitoring and evaluation of such projects. The second objective was to explore whether geomorphic variables could provide insight into varying capacities of bends to intercept drifting larvae. The bend-scale classification was based on geomorphic and engineering variables for 257 bends from Sioux City, Iowa, to the confluence with the Mississippi River near St. Louis, Missouri. We used k-means clustering to identify groupings of bends that shared the same characteristics. Separate 3-, 4-, and 6-cluster classifications were developed and mapped. The three classifications are nested in a hierarchical structure. We also explored capacities of bends to intercept larvae through evaluation of linear models that predicted persistent sand area or catch per unit effort (CPUE) of age-0 sturgeon as a function of the same geomorphic variables used in the classification. All highly ranked models that predict persistent sand area contained mean channel width and standard deviation of channel width as significant variables. Some top-ranked models also included contributions of channel sinuosity and density of navigation structures. The sand-area prediction models have r-squared values of 0.648–0.674. In contrast, the highest-ranking CPUE models have r-squared values of 0.011–0.170, indicating much more uncertainty for the biological response variable. Whereas the persistent sand model documents that physical processes of transport and accumulation are systematic and predictable, the poor performance of the CPUE models indicate that additional processes will need to be considered to predict biological transport and accumulation.

Tree ring-based chronology of hydro-geomorphic processes as a fundament for identification of hydro-meteorological triggers in the Hrubý Jeseník Mountains (Central Europe).

PubMed

Tichavský, Radek; Šilhán, Karel; Tolasz, Radim

2017-02-01

Hydro-geomorphic processes have significantly influenced the recent development of valley floors, river banks and depositional forms in mountain environments, have caused considerable damage to manmade developments and have disrupted forest management. Trees growing along streams are affected by the transported debris mass and provide valuable records of debris flow/flood histories in their tree-ring series. Dendrogeomorphic approaches are currently the most accurate methods for creating a chronology of the debris flow/flood events in forested catchments without any field-monitoring or a stream-gauging station. Comprehensive studies focusing on the detailed chronology of hydro-geomorphic events and analysis of meteorological triggers and weather circulation patterns are still lacking for the studied area. We provide a spatio-temporal reconstruction of hydro-geomorphic events in four catchments of the Hrubý Jeseník Mountains, Czech Republic, with an analysis of their triggering factors using meteorological data from four nearby rain gauges. Increment cores from 794 coniferous trees (Picea abies [L.] Karst.) allowed the identification of 40 hydro-geomorphic events during the period of 1889-2013. Most of the events can be explained by extreme daily rainfalls (≥50mm) occurring in at least one rain gauge. However, in several cases, there was no record of extreme precipitation at rain gauges during the debris flow/flood event year, suggesting extremely localised rainstorms at the mountain summits. We concluded that the localisation, intensity and duration of rainstorms; antecedent moisture conditions; and amount of available sediments all influenced the initiation, spatial distribution and characteristics of hydro-geomorphic events. The most frequent synoptic situations responsible for the extreme rainfalls (1946-2015) were related to the meridional atmospheric circulation pattern. Our results enhance current knowledge of the occurrences and triggers of debris flows/floods in the Central European mountains in transition between temperate oceanic and continental climatic conditions and may prompt further research of these phenomena in the Eastern Sudetes in general. Copyright © 2016 Elsevier B.V. All rights reserved.

Effects of river regulation on aeolian landscapes, Colorado River, southwestern USA

USGS Publications Warehouse

Draut, Amy E.

2012-01-01

Connectivity between fluvial and aeolian sedimentary systems plays an important role in the physical and biological environment of dryland regions. This study examines the coupling between fluvial sand deposits and aeolian dune fields in bedrock canyons of the arid to semiarid Colorado River corridor, southwestern USA. By quantifying significant differences between aeolian landscapes with and without modern fluvial sediment sources, this work demonstrates for the first time that the flow- and sediment-limiting effects of dam operations affect sedimentary processes and ecosystems in aeolian landscapes above the fluvial high water line. Dune fields decoupled from fluvial sand supply have more ground cover (biologic crust and vegetation) and less aeolian sand transport than do dune fields that remain coupled to modern fluvial sand supply. The proportion of active aeolian sand area also is substantially lower in a heavily regulated river reach (Marble–Grand Canyon, Arizona) than in a much less regulated reach with otherwise similar environmental conditions (Cataract Canyon, Utah). The interconnections shown here among river flow and sediment, aeolian sand transport, and biologic communities in aeolian dunes demonstrate a newly recognized means by which anthropogenic influence alters dryland environments. Because fluvial–aeolian coupling is common globally, it is likely that similar sediment-transport connectivity and interaction with upland ecosystems are important in other dryland regions to a greater degree than has been recognized previously.

Impact of 1985 hurricanes on Isles Dernieres, Louisiana: Temporal and spatial analysis of coastal geomorphic changes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Debusshere, K.; Westphal, K.; Penland, S.

1989-09-01

Catastrophic geomorphic changes occurred in the Isles Dernieres barrier island arc as a result of the direct impact of three hurricanes in 1985. The severity of the impact of hurricanes Danny, Elena, and Juan had not been equaled since the landfall of hurricanes Betsy and Camille in the late 1960s. The Isles Dernieres had not been subjected to a direct hurricane landfall since hurricane Bob in 1979. The recent hurricane impacts provided the USGS/LGS Louisiana Cooperative Barrier Island and Land Loss Study the opportunity to examine the process-response characteristics of this low-profile transgressive barrier island arc to multiple hurricane impactsmore » in a single hurricane season. The geomorphic changes along the Isles Dernieres were determined using four sequential airborne videotape surveys acquired in July 1984, July 1985 (pre-storm), August 1985 (post-Danny) and November 1985 (post-Juan) and mapped on 1:24,000 base maps produced from concurrent vertical aerial photography. A coastal geomorphic classification was developed to describe, quantify, and map the alongshore geomorphic, sedimentologic , and vegetative character of this barrier shoreline. The classification consists of three levels of descriptors: (1) primary morphology to define the predominant longshore morphology, (2) modifiers to depict the small-scale longshore features, and (3) variants to locate and quantify important coastal features, not mappable at the scale used.« less

Environment and Climate Changes during the Holocene: Inferred from Sedimentary Record/Proxies of a Paleodelta Region, Southwest Coast of India

NASA Astrophysics Data System (ADS)

Allu, N. C.; Prakash, V.; Gautam, P. K.; Bera, S. K.

2014-12-01

This work explains the sedimentation history and environment and climate changes during the Holocene along the southwest coast of India. The area is characterized by various landforms such as lagoons, barrier islands, beach ridges, paleostrandlines, alluvial plains, marshy lands and flood plains. Paleodelta, located at the mouth of the modern Periyar River is an important geomorphic marker. A borehole of 40 m depth was drilled in the paleodelta and sediment samples were recovered at different depth intervals. Paleoclimate and paleo-environment were inferred based on geochronology, textural and geotechnical parameters, clay minerals, and pollen analysis results. The bottom of the borehole represents an age of ~ 12 ka BP. Sediments exhibit coarsening texture upwards of the borehole, with fine mud and peat intercalations at the bottom. Six litho facies - muddy sand, sand, sandy mud, silty sand, sandy silt, and mud - were recorded. Geotechnical properties comprising moisture content, organic carbon, plasticity index record high values, whereas low bulk density associated with a low critical shear stress, are recorded. An increase in illite and to a lesser degree smectite with concomitant decrease in kaolinite is observed. Sediment texture represents a major change of depositional environment from marine to fluvial sedimentary facies during the major sea level fall i.e., after 7 ka B.P. The present sea level attained during 4-5 ka B.P; major rise of sea level has taken place from 7-11 ka BP and regression during 7 - 5 ka B.P. These transgression and regression phases introduced the changes in the environment of deposition. The monsoon was dynamic and more intense after the major fall of sea level causing the fluctuations in the fluvial facies. Upward coarsening of grain size in the borehole indicates change in sediment deposition due to increased hydrodynamic conditions and strong fluvial action, which can be linked to marine regression. Geotechnical properties suggest textural changes and sedimentary facies. An upward increase in smectite and kaolinite and decreasing illite supports major fall in sea level and also the aridity. Pollen record of sediment strata supports the paleo-environment dominated by the presence of semi-evergreen type of mangrove plants during mid- to early-Holocene times.

Fluvial responses to land-use changes and climatic variations within the Drury Creek watershed, southern Illinois

NASA Astrophysics Data System (ADS)

Miller, Suzanne Orbock; Ritter, Dale F.; Kochel, R. Craig; Miller, Jerry R.

1993-04-01

Fluvial responses to climatic variation and Anglo-American settlement were documented for the Drury Creek watershed, southern Illinois by examining stratigraphic, geomorphic, climatic, and historical data. Regional analyses of long-term precipitation records document a period of decreasing mean annual precipitation from 1904 to about 1945, and an increasing trend in annual precipitation from 1952 to the present. The period between 1945 and 1951 experienced a large number of intense storms that resulted in high annual precipitation totals. Statistical relationships illustrate that changes in precipitation totals are transferred to the hydrologic system as fluctuations in stream discharge. Historical records of southern Illinois show that a maximum period of settlement and deforestation occurred between the 1860s and 1920s. This era ended in the 1940s when large tracts of land were revegetated in an attempt to curtail erosion which had caused extensive upland degradation. In response to hillslope erosion at least two meters of fine-grained sediments were deposited on valley floors. Average sedimentation rates, determined using decdrochronologic techniques, are estimated to be 2.11 cm/yr for the period between 1890 and 1988; rates that are 1 to 2 orders of magnitude greater than pre-settlement values calculated for other areas of the midwest. However, botanical data suggest that aggradation was episodic, possibly occurring during three periods characterized by greater annual precipitation. Since the 1940s, sedimentation rates have declined. Reduced rates of sedimentation are related to an episode of channel entrenchment that reduced overbank flooding. Entrenchment coincided with a period of: (1) reduced sediment yields associated with watershed revegetation and the introduction of soil conservation practices, and (2) intense storm activity that resulted in long periods of high discharge. As a result of channel incision and hillslope erosion, newly exposed bedrock in upstream areas currently provides a source of gravel load to the channels. The distribution of coarse bedload material along tributary streams combined with downstream decreases in width:depth ratios and tractive force estimates suggest that channels in the Drury Creek watershed are slowly adjusting their configuration to transport coarse bedload material. The fluvial response to the increased influx of coarse sediment began more than 45 years ago and continues today.

Surficial geology and stratigraphy of Pleistocene Lake Manix, San Bernardino County, California

USGS Publications Warehouse

Reheis, Marith C.; Redwine, Joanna R.; Wan, Elmira; McGeehin, John P.; VanSistine, D. Paco

2014-01-01

Pluvial Lake Manix and its surrounding drainage basin, in the central Mojave Desert of California, has been a focus of paleoclimate, surficial processes, and neotectonic studies by the U.S. Geological Survey (USGS) since about 2004. The USGS initiated studies of Lake Manix deposits to improve understanding of the paleoclimatic record and the shifts in atmospheric circulation that controlled precipitation in the Mojave Desert. Until approximately 25,000 years ago, Lake Manix was the terminus of the Mojave River, which drains northeasterly from the San Bernardino Mountains; the river currently terminates in the Soda Lake and Silver Lake playas. Pleistocene Lake Manix occupied several subbasins at its maximum extent. This map focuses on the extensive exposures created by incision of the Mojave River and its tributaries into the interbedded lacustrine and alluvial deposits within the central (Cady) and northeastern (Afton) subbasins of Lake Manix, and extends from the head of Afton Canyon to Manix Wash. The map illuminates the geomorphic development and depositional history of the lake and alluvial fans within the active tectonic setting of the eastern California shear zone, especially interactions with the left-lateral Manix fault. Lake Manix left an extraordinarily detailed but complex record of numerous transgressive-regressive sequences separated by desiccation and deposition of fan, eolian, and fluvial deposits, and punctuated by tectonic movements and a catastrophic flood that reconfigured the lake basin. Through careful observation of the intercalated lacustrine and fan sequences and by determining the precise elevations of unit contacts, this record was decoded to understand the response of the lake and river system to the interplay of climatic, geomorphic, and tectonic forces. These deposits are exposed in steep badland topography. Mapping was carried out mostly at scales of 1:12,000, although the map is presented at 1:24,000 scale, and employs custom unit nomenclature, with multiple subdivided lacustrine and alluvial fan units. In addition, many important units are very thin and cannot be mapped separately, or are covered by thin eolian sand, so these are commonly portrayed as stacks of units or combined units. These details are more accurately portrayed in the measured sections that accompany the map. Altitudes of many contacts were obtained using differentially corrected Global Positioning System (GPS) or, in some cases, lidar (light detection and ranging) data.

The Northwestern Slope Valleys Region, Mars: A Prime Target for the Future Exploration of Mars

NASA Astrophysics Data System (ADS)

Dohm, J. M.; Ferris, J. C.; Anderson, R. C.; Baker, V. R.; Hare, T. M.; Mahaney, W. C.

2002-12-01

Mars is a water-enriched planet theorized to have had Earth-like conditions during its embryonic stages of evolution (Early into Middle Noachian or > 3.8 GA). The Earth-like conditions include: (1) plate tectonism, (2) an active hydrosphere resulting in higher erosion rates and the presence of layered sedimentary deposits, and (3) a potential biosphere. Due to its smaller size and lower gravity, its thermal energy rapidly declined, sending the planet into a permanent monoplate regime. The Tharsis superplume, Elysium superplume, and structural discontinuities in the lithosphere are sites of long-lived energy releases and hydrothermal activity. Furthermore, as its atmosphere thinned and cooled, and water was lost to hydrodynamic escape, the Earth-like hydrological cycle transitioned into a persisting cold desert climate, approximating the present-day climate of the Dry Valleys in Antarctica. Stratigraphic, hydrogeomorphic, and paleotectonic information indicate an active Mars (e.g., late-stage superplume activity) that experienced punctuated periods of magmatic-driven hydrologic activity long after the Earth-like hydrologic regime had ended. Existing geologic, geomorphic, geophysical, topographic, impact cratering, spectral, and elemental information collectively point to a prime target site for future exploration that has the potential to yield significant geologic, paleoclimatic, paleohydrologic, and exobiologic information. The Northwestern Slope Valleys (NSVs) region archives traits similar to terrestrial field sites where the processes associated with: (1) fluvial, eolian, and hydrothermal activity, (2) modification due to landslides and glaciers, and (3) the formation of diverse rock assemblages (e.g., provenances include Noachian Thaumasia highlands mountain range and Europe-sized sedimentary basin and Noachian-Amazonian basaltic and possibly silica-enriched volcanoes and lava flow fields) are recorded. The region is especially remarkable since it encapsulates at least three distinct paleohydrologic regimes: Noachian-Early Hesperian NSVs flooding (~108 - 1010 m3/sec), Late Hesperian-Early Amazonian Mangala Valles flooding (~107 m3/sec), Amazonian sapping channel formation (~103 m3/sec), and recent groundwater seeps (<102 m3/sec), all of which expose deposits for in-situ study and sample return. Terrestrial analogs include: (1) Wet Beaver Creek, Arizona, which reveals intriguing geologic, hydrogeologic, and geomorphic similarities to a well-developed martian sapping channel, Abus Vallis, and (2) the Gray Mountain FIDO rover test site, which records diverse geological terrains similar to what might be encountered at the proposed NSVs prime target site.

Volcanogenic Fluvial-Lacustrine Environments in Iceland and Their Utility for Identifying Past Habitability on Mars

PubMed Central

Cousins, Claire

2015-01-01

The search for once-habitable locations on Mars is increasingly focused on environments dominated by fluvial and lacustrine processes, such as those investigated by the Mars Science Laboratory Curiosity rover. The availability of liquid water coupled with the potential longevity of such systems renders these localities prime targets for the future exploration of Martian biosignatures. Fluvial-lacustrine environments associated with basaltic volcanism are highly relevant to Mars, but their terrestrial counterparts have been largely overlooked as a field analogue. Such environments are common in Iceland, where basaltic volcanism interacts with glacial ice and surface snow to produce large volumes of meltwater within an otherwise cold and dry environment. This meltwater can be stored to create subglacial, englacial, and proglacial lakes, or be released as catastrophic floods and proglacial fluvial systems. Sedimentary deposits produced by the resulting fluvial-lacustrine activity are extensive, with lithologies dominated by basaltic minerals, low-temperature alteration assemblages (e.g., smectite clays, calcite), and amorphous, poorly crystalline phases (basaltic glass, palagonite, nanophase iron oxides). This paper reviews examples of these environments, including their sedimentary deposits and microbiology, within the context of utilising these localities for future Mars analogue studies and instrument testing. PMID:25692905

Volcanogenic fluvial-lacustrine environments in iceland and their utility for identifying past habitability on Mars.

PubMed

Cousins, Claire

2015-02-16

The search for once-habitable locations on Mars is increasingly focused on environments dominated by fluvial and lacustrine processes, such as those investigated by the Mars Science Laboratory Curiosity rover. The availability of liquid water coupled with the potential longevity of such systems renders these localities prime targets for the future exploration of Martian biosignatures. Fluvial-lacustrine environments associated with basaltic volcanism are highly relevant to Mars, but their terrestrial counterparts have been largely overlooked as a field analogue. Such environments are common in Iceland, where basaltic volcanism interacts with glacial ice and surface snow to produce large volumes of meltwater within an otherwise cold and dry environment. This meltwater can be stored to create subglacial, englacial, and proglacial lakes, or be released as catastrophic floods and proglacial fluvial systems. Sedimentary deposits produced by the resulting fluvial-lacustrine activity are extensive, with lithologies dominated by basaltic minerals, low-temperature alteration assemblages (e.g., smectite clays, calcite), and amorphous, poorly crystalline phases (basaltic glass, palagonite, nanophase iron oxides). This paper reviews examples of these environments, including their sedimentary deposits and microbiology, within the context of utilising these localities for future Mars analogue studies and instrument testing.

Ecogeomorphic feedbacks in regrowth of travertine step-pool morphology after dam decommissioning, Fossil Creek, Arizona

NASA Astrophysics Data System (ADS)

Fuller, Brian M.; Sklar, Leonard S.; Compson, Zacchaeus G.; Adams, Kenneth J.; Marks, Jane C.; Wilcox, Andrew C.

2011-03-01

The linkages between fluvial geomorphology and aquatic ecosystems are commonly conceptualized as a one-way causal chain in which geomorphic processes create the physical template for ecological dynamics. In streams with a travertine step-pool morphology, however, biotic processes strongly influence the formation and growth of travertine dams, creating the potential for numerous feedbacks. Here we take advantage of the decommissioning of a hydroelectric project on Fossil Creek, Arizona, where restoration of CaCO 3-rich baseflow has triggered rapid regrowth of travertine dams, to explore the interactions between biotic and abiotic factors in travertine morphodynamics. We consider three conceptual frameworks, where biotic factors independently modulate the rate of physical and chemical processes that produce travertine dams; combine with abiotic factors in a set of feedback loops; and work in opposition to abiotic processes, such that the travertine step-pool morphology reflects a dynamic balance between dominantly-biotic constructive processes and dominantly-abiotic destructive processes. We consider separately three phases of an idealized life cycle of travertine dams: dam formation, growth, and destruction by erosive floods. Dam formation is catalyzed by abiotic factors (e.g. channel constrictions, and bedrock steps) and biotic factors (e.g. woody debris, and emergent vegetation). From measurements of changes over time in travertine thickness on a bedrock step, we find evidence for a positive feedback between flow hydraulics and travertine accrual. Measurements of organic content in travertine samples from this step show that algal growth contributes substantially to travertine accumulation and suggest that growth is most rapid during seasonal algal blooms. To document vertical growth of travertine dams, we embedded 252 magnets into nascent travertine dams, along a 10 km stretch of river. Growth rates are calculated from changes over time in the magnetic field intensity at the dam surface. At each magnet we record a range of hydraulic and travertine composition variables to characterize the dominant mechanism of growth: abiotic precipitation, algal growth, trapping of organic material, or in situ plant growth. We find: (1) rapid growth of travertine dams following flow restoration, averaging more than 2 cm/year; (2) growth rates decline downstream, consistent with loss of dissolved constituents because of upstream travertine deposition, but also parallel to a decline in organic content in dam surface material and a downstream shift in dominant biotic mechanism; (3) biotic mechanisms are associated with faster growth rates; and (4) correlations between hydraulic attributes and growth rates are more consistent with biotic than abiotic controls. We conclude that the strong influence of living organisms on rates of travertine growth, coupled with the beneficial effects of travertine on ecosystem dynamics, demonstrate a positive feedback between biology and geomorphology. During our two-year study period, erosive flood flows occurred causing widespread removal of travertine. The temporal distribution of travertine growth and erosion over the study period is consistent with a bimodal magnitude-frequency relation in which growth dominates except when large, infrequent storms occur. This model may be useful in other systems where biology exerts strong controls on geomorphic processes.

Feedbacks in Human-Landscape Systems

NASA Astrophysics Data System (ADS)

Chin, Anne; Florsheim, Joan L.; Wohl, Ellen; Collins, Brian D.

2014-01-01

This article identifies key questions and challenges for geomorphologists in investigating coupled feedbacks in human-landscape systems. While feedbacks occur in the absence of human influences, they are also altered by human activity. Feedbacks are a key element to understanding human-influenced geomorphic systems in ways that extend our traditional approach of considering humans as unidirectional drivers of change. Feedbacks have been increasingly identified in Earth-environmental systems, with studies of coupled human-natural systems emphasizing ecological phenomena in producing emerging concepts for social-ecological systems. Enormous gaps or uncertainties in knowledge remain with respect to understanding impact-feedback loops within geomorphic systems with significant human alterations, where the impacted geomorphic systems in turn affect humans. Geomorphology should play an important role in public policy by identifying the many diffuse and subtle feedbacks of both local- and global-scale processes. This role is urgent, while time may still be available to mitigate the impacts that limit the sustainability of human societies. Challenges for geomorphology include identification of the often weak feedbacks that occur over varied time and space scales ranging from geologic time to single isolated events and very short time periods, the lack of available data linking impact with response, the identification of multiple thresholds that trigger feedback mechanisms, the varied tools and metrics needed to represent both physical and human processes, and the need to collaborate with social scientists with expertise in the human causes of geomorphic change, as well as the human responses to such change.

Controls on morphological variability and role of stream power distribution pattern, Yamuna River, western India

NASA Astrophysics Data System (ADS)

Bawa, Nupur; Jain, Vikrant; Shekhar, Shashank; Kumar, Niraj; Jyani, Vikas

2014-12-01

Understanding the controls on the morphological variability of river systems constitutes one of the fundamental questions in geomorphic investigation. Channel morphology is an important indicator of river processes and is of significance for mapping the hydrology-ecologic connectivity in a river system and for predicting the future trajectory of river health in response to external forcings. This paper documents the spatial morphological variability and its natural and anthropogenic controls for the Yamuna River, a major tributary of the Ganga River, India. The Yamuna River runs through a major urban centre i.e. Delhi National Capital Region. The Yamuna River was divided into eight geomorphically distinct reaches on the basis of the assemblages of geomorphic units and the association of landscape, valley and floodplain settings. The morphological variability was analysed through stream power distribution and sediment load data at various stations. Stream power distribution of the Yamuna River basin is characterised by a non-linear pattern that was used to distinguish (a) high energy ‘natural' upstream reaches, (b) ‘anthropogenically altered', low energy middle stream reaches, and (c) ‘rejuvenated' downstream reaches again with higher stream power. The relationship between stream power and channel morphology in these reaches was integrated with sediment load data to define the maximum flow efficiency (MFE) as the threshold for geomorphic transition. This analysis supports the continuity of river processes and the significance of a holistic, basin-scale approach rather than isolated local scale analysis in river studies.

From coastal barriers to mountain belts - commonalities in fundamental geomorphic scaling laws

NASA Astrophysics Data System (ADS)

Lazarus, E.

2016-12-01

Overwash is a sediment-transport process essential to the form and resilience of coastal barrier landscapes. Driven by storm events, overwash leaves behind distinctive sedimentary features that, although intensively studied, have lacked unifying quantitative descriptions with which to compare their morphological attributes across documented examples or relate them to other morphodynamic phenomena. Geomorphic scaling laws quantify how measures of shape and size change with respect to another - information that helps to constrain predictions of future change and reconstructions of past environmental conditions. Here, a physical model of erosional and depositional overwash morphology yields intrinsic, allometric scaling laws involving length, width, area, volume, and alongshore spacing. Corroborative comparisons with natural washover morphology indicate scale invariance spanning several orders of magnitude. Several observers of the physical model remarked that the overwashed barrier resembled a dissected linear mountain front with an alluvial apron - an intriguing reimagining of the intended analog. Indeed, that resemblance is reflected quantitatively in these new scaling relationships, which align with canonical scaling laws for terrestrial and marine drainage basins and alluvial fans on Earth and Mars. This finding suggests disparate geomorphic systems that share common allometric properties may be related dynamically, perhaps by an influence more fundamental than characteristic erosion and deposition processes. Such an influence could come from emergent behavior at the intersection of advection and diffusion. Geomorphic behaviors at advection-diffusion transitions (and vice versa), specifically, could be the key to disentangling mechanistic causality from acausality in physical landscape patterns.

Geomorphic process fingerprints in submarine canyons

USGS Publications Warehouse

Brothers, Daniel S.; ten Brink, Uri S.; Andrews, Brian D.; Chaytor, Jason D.; Twichell, David C.

2013-01-01

Submarine canyons are common features of continental margins worldwide. They are conduits that funnel vast quantities of sediment from the continents to the deep sea. Though it is known that submarine canyons form primarily from erosion induced by submarine sediment flows, we currently lack quantitative, empirically based expressions that describe the morphology of submarine canyon networks. Multibeam bathymetry data along the entire passive US Atlantic margin (USAM) and along the active central California margin near Monterey Bay provide an opportunity to examine the fine-scale morphology of 171 slope-sourced canyons. Log–log regression analyses of canyon thalweg gradient (S) versus up-canyon catchment area (A) are used to examine linkages between morphological domains and the generation and evolution of submarine sediment flows. For example, canyon reaches of the upper continental slope are characterized by steep, linear and/or convex longitudinal profiles, whereas reaches farther down canyon have distinctly concave longitudinal profiles. The transition between these geomorphic domains is inferred to represent the downslope transformation of debris flows into erosive, canyon-flushing turbidity flows. Over geologic timescales this process appears to leave behind a predictable geomorphic fingerprint that is dependent on the catchment area of the canyon head. Catchment area, in turn, may be a proxy for the volume of sediment released during geomorphically significant failures along the upper continental slope. Focused studies of slope-sourced submarine canyons may provide new insights into the relationships between fine-scale canyon morphology and down-canyon changes in sediment flow dynamics.

Asymmetric progradation of a coastal mangrove forest controlled by combined fluvial and marine influence, Cù Lao Dung, Vietnam

NASA Astrophysics Data System (ADS)

Fricke, A. T.; Nittrouer, C. A.; Ogston, A. S.; Vo-Luong, H. P.

2017-09-01

Mangrove forests are an important means of coastal protection along many shorelines in the tropics, and are often associated with large rivers there. Isolating the contribution of any one factor to the progradation or retreat of a coastal mangrove forest is often hindered by the physical separation between sites that are subject to vastly different combinations of marine and fluvial influence. The mangrove forest at the seaward end of Cù Lao Dung, an island in the Mekong Delta, includes areas with progradation rates of 10 s m y-1, and areas that have experienced little to no progradation in recent decades. The physical proximity (<12 km) of these two environments allows detailed hydrodynamic and sediment-dynamic measurements to be related directly to morphologic change and century-scale stratigraphy. Contrary to conventional understanding, the region of mangrove forest prograding most rapidly is subject to the greatest wave attack, while progradation is slowest in the most quiescent area. Limited progradation here is the product of a reduction in the supply of sediment to certain parts of the mangrove forest due to nearby estuarine dynamics operating on spring-neap timescales. Measurements of sediment flux show net transport into the rapidly prograding part of the forest, and transport out from the part of the forest with minimal progradation. Century-scale rates of sediment accumulation determined using 210Pb geochronology are consistent with in-situ dynamical measurements and geomorphic evolution of the mangrove forest. Where progradation is most rapid, sediment accumulation rates (3.0-5.1 cm y-1) exceed the rate of local sea-level rise (∼1.5 cm y-1). In contrast, sediment-accumulation rates in the area of minimal progradation (0.8-2.8 cm y-1) only somewhat exceed the rate of local sea-level rise, if at all. Physical stratification is well preserved in cores from areas of rapid progradation, consistent with energetic transport processes and an ample sediment supply. Greater impact from bioturbation and episodic sediment delivery produce more variable bedding where progradation is less rapid. The presence of a supply-limited mangrove forest adjacent to a major sediment source highlights the complexity of sediment-supply pathways in coastal mangrove environments.

Analysis and classification of topographic flow steering and inferred geomorphic processes as a function of discharge in a mountain river

NASA Astrophysics Data System (ADS)

Gore, J.; Pasternack, G. B.; Wiener, J.

2016-12-01

Process-based river classification tends to be done at reach to catchment scales assuming channels are uniform and thus differentiated by the simple specific stream power metric. In fact, mountain rivers are highly variable at subreach scales to the point that local topographic steering may be the dominant control on geomorphic processes. This study presents a new framework for characterizing how stage-dependent topographic steering varies continuously down a river, leading to a classification of subreach landforms on the basis of the geomorphic mechanism of flow convergence routing. The two remote mountain river segments were located in the 3480-km2 Yuba River, with the upper South Yuba having a substantial sediment supply from legacy hydraulic gold mining and the mainstem Yuba downstream of New Bullards Bar Dam having a restricted sediment supply. Meter-scale DEMs were produced for both cases using airborne LiDAR and survey data. DEMs were slope detrended to focus the analysis on cross-sectional variability. DEMs were then heavily smoothed to allow for automated tracing of the valley centerline, and then cross-sectional rectangles were spaced every 5 m. The average width (W) and detrended bed elevation (Z) of the wetted area was computed from the DEM for each raster for 6-7 different river stages. Both width and cross-sectionally averaged bed elevation were standardized. The product of these two variables was computed as a measure of cross-sectional area, and is termed the geomorphic covariance (Czw) series when plotted along each river corridor. Cwz was then used to classify each cross-section as one of five distinct landform types: nozzle, wide bar, normal channel, constricted pool, and oversized pool- with this classification varying with discharge such that a section could, for example, function as a nozzle during low flow but an oversized pool at high flow, or any other combination. Longitudinal profiles of bed elevation, width, covariance, and landform type were analyzed for their stage-dependent patterns to understand their geomorphic significance and to contrast the two rivers. This new method may be the first example of a hierarchical, process-based classification at the subreach scale in which one mechanism is assessed for how it varies not only in space, but as a function of discharge.

Fractal topography and subsurface water flows from fluvial bedforms to the continental shield

USGS Publications Warehouse

Worman, A.; Packman, A.I.; Marklund, L.; Harvey, J.W.; Stone, S.H.

2007-01-01

Surface-subsurface flow interactions are critical to a wide range of geochemical and ecological processes and to the fate of contaminants in freshwater environments. Fractal scaling relationships have been found in distributions of both land surface topography and solute efflux from watersheds, but the linkage between those observations has not been realized. We show that the fractal nature of the land surface in fluvial and glacial systems produces fractal distributions of recharge, discharge, and associated subsurface flow patterns. Interfacial flux tends to be dominated by small-scale features while the flux through deeper subsurface flow paths tends to be controlled by larger-scale features. This scaling behavior holds at all scales, from small fluvial bedforms (tens of centimeters) to the continental landscape (hundreds of kilometers). The fractal nature of surface-subsurface water fluxes yields a single scale-independent distribution of subsurface water residence times for both near-surface fluvial systems and deeper hydrogeological flows. Copyright 2007 by the American Geophysical Union.

How quickly do earthquakes get locked in the landscape? One year of erosion on El Mayor-Cucapah rupture scarps imaged by repeat terrestrial lidar scans

NASA Astrophysics Data System (ADS)

Elliott, A. J.; Oskin, M. E.; Banesh, D.; Gold, P. O.; Hinojosa-Corona, A.; Styron, R. H.; Taylor, M. H.

2012-12-01

Differencing repeat terrestrial lidar scans of the 2010 M7.2 El Mayor-Cucapah (EMC) earthquake rupture reveals the rapid onset of surface processes that simultaneously degrade and preserve evidence of coseismic fault rupture in the landscape and paleoseismic record. We surveyed fresh fault rupture two weeks after the 4 April 2010 earthquake, then repeated these surveys one year later. We imaged fault rupture through four substrates varying in degree of consolidation and scarp facing-direction, recording modification due to a range of aeolian, fluvial, and hillslope processes. Using lidar-derived DEM rasters to calculate the topographic differences between years results in aliasing errors because GPS uncertainty between years (~1.5cm) exceeds lidar point-spacing (<1.0cm) shifting the raster sampling of the point cloud. Instead, we coregister each year's scans by iteratively minimizing the horizontal and vertical misfit between neighborhoods of points in each raw point cloud. With the misfit between datasets minimized, we compute the vertical difference between points in each scan within a specified neighborhood. Differencing results reveal two variables controlling the type and extent of erosion: cohesion of the substrate controls the degree to which hillslope processes affect the scarp, while scarp facing direction controls whether more effective fluvial erosion can act on the scarp. In poorly consolidated materials, large portions (>50% along strike distance) of the scarp crest are eroded up to 5cm by a combination of aeolian abrasion and diffusive hillslope processes, such as rainsplash and mass-wasting, while in firmer substrate (i.e., bedrock mantled by fault gouge) there is no detectable hillslope erosion. On the other hand, where small gullies cross downhill-facing scarps (<5% along strike distance), fluvial erosion has caused 5-50cm of headward scarp retreat in bedrock. Thus, although aeolian and hillslope processes operate over a greater along-strike distance, fluvial processes concentrated in pre-existing bedrock gullies transport a far greater volume of material across the scarp. Substrate cohesiveness dictates the degree to which erosive processes act to relax the scarp (e.g., gravels erode more easily than bedrock). However, scarp locations that favor fluvial processes suffer rapid, localized erosion of vertical scarp faces, regardless of substrate. Differential lidar also reveals debris cones formed at the base of the scarp below locations of scarp crest erosion. These indicate the rapid growth of a colluvial wedge. Where a fissure occupies the base of the scarp we observe nearly complete in-filling by silt and sand moved by both mass wasting and fluvial deposition, indicating that fissure fills observed in paleoseismic trenches likely bracket the age of an earthquake to within one year. We find no evidence of differential postseismic tectonic deformation across the fault within the ~100m aperture of our surveys.

Unsteady Landscapes: Climatic and Tectonic Controls on Fluvial Terrace Formation

NASA Astrophysics Data System (ADS)

Clubb, F. J.; Mudd, S. M.

2017-12-01

Fluvial terraces are common landforms throughout mountainous regions which represent abandoned remnants of active river systems and their floodplains. The formation of these landforms points to a fundamental unsteadiness in the incision rate of the fluvial network, providing important information on channel response to climatic, tectonic, and base-level forcing, sediment storage and dynamics within mountainous systems, and the relative importance of lateral and vertical incision rates. In his 1877 Report on the Geology of the Henry Mountains, G.K. Gilbert suggested that strath terraces may form due to climatically-driven increase in sediment supply, causing armouring of the channel bed and hindering vertical incision. An alternative hypothesis suggests that strath terraces may be preserved through progressive tectonic uplift or base-level fall. These different formation mechanisms should result in varying distribution of terrace elevations along channels: if terraces are formed through climate-driven variations in sediment supply, we might expect that terrace elevations would be random, whereas progressive fluvial incision should result in a series of terraces with a systematic elevation pattern. Here we test alternative hypotheses for strath terrace formation using a new method for objectively and rapidly identifying terrace surfaces from digital elevation models (DEMs) over large spatial scales. Our new method identifies fluvial terraces using their gradient and elevation compared to the modern channel, thresholds of which are statistically calculated from the DEM and do not need to be set manually by the user. We use this method to extract fluvial terraces for every major river along the coast of California, and quantify their distribution and elevation along the fluvial long profile. Our results show that there is no systematic pattern in terrace elevations despite a well-constrained spatial variation in uplift rates, suggesting that terraces in this region do not reflect the influence of regional tectonics, and may instead be the formed through climatic variations or autogenic fluvial processes.

Fluvial process and the establishment of bottomland trees

USGS Publications Warehouse

Scott, Michael L.; Friedman, Jonathan M.; Auble, Gregor T.

1996-01-01

The relation between streamflow and establishment of bottomland trees is conditioned by the dominant fluvial process or processes acting along a stream. For successful establishment, cottonwoods, poplars, and willows require bare, moist surfaces protected from disturbance. Channel narrowing, channel meandering, and flood deposition promote different spatial and temporal patterns of establishment. During channel narrowing, the site requirements are met on portions of the bed abandoned by the stream, and establishment is associated with a period of low flow lasting one to several years. During channel meandering, the requirements are met on point bars following moderate or higher peak flows. Following flood deposition, the requirements are met on flood deposits ;high above the channel bed. Flood deposition can occur along most streams, but where a channel is constrained by a narrow valley, this process may be the only mechanism that can produce a bare, moist surface high enough to be safe from future disturbance. Because of differences in local bedrock, tributary influence, or geologic history, two nearby reaches of the same stream may be dominated by different fluvial processes and have different spatial and temporal patterns of trees. We illustrate this phenomenon with examples from forests of plains cottonwood (Populus deltoides ssp. monilifera) along meandering and constrained reaches of the Missouri River in Montana.

Recognition of strong seasonality and climatic cyclicity in an ancient, fluvially dominated, tidally influenced point bar: Middle McMurray Formation, Lower Steepbank River, north-eastern Alberta, Canada

NASA Astrophysics Data System (ADS)

Jablonski, Bryce V. J.; Dalrymple, Robert W.

2016-04-01

Inclined heterolithic stratification in the Lower Cretaceous McMurray Formation, exposed along the Steepbank River in north-eastern Alberta, Canada, accumulated on point bars of a 30 to 40 m deep continental-scale river in the fluvial-marine transition. This inclined heterolithic stratification consists of two alternating lithologies, sand and fine-grained beds. Sand beds were deposited rapidly by unidirectional currents and contain little or no bioturbation. Fine-grained beds contain rare tidal structures, and are intensely bioturbated by low-diversity ichnofossil assemblages. The alternations between the sand and fine-grained beds are probably caused by strong variations in fluvial discharge; that are believed to be seasonal (probably annual) in duration. The sand beds accumulated during river floods, under fluvially dominated conditions when the water was fresh, whereas the fine-grained beds accumulated during the late stages of the river flood and deposition continued under tidally influenced brackish-water conditions during times of low-river flow (i.e. the interflood periods). These changes reflect the annual migration in the positions of the tidal and salinity limits within the fluvial-marine transition that result from changes in river discharge. Sand and fine-grained beds are cyclically organized in the studied outcrops forming metre-scale cycles. A single metre-scale cycle is defined by a sharp base, an upward decrease in sand-bed thickness and upward increases in the preservation of fine-grained beds and the intensity of bioturbation. Metre-scale cycles are interpreted to be the product of a longer term (decadal) cyclicity in fluvial discharge, probably caused by fluctuations in ocean or solar dynamics. The volumetric dominance of river-flood deposits within the succession suggests that accumulation occurred in a relatively landward position within the fluvial-marine transition. This study shows that careful observation can reveal much about the interplay of processes within the fluvial-marine transition, which in turn provides a powerful tool for determining the palaeo-environmental location of a deposit within the fluvial-marine transition.

Characterizing the geomorphic setting of precariously balanced rocks using terrestrial laser scanning technology

NASA Astrophysics Data System (ADS)

Haddad, D. E.; Arrowsmith, R.

2009-12-01

Terrestrial laser scanning (TLS) technology is rapidly becoming an effective three-dimensional imaging tool. Precariously balanced rocks are a subset of spheroidally weathered boulders. They are balanced on bedrock pedestals and are formed in upland drainage basins and pediments of exhumed plutons. Precarious rocks are used as negative evidence of earthquake-driven extreme ground motions. Field surveys of PBRs are coupled with cosmogenic radionuclide (CRN) surface exposure dating techniques to determine their exhumation rates. These rates are used in statistical simulations to estimate the magnitudes and recurrences of earthquake-generated extreme ground shaking as a means to physically validate seismic hazard analyses. However, the geomorphic setting of PBRs in the landscape is poorly constrained when interpreting their exhumation rates from CRN surface exposure dates. Are PBRs located on steep or gentle hillslopes? Are they located near drainages or hillslope crests? What geomorphic processes control the spatial distribution of PBRs in a landscape, and where do these processes dominate? Because the fundamental hillslope transport laws are largely controlled by local hillslope gradient and contributing area, the location of a PBR is controlled by the geomorphic agents and their rates acting on it. Our latest efforts involve using a combination of TLS and airborne laser swath mapping (ALSM) to characterize the geomorphic situation of PBRs. We used a Riegl LPM 800i (LPM 321) terrestrial laser scanner to scan a ~1.5 m tall by ~1 m wide precariously balanced rock in the Granite Dells, central Arizona. The PBR was scanned from six positions, and the scans were aligned to a point cloud totaling 3.4M points. We also scanned a ~50 m by ~150 m area covering PBR hillslopes from five scan positions. The resulting 5.5M points were used to create a digital terrain model of precarious rocks and their hillslopes. Our TLS- and ALSM-generated surface models and DEMs provide a unique opportunity to understand the roles of hillslope-scale geomorphic processes in the PBR life cycle. Initial results show that the studied PBRs are located near hillslope crests ~33 m above the nearest drainages and on slopes >17°. No PBRs were found on gentle slopes adjacent to channels, suggesting that hillslope crests are conducive to preserving PBRs. Understanding these landscape morphometrics for precarious rock zones is critical to building our confidence in interpreting PBR exhumation rates from CRN dating techniques, thus improving the evaluation of seismic hazard analyses.

Shaler: in situ analysis of a fluvial sedimentary deposit on Mars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edgar, Lauren A.; Gupta, Sanjeev; Rubin, David M.

This article characterizes the detailed sedimentology of a fluvial sandbody on Mars for the first time and interprets its depositional processes and palaeoenvironmental setting. Despite numerous orbital observations of fluvial landforms on the surface of Mars, ground-based characterization of the sedimentology of such fluvial deposits has not previously been possible. Results from the NASA Mars Science Laboratory Curiosity rover provide an opportunity to reconstruct at fine scale the sedimentary architecture and palaeomorphology of a fluvial environment on Mars. This work describes the grain size, texture and sedimentary facies of the Shaler outcrop, reconstructs the bedding architecture, and analyses cross-stratification tomore » determine palaeocurrents. On the basis of bedset geometry and inclination, grain-size distribution and bedform migration direction, this study concludes that the Shaler outcrop probably records the accretion of a fluvial barform. The majority of the outcrop consists of large-scale trough cross-bedding of coarse sand and granules. Palaeocurrent analyses and bedform reconstruction indicate that the beds were deposited by bedforms that migrated towards the north-east, across the surface of a bar that migrated south-east. Stacked cosets of dune cross-bedding suggest aggradation of multiple bedforms, which provides evidence for short periods of sustained flow during Shaler deposition. However, local evidence for aeolian reworking and the presence of potential desiccation cracks within the outcrop suggest that fluvial deposition may have been intermittent. The uppermost strata at Shaler are distinct in terms of texture and chemistry and are inferred to record deposition from a different sediment dispersal system with a contrasting provenance. The outcrop as a whole is a testament to the availability of liquid water on the surface of Mars in its early history.« less