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Sample records for aguas fluviales utilizando

  1. Secondary natural gas recovery in mature fluvial sandstone reservoirs, Frio Formation, Agua Dulce Field, South Texas

    SciTech Connect

    Ambrose, W.A.; Levey, R.A. ); Vidal, J.M. ); Sippel, M.A. ); Ballard, J.R. ); Coover, D.M. Jr. ); Bloxsom, W.E. )

    1993-09-01

    An approach that integrates detailed geologic, engineering, and petrophysical analyses combined with improved well-log analytical techniques can be used by independent oil and gas companies of successful infield exploration in mature Gulf Coast fields that larger companies may consider uneconomic. In a secondary gas recovery project conducted by the Bureau of Economic Geology and funded by the Gas Research Institute and the U.S. Department of Energy, a potential incremental natural gas resource of 7.7 bcf, of which 4.0 bcf may be technically recoverable, was identified in a 490-ac lease in Agua Dulce field. Five wells in this lease had previously produced 13.7 bcf from Frio reservoirs at depths of 4600-6200 ft. The pay zones occur in heterogeneous fluvial sandstones offset by faults associated with the Vicksburg fault zone. The compartments may each contain up to 1.0 bcf of gas resources with estimates based on previous completions and the recent infield drilling experience of Pintas Creek Oil Company. Uncontacted gas resources occur in thin (typically less than 10 ft) bypassed zones that can be identified through a computed log evaluation that integrates open-hole logs, wireline pressure tests, fluid samples, and cores. At Agua Dulce field, such analysis identified at 4-ft bypassed zone uphole from previously produced reservoirs. This reservoir contained original reservoir pressure and flowed at rates exceeding 1 mmcf/d. The expected ultimate recovery is 0.4 bcf. Methodologies developed in the evaluation of Agua Dulce field can be successfully applied to other mature gas fields in the south Texas Gulf Coast. For example, Stratton and McFaddin are two fields in which the secondary gas recovery project has demonstrated the existence of thin, potentially bypassed zones that can yield significant incremental gas resources, extending the economic life of these fields.

  2. Three-dimensional seismic fluvial architecture of the basal middle Frio Formation, Stratton and Agua Dulce fields, south Texas

    NASA Astrophysics Data System (ADS)

    El-Mowafy, Hamed Zeidan

    Facies architectural models are developed for the Oligocene basal middle Frio meandering fluvial system at Stratton and Agua Dulce fields in south Texas. These models are based on detailed mapping and are important to understand reservoir heterogeneities. The basal middle Frio is characterized in terms of a hierarchy of architectural elements at different heterogeneity levels. In order from small-scale to large-scale, these are facies, channel-belt, systems tract, and depositional sequence. A structural architecture model integrating well logs and 3-D seismic data is developed for the basal middle Frio. It indicates that growth faults are syndepositional and cut through the basal middle Frio Formation and younger sediments in the Stratton-Agua Dulce area. These affect the architecture of the sandstone bodies stacked in that interval. The dimensions, directions, and spatial locations of the basal middle Frio facies architectural elements are predicted from log facies maps and confirmed from seismic amplitude maps. RMS amplitude was related to rock properties and can be used to predict, among other things, facies type and net sand thickness. Seismic sequence stratigraphic models constructed for the basal middle Frio non-marine fluvial strata predict the location of new reservoirs that offer potential reserve growth in the Stratton-Agua Dulce field area. Observations from well logs and 3-D seismic data suggest that accommodation changes and nodal avulsions are possible factors controlling the basal middle Frio fluvial architecture. A 2-D facies architectural model is developed which describes the changes in the stacking patterns of the basal middle Frio sandstone deposits. Changes in the stacking patterns are a reflection of changes in accommodation space, avulsion frequency and sediment accumulation rate. The integrated 3-D fluvial facies architecture model of the basal middle Frio indicates that growth faults controlled the stacking patterns of the basal middle Frio sandstone reservoirs. Results of this study are significant in exploring for and developing similar meandering fluvial reservoirs affected by growth faulting in the Texas Gulf Coast and in similar geological settings worldwide.

  3. Simulations of Fluvial Landscapes

    NASA Astrophysics Data System (ADS)

    Cattan, D.; Birnir, B.

    2013-12-01

    The Smith-Bretherton-Birnir (SBB) model for fluvial landsurfaces consists of a pair of partial differential equations, one governing water flow and one governing the sediment flow. Numerical solutions of these equations have been shown to provide realistic models in the evolution of fluvial landscapes. Further analysis of these equations shows that they possess scaling laws (Hack's Law) that are known to exist in nature. However, the simulations are highly dependent on the numerical methods used; with implicit methods exhibiting the correct scaling laws, but the explicit methods fail to do so. These equations, and the resulting models, help to bridge the gap between the deterministic and the stochastic theories of landscape evolution. Slight modifications of the SBB equations make the results of the model more realistic. By modifying the sediment flow equation, the model obtains more pronounced meandering rivers. Typical landsurface with rivers.

  4. The Fluvial Information System

    NASA Astrophysics Data System (ADS)

    Dugdale, S. J.; Carbonneau, P.; Clough, S.

    2009-12-01

    River ecologists have long been aware that our understanding of lotic ecology is limited by our lack of methods applicable to catchment scale processes. Furthermore, the EU’s Water Framework Directive states that surface waters must be managed at catchment scales. This has created a need for a new approach to high-resolution catchment scale data collection in fluvial environments. In response to this, remote sensing has been the focus of increasing interest in river science, and it is now possible to map parameters such as water depth, grain size and habitat type with sub-metric resolutions over large areas. These techniques are capable of yielding unprecedented amounts of information about river systems, and with such levels of information, crucial questions about catchment scale ecology can now be addressed. However, this intensive approach produces vast amounts of raster data leading to significant issues in terms of data management, and extracting spatially explicit information from large image databases poses a significant challenge which must be resolved if fluvial remote sensing methods are to deliver their potential. GIS has already been successfully applied to manage remotely sensed data. Unfortunately, when applied to fluvial remote sensing raster data, traditional GIS appears limited and unsuited to the specific tasks required by river scientists and managers, and experience with GIS packages has shown that they become overwhelmed when faced with datasets comprising thousands of rasters. Another fundamental issue with traditional GIS packages is the use of established Cartesian map projection systems. Given that rivers are curvilinear entities, the use of Cartesian grid map projections is mismatched and curvilinear coordinate systems unique to each river will be required. This paper introduces the Fluvial Information System (FIS), a raster based GIS-type system designed to manage fluvial remote sensing data and automatically extract meaningful information. The FIS rests on a 2D river coordinate system. Modelled after the curvilinear system presented by Legleiter and Kyriakidis, 2006, the downstream axis of this system follows the river path as modelled by cubic splines whilst the cross-stream direction is locally orthogonal to the main axis. This river coordinate system is generated automatically by automatically detecting and digitizing successive channel midpoints from classified georeferenced imagery. The end result is a coordinate system which allows for a unique spatial localization of each image pixel and an accurate determination of the inter-image spatial relationships. This adaptation of GIS to fluvial systems is a significant innovation with consequences to fundamental river science and management. With the FIS, managers can make effective use of the information contained in high resolution imagery. For example, such information can now allow us to quantify the available habitat for important species such as salmonids and be used to support river management decisions. Additionally, this information can be used in fundamental investigations on large scale patterns of habitat distribution and spatial ecology. The Fluvial Information System offers a unique tool which promises to modernise our understanding of lotic ecology and our ability to manage rivers.

  5. Fluvial networks of the Iberian Peninsula: a chronological framework

    NASA Astrophysics Data System (ADS)

    Santisteban, Juan I.; Schulte, Lothar

    2007-11-01

    Knowledge of the evolution of Spanish fluvial networks has improved during recent years as more river systems have been studied and more geochronological data has become available. However, the chronological framework is a major issue as the range of applications is limited by methodological constraints and spatial coverage is sparse. Integration of 'absolute' dating methods with biostratigraphy and palaeomagnetism permits the recent evolution of these river systems to be reviewed. The timing of incision from the Late Neogene to the present varies between the major Iberian fluvial systems, depending on the substrata and tectonic settings. Early Pleistocene and older fluvial sequences in the core areas of the Iberian Peninsula provide a more extensive record of fluvial evolution and are better preserved than the terrace flights in the coastal lowlands. Middle Pleistocene sequences are well developed in most of the major river systems in Iberia, particularly those of the Tajo, Guadalquivir and Aguas River, and frequently represent the principal climatic cycles of that period, although tectonic and sea-level effects can also be seen. For Late Pleistocene to Holocene times, the scheme becomes more complex. Our review suggests that each river system has responded differently to local and regional climate control, glacial and periglacial processes in headwaters in high mountain areas, glacio-eustatic sea-level changes and local and regional tectonic patterns.

  6. Floods and Fluvial Wood

    NASA Astrophysics Data System (ADS)

    Comiti, F.

    2014-12-01

    Several studies have recently addressed the complex interactions existing at various spatial scales among riparian vegetation, channel morphology and wood storage. The majority of these investigations has been carried out in relatively natural river systems, focusing mostly on the long-term vegetation-morphology dynamics under "equilibrium" conditions. Little is still known about the role of flood events - of different frequency/magnitude - on several aspects of such dynamics, e.g. entrainment conditions of in-channel wood, erosion rates of vegetation from channel margins and from islands, transport distances of wood elements of different size along the channel network. Even less understood is how the river's evolutionary trajectory may affect these processes, and thus the degree to which conceptual models derivable from near-natural systems could be applicable to human-disturbed channels. Indeed, the different human pressures - present on most river basins worldwide - have greatly impaired the morphological and ecological functions of fluvial wood, and the attempts to "restore" in-channel wood storage are currently carried out without a sufficient understanding of wood transport processes occurring during floods. On the other hand, the capability to correctly predict the magnitude of large wood transport during large floods is now seen as crucial - especially in mountain basins - for flood hazard mapping, as is the identification of the potential wood sources (e.g. landslides, floodplains, islands) for the implementation of sound and effective hazard mitigation measures. The presentation will first summarize the current knowledge on fluvial wood dynamics and modelling at different spatial and temporal scales, with a particular focus on mountain rivers. The effects of floods of different characteristics on vegetation erosion and wood transport will be then addressed presenting some study cases from rivers in the European Alps and in the Italian Apennines featuring different degrees of human alteration. Finally, several conclusions about the applicability of wood transport modelling and on rationale vegetation/wood management strategies will be drawn.

  7. Quaternary fluvial archives: achievements of the Fluvial Archives Group

    NASA Astrophysics Data System (ADS)

    Bridgland, David; Cordier, Stephane; Herget, Juergen; Mather, Ann; Vandenberghe, Jef; Maddy, Darrel

    2013-04-01

    In their geomorphological and sedimentary records, rivers provide valuable archives of environments and environmental change, at local to global scales. In particular, fluvial sediments represent databanks of palaeoenvironment and palaeoclimatic (for example) of fossils (micro- and macro-), sedimentary and post-depositional features and buried soils. Well-dated sequences are of the most value, with dating provided by a wide range of methods, from radiometric (numerical) techniques to included fossils (biostratigraphy) and/or archaeological material. Thus Quaternary fluvial archives can also provide important data for studies of Quaternary biotic evolution and early human occupation. In addition, the physical disposition of fluvial sequences, be it as fragmented terrace remnants or as stacked basin-fills, provides valuable information about geomorphological and crustal evolution. Since rivers are long-term persistent features in the landscape, their sedimentary archives can represent important frameworks for regional Quaternary stratigraphy. Fluvial archives are distributed globally, being represented on all continents and across all climatic zones, with the exception of the frozen polar regions and the driest deserts. In 1999 the Fluvial Archives Group (FLAG) was established, as a working group of the Quaternary Research Association (UK), aimed at bringing together those interested in such archives. This has evolved into an informal organization that has held regular biennial combined conference and field-trip meetings, has co-sponsored other meetings and conference sessions, and has presided over two International Geoscience Programme (IGCP) projects: IGCP 449 (2000-2004) 'Global Correlation of Late Cenozoic Fluvial Deposits' and IGCP 518 (2005-2007) 'Fluvial sequences as evidence for landscape and climatic evolution in the Late Cenozoic'. Through these various activities a sequence of FLAG publications has appeared, including special issues in a variety of journals, amassing a substantial volume of information on fluvial archives worldwide. This presentation will highlight some of these data and will describe important patterns observed and interpretations arising therefrom.

  8. Understanding the Fluvial Critical Zone

    NASA Astrophysics Data System (ADS)

    Bätz, N.; Lane, S. N.; Temme, A. J. A. M.; Lang, F.

    2012-04-01

    Geomorphological modelling has evolved significantly the representation of the link between river morphology, flow processes and sediment transport; notably recently, with an emphasis upon the interactions between vegetation dynamics and morphodynamics. Nevertheless, vegetation dynamics have tended to be treated as a simplistic "black box" in which time replaces the more complex underlying processes. Thus, riparian vegetation dynamics not only result from interactions between surface-flow, topography and vegetation resistance to disturbance, but also soil development within the fluvial zone, which affects nutrient and water supply. More generally labeled the critical zone, there is a lack of considering the "critical fluvial zone" in geomorphological models. Understanding the key drivers of this system, thus the processes interrelating vegetation, topography, soil (formation), subsurface- and surface-flow, are crucial to understand how riverine landscapes respond to increasing human pressure and to climate change. In this poster, we consider the likely nature of a braided river critical fluvial zone. Braided rivers in deglaciated forelands provide an opportunity to study the fluvial critical zone due to their dynamic properties, the restricted physical size, the simple ecosystems and the space-for-time relation caused by glacier retreatment after the "Little Ice Age". The poster aims to commence a discussion on the fluvial critical zone, showing first results about: a) the system understanding of a braided river set in a recently deglaciated alpine foreland; b) methodological approaches to quantify the identified interrelating key processes; c) how quantitative understanding can be integrated into fluvial geomorphological modelling.

  9. Meandering: fluvial versus tidal. (Invited)

    NASA Astrophysics Data System (ADS)

    Seminara, G.

    2009-12-01

    Tidal meanders (Marani et al, Water Resour Res, 2002) display similarities as well as important differences from fluvial meanders (Seminara, J Fluid Mech, 2006). Like fluvial meanders they have characteristic wavelengths scaling with channel width: this is why the convergent character of tidal channels leads to meander wavelengths decaying landward. Unlike fluvial meanders, the typical curvature spectra of tidal meanders contain even harmonics: hence, meander skewing does non display any distinct correlation with the flow direction and the known Kinoshita curve, which approximates the shape of fluvial meanders, is not appropriate to tidal meanders. Additional constraints are brought up by the spatial gradients of the basic bed profile connected to the finite length of tidal channels at equilibrium. In fact, it has been theoretically established (Schuttelaars and De Swart, Eur J Mech, B/Fluids, 1996, Seminara et al, J Fluid Mech submitted, 2009) and confirmed by controlled laboratory experiments (Tambroni et al., J Geoph Res, 2005) that tidal channels closed at one end and connected at the other end with a tidal sea, evolve towards an equilibrium configuration characterized by a ‘slow’ landward decay of the average flow depth. An equilibrium length of the channel is then determined by the formation of a shoreline. Channel curvature affects the lateral equilibrium topography and gives rise to a pattern of point bars and scour pools resembling that of fluvial channels. With some notable differences, though. In fact, Solari et al (J Fluid Mech, 2001) showed that long sequences of weakly sinuous identical meandering channels subject to a symmetrical tidal forcing develop a symmetrical bar-pool pattern with small symmetrical oscillations during the tidal cycle. However, in the laboratory investigations of Garotta et al. (Proceedings RCEM5,2007) the bar-pool pattern was somehow unexpected. In a first experiment, it was in phase with curvature only in the inner half of the channel, whereas the seaward pattern displayed deposition at the outer bends and scour at the inner bends, a pattern which would clearly be planimetrically unstable if the channel walls were erodible. In a second experiment, in the final stage, close to equilibrium, point bars were out of phase with respect to curvature throughout the whole channel. A possible explanation of this striking observation is that asymmetry of an observed pattern must be associated with either flood- or ebb- dominance of the basic flow field: some indication, in this respect, comes from the observation that the bar-pool pattern changed in time with the hydrodynamics as the average bed profile evolved towards equilibrium. A second key to be explored is the very nature of the observed bar-pool pattern, recalling that the relationship of tidal alternate (free) bars to point (forced) bars differs from its fluvial counterpart: tidal free bars are non migrating features at equilibrium (Seminara and Tubino, J Fluid Mech, 2001), bar migration arising from the role of overtides (Garotta et al, Phys. of Fluids, 2006). Distinguishing free from forced bars is then harder than in the fluvial case and the issue of their possible coexistence needs be revisited. Finally, the plan form evolution of tidal meanders is typically slower than in the fluvial case: not surprisingly, as sediment transport is very weak close to channel equilibrium.

  10. What is a fluvial levee?

    NASA Astrophysics Data System (ADS)

    Brierley, Gary J.; Ferguson, Rob J.; Woolfe, Ken J.

    1997-12-01

    Fluvial levees are elevated partitions between channels and floodplains. Because of their character and position, levees may provide critical controls on, and insights into, geomorphic processes that determine the distribution of water and sediment within river systems. Few studies have analysed the character, distribution, sedimentology and processes that form levees in modern depositional environments. Characterisation of levee deposits from the Mississippi River continues to form the basis for most levee interpretations from the rock record. This discussion paper assesses the reliability of interpretations of levee deposits in numerous examples from the rock record, and their associated inferences for river style. This uncertainty reflects the lack of definitive sedimentological attributes for levee deposits, their limited preservation potential, and the fact that levee identification in the rock record is inhibited by the reliance on geometric descriptors or indirect associations between channel and floodplain facies. Given these concerns, it is suggested that geomorphologists and sedimentologists need to recognise the limitations of our present knowledge of levees, and work towards a more systematic understanding of these significant fluvial landforms in the full spectrum of modern (and ancient) river settings.

  11. Laser Scanning Applications in Fluvial Geomorphology

    NASA Astrophysics Data System (ADS)

    Alho, P.

    2014-12-01

    During recent decades, the use of high-resolution laser scanning data in fluvial studies has rapidly increased. Airborne laser scanning (ALS) can be used to extensively map riverine topography. Laser scanning data have great potential to improve the effectiveness of topographical data acquisition and the accuracy and resolution of DTMs (Digital Terrain Models) needed in fluvial geomorphology. Airborne Laser Scanning (ALS) is applicable for mapping areas varying from reach to catchment scale and these data are, therefore, particularly suitable, especially for hydraulic modelling, mapping of flood inundation, and the detection of macro-scale fluvial geomorphology. With Terrestrial Laser Scanning (TLS) a spatial resolution of less than 1 mm and a range accuracy of few millimetres can be achieved. Mobile Laser Scanning (MLS) enables a remarkably faster survey approach compared to the conventional TLS method. One of the newest applications of MLS approaches involves a boat/cart/backpack -based mobile mapping system. This set-up includes laser scanning and imaging from a platform moving along a river course or floodplain and may be used to expand the spatial extent of terrestrial scanning. Detailed DTMs derived from laser scanning data can be used to improve the recognition of fluvial landforms, the geometric data of hydraulic modelling, and the estimation of flood inundation extents and the associated fluvial processes. Fluvial environments also offer challenges for the application of laser scanning techniques. Factors such as vegetation cover, terrain undulation, coarse surface materials and water surfaces may distort a laser scanning survey.

  12. Agua Caliente and Their Music.

    ERIC Educational Resources Information Center

    Ryterband, Roman

    1979-01-01

    Discusses the traditional music of the Agua Caliente band of California's Desert Cahuilla Indian tribe, including accompanying instruments, types of songs, thematic material, and performance routines. Exploring the structure of the music, the article describes meter, tempo, harmony and tonal gravitations, and use of words. (DS)

  13. Fluvial mudstone breccias and their petroleum significance

    SciTech Connect

    Putnam, P.E.

    1987-05-01

    The classic fining-upward model of fluvial deposition places mudstone breccia fragments as basal channel lag deposits. Basal breccias can form by bank erosion and collapse by migrating channels and channel down-cutting into preexisting mudstones. However, mudstone breccias associated with fluvial sediments display much wider distributions and can be found at the top of channel fills. Some formative mechanisms for breccias found toward the tops of fluvial sequences are (1) gravity sliding down point bar surfaces; (2) bank erosion and collapse by migrating underfit streams found within abandoned channel reaches undergoing vertical accretion and; (3) oversteepening and collapse of channel banks in response to stage fluctuations. Thus, breccia deposits can be located above or adjacent to well-sorted porous and permeable sands. In the subsurface, fluvial breccias are difficult to recognize in core if individual clasts are larger than the borehole diameter and flat lying. Dense concentrations of clasts also influence log readings by displaying high gamma-ray and relatively positive spontaneous potential responses. Core analyses commonly give misleadingly low indications of porosity and permeability because of the relatively small sample sizes available. It is very easy to mistake thick, dense concentrations of mudstone breccia for the deposits of shale-filled channels. Breccias found at the top of fluvial sequences are commonly overlooked reservoirs because hydrocarbons will be found in zones characterized by very large impervious blocks formed of muddy sediment. Recognition of the presence and distribution of breccias is crucial in the exploration and development of channel reservoirs.

  14. The fluvial record of climate change.

    PubMed

    Macklin, M G; Lewin, J; Woodward, J C

    2012-05-13

    Fluvial landforms and sediments can be used to reconstruct past hydrological conditions over different time scales once allowance has been made for tectonic, base-level and human complications. Field stratigraphic evidence is explored here at three time scales: the later Pleistocene, the Holocene, and the historical and instrumental period. New data from a range of field studies demonstrate that Croll-Milankovitch forcing, Dansgaard-Oeschger and Heinrich events, enhanced monsoon circulation, millennial- to centennial-scale climate variability within the Holocene (probably associated with solar forcing and deep ocean circulation) and flood-event variability in recent centuries can all be discerned in the fluvial record. Although very significant advances have been made in river system and climate change research in recent years, the potential of fluvial palaeohydrology has yet to be fully realized, to the detriment of climatology, public health, resource management and river engineering. PMID:22474679

  15. Applied fluvial geomorphology. Report No. 31

    SciTech Connect

    MacBroom, J.G.

    1981-03-01

    The first portion of this report discusse the geologic properties and characteristics of natural rivers and floodplains. The second part outlines the influence of man on fluvial geomorphology, ecological considerations, and the natural characteristics of rivers that should be applied in the design of river and bridge projects.

  16. Applied fluvial geomorphology. Report No. 31

    SciTech Connect

    MacBroom, J.G.

    1981-03-01

    The first portion of this report discusses the geologic properties and characteristics of natural rivers and floodplains. The second part outlines the influence of man on fluvial geomorphology, ecological considerations, and the natural characteristics of rivers that should be applied in the design of river and bridge projects.

  17. 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.

  18. Large Fluvial Fans and Exploration for Hydrocarbons

    NASA Technical Reports Server (NTRS)

    Wilkinson, Murray Justin

    2005-01-01

    A report discusses the geological phenomena known, variously, as modern large (or large modern) fluvial fans or large continental fans, from a perspective of exploring for hydrocarbons. These fans are partial cones of river sediment that spread out to radii of 100 km or more. Heretofore, they have not been much recognized in the geological literature probably because they are difficult to see from the ground. They can, however, be seen in photographs taken by astronauts and on other remotely sensed imagery. Among the topics discussed in the report is the need for research to understand what seems to be an association among fluvial fans, alluvial fans, and hydrocarbon deposits. Included in the report is an abstract that summarizes the global distribution of large modern fluvial fans and a proposal to use that distribution as a guide to understanding paleo-fluvial reservoir systems where oil and gas have formed. Also included is an abstract that summarizes what a continuing mapping project has thus far revealed about the characteristics of large fans that have been found in a variety of geological environments.

  19. A fluvial mercury budget for Lake Ontario.

    PubMed

    Denkenberger, Joseph S; Driscoll, Charles T; Mason, Edward; Branfireun, Brian; Warnock, Ashley

    2014-06-01

    Watershed mercury (Hg) flux was calculated for ten inflowing rivers and the outlet for Lake Ontario using empirical measurements from two independent field-sampling programs. Total Hg (THg) flux for nine study watersheds that directly drain into the lake ranged from 0.2 kg/yr to 13 kg/yr, with the dominant fluvial THg load from the Niagara River at 154 kg/yr. THg loss at the outlet (St. Lawrence River) was 68 kg/yr and has declined approximately 40% over the past decade. Fluvial Hg inputs largely (62%) occur in the dissolved fraction and are similar to estimates of atmospheric Hg inputs. Fluvial mass balances suggest strong in-lake retention of particulate Hg inputs (99%), compared to dissolved total Hg (45%) and methyl Hg (22%) fractions. Wetland land cover is a good predictor of methyl Hg yield for Lake Ontario watersheds. Sediment deposition studies, coupled atmospheric and fluvial Hg fluxes, and a comparison of this work with previous measurements indicate that Lake Ontario is a net sink of Hg inputs and not at steady state likely because of recent decreases in point source inputs and atmospheric Hg deposition. PMID:24783951

  20. A Field Exercise in Fluvial Sediment Transport.

    ERIC Educational Resources Information Center

    Tharp, Thomas M.

    1983-01-01

    Describes an investigation which introduces the mathematical principles of stream hydraulics and fluvial sediment in a practical context. The investigation has four stages: defining hydrology of the stream; defining channel hydraulics in a study reach; measuring grain size; and calculating transportable grain size and comparing measure stream-bed…

  1. Fluvial architecture and reservoir compartmentalization in the Oligocene middle Frio Formation of south Texas

    SciTech Connect

    Kerr, D.R.; Jirik, L.A. )

    1990-09-01

    Seeligson, Stratton, and Agua Dulce fields are being studied as part of a Gas Research Institute/Department of Energy/State of Texas cosponsored program designed to develop and test methodologies and technologies for gas reserve growth in conventional reservoirs in mature gas fields. Over the last four decades, each field has produced approximately 2 tcf of gas from middle Frio reservoirs alone. Recent drilling and workover results and reservoir pressure data, however, point to the possibility of additional reserves. Stratigraphic and sedimentologic studies based on well logs and cores indicate that middle Frio reservoirs are architecturally complex. Deposition on an aggrading coastal plain resulted in a continuum of architectural styles that has important implications for reservoir compartmentalization. The middle Frio is composed of sand-rich channel-fill and splay deposits interstratified with floodplain mudstones, all forming part of the Gueydan fluvial system. Relatively slow aggradation resulted in laterally stacked channel systems; whereas more rapid aggradation resulted in vertically stacked channel systems. Laterally stacked sandstone bodies predominate at Seeligson field, leading to separate but potentially leaky reservoir compartments. By contrast, vertically stacked sandstone bodies predominate at Stratton and Agua Dulce fields, favoring more isolated reservoir compartments. Thus, a high potential for reserve growth through the identification of untapped compartments, poorly drained acreage, and bypassed zones exists for each of these fields, but differences in reservoir architecture must be taken into account as part of exploitation strategies.

  2. AGUA TIBIA PRIMITIVE AREA, CALIFORNIA.

    USGS Publications Warehouse

    Irwin, William P.; Thurber, Horace K.

    1984-01-01

    The Agua Tibia Primitive Area in southwestern California is underlain by igneous and metamorphic rocks that are siilar to those widely exposed throughout much of the Peninsular Ranges. To detect the presence of any concealed mineral deposits, samples of stream sediments were collected along the various creeks that head in the mountain. As an additional aid in evaluating the mineral potential, an aeromagnetic survey was made and interpreted. A search for records of past or existing mining claims within the primitive area was made but none was found. Evidence of deposits of metallic or nonmetallic minerals was not seen during the study.

  3. Martian Fluvial Conglomerates at Gale Crater

    NASA Astrophysics Data System (ADS)

    Williams, R. M. E.; Grotzinger, J. P.; Dietrich, W. E.; Gupta, S.; Sumner, D. Y.; Wiens, R. C.; Mangold, N.; Malin, M. C.; Edgett, K. S.; Maurice, S.; Forni, O.; Gasnault, O.; Ollila, A.; Newsom, H. E.; Dromart, G.; Palucis, M. C.; Yingst, R. A.; Anderson, R. B.; Herkenhoff, K. E.; Le Mouélic, S.; Goetz, W.; Madsen, M. B.; Koefoed, A.; Jensen, J. K.; Bridges, J. C.; Schwenzer, S. P.; Lewis, K. W.; Stack, K. M.; Rubin, D.; Kah, L. C.; Bell, J. F.; Farmer, J. D.; Sullivan, R.; Van Beek, T.; Blaney, D. L.; Pariser, O.; Deen, R. G.; Kemppinen, Osku; Bridges, Nathan; Johnson, Jeffrey R.; Minitti, Michelle; Cremers, David; Edgar, Lauren; Godber, Austin; Wadhwa, Meenakshi; Wellington, Danika; McEwan, Ian; Newman, Claire; Richardson, Mark; Charpentier, Antoine; Peret, Laurent; King, Penelope; Blank, Jennifer; Weigle, Gerald; Schmidt, Mariek; Li, Shuai; Milliken, Ralph; Robertson, Kevin; Sun, Vivian; Baker, Michael; Edwards, Christopher; Ehlmann, Bethany; Farley, Kenneth; Griffes, Jennifer; Miller, Hayden; Newcombe, Megan; Pilorget, Cedric; Rice, Melissa; Siebach, Kirsten; Stolper, Edward; Brunet, Claude; Hipkin, Victoria; Léveillé, Richard; Marchand, Geneviève; Sobrón Sánchez, Pablo; Favot, Laurent; Cody, George; Steele, Andrew; Flückiger, Lorenzo; Lees, David; Nefian, Ara; Martin, Mildred; Gailhanou, Marc; Westall, Frances; Israël, Guy; Agard, Christophe; Baroukh, Julien; Donny, Christophe; Gaboriaud, Alain; Guillemot, Philippe; Lafaille, Vivian; Lorigny, Eric; Paillet, Alexis; Pérez, René; Saccoccio, Muriel; Yana, Charles; Aparicio, Carlos Armiens; Caride Rodríguez, Javier; Carrasco Blázquez, Isaías; Gómez Gómez, Felipe; Elvira, Javier Gómez; Hettrich, Sebastian; Lepinette Malvitte, Alain; Marín Jiménez, Mercedes; Frías, Jesús Martínez; Soler, Javier Martín; Torres, F. Javier Martín; Molina Jurado, Antonio; Sotomayor, Luis Mora; Muñoz Caro, Guillermo; Navarro López, Sara; González, Verónica Peinado; García, Jorge Pla; Rodriguez Manfredi, José Antonio; Planelló, Julio José Romeral; Alejandra Sans Fuentes, Sara; Sebastian Martinez, Eduardo; Torres Redondo, Josefina; O'Callaghan, Roser Urqui; Zorzano Mier, María-Paz; Chipera, Steve; Lacour, Jean-Luc; Mauchien, Patrick; Sirven, Jean-Baptiste; Manning, Heidi; Fairén, Alberto; Hayes, Alexander; Joseph, Jonathan; Squyres, Steven; Thomas, Peter; Dupont, Audrey; Lundberg, Angela; Melikechi, Noureddine; Mezzacappa, Alissa; DeMarines, Julia; Grinspoon, David; Reitz, Günther; Prats, Benito; Atlaskin, Evgeny; Genzer, Maria; Harri, Ari-Matti; Haukka, Harri; Kahanpää, Henrik; Kauhanen, Janne; Paton, Mark; Polkko, Jouni; Schmidt, Walter; Siili, Tero; Fabre, Cécile; Wray, James; Wilhelm, Mary Beth; Poitrasson, Franck; Patel, Kiran; Gorevan, Stephen; Indyk, Stephen; Paulsen, Gale; Bish, David; Schieber, Juergen; Gondet, Brigitte; Langevin, Yves; Geffroy, Claude; Baratoux, David; Berger, Gilles; Cros, Alain; Uston, Claude d.; Lasue, Jérémie; Lee, Qiu-Mei; Meslin, Pierre-Yves; Pallier, Etienne; Parot, Yann; Pinet, Patrick; Schröder, Susanne; Toplis, Mike; Lewin, Éric; Brunner, Will; Heydari, Ezat; Achilles, Cherie; Oehler, Dorothy; Sutter, Brad; Cabane, Michel; Coscia, David; Szopa, Cyril; Robert, François; Sautter, Violaine; Nachon, Marion; Buch, Arnaud; Stalport, Fabien; Coll, Patrice; François, Pascaline; Raulin, François; Teinturier, Samuel; Cameron, James; Clegg, Sam; Cousin, Agnès; DeLapp, Dorothea; Dingler, Robert; Jackson, Ryan Steele; Johnstone, Stephen; Lanza, Nina; Little, Cynthia; Nelson, Tony; Williams, Richard B.; Jones, Andrea; Kirkland, Laurel; Treiman, Allan; Baker, Burt; Cantor, Bruce; Caplinger, Michael; Davis, Scott; Duston, Brian; Fay, Donald; Hardgrove, Craig; Harker, David; Herrera, Paul; Jensen, Elsa; Kennedy, Megan R.; Krezoski, Gillian; Krysak, Daniel; Lipkaman, Leslie; McCartney, Elaina; McNair, Sean; Nixon, Brian; Posiolova, Liliya; Ravine, Michael; Salamon, Andrew; Saper, Lee; Stoiber, Kevin; Supulver, Kimberley; Van Beek, Jason; Zimdar, Robert; French, Katherine Louise; Iagnemma, Karl; Miller, Kristen; Summons, Roger; Goesmann, Fred; Hviid, Stubbe; Johnson, Micah; Lefavor, Matthew; Lyness, Eric; Breves, Elly; Dyar, M. Darby; Fassett, Caleb; Blake, David F.; Bristow, Thomas; DesMarais, David; Edwards, Laurence; Haberle, Robert; Hoehler, Tori; Hollingsworth, Jeff; Kahre, Melinda; Keely, Leslie; McKay, Christopher; Bleacher, Lora; Brinckerhoff, William; Choi, David; Conrad, Pamela; Dworkin, Jason P.; Eigenbrode, Jennifer; Floyd, Melissa; Freissinet, Caroline; Garvin, James; Glavin, Daniel; Harpold, Daniel; Mahaffy, Paul; Martin, David K.; McAdam, Amy; Pavlov, Alexander; Raaen, Eric; Smith, Michael D.; Stern, Jennifer; Tan, Florence; Trainer, Melissa; Meyer, Michael; Posner, Arik; Voytek, Mary; Anderson, Robert C.; Aubrey, Andrew; Beegle, Luther W.; Behar, Alberto; Brinza, David; Calef, Fred; Christensen, Lance; Crisp, Joy A.; DeFlores, Lauren; Feldman, Jason; Feldman, Sabrina; Flesch, Gregory; Hurowitz, Joel; Jun, Insoo; Keymeulen, Didier; Maki, Justin; Mischna, Michael; Morookian, John Michael; Parker, Timothy; Pavri, Betina; Schoppers, Marcel; Sengstacken, Aaron; Simmonds, John J.; Spanovich, Nicole; de la Torre Juarez, Manuel; Vasavada, Ashwin R.; Webster, Christopher R.; Yen, Albert; Archer, Paul Douglas; Cucinotta, Francis; Jones, John H.; Ming, Douglas; Morris, Richard V.; Niles, Paul; Rampe, Elizabeth; Nolan, Thomas; Fisk, Martin; Radziemski, Leon; Barraclough, Bruce; Bender, Steve; Berman, Daniel; Dobrea, Eldar Noe; Tokar, Robert; Vaniman, David; Leshin, Laurie; Cleghorn, Timothy; Huntress, Wesley; Manhès, Gérard; Hudgins, Judy; Olson, Timothy; Stewart, Noel; Sarrazin, Philippe; Grant, John; Vicenzi, Edward; Wilson, Sharon A.; Bullock, Mark; Ehresmann, Bent; Hamilton, Victoria; Hassler, Donald; Peterson, Joseph; Rafkin, Scot; Zeitlin, Cary; Fedosov, Fedor; Golovin, Dmitry; Karpushkina, Natalya; Kozyrev, Alexander; Litvak, Maxim; Malakhov, Alexey; Mitrofanov, Igor; Mokrousov, Maxim; Nikiforov, Sergey; Prokhorov, Vasily; Sanin, Anton; Tretyakov, Vladislav; Varenikov, Alexey; Vostrukhin, Andrey; Kuzmin, Ruslan; Clark, Benton; Wolff, Michael; McLennan, Scott; Botta, Oliver; Drake, Darrell; Bean, Keri; Lemmon, Mark; Lee, Ella Mae; Sucharski, Robert; Hernández, Miguel Ángel de Pablo; Blanco Ávalos, Juan José; Ramos, Miguel; Kim, Myung-Hee; Malespin, Charles; Plante, Ianik; Muller, Jan-Peter; González, Rafael Navarro; Ewing, Ryan; Boynton, William; Downs, Robert; Fitzgibbon, Mike; Harshman, Karl; Morrison, Shaunna; Kortmann, Onno; Williams, Amy; Lugmair, Günter; Wilson, Michael A.; Jakosky, Bruce; Zunic, Tonci Balic; Frydenvang, Jens; Kinch, Kjartan; Stipp, Susan Louise Svane; Boyd, Nick; Campbell, John L.; Gellert, Ralf; Perrett, Glynis; Pradler, Irina; VanBommel, Scott; Jacob, Samantha; Owen, Tobias; Rowland, Scott; Savijärvi, Hannu; Boehm, Eckart; Böttcher, Stephan; Burmeister, Sönke; Guo, Jingnan; Köhler, Jan; García, César Martín; Mellin, Reinhold Mueller; Schweingruber, Robert Wimmer; McConnochie, Timothy; Benna, Mehdi; Franz, Heather; Bower, Hannah; Brunner, Anna; Blau, Hannah; Boucher, Thomas; Carmosino, Marco; Atreya, Sushil; Elliott, Harvey; Halleaux, Douglas; Rennó, Nilton; Wong, Michael; Pepin, Robert; Elliott, Beverley; Spray, John; Thompson, Lucy; Gordon, Suzanne; Williams, Joshua; Vasconcelos, Paulo; Bentz, Jennifer; Nealson, Kenneth; Popa, Radu; Moersch, Jeffrey; Tate, Christopher; Day, Mackenzie; Kocurek, Gary; Hallet, Bernard; Sletten, Ronald; Francis, Raymond; McCullough, Emily; Cloutis, Ed; ten Kate, Inge Loes; Arvidson, Raymond; Fraeman, Abigail; Scholes, Daniel; Slavney, Susan; Stein, Thomas; Ward, Jennifer; Berger, Jeffrey; Moores, John E.

    2013-05-01

    Observations by the Mars Science Laboratory Mast Camera (Mastcam) in Gale crater reveal isolated outcrops of cemented pebbles (2 to 40 millimeters in diameter) and sand grains with textures typical of fluvial sedimentary conglomerates. Rounded pebbles in the conglomerates indicate substantial fluvial abrasion. ChemCam emission spectra at one outcrop show a predominantly feldspathic composition, consistent with minimal aqueous alteration of sediments. Sediment was mobilized in ancient water flows that likely exceeded the threshold conditions (depth 0.03 to 0.9 meter, average velocity 0.20 to 0.75 meter per second) required to transport the pebbles. Climate conditions at the time sediment was transported must have differed substantially from the cold, hyper-arid modern environment to permit aqueous flows across several kilometers.

  4. Martian fluvial conglomerates at Gale crater.

    PubMed

    Williams, R M E; Grotzinger, J P; Dietrich, W E; Gupta, S; Sumner, D Y; Wiens, R C; Mangold, N; Malin, M C; Edgett, K S; Maurice, S; Forni, O; Gasnault, O; Ollila, A; Newsom, H E; Dromart, G; Palucis, M C; Yingst, R A; Anderson, R B; Herkenhoff, K E; Le Mouélic, S; Goetz, W; Madsen, M B; Koefoed, A; Jensen, J K; Bridges, J C; Schwenzer, S P; Lewis, K W; Stack, K M; Rubin, D; Kah, L C; Bell, J F; Farmer, J D; Sullivan, R; Van Beek, T; Blaney, D L; Pariser, O; Deen, R G

    2013-05-31

    Observations by the Mars Science Laboratory Mast Camera (Mastcam) in Gale crater reveal isolated outcrops of cemented pebbles (2 to 40 millimeters in diameter) and sand grains with textures typical of fluvial sedimentary conglomerates. Rounded pebbles in the conglomerates indicate substantial fluvial abrasion. ChemCam emission spectra at one outcrop show a predominantly feldspathic composition, consistent with minimal aqueous alteration of sediments. Sediment was mobilized in ancient water flows that likely exceeded the threshold conditions (depth 0.03 to 0.9 meter, average velocity 0.20 to 0.75 meter per second) required to transport the pebbles. Climate conditions at the time sediment was transported must have differed substantially from the cold, hyper-arid modern environment to permit aqueous flows across several kilometers. PMID:23723230

  5. Martian fluvial conglomerates at Gale Crater

    USGS Publications Warehouse

    Williams, Rebecca M.E.; Grotzinger, J.P.; Dietrich, W.E.; Gupta, S.; Sumner, D.Y.; Wiens, R.C.; Mangold, N.; Malin, M.C.; Edgett, K.S.; Maurice, S.; Forni, O.; Gasnault, O.; Ollila, A.; Newsom, Horton E.; Dromart, G.; Palucis, M.C.; Yingst, R.A.; Anderson, Ryan B.; Herkenhoff, K. E.; Le Mouélic, S.; Goetz, W.; Madsen, M.B.; Koefoed, A.; Jensen, J.K.; Bridges, J.C.; Schwenzer, S.P.; Lewis, K.W.; Stack, K.M.; Rubin, D.; Kah, L.C.; Bell, J.F., III; Farmer, J.D.; Sullivan, R.; Van Beek, T.; Blaney, D.L.; Pariser, O.; Deen, R.G.

    2013-01-01

    Observations by the Mars Science Laboratory Mast Camera (Mastcam) in Gale crater reveal isolated outcrops of cemented pebbles (2 to 40 millimeters in diameter) and sand grains with textures typical of fluvial sedimentary conglomerates. Rounded pebbles in the conglomerates indicate substantial fluvial abrasion. ChemCam emission spectra at one outcrop show a predominantly feldspathic composition, consistent with minimal aqueous alteration of sediments. Sediment was mobilized in ancient water flows that likely exceeded the threshold conditions (depth 0.03 to 0.9 meter, average velocity 0.20 to 0.75 meter per second) required to transport the pebbles. Climate conditions at the time sediment was transported must have differed substantially from the cold, hyper-arid modern environment to permit aqueous flows across several kilometers.

  6. Riparian vegetation and fluvial geomorphic processes

    USGS Publications Warehouse

    Hupp, C.R.; Osterkamp, W.R.

    1996-01-01

    Riparian vegetation and fluvial-geomorphic processes and landforms are intimately connected parts of the bottomland landscape. Relations among vegetation, processes, and landforms are described here for representative streams of four areas of the United States: high-gradient streams of the humid east, coastal-plain streams. Great Plains streams, and stream channels of the southwestern United States. Vegetation patterns suggest that species distributions in the humid east are largely controlled by frequency, duration, and intensity of floods. Along channelized streams, vegetation distribution is largely controlled by variation in fluvial geomorphic processes (cycles of degradation and aggradation) in response to increases in channel gradient associated with channelization. Similarly, riparian vegetation of Great Plains streams may be controlled by fluxes in sediment deposition and erosion along braided streams. Patterns of riparian vegetation in semi-arid regions may be most closely related to patterns of water availability, unlike most other streams in more humid environments. Channel-equilibrium conditions control stability of the coincident fluvial landform and attendant vegetation pattern throughout the continent. In most situations, riparian-vegetation patterns are indicative of specific landforms and, thus, of ambient hydrogeomorphic conditions.

  7. Lowland fluvial phosphorus altered by dams

    NASA Astrophysics Data System (ADS)

    Zhou, Jianjun; Zhang, Man; Lin, Binliang; Lu, Pingyu

    2015-04-01

    Dams affect ecosystems, but their physical link to the variations in fluvial fluxes and downstream ecological consequences are inadequately understood. After estimating the current effects of the Three Gorges project and other reservoirs upstream on the Yangtze River on the fluvial phosphorus (P) in the middle and lower Yangtze River, we further investigated the long-term effects of dams on the fluvial regimes of P and P-enriched sediment (PES). Simultaneously measured P distributions with sediment size (PDSS) from the Three Gorges Reservoir (TGR) proved that the areal density of particulate P (PP) bound on graded sediment can be measured using the surface area concentration of the total sediment. A PDSS relationship is obtained and the selective transport and long-term sedimentation of P are simulated using a nonuniform suspended sediment model, which incorporates the PDSS formula. The computations revealed that a reservoir would significantly lower the downstream availability of P in the dry season and promote high pulses of P in summer when the reservoir is flushed as sedimentation accumulates. As a result, the P buffering and replenishing mechanism in the pristine ecosystem from upstream supplies and local re-suspension are permanently eliminated when a regulating reservoir is built upstream. This change is irreversible if reservoir regulation continues. Changes could potentially aggravate the existing P-limitation, decrease the water's ability to adjust nutrient/pollutant fluctuations, accumulate a greater surplus of carbon and nitrogen, and even exacerbate blooms in favorable conditions.

  8. Can anomalous diffusion describe depositional fluvial profiles?

    NASA Astrophysics Data System (ADS)

    Voller, V. R.; Paola, C.

    2010-06-01

    Diffusion models have been widely applied to describe fluvial long profiles. However, aggrading rivers simulated in laboratory experiments typically display much less profile curvature than a diffusion model would predict, whether aggradation is driven by subsidence or by base-level rise. Here we explore the possibility that this is due to nonclassical or non-Fickian, anomalous sediment transport in braided networks, which are known to have fractal planform geometry. We solve a fractional diffusion equation for a steady state aggrading fluvial profile for fractional exponents in the spatial derivative α in the range 1.1 < α + 1 < 2. The domain is bounded at both ends, and a constant sediment sink forces extraction of all of the imposed, constant sediment supply. We assume the fractional behavior is expressed solely by a nonlocal sediment flux term. Using the right-hand Caputo fractional derivative, we are able to construct a fractional diffusion equation that admits an analytical fluvial profile closely matching the laboratory-scale physical observations. We show that this solution is also in good agreement with a Monte Carlo simulation obtained using step lengths drawn from a Lévy probability density. However, despite the clear nonlocal behavior, we are unable to establish a direct physical link between the power law statistics of the fluvial transport system and the mathematical ingredients in a fractional diffusion model. In general, we expect the fractional behavior to be most pronounced when the length scale of significant downstream sediment extraction is comparable to the scale range of the fractal channel pattern behavior. This is typically the case for laboratory experiments but not at field scales, which could explain why anomalously flat fluvial long profiles have not been reported from the field. Applying fractional calculus to depositional river profiles, at any scale, exposes problems in applying fractional calculus posed by the bounded domain and the presence of a distributed sink associated with sediment extraction. With present understanding, the benefit of fractional calculus, which is its ability to capture effects of power law statistics in the underlying dynamics, comes at a significant cost in terms of flexibility to handle other physical effects such as complex domains, boundary conditions, and source terms.

  9. Reull Vallis fluvial system - Hypothesis for evolution

    NASA Astrophysics Data System (ADS)

    Kostama, V.-P.; Ivanov, M. A.; Polit, A. T.; Tormanen, T.; Grosfils, E.; Raitala, J.

    In this study we present a working hypothesis for the evolution of Reull Vallis fluvial system. We suggest that this system located in the eastern Hellas region consists of several parts, which are not necessarily contemporaneous, and could have formed independently. The existence of a possible paleolake or paleoreservoir between the Reull Vallis segments 1 and 2 as identified by [1] is also proposed as part of the system. We have analyzed and measured the different parts of the fluvial system, and correlated temporally the processes that have led to the formation of the system. Crater counting was used to derive relative ages, and to model roughly the absolute ages of different portions of the Reull Vallis system: (1) Morpheos subsystem, N(5) ˜200, early Hesperian; (2) Main Reull Vallis region, N(5) ˜120, late Hesperian. Also, the measurements from Viking MDIM and MGS MOLA were used to estimate volumes, discharge rates, and their balances for different parts of the system. Using the morphological and topographic indicators, the plausible volume for the proposed paleoreservoir (˜200 m deep) is ˜11-17 x 103 km3 . The Reull Vallis fluvial system appears to consist of at least five parts separable either by (1) morphology, or type of flow (sub/on-surface), or (2) by the temporal placement within the evolution of the fluvial system. The large scale development of the system appears to include three episodes: (1) Formation of the lower Reull (apparent beginning of it is the Teviot Vallis in ˜44°S, 258°W), (2) formation of the proposed "Morpheos" fluvial sub-system (including the segment 1 of Reull Vallis in [1]), and (3) formation of the upper Reull (segment 2 in [1]) that connected the Morpheos subsystem with the lower Reull Vallis. The episodes 1 and 2 may or may not be contemporaneous. This hypothesis explains (1) the missing connection between segments 1 and 2, (2) the relationship of the Teviot Vallis and Reull Vallis, and (3) the changes in topography and morphology. [1] Mest, S.C. and D.A. Crown, Icarus, 153, 2001.

  10. Fluvial landscapes of the Harappan civilization.

    PubMed

    Giosan, Liviu; Clift, Peter D; Macklin, Mark G; Fuller, Dorian Q; Constantinescu, Stefan; Durcan, Julie A; Stevens, Thomas; Duller, Geoff A T; Tabrez, Ali R; Gangal, Kavita; Adhikari, Ronojoy; Alizai, Anwar; Filip, Florin; VanLaningham, Sam; Syvitski, James P M

    2012-06-26

    The collapse of the Bronze Age Harappan, one of the earliest urban civilizations, remains an enigma. Urbanism flourished in the western region of the Indo-Gangetic Plain for approximately 600 y, but since approximately 3,900 y ago, the total settled area and settlement sizes declined, many sites were abandoned, and a significant shift in site numbers and density towards the east is recorded. We report morphologic and chronologic evidence indicating that fluvial landscapes in Harappan territory became remarkably stable during the late Holocene as aridification intensified in the region after approximately 5,000 BP. Upstream on the alluvial plain, the large Himalayan rivers in Punjab stopped incising, while downstream, sedimentation slowed on the distinctive mega-fluvial ridge, which the Indus built in Sindh. This fluvial quiescence suggests a gradual decrease in flood intensity that probably stimulated intensive agriculture initially and encouraged urbanization around 4,500 BP. However, further decline in monsoon precipitation led to conditions adverse to both inundation- and rain-based farming. Contrary to earlier assumptions that a large glacier-fed Himalayan river, identified by some with the mythical Sarasvati, watered the Harappan heartland on the interfluve between the Indus and Ganges basins, we show that only monsoonal-fed rivers were active there during the Holocene. As the monsoon weakened, monsoonal rivers gradually dried or became seasonal, affecting habitability along their courses. Hydroclimatic stress increased the vulnerability of agricultural production supporting Harappan urbanism, leading to settlement downsizing, diversification of crops, and a drastic increase in settlements in the moister monsoon regions of the upper Punjab, Haryana, and Uttar Pradesh. PMID:22645375

  11. Reconstructing Fluvial Morphology from Set Thickness Statistics

    NASA Astrophysics Data System (ADS)

    Kleinhans, M. G.; Van De Lageweg, W.; Van Dijk, W. M.

    2012-12-01

    Preservation is the link between fluvial surface morphodynamics and what is recorded in the fluvial sedimentary. Reconstruction of the original channel morphology from stratification can provide important information about paleoflow conditions. To infer the original dimensions of paleomorphological features such as river channels from the fluvial record, a detailed understanding of the relation between morphodynamics and preservation is needed. So far, theories to reconstruct the original morphology from preserved stratification have not been tested for meandering river channels for lack of detailed bathymetry. We report on a series of controlled flume experiments and Delft3D physics-based numerical model runs with the objectives to i) test the prediction of set thickness as a function of the morphology formed by a meandering river channel, and ii) explore and explain spatial and temporal set thickness variations in the resulting channel belt. High-resolution measurements of time-dependent surface elevation were used to quantitatively relate the preserved stratification to the river morphology. Experimental design corresponds to the predicted hydraulic geometry for a non-cohesive gravel-bed river, and the width-depth ratio is chosen such that alternate bars form. We find that the mean set thickness agrees well with the theoretical prediction from channel morphology. The mean preserved set thickness is 30% of the mean channel depth. Finally, there is much systematic spatial variation in set thickness related to repetitive point bar growth and chute cutoff. We find undisturbed and thick sets close to channel belt margins and more irregular stratification with stacked thinner sets in the channel belt center. We conclude that set thickness statistics can be used to provide quantitative error bounds for the reconstruction of paleochannel dimensions.

  12. Time and the rivers flowing: Fluvial geomorphology since 1960

    NASA Astrophysics Data System (ADS)

    Wohl, Ellen

    2014-07-01

    Fluvial geomorphology has been the largest single subdiscipline within geomorphology for many decades. Fluvial geomorphic expertise is integral to understanding and managing rivers and to developing strategies for sustainable development. This paper provides an overview of some of the significant advances in fluvial geomorphology between 1960 and 2010 with respect to: conceptual models; fluvial features and environments being studied; tools used by fluvial geomorphologists; geomorphic specialty groups within professional societies; journals in which fluvial geomorphic research is published; and textbooks of fluvial geomorphology. During this half century, fluvial geomorphology broadened considerably in scope, from a focus primarily on physical principles underlying process and form in lower gradient channels with limited grain size range, to a more integrative view of rivers as ecosystems with nonlinear behavior and great diversity of gradient, substrate composition, and grain size. The array of tools for making basic observations, analyzing data, and disseminating research results also expanded considerably during this period, as did the diversity of the fluvial geomorphic community.

  13. Meta-ecosystem metabolism across fluvial networks

    NASA Astrophysics Data System (ADS)

    Ulseth, A. J.; Singer, G. A.; Battin, T. J.

    2013-12-01

    Freshwater ecosystems store, transform, and export terrestrial carbon and play an important role for regional and global carbon fluxes. Ecosystem metabolism is a measure of how and how much carbon is produced and transformed and - for streams and rivers - is typically estimated at the reach scale (typically tens to hundreds of meters). Due to methodological constraints we so far lack an understanding of metabolism of the fluvial meta-ecosystem continuum, i.e. at the scale of a fluvial network. To address this issue, we measured metabolism in multiple reaches across a 254 km2 catchment in Lower Austria, capturing both temporal dynamics and the spatial scale of the whole fluvial network. Stream metabolism was estimated from diel changes in oxygen and corrected for reaeration; continuously in 15 streams and during a short-term ';snap-shot' campaign across 42 streams. Across the network, the streams varied in catchment size (0.1 to 254 km2) and water chemistry (DOC: 1.0 to 2.7 mg L-1, NO3: 259 to 1277 μg L-1, NH4:<0.1 to 30 μg L-1, and PO4:<0.1 to 20 μg L-1) as a consequence of subcatchment landuse, elevation and geology. Gross primary production (GPP) and ecosystem respiration (ER) were suppressed across the network by high stream discharge events such as snow melt and heavy rains. Larger streams (catchment size > 35 km2) had higher GPP and tended to be more autotrophic than lower order streams. However, streams located above 1000 m elevation had higher GPP than streams of equivalent size found elsewhere in the stream network. During the winter months, all streams across the network were net heterotrophic, with GPP typically <1.0 g 02 m-2 d-1. The degree of autotrophy versus heterotrophy across the network was driven in part by light, which is contingent on location within the stream network. We will discuss scaling GPP and ER from the reach to the network scale in order to elucidate patterns of meta-ecosystem metabolism across fluvial networks.

  14. Fluvial geomorphology and river engineering: future roles utilizing a fluvial hydrosystems framework

    NASA Astrophysics Data System (ADS)

    Gilvear, David J.

    1999-12-01

    River engineering is coming under increasing public scrutiny given failures to prevent flood hazards and economic and environmental concerns. This paper reviews the contribution that fluvial geomorphology can make in the future to river engineering. In particular, it highlights the need for fluvial geomorphology to be an integral part in engineering projects, that is, to be integral to the planning, implementation, and post-project appraisal stages of engineering projects. It should be proactive rather than reactive. Areas in which geomorphologists will increasingly be able to complement engineers in river management include risk and environmental impact assessment, floodplain planning, river audits, determination of instream flow needs, river restoration, and design of ecologically acceptable channels and structures. There are four key contributions that fluvial geomorphology can make to the engineering profession with regard to river and floodplain management: to promote recognition of lateral, vertical, and downstream connectivity in the fluvial system and the inter-relationships between river planform, profile, and cross-section; to stress the importance of understanding fluvial history and chronology over a range of time scales, and recognizing the significance of both palaeo and active landforms and deposits as indicators of levels of landscape stability; to highlight the sensitivity of geomorphic systems to environmental disturbances and change, especially when close to geomorphic thresholds, and the dynamics of the natural systems; and to demonstrate the importance of landforms and processes in controlling and defining fluvial biotopes and to thus promote ecologically acceptable engineering. Challenges facing fluvial geomorphology include: gaining full acceptance by the engineering profession; widespread utilization of new technologies including GPS, GIS, image analysis of satellite and airborne remote sensing data, computer-based hydraulic modeling and geophysical techniques; dovetailing engineering approaches to the study of river channels which emphasize reach-scale flow resistance, shear stresses, and material strength with catchment scale geomorphic approaches, empirical predictions, bed and bank processes, landform evolution, and magnitude-frequency concepts; producing accepted river channel typologies; fundamental research aimed at producing more reliable deterministic equations for prediction of bed and bank stability and bedload transport; and collaboration with aquatic biologists to determine the role and importance of geomorphologically and hydraulically defined habitats.

  15. Fluvial processes on Mars: Erosion and sedimentation

    NASA Technical Reports Server (NTRS)

    Squyres, Steven W.

    1988-01-01

    One of the most important discoveries of the Mariner 9 and Viking missions to Mars was evidence of change of the Martian surface by the action of liquid water. From the standpoint of a Mars Rover/Sample Return Mission, fluvial activity on Mars is important in two ways: (1) channel formation has deeply eroded the Martian crust, providing access to relatively undisturbed subsurface units; and (2) much of the material eroded from channels may have been deposited in standing bodies of liquid water. The most striking fluvial erosion features on Mars are the outflow channels. A second type of channel apparently caused by flow of liquid water is the valley systems. These are similar to terrestial drainage systems. The sedimentary deposits of outflow channels are often difficult to identfy. No obvious deposits such as deltaic accumulations are visible in Viking images. Another set of deposits that may be water lain and that date approx. from the epoch of outflow channels are the layered deposits in the Valles Marineris. From the standpoint of a Mars Rover/Sample Return mission, the problem with all of these water-lain sediments is their age, or rather the lack of it.

  16. Fluvial supraglacial landscape evolution on the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Karlstrom, Leif; Yang, Kang

    2016-03-01

    Supraglacial stream networks incise via thermal erosion of underlying ice, reflecting a balance between localized fluvial incision and dynamic topography from underlying ice flow. We analyze high-resolution digital elevation models of the ice surface and bedrock in the southwest Greenland Ice Sheet from 1000-1600 m elevation to quantify the importance of fluvial erosion. At wavelengths greater than ice thickness, bedrock dominates surface topography so supraglacial drainage basins are fixed spatially. At smaller wavelengths, fluvial erosion significantly affects topography. Stream longitudinal profiles exhibit positive mean curvature and consistent power law scaling between local channel slope and drainage area, suggestive of adjustment toward topographic steady state. We interpret these observations with a model for fluvial thermal erosion on top of a flowing ice substrate that predicts concave up steady state longitudinal profiles, where average concavity is most sensitive to melt rate and the relative magnitudes of ice flow and fluvial erosion.

  17. Predicting Facies Patterns within Fluvial Channel Belts

    NASA Astrophysics Data System (ADS)

    Willis, B. J.; Sech, R.; Sun, T.; Pyrcz, M.

    2014-12-01

    Reservoirs (aquifers) in fluvial channel belt sandstones can have very different subsurface flow behavior depending on the degree and distribution of internal heterogeneities. Fluvial channel belts are composed of multiple "storeys" formed as individual channel segments increase in sinuosity and then are cut off and abandoned. Heterogeneities are defined by depositional variations across storeys and inter-story connectivity patterns along the channel belt. Although commonly inferred to reflect the formative river pattern (sinuosity & braiding), the spatial arrangement of facies depend most directly on the relative preservation of deposits formed within different areas of the migrating channels and the lateral stacking arrangement of storeys due to style of bend cutoff. Grains are poorly sorted across the inner bank along upstream parts of channel bends and become better sorted laterally in downstream areas adjacent to a deeper thalweg scour. If deposition occurs evenly along the entire inner bank (bar), this grain size pattern leads to an elliptical body in planview with weak vertical grain size trends upstream and more fining-upward trend downstream. As channel bend segments migrate to a greater extent downstream, preserved inner-bank-bar deposits are increasingly dominated by upward-fining deposits and more outer-bank-deposits are preserved ("concave bank" deposits). Although concave bank deposits have highly variable character in different systems, vertical-grainsize trends tend to be weaker in straighter systems dominated by downstream-accretion, and more strongly upward-fining in higher sinuosity systems where these deposits form by eddy accretion or low flow aggradation. River cutoffs of straighter channel segments abandon slowly, leading to more gradual vertical fining. Subsurface heterogeneity prediction requires documentation of shape and character of deposits preserved in different zones within the channel (upstream and downstream inner bank, concave bank, thalweg scour lags, and abandonment fill). Systems with similar paleochannel pattern can leave deposits with very different subsurface heterogeneity arrangement.

  18. 72. Headgates for Agua Fria project canal on east end ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    72. Headgates for Agua Fria project canal on east end of diversion dam. Photographer Mark Durben. Source: Salt River Project. - Waddell Dam, On Agua Fria River, 35 miles northwest of Phoenix, Phoenix, Maricopa County, AZ

  19. 61. View of the Agua Fria River stream bed from ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    61. View of the Agua Fria River stream bed from atop Waddell Dam. Photographer Mark Durben. Source: Salt River Project. - Waddell Dam, On Agua Fria River, 35 miles northwest of Phoenix, Phoenix, Maricopa County, AZ

  20. 54. Downstream face of Agua Fria project's diversion dam showing ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    54. Downstream face of Agua Fria project's diversion dam showing initial masonry construction and poured concrete capping. Photographer Mark Durben, 1986. Source: Salt River Project. - Waddell Dam, On Agua Fria River, 35 miles northwest of Phoenix, Phoenix, Maricopa County, AZ

  1. 74. View of flume crossing the Agua Fria River from ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    74. View of flume crossing the Agua Fria River from the east embankment. Photographer Mark Durben. Source: Salt River Project. - Waddell Dam, On Agua Fria River, 35 miles northwest of Phoenix, Phoenix, Maricopa County, AZ

  2. Titan's Impact Craters and Associated Fluvial Features

    NASA Astrophysics Data System (ADS)

    Gilliam, A.; Jurdy, D. M.

    2012-12-01

    The Cassini spacecraft has detected remarkably few impact craters on the surface of Titan. By early 2010, with surface radar coverage reaching 33%, seven certain impact craters were discovered, with another 52 nearly certain and probable ones. The paucity of craters implies that the surface of Titan is very dynamic and relatively young. Dynamical models of the internal structure of Titan suggest the possibility of a subsurface ocean of ammonia-water liquid beneath its icy shell. If a large subsurface ocean does exist, it should have measurable effects on Titan's surface and the morphology of its craters. Using a combination of available Cassini radar-SAR, ISS, and VIMS data, we construct geomorphologic maps of Titan's "certain" impact craters with associated features we interpret as fluvial in origin. The best example, Menrva, a 445 km wide double-ring impact basin, hosts a complex network of channels. On the western, more degraded side of the crater, channels cut through the outer rim. To the east of Menrva, a curious network of channels start near the rim crest and appear to have flowed away into a large catchment basin; the complex is termed Elivagar Flumina. Channels surrounding Menrva display a low order - a classification of stream segments based on the number of tributaries upstream - measuring one or two, occasionally up to three. This matches observations of two other confirmed impact craters with associated fluvial features. A halo of low-order channels encircles Selk, an 80 km diameter crater with a small central peak. Also, Ksa, a 30 km diameter crater with a bright central peak and radial ejecta, has a feature that appears to be a first order channel. These differ radically from the tree-shaped dendritic channels common on Titan, which are generally attributed to heavy rainfall. For example, the Xanadu region, as observed on the T13 swath, exhibits a very complex and dendritic network of channels, where the order of channels reaches six to seven. The extensive area covered by dendritic systems indicates an origin from rainfall, rather than seepage of subsurface liquids, which has a low stream order. Thus, we argue that the association of channels with Titan's largest craters may not be pluvial in origin, and instead may be the result of seepage or even record a flood initiated by a large impact.

  3. 7. Photocopy of map of the Agua Fria Valley and ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. Photocopy of map of the Agua Fria Valley and lands to be irrigated by the Agua Fria Water and Land Company. Photographer Mark Durben, 1987 Source: 'Map of the Agua Fria Valley and the Western Portion of the Salt River Valley Showing the System of Reservoirs and Canals of the Agua Fria Water and Land Company and the Land to be Irrigated Thereby 160,000 Acres of New Land to be Reclaimed in the Maricopa County, Arizona Territory,' (Brochure) Union Photo Engraving Company, c. 1895, Salt River Project Research Archives, Tempe, Arizona. - Waddell Dam, On Agua Fria River, 35 miles northwest of Phoenix, Phoenix, Maricopa County, AZ

  4. 2. William Beardsley standing along the Agua Fria River near ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. William Beardsley standing along the Agua Fria River near construction site of the Agua Fria project. Photographer James Dix Schuyler, 1903. Source: Schuyler, James D. 'Report on the Water Supply of the Agua Fria River, and the Storage Reservoir Project of the Agua Fria Water and Land Company For Irrigation in the Gila River Valley, Arizona,' (September 29, 1903). Arizona Historical Collection, Hayden Library, Arizona State University, Tempe, Arizona. (Typewritten.) - Waddell Dam, On Agua Fria River, 35 miles northwest of Phoenix, Phoenix, Maricopa County, AZ

  5. Linking fluvial bed sediment transport across scales

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Meerschaert, Mark M.; Packman, Aaron I.

    2012-10-01

    We present a new random walk model for bed load sediment transport that explains the scale-dependency generally observed in transport rates and captures the transient anomalous dispersion often seen in rivers. Particles alternate between mobile and resting phases, with a tempered stable probability distribution for both particle step length and resting time. Tempered fractional mobile-immobile differential equations model the ensemble average of particle dynamics. The model is tested against data from three sediment dispersion experiments. Using tempering in both space and time, the new model is able to capture the full range of observed ensemble particle dynamics. The random walk model illuminates the physical meaning of all transport parameters in the mobile-immobile equations and explains transitions between observed super-diffusive, sub-diffusive, and regular diffusive ensemble particle dynamics. By explicitly predicting the effects of spatial and temporal averaging on particle dynamics, this method can be used to link observations of fluvial sediment dynamics across scales. This approach is also generally applicable to a wide variety of geophysical and ecological dynamics, such as ecological dispersal, pathogen transmission in rivers, nutrient export from watersheds, and large-scale geomorphodynamics associated with infrequent phenomena such as avalanches and turbidity currents.

  6. Erosion of biofilm-bound fluvial sediments

    NASA Astrophysics Data System (ADS)

    Vignaga, Elisa; Sloan, David M.; Luo, Xiaoyu; Haynes, Heather; Phoenix, Vernon R.; Sloan, William T.

    2013-09-01

    The movement of fluvial sediment shapes our rivers. Understanding sediment entrainment has been a goal of hydraulic engineers for almost a century. Previous sediment entrainment models have been informed by laboratory experiments using grains that were free from biological material. In natural river settings, however, sediments are invariably covered by bacteria, often forming visible biofilms, which comprise diverse consortia of species housed in sticky extracellular polysaccharides. Here we report experiments in a laboratory flume with cyanobacteria grown over sediment. We show that the prevailing model, where grains roll over one another at some critical threshold in shear velocity, does not hold for biofilm-bound sediments. Instead, biostabilized sediment behaves more like an elastic membrane. Fluid flow produces oscillations in the membrane, which can become unstable. Beyond a particular threshold in velocity, the membrane fails catastrophically by ripping and clumps of biofilm-bound sediment become entrained. We use a mathematical model of an oscillating membrane in incompressible flow to show that unstable oscillations will occur over a wide range of elastic material properties at realistic river flow velocities. We find that the horizontal length scale over which oscillations occur is a controlling factor for incipient sediment entrainment of biostabilized sediments.

  7. Timescales of fluvial activity and intermittency in Milna Crater, Mars

    NASA Astrophysics Data System (ADS)

    Buhler, Peter B.; Fassett, Caleb I.; Head, James W.; Lamb, Michael P.

    2014-10-01

    Milna Crater, Mars (23.4S, 12.3W) exhibits signs of fluvial modification early in Mars history, including a large multi-lobed fan deposit cut by several sinuous valleys. We describe the past hydrologic conditions in Milna and the surrounding area, including a potential lake with a volume of 50 km3. We also introduce new methods (i) to calculate the timescale of sediment deposition by considering fluvial sediment input into the entire crater while accounting for non-fluvial input, and (ii) to place improved constraints on the channel dimensions through which sediment was delivered to Milna by comparing to the dimensions of inner channels found in valleys in the region surrounding Milna. By calculating the flux of fluid and sediment into the crater, we find that the crater cavity was flooded for at least months and that the time of active fluvial sediment transport without hiatus is on the order of decades to centuries, with a preferred timescale of centuries. We also calculate the total amount of water required to transport the volume of sediment we measure in Milna and conclude that impacts alone are likely insufficient to deliver enough water to Milna to allow the sedimentary fill we see. Combining the timescales of fluvial activity in the adjacent Paraná Valles with estimates for global Noachian erosion rates, we calculate an intermittency factor for fluvial activity of ∼0.01-0.1% during 105-106 yr near the Noachian-Hesperian boundary in the Paraná Valles region. These values are comparable to arid climates on Earth where the majority of fluvial sedimentary transport takes place during floods with multi-year to decadal recurrence intervals. Our calculations of intermittency help to quantitatively reconcile the divergent estimates of the short and long timescales of fluvial activity on Mars reported in the literature.

  8. Fluvial erosion on Mars: Implications for paleoclimatic change

    NASA Technical Reports Server (NTRS)

    Gulick, Virginia C.; Baker, Victor R.

    1993-01-01

    Fluvial erosion on Mars has been nonuniform in both time and space. Viking orbiter images reveal a variety of different aged terrains exhibiting widely different degrees of erosion. Based on our terrestrial analog studies, rates of fluvial erosion associated with the formation of many of the valleys on Mars is probably on the order of hundreds of meters per million years, while rates of erosion associated with the formation of the outflow channels probably ranged from tens to hundreds of meters in several weeks to months. However, estimated rates of erosion of the Martian surface at the Viking Lander sites are extremely low, on the order of 1 micron/yr or less. At most this would result in a meter of material removed per million years, and it is unlikely that such an erosion rate would be able to produce the degree of geomorphic work required to form the fluvial features present elsewhere on the surface. In addition, single terrain units are not eroded uniformly by fluvial processes. Instead fluvial valleys, particularly in the cratered highlands, typically are situated in clusters surrounded by vast expanses of uneroded surfaces of the same apparent lithologic, structural, and hydrological setting. Clearly throughout its geologic history, Mars has experienced a nonuniformity in erosion rates. By estimating the amount of fluvial erosion on dissected terrains and by studying the spatial distribution of those locations which have experienced above normal erosion rates, it should be possible to place further constraints on Mars' paleoclimatic history.

  9. Relative size of fluvial and glaciated valleys in central Idaho

    NASA Astrophysics Data System (ADS)

    Amerson, Byron E.; Montgomery, David R.; Meyer, Grant

    2008-01-01

    Quantitative comparisons of the morphometry of glaciated and fluvial valleys in central Idaho were used to investigate the differences in valley relief and width in otherwise similar geologic and geomorphic settings. The local relief, width, and cross-sectional area of valleys were measured using GIS software to extract information from USGS digital elevation models. Hillslope gradients were also measured using GIS software. Power-law relationships for local valley relief, width, and cross-sectional area as a function of drainage area were developed. Local valley relief in glaciated valleys relates to drainage area with a power-law exponent similar to fluvial valleys, but glaciated valleys are deeper for a given drainage area. Local valley width in glaciated valleys is greater than in fluvial valleys, but the exponent of the power-law relationship to drainage area is similar in both valley types. Local valley cross-sectional area in glaciated valleys increases with drainage area with a power-law exponent similar to fluvial valleys, however, glacial valleys have roughly 80% greater cross-sectional area. Steep valley walls in glaciated basins increase the potential for bedrock landsliding relative to fluvial basins. Both the Olympic Mountains of Washington and valleys in central Idaho show relationships in which glaciated valleys are up to 30% deeper than fluvial valleys despite differences in lithology, tectonic setting, and climate.

  10. Reconstructing Holocene fluvial activity in Ireland using alluvial radiocarbon dates

    NASA Astrophysics Data System (ADS)

    Turner, Jonathan; Macklin, Mark; Jones, Anna

    2010-05-01

    Advances in fluvial geochronologies and multi-proxy environmental correlatives are providing increasingly robust models of river response to Holocene environmental change. At the forefront of recent scientific progress is the development and analysis of databases of fluvial radiocarbon dates, where particular emphasis is given to terminus post quem (‘change after') radiocarbon dates that mark the onset of alluviation linked to episodes of enhanced flooding. Here we report on the first attempt to apply these meta-analysis techniques to dated fluvial deposits in Ireland, which offer tremendous potential for recording climate changes associated with shifts in meridional atmospheric circulation, largely free from the effects of continentality in the east. The resulting Irish fluvial radiocarbon database is considerably smaller than examples from other European countries, such as Germany, Poland, Spain and the UK, and a patchy geographical distribution of dated sites across Ireland highlights the relative dearth of Irish fluvial research up to now. Despite a comparatively small number of significant ‘change after' radiocarbon dates, however, the application of generic meta-analysis techniques reveals a pattern of Holocene flooding that is consistent with widely cited palaeoclimate proxies for regional temperature and precipitation. The Irish flood record also closely matches that derived from an established and much larger UK radiocarbon database, thereby corroborating the growing body of evidence that supports an underlying climate forcing of fluvial activity during much of the Holocene. Fluvial systems in Ireland are shown to be sensitive to climate, but the majority of major radiocarbon-dated flooding episodes appear to lag the UK by ca. 100 years. Although this may be the result of database precision, we suggest that the hydrological buffering and sponge effects of widespread peatland cover across Ireland may have impeded hydrological connectivity during Holocene flooding episodes. In addition, this investigation reveals systematically lower sedimentation rates across Ireland compared to the UK, which may have reduced the geomorphic effectiveness of fluvial sediment archives to record major flood events. These considerations, together with an increasing focus on regional variations in fluvial activity across the Holocene, can only be properly addressed with a more concerted and expanded programme of Holocene fluvial research in Ireland.

  11. Modelling Fluvial Sediment Budgets Under Uncertainty

    NASA Astrophysics Data System (ADS)

    Brasington, J.; Wheaton, J. M.; Williams, R. D.

    2004-12-01

    The last decade has witnessed a resurgence of interest in morphological estimation of fluvial sediment budgets, facilitated by major advances in survey technology, including airborne lidar and photogrammetry and ground-based GPS. The reliability of such morphologically inferred budgets is controlled by: a) uncertainty in the flux boundary conditions; b) survey frequency; and c) DEM quality. A body of research has sought to identify the sensitivity of derived parameters to these controls and establish a methodological framework for data quality control and assurance. To date, most interest has focused on evaluating the uncertainty in budget estimates due to DEM errors. These arise as a largely unknown function of survey point quality, sampling strategy and interpolation methods. A commonly adopted procedure for managing these uncertainties involves specifying a minimum level of detection threshold (LOD) to distinguish actual surface changes from inherent noise. Determining the LOD requires both a theory of change detection and a metric of DEM quality. Typically this is achieved by applying the classical statistical theory of errors and a measure of DEM precision derived from check data or point precision estimates. Research presented here aims to demonstrate that simple thresholding of DEMs of difference may, however, significantly underestimate the information that can be optimally retrieved through DEM differencing. Analyses are based on a series of annual surveys of the River Feshie in the Scottish Highlands using high-quality rtkGPS and lower precision airborne photogrammetric data. A new methodology for change detection is presented which incorporates: (i) a stepwise analysis of errors arising during DEM construction; (ii) the development of a spatial filter to group areas of scour and fill; and (iii) alternative methods for analysing change data which relax the assumptions of the LOD approach. These latter strategies explicitly incorporate uncertainties in DEM data and permit sediment budget calculations to be presented in a stochastic framework. The results suggest that enhanced data retrievals are possible and have the potential to recast the geomorphic interpretation of process rates.

  12. Distributive Fluvial Systems of the Chaco Plain - Satellite Image Assessment of Fluvial Form and Facies Distributions

    NASA Astrophysics Data System (ADS)

    Weissmann, G. S.; Hartley, A. J.; Scuderi, L.; Bhattacharyya, P.; Buehler, H.; Leleu, S.; Mather, A.

    2009-12-01

    Distributive fluvial systems (DFS) dominate fluvial deposition inside modern continental sedimentary basins and are particularly extensive in modern foreland basins. The largest of these DFS are found in the Chaco Plain, Andean Foreland Basin, South America. We use published literature, field and satellite data (Landsat, Modis, and SRTM) to construct preliminary hypotheses about the geomorphic form and fluvial facies distributions on the DFSs in this basin. The Pilcomayo River DFS extends over 700 km from apex to toe. The river enters the DFS apex as a large braided river with a bankfull channel width of 2500 m. Gravels and cobbles occur in terraces cut through the apex. At ~70-km downstream the bankfull channel width is ~2000 m and the channel is dominated by fine sand with cut banks 2-3 m high. The proximal channel belt is surrounded by floodplain sediments, however many sandy abandoned channel belts are present across the DFS, indicating a mobile channel system. Abandoned channels have a similar form to the modern channel, with minor reworking by underfit meandering streams. At ~75-km downfan, the river system diminishes in size (bankfull channel width up to 2 km but generally <1.5 km) and becomes increasingly sinuous in planform. This point appears to serve as a node for a series of recently abandoned meander belts and splays associated with discrete channels surrounded by floodplain material. At 100 km downstream the planform is highly sinuous and bankfull width has decreased to 1500 m or less. Downstream of this area abandoned meander belts dominate along the flanks of the modern channel with oxbow lakes present adjacent to the active channel. At 150 km downstream the bankfull channel belt width is 500 m or less and the river bifurcates into splays and multiple active channels which extend downstream for a further 200 km. Vegetation maps derived from Modis imagery indicate an increase in tree density around the DFS at this elevation (230 m). Along the distal portion of the DFS, a springline at ~150 m elevation separates the upper, well drained, aridisol dominated dry Chaco area of the DFS from the poorly drained wet Chaco at the toe. Channels below this line remain wet, are mud-dominated, and associated soils are hydromorphic. At the termination of the DFS the main Pilcomayo channel has a bankfull width of 120 m with sediments consisting of interbedded fine sand and mudstone. The observations from the Pilcomayo can serve as important analogues for the development of DFS in ancient foreland basin successions, particularly the recognition of the radial distribution of distinct facies types and the downstream changes in soil types associated with the spring line.

  13. Global effects of agriculture on fluvial dissolved organic matter.

    PubMed

    Graeber, Daniel; Boëchat, Iola G; Encina-Montoya, Francisco; Esse, Carlos; Gelbrecht, Jörg; Goyenola, Guillermo; Gücker, Björn; Heinz, Marlen; Kronvang, Brian; Meerhoff, Mariana; Nimptsch, Jorge; Pusch, Martin T; Silva, Ricky C S; von Schiller, Daniel; Zwirnmann, Elke

    2015-01-01

    Agricultural land covers approximately 40% of Earth's land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, agriculture also strongly affects the amount and molecular composition of dissolved organic matter (DOM), which constitutes the main vector of carbon transport from soils to fluvial networks and to the sea, and is involved in a large variety of biogeochemical processes. Here, we provide first evidence about the wider occurrence of agricultural impacts on the concentration and composition of fluvial DOM across climate zones of the northern and southern hemispheres. Both extensive and intensive farming altered fluvial DOM towards a more microbial and less plant-derived composition. Moreover, intensive farming significantly increased dissolved organic nitrogen (DON) concentrations. The DOM composition change and DON concentration increase differed among climate zones and could be related to the intensity of current and historical nitrogen fertilizer use. As a result of agriculture intensification, increased DON concentrations and a more microbial-like DOM composition likely will enhance the reactivity of catchment DOM emissions, thereby fuelling the biogeochemical processing in fluvial networks, and resulting in higher ecosystem productivity and CO2 outgassing. PMID:26541809

  14. Global effects of agriculture on fluvial dissolved organic matter

    PubMed Central

    Graeber, Daniel; Boëchat, Iola G.; Encina-Montoya, Francisco; Esse, Carlos; Gelbrecht, Jörg; Goyenola, Guillermo; Gücker, Björn; Heinz, Marlen; Kronvang, Brian; Meerhoff, Mariana; Nimptsch, Jorge; Pusch, Martin T.; Silva, Ricky C. S.; von Schiller, Daniel; Zwirnmann, Elke

    2015-01-01

    Agricultural land covers approximately 40% of Earth’s land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, agriculture also strongly affects the amount and molecular composition of dissolved organic matter (DOM), which constitutes the main vector of carbon transport from soils to fluvial networks and to the sea, and is involved in a large variety of biogeochemical processes. Here, we provide first evidence about the wider occurrence of agricultural impacts on the concentration and composition of fluvial DOM across climate zones of the northern and southern hemispheres. Both extensive and intensive farming altered fluvial DOM towards a more microbial and less plant-derived composition. Moreover, intensive farming significantly increased dissolved organic nitrogen (DON) concentrations. The DOM composition change and DON concentration increase differed among climate zones and could be related to the intensity of current and historical nitrogen fertilizer use. As a result of agriculture intensification, increased DON concentrations and a more microbial-like DOM composition likely will enhance the reactivity of catchment DOM emissions, thereby fuelling the biogeochemical processing in fluvial networks, and resulting in higher ecosystem productivity and CO2 outgassing. PMID:26541809

  15. Global effects of agriculture on fluvial dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Graeber, Daniel; Boëchat, Iola G.; Encina-Montoya, Francisco; Esse, Carlos; Gelbrecht, Jörg; Goyenola, Guillermo; Gücker, Björn; Heinz, Marlen; Kronvang, Brian; Meerhoff, Mariana; Nimptsch, Jorge; Pusch, Martin T.; Silva, Ricky C. S.; von Schiller, Daniel; Zwirnmann, Elke

    2015-11-01

    Agricultural land covers approximately 40% of Earth’s land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, agriculture also strongly affects the amount and molecular composition of dissolved organic matter (DOM), which constitutes the main vector of carbon transport from soils to fluvial networks and to the sea, and is involved in a large variety of biogeochemical processes. Here, we provide first evidence about the wider occurrence of agricultural impacts on the concentration and composition of fluvial DOM across climate zones of the northern and southern hemispheres. Both extensive and intensive farming altered fluvial DOM towards a more microbial and less plant-derived composition. Moreover, intensive farming significantly increased dissolved organic nitrogen (DON) concentrations. The DOM composition change and DON concentration increase differed among climate zones and could be related to the intensity of current and historical nitrogen fertilizer use. As a result of agriculture intensification, increased DON concentrations and a more microbial-like DOM composition likely will enhance the reactivity of catchment DOM emissions, thereby fuelling the biogeochemical processing in fluvial networks, and resulting in higher ecosystem productivity and CO2 outgassing.

  16. Fluvial erosion as a mechanism for crater modification on Titan

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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.

  17. Fluvial network organization imprints on microbial co-occurrence networks

    PubMed Central

    Widder, Stefanie; Besemer, Katharina; Singer, Gabriel A.; Ceola, Serena; Bertuzzo, Enrico; Quince, Christopher; Sloan, William T.; Rinaldo, Andrea; Battin, Tom J.

    2014-01-01

    Recent studies highlight linkages among the architecture of ecological networks, their persistence facing environmental disturbance, and the related patterns of biodiversity. A hitherto unresolved question is whether the structure of the landscape inhabited by organisms leaves an imprint on their ecological networks. We analyzed, based on pyrosequencing profiling of the biofilm communities in 114 streams, how features inherent to fluvial networks affect the co-occurrence networks that the microorganisms form in these biofilms. Our findings suggest that hydrology and metacommunity dynamics, both changing predictably across fluvial networks, affect the fragmentation of the microbial co-occurrence networks throughout the fluvial network. The loss of taxa from co-occurrence networks demonstrates that the removal of gatekeepers disproportionately contributed to network fragmentation, which has potential implications for the functions biofilms fulfill in stream ecosystems. Our findings are critical because of increased anthropogenic pressures deteriorating stream ecosystem integrity and biodiversity. PMID:25136087

  18. Fluvial network organization imprints on microbial co-occurrence networks.

    PubMed

    Widder, Stefanie; Besemer, Katharina; Singer, Gabriel A; Ceola, Serena; Bertuzzo, Enrico; Quince, Christopher; Sloan, William T; Rinaldo, Andrea; Battin, Tom J

    2014-09-01

    Recent studies highlight linkages among the architecture of ecological networks, their persistence facing environmental disturbance, and the related patterns of biodiversity. A hitherto unresolved question is whether the structure of the landscape inhabited by organisms leaves an imprint on their ecological networks. We analyzed, based on pyrosequencing profiling of the biofilm communities in 114 streams, how features inherent to fluvial networks affect the co-occurrence networks that the microorganisms form in these biofilms. Our findings suggest that hydrology and metacommunity dynamics, both changing predictably across fluvial networks, affect the fragmentation of the microbial co-occurrence networks throughout the fluvial network. The loss of taxa from co-occurrence networks demonstrates that the removal of gatekeepers disproportionately contributed to network fragmentation, which has potential implications for the functions biofilms fulfill in stream ecosystems. Our findings are critical because of increased anthropogenic pressures deteriorating stream ecosystem integrity and biodiversity. PMID:25136087

  19. Fluvial to Lacustrine Facies Transitions in Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Sumner, Dawn Y.; Williams, Rebecca M. E.; Schieber, Juergen; Palucis, Marisa C.; Oehler, Dorothy Z.; Mangold, Nicolas; Kah, Linda C.; Gupta, Sanjeev; Grotzinger, John P.; Grant, John A., III; Edgar, Lauren A.; Dietrich, William E.

    2015-01-01

    NASA's Curiosity rover has documented predominantly fluvial sedimentary rocks along its path from the landing site to the toe of the Peace Vallis alluvial fan (0.5 km to the east) and then along its 8 km traverse across Aeolis Palus to the base of Aeolis Mons (Mount Sharp). Lacustrine facies have been identified at the toe of the Peace Vallis fan and in the lowermost geological unit exposed on Aeolis Mons. These two depositional systems provide end members for martian fluvial/alluvial-lacustrine facies models. The Peace Vallis system consisted of an 80 square kilometers alluvial fan with decimeter-thick, laterally continuous fluvial sandstones with few sedimentary structures. The thin lacustrine unit associated with the fan is interpreted as deposited in a small lake associated with fan runoff. In contrast, fluvial facies exposed over most of Curiosity's traverse to Aeolis Mons consist of sandstones with common dune-scale cross stratification (including trough cross stratification), interbedded conglomerates, and rare paleochannels. Along the southwest portion of the traverse, sandstone facies include south-dipping meter-scale clinoforms that are interbedded with finer-grained mudstone facies, interpreted as lacustrine. Sedimentary structures in these deposits are consistent with deltaic deposits. Deltaic deposition is also suggested by the scale of fluvial to lacustrine facies transitions, which occur over greater than 100 m laterally and greater than 10 m vertically. The large scale of the transitions and the predicted thickness of lacustrine deposits based on orbital mapping require deposition in a substantial river-lake system over an extended interval of time. Thus, the lowermost, and oldest, sedimentary rocks in Gale Crater suggest the presence of substantial fluvial flow into a long-lived lake. In contrast, the Peace Vallis alluvial fan onlaps these older deposits and overlies a major unconformity. It is one of the youngest deposits in the crater, and requires only short-lived, transient flows.

  20. Progressive Poleward Migration of Fluvial Processes on Titan

    NASA Astrophysics Data System (ADS)

    Moore, Jeffrey M.; Howard, A. D.

    2012-04-01

    Titan may have acquired its massive atmosphere relatively recently in solar system history. The warming sun may have been key to generating Titans 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 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 mid-latitude regions on Titan exhibit dissected sedimentary plains at a number of localities, suggesting deposition (perhaps by sediment eroded from equatorial regions) followed by erosion. These dissected plains may be evidence for the poleward retreat of rain 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. Figure 1. High mid-latitude region exhibiting a partially-dissected surface (Dissected Plateau). The dissection is interpreted to be fluvial due to dendritic valleys draining southward. The undissected surface to the left Upper Plain may be alluvial lowlands or an undissected part of the plateau bordering it to the right. The smooth radar-dark surface in center right is suggested to be Alluvial Lowlands because it is crossed by several broad, sinuous valleys or channels (arrow). Portion of swath T39, ~50S, 210W.

  1. River Self-Restoration: Interactions between Plants and Fluvial Processes

    NASA Astrophysics Data System (ADS)

    Gurnell, Angela

    2014-05-01

    This paper presents evidence from European rivers of the nature and consequences of plant-fluvial process interactions. While the examples are representative of different climates, riparian and aquatic plant species, and river geomorphological types, they are linked by a general conceptual model of plant-fluvial process interactions that can be adapted to local conditions. Riparian and aquatic plants both affect and respond to fluvial processes. Their above ground biomass modifies the flow field and retains sediment, whereas their below-ground biomass affects the hydraulic and mechanical properties of the substrate and consequently the moisture regime and erodibility of the land surface. At the same time plants are disturbed, removed and buried by fluvial processes. Thus the margins of river systems provide a critical zone where plants and fluvial processes interact to produce a diverse mosaic of dynamic landforms that are characteristic of naturally-functioning river ecosystems. It is important to understand these interactions between aquatic and riparian plants and fluvial processes, and to recognize how they contribute to trajectories of natural river channel recovery from human interventions. The interactions have a significant influence on river systems across space scales from individual plants to entire river corridors. Plant-scale phenomena structure patch-scale geomorphological forms and processes. Interactions between patches contribute to larger-scale and longer-term river geomorphological phenomena. Furthermore, the influence of plants varies through time as above and below ground biomass alter within the annual growth cycle, over longer-term growth trajectories, and in response to drivers of change such as climatic and hydrological fluctuations and extremes. If river management and restoration works with these natural interactions and recovery processes, outcomes have the best chance of being cost-effective and sustainable.

  2. Fluvial-deltaic sedimentation and stratigraphy of the ferron sandstone

    USGS Publications Warehouse

    Anderson, P.B.; Chidsey, T.C., Jr.; Ryer, T.A.

    1997-01-01

    East-central Utah has world-class outcrops of dominantly fluvial-deltaic Turonian to Coniacian aged strata deposited in the Cretaceous foreland basin. The Ferron Sandstone Member of the Mancos Shale records the influences of both tidal and wave energy on fluvial-dominated deltas on the western margin of the Cretaceous western interior seaway. Revisions of the stratigraphy are proposed for the Ferron Sandstone. Facies representing a variety of environments of deposition are well exposed, including delta-front, strandline, marginal marine, and coastal-plain. Some of these facies are described in detail for use in petroleum reservoir characterization and include permeability structure.

  3. Evidence from Fluvial Deposits for Changes in Water Surface Levels of a Sea or Large Lake at Aeolis Dorsa, Mars

    NASA Astrophysics Data System (ADS)

    Cardenas, B. T.; Mohrig, D.

    2014-07-01

    Fluvial deposits at Aeolis Dorsa are arranged in a stratigraphic sequence common to the fluvial fill of incised valleys on Earth. On Earth, this type of fluvial stratigraphy is a common response to ocean level falls and rises.

  4. Mid-late Holocene environments of Agua Buena locality (34°50'S 69°56'W), Mendoza, Argentina

    NASA Astrophysics Data System (ADS)

    Navarro, Diego; Mehl, A.; Zarate, M. A.; Paez, M. M.

    2010-03-01

    In southern South America the acquisition of high-quality Holocene paleoclimate data is a priority due to the paucity of complete, continuous and well dated records. Here we report preliminary results from a combined sedimentological and palynological study of an alluvial fan sequence and the laterally connected sedimentary deposits of the Vega de la Cueva profile at Agua Buena east of the Andes in central Argentina. The main geomorphological units of the area were identified and mapped based on satellite image analysis and multiple field surveys. The sedimentological and pollen results allowed us to reconstruct the development of some environments. The Agua Buena record corresponds to the distal facies of the Arroyo Bayo alluvial fan starting the aggradation process prior to ca. 4100 cal yr BP. The organic-rich levels found were formed during the development of wetlands (vegas) dominated by Cyperaceae, Juncaceae and Poaceae. These highly productive environments with almost permanent water saturation were important between 4100 and 2800 cal yr BP, indicating more stable conditions. After 2800 cal yr BP, the organic content was comparatively lower with increasing sedimentation rates that are indicative of higher fluvial discharges. This information is fundamental to interpret both the pollen and charcoal records of the area and to evaluate their representativeness and potential to reconstruct past local and/or regional vegetation.

  5. Architectural studies of Jurassic-Cretaceous fluvial units, Colorado Plateau

    SciTech Connect

    Miall, A.D.; Bromley, M.H.; Cowan, E.J.; Turner-Peterson, C.E.

    1989-03-01

    A sixfold hierarchy of architectural elements and bounding surfaces evolved from outcrop studies of three fluvial units: Westwater Canyon member (WCM), Morrison Formation, Upper Jurassic; Torrivio sandstone member (TSM), Gallup Sandstone, Upper Cretaceous, northwestern New Mexico; and Kayenta Formation (KF), Lower Jurassic, southwestern Colorado. This hierarchy is discussed.

  6. Bank stability analysis for fluvial erosion and mass failure

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The central objective of this study was to highlight the differences in magnitude between mechanical and fluvial streambank erosional strength with the purpose of developing a more comprehensive bank stability analysis. Mechanical erosion and ultimately failure signifies the general movement or coll...

  7. The Australian Paleoflood Model for Unconfined Fluvial Deposition on Mars

    NASA Technical Reports Server (NTRS)

    Bourke, M. C.; Zimbelman, J. R.

    2001-01-01

    Paleoflood deposits in central Australia represent a new model for possible fluvial deposits on Mars. The distinct Australian assemblage of landforms and sediments is used to identify potential unconfined paleoflood deposits in Mars Orbiter Camera (MOC) images of Mars. Additional information is contained in the original extended abstract.

  8. Fluvial network imprints on microbial diversity and community network topology

    NASA Astrophysics Data System (ADS)

    Battin, T. J.; Besemer, K.; Widder, S.; Singer, G. A.; Ceola, S.; Bertuzzo, E.; Quince, C.; Sloan, W. T.; Rinaldo, A.

    2013-12-01

    Streams and rivers sculpt continental landscapes and the networks they form carry universal signatures of spatial organization. Biodiversity in fluvial networks ranks among the highest on Earth and microorganisms therein, often enclosed in biofilms, fulfill critical ecosystem functions even with repercussions on the global carbon cycle. We extensively used 454 pyrosequencing on biofilm samples from more than 100 streams from a 5th-order catchment, derived alpha and beta diversity patterns and, using co-occurrence analyses, we studied community network organization. Contrary to current theory and to animal diversity studies, we found microbial alpha diversity in biofilms to decrease downstream with confluences likely acting as filters to biodiversity as it propagates from the smallest headwaters to larger rivers. Along with higher beta diversity in the headwaters, these findings highlight headwaters as critical reservoirs of microbial diversity for entire fluvial networks. Co-occurrence analyses revealed a lower level of fragmentation of community networks in headwaters than in larger rivers downstream and further identified gatekeepers (at family level) as potential architects of the observed network topology. Similarly, fragmentation was higher downstream than upstream of confluences. Consistent with current network theory, simple model simulations suggest that fragmentation patterns are linked to persistence against perturbations. We further explore the role of perturbation for community network topology in the context of fluvial network hydrology. Our findings have deep implications for restoration and conservation. They portrait the imprint of fluvial networks on microbial community networks and thereby expand our knowledge on biodiversity and ecosystem persistence.

  9. A classification scheme for fluvial-aeolian system interaction in desert-margin settings

    NASA Astrophysics Data System (ADS)

    Al-Masrahy, Mohammed A.; Mountney, Nigel P.

    2015-06-01

    This study examines 130 case examples from 60 desert regions to propose a generalised framework to account for the diverse types of interaction known to exist between active aeolian and fluvial depositional systems at modern dune-field margins. Results demonstrate the significance of aeolian and fluvial system type, orientation of aeolian versus fluvial landforms, distribution of open versus closed interdune corridors, and fluvial flow processes in controlling the distance and type of penetration of fluvial systems into aeolian dune fields. Ten distinct types of fluvial-aeolian interaction are recognised: fluvial incursions aligned parallel to trend of linear chains of aeolian dune forms; fluvial incursions oriented perpendicular trend of aeolian dunes; bifurcation of fluvial flow between isolated aeolian dune forms; through-going fluvial channel networks that cross entire aeolian dune fields; flooding of dune fields due to regionally elevated water-table levels associated with fluvial floods; fluvial incursions emanating from a single point source into dune fields; incursions emanating from multiple sheet sources; cessation of the encroachment of entire aeolian dune fields by fluvial systems; termination of fluvial channel networks in aeolian dune fields; long-lived versus short-lived modes of fluvial incursion. Quantitative relationships describing spatial rates of change of desert-margin landforms are presented. The physical boundaries between geomorphic systems are dynamic: assemblages of surface landforms may change gradationally or abruptly over short spatial and temporal scales. Generalised models for the classification of types of interaction have application to the interpretation of ancient preserved successions, especially those known only from the subsurface.

  10. The Agua Salud Project, Central Panama

    NASA Astrophysics Data System (ADS)

    Stallard, R. F.; Elsenbeer, H.; Ogden, F. L.; Hall, J. S.

    2007-12-01

    The Agua Salud Project utilizes the Panama Canal's central role in world commerce to focus global attention on the ecosystem services provided by tropical forests. It will be the largest field experiment of its kind in the tropics aimed at quantifying the environmental services (water, carbon, and biodiversity) provided by tropical forests. The Agua Salud Watershed is our principal field site. This watershed and the headwaters of several adjacent rivers include both protected mature forests and a wide variety of land uses that are typical of rural Panama. Experiments at the scale of entire catchments will permit complete water and carbon inventories and exchanges for different landscape uses. The following questions will be addressed: (1) How do landscape treatments and management approaches affect ecosystem services such as carbon storage, water quality and quantity, dry- season water supply, and biodiversity? (2) Can management techniques be designed to optimize forest production along with ecosystem services during reforestation? (3) Do different tree planting treatments and landscape management approaches influence groundwater storage, which is thought to be critical to maintaining dry-season flow, thus insuring the full operation of the Canal during periods of reduced rainfall and severe climatic events such as El Niño. In addition we anticipate expanding this project to address biodiversity, social, and economic values of these forests.

  11. From archive to process in past fluvial systems

    NASA Astrophysics Data System (ADS)

    Dikau, R.

    2009-04-01

    The reconstruction of sediment fluxes through palaeo ecological systems is based on effect (sediment record) - cause (soil erosion, fluvial transport, sediment deposition) relationships using abduction as central methodology. In philosophy of science abduction means, that the effect of a palaeo process is known. e.g. a recent sediment body including specific properties of this archive. There are, however, potentially a range of laws that could be applied to explain the cause, e.g. a human or a climatic impact or internal system behaviour. From a methodological point of view this means that the coupling of cause and effect has to consider several potential starting points of the sediment flux system and a range of laws or explanations which increases the degree of uncertainty significantly. Particularly in modelling plaeo sediment flux systems no reliable transfer functions exist which translate sediment archive properties into flux processes. This general methodological challenge for reconstructing palaeo systems is a particular problem in fluvial systems. Fluvial systems act as a filter whose properties for past time scales are widely unknown. This represents a decoupled cause-effect relationship. The filter function of these system types means, that the external signal that drives the sediment flux record cannot be read directly from that record and that e.g. climatic hypotheses eventually are not testable. The methodology to link archive and process therefore requires spatially-structured storage and release models including abductive interpretation laws for internal feedbacks, thresholds and complex non-linear dynamics. Based on these arguments the aim this presentation is a discussion of a methodological framework in past fluvial system understanding.

  12. Lahar hazards at Agua volcano, Guatemala

    USGS Publications Warehouse

    Schilling, S.P.; Vallance, J.W.; Matías, O.; Howell, M.M.

    2001-01-01

    At 3760 m, Agua volcano towers more than 3500 m above the Pacific coastal plain to the south and 2000 m above the Guatemalan highlands to the north. The volcano is within 5 to 10 kilometers (km) of Antigua, Guatemala and several other large towns situated on its northern apron. These towns have a combined population of nearly 100,000. It is within about 20 km of Escuintla (population, ca. 100,000) to the south. Though the volcano has not been active in historical time, or about the last 500 years, it has the potential to produce debris flows (watery flows of mud, rock, and debris—also known as lahars when they occur on a volcano) that could inundate these nearby populated areas.

  13. A Search for Unconfined Fluvial Outflow Deposits on Mars

    NASA Technical Reports Server (NTRS)

    Zimbelman, J. R.; Bourke, M. C.

    2000-01-01

    Fluvial processes have been active during a large portion of Martian history, as evidenced by a variety of erosional features, ranging from concentrations of small channels to scour features generated by floods that affected enormous areas on Mars. Most research efforts prior to Mars Global Surveyor (MGS) focused on channelized reaches since these were some of the most convincing fluvial features on the planet. Since MGS reached its planned mapping orbit in 1999, a new era of Mars exploration has been opened. The m-scale resolution of the Mars Orbiter Camera (MOC), the precise elevation measurements of the Mars Orbiter Laser Altimeter (MOLA), and the compositional constraints derived from the Thermal Emission Spectrometer (TES) allows one now to search for deposits as well as erosional landforms. Here we describe our initial efforts at a search for deposits on Mars where flow was no longer confined within a topographic channel. We are using both new MGS and existing Viking data, in conjunction with field results of fluvial deposits in unconfined reaches from central Australia and elsewhere as analogues for the deposit characteristics to search for on Mars. Additional information is contained in the original extended abstract.

  14. Headwaters are critical reservoirs of microbial diversity for fluvial networks

    PubMed Central

    Besemer, Katharina; Singer, Gabriel; Quince, Christopher; Bertuzzo, Enrico; Sloan, William; Battin, Tom J.

    2013-01-01

    Streams and rivers form conspicuous networks on the Earth and are among nature's most effective integrators. Their dendritic structure reaches into the terrestrial landscape and accumulates water and sediment en route from abundant headwater streams to a single river mouth. The prevailing view over the last decades has been that biological diversity also accumulates downstream. Here, we show that this pattern does not hold for fluvial biofilms, which are the dominant mode of microbial life in streams and rivers and which fulfil critical ecosystem functions therein. Using 454 pyrosequencing on benthic biofilms from 114 streams, we found that microbial diversity decreased from headwaters downstream and especially at confluences. We suggest that the local environment and biotic interactions may modify the influence of metacommunity connectivity on local biofilm biodiversity throughout the network. In addition, there was a high degree of variability in species composition among headwater streams that could not be explained by geographical distance between catchments. This suggests that the dendritic nature of fluvial networks constrains the distributional patterns of microbial diversity similar to that of animals. Our observations highlight the contributions that headwaters make in the maintenance of microbial biodiversity in fluvial networks. PMID:24089333

  15. Does deposition depth control the OSL bleaching of fluvial sediment?

    NASA Astrophysics Data System (ADS)

    Cunningham, A. C.; Wallinga, J.; Hobo, N.; Versendaal, A. J.; Makaske, B.; Middelkoop, H.

    2014-07-01

    The Optically Stimulated Luminescence (OSL) signal from fluvial sediment often contains a remnant from the previous deposition cycle, leading to a partially bleached equivalent-dose distribution. Although identification of the burial dose is of primary concern, the degree of bleaching could potentially provide insights into geomorphic processes. However, comparison of bleaching between samples is complicated by sample-to-sample variation in aliquot size and luminescence sensitivity. Here we develop an age model to account for these effects. With measurement data from multi-grain aliquots, we use Bayesian computational statistics to estimate the burial dose and bleaching parameters of the single-grain dose distribution. We apply the model to 46 samples taken from fluvial sediment of Rhine branches in the Netherlands, and compare the results with environmental predictor variables (depositional energy and environment, sample depth, depth relative to mean water level, dose rate). We find no significant correlations between any predictor variable and the bleaching parameters, although large uncertainties may be obscuring relationships. However, the best bleached samples are found close to the mean water level. Based on these results, we hypothesize that bleaching occurs mainly during fluvial transport rather than upon deposition, with extra bleaching possible for sediments near the transition of channel to overbank deposits due to local reworking after deposition either by wind or water.

  16. Discrepancy between fluvial incision and erosion rates in Pamir

    NASA Astrophysics Data System (ADS)

    Fuchs, Margret; Gloaguen, Richard; Pohl, Eric

    2015-04-01

    Understanding mountain evolution relies on quantitative estimates of surface processes. Variations in magnitude allow to decipher the control of tectonic and climatic factors. However, significant discrepancies exist between fluvial incision and erosion rates in Pamir. Optically stimulated luminescence (OSL)-based terrace incision along the Panj at the western Pamir margin outpaces cosmogenic nuclide (CN)-based erosion of marginal basins by up to 10 times. Differences in the captured time interval of both methods are not convincing to explain the contrast. The millennial erosion rates are highest (1.0 - 1.5 mm/yr) where long-term (104 years) fluvial incision is moderate (2 - 5 mm/yr). In contrast, erosion is lower (~0.8 mm/yr) where incision is highest (7 - 10 mm/yr), although the millennial scale of rates suggests to represent the most recent stage of adjustment to base level lowering. Analyses of fluvial incision and erosion patterns in Pamir reveal differing control factors. The longitudinal profile and valley profiles of the Panj highlight links between fluvial incision and tectonic structures. Several river captures across Pamir domes correspond to intense incision, while southern dome boundaries coincide with base levels of successive river segments. The interpretation of river captures implies sudden base level drops for basins at the Pamir margins. The generally high erosion at the Pamir margins (0.5 - 1.5 mm/yr) correlate with the resulting steep slopes (0.75 quartiles of values within a basin) with an R2 of ~0.8. The coincidence of the highest erosion rates with increased moisture supply from the Westerlies indicates an additional role of precipitation that becomes evident in multiple linear regression of erosion with the 0.75 quartiles of steep slopes and precipitation (R2 of 0.93). Hence, steep slopes are the primary precondition for high erosion, but sufficient winter precipitation (snow) and the related concentrated discharge during the melting season are needed for an efficient sediment transport out of basins. Accordingly, the discrepancy between erosion in marginal basins and fluvial incision along the Panj is lowest (~2 - 3 times) where a minimum of precipitation facilitates the sediment transport from hillslopes into the river channels and out of basins. We propose that river captures are responsible for the strong base level drop driving the incision along the Panj and consequently, initiate steep hillslopes that will contribute to high erosion at the Pamir margins. Precipitation may act as limiting factor to hillslope adjustment and consequently to erosion processes.

  17. Estuarine fluvial floodplain formation in the Holocene Lower Tagus valley (Central Portugal) and implications for Quaternary fluvial system evolution

    NASA Astrophysics Data System (ADS)

    van der Schriek, Tim; Passmore, David G.; Rolão, Jose; Stevenson, Anthony C.

    2007-11-01

    We present a brief synthesis of the Quaternary fluvial record in the Lower Tagus Basin (central Portugal), concentrating on factors controlling infill and incision. The Holocene part of the record forms the focus of this paper and guides the questioning of the basic assumptions of the established Quaternary fluvial evolution model, in particular the link between sea-level change and fluvial incision-deposition. We suggest that several incision-aggradation phases may have occurred during glacial periods. Major aggradation events may overlap with cold episodes, while incision appears to concentrate on the warming limb of climate transitions. The complex stratigraphy of the Quaternary record in the Lower Tagus valley is influenced by repeated base-level and climate changes. This paper submits the first chronostratigraphic framework for valley fill deposits in the Lower Tagus area. Sea-level rise forced aggradation and controlled deposition of the fine-grained sedimentary wedge underlying the low-gradient Lower Tagus floodplain. Investigations have focused on the lower Muge tributary, where rapidly aggrading estuarine and fluvial environments were abruptly established (∼8150 cal BP) as sea level rose. Base level at the valley mouth controlled the upstream extent of the fine-grained backfill. Tidal environments disappeared abruptly (∼5800 cal BP) when the open estuary at the Muge confluence was infilled by the Tagus River. The decrease and final still stand of sea-level rise led to floodplain stabilisation with peat (∼6400-5200 cal BP) and soil formation (∼5200-2200 cal BP). Localised renewed sedimentation (∼2200-200 cal BP) is linked to human activity.

  18. Fluvial geomorphology: where do we go from here?

    NASA Astrophysics Data System (ADS)

    Smith, Derald G.

    1993-07-01

    The evolution of geomorphology and in particular, fluvial geomorphology, is at a crossroads. Currently, the discipline is dismally organized, without focus or direction, and is practised by individualists who rarely collaborate in numbers significant enough to generate major research initiatives. If the discipline is to mature and to prosper, we must make some very difficult decisions that will require major changes in our ways of thinking and operating. Either the field stays in its current operational mode and becomes a backwater science, or it moves forward and adopts the ways of the more competitive sectors of the earth and biosciences. For the discipline to evolve, fluvial geomorphologists must first organize an association within North America or at the international level. The 3rd International Geomorphology Conference may be a start, but within that organization we must develop our own divisional and/or regional organizations. Within the Quaternary geology/geomorphology divisions of the Geological Socieity of America (GSA), Association of American Geographers (AAG), American Geophysical Union (AGU) and British Geomorphology Research Group (BGRG) the voice of fluvial geomorphology is lost in a sea of diverse and competitive interests, though there is reason for hope resulting from some recent initiatives. In Canada, we have no national geomorphology organization per se; our closest organization is Canqua (Canadian Quaternary Association). Next, fluvial researchers must collaborate, by whatever means, to develop "scientific critical mass" in order to generate ideas and long-range goals of modest and major scientific importance. These projects will help secure major research funding without which, research opportunities will diminish and initiating major new research will become nearly impossible. Currently, we are being surpassed by the glaciologists, remote sensors, ecologists, oceanographers, climatologists-atmospheric researchers and some Quaternary scientists, because they are organized and successfully promote and sell a variety of global change research and other large-scale projects for major funding. Moreover, I see no end to their current success and future prospects as research councils and the public perceives continued deterioration of climate and ecosystems. Next, senior fluvial researchers must work more closely with junior researchers to instill collaborative attitudues, generate group synergism and to provide the inspiration to help "kick start" their careers so they can quickly reach critical momentum. Finally, we must embrace the model of success used by our colleagues in associated, more successful parts of the sciences. An issue we must debate now is whether our only hope is to climb onto the global change and sustainable development bandwagons or to evolve our own mega-projects and scientific agendas. Governments are financially constrained and future lean and competitive times are a certainty. The good old days are over; we are at a historical break point. University and government budget cuts are eliminating ever increasing numbers of geomorphology faculty and research positions. The discipline must take action or suffer the consequences. If we do nothing, the decision-making powers may reclassify the field as scientifically irrelevant. Our current situation will require more than repackaging of existing concepts, suggesting "band-aid" paradigms, and proposing "quick-fix" gimmicks. We must make some fundamental changes in the way we think and operate in order to develop a survival plan before it is too late. We must get together and talk about what kind of future we want and how to achieve it before geomorphology falls into a state of irreversible decay. This article is not about how wonderful the future will be. Its aim is to awaken fluvial geomorphologists from complacency so that they can take action and prepare for tough competitive times ahead. In the following paragraphs I outline some of my deep concerns about the future of our field and suggest some survival remedies.

  19. Western Mediterranean environmental changes: Evidences from fluvial archives

    NASA Astrophysics Data System (ADS)

    Wolf, Daniel; Faust, Dominik

    2015-08-01

    When dealing with current and past landscape evolution, a key issue addresses responses of geomorphic systems to the large number of influencing variables. Identifying morphodynamic phases and revealing interrelations with specific driving forces are demanding tasks for Quaternary research. In this paper, we present late Pleistocene and Holocene fluvial sedimentation patterns of three Western Mediterranean river catchments, namely Jarama River, Guadalete River and Guadalquivir River that extent along a climatic transect from semi-humid SW-Spain to semi-arid central Spain. These studies are based on extensive fieldwork conducted on 36 exposures and 13 drillings in floodplain positions. Field data is supported by geochemical analyses, while the chronological framework was obtained from the analyses of 70 radiocarbon samples. Results show distinct patterns of fluvial sedimentation as well as soil formation linked to floodplain stability for each river catchment. On regional or catchment scale, pollen stratigraphical correlation and comparison with lacustrine records show that fluvial dynamics have a strong reaction to climatic shifts, with phases of high fragility characterized by catchment erosion and floodplain sedimentation in response to climatic aridification events and phases of climate change in general. The comparison of the examined river systems reveals that periods of supra-regional floodplain sedimentation in several catchments occurred from 8.0 to 7.0, 5.0 to 3.8, 2.2 to 1.5, and around 1.0 as well as 0.4 ka cal. BP, while we found periods of supra-regional soil formation from 13.3 to 12.7, 7.0 to 5.1 (with a short interruption around 6.0 to 5.5 ka), 2.8 to 2.3 ka, 1.4 to 1.2 ka, and 0.8 to 0.5 ka cal. BP. Beside these consistencies we found deviating dynamic patterns that are apparently expressed in terms of differing onset and offset, differing durations, or even the lack of fluvial system response. The main reasons for this can be seen in different regional climate condition and impacts of further influencing factors, or in different levels of sensitivity of the river catchments that may be controlled by initial hydrological conditions, catchment size, or the degree of anthropogenic influence. A larger scale assessment shows that fluvial dynamic patterns are hardly comparable across entire Spain due to strong spatial heterogeneity of physiographic and climatic conditions on the Iberian Peninsula, in particular when areas are influenced by different circulation systems (e.g. regions influenced by the Atlantic Ocean vs. regions influenced by the Mediterranean Sea). However, the consideration of North Atlantic marine records reveals a certain coupling between North Atlantic coolings, atmospheric processes leading to arid climate over large parts of Spain, as well as increased landscape instability including strong fluvial sedimentation activity. Attendant atmospheric conditions are discussed.

  20. Energy, time, and channel evolution in catastrophically disturbed fluvial systems

    USGS Publications Warehouse

    Simon, A.

    1992-01-01

    Two diverse fluvial systems show that with time, channels adjust such that the rate of energy dissipation is minimized. One fluvial system, characterized by high relief and coarse-grained sediment, was subjected to an explosive volcanic eruption; the other system, characterized by low relief and fine-grained sediment, was subjected to dredging and straightening. Study of the expenditure of kinetic- and potential-energy components of total-mechanical energy provide an energy-based rationale of the interdependency between processes and forms during channel evolution. Spatial and temporal trends of aggradation and degradation are similar although relative amounts of aggradation in the high-energy system are greatly enhanced by the deposition of large amounts of eroded bank material from upstream reaches. Degradation accompanied by widening is the most efficient means of energy dissipation because all components of total-mechanical energy decrease with time. Widening dominates energy dissipation in the coarse-grained system to offset increases in hydraulic depth caused by incision. In the low-energy fine-grained system, channel adjustment and energy dissipation are dominated by vertical processes because of low relative values of kinetic energy, and because eroded bank sediment is transported out of the drainage basin and does not aid in downstream aggradation, energy dissipation, or channel recovery. Specific energy is shown to decrease nonlinearly with time during channel evolution and provides a measure of reductions in available energy at the channel bed. Data from two sites show convergence towards a minimum specific energy with time. Time-dependent reductions in specific energy at a point act in concert with minimization of the rate of energy dissipation over a reach during channel evolution as the fluvial systems adjust to a new equilibrium. ?? 1992.

  1. Large Fluvial Fans: Aspects of the Attribute Array

    NASA Technical Reports Server (NTRS)

    Wilkinson, Justin M.

    2015-01-01

    In arguing for a strict definition of the alluvial fan (coarse-grained with radii less than10 km, in mountain-front settings), Blair and McPherson (1994) proposed that there is no meaningful difference between large fluvial fans (LFF) and floodplains, because the building blocks of both are channel-levee-overbank deposits. Sediment bodies at the LFF scale (greater than 100 km long, fan-shaped in planform), are relatively unstudied although greater than 160 are now identified globally. The following perspectives suggest that the significance of LFF needs to be reconsidered.

  2. Downstream-migrating fluvial point bars in the rock record

    NASA Astrophysics Data System (ADS)

    Ghinassi, Massimiliano; Ielpi, Alessandro; Aldinucci, Mauro; Fustic, Milovan

    2016-04-01

    Classical models developed for ancient fluvial point bars are based on the assumption that meander bends invariably increase their radius as meander-bend apices migrate in a direction transverse to the channel-belt axis (i.e., meander bend expansion). However, many modern meandering rivers are also characterized by down-valley migration of the bend apex, a mechanism that takes place without a significant change in meander radius and wavelength. Downstream-migrating fluvial point bars (DMFPB) are the dominant architectural element of these types of meander belts. Yet they are poorly known from ancient fluvial-channel belts, since their disambiguation from expansional point bars often requires fully-3D perspectives. This study aims to review DMFPB deposits spanning in age from Devonian to Holocene, and to discuss their main architectural and sedimentological features from published outcrop, borehole and 3D-seismic datasets. Fluvial successions hosting DMFPB mainly accumulated in low accommodation conditions, where channel belts were affected by different degrees of morphological (e.g., valleys) or tectonic (e.g., axial drainage of shortening basins) confinement. In confined settings, bends migrate downstream along the erosion-resistant valley flanks and little or no floodplain deposits are preserved. Progressive floor aggradation (e.g., valley filling) allow meander belts with DMFPB to decrease their degree of confinement. In less confined settings, meander bends migrate downstream mainly after impinging against older, erosion-resistant channel fill mud. By contrast, tectonic confinement is commonly associated with uplifted alluvial plains that prevented meander-bend expansion, in turn triggering downstream translation. At the scale of individual point bars, translational morphodynamics promote the preservation of downstream-bar deposits, whereas the coarser-grained upstream and central beds are less frequently preserved. However, enhanced preservation of upstream-bar deposits can be controlled by aggradation at the scale of the entire meander belt. Despite their different preservation potential, the sedimentology of downstream-bar deposits is overall similar to that of expansional bars, since a downstream decrease in grain size and dominance of upbar-directed palaeoflows are observed in both cases. Bar-tail deposits are instead distinctive of DMFPB, specifically when channel-flow impinges at high angle against river outer banks. There, fine-grained counter-point bars or coarse-grained eddy-accretion deposits can accumulate. Channel belts dominated by DMFPB develop cross-sectional configurations featuring two main marginal trenches, commonly filled with bar tail deposits.

  3. Wilmington Submarine Canyon: a marine fluvial-like system.

    USGS Publications Warehouse

    McGregor, B.; Stubblefield, W.L.; Ryan, William B. F.; Twichell, D.C.

    1982-01-01

    Midrange sidescan sonar data show that a system of gullies and small channels feeds into large submarine canyons on the Middle Atlantic Continental Slope of the US. The surveyed canyons all have relatively flat floors, but they have different channel morphologies. Wilmington Canyon has a meandering channel that extends down the Continental Slope and across the Continental Rise, whereas two canyons south of Wilmington Canyon have straight channels that trend directly downslope onto the rise. The morphology of these submarine canyon systems is remarkably similar to that of terrestrial fluvial systems.-Authors

  4. New Mesoscale Fluvial Landscapes - Seismic Geomorphology and Exploration

    NASA Technical Reports Server (NTRS)

    Wilkinson, M. J.

    2013-01-01

    Megafans (100-600 km radius) are very large alluvial fans that cover significant areas on most continents, the surprising finding of recent global surveys. The number of such fans and patterns of sedimentation on them provides new mesoscale architectures that can now be applied on continental fluvial depositional systems, and therefore on. Megafan-scale reconstructions underground as yet have not been attempted. Seismic surveys offer new possibilities in identifying the following prospective situations at potentially unsuspected locations: (i) sand concentrations points, (ii) sand-mud continuums at the mesoscale, (iii) paleo-valley forms in these generally unvalleyed landscapes, (iv) stratigraphic traps, and (v) structural traps.

  5. Reservoir heterogeneity in the middle Frio Formation: Case studies in Stratton and Agua Dulce fields, Nueces County, Texas

    SciTech Connect

    Kerr, D.R. )

    1990-09-01

    Selected middle Frio (Oligocene) reservoirs of Stratton field and the contiguous Agua Dulce field are being studied as part of a Gas Research Institute/Department of Energy/State of Texas cosponsored program designed to improve reserve growth in mature gas fields. Over the past four decades, Stratton has produced 2.0 tcf of gas from 113 middle Frio reservoirs, and Agua Dulce has produced 1.6 tcf from 116 reservoirs. Recent drilling and workover activities, however, suggest the presence of additional untapped or bypassed middle Frio reservoirs. Four reservoirs, the E18/6,020-ft, E21/6,050-ft, E31/6,100-ft, and E41/Bertram, were evaluated over a 13,000-acre tract that includes areas adjacent to both fields. The middle Frio is composed of sand-rich channel-fill and splay deposits interstratified with floodplain mudstones, all forming part of the Gueydan fluvial system. Channel-fill deposits are 30 ({plus minus}15) ft thick and 2,500 ({plus minus}500) ft wide. Splay deposits are up to 30 ft thick proximal to channels and extend as much as 2 mi from channels. Channel-fill and associated splay sandstones are reservoir facies (porosity 20%; permeability = 10s to 100s md); floodplain mudstones and levee sandy mudstones are barriers to flow facies separating individual reservoirs vertically and laterally. The E41/Bertram reservoir is an example of a laterally stacked channel system deposited during relatively slow aggradation. This reservoir includes sand-on-sand contacts and is composed of mostly leaky compartments. The E 18/6,020-ft, E21/6,050-ft, and E31/6,100ft reservoirs are examples of vertically stacked channel systems reflecting higher rates of aggradation. Vertically stacked architectures are more favorable for isolated compartments and therefore are better candidates for infield reserve growth.

  6. Quantifying the transition from fluvial- to wave-dominance for river deltas with multiple active channels

    NASA Astrophysics Data System (ADS)

    Nienhuis, J.; Ashton, A. D.; Giosan, L.

    2012-12-01

    The plan-view morphologies of fluvial- and wave-dominated deltas are clearly distinctive, but transitional forms are numerous. A quantitative, process-based description of this transition remains unexplored, particularly for river deltas with multiple active channels. Previous studies focused on general attributes of the fluvial and marine environment, such as the balance between wave energy and river discharge. Here, we propose that the transition between fluvial and wave dominance is directly related to the magnitude of the fluvial bedload flux to the nearshore region versus the alongshore sediment transport capacity of waves removing sediment away from the mouth. In the case of a single-channel delta, this balance can be computed for a given distribution of waves approaching shore. Fluvial dominance occurs when fluvial sediment input exceeds the wave-sustained maximum alongshore sediment transport for all potential shoreline orientations both up- and downdrift of the river mouth. However, deltaic channels have the tendency to bifurcate with increasing fluvial strength. Initial bifurcation splits the fluvial sediment flux among individual channels, while the potential sediment transport by waves remains constant for both river mouths. At higher bifurcation orders, multiple channels interact with each other alongshore, a situation more complicated than the single channel case and one that cannot be simple addressed analytically. We apply a model of plan-view shoreline evolution to simulate the evolution of a deltaic environment with multiple active channels. A highly simplified fluvial domain is represented by deposition of sediment where channels meet the coast. We investigate two scenarios of fluvial delivery. The first scenario deposits fluvial sediment alongshore on a self-similar predefined network of channels. We analyze the effects of different network geometrical parameters, such as bifurcation length, bifurcation angle, and sediment partitioning. In the second scenario, local conditions help determine where channels form, distribute sediment and bifurcate, therefore allowing feedbacks between the marine and fluvial domains. With increasing fluvial sediment flux, the delta transitions from a classic cuspate morphology to a space-filling, radial fluvial delta. This simplified model allows us to quantify the transition from fluvial to wave dominance and enables comparisons with natural examples near this transition, such as the Tinajones lobe of the Sinu River Delta, Colombia, and the Po Delta, Italy.

  7. Fluvial sediment fingerprinting: literature review and annotated bibliography

    USGS Publications Warehouse

    Williamson, Joyce E.; Haj, Adel E., Jr.; Stamm, John F.; Valder, Joshua F.; Prautzch, Vicki L.

    2014-01-01

    The U.S. Geological Survey has evaluated and adopted various field methods for collecting real-time sediment and nutrient data. These methods have proven to be valuable representations of sediment and nutrient concentrations and loads but are not able to accurately identify specific source areas. Recently, more advanced data collection and analysis techniques have been evaluated that show promise in identifying specific source areas. Application of field methods could include studies of sources of fluvial sediment, otherwise referred to as sediment “fingerprinting.” The identification of sediment is important, in part, because knowing the primary sediment source areas in watersheds ensures that best management practices are incorporated in areas that maximize reductions in sediment loadings. This report provides a literature review and annotated bibliography of existing methodologies applied in the field of fluvial sediment fingerprinting. This literature review provides a bibliography of publications where sediment fingerprinting methods have been used; however, this report is not assumed to provide an exhaustive listing. Selected publications were categorized by methodology with some additional summary information. The information contained in the summary may help researchers select methods better suited to their particular study or study area, and identify methods in need of more testing and application.

  8. Multiescalar studies of fracturing mechanisms in fluvial-lacustrine basins

    NASA Astrophysics Data System (ADS)

    Carreon-Freyre, D.; Cerca, M.; Hidalgo, C.; Hernandez-Marin, M.

    2007-05-01

    Fracturing of clayey fluvial and lacustrine deposits has become a major problem in several cities of central Mexico. The available data reveals the coexistence of several factors determining fracturing at different scales. As main factors we analyze the variation in compressibility of sediments causing differential deformation and withdrawal of groundwater causing a drop in pore pressure. Compressibility depends on consolidation, a term that in soil mechanics refers to the expulsion of interstitial water, and provokes volume decrease and land subsidence. Although major volume decrease occurs in the vertical scale, consolidation of silty clayey materials generates also horizontal tensile stresses. Considering that this factor can be determining to the generation of fractures, the deformational conditions of clayey, silty and sandy sequences is analyzed integrating their stratigraphy and mechanical characteristics. A particular emphasis is made in the mineralogical heterogeneity of the clay fraction that can be related to compressibility variations and can generate micro-fracturing by differential deformation. As study case we analyze the mechanical and geological properties of two sedimentary sequences with contrasting hydraulic and mechanical behavior. Our results show that the paleoenvironmental history of sediments can be used to determine a specific type of fracturing. Thus, the fracturing in fluvial lacustrine deposits is not a random phenomenon but is highly dependent of the geological properties of materials.

  9. Fluvial biogeomorphology in the Anthropocene: Managing rivers and managing landscapes.

    NASA Astrophysics Data System (ADS)

    Viles, Heather

    2015-04-01

    Biogeomorphology considers the many, and often complex, interactions between ecological and geomorphological processes. The concept of the Anthropocene deserves greater attention by scientists working on biogeomorphology, as will be demonstrated in this talk though a focus on fluvial environments. Rivers and river systems have been the subject of long-term human interference and management across the world, often in the form of direct manipulation of biogeomorphic interactions. Up to the present three broadly-defined phases of the Anthropocene can be identified - the Palaeoanthropocene, the Industrial Revolution and the Great Acceleration. Each of these broad phases of the Anthropocene has different implications for fluvial biogeomorphology and river management. The nature and dynamics of tufa-depositing systems provide good examples of the differing Anthropocene situations and will be focused on in this talk. We may now be entering a fourth phase of the Anthropocene called 'Earth system stewardship'. In terms of better understanding and managing the biogeomorphic interactions within rivers in such a phase, an improved conceptualisation of the Anthropocene and the complex web of interactions between human, ecological and geomorphological processes is needed.

  10. western mediterranean fluvial history - an attempt to correlate

    NASA Astrophysics Data System (ADS)

    Faust, Dominik; Wolf, Daniel

    2013-04-01

    Western mediterranean fluvial history - an attempt to correlate Dominik Faust & Daniel Wolf (TU Dresden, Germany) Correlation of fluvial sediments over large distances is a challenging issue. However it is worth to try it when reliable and robust data are available. Location of the sites to be correlated play a decesive role. So we considered possible pitfalls (tectonic activity, halokinetic movements, sea level changes, disorder inherent to the system itself) to find and chose the best exposures in order to built up a standard profile for every single river system. Three selected rivers were worked out in detail, the Guadalquivir sequences however are used complementary . We attempt to correlate The Oued Medjerda standard profile from Northern Tunisia (Faust et al. 2004; Zielhofer & Faust 2008) The Rio Jarama standard profile for Central Spain (Wolf et al. 2013) The Rio Guadalete standard profile for Southern Spain (Wolf et al. in review) (The Rio Guadalquivir) We aim to propose a correlation scheme in order to visualize analog and inconsistent trends and to discuss possible driving forces. dominik.faust@tu-dresden.de

  11. Fluvial ecosystem resilience and stability: the role of riparian vegetation

    NASA Astrophysics Data System (ADS)

    Corenblit, Dov; Steiger, Johannes

    2014-05-01

    Riparian vegetation impacts fluvial landform resistance and resilience. Here we analyse the spatial and temporal pattern of biogeomorphic equilibrium conditions within a high energy river system. We quantified rejuvenation and maturation of the biogeomorphic succession using a spatial explicit analysis based on aerial photographs at six dates between 1942 and 2000. The Mediterranean River Tech, France, was chosen because a catastrophic flood in 1940 (recurrence time > 100 years) nearly completely destroyed the riparian forest and thus rejuvenated the biogeomorphic succession, providing a reference state in 1942. Interactions between vegetation establishment and flood regime enhanced the replacement of the dense riparian forest removed in 1940 at the scale of the corridor. Following this major disturbance, the riparian landscape demonstrated a very high resilience related to a positive biogeomorphic feedback driven by pioneer riparian engineer plants trapping sediments. This positive feedback enhanced floodplain construction, vegetation succession and a non-linear increase in biogeomorphic stability. Biogeomorphic equilibrium (ratio between instable active tract and stabilised riparian margins) driven by the interplay of vegetation dynamics and hydrogeormorphic processes was reached thirty years after the catastrophic flood event. The results suggest the existence of abrupt transitions between alternative domains of stability and hysteresis cycles. Based on these findings we propose a topological model of riparian ecosystem resistance and resilience according to biogeomorphic feedbacks. Furthermore, the proposed model developed on the River Tech suggests that biogeomorphic feedbacks play a critical role for transitions between different fluvial styles which determine the evolutionary trajectories of rivers.

  12. Fluvial deposits as an archive of early human activity

    NASA Astrophysics Data System (ADS)

    Mishra, S.; White, M. J.; Beaumont, P.; Antoine, P.; Bridgland, D. R.; Limondin-Lozouet, N.; Santisteban, J. I.; Schreve, D. C.; Shaw, A. D.; Wenban-Smith, F. F.; Westaway, R. W. C.; White, T. S.

    2007-11-01

    River terraces are well established as an important source of Lower and Middle Palaeolithic artefacts in Europe, large collections having been assembled there during the years of manual gravel extraction. Now that many terrace sequences can be reliably dated and correlated with the oceanic record, potentially useful patterns can be recognized in the distribution of artefacts. The earliest appearance of artefacts in terrace staircases, marking the arrival of the first tool-making hominins in the region in question, is the first of several archaeological markers within fluvial sequences. The Lower to Middle Palaeolithic transition, with the appearance of Levallois, is another. Others may be more regional in significance: the occurrences of Clactonian (Mode 1) industry, twisted ovate handaxes and bout coupé handaxes, for example. IGCP Project no. 449 instigated the compilation of fluvial records from all over the 'old world'. Comparison between British and Central European sequences confirms the established view that there is a demarcation between handaxe making in the west and flake/core industries in the east. Other centres of activity reported here have been in the Middle East (Syria), South Africa and India. Data from such areas will be key in deciphering the story of the earlier 'out-of-Africa' migration, that by pre-Homo sapiens people. There is clear evidence for diachroneity between the first appearances of different industries, in keeping with the well-established idea of northward migration.

  13. 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.

  14. Fluvial channels on Titan: Initial Cassini RADAR observations

    USGS Publications Warehouse

    Lorenz, R.D.; Lopes, R.M.; Paganelli, F.; Lunine, J.I.; Kirk, R.L.; Mitchell, K.L.; Soderblom, L.A.; Stofan, E.R.; Ori, G.; Myers, M.; Miyamoto, H.; Radebaugh, J.; Stiles, B.; Wall, S.D.; Wood, C.A.

    2008-01-01

    Cassini radar images show a variety of fluvial channels on Titan's surface, often several hundreds of kilometers in length. Some (predominantly at low- and mid-latitude) are radar-bright and braided, resembling desert washes where fines have been removed by energetic surface liquid flow, presumably from methane rainstorms. Others (predominantly at high latitudes) are radar-dark and meandering and drain into or connect polar lakes, suggesting slower-moving flow depositing fine-grained sediments. A third type, seen predominantly at mid- and high latitudes, have radar brightness patterns indicating topographic incision, with valley widths of up to 3 km across and depth of several hundred meters. These observations show that fluvial activity occurs at least occasionally at all latitudes, not only at the Huygens landing site, and can produce channels much larger in scale than those observed there. The areas in which channels are prominent so far amount to about 1% of Titan's surface, of which only a fraction is actually occupied by channels. The corresponding global sediment volume inferred is not enough to account for the extensive sand seas. Channels observed so far have a consistent large-scale flow pattern, tending to flow polewards and eastwards. ?? 2008.

  15. Fluvial erosion of impact craters: Earth and Mars

    NASA Technical Reports Server (NTRS)

    Baker, V. R.

    1984-01-01

    Geomorphic studies of impact structures in central Australia are being used to understand the complexities of fluvial dissection in the heavily cratered terrains of Mars. At Henbury, Northern Territory, approximately 12 small meteorite craters have interacted with a semiarid drainage system. The detailed mapping of the geologic and structural features at Henbury allowed this study to concentrate on degradational landforms. The breaching of crater rims by gullies was facilitated by the northward movement of sheetwash along an extensive pediment surface extending from the Bacon Range. South-facing crater rims have been preferentially breached because gullies on those sides were able to tap the largest amounts of runoff. At crater 6 a probable rim-gully system has captured the headward reaches of a pre-impact stream channel. The interactive history of impacts and drainage development is critical to understanding the relationships in the heavily cratered uplands of Mars. Whereas Henbury craters are younger than 4700 yrs. B.P., the Gosses Bluff structure formed about 130 million years ago. The bluff is essentially an etched central peak composed of resistant sandstone units. Fluvial erosion of this structure is also discussed.

  16. 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

  17. Revegetation of Fluvial Mine Tailing Deposits: The Use of Five Riparian Shrub Species

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fluvial deposition of mine tailings has caused extensive damage to riparian ecosystems throughout the West. Willows are often used for revegetation of fluvial mine tailing deposits but some species accumulate toxic concentrations of metals in leaves and stems. A greenhouse experiment was conducted ...

  18. Fluvial sediment in Double Creek subwatershed No. 5, Washington County, Oklahoma

    USGS Publications Warehouse

    Bednar, Gene A.; Waldrep, Thomas E.

    1973-01-01

    A total of 21,370 tons of fluvial sediment was transported into reservoir No. 5 and a total of 19,930 tons was deposited. Seventy-eight percent of the total fluvial sediment was deposited during the first 9.2 years, or 63 percent of time of reservoir operation. The computed trap efficiency of reservoir No. 5 was 93 percent.

  19. Riparian shrub metal concentrations and growth in amended fluvial mine tailings

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fluvial mine tailing deposition has caused extensive riparian damage throughout the western United States. Willows are often used for fluvial mine tailing revegetation, but some species accumulate excessive metal concentrations which could be detrimental to browsers. In a greenhouse experiment, gr...

  20. Active tectonics coupled to fluvial erosion in the NW Himalaya

    NASA Astrophysics Data System (ADS)

    Vannay, J.-C.; Grasemann, B.; Rahn, M.; Frank, W.; Carter, A.

    2003-04-01

    Both syntaxial extremities of the Himalaya show a spatial correlation between active exhumation of deep crustal rocks and the presence of powerful rivers, the Indus and the Tsangpo-Brahmaputra, cutting across the range two of the deepest gorges on Earth. These features strongly suggests that vigorous fluvial erosion can locally enhance isostatic and tectonic uplift, which in turn contributes to heat advection and weakening of the crust, as well as to maintain steep topographic gradients [Zeitler et al., 2001]. In order to test this positive feedback model, we combined structural and geochronological data to constrain the tectono-thermal evolution along the Sutlej (NW India), the third largest river cross-cutting entirely the Himalaya. The Himalayan crystalline core zone exposed along the Sutlej Valley is composed of two gneiss sheets, that were successively underthrusted and tectonically extruded as a consequence of the foreland-directed propagation of deformation in the Indian plate margin. During Early to Middle Miocene, combined thrusting along the Main Central Thrust (MCT) and extension along the Sangla Detachment induced the rapid exhumation and cooling of the amphibolite facies to migmatitic High Himalayan Crystalline Sequence [Vannay &Grasemann, 2001]. Underthrusting beneath the MCT led to the creation of the amphibolite facies Lesser Himalayan Crystalline Sequence (LHCS). The LHCS cooled rapidly from Late Miocene to Pleistocene, as a consequence of tectonic extrusion controlled by thrusting along the Munsiari Thrust, and extension in the MCT hanging wall. This phase is still active, as indicated by: (1) cooling rates in excess of 100^oC/Myr during the past 3 Myr in the LHCS; (2) Holocene neo-tectonic activity; (3) present-day hydrothermal activity testifying to elevated near-surface geothermal gradients; and (4) seismic activity along the Munsiari Thrust. Modelling of fluvial erosion in the Himalaya indicate that the Sutlej Valley corresponds to the main zone of high erosion index between the syntaxes [Finlayson et al., 2002]. The correlation between active extrusion of deep crustal rocks and focused fluvial erosion along the Sutlej supports consequently the emerging view of a positive feedback between tectonics, topography, and surface processes during the Himalayan tectono-thermal evolution. Finlayson et al. (2002), Geology, 30, 219 222. Vannay &Grasemann (2001), Geological Magazine 138, 253-276. Zeitler et al. (2001), Tectonics, 20, 712-728.

  1. Modeling post-wildfire fluvial incision and terrace formation

    NASA Astrophysics Data System (ADS)

    Rengers, F. K.; Tucker, G. E.

    2013-12-01

    Wildfires often lead to rapid erosion, sedimentation, and morphologic change. One of the challenges in developing quantitative models of post-fire landscape dynamics is a lack of high-quality datasets that document fluvial system evolution in the years to decades following a destructive fire. This study takes advantage of a natural experiment in post-fire fluvial incision to explore how the magnitude and timing of large flow events following a wildfire can change fluvial channel patterns. The study site is the Spring Creek watershed located in the foothills of central Colorado approximately 26 miles southwest of Denver, Colorado. The site burned during the Buffalo Creek wildfire, which was contained in May 1996. Within the Spring Creek watershed, 79% of the basin was burned and 63% of the burned area was considered high severity (Moody and Martin, 2001). In July 1996 a large rain storm hit the burned watershed and 110 mm of rain fell in one hour (Jarrett, 2001). This storm was larger than the estimated 100-year rainfall intensity of 60 mm/hr. Due to the increased surface erodibility after the wildfire, rapid erosion occurred within the watershed, while the main valley of Spring Creek aggraded with up to 2 m of sediment after this storm. Spring Creek has been incising through this post-wildfire sediment since the 1996 storm, and the terraces from this initial storm are still prevalent and identifiable along the valley. Repeated measurements of valley cross-sections since 1996 provide a comprehensive dataset for testing models of fluvial-system evolution on a decadal time scale. We hypothesize that the current channel pattern results from the specific sequence of rain events that occurred within the four years after the initial 1996 storm filled the valley with sediment. This hypothesis was tested using a two-dimensional coupled model of shallow-water flow, sediment transport, and topographic evolution. Discharge data were obtained from a stream gage installed at Spring Creek in 1997, with records from April 1997 to October 2000. The initial channel topography was constructed by extrapolating the 1996 terraces across the channel. Thus the initial condition for the model is the aggradation after the 1996 storm. We calibrated the model using observed measured discharges and actual closely spaced (10-50 m) cross-sections that were measured before and after large discharges from 1997-2000. Model sensitivity tests are used to explore how the channel evolution might have differed under alternative discharge sequences. For example, the natural discharge from the study site showed three large floods in 1997, two in 1998, one in 1999, and none in 2000. We ran models that varied this sequence to identify the degree to which storm sequence, magnitude, and duration influence the tempo and nature of channel evolution. Early results show that the sequence of storms is indeed important in shaping the overall channel geomorphology.

  2. Probabilistic approaches to the modelling of fluvial processes

    NASA Astrophysics Data System (ADS)

    Molnar, Peter

    2013-04-01

    Fluvial systems generally exhibit sediment dynamics that are strongly stochastic. This stochasticity comes basically from three sources: (a) the variability and randomness in sediment supply due to surface properties and topography; (b) from the multitude of pathways that sediment may take on hillslopes and in channels, and the uncertainty in travel times and sediment storage along those pathways; and (c) from the stochasticity which is inherent in mobilizing sediment, either by heavy rain, landslides, debris flows, slope erosion, channel avulsions, etc. Fully deterministic models of fluvial systems, even if they are physically realistic and very complex, are likely going to be unable to capture this stochasticity and as a result will fail to reproduce long-term sediment dynamics. In this paper I will review another approach to modelling fluvial processes, which grossly simplifies the systems itself, but allows for stochasticity in sediment supply, mobilization and transport. I will demonstrate the benefits and limitations of this probabilistic approach to fluvial processes on three examples. The first example is a probabilistic sediment cascade which we developed for the Illgraben, a debris flow basin in the Rhone catchment. In this example it will be shown how the probability distribution of landslides generating sediment input into the channel system is transposed into that of sediment yield out of the basin by debris flows. The key role of transient sediment storage in the channel system, which limits the size of potential debris flows, is highlighted together with the influence of the landslide triggering mechanisms and climate stochasticity. The second example focuses on the river reach scale in the Maggia River, a braided gravel-bed stream where the exposed sediment on gravel bars is colonised by riparian vegetation in periods without floods. A simple autoregressive model with a disturbance and colonization term is used to simulate the growth and decline in the sediment covered area of the floodplain. The stochastic arrival of floods which erode riparian vegetation is a key ingredient of the dynamics in this model. This example will be used to illustrate how potential effects of flow regulation on sediment dynamics in rivers may statistically be quantified. The third example is a cellular automaton model of individual grain transport and storage in a steep mountain stream which captures the formation and collapse of step-like structures in the channel. In this model stochasticity is included in the input of grains, the probability that individual grains will be blocked by others in transport and form a step, and the probability that that step will collapse. It will be illustrated how this simple model generates complex behaviour in the sediment output, where periods of stasis and sediment storage are punctuated by rapid evacuation of grains as steps collapse. The three examples have one thing in common: the dynamics of sediment output depend not only on stochastic disturbance events but also on the state of the system at the time of the event. Both of these ingredients are needed to statistically describe sediment output in the models, and likely in nature as well. I will conclude by arguing that in the context of stochasticity, traditional notions of stability and equilibrium, of the attribution of cause and effect, and of the timescales of process and form in geomorphic systems, become increasingly difficult.

  3. Water soluble cations and the fluvial history of Mars

    NASA Technical Reports Server (NTRS)

    Silverman, M. P.; Munoz, E. F.

    1975-01-01

    The electrical conductivity and water soluble Na, K, Ca, and Mg of aqueous solutions of terrestrial soils and finely divided igneous and metamorphic rocks were determined. Soils from dry terrestrial basins with a history of water accumulation as well as soils from the topographic lows of valleys accumulated water soluble cations, particularly Na and Ca. These soils as a group can be distinguished from the rocks or a second group of soils (leached upland soils and soils from sites other than the topographic lows of valleys) by significant differences in their mean electrical conductivity and water-soluble Na + Ca content. Similar measurements on multiple samples from the surface of Mars, collected by an automated long-range roving vehicle along a highlands-to-basin transect at sites with morphological features resembling dry riverlike channels, are suggested to determine the fluvial history of the planet.

  4. Modeling fluvial erosion on regional to continental scales

    NASA Technical Reports Server (NTRS)

    Howard, Alan D.; Dietrich, William E.; Seidl, Michele A.

    1994-01-01

    The fluvial system is a major concern in modeling landform evolution in response to tectonic deformation. Three stream bed types (bedrock, coarse-bed alluvial, and fine-bed alluvial) differ in factors controlling their occurrence and evolution and in appropriate modeling approaches. Spatial and temporal transitions among bed types occur in response to changes in sediment characteristics and tectonic deformation. Erosion in bedrock channels depends upon the ability to scour or pluck bed material; this detachment capacity is often a power function of drainage area and gradient. Exposure of bedrock in channel beds, due to rapid downcutting or resistant rock, slows the response of headwater catchments to downstream baselevel changes. Sediment routing through alluvial channels must account for supply from slope erosion, transport rates, abrasion, and sorting. In regional landform modeling, implicit rate laws must be developed for sediment production from erosion of sub-grid-scale slopes and small channels.

  5. Identification and Evaluation of Fluvial-Dominated Deltaic Reservoirs.

    SciTech Connect

    Baken, Mary K.; Andrews, Richard

    1997-11-15

    This document is provided as a Quarterly Technical Progress Report for the program entitled `Identification and Evaluation of Fluvial- Dominated Deltaic (Class I Oil) Reservoirs in Oklahoma`, covering the reporting period of July 1 - September 30, 1997. Work is progressing as expected for the project. The Tonkawa Play workshop was completed as scheduled on July 9, 1997 in Norman Oklahoma. It was attended by 101 people of whom about 55 were operators. The Bartlesville workshop is scheduled for October and November 1997, in three different sites including Tulsa, Bartlesville, and Norman, Oklahoma. The FDD computer facility is fully operational. During this quarter, there were 10 industry individuals who used the computer facility. This project is serving an extremely valuable role in the technology transfer activities for the Oklahoma petroleum industry, with very positive industry feedback.

  6. Fluvial transport of human remains in the lower Mississippi River.

    PubMed

    Bassett, Helen E; Manhein, Mary H

    2002-07-01

    The Mississippi River has claimed many lives over the last several decades. A better understanding of the universal dynamics of its fluvial system can help direct the production of a predictive model regarding the transportation of human remains in the river. The model may then be applied to situations where the location and the identification of water victims are necessarily part of the recovery process. Results from the preliminary phase of a longitudinal project involving the transport of human remains in the Mississippi River are presented and represent the analyses of 233 case files of river victims. A provisional model for fluvial transport of human remains in the Mississippi River is proposed and examined. This model indicates that time in the river and distance a body travels are related. Such a model may assist in pinpointing entry location for unidentified human remains found in the river or on its banks. Further, it has the potential to provide local and regional law enforcement agencies, the United States Coast Guard, and other search and rescue organizations with primary search areas when someone is missing in the river. Other results from this study indicate that a relationship exists between the side of the river where victims enter the water and the side of the river where the remains are recovered. Finally, relationships are established between the length of time before recovery of the remains and state of preservation exhibited by those remains. A secondary benefit from this study is a database of river victims that can be used by a variety of different agencies. PMID:12136979

  7. Fluvial process and the establishment of bottomland trees

    NASA Astrophysics Data System (ADS)

    Scott, Michael L.; Friedman, Jonathan M.; Auble, Gregor T.

    1996-01-01

    The effects of river regulation on bottomland tree communities in western North America have generated substantial concern because of the important habitat and aesthetic values of these communities. Consideration of such effects in water management decisions has been hampered by the apparent variability of responses of bottomland tree communities to flow alteration. When the relation between streamflow and tree establishment is placed in a geomorphic context, however, much of that variability is explained, and prediction of changes in the tree community is improved. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  9. Dynamic Flocculation of Muds in Fluvial to Marine Transitions

    NASA Astrophysics Data System (ADS)

    Keyvani, A.; Strom, K. B.

    2012-12-01

    Rivers are the primary conduits for delivery of sediment and organic matter to the sea. The sediments from river plumes may deposit and be preserved in estuarine and deltaic zones, or may be carried and mixed by ocean currents to deposit elsewhere on the shelf or basin. The sediment settling velocity is the most important parameter in terms of controlling and predicting depositional patterns in river mouths and coastal shelves. Settling velocity greatly impacts the distribution of muds in deltas and turbidity currents, and is largely controlled by grain size and density. The flocculation process yields mud aggregates of variable size and density as a function of turbulent energy and salt levels. Since turbulent energy and salinity both change during the fluvial to marine transition, dynamic flocculation processes may have a significant control to the eventual distribution of sediment through these zones. The purpose of this study is to quantify the evolution of floc size distribution and fractal dimension of suspended flocs with time as a function of time and space as turbulent shear and salinity levels vary in the fluvial to marine transition (river jet/plume and turbidity currents). To do this, experiments are carried out in a laboratory chamber where turbulent shear and salinity levels are varied to mimic a fixed volume of fluid being advected through the transition zone, and floc size distribution properties are measured within the mixing chamber using a specially designed floc imaging system and a set of image processing routines that allows us to measure floc size distributions of suspended flocs. Results demonstrate that floc properties and floc settling velocity change due to the dynamic flocculation and are dependent on the turbulent time history the mud suspension was exposed to under constant concentration. Results from the study are then used to frame a discussion on the relative importance of accounting for these dynamic effects in numerical models of deltas and turbidity currents.

  10. The chemistry of fluvial sediments analyzed by the Curiosity rover

    NASA Astrophysics Data System (ADS)

    Mangold, Nicolas; Thompson, Lucy; Le Deit, Laetitia; Forni, Olivier; Gellert, Ralf; Grotzinger, John; Maurice, Sylvestre; Wiens, Roger

    2015-04-01

    The Curiosity rover has encountered a diversity of sedimentary rocks, which overall have displayed significant variations in both texture and composition. Early observations by the Curiosity rover in Gale crater revealed isolated outcrops of cemented pebbles and sand grains with textures typical of fluvial sedimentary conglomerates (Williams et al., Science, 2013). Sandstones and mudstones, interpreted as having been deposited in a fluvio-lacustrine environment, were observed at Yellowknife Bay, a location identified from orbital images as of significant interest (Grotzinger et al., 2014). More stratified sandstones have been observed in the second and third terrestrial years of investigation in the outcrops named Cooperstown, Kylie and Kimberley, and Pahrump. The different groups of sediments have been interpreted to represent fluvial transport across Gale crater (Grotzinger et al., AGU, 2014), but they show a high variation in their composition, especially at Kimberley where rocks display enhanced K proportion. Among sedimentary rocks, conglomerates provide the most direct knowledge of the source of sediments. Conglomerates observed by Curiosity contain clasts with a strong diversity in albedo and textures indicating multiple sources on the Gale crater rims, with local identification of minerals such as plagioclases and alkali feldspars. Assuming the conglomerates are a mechanically altered product of crustal rocks with relatively little aqueous alteration, the average composition of conglomerates can be considered as a proxy for the source rock composition. This average composition displays a more felsic composition than the Martian average crust as defined by meteorites and orbital data implying that the Gale crater rim is enriched in felsic rocks. The difference in sedimentary composition suggests a variability in source rocks and/or diagenetic evolution compared to the conglomerates that needs to be considered in the broad context of Gale crater's evolution.

  11. The fluvial system response to abrupt climate change during the last cold stage: the Upper Pleistocene River Thames fluvial succession at Ashton Keynes, UK

    NASA Astrophysics Data System (ADS)

    Lewis, S. G.; Maddy, D.; Scaife, R. G.

    2001-02-01

    The last interglacial-glacial cycle (125-10 ka BP) is characterised by numerous rapid shifts in global climate on sub-Milankovitch timescales, recorded in the ocean and ice core records. These climatic fluctuations are clearly recorded in those European terrestrial sedimentary sequences that span this time period without interruption. In the UK, only fragmentary Upper Pleistocene sequences exist, mainly within the fluvial archive of the major river systems such as the Thames. The response of the upper River Thames to abrupt fluctuations in climate is documented in the fluvial sediments beneath the Floodplain Terrace (Northmoor Member of the Upper Thames Formation) at Ashton Keynes, Wiltshire. A number of criteria are set out by which significant changes in the fluvial system may be established from the sedimentological, palaeoecological and geochronological information contained within the succession. The sedimentary succession is divisible into four facies associations, on the basis of their sedimentology and bounding surface characteristics. These represent distinct phases of fluvial activity at the site and allow changes in fluvial style to be inferred. Palaeoecological reconstructions from pollen analysis of peats within the sequence provides an indication of the nature and direction of Late Glacial environmental change and optically stimulated luminescence and radiocarbon dating methods provide chronological control on the sequence. These data suggest that major changes in fluvial style are recorded within the succession, which can be related to the climatic fluctuations that took place on the oxygen isotope stage 5a/4 transition (approximately 70 ka BP) and the Devensian Late Glacial climatic warm-cold-warm oscillation (13-11 ka BP). The changes in fluvial style are a result of variations in sediment supply to the river resulting from changes in slope stability, vegetation cover and cold-climate mass movement processes and variations in discharge regime caused by changes in precipitation patterns, snow cover, permafrost distribution and vegetation cover.

  12. Towards a phoenix phase in aeolian research: shifting geophysical perspectives from fluvial dominance

    SciTech Connect

    Whicker, Jeffrey J; Field, Jason P; Breshears, David D

    2008-01-01

    Aeolian processes are a fundamental driver of earth surface dynamics, yet the importance of aeolian processes in a broader geosciences context may be overshadowed by an unbalanced emphasis on fluvial processes. Here we wish to highlight that aeolian and fluvial processes need to be considered in concert relative to total erosion and to potential interactions, that relative dominance and sensitivity to disturbance vary with mean annual precipitation, and that there are important scale-dependencies associated with aeolian-fluvial interactions. We build on previous literature to present relevant conceptual syntheses highlighting these issues. We then highlight the relative investments that have been made in aeolian research on dust emission and management relative to that in fluvial research on sediment production. Literature searches highlight that aeolian processes are greatly understudied relative to fluvial processes when considering total erosion in different environmental settings. Notably, within the USA, aeolian research was triggered by the Dust Bowl catastrophe of the 1930s, but the resultant research agencies have shifted to almost completely focusing on fluvial processes, based on number of remaining research stations and on monetary investments in control measures. However, numerous research issues associated with intensification of land use and climate change impacts require a rapid ramping up in aeolian research that improves information about aeolian processes relative to fluvial processes, which could herald a post-Dust Bowl Phoenix phase in which aeolian processes are recognized as broadly critical to geo- and environmental sciences.

  13. 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.

  14. Bottomland vegetation distribution along Passage Creek, Virginia, in relation to fluvial landforms.

    USGS Publications Warehouse

    Hupp, C.R.; Osterkamp, W.R.

    1985-01-01

    Persistent distribution patterns of woody vegetation within the bottomland forest of Passage Creek, Virginia, were related to fluvial landforms, channel geometry, streamflow characteristics, and sediment-size characteristics. Distinct species distributional patterns were found on four common fluvial geomorphic landforms: depositional bar, active-channel shelf, floodplain, and terrace. Independent hydrologic characteristics (flow duration and flood frequency) were determined for each of the landforms. Vegetation patterns appear to develop more as a result of hydrologic processes associated with each fluvial landform rather than from sediment-size characteristics. -from Authors

  15. Analysis of Ancient Fluvial Patterns on the Surface of Mars

    NASA Technical Reports Server (NTRS)

    Jethani, Henna; Williams, M. E.

    2010-01-01

    This project involves the study of ancient fluvial patterns on the surface of Mars, including raised curvilinear features (RCFs) and negative relief channels. It requires the use of geological images provided by the Mars Reconnaissance Orbiter to determine how water shaped the surface of Mars in the form of rivers, lakes and/or oceans approximately 3.5 billion years ago, during the Noachian period. The role of the intern is to examine the images and record the corresponding measurements of ancient river systems in an Excel spreadsheet to assist in determining the Noachian water cycle on Mars. Resources used to make these measurements include the Arena software, hand-drawn sketch maps, Microsoft Word, Microsoft Excel and the images provided by the Mars Reconnaissance Orbiter. The Context Imager (CTX) returns black and white images at a resolution of six meters per pixel. The camera can take images with a width of 30 km and a length of 160 km. Seventeen images were observed in total. Images are analyzed and notes are taken concerning their terminal deposits, stream ordering and drainage pattern. The Arena software is utilized to make the images more visible by allowing control of contrast and magnification. Once the image is adjusted, measurements: length, average width, drainage basin area, sinuous ridge area are recorded, at a magnification of one, through using the line segment and polygon tools. After an image has been analyzed and measured, a sketch map is drawn in order to clearly identify the various segments, basins and terminal deposits the intern observed. Observations are used to further classify the fluvial patterns; their drainage pattern is defined as dendritic, parallel, trellis, rectangular, radial, centripetal, deranged or discordant. Once observational notes are completed, mathematical relations are used to determine drainage density, stream frequency, theoretic basin area and sinuosity index. These data will be added to a larger data set that will yield a comprehensive view of early Mars drainage systems. The data obtained from the work conducted will be used to characterize the nature and behavior of water on the surface of Mars. Thorough understanding of the Martian water cycle will serve as biologically significant information. Through working on this project, I acquired insight into the study of planet Mars, and skills in the Arena software as well as the organization of a vast amount of data.

  16. Impact of historic mining activities on fluvial sediment dynamics

    NASA Astrophysics Data System (ADS)

    Notebaert, B.; Verstraeten, G.; Haex, J.

    2009-04-01

    Holocene floodplain deposits are often used as environmental archives of terrestrial ecosystems, but often radiocarbon dating is problematic due to the absence of datable material. One of the possible alternatives is the use of floodplain contaminants, where the presence of contaminants in sediment indicates that these sediments were deposited after the initiation of contamination. The Geul river catchment (350 km²) is located in the loess region of eastern Belgium and southern Netherlands. Lead was probably mined since Roman times, but main mining activities started in 1844, and all mines were closed by 1882. Large amounts of Pb (and other) contaminants were deposited in channel bed and the floodplain following these mining activities, and contaminated deposits are still been reworked by the river. As a result, all sediments which are deposited since 1844 are polluted with Pb. Previous studies on point bar deposits have shown that peaks in Pb production of the mining sites can be recognized in these deposits as peaks in Pb concentration. Sediment samples for analysis were collected from 17 percussion drillings at three floodplain locations (with overbank deposits) and one point bar location, while 35 additional corings give information about the fluvial architecture. Lead concentrations of samples representing 0.05 to 0.2 m soil depth were determined using the flam atomic absorption spectroscopy method. Pb concentrations were plotted to depth, and peaks in Pb concentrations were linked with the mining history to allow the identification of sediments deposited during the start of the mining (1844-1847) and for some corings also during the peak in mining activities (1869). The presence of Pb in gravelly point bar deposits indicate that since the initiation of mining (1844) the lateral movement was 5 to 7 m. On the other hand, previous research suggests that the entire floodplain (150 m wide) has been reworked by meandering during the Holocene. Results for the overbank deposits show that sediment deposition was highest between 1847-1869 (8 mm/a). After the peak mining period (1869-2007) deposition was much lower (1.7 mm/a), but nevertheless still much higher than before the main mining period (early Holocene - 1847: 0.25 mm/a). Although measurement periods differ largely, these differences in rates clearly illustrate the influence of human land use, both mining and agriculture, on fluvial sediment dynamics.

  17. Network Dynamic Connectivity for Identifying Hotspots of Fluvial Geomorphic Change

    NASA Astrophysics Data System (ADS)

    Czuba, J. A.; Foufoula-Georgiou, E.

    2014-12-01

    The hierarchical branching structure of a river network serves as a template upon which environmental fluxes of water, sediment, nutrients, etc. are conveyed and organized both spatially and temporally within a basin. Dynamical processes occurring on a river network tend to heterogeneously distribute fluxes on the network, often concentrating them into "clusters," i.e., places of excess flux accumulation. Here, we put forward the hypothesis that places in the network predisposed (due to process dynamics and network topology) to accumulate excess bed-material sediment over a considerable river reach and over a considerable period of time reflect locations where a local imbalance in sediment flux may occur thereby highlighting a susceptibility to potential fluvial geomorphic change. We have developed a framework where we are able to track fluxes on a "static" river network using a simplified Lagrangian transport model and use the spatial-temporal distribution of that flux to form a new "dynamic" network of the flux that evolves over time. From this dynamic network we can quantify the dynamic connectivity of the flux and integrate emergent "clusters" over time through a cluster persistence index (CPI) to assess the persistence of mass throughout the network. The framework was applied to sand transport on the Greater Blue Earth River Network in Minnesota where three hotspots of fluvial geomorphic change have been defined based on high rates of channel migration observed from aerial photographic analysis. Locations within the network with high CPI coincided with two of these hotspots, possibly suggesting that channel migration here is driven by sediment deposition "pushing" the stream into and thus eroding the opposite bank. The third hotspot was not identified by high CPI, but instead is believed to be a hotspot of streamflow-driven change based on additional information and the fact that high bed shear stress coincided with this hotspot. The proposed network-based dynamic connectivity framework has the potential to place dynamical processes occurring at small scales into a network context to understand how reach-scale changes cascade into network-scale effects, useful for informing the large-scale consequences of local management actions.

  18. What can we learn from fluvial incision in high mountains?

    NASA Astrophysics Data System (ADS)

    Fuchs, Margret; Gloaguen, Richard; Krbetschek, Matthias

    2013-04-01

    High and actively deforming mountain ranges attract the attention of geoscientists as they provide natural laboratories of fast evolving process-response systems. Tectonic compressional settings, often linked to perpendicular extension, control the topographic growth and hence, erosion, transport pathways and sedimentation. High altitude differences within short horizontal distances promote material re-organisation and high rates of surface processes. Furthermore, high mountains constitute orographic barriers that affect atmospheric circulations as well as host different climate regimes similar to those of widely separated latitudinal belts. Both cause a high sensitivity of surface processes to changes in climatic conditions. However, feedbacks between climatic and tectonic forcing are complex. Additionally, the dominance of one or the other varies in space and also over time, inheriting various traces of the paleo-morphodynamic conditions to the subsequent process regimes. To unravel the forces driving the evolution of relief in active mountains, numerous studies employ the drainage network of the corresponding mountains as a proxy of landscape evolution. Especially the rates of river incision provide a powerful tool to characterize the surface response and infer causes behind it. Several parameters of river incision are available to describe the fluvial incision at individual sites (e.g. terrace incision rates), along the river course (e.g. longitudinal river profiles, Hack index) and in its perpendicular dimension (e.g. valley cross sections, valley shape ratios). But they require careful interpretation. They are sensitive to both, climatic and tectonic forcing. Therefore, the synopsis of such indices for fluvial incision is essential to evaluate the role of climatic versus tectonic forcing. Here, we use the Panj river system, the major river draining the Pamir mountains of Central Asia, as an example. The Panj experiences high altitude changes of more than 4000 m and deflects several times from the main river orientation, where it cuts through major deformation zones and dome structures of the Pamir. Our contribution discusses the potentials and limitations of river incision analysis. We infer climatic versus tectonic forcing based on terraces along the Panj river together with the indication from its longitudinal profile, Hack index and valley shape ratios.

  19. Evolution of fluvial systems in salt-walled mini-basins: A review and new insights

    NASA Astrophysics Data System (ADS)

    Banham, Steven G.; Mountney, Nigel P.

    2013-10-01

    The preserved sedimentary expression of fluvial successions accumulated in salt-walled mini-basins records the complex history of basin subsidence, the style of sediment supply, and the pattern of sediment distribution in response to a range of fluvial processes throughout the evolution of such basins. Temporal and spatial variations in the rate of basin subsidence govern the generation of accommodation space, whereas the rate and style of sediment supply govern how available accommodation is filled; together these parameters act as principal controls that dictate the gross-scale pattern of fluvial sedimentation. Additional factors that influence fluvial stratigraphic architecture in salt-walled mini-basins are: (i) the trend and form of inherited basement lineations and faults that control the geometry, orientation and spacing of salt walls that develop in response to halokinesis; (ii) salt thickness and composition that dictate both the maximum potential basin-fill thickness within a developing mini-basin and the rate of evacuation (migration) of salt from beneath evolving mini-basins, leading to the growth of confining salt walls, uplift of which may generate surface topographic expression that influences fluvial drainage patterns; (iii) climate that dictates fluvial style and the processes by which sediment is distributed; and (iv) the inherited direction of drainage relative to the trend of elongate salt walls and locus of sediment supply that dictates how sediments are distributed both within a single mini-basin and between adjacent basins. Examples of fluvial sedimentary architectures preserved in salt-walled mini-basins from a number of geographic regions are used to illustrate and document the primary controls that influence patterns of fluvial sediment accumulation. The distribution of fluvial architectural elements preserved within mini-basins follows a predictable pattern, both within individual basin depocentres and between adjoining basins: drainage pathways preferentially migrate to topographic lows within basins, such as developing rim-synclines, and away from topographic highs, such as uplifting salt walls or developing turtle-back structures. This paper demonstrates a range of fluvial-halokinetic interactions through consideration of a series of case studies, which demonstrate the current understanding of fluvial response to salt-walled mini-basin evolution and which highlight gaps in the current understanding.

  20. Geomorphic evolution of the Martian highlands through ancient fluvial processes

    NASA Astrophysics Data System (ADS)

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

    1993-02-01

    The evolution of crater degradation in the Martian highlands based on variations in crater morphology is traced. The timing of this process related to geology, elevation, and latitude is examined, the nature of fluvial resurfacing is studied, and the approximate rate of denudation is determined. The obtained data make it possible to understand the early geologic history of Mars, the interaction between the atmosphere and surface processes through time, and the nature of highland surface materials. Degradation was found to begin with sheet-flooding and the formation of runoff channels in both the interior and exterior of the craters. Progressive stripping of the ejecta material led to craters with incised rims. Erosion and infilling led to flat doors. With time, continued erosion removed ejecta and rim materials completely. Timing of degradation based on cumulative size-frequency distribution curves of highland crater population indicates that the process ceased completely in the late Hesperian. Global average denudation rates were found to be between 0.0001 and 0.005 mm/yr.

  1. Microbiological and Geochemical Characterization of Fluvially Deposited Sulfidic Mine Tailings

    PubMed Central

    Wielinga, Bruce; Lucy, Juliette K.; Moore, Johnnie N.; Seastone, October F.; Gannon, James E.

    1999-01-01

    The fluvial deposition of mine tailings generated from historic mining operations near Butte, Montana, has resulted in substantial surface and shallow groundwater contamination along Silver Bow Creek. Biogeochemical processes in the sediment and underlying hyporheic zone were studied in an attempt to characterize interactions consequential to heavy-metal contamination of shallow groundwater. Sediment cores were extracted and fractionated based on sediment stratification. Subsamples of each fraction were assayed for culturable heterotrophic microbiota, specific microbial guilds involved in metal redox transformations, and both aqueous- and solid-phase geochemistry. Populations of cultivable Fe(III)-reducing bacteria were most prominent in the anoxic, circumneutral pH regions associated with a ferricrete layer or in an oxic zone high in organic carbon and soluble iron. Sulfur- and iron-oxidizing bacteria were distributed in discrete zones throughout the tailings and were often recovered from sections at and below the anoxic groundwater interface. Sulfate-reducing bacteria were also widely distributed in the cores and often occurred in zones overlapping iron and sulfur oxidizers. Sulfate-reducing bacteria were consistently recovered from oxic zones that contained high concentrations of metals in the oxidizable fraction. Altogether, these results suggest a highly varied and complex microbial ecology within a very heterogeneous geochemical environment. Such physical and biological heterogeneity has often been overlooked when remediation strategies for metal contaminated environments are formulated. PMID:10103249

  2. Timescales of fluvial response to climate and tectonic perturbations

    NASA Astrophysics Data System (ADS)

    Castelltort, Sebastien

    2015-04-01

    Earth's landscapes are composed of connected elements such as hillslopes, bedrock and alluvial rivers, alluvial fans and floodplains for example. Because these entities are dominated by different processes, they might respond in different ways and at different rates to external forcings depending on the nature, magnitude and time scale of changes. Knowledge of those response times is fundamental if we want to extract past climate and tectonics from landscape forms and sedimentary archives. Moreover, the interactions between different landscape elements and their response times also control the response of the landscape as a whole, and the delivery of sediment flux to the basins. Here we review the timescales of fluvial response to perturbations in bedrock and alluvial rivers and discuss the implications for delivery of sediment to basins over multi-millenial timescales. We first use existing relationships for bedrock rivers to study their response to climatic and tectonic perturbations. For alluvial rivers, we consider a simple 1D alluvial reach with a single grain size and an equilibrium slope determined by classical bedload relations. Upstream perturbations of grain size, sediment concentration and water discharge induce river aggradation or degradation according to their effect on river equilibrium slope. While minimum aggradation time can be computed analytically as a function of slope change and sediment supply, the time necessary to degrade to a lower equilibrium slope may be only a function of the timescale of the perturbation in a transport-limited system. We explore the field of natural rivers and their possible response to upstream perturbations.

  3. Fluvial organic carbon losses from a Bornean blackwater river

    NASA Astrophysics Data System (ADS)

    Moore, S.; Gauci, V.; Evans, C. D.; Page, S. E.

    2010-11-01

    The transport of carbon from terrestrial ecosystems such as peatlands into rivers and out to the oceans plays an important role in the carbon cycle because it provides a link between the terrestrial and marine carbon cycles. Concentrations of dissolved organic carbon (DOC) and particulate organic carbon (POC) were analysed from the source to the mouth of the River Sebangau in Central Kalimantan, Indonesia during the dry and wet seasons in 2008/2009 and an annual total organic carbon (TOC) flux estimated. DOC concentrations were higher and POC concentrations lower in the wet season compared to the dry season. As seen in other tropical blackwater rivers, DOC concentration is consistently around 10 times greater than POC concentration. We estimate the annual TOC flux discharged to the Java Sea to be 0.46 Tg year-1 comprising of 93% (0.43 Tg) DOC and 7% (0.03 Tg) POC. This equates to a fluvial TOC loss flux per unit area over the entire Sebangau catchment of 88 g C m-2 yr-1. When extrapolating this TOC loss flux to the peat covered area of Indonesia (206 950 km2), we estimate a TOC loss of 18.2 Tg C yr-1 or ~10% of current estimates of the global annual riverine DOC discharge into the ocean.

  4. Fluvial organic carbon losses from a Bornean blackwater river

    NASA Astrophysics Data System (ADS)

    Moore, S.; Gauci, V.; Page, S.; Evans, C.; Limin, S.

    2010-12-01

    The transport of carbon from terrestrial ecosystems such as peatlands into rivers and out to the oceans plays an important role in the carbon cycle because it provides a link between the terrestrial and marine carbon cycles. Concentrations of dissolved organic carbon (DOC) and particulate organic carbon (POC) were analysed from the source to the mouth of the River Sebangau in Central Kalimantan, Indonesia during the dry and wet seasons in 2008/2009 and an annual total organic carbon (TOC) flux estimated. DOC concentrations were higher and POC concentrations lower in the wet season compared to the dry season. As seen in other tropical blackwater rivers, DOC concentration is consistently around 10 times greater than POC concentration. We estimate the annual TOC flux discharged to the Java Sea to be 0.46 Tg year-1 comprising of 93% (0.43 Tg) DOC and 7% (0.03 Tg) POC. This equates to a fluvial TOC loss flux per unit area over the entire Sebangau catchment of 88g C m-2 yr-1. When extrapolating the Sebangau catchment TOC loss flux (88g C m-2 yr-1) to the peat covered area of Indonesia (206,950 km2), we calculate a TOC loss of 18.2 Tg C yr-1 or ~10% of current estimates of the global annual riverine DOC discharge into the ocean.

  5. Fluvial organic carbon losses from a Bornean blackwater river

    NASA Astrophysics Data System (ADS)

    Moore, S.; Gauci, V.; Evans, C. D.; Page, S. E.

    2011-04-01

    Concentrations of dissolved organic carbon (DOC) and particulate organic carbon (POC) were analysed from the source to the mouth of the River Sebangau in Central Kalimantan, Indonesia during the dry and wet seasons in 2008/2009 and an annual total organic carbon (TOC) flux estimated. DOC concentrations were higher and POC concentrations lower in the wet season compared to the dry season. As seen in other tropical blackwater rivers, DOC concentration is consistently around 10 times greater than POC concentration. We estimate the annual TOC flux discharged to the Java Sea to be 0.46 Tg year-1 comprising of 93% (0.43 Tg) DOC and 7% (0.03 Tg) POC. This equates to a fluvial TOC loss flux per unit area over the entire Sebangau catchment of 88 g C m-2 yr-1. When extrapolating the River Sebangau DOC loss flux (83 g C m-2 yr-1) to the peat covered area of Indonesia (206 950 km2), we estimate a DOC loss of 17.2 Tg C yr-1 or ~10% of current estimates of the global annual riverine DOC discharge into the ocean.

  6. Defining Fluvial Megafans through Geomorphic Mapping and Metrics

    NASA Astrophysics Data System (ADS)

    Sounny-Slitine, M. A.; Latrubesse, E. M.

    2014-12-01

    Fluvial megafans are 'large' fan-shaped bodies of sediment that form from lateral migrations of a river as it exits a topographic front of a mountain belt. The criterion of what differentiates megafans from alluvial fans is an artificial scale divide. The scale divide varies in the literature, with the most common being a 100-km apex-to-toe length. Alternative values as little of 30-km apex-to-toe length have been proposed, as well as alternative metrics like coverage area. The question remains how should we define megafans, and what metrics differentiate them from smaller alluvial fans? To answer these questions, we catalog the known megafans of the world into a geodatabase delineating size and extent of basins both upstream and downstream from the apex. Through remote sensing, elevation modeling and geomorphic mapping, we populated the database with morphometric measurements, qualitative descriptions and basin parameters. We utilize the geodatabase to test a variety of criteria differentiating megafans from alluvial fans. The analysis draws into question a single parameter for defining megafans.

  7. Geomorphic evolution of the Martian highlands through ancient fluvial processes

    NASA Technical Reports Server (NTRS)

    Craddock, Robert A.; Maxwell, Ted A.

    1993-01-01

    The evolution of crater degradation in the Martian highlands based on variations in crater morphology is traced. The timing of this process related to geology, elevation, and latitude is examined, the nature of fluvial resurfacing is studied, and the approximate rate of denudation is determined. The obtained data make it possible to understand the early geologic history of Mars, the interaction between the atmosphere and surface processes through time, and the nature of highland surface materials. Degradation was found to begin with sheet-flooding and the formation of runoff channels in both the interior and exterior of the craters. Progressive stripping of the ejecta material led to craters with incised rims. Erosion and infilling led to flat doors. With time, continued erosion removed ejecta and rim materials completely. Timing of degradation based on cumulative size-frequency distribution curves of highland crater population indicates that the process ceased completely in the late Hesperian. Global average denudation rates were found to be between 0.0001 and 0.005 mm/yr.

  8. Fluvial sedimentation following Quaternary eruptions of Mount St. Helens, Washington

    SciTech Connect

    Janda, R.J.; Meyer, D.F

    1985-01-01

    Depositional records of convulsive volcanic events at Mount St. Helens are in many places obscured by rapid fluvial erosion and deposition close to the volcano. Some major eruptions are recorded primarily by lahars and alluvium deposited tens of kilometers away. About 35 percent of the distinctive hummocky topography of the 1980 North Fork Toutle debris avalanche deposit now resembles an alluvial fan or a braided glacial outwash plain covered with 10 m or more of alluvium. Deposits of small (20 x 10/sup 6/m/sup 3/) but damaging lahars, such as those generated in the afternoon of 18 May 1980 and on 19 March 1982, have been largely eroded away. Rivers draining rapidly eroding areas surrounding Mount St. Helens presently have sediment yields that are among the highest in the world for nonglaciated streams of comparable size. These sediment loads are capable of causing aggradation-induced flooding in populated areas along the lower Toutle and Cowlitz Rivers. Sediment retention structures and dredging have prevented such flooding. Immediately following prehistoric eruptions, however, coarse-grained volcanic alluvium was deposited in the Cowlitz River to levels more than 1 m above the 1980 mud flow inundation level. Post-1980 rapid landscape modifications and high sediment yields are noteworthy because the eruption-impact area has not yet had a major regional storm and potentially catastrophic breachings of avalanche-impounded lakes have been prevented through engineering measures.

  9. Microbiological and geochemical characterization of fluvially deposited sulfidic mine tailings

    SciTech Connect

    Wielinga, B.; Lucy, J.K.; Moore, J.N.; Seastone, O.F.; Gannon, J.E.

    1999-04-01

    The fluvial deposition of mine tailings generated from historic mining operations near Butte, Montana, has resulted in substantial surface and shallow groundwater contamination along Silver Bow Creek. Biogeochemical processes in the sediment and underlying hyporheic zone were studied in an attempt to characterize interactions consequential to heavy-metal contamination of shallow groundwater. Sediment cores were extracted and fractionated based on sediment stratification. Subsamples of each fraction were assayed for culturable heterotrophic microbiota, specific microbial guilds involved in metal redox transformations, and both aqueous- and solid-phase geochemistry. Populations of cultivable Fe(III)-reducing bacteria were most prominent in the anoxic, circumneutral pH regions associated with a ferricrete layer or in an oxic zone high in organic carbon and soluble iron. Sulfur- and iron-oxidizing bacteria were distributed in discrete zones throughout the tailings and were often recovered from sections at and below the anoxic groundwater interface. Sulfate-reducing bacteria were also widely distributed in the cores and often occurred in zones overlapping iron and sulfur oxidizers. Sulfate-reducing bacteria were consistently recovered from oxic zones that contained high concentrations of metals in the oxidizable fraction. Altogether, these results suggest a highly varied and complex microbial ecology within a very heterogeneous geochemical environment. Such physical and biological heterogeneity has often been overlooked when remediation strategies for metal contaminated environments are formulated.

  10. Fluvial Placement of Radioactive Contaminants a Weldon Spring Case Study

    SciTech Connect

    Meier, J.

    2002-02-26

    The operation of the Weldon Spring Uranium Feed Materials Plant in St. Charles, MO between 1958 and 1966 resulted in the migration and emplacement of radioactive contaminants into surface water drainage systems. Multiple drainage systems, receiving from a variety of waste discharge points, combined to create unique and unexpected depositional environment. Discovery and investigation of the depositional environments was a significant technical challenge due to the complex nature of sediment movement and emplacement. The objective of this investigation was to show that application of the knowledge of geomorphic processes is an essential element of a complete stream characterization, pursuant to risk analysis and remediation. This paper sets out to describe many of the expected and unexpected findings of the investigations by the Weldon Spring Site Remedial Action Project (WSSRAP) into the placement and rework of contaminated sediments in stream systems. Information from this paper will be useful to other agencies and contractor personnel faced with the challenge of locating and quantifying contaminated sediments in seemingly haphazard fluvial depositional conditions.

  11. Hydrodynamic perspectives of soil scour in fluvial environment

    NASA Astrophysics Data System (ADS)

    Salim, Sarik; Jayaratne, Ravindra

    2013-09-01

    The major concern for many hydraulic structures is the effect of scour at the toe, when the racing floodwater scours away the bed just downstream of the piers. Therefore, understanding the soil-hydrodynamic interaction needs to be investigated. In this study, a series of 2D laboratory tests have been carried out to study the likelihood of soil scour due to the soil-hydrodynamic interaction and influence of sediment properties. Characteristics such as sediment deposition patterns, longitudinal/lateral spreading length/area, and bed scour profiles for three sediment diameters (i.e. 0.26, 0.30 and 2.40 mm) under dry and wet soil conditions are studied intensively. Experimental results revealed that soil of identical diameters under wet and dry conditions caused significant changes in soil scour rate and deposition patterns. Transport rates in dry condition were much slower than wet condition. It was observed that, for the same flow condition, different soils gave different long term equilibrium deposition patterns due to the grain size distribution and particle shape. Eddies were generated behind the soil samples which resulted in forming a series of `crescent' zones. Findings of this study could offer a qualitative outline of the effects of various parameters to demonstrate a better representation of estimating scour rate in fluvial condition.

  12. Fluvial Drainage Basins and Valley Networks: Eastern Margaritifer Sinus, Mars

    NASA Technical Reports Server (NTRS)

    Boothroyd, J. C.; Grant, J. A.

    1985-01-01

    The fluvial drainage of the eastern Margaritifer Sinus (MC-19NE, SE) and northeastern Argyre (MC-26NE) Quadrangles is dominated by two major longitudinal valley networks, the Parana/Loire system on the east, and the Samara Himera system to the west. It is believed that both of these drainages are through-going to the northwest and debouch into Margaritifer Chaos (general location: 12S, 22.5W). The Parana/Loire drainage is bounded on the east in part by an ancient multi-ringed impact basin. The Parana multi-digitate network drains northwest into a depositional basin, and impact basin floor, characterized by positive relief chaos. It is believed that Loire Vallis heads in the basin; thus Parana and Loire Valles may be treated as one system. Samara Valles heads in the northeastern Argyre Quadrangle and extends as a major truck valley to the northwest. Samara Valles cuts through the hills forming one of the concentric rings of the Ladon impact basin and joins the Himera drainage to trend in a more northerly direction to Margaritifer Chaos. The downstream portion of Himera is considered to be part of the Samara

  13. 3D Geologic and Reservoir Modelling of a Distributive Fluvial System Derived from lidar: A Case Study of the Huesca Fluvial Fan.

    NASA Astrophysics Data System (ADS)

    Burnham, Brian; Hodgetts, David; Redfern, Jonathan

    2014-05-01

    Understanding stratigraphic and depositional architecture in a fluvially dominated system is fundamental when trying to model and characterise properties such as geometric relationships, heterogeneity, lithologic patterns or trends of the system as well as any associated petrophysical properties or behaviours. The Huesca fluvial fan, an Oligocene - Miocene age Distributive Fluvial System (DFS) in the northern extent of the Ebro Basin, is used extensively as an outcrop analogue for modelling fluvial hydrocarbon reservoirs, as well as a base for the DFS model. To further improve understanding of the system, mapping techniques using lidar integrated with Differential Global Navigation Satellite System (DGNSS) measurements were used to create sub-metre (spatially) accurate geologic models of the medial-distal portions of the DFS. In addition to the digital terrain data, traditional field sedimentary logs, structural and palaeocurrent measurements, and samples for petrophysical analysis were also collected near the town of Piracés in a series of amphitheatres and canal cuts that expose excellent two and three-dimensional views of the strata. The geologic models and subsequent analyses derived from the data will provide a quantitative tool to further understand the depositional architecture, geometric relationship and lithologic characteristics across the studied portion of the distributive fluvial system. Utilizing the inherent quantitative nature of the terrain data in combination with the traditional field and sample data collected, an outcrop based geocellular model of the studied section can be constructed by using several geostatistical modelling approaches to describe geo-body geometries (thickness and width ratio) for the associated fluvial architecture, as well as facies distribution and observed petrophysical characteristics. The resolution of the digital terrain data (<10cm) allowed for an accurate integration of the field observations (palaeoflow, sedimentary structures and grain size distributions) into a more complete model of studied portion of the fluvial system. The three-dimensionality of the exposure lends itself well to using lidar as a tool when mapping geo-body geometry and architecture across several kilometres. This approach leads to more accurate, quantitative reservoir and depositional models of the distributive fluvial system.

  14. Late Cenozoic fluvial development within the Sea of Azov and Black Sea coastal plains

    NASA Astrophysics Data System (ADS)

    Matoshko, A.; Gozhik, P.; Semenenko, V.

    2009-09-01

    Late Cenozoic terrestrial deposits are widespread across the northern coastal regions of the Black Sea and the Sea of Azov and represent diverse fluvial, estuarine and deltaic environments. The dating and correlation of these deposits rely on stratigraphically-associated marine index beds, mammalian and molluscan faunas and magnetostratigraphy. In detail the geometries of these sediment bodies are extremely complex, typically varying between localities and representing many cycles of incision and aggradation. However, the overall disposition of the sediments reflects the transition from the uplifting sediment source region to the north and the subsiding depocentre in the interior of the Black Sea to the south. Since the Middle Miocene the area of the Paratethys/Black Sea depocentre has decreased significantly, but since the Middle Pliocene the hinge zone between uplift and subsidence has been located close to the modern coastline. A combination of regional and local differential crustal movements has given rise to the great variety of fluvial sediment bodies, to the erosion-aggradation cycles, different phases and river activity and to the various fluvial landforms that have all been important in landscape development in this region during the past 12 Ma. The fluvial erosion-accumulation cycles (during the upper Serravillian-Messinian, the Zanclean-late Gelasian, and the Pleistocene) and corresponding cycles of relief dissection and planation are reconstructed against a background of local sea-level changes and climatic variations determined from palaeobotanical data. The maximum fluvial incision occurred in the early Zanclean time with alluvial coastal plains, unique in this area, developing in the Gelasian. Increased climatic aridity during the Pleistocene caused a reduction of fluvial activity in comparison with the Late Miocene and Pliocene. The sea-level oscillations and Pleistocene glaciations affected fluvial processes in different ways. The most remarkable events were the substantial reduction of fluvial activity during the Messinian dessication in the Black Sea and drainage of the shelf, with intensive dissection, coeval with the Last Glaciation.

  15. Paraglacial fluvial bedrock incision in postglacial landscapes: the NW Scottish Highlands

    NASA Astrophysics Data System (ADS)

    Whitbread, Katie; Jansen, John; Bishop, Paul; Fabel, Derek

    2010-05-01

    Glacial landscape forms are inherited by rivers following deglaciation. Hillslopes and valley floors configured by glacial erosion control the distribution of bedrock channels and potential sites for fluvial incision. The importance of 'stream power' parameters, channel slope and drainage area (discharge), in controlling the rate of incision is widely accepted, but the rate, timing and mechanisms of incision have yet to be quantified in these settings. The dual controls of glacially conditioned bedrock slopes and sediment supply set two of the key boundary conditions for temporally and spatially dynamic fluvial bedrock incision. Measurement of incision rates in these settings is key to understanding the influence of controls on fluvial erosion, and the role of the process in long-term evolution of deglaciated landscapes. In tectonically-passive, hard-rock terrains, such as the Scottish Highlands, incisional fluvial features such as bedrock channels, gorges and waterfalls are common on glacially carved valley steps. Here we report preliminary data on fluvial incision rates measured with cosmogenic 10Be. Our results confirm a postglacial age of bedrock straths in the NW Scottish Highlands and indicate a vertical incision rate of 0.3 mm/yr into resistant quartzites. Further work will explore erosion mechanisms and rates of incision across the Scottish Highlands, and assess controls on fluvial incision, including the potential role of paraglacial sediment.

  16. Disturbance of fluvial gravel substrates by signal crayfish (Pacifastacus leniusculus)

    NASA Astrophysics Data System (ADS)

    Johnson, Matthew; Rice, Stephen; Reid, Ian

    2010-05-01

    The reworking of substrates by organisms, termed bioturbation, is considered a fundamental processes in marine and terrestrial environments but has remained relatively unstudied in fluvial environments. This studies looks at the bioturbation of fluvial gravel substrates by signal crayfish, an internationally important invasive species. We investigated the impact of signal crayfish activity in a laboratory flume. Bioturbation by crayfish on both loose arrangements of gravel and water-worked surfaces were studied and two sizes of narrowly-graded gravel were used; 11 - 16 mm and 16 - 22 mm. A laser scanner was used to obtain high resolution digital elevation models (DEMs) of gravel surfaces before and after crayfish activity. These DEMs were used to quantify topographic and structural changes to the surfaces due to the activity of crayfish. It was found that crayfish moved substantial quantities of material from all surfaces within six hours of introduction. The majority of the disturbance was associated with small scale (≤ 1 median grain diameter) movements of surface grains due to walking and foraging by crayfish. This textural change resulted in a structural alteration to the substrate surface. After six hours of crayfish activity, there was a 14% reduction in the imbrication of the grains from water-worked surfaces. Crayfish also constructed shallow pits and heaped excavated material into a series of mounds around its edge. Crayfish would always posture in pits in the same way. They would fold their vulnerable tails under their body and place their claws in front of their heads. When in pits crayfish predominately orientated themselves so they were facing an upstream direction. This implies that crayfish dig pits in order to streamline their bodies in the flow and lower their protrusion. Although pits and mounds contributed a relatively small proportion to the overall disturbance of substrates, they significantly increased the roughness of substrates. Pit and mound construction was far more prevalent in loose gravel surfaces. This suggests that water-working of gravel substrates not only reduces the vulnerability of grains to entrainment from the flow, but also disturbance by crayfish. Subsequent to topographic analysis, surfaces disturbed by crayfish were entrained in the laboratory flume and compared to control surfaces on which crayfish were not present. Substantially more material was entrained from crayfish disturbed surfaces than control surfaces for both loose and water-worked gravels. In loose 11 - 16 mm gravels, 20% more grains were entrained from surfaces disturbed by crayfish. For water-worked surfaces this increased to 46%. Not only was the increase in entrained material greater for water-worked surfaces but it was also statistically significant. During extended periods of low flow, gravel beds consolidate with the ingress of fine material and grain rearrangement. Both generally increase grain interlock and both increase the stresses required to entrain bed material during the next flood event. This study indicates that crayfish may oppose the process, jostling grains into less stable positions and increasing grain exposure through the mounding of material excavated from pits. Both will affect gravel stability during flood events. This study shows that invasive species may be having detrimental impacts on the physical environment as well as the wider ecological community.

  17. Fluvial erosion and post-erosional processes on Titan

    USGS Publications Warehouse

    Jaumann, R.; Brown, R.H.; Stephan, K.; Barnes, J.W.; Soderblom, L.A.; Sotin, C.; Le, Mouelic S.; Clark, R.N.; Soderblom, J.; Buratti, B.J.; Wagner, R.; McCord, T.B.; Rodriguez, S.; Baines, K.H.; Cruikshank, D.P.; Nicholson, P.D.; Griffith, C.A.; Langhans, M.; Lorenz, R.D.

    2008-01-01

    The surface of Titan has been revealed by Cassini observations in the infrared and radar wavelength ranges as well as locally by the Huygens lander instruments. Sand seas, recently discovered lakes, distinct landscapes and dendritic erosion patterns indicate dynamic surface processes. This study focus on erosional and depositional features that can be used to constrain the amount of liquids involved in the erosional process as well as on the compositional characteristics of depositional areas. Fluvial erosion channels on Titan as identified at the Huygens landing site and in RADAR and Visible and Infrared Mapping Spectrometer (VIMS) observations have been compared to analogous channel widths on Earth yielding average discharges of up to 1600 m3/s for short recurrence intervals that are sufficient to move centimeter-sized sediment and significantly higher discharges for long intervals. With respect to the associated drainage areas, this roughly translates to 1-150 cm/day runoff production rates with 10 years recurrence intervals and by assuming precipitation this implies 0.6-60 mm/h rainfall rates. Thus the observed surface erosion fits with the methane convective storm models as well as with the rates needed to transport sediment. During Cassini's T20 fly-by, the VIMS observed an extremely eroded area at 30?? W, 7?? S with resolutions of up to 500 m/pixel that extends over thousands of square kilometers. The spectral characteristics of this area change systematically, reflecting continuous compositional and/or particle size variations indicative of transported sediment settling out while flow capacities cease. To account for the estimated runoff production and widespread alluvial deposits of fine-grained material, release of area-dependent large fluid volumes are required. Only frequent storms with heavy rainfall or cryovolcanic induced melting can explain these erosional features. ?? 2008 Elsevier Inc.

  18. Dynamic LiDAR-NDVI classification of fluvial landscape units

    NASA Astrophysics Data System (ADS)

    Ramírez-Núñez, Carolina; Parrot, Jean-François

    2015-04-01

    The lower basin of the Coatzacoalcos River is a wide floodplain in which, during the wet season, local and major flooding are distinguished. Both types of floods, intermittent and regional, are important in terms of resources; the regional flood sediments enrich the soils of the plains and intermittent floods allow obtaining aquatic resources for subsistence during the heatwave. In the floodplain different abandoned meanders and intermittent streams are quickly colonized by aquatic vegetation. However, from the 1990s, the Coatzacoalcos River floodplain has important topographic changes due to mining, road and bridges construction; erosion and sedimentation requires continuous parcel boundaries along with the increasing demand of channel reparation, embankments, levees and bridges associated to tributaries. NDVI data, LiDAR point cloud and various types of flood simulations taking into account the DTM are used to classify the dynamic landscape units. These units are associated to floods in relation with water resources, agriculture and livestock. In the study area, the first returns of the point cloud allow extracting vegetation strata. The last returns correspond to the bare earth surface, especially in this area with few human settlements. The surface that is not covered by trees or by aquatic vegetation, correspond to crops, pastures and bare soils. The classification is obtained by using the NDVI index coupled with vegetation strata and water bodies. The result shows that 47.96% of the area does not present active vegetation and it includes 31.53% of bare soils. Concerning the active vegetation, pastures, bushes and trees represent respectively 25.59%, 11.14% and 13.25%. The remaining 1.25% is distributed between water bodies with aquatic vegetation, trees and shrubs. Dynamic landscape units' classification represents a tool for monitoring water resources in a fluvial plain. This approach can be also applied to forest management, environmental services and habitat analysis. Thus, the unsupervised LiDAR-NDVI approach coupled with flood simulation developed here, allows studying environmental behavior without introducing subjective considerations.

  19. Marine intervals in Neogene fluvial deposits of western Amazonia

    NASA Astrophysics Data System (ADS)

    Boonstra, Melanie; Troelstra, Simon; Lammertsma, Emmy; Hoorn, Carina

    2014-05-01

    Amazonia is one of the most species rich areas on Earth, but this high diversity is not homogeneous over the entire region. Highest mammal and tree-alpha diversity is found in the fluvio-lacustrine Pebas system, a Neogene wetland associated with rapid radiation of species. The estuarine to marine origin of various modern Amazonian fish, plants, and invertebrates has been associated with past marine ingressions into this freshwater Pebas system. The exact nature and age of these invasions is, however, debated. Here we present new evidence from fluvial and fluvio-lacustrine deposits of Neogene age in southeast Colombia, that point to periods of widespread marine conditions in western Amazonia. Our evidence is based on an analysis of marine palynomorphs, such as organic linings of foraminifera and dinoflagellate cysts, present in dark sandy clay sediments that outcrop along the Caqueta and Amazon rivers. Characteristically, the foraminiferal linings can be assigned to three benthic morphotypes only, e.g. Ammonia, Elphidium and Trochammina. This low diversity assemblage is associated with estuarine/marginal marine conditions. No distinct marine elements such as shelf or planktonic species were encountered. The observed foraminiferal linings and dinocyst assemblages are typical for a (eutrophic) shallow marine environment, suggesting that the Pebas freshwater wetland system occasionally changed to (marginal) marine. Although some reworked elements are found, a typical Neogene dinocyst taxon is commonly found supporting in situ deposition. Sedimentological features typical for tidal conditions that are reported for sites in Peru and northeastern Brazil likely relate to these marine ingressions. Sea level changes as well as foreland basin development related to Andes formation may have facilitated the entry of marine water during the Neogene.

  20. Palaeoenvironment of braided fluvial systems in different tectonic realms of the Triassic Sherwood Sandstone Group, UK

    NASA Astrophysics Data System (ADS)

    Medici, G.; Boulesteix, K.; Mountney, N. P.; West, L. J.; Odling, N. E.

    2015-11-01

    Fluvial successions comprising the fills of sedimentary basins occur in a variety of tectonic realms related to extensional, compressional and strike-slip settings, as well as on slowly subsiding, passive basin margins. A major rifting phase affected NW Europe during the Triassic and resulted in the generation of numerous sedimentary basins. In the UK, much of the fill of these basins is represented by fluvial and aeolian successions of the Sherwood Sandstone Group. Additionally, regions that experienced slow rates of Mesozoic subsidence unrelated to Triassic rifting also acted as sites of accumulation of the Sherwood Sandstone Group, one well-exposed example being the eastern England Shelf. The fluvial depositional architecture of deposits of the Sherwood Sandstone Group of the eastern England Shelf (a shelf-edge basin) is compared with similar fluvial deposits of the St Bees Sandstone Formation, eastern Irish Sea Basin (a half-graben). The two studied successions represent the preserved deposits of braided fluvial systems that were influenced by common allogenic factors (climate, sediment source, delivery style); differences in preserved sedimentary style principally reflect their different tectonics settings. Analysis of lithofacies and architectural elements demonstrates that both studied successions are characterized by amalgamated channel-fill elements that are recorded predominantly by downstream-accreting sandy barforms. The different tectonic settings in which the two braided-fluvial systems accumulated exerted a dominant control on preserved sedimentary style and long-term preservation potential. On the eastern England Shelf, the vertical stacking of pebbly units and the general absence of fine-grained units reflect a slow rate of sediment accommodation generation (18-19.4 m/Myr). In this shelf-edge basin, successive fluvial cycles repeatedly reworked the uppermost parts of earlier fluvial deposits such that only the lowermost channel lags tend to be preserved. By contrast, in the eastern Irish Sea Basin of west Cumbria, the rate of sediment accommodation generation was substantially greater (119 m/Myr) such that space was available to preserve complete fluvial cycles, including silty drape units that cap the channelized deposits.

  1. 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.

  2. Characterization of alluvial formation by stochastic modelling of paleo-fluvial processes: The concept and method

    NASA Astrophysics Data System (ADS)

    Jiang, Zhenjiao; Mariethoz, Gregoire; Farrell, Troy; Schrank, Christoph; Cox, Malcolm

    2015-05-01

    Modelling fluvial processes is an effective way to reproduce basin evolution and to recreate riverbed morphology. However, due to the complexity of alluvial environments, deterministic modelling of fluvial processes is often impossible. To address the related uncertainties, we derive a stochastic fluvial process model on the basis of the convective Exner equation that uses the statistics (mean and variance) of river velocity as input parameters. These statistics allow for quantifying the uncertainty in riverbed topography, river discharge and position of the river channel. In order to couple the velocity statistics and the fluvial process model, the perturbation method is employed with a non-stationary spectral approach to develop the Exner equation as two separate equations: the first one is the mean equation, which yields the mean sediment thickness, and the second one is the perturbation equation, which yields the variance of sediment thickness. The resulting solutions offer an effective tool to characterize alluvial aquifers resulting from fluvial processes, which allows incorporating the stochasticity of the paleoflow velocity.

  3. Annual loads of organic contaminants in Chesapeake Bay contributed through fluvial transport

    SciTech Connect

    Foster, G.D.; Lippa, K.A.

    1994-12-31

    Organic contaminants in fluvial transport, atmospheric deposition, urban runoff, and shoreline erosion are being quantified and compared in an effort to understand contaminant inputs and mass balances in Chesapeake Bay. Concentrations of nine organonitrogen and organophosphorus (organo-N/P) pesticides, eight organochlorine (OC) pesticides, polychlorinated biphenyls (PCBs), and four polynuclear aromatic hydrocarbons in fluvial transport were determined at the Susquehanna, Potomac, and James River fall lines for the period of March 1992 through February 1993. Together these rivers account for ca. 75% of the freshwater inflow to the bay from fluvial sources. Sampling was conducted monthly during base flow conditions and during all major storm events. Analysis of nanogram and picogram per liter concentrations of the organic contaminants was performed for both the dissolved and particulate phases of the surface water samples. Daily fluvial loads were calculated using an iterative-increment method from concentration and discharge data, and the resulting daily load estimates were summed to provide annual loads. Loads contributed by the three tributaries from March 1992 through February 1993 were 6.9 metric tons for the organo-N/P pesticides, 0.73 metric tons for the OC compounds and PCBs, and 1.2 metric tons for the PAH. Preliminary comparisons show that loads from fluvial transport are generally greater than other sources for most contaminants except PAH, where atmospheric deposition and urban runoff contribute greater loads of some compounds.

  4. Fluvial processes in eastern Hellas Planitia, Mars - Insights from crater counts

    NASA Astrophysics Data System (ADS)

    Zuschneid, W.; van Gasselt, S.

    2014-04-01

    With a diameter of 2,300 km and a depth of more than 8,000 m, the Hellas basin is one of the major geomorphic and topographic features in the southern Martian hemisphere. It has been acting as a depositional sink since its formation 4 Ga ago [1] and has been the location of a wide variety of geologic processes. In this ongoing study, we investigated the stratigraphy of fluvial features in the eastern Hellas region on Mars, focusing on apparently young fluvial depositional areas in the Dao and Harmakhis Valles region and on the eastern plains within the Hellas basin. The region connecting Hesperia Planum with Hellas Planitia is characterized by a patchwork of remnant massifs protruding through a set of plains units of varying morphology and surface texture, indicating a diverse and eventful geologic history. A variety of geologic processes has been observed, from the basin-forming Hellas impact, widespread plainsforming and central vent volcanism [2,3] to fluvial and cold climate processes [3,4]. In order to analyze the stratigraphy, we performed crater counts for selected areas to obtain absolute ages for young areas formed by fluvial processes. We also obtained a lower limit for the age of major fluvial processes.

  5. Neotectonics and fluvial geomorphology of the Northern Sinai Peninsula

    NASA Astrophysics Data System (ADS)

    Kusky, T.; El-Baz, F.

    2000-08-01

    Large anticlinal ridges of Jurassic-Tertiary limestone in the northern Sinai Peninsula are part of the Syrian Arc Fold Belt, parts of which have been active intermittently from Late Cretaceous through the present. Recent uplift of the Syrian Arc Fold Belt is supported by quantitative indices of active tectonics including low values of mountain front sinuosity and, by recent seismicity, extending southwest past Cairo into the Fayoum Depression. The northern Sinai Desert has a climate similar to that of the adjacent part of the eastern Sahara. Sand sheets and dune fields cover its northwestern part, which is a depression extending from the Suez Canal to Wadi El-Arish. Numerous dry channels of palaeorivers and streams lead into this depression, where several temporary palaeolakes and flood overbank deposits have been identified. Some of the temporary pluvial palaeolakes developed behind natural dams formed by folds of the Syrian Arc, whereas others filled deeply-eroded fault traces. Migration of sand dunes may have blocked some channels, but the location of the dunes seems to be controlled by Recent uplift of parts of the fold belt, with the dunes residing in synclinal depressions and adjacent to fault scarps. The palaeolakes are correlated more with structures than with active dune fields. Wadi El-Arish abandoned a channel west of its present-day course, perhaps because of recent growth and uplift of the Gebel Halal Fold. This abandonment was synchronous with down-cutting of a gorge through Gebel Halal, which follows conjugate faults formed during uplift of an anticline. The presence of standing water during wetter climates in the past is supported by silt deposits and archaeological evidence of previous human habitation. The newly identified lake margin and fluvial sediments could be important targets for studying early-modern human and Neanderthal activities. In the eastern Sahara, cycles of pluvial periods that date back 320,000 years appear to correspond to interglacial stages. These indicate major global climate changes resulting in alternation of wet and dry climate episodes, which interplayed with local tectonic uplift to dramatically change the physiography of the northern Sinai.

  6. Cauvery River: Late Quaternary Fluvial Process and landforms

    NASA Astrophysics Data System (ADS)

    Stalin, Manjula; Achyuthan, Hema

    2014-05-01

    The Cauvery river basin from Hogenakkal to Thiruchirapalli, Tamil nadu, lies between 10o16' N to 11o30' N latitude and longitude 78o45' E to 79o51'E as demarcated in the survey of Indian topographical maps and draining a total area about 27,700 square miles. In this study, remote sensing imageries supported by topomaps and photo geological maps in relation to the structural configuration of the Cauvery basin, geodynamics and sedimentology are presented. Previous studies revealed that Cauvery river had earlier flowed in east to west direction along the Hogenekkal transverse fault to Erode and also controlled by minor fault systems. Three major palaeochannel systems, all branching off Cauvery, such as Hogenekkal- Kaveri pattinam along the Stanley reservoir, Harur a tract of Ponnaiyar river and Dharmapuri- Tiruchirapalli plains, indicates that the Cauvery river is structurally controlled and has changed its courses in the past due to neotectonic movements. The major tributaries draining along the district of Dharmapuri and Thiruchirapalli regions are Ayyar and Uppar in the north and Koraiyar in the south. The geology of the drainage basin is predominantly formed sculpting the Precambrian rocks, principally the Dharwars, Peninsular granitic gneiss, Charnockites and the Closepet granite and in general, the drainage pattern is dendritic in nature. Geologically, the Cauvery River is influenced by a major structural depression in the southern part of the Dharwar dome granulite belt. However the drainage pattern is largely sub-parallel and parallel when the river is flowing over the Cretaceous sedimentary rocks of Thiruchirapalli. Cauvery river undergoing uplift is reveals bedrock channel weathering and erosion, narrow and incised valleys with the occurrence of over steepened lower reaches of the tributaries and hanging valleys. In the present study the tectonic controls on this river were evaluated on the basis of the longitudinal profiles, morphotectonic of active tectonics, and fluvial records. The occurrence of low channel gradients, prominent hanging valleys, narrow bedrock and rapid erosion in middle portion of the Cauvery river indicate strong bedrock channel erosion. Drainage density and length of overland flow positively correlated with each other and the relationships are significant at 85% level. In this presentation detailed morphometric analysis supported by field date are presented.

  7. FLUVSIM: a program for object-based stochastic modeling of fluvial depositional systems

    NASA Astrophysics Data System (ADS)

    Deutsch, C. V.; Tran, T. T.

    2002-05-01

    This paper presents a FORTRAN program for hierarchical object-based modeling of complex fluvial facies. Unique features of this program include (1) a simple approach to place channel, levee, and crevasse sands within a matrix of floodplain shales, (2) templates for fast rastering of fluvial facies objects, leading to fast CPU times, and (3) the use of simulated annealing and non-random perturbation rules for conditioning to extensive soft facies-proportion data and local well data. Object-based modeling techniques are widely applicable to modeling fluvial depositional systems. Public domain software for such modeling is uncommon and inflexible with respect to the variety of conditioning data that can be handled. Commercial software is costly and also of limited flexibility. The fluvsim program overcomes many of these limitations with an accessible research code.

  8. Quantification of fluvial bedload transport in glacier-connected steep mountain catchments in western Norway

    NASA Astrophysics Data System (ADS)

    Beylich, Achim A.; Laute, Katja

    2015-04-01

    Contemporary fluvial bedload transport rates are still very difficult to measure and, as a result of this, in many sites only quantitative data on fluvial suspended and solute transport are included in sediment budget studies carried out for defined drainage basin systems. During the years 2010-2013 detailed field measurements with portable impact sensors as a non-invasive technique for indirectly determining fluvial bedload transport intensity were conducted in two instrumented drainage basin systems (Erdalen and Bødalen) in the fjord landscape in western Norway. The collected impact sensor field data were calibrated with laboratory flume experiments, and the data from the impact sensor field measurements and the flume experiments were combined with field data from continuous discharge monitoring, repeated surveys of channel morphometry and sediment texture, particle tracer measurements, Helley-Smith samplings, underwater video filming and biofilm analyses. The combination of methods and techniques applied provides insights into the temporal variability and intensity of fluvial bedload transport in the selected mountain streams of both drainage basin systems. The conducted analysis of fluvial bedload dynamics in different defined subsystems of Erdalen (79.5 km2) and Bødalen (60.1 km2) provides information on (i) detectable relevant sediment sources, (ii) instream channel storage of bedload material, (iii) spatiotemporal variability and controls of bedload transport rates and bedload yields, and (iv) the absolute and relative importance of fluvial bedload transport within the sedimentary budgets of these steep cold climate mountain catchments. Rockfalls, snow avalanches, stream channel bank erosion, and fluvial transfers through small tributaries draining slope systems are relevant sediment sources for fluvial bedload transport in the main stream channels, whereas the main outlet glaciers in both catchment systems are not of importance as all bedload material delivered directly from these outlet glaciers is trapped within proglacial lakes. Snow avalanches are the most important sediment source in Erdalen, whereas fluvial transfers through small tributaries followed by snow avalanches are most important in Bødalen. Narrow valleys within both drainage basin systems are characterized by a higher intensity of slope-channel coupling and display higher rates of sediment supply from slopes into main stream channels than wider valleys. Longer-term, instream channel storage is not of great importance in the steep Bødalen catchment but currently plays an important role within the Erdalen drainage basin, which is characterized by a stepped longitudinal main valley bottom profile favoring deposition of bedload material within the less steep main channel reaches. The computed mean annual bedload yields (2010-2013) are 2.4 t km-2y-1 for the entire Erdalen and 13.3 t km-2y-1 for the entire Bødalen, which are comparably low values for steep and partly glacierized catchment systems. Because of supply-limited conditions, the intensity of fluvial bedload transport is generally more related to the availability of sediments than to channel discharge. Fluvial bedload transport accounts for about one-third of the total fluvial transport in both drainage basin systems.

  9. 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.

  10. Metabolism of mineral-sorbed organic matter and microbial lifestyles in fluvial ecosystems

    NASA Astrophysics Data System (ADS)

    Hunter, William Ross; Niederdorfer, Robert; Gernand, Anna; Veuger, Bart; Prommer, Judith; Mooshammer, Maria; Wanek, Wolfgang; Battin, Tom J.

    2016-02-01

    In fluvial ecosystems mineral erosion, carbon (C), and nitrogen (N) fluxes are linked via organomineral complexation, where dissolved organic molecules bind to mineral surfaces. Biofilms and suspended aggregates represent major aquatic microbial lifestyles whose relative importance changes predictably through fluvial networks. We tested how organomineral sorption affects aquatic microbial metabolism, using organomineral particles containing a mix of 13C, 15N-labeled amino acids. We traced 13C and 15N retention within biofilm and suspended aggregate biomass and its mineralization. Organomineral complexation restricted C and N retention within biofilms and aggregates and also their mineralization. This reduced the efficiency with which biofilms mineralize C and N by 30% and 6%. By contrast, organominerals reduced the C and N mineralization efficiency of suspended aggregates by 41% and 93%. Our findings show how organomineral complexation affects microbial C:N stoichiometry, potentially altering the biogeochemical fate of C and N within fluvial ecosystems.

  11. 75 FR 21034 - Notice of Availability of Record of Decision for the Agua Fria National Monument and Bradshaw...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-22

    ... Bureau of Land Management Notice of Availability of Record of Decision for the Agua Fria National... Agua Fria National Monument and Bradshaw-Harquahala Planning Area, located in central Arizona. The... occupied or used portions of the planning area during prehistoric or historic times. The Agua Fria...

  12. Contrasting fluvial styles of the Paraguay River in the northwestern border of the Pantanal wetland, Brazil

    NASA Astrophysics Data System (ADS)

    Assine, Mario Luis; Silva, Aguinaldo

    2009-12-01

    The Upper Paraguay drainage basin is situated mainly in west-central Brazil, near the Bolivian border. Flowing from north to south, the Paraguay is the trunk river of an alluvial depositional tract characterized by complex geomorphologic zonation that resulted from an intricate geologic evolution since the Late Pleistocene. This paper focuses on the geomorphology of the Paraguay River at the northwestern border of the Pantanal wetland, where two broad geomorphologic zones were distinguished. North from the Pantanal wetland, the Paraguay River flows in an aggradational fluvial plain, 5 km wide and incised into older alluvial deposits. The river exhibits a meandering style over most of its course, but sinuosity drops from 2.2 to 1.1 near the northwest border of the Pantanal wetland where the river has been forming the Paraguay fluvial megafan since the Late Pleistocene. The river deflects 90° eastward at the entrance into the Pantanal, changing its fluvial style because of a progressive loss of confinement downstream of the point where the river reaches lowland plains. The river becomes more sinuous, adopts a distributary pattern within the wetland and brings about the creation of the modern depositional lobe characterized by higher topographic gradient and active sedimentation likely linked to increased accommodation space allowing progradation. Fluvial discharge diminishes in the Pantanal wetland because of channel overbank flow during the rainy season and frequent levee crevassing. Avulsion belts and channel-levee complex are preserved on the floodplain as relict forms. South of the convergence of the two main channels that define the Taiamã Island, a loss of gradient marks the base of the depositional lobe. Further downstream, the Paraguay River returns to a meandering fluvial style, but crossing a large fluvial plain populated by hundreds of small lakes and seasonally flooded that characterizes the Pantanal wetland.

  13. 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.

  14. Integrated assessment of fluvial and pluvial flood hazards in the city of Salzburg, Austria

    NASA Astrophysics Data System (ADS)

    Breinl, Korbinian

    2014-05-01

    Urban flooding can have various sources including floods from a river ('fluvial flooding'), from heavy rainfall usually from convective storms ('pluvial flooding') or from high tides ('storm surge'). Although awareness of pluvial flooding in the scientific community and among policymakers has been increasing, the term 'flooding' is still often seen as a phenomenon explicitly related to a river. Previous research primarily focused on fluvial flooding, with only very recent literature dealing with pluvial flooding. As a result, there are established methods to assess the hazards from fluvial floods, and a smaller number focusing on pluvial floods. Much less work has been conducted on integrated flood hazard assessment taking into account various types of flood hazards. In this work, an integrative, probabilistic modelling framework was developed to assess the urban flood hazard from fluvial and pluvial flooding in the city of Salzburg (Austria). The framework consists of a stochastic multi-site weather generator, which provides input for the hydrological model HBV. In the city of Salzburg, a kNN algorithm converts the simulated mean discharge into peak discharge as well as daily into sub-daily precipitation. The time series generated in this way make the identification of fluvial events (peak discharge) and pluvial events (sub-daily precipitation) possible. The kNN algorithm inherently considers weather situations to ensure a reasonable disaggregation of daily precipitation. Critical thresholds of pluvial flood events are empirically derived from damage data provided by a local insurer as well as action plans from the local fire service. The modelling framework is then applied to examine the probability of the two single flood hazards, as well as the probability of simultaneous pluvial-fluvial flood events.

  15. Fluvial Channel Networks as Analogs for the Ridge-Forming Unit, Sinus Meridiani, Mars

    NASA Technical Reports Server (NTRS)

    Wilkinson, M. J.; du Bois, J. B.

    2010-01-01

    Fluvial models have been generally discounted as analogs for the younger layered rock units of Sinus Meridiani. A fluvial model based on the large fluvial fan provides a possibly close analog for various features of the sinuous ridges of the etched, ridge-forming unit (RFU) in particular. The close spacing of the RFU ridges, their apparently chaotic orientations, and their organization in dense networks all appear unlike classical stream channel patterns. However, drainage patterns on large fluvial fans low-angle, fluvial aggradational features, 100s of km long, documented worldwide by us provide parallels. Some large fan characteristics resemble those of classical floodplains, but many differences have been demonstrated. One major distinction relevant to the RFU is that channel landscapes of large fans can dominate large areas (1.2 million km2 in one S. American study area). We compare channel morphologies on large fans in the southern Sahara Desert with ridge patterns in Sinus Meridiani (fig 1). Stream channels are the dominant landform on large terrestrial fans: they may equate to the ubiquitous, sinuous, elongated ridges of the RFU that cover areas region wide. Networks of convergent/divergent and crossing channels may equate to similar features in the ridge networks. Downslope divergence is absent in channels of terrestrial upland erosional landscapes (fig. 1, left), whereas it is common to both large fans (fig. 1, center) and RFU ridge patterns (fig 1, right downslope defined as the regional NW slope of Sinus Meridiani). RFU ridge orientation, judged from those areas apparently devoid of impact crater control, is broadly parallel with the regional slope (arrow, fig. 1, right), as is mean orientation of major channels on large fans (arrow, fig. 1, center). High densities per unit area characterize fan channels and martian ridges reaching an order of magnitude higher than those in uplands just upstream of the terrestrial study areas fig. 1. In concert with several other regional features, these morphological similarities argue for the RFU as a possibly fluvial unit.

  16. A 100 ka record of fluvial activity in the Fitzroy River Basin, tropical northeastern Australia

    NASA Astrophysics Data System (ADS)

    Croke, Jacky; Jansen, John D.; Amos, Kathryn; Pietsch, Timothy J.

    2011-06-01

    This study reports the nature and timing of Quaternary fluvial activity in the Fitzroy River basin, which drains a diverse 143,000 km 2 area in northeastern Queensland, before discharging into the Great Barrier Reef Marine Park. The catchment consists of an extensive array of channel and floodplain types that we show have undergone large-scale fluvial adjustment in-channel planform, geometry and sinuosity. Optically stimulated luminescence (OSL) dating of quartz sediments from fifteen (3-18 m) floodplain cores throughout the basin indicates several discrete phases of active bedload activity: at 105-85 ka in Marine Isotope Stage (MIS) 5, at 50-40 ka (MIS 3), and at 30-10 ka (MIS 3/2). The overall timing of late Quaternary fluvial activity correlates well with previous accounts from across Australia with rivers being primarily active during interstadials. Fluvial activity, however, does not appear to have been synchronous throughout the basin's major sub-catchments. Fluvial activity throughout MIS 2 (i.e. across the Last Glacial Maximum) in the meandering channels of the Fitzroy correlates well with regional data in tropical northeastern Queensland, and casts new light on the river response to reduced rainfall and vegetation cover suggested by regional palaeoclimate indicators. Moreover, the absence of a strong Holocene signal is at odds with previous accounts from elsewhere throughout Australia. The latitudinal position of the Fitzroy across the Tropic of Capricorn places this catchment at a key location for elucidating the main hydrological drivers of Quaternary fluvial activity in northeastern Australia, and especially for determining tropical moisture sources feeding into the headwaters of Cooper Creek, a major river system of the continental interior.

  17. Deep instability of deforested tropical peatlands revealed by fluvial organic carbon fluxes.

    PubMed

    Moore, Sam; Evans, Chris D; Page, Susan E; Garnett, Mark H; Jones, Tim G; Freeman, Chris; Hooijer, Aljosja; Wiltshire, Andrew J; Limin, Suwido H; Gauci, Vincent

    2013-01-31

    Tropical peatlands contain one of the largest pools of terrestrial organic carbon, amounting to about 89,000 teragrams (1?Tg is a billion kilograms). Approximately 65 per cent of this carbon store is in Indonesia, where extensive anthropogenic degradation in the form of deforestation, drainage and fire are converting it into a globally significant source of atmospheric carbon dioxide. Here we quantify the annual export of fluvial organic carbon from both intact peat swamp forest and peat swamp forest subject to past anthropogenic disturbance. We find that the total fluvial organic carbon flux from disturbed peat swamp forest is about 50 per cent larger than that from intact peat swamp forest. By carbon-14 dating of dissolved organic carbon (which makes up over 91 per cent of total organic carbon), we find that leaching of dissolved organic carbon from intact peat swamp forest is derived mainly from recent primary production (plant growth). In contrast, dissolved organic carbon from disturbed peat swamp forest consists mostly of much older (centuries to millennia) carbon from deep within the peat column. When we include the fluvial carbon loss term, which is often ignored, in the peatland carbon budget, we find that it increases the estimate of total carbon lost from the disturbed peatlands in our study by 22 per cent. We further estimate that since 1990 peatland disturbance has resulted in a 32 per cent increase in fluvial organic carbon flux from southeast Asia--an increase that is more than half of the entire annual fluvial organic carbon flux from all European peatlands. Our findings emphasize the need to quantify fluvial carbon losses in order to improve estimates of the impact of deforestation and drainage on tropical peatland carbon balances. PMID:23364745

  18. 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.

  19. Fluvial Features on Titan: New Insights from Morphology and Hydraulic Modeling

    NASA Astrophysics Data System (ADS)

    Burr, D. M.; Adamkovics, M.; Baker, V. R.; Collins, G. C.; Howard, A. D.; Irwin, R. P.; Lamb, M. P.; Moore, J. M.; Perron, T.; Sklar, L. S.; Drummond, S.; Black, B. A.

    2011-12-01

    Fluvial features on Titan have been inferred in data from surface imaging instruments on the Cassini spacecraft (Image Science Subsystem, ISS; Visual and Infrared Mapping Spectrometer, VIMS; Cassini Titan RADAR Mapper, RADAR) and the Huygens probe (Descent Imager/Spectral Radiometer, DISR). Interpretations of these features using terrestrial classifications and analogs offer insight into their formative processes and controls. Networks may be classified using a modified version of an algorithm developed from terrestrial drainage networks. As each network class carries different landscape-scale implications, these classifications provide information on the regional geology. For example, rectangular networks, the dominant drainage pattern on Titan, imply structural control. Individual fluvial features provide more localized information and may be classified using simple plan view parameters of relative width, length, and RADAR albedo into six descriptive classes, which have multiple hypothesized interpretations. At the highest resolution observations of Titan, DISR images show uplands dissected by river valley networks, which are not visible in lower resolution SAR data. This comparison of DISR and SAR images suggests (1) that some fluvial features observed in SAR data elsewhere may be river valleys instead of channels as previously denoted, and (2) that other uplands on Titan may likewise be fluvially dissected below SAR resolution. Crenulated (mountainous, hummocky) terrain is hypothesized here to have such sub-resolution fluvial dissection, based on (a) emergent fluvial features at lakes and (b) terrestrial data over dissected landscapes that illustrate the underrepresentation of fluvial dissection in SAR data. Fluvial deposits occur in (paleo)lake basins and on SAR-dark plains. For fully turbulent flow over a rough boundary, hydraulic equations are insensitive to fluid viscosity, so that terrestrial formulations are applicable to Titan flow when the difference in material properties (i.e., gravity, fluid density and viscosity, sediment densities) is accounted for. However, for low Reynolds number flow over a smooth boundary, knowledge of fluid kinematic viscosity is necessary for quantitative predictions of flow rates. Sediment movement and bedform development are also influenced by material properties. The reduced sediment density and fluid viscosity for Titan largely balance each other out, so that the predominant effect is the lower gravity, which results in movement and bedforms occurring at lower bed shear stress on Titan than on Earth. However, scaling bedrock erosion is hampered by uncertainties regarding Titan material properties.

  20. Debris Flow Control on Fluvial Hanging Valley Formation in the South Fork Eel River, CA

    NASA Astrophysics Data System (ADS)

    Deshpande, N.; Perkins, J.; Finnegan, N. J.

    2012-12-01

    An understanding of how base level signals are transmitted into landscapes is fundamental to interpreting river long profiles in tectonically active settings. Fluvial hanging valleys, locations where waves of incision have apparently arrested at tributary junctions, suggest that base level propagation is an unsteady process in many settings. A recent hypothesis (Wobus et al., 2006) explains the formation of fluvial hanging valleys via an instability in the saltation abrasion model of Sklar and Dietrich (2004). At locations where small steep tributaries join trunk streams, tributary incision rates can actually decrease with increasing channel slope when subjected to downstream base-level fall. However, we note that in mountainous river networks steep tributaries also commonly convey debris flows into trunk channels. Since these tributary junctions mark the upstream limit of channels whose beds are mobilized on a regular basis during flood events, here we hypothesize that transitions from fluvial to debris flow channels control the location of fluvial hanging valleys. To test our hypothesis, we exploit a natural experiment in base level fall and landscape evolution along the South Fork Eel River, which is argued to be responding to an increase in rock uplift rate associated with the passage of the Mendocino Triple Junction. In order to separate debris flow channels from fluvial channels, we use airborne laser swath mapping (ALSM) to quantify channel slopes and concavities. In our analysis, concavity data are noisy and represent a poor metric for determination of debris flow channels. In lieu of this, we choose a more straightforward metric of channel slope to discriminate where debris flows occur on the landscape. We find that, on average, fluvial hanging valleys are only present in tributaries with average gradients above 0.10, consistent with empirical determinations of the gradient at which debris flow channels transition to fluvial channels (0.03-0.10). Field observations in selected tributaries confirm our interpretation of the topographic analysis and thereby lend support to our hypothesis. Our results contradict Wobus et al. (2006) who find through a topographic analysis of tributaries in the eastern Central Range of Taiwan that channels exhibiting a signature of debris flows in slope-area space do not form hanging valleys or display evidence of a transient response. Possible explanations for this discrepancy lie in the scale of topographic data used in the respective analyses, as well as the spatial scale of the study areas themselves. Regardless, our observations of systematically steeper slopes (above the debris flow threshold) upstream of fluvial hanging valleys along the South Fork Eel River, CA suggest a process transition may be responsible for the morphologic changes observed here.

  1. Diagenetic history of fluvial and lacustrine sandstones of the Hartford Basin (Triassic Jurassic), Newark Supergroup, USA

    NASA Astrophysics Data System (ADS)

    Wolela, A. M.; Gierlowski-Kordesch, E. H.

    2007-04-01

    The early introduction of clays into continental sandstones has been attributed to mechanical infiltration by percolation of clay-rich surface waters into grain framework or cutans formed from pedogenic processes. The discovery of pedogenic mud aggregates as traction-load mud in ancient fluvial deposits suggests that permeability and porosity of terrigenous sandstones can be influenced at deposition and control early diagenetic patterns. This study compares diagenesis in fluvial (subaerially exposed) sandstones with lacustrine (subaqueous) sandstones in a Triassic-Jurassic continental rift basin (Hartford Basin, Newark Supergroup). Diversity of diagenetic minerals and sequence of diagenetic alteration can be directly related to depositional environment. The fluvial sandstones in the New Haven Arkose, East Berlin Formation, and Shuttle Meadow Formation of the Hartford Basin are dominated by concretionary calcite and early calcite cement, infiltrated clays (illite-smectite), pedogenic mud aggregates (smectite and illite-smectite), grain coating clays (illite/hematite, illite-chlorite/hematite), quartz overgrowths, late stage carbonate cements (calcite, ferroan calcite), pore-filling clays (illite, kaolinite with minor amounts of smectite, smectite-chlorite, illite-smectite) and hematite. However, pedogenic processes in these fluvial sandstones retarded the development of quartz and feldspar overgrowths, and carbonate authigenesis, as well as the quality of diagenetically enhanced porosity. Dark gray-black lacustrine (subaqueous) sandstones and mudrocks in the East Berlin and Shuttle Meadow Formations are dominated by pyrite, concretionary dolomite and early dolomite cement, radial grain coating clays (smectite-chlorite, illite-smectite), late stage carbonate cements (dolomite, ferroan dolomite, ankerite), albite and pore-filling clays (smectite-chlorite, illite-smectite, illite-chlorite). Clay minerals exist as detrital, mechanically infiltrated, and neoformed clay. The fluvial sandstones in the New Haven Arkose are dominated by illite. The East Berlin and Shuttle Meadow Formations are dominated by illite in the fluvial sequences and smectite-chlorite and illite-smectite in the lacustrine sandstones. Dolomite, ferroan dolomite, and ankerite are restricted to lacustrine sandstones, whereas calcite and ferroan calcite to fluvial sandstones. Albite predominantly precipitated in lacustrine rather than fluvial environments through intergranular dissolution of plagioclase by acidic meteoric water, dissolution of unstable mafic minerals, and sodium-rich brines and evaporites developed from groundwater. Albitization and carbonate cementation are the most pronounced late stage diagenetic processes affecting both types of Hartford sandstones.

  2. Gone But Not Forgotten: The Aeolian Modification of Fluvial Surfaces on Mars: Preliminary Results from Central Australia

    NASA Technical Reports Server (NTRS)

    Bourke, M. C.

    2003-01-01

    MOC images indicate that aeolian ridges may mask and even obliterate primary depositional surfaces on Mars. This modification increases the difficulty in mapping the recent geological history of the planet. An analogue study in central Australia demonstrates how patterns in aeolian dunes, formed over abandoned fluvial surfaces, can be used to detect buried fluvial features.

  3. Selective deposition response to aeolian-fluvial sediment supply in the desert braided channel of the Upper Yellow River, China

    NASA Astrophysics Data System (ADS)

    Wang, H.; Jia, X.

    2015-02-01

    Rivers flow across aeolian dunes and develop braided stream channels. Both aeolian and fluvial sediment supplies regulate sediment transport and deposition in such a cross-dune braided river. Here we show a significant selective deposition in response to both aeolian and fluvial sediment supplies in the Ulan Buh desert braided channel. This selective deposition developed by the interaction between the flows and the Aeolian-fluvial sediment supplies, making the coarser sediments (> 0.08 mm) from aeolian sand supply and bank erosion to accumulate in the channel center and the finer fluvial sediments (< 0.08 mm) to be deposited on the bar and floodplain surfaces and forming a coarser-grained thalweg bed bounded by finer-grained floodplain surfaces. This lateral selective deposition reduces the downstream sediment transport and is a primary reason for the formation of "above-ground river" in the braided reach of the Upper Yellow River in response to aeolian and fluvial sediment supplies.

  4. Reciprocal interactions and adjustments between fluvial landforms and vegetation dynamics in river corridors: A review of complementary approaches

    NASA Astrophysics Data System (ADS)

    Corenblit, Dov; Tabacchi, Eric; Steiger, Johannes; Gurnell, Angela M.

    2007-09-01

    Until recently, one-way relationships between flow dynamics, geomorphology and plant ecology were considered dominantly when studying the functioning of river systems, whereby fluvial landforms and hydrogeomorphic processes drive the evolution of riparian plant communities. However, biological communities may significantly control geomorphic processes and have strong impacts on landform dynamics. In order to fully identify the processes linked to river dynamics (changes in time and space of fluvial landforms and associated plant communities), conceptual multidisciplinary progress is clearly needed. To understand the mutual interactions and feedbacks between fluvial landforms and vegetation community dynamics, this paper presents a detailed literature review of fluvial geomorphology, riparian plant ecology and hydraulic engineering knowledge. The historical and recent development of ecological plant succession theory toward the integration of hydrogeomorphic disturbances is discussed as well as the integration of vegetation within geomorphology as a significant landform control factor, incorporating both hydrogeomorphic controls on riparian vegetation dynamics and mechanical impacts of vegetation structures on flow properties and sediment dynamics. Recent progress in ecology, hydraulic engineering and fluvial geomorphology emphasises interdependence between biological and physical forms and processes. Based on this literature review, a 'fluvial biogeomorphic succession' concept is proposed to link fluvial landform and riparian vegetation community evolution within a bi-directional model. The succession of fluvial landforms and associated vegetation communities is composed of four main critical phases that represent a shift in the relative dominance of hydrogeomorphic and ecological processes as a response to biostabilisation and passive bioconstruction processes. The positive feedbacks associated with this shift lead to the development of characteristic biogeomorphic structures such as vegetated banks, islands or floodplains, which are moderated by the biogeomorphic functional roles of 'ecosystem engineers' that induce or reinforce the positive feedbacks. This fluvial biogeomorphic succession concept relates the natural Darwinian selection and ecological succession theories to fluvial geomorphology.

  5. Phosphorus and nitrogen loading depths in fluvial sediments following manure spill simulations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Manure spills that enter streams can devastate the aquatic ecosystem. The depth of nitrogen (N) and phosphorus (P) loading in fluvial sediments following a manure spill have not been documented. Thus, the objectives of this study were (i) to determine the depth of N and P contamination as a result o...

  6. Volcanogenic fluvial-lacustrine environments in iceland and their utility for identifying past habitability on Mars.

    PubMed

    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

  7. Fluvial rainbow trout contribute to the colonization of steelhead (Oncorhynchus mykiss) in a small stream

    USGS Publications Warehouse

    Weigel, Dana E.; Connolly, Patrick J.; Powell, Madison S.

    2013-01-01

    Life history polymorphisms provide ecological and genetic diversity important to the long term persistence of species responding to stochastic environments. Oncorhynchus mykiss have complex and overlapping life history strategies that are also sympatric with hatchery populations. Passive integrated transponder (PIT) tags and parentage analysis were used to identify the life history, origin (hatchery or wild) and reproductive success of migratory rainbow/steelhead for two brood years after barriers were removed from a small stream. The fluvial rainbow trout provided a source of wild genotypes to the colonizing population boosting the number of successful spawners. Significantly more parr offspring were produced by anadromous parents than expected in brood year 2005, whereas significantly more parr offspring were produced by fluvial parents than expected in brood year 2006. Although hatchery steelhead were prevalent in the Methow Basin, they produced only 2 parr and no returning adults in Beaver Creek. On average, individual wild steelhead produced more parr offspring than the fluvial or hatchery groups. Yet, the offspring that returned as adult steelhead were from parents that produced few parr offspring, indicating that high production of parr offspring may not be related to greater returns of adult offspring. These data in combination with other studies of sympatric life histories of O. mykiss indicate that fluvial rainbow trout are important to the conservation and recovery of steelhead and should be included in the management and recovery efforts.

  8. A Chemical Treatment to Reduce P Desorption From Manure Exposed Fluvial Sediments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The current remediation methods for manure spills that have reached surface waters give no attention to the P enriched ditch sediments that remain in the fluvial system and continue to impair the water column. Consequently, no method exists to treat P contaminated sediments to reduce their ability ...

  9. Study on detailed geological modelling for fluvial sandstone reservoir in Daqing oil field

    SciTech Connect

    Zhao Hanqing; Fu Zhiguo; Lu Xiaoguang

    1997-08-01

    Guided by the sedimentation theory and knowledge of modern and ancient fluvial deposition and utilizing the abundant information of sedimentary series, microfacies type and petrophysical parameters from well logging curves of close spaced thousands of wells located in a large area. A new method for establishing detailed sedimentation and permeability distribution models for fluvial reservoirs have been developed successfully. This study aimed at the geometry and internal architecture of sandbodies, in accordance to their hierarchical levels of heterogeneity and building up sedimentation and permeability distribution models of fluvial reservoirs, describing the reservoir heterogeneity on the light of the river sedimentary rules. The results and methods obtained in outcrop and modem sedimentation studies have successfully supported the study. Taking advantage of this method, the major producing layers (PI{sub 1-2}), which have been considered as heterogeneous and thick fluvial reservoirs extending widely in lateral are researched in detail. These layers are subdivided into single sedimentary units vertically and the microfacies are identified horizontally. Furthermore, a complex system is recognized according to their hierarchical levels from large to small, meander belt, single channel sandbody, meander scroll, point bar, and lateral accretion bodies of point bar. The achieved results improved the description of areal distribution of point bar sandbodies, provide an accurate and detailed framework model for establishing high resolution predicting model. By using geostatistic technique, it also plays an important role in searching for enriched zone of residual oil distribution.

  10. A mechanistic detachment rate model to predict soil erodibility due to fluvial and seepage forces

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The erosion rate of cohesive soils is typically computed using an excess shear stress model based on the applied fluvial shear stress. However, no mechanistic approaches are available for incorporating additional forces such as localized groundwater seepage forces into the excess shear stress model...

  11. 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

  12. Misconceptions about mechanical and fluvial erosional strength: implications to streambank stability

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The central objective of this study was to highlight the differences in magnitude between the mechanical and fluvial streambank erosional strength measures of with the purpose of developing a more comprehensive bank stability analysis. Mechanical erosion and ultimately failure signifies the general ...

  13. Quantifying the seasonal variations in fluvial and eolian sources of terrigenous material to Cariaco Basin, Venezuela

    NASA Astrophysics Data System (ADS)

    Elmore, Aurora C.; Thunell, Robert C.; Styles, Richard; Black, David; Murray, Richard W.; Martinez, Nahysa; Astor, Yrene

    2009-02-01

    The varved sediments that accumulate in the Cariaco Basin provide a detailed archive of the region's climatic history, including a record of the quantity of fluvial and wind-transported material. In this study, we examine the sedimentological characteristics (clay mineralogy and grain size) of both surface sediments and sinking lithogenic material collected from sediment trap samples over a three-year period from 1997 to 2000. Data from biweekly sediment trap samples show a tri-modal particle size distribution, with prominent peaks at 2, 22 and 80 μm, indicating sediment contributions from both eolian and fluvial sources. The clay mineralogy of the water column samples collected from 1997 to 1999 also shows distinctive characteristics of eolian and fluvial material. An examination of surface sediment samples from the Cariaco Basin indicates that the Unare River is the main source of riverine sediments to the eastern sub-basin. By combining these sedimentological proxies, we estimate that ˜10% of the terrigenous material delivered to the Cariaco Basin is eolian, while ˜90% is fluvial. This represents an annual dust accumulation rate of ˜0.59 mg/cm 2/yr. Since aerosols are closely linked to climate variability, the ability to quantify paleo-dust fluxes using sedimentological characteristics will be a useful tool for future paleoclimate studies looking at sub-Saharan aridity and latitudinal migration of the Intertropical Convergence Zone.

  14. Mixed fluvial systems of Messak Sandstone, a deposit of Nubian lithofacies, southwestern Libya

    SciTech Connect

    Lorenz, J.C.

    1987-05-01

    The Messak Sandstone is a coarse to pebbly, tabular cross-bedded, Lower Cretaceous deposit of the widespread Nubian lithofacies. It was deposited at the northern edge of the Murzuq basin in southwestern Libya. Although the sedimentary record is predominantly one of braided fluvial systems, a common subfacies within the formation is interpreted to record the passage of straight-crested sand waves across laterally migrating point bars in sinuous rivers, similar to the pattern documented by Singh and Kumar on the modern Ganga and Yamuna Rivers. Because the sand waves were larger on the lower parts of the point bars, lateral migration created diagnostic thinning-upward, unidirectional cosets of tabular cross-beds as well as fining-upward, grain-size trends. Common, thick, interbedded claystones, deposited in associated paludal and lacustrine environments, and high variance in cross-bed dispersion patterns also suggest the local presence of sinuous fluvial systems within the overall braided regime. The Messak Sandstone contains some of the features that led Harms et al to propose an unconventional low-sinuosity fluvial environment for the Nubian lithofacies in Egypt, and the continuously high water levels of this model may explain channel-scale clay drapes and overturned cross-beds in the Messak. However, most of the Messak characteristics are incompatible with the low-sinuosity model, suggesting instead that the fluvial channels in the Murzuq basin alternated between braided and high-sinuosity patterns.

  15. Variables and potential models for the bleaching of luminescence signals in fluvial environments

    USGS Publications Warehouse

    Gray, Harrison J.; Mahan, Shannon

    2015-01-01

    Luminescence dating of fluvial sediments rests on the assumption that sufficient sunlight is available to remove a previously obtained signal in a process deemed bleaching. However, luminescence signals obtained from sediment in the active channels of rivers often contain residual signals. This paper explores and attempts to build theoretical models for the bleaching of luminescence signals in fluvial settings. We present two models, one for sediment transported in an episodic manner, such as flood-driven washes in arid environments, and one for sediment transported in a continuous manner, such as in large continental scale rivers. The episodic flow model assumes that the majority of sediment is bleached while exposed to sunlight at the near surface between flood events and predicts a power-law decay in luminescence signal with downstream transport distance. The continuous flow model is developed by combining the Beer–Lambert law for the attenuation of light through a water column with a general-order kinetics equation to produce an equation with the form of a double negative exponential. The inflection point of this equation is compared with the sediment concentration from a Rouse profile to derive a non-dimensional number capable of assessing the likely extent of bleaching for a given set of luminescence and fluvial parameters. Although these models are theoretically based and not yet necessarily applicable to real-world fluvial systems, we introduce these ideas to stimulate discussion and encourage the development of comprehensive bleaching models with predictive power.

  16. Flow resistance in natural, turbulent channel flows: The need for a fluvial fluid mechanics

    NASA Astrophysics Data System (ADS)

    Keylock, Christopher J.

    2015-06-01

    In fluvial environments, feedbacks among flow, bed forms, sediment, and macrophytes result in a complex fluid dynamics. The assumptions underpinning standard tools in hydraulics are commonly violated and alternative approaches must be formulated. I argue that we should question the assumption that classical notions in fluid mechanics provide the foundations for the techniques of the future. Recent work on turbulent dissipation, interscale modulation of the dynamics, intermittency, and the role of complex forcings is discussed. An agenda for future work is proposed that involves improving our characterization of complex forcings and developing better understanding of the behavior of the velocity gradient tensor in complex, fluvial environments. This leads to the formulation of modeling tools relevant to fluvial fluid mechanics, rather than a reliance on methods developed elsewhere. One avenue by which such methods might be developed is suggested based on the stretched spiral vortex as a baseline topology. This would result in a nonequilibrium model for turbulence that has greater potential to capture the dynamics in which we are interested. Although these ideas are raised in the context of a future fluvial fluid mechanics, they are applicable to any situation where turbulent flows are forced in complicated ways.

  17. Fluvial Degradation of the Highlands: The Terra Tyrrhena Region of Mars

    NASA Technical Reports Server (NTRS)

    Mest, S. C.; Crown, D. A.; Harbert, W.

    2002-01-01

    Geologic and geomorphic analyses of highland terrains reveal the effects of fluvial erosion by well-integrated valley networks. Hydrologic modeling using 128 pix/deg Mars Orbiting Laser Altimeter (MOLA) gridded topography is being done to quantitatively characterize these systems. Additional information is contained in the original extended abstract.

  18. Mixed fluvial systems of the Messak Sandstone, a deposit of the Nubian lithofacies, southwestern Libya

    NASA Astrophysics Data System (ADS)

    Lorenz, John C.

    1987-11-01

    The Messak Sandstone is a coarse-grained to pebbly, tabular-crossbedded deposit of the widespread nubian lithofacies. It was deposited during Late Jurassic and/or Early Cretaceous time at the northern edge of the Murzuq basin, in southwestern Libya. Although the sedimentary record is predominantly one of braided fluvial systems, a common subfacies within the formation is interpreted to record the passage of straight-crested sand waves across laterally migrating point bars in sinuous rivers, similar to parts of the modern Ganga and Yamuna rivers. Because the sand waves were larger on the lower parts of the point bar, lateral migration created diagnostic thinning-upward cosets of tabular crossbeds, as well as fining-upward grain-size trends. Common thick, interbedded claystones, deposited in associated paludal and lacustrine environments, and high variance in crossbed dispersion patterns, also suggest the local presence of sinuous fluvial systems within the overall braided regime. The Messak Sandstone contains some of the features that led to the proposal of an unconventional low-sinuosity fluvial environment for the Nubian lithofacies in Egypt, and the continuously high water levels of this model may explain channel-scale clay drapes and overturned crossbeds in the Messak. However, most of the Messak characteristics are incompatible with a low-sinuosity model, suggesting instead that the fluvial channels in the Murzuq basin alternated between braided and high-sinuosity channel patterns.

  19. 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.

  20. Sinus Meridiani Landing Site for Human Exploration —- A Mesoscale Fluvial System

    NASA Astrophysics Data System (ADS)

    Wilkinson, M. J.; McGovern, P. J.

    2015-10-01

    SW Sinus Meridiani is proposed as an EZ as seen through the lens of the still poorly recognized large fluvial fan model. Hematite distribution, regional and Miyamoto Crater sedimentary stacks, sediment inundation of craters, and the rover traverse path are suggested ROIs.

  1. "The Waters of Meridiani" - Further Support for a Fluvial Interpretation of the Ridged, Layered Units

    NASA Technical Reports Server (NTRS)

    Wilkinson, Justin; Kreslavsky, Misha

    2009-01-01

    A relatively unknown terrestrial fluvial environment, the mesoscale megafan, provides analogs for various Martian landscapes, including the etched unit (etched unit, Unite E of Arvidson et al., 2003; ridge-forming unit R of Edgett, 2005) of the Sinus Meridiani region on Mars. A global survey of Earth shows that megafans are very large partial cones of dominantly fluvial sediment with radii on the order of hundreds of km, and very low slopes. Responsible fluvial processes are sufficiently different from those of classical arid alluvial fans and deltas that it is useful to class megafans as separate features. The megafan model calls into question two commonly held ideas. 1. Earth examples prove that topographic basins per se are unnecessary for the accumulation of large sedimentary bodies. 2. River channels are by no means restricted to valleys (Meridiani sediments are termed a "valley-ed volume" of Edgett). These perspectives reveal unexpected parallels with features at Meridiani-several channel-like features that are widespread, mostly as ridges inverted by eolian erosion; channel networks covering thousands of sq km, especially on intercrater plains; and regional relationships of sediment bodies situated immediately downstream of highland masses. These all suggest that fluvial explanations are at least part of the Meridiani story.

  2. MODIFICATION OF PHOSPHORUS EXPORT FROM A CATCHMENT BY FLUVIAL SEDIMENT PHOSPHORUS INPUTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Phosphorus (P) export from agricultural watersheds can accelerate freshwater eutrophication. Landscape-based remedial measures can reduce edge-of-field P losses. However stream channel hydraulics and fluvial sediment properties can modify the forms and amounts of P exported by the time it reaches th...

  3. Legacies of Glacio-fluvial Interactions in the Finger Lakes, Central New York

    NASA Astrophysics Data System (ADS)

    Safran, E. B.; Fountain, A. G.

    2011-12-01

    The Finger Lakes region of central New York exhibits spectacular examples of the interplay between glacial and fluvial processes. The Finger Lakes themselves were carved by ice sheets and related subglacial hydrologic processes that enlarged, over-deepened, and reversed the drainage direction of pre-existing fluvial valleys. The region's famous gorges flank the glacial troughs and reflect ongoing fluvial adjustment to glacially driven base level variations. Modern tools of topographic analysis permit quantification of the imprint that glacial processes leave on fluvial form and process. Regionally, ice sheet erosion is maximized along the north end of the Seneca/Cayuga trough. Local relief ranges from ~100 m at the north end of Seneca and Cayuga lakes to 250-400 m on the southern ends of these lakes and on the smaller, flanking lakes (Keuka, Canandaigua, Skaneateles, Owasco). Concavity indices for lake-tributary stream profiles are predominantly in the range of -7 to 0, reflecting a convex initial form imposed by glacial processes, while normalized channel steepness (ksn) indices are generally under 40 (reference concavity of 0.45), reflecting the gentle gradients of the glacial uplands. Concavity index and ksn values are maximized (>0, and >75, respectively) along short segments at the downstream ends of the so-called interglacial or post-glacial gorge reaches, again maximized at the southern and peripheral parts of the Seneca/Cayuga trough. Finally, streams that cross former channel courses buried by subglacial debris typically have more numerous and/or more pronounced knickpoints and more concave long profile segments than streams that do not. In short, the legacy of glaciations from the regional to the reach scale appears to be driving patterns of fluvial response in the Finger Lakes.

  4. Fluvial responses to late Quaternary climate change in the Shiyang River drainage system, western China

    NASA Astrophysics Data System (ADS)

    Gao, Hongshan; Li, Zongmeng; Pan, Baotian; Liu, Fenliang; Liu, Xiaopeng

    2016-04-01

    As a drainage system located in arid western China, the Shiyang River, combined with considerable fluvial strata and landform information, provides an environmental context within which to investigate fluvial responses to late Quaternary climate change. Sedimentological analysis and optically stimulated luminescence (OSL) dating enabled us to reconstruct the processes and fluvial styles of three sedimentary sequences of the Shagou and Hongshui rivers in the Shiyang drainage system. Our results present a variety of river behaviors during the late Quaternary in these areas. In the upstream Shiyang River, Zhangjiadazhuang (ZJDZ) profile of the Shagou was dominated by aggradation and a meandering channel pattern at 10.6-4.2 ka, while a noticeable channel incision occurred at ~ 4.2 ka followed by lateral channel migration. In the downstream Shiyang River, Datugou (DTG) profile of the Hongshui was an aggrading meandering river from 39.7 to 7.2 ka while channel incision occurred at 7.2 ka. Another downstream profile, Wudunwan (WDW) of the Hongshui was also characterized by aggradation from 22.4 to 4.8 ka; however, its channel pattern shifted from braided to meandering at ~ 13 ka. A discernable downcutting event occurred at ~ 4.8 ka, followed by three channel aggradation and incision episodes prior to 1.8 ka. The last 1.8 ka has been characterized by modern channel and floodplain development. The fluvial processes and styles investigated have a close correlation with late Quaternary climate change in the Shiyang River drainage. During cold phases, the WDW reach was dominated by aggradation with a braided channel pattern. During warm phases, the rivers that we investigated were also characterized by aggradation but with meandering channel patterns. Channel incision events and changes of fluvial style occurred mainly during climate transitions.

  5. Geomorphic thresholds and complex response of fluvial systems - some implications for sequence stratigraphy

    SciTech Connect

    Wescott, W.A. )

    1993-07-01

    First-generation sequence stratigraphic models have dealt in a very rudimentary fashion with the response of fluvial systems to eustasy. A major element of presently accepted models is that rivers incise when sea level falls and aggrade during the ensuing rise. Geomorphic principles state that fluvial systems are complex, process-response systems that can adjust to internal and external changes in other ways besides incision and aggradation by modifying their stream patterns and channel geometries. Application of geomorphic principles to sequence stratigraphic models results in the following observations. During eustatic lowstands, rivers may adjust to lowered base levels and changes in slope by modifying channel patterns. Therefore, not all lowstands produce type 1 sequence boundaries. Type 1 sequence boundaries characterized by fluvial-valley incision are more likely to develop when sea level drops below the shelf-slope break, resulting in topological relief near the strandline in which headwardly eroding knickpoints form. Rate of eustatic change is sufficiently low that geomorphic systems can maintain their equilibrium during eustatic changes and migrate back and forth across the shelf without major modifications. Finally, under conditions of relatively static sea level, sequences and parasequences of the same scale in time and space can be deposited as the result of purely intrinsic causes and responses of a fluvial system. In general, eustasy controls the location of deposition and erosion, but the resultant stratal geometry is controlled by sediment supply and processes acting on the sediments as the shoreline moves across the shelf in response to eustasy. Sequence stratigraphy is frequently used in petroleum exploration and basin analysis. However, present models do not adequately in corporate modern principles of fluvial geomorphology and do not accurately predict sedimentary facies and surfaces in some basins. 33 refs., 14 figs., 4 tabs.

  6. Two depositional models for Pliocene coastal plain fluvial systems, Goliad Formation, south Texas Gulf Coastal plain

    SciTech Connect

    Hoel, H.D.; Galloway, W.E.

    1983-03-01

    The Goliad Formation consists of four depositional systems-the Realitos and Mathis bed-load fluvial systems in the southwest and the Cuero and Eagle Lake mixed-load fluvial systems in the northeast. Five facies are recognized in the Realitos and Mathis bed-load fluvial systems: (1) primary channel-fill facies, (2) chaotic flood channel-fill facies, (3) complex splay facies, (4) flood plain facies, and (5) playa facies. A model for Realitos-Mathis depositional environments shows arid-climate braided stream complexes with extremely coarse sediment load, highly variable discharge, and marked channel instability. Broad, shallow, straight to slightly sinuous primary channels were flanked by wide flood channels. Flood channels passed laterally into broad, low-relief flood plains. Small playas occupied topographic lows near large channel axes. Three facies are recognized in the Cuero and Eagle Lake mixed-load fluvial systems: (1) channel-fill facies, (2) crevasse splay facies, and (3) flood plain facies. A model for Cuero-Eagle Lake depositional environments shows coarse-grained meander belts in a semi-arid climate. Slightly to moderately sinuous meandering streams were flanked by low, poorly developed natural levees. Crevasse splays were common, but tended to be broad and ill-defined. Extensive, low-relief flood plains occupied interaxial areas. The model proposed for the Realitos and Mathis fluvial systems may aid in recognition of analogous ancient depositional systems. In addition, since facies characteristics exercise broad controls on Goliad uranium mineralization, the proposed depositional models aid in defining target zones for Goliad uranium exploration.

  7. Characteristics of steady state fluvial topography above fault-bend folds

    NASA Astrophysics Data System (ADS)

    Miller, Scott R.; Slingerland, Rudy L.; Kirby, Eric

    2007-12-01

    In steady state convergent orogens, erosion balances lateral as well as vertical bedrock motions. For simple geometrical reasons, the difference between the total steady state erosion flux and its vertical component is up to 30% for typical fluvial slopes and bedrock streamline inclinations, suggesting that lateral advection is also likely to be expressed topographically. In order to understand these geomorphologic consequences, we focus on steady state topography developed on active fault-bend folds. First, we derive an analytical solution for the slopes of detachment-limited streams that incorporates lateral advection. Next, we conduct experiments using a numerical two-dimensional landscape evolution model (Channel-Hillslope Integrated Landscape Development model (CHILD)) incorporating linear diffusion on hillslopes and detachment-limited stream channel incision above a fault-bend fold. The concavity and steepness indices of steady state long profiles are functions of bedrock velocity magnitude and direction, streamflow direction, and fluvial erosivity. Asymmetry of mountain range profiles varies as a function of fluvial erosivity or bedrock velocity only if we account for the lateral velocity component. This asymmetry is equally sensitive to this lateral component, fluvial incision, and hillslope diffusion. However, the effect of diffusion on drainage divide position is significant only at high diffusivities, short length scales, low bedrock advection rates, or relatively low fluvial erosivity. Thus in most mountain ranges and fault blocks, drainage divide migration is expected to be dictated by stream channel erosion. Model results are shown to be consistent with topography in the Siwalik Hills, Nepal, which overlie fault-bend folds produced above the frontal fault systems in the Himalayan foreland.

  8. Climate-sensitive feedbacks between hillslope processes and fluvial erosion in sediment-driven incision models

    NASA Astrophysics Data System (ADS)

    Skov, Daniel; Egholm, David

    2015-04-01

    Surface erosion and sediment production accelerated dramatically in most parts of the world as the climate cooled in the Late Cenozoic, (e.g. Molnar, Annu. Rev. Earth Planet. Sci. 32, 2004). In many high mountain ranges, glaciers emerged for the first time during the Quaternary, and they represent a likely explanation for the accelerated erosion in such places. Still, observations and measurements point to increases in erosion rate also in landscapes where erosion is driven mainly by fluvial processes (e.g. Lease and Ehlers, Science 341, 2013). Why fluvial incision responds to climate change remains enigmatic, in particular because the obvious links to variations in precipitation, and hence water flux, are not generally supported by erosion rate measures (Stock et al., GSA Bulletin 117, 2005). This study explores potential links between accelerating rates of river incision and sediment production on hillslopes that surround the channel network. Hillslope soil production and soil transport are processes that are likely to respond to decreasing temperatures, because the density of vegetation and for example the occurrence of frost influence rates of weathering and sediment flow. We perform computational landscape evolution experiments where a sediment-flux-dependent model for fluvial incision (e.g. Sklar and Dietrich, Geology 29, 2001) is coupled to models for sediment production and transport on hillslopes. The resulting coupled landscape dynamics is of a highly nonlinear nature, where even small changes in hillslope sediment production far up in a drainage network propagate all the way through the downstream fluvial system. Dependent on the total sediment load, the fluvial system may respond with increased incision that steepens the hillslopes and starts a positive feedback loop that accelerates overall erosion.

  9. Unincised fluvial and tide-dominated estuarine systems from the Mesoproterozoic Lower Tombador Formation, Chapada Diamantina basin, Brazil

    NASA Astrophysics Data System (ADS)

    Magalhães, A. J. C.; Scherer, C. M. S.; Raja Gabaglia, G. P.; Bállico, M. B.; Catuneanu, O.

    2014-12-01

    The Mesoproterozoic Lower Tombador Formation is formed of shallow braided fluvial, unconfined to poorly-channelized ephemeral sheetfloods, sand-rich floodplain, tide-dominated estuarine, and shallow marine sediments. Lowstand braided fluvial deposits are characterized by a high degree of channel amalgamation interbedded with ephemeral, intermediate sheetflood sandstones. Sand-rich floodplain sediments consist of intervals formed by distal sheetflood deposits interbedded with thin layers of eolian sandstones. Tide-dominated estuarine successions are formed of tide-influenced sand-bed braided fluvial, tidal channel, tidal sand flat and tidal bars. Shallow marine intervals are composed of heterolithic strata and tidal sand bars. Seismic scale cliffs photomosaics calibrated with vertical sections indicate high lateral continuity of sheet-like depositional geometry for fluvial-estuarine successions. These geometric characteristics associated with no evidence of incised-valley features nor significant fluvial scouring suggest that the Lower Tombador Formation registers deposition of unincised fluvial and tide-dominated systems. Such a scenario is a natural response of the interplay between sedimentation and fluctuations of relative sea level on the gentle margins of a sag basin. This case study indicates that fluvial-estuarine successions exhibit the same facies distributions, irrespective of being related to unincised or incised-valley systems. Moreover, this case study can serve as a starting point to better understand the patterns of sedimentation for Precambrian basins formed in similar tectonic settings.

  10. Combined fluvial and pluvial urban flood hazard analysis: method development and application to Can Tho City, Mekong Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Apel, H.; Trepat, O. M.; Hung, N. N.; Chinh, D. T.; Merz, B.; Dung, N. V.

    2015-08-01

    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 fluvial or pluvial flood hazard, studies of combined fluvial and pluvial flood hazard are hardly available. Thus this study aims at the analysis of fluvial and pluvial flood hazard individually, but also at developing a method for the analysis of 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 example. In this tropical environment the annual monsoon triggered floods of the Mekong River can coincide with heavy local convective precipitation events causing both fluvial and pluvial flooding at the same time. 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. Pluvial hazard was estimated by a peak-over-threshold frequency estimation based on local rain gauge data, and a stochastic rain storm generator. Inundation was simulated by a 2-dimensional hydrodynamic model implemented on a Graphical Processor Unit (GPU) for time-efficient flood propagation modelling. All hazards - fluvial, pluvial and combined - were accompanied by an uncertainty estimation considering 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 ways for their usage in flood risk management are outlined.

  11. Temporal and spatial variability of tidal-fluvial dynamics in the St. Lawrence fluvial estuary: An application of nonstationary tidal harmonic analysis

    NASA Astrophysics Data System (ADS)

    Matte, Pascal; Secretan, Yves; Morin, Jean

    2014-09-01

    Predicting tides in upstream reaches of rivers is a challenge, because tides are highly nonlinear and nonstationary, and accurate short-time predictions of river flow are hard to obtain. In the St. Lawrence fluvial estuary, tide forecasts are produced using a one-dimensional model (ONE-D), forced downstream with harmonic constituents, and upstream with daily discharges using 30 day flow forecasts from Lake Ontario and the Ottawa River. Although this operational forecast system serves its purpose of predicting water levels, information about nonstationary tidal-fluvial processes that can be gained from it is limited, particularly the temporal changes in mean water level and tidal properties (i.e., constituent amplitudes and phases), which are function of river flow and ocean tidal range. In this paper, a harmonic model adapted to nonstationary tides, NS_TIDE, was applied to the St. Lawrence fluvial estuary, where the time-varying external forcing is directly built into the tidal basis functions. Model coefficients from 13 analysis stations were spatially interpolated to allow tide predictions at arbitrary locations as well as to provide insights into the spatiotemporal evolution of tides. Model hindcasts showed substantial improvements compared to classical harmonic analyses at upstream stations. The model was further validated by comparison with ONE-D predictions at a total of 32 stations. The slightly lower accuracy obtained with NS_TIDE is compensated by model simplicity, efficiency, and capacity to represent stage and tidal variations in a very compact way and thus represents a new means for understanding tidal rivers.

  12. Using portable impact sensors for analyzing fluvial bedload transport in steep mountain streams

    NASA Astrophysics Data System (ADS)

    Beylich, A.; Laute, K.

    2013-12-01

    The timing and rate of fluvial bedload transport are of central importance in quantitative studies on fluvial transport, within sediment budget studies, and in many applications in river science and engineering. Bedload transport rates are still comparably difficult to measure and, in many sites, only suspended load and solute load data are actually included in fluvial sediment budget studies. Detailed field measurements with portable impact sensors as a comparably new and non-invasive technique for indirectly determining fluvial bedload transport intensity have been conducted since 2010 in two instrumented and supply-limited mountainous drainage basin systems (Erdalen and Bødalen) in western Norway. Additional field measurements with portable impact sensors were carried out in three selected transport-limited fluvial systems in the Coast Mountains of western Canada. The collected impact sensor field data were calibrated with laboratory impact sensor flume experiments. In the transport-limited systems (in western Canada) with generally high bedload transport rates during high discharge and with bedload moving in clusters over the impact sensor plates, impact sensor data (based on a 1 s measuring interval) provide the opportunity to detect the start and end of bedload transport, thus to identify discharge thresholds for sediment entrainment, and to roughly estimate the intensity and relative intensity changes of bedload transport during the measuring period. In the supply-limited systems (in western Norway) with generally low bedload transport rates and bedload components moving separately (as single particles) over the impact sensor plates, impact sensor data (based on a 1 s measuring interval) allow the detection of the start and end of transport of bedload components >11.3 mm, thus the identification of discharge thresholds for possible entrainment of particles, the quantification of the number of particles >11.3 mm moving over the impact sensor plates during the measuring period, the rough estimation of grain sizes of the particles >11.3 mm moving separately over the impact sensor plates, and the calculation of the total mass of the bedload material >11.3 mm moving over the impact sensor plates during the measuring period. When combined with other bedload measuring methods and techniques (Helley-Smith sampling, particle tracer measurements, biofilm analyses, underwater video filming) which have provided information on the active bedload transport channel width, on discharge thresholds for possible entrainment of particles of different grain sizes, and on transport rates of bedload material <11.3 mm, total rates of fluvial bedload transport, covering all given grain sizes of the bedload material, can be calculated for the supply-limited mountain streams with generally low bedload transport. The higher computed mean annual bedload yield in Bødalen (13.6 t km-2yr-1) compared to Erdalen (2.6 t km-2yr-1) reflects a higher level of slope-channel coupling in the Bødalen drainage basin than in Erdalen. In both drainage basins fluvial bedload transport is smaller than fluvial suspended sediment transport. In Bødalen the annual fluvial bedload yield is two times greater than annual chemical denudation whereas in Erdalen it is less than half of the annual chemical denudation rate.

  13. The potential of hydrodynamic analysis for the interpretation of Martian fluvial activities

    NASA Astrophysics Data System (ADS)

    Kim, Jungrack; Schumann, Guy; Neal, Jeffrey; Lin, Shih-Yuan

    2014-05-01

    After liquid water was identified as the agent of ancient Martian fluvial activities, the valley and channels on the Martian surface were investigated by a number of remote sensing and in-situ measurements. In particular, the stereo DTMs and ortho images from various successful orbital sensors are being effectively used to trace the origin and consequences of Martian hydrological channels. For instance, to analyze the Martian fluvial activities more quantitatively using the topographic products, Burr et al. (2003) employed 1D hydrodynamic models such as HEC-RAS together with the topography by MOLA to derive water flow estimates for the Athabasca Valles area on Mars [1]. Where extensive floodplain flows or detailed 2D bathymetry for the river channel exist, it may be more accurate to simulate flows in two dimensions, especially if the direction of flow is unclear a priori. Thus in this study we demonstrated a quantitative modeling method utilizing multi-resolution Martian DTMs, constructed in line with Kim and Muller's (2009) [2] approach, and an advanced hydraulics model LISFLOOD-FP (Bates et al., 2010) [3], which simulates in-channel dynamic wave behavior by solving for 2D shallow water equations without advection. Martian gravitation and manning constants were adjusted in the hydraulic model and the inflow values were iteratively refined from the outputs of the coarser to the finer model. Then we chose the target areas among Martian fluvial geomorphologies and tested the effectiveness of high resolution hydraulic modeling to retrieve the characteristics of fluvial systems. Test sites were established in the Athabasca Valles, Bahram Vallis, and Naktong Vallis respectively. Since those sites are proposed to be originated by different fluvial mechanisms, it is expected that the outputs from hydraulics modeling will provide important clues about the evolution of each fluvial system. Hydraulics modeling in the test areas with terrestrial simulation parameters was also conducted to explore the different characteristics of two planets' fluvial activities. Ultimately, this study proved the effectiveness of multi-resolution modeling using 150-1.2m DTMs and 2D hydraulics to study the Martian fluvial system. In future study, we will elaborate the hydrodynamic model to investigate the sediment transformation mechanism in Martian fluvial activities using hydrodynamic properties such as flow speed. References: [1] Burr, D.M. (2003).Hydraulic modelling of Athabasca Vallis, Mars. Hydrological Sciences Journal, 48(4), 655-664. [2] Kim, J.R. & Muller, J-P.,(2009).Multi resolution topographic data extraction from Martian stereo imagery.Planetary and Space Science. 57, 2095-2112. [3] Bates, P.D., Horritt, M.S., & Fewtrell, T.J. (2010). A simple inertial formulation of the shallow water equations for efficient two-dimensional flood inundation modelling. Journal of Hydrology, 387(1), 33-45.

  14. 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.

  15. Basin-scale and travertine dam-scale controls on fluvial travertine, Jiuzhaigou, southwestern China

    NASA Astrophysics Data System (ADS)

    Florsheim, J. L.; Ustin, S. L.; Tang, Y.; Di, B.; Huang, C.; Qiao, X.; Peng, H.; Zhang, M.; Cai, Y.

    2013-01-01

    Travertine deposition in fluvial systems builds dams and other forms that create diversity in geomorphic processes, morphology, and associated wetland ecosystems. In Jiuzhaigou Natural Reserve, Sichuan Province, China, we investigate the relation between contemporary fluvial travertine morphology, slope, and water chemistry at the fluvial-system scale and at the local scale of large individual dams in order to address two fundamental questions. First, what factors determine the spatial distribution of such large valley-spanning, or primary, travertine dams? Second, what factors govern smaller but distinctive travertine dams and other secondary travertine morphology present on the sloping downstream side of primary travertine dams? Through remote sensing analysis and field work, we recognize two factors as paramount in controlling spatial distribution of primary fluvial travertine dams: watershed-scale steps in the longitudinal profile and water chemistry, based on a proxy for dissolved calcite. In the steep Jiuzhaigou watershed, hillslope erosion processes that contribute large boulders to the channel influence the majority of the primary dams. However, two valley-spanning primary dams, Pearl Shoals and Norilang Lakes, appear to be dominated by travertine precipitation. The submerged upstream sides of these two dams are nearly vertical with heights > 30 m. Slope varies with position along the longitudinal profiles over the downstream sides of these two primary dams because the profile shapes are convex. With downstream-dam profile lengths > 500 m, flow encounters secondary travertine morphology organized as an array of travertine bedforms that vary with local channel slope along the convex profiles. The secondary travertine bedforms include sequences of repeating patterns including smaller dams that impound correspondingly small waterbodies. Morphologic differences between two types of secondary dams are quantified on the basis of their relative size, spacing, and the slope on which they form. Increasing slope is correlated with a decrease in height of secondary travertine bedforms according to a power law where y = 0.0053x- 1.68. Results of the investigation demonstrate that slope, a main influence on river hydrodynamics, influences and is influenced by fluvial travertine morphology at two discrete fluvial scales. This work advances our understanding of geomorphic factors that influence travertine morphology, a critical need for conservation and management of travertine natural resources and their wetland ecosystems.

  16. An analysis of the combined consequences of pluvial and fluvial flooding.

    PubMed

    Chen, A S; Djordjević, S; Leandro, J; Savić, D A

    2010-01-01

    Intense rainfall in urban areas often generates both pluvial flooding due to the limited capacity of drainage systems, as well as fluvial flooding caused by deluges from river channels. The concurrence of pluvial and fluvial flooding can aggravate their (individual) potential damages. To analyse the impact caused by individual and composite type of flooding, the SIPSON/UIM model, an integrated 1D sewer and 2D overland flow was applied to numerical modelling. An event matrix of possible pluvial scenarios was combined with hypothetic overtopping and breaching situations to estimate the surface flooding consequences in the Stockbridge area, Keighley (Bradford, UK). The modelling results identified different flooding drivers in different parts of the study area and showed that the worst scenarios resulted from synthesised events. PMID:20935365

  17. Ichnofossils and rhizoliths of the nearshore fluvial Jebel Qatrani Formation (Oligocene), Fayum Province, Egypt

    USGS Publications Warehouse

    Bown, T.M.

    1982-01-01

    The ichnofossils and rhizoliths of the Oligocene Jebel Qatrani Formation of Egypt are among the best preserved, most diverse in form, and most abundant of such structures yet recognized in fluvial rocks. Twenty-one forms are described. The ichnofauna contains traces (domichnia, fodinichnia, cubichnia) of probable annelid, insect, crustacean, and vertebrate origin. These include the first described fossil nest structures and gallery systems of subterranean termites (Isoptera), the first examples of Ophiomorpha from wholly fluvial rocks, and the first fossil vertebrate burrows from the African Tertiary. Rhizoliths associated with the ichnofauna and those occurring elsewhere document a variety of small, wetland plants, coastal mangroves, and much larger trees. The environment suggested by these traces is consistent with the coastal, tropical to subtropical, monsoonal rain forest, with adjacent more open areas, that is indicated by independent evidence of sedimentology, paleontology, and paleopedology. ?? 1982.

  18. Dissected paleotopography and base-level changes in a Triassic fluvial sequence

    NASA Astrophysics Data System (ADS)

    Kraus, Mary J.; Middleton, Larry T.

    1987-01-01

    At one stratigraphic level in Petrified Forest National Park in Arizona, fluvial mudrocks of the Chinle Formation are truncated by areally extensive deep scours that are filled dominantly by pedogenically modified mudrocks. Color differences between paleosols, developed on scoured and scour-fill deposits, facilitate recognition of the dissected interval. The mudstone-filled scour system records a period of channel incision and widespread gullying caused by lowered base level. Although it is difficult to document subsidence rates in the Chinle basin, the tectonic setting suggests that the enormous scour system could be the result of fluctuations in regional thermal activity during Late Triassic time. Similar scour and fill should occur in other fluvial sequences; however, because they both truncate and are filled by mudrocks, identification can be difficult. Recognition of them is important because they are indicators of base-level fluctuations and thus are useful in unraveling the depositional history of a basin.

  19. Integrating field measurements with flume experiments for analysing fluvial bedload transport in steep mountain streams

    NASA Astrophysics Data System (ADS)

    Beylich, A. A.; Laute, K.; Liermann, S.

    2012-04-01

    Fluvial bedload transport has high importance within sediment budgets of steep catchments and steep mountain streams. It is also of crucial importance as headwater catchments and steep mountain streams can be relevant sediment sources for lowland river systems. Measured under comparable conditions of discharge, rates of fluvial bedload transport can differ by up to one order of magnitude, which is due to the irregular nature of sediment movement. Bedload transport at a defined site depends on factors such as local flow conditions, bed material composition and amount of sediment supply from upstream sources. Irregular deviations from mean rates of bedload transport can be caused by sporadic inputs of material from hillslopes. Permafrost degradation and shifts in ground frost regimes as caused by climate change can lead to increased frequencies and intensities of mass movements on slopes including the increased frequency of rock fall events. By the destabilisation of slope systems higher amounts of sediment are available from a larger number of activated sediment sources. At the same time, a higher frequency of extreme rainfall events and thermally determined runoff-peaks from glacier-fed systems is leading to an increased number of peak runoff events showing a high transport competence with significant fluvial bedload transport. A better general understanding of the exact mechanisms and the dynamics of fluvial bedload transport is essential for the further improvement of river engineering management and hazard mitigation projects. Since 2004, extended and interdisciplinary field investigations on fluvial bedload transport using a novel combination of methods and techniques have been performed in a number of selected stream segments in supply-limited fluvial systems in the inner Nordfjord (Erdalen and Bødalen drainage basins) in western Norway. Field studies include (i) continuous channel discharge monitoring, (ii) frequently repeated surveys of channel morphometry and granulometric analyses, (iii) different tracer techniques (painted stones, magnetic tracers), (iv) Helley-Smith and other basket measurements, (v) horizontally installed impact sensors, (vi) underwater video filming, and (vii) extended biofilm analyses, including also controlled biofilm growing experiments with fixed baskets in selected channels. In addition, field studies with horizontally installed impact sensors were also carried out in selected transport-limited fluvial systems in the Coast Mountains of British Columbia (Canada) in 2010 and 2011. The extended field studies are integrated with advanced flume experiments which were carried out in 2010 and 2011 at the Department of Geography at the University of British Columbia (UBC), Canada for calibration of field measurements. As a key achievement, the entire range of different bedload component grain sizes can be covered by the applied combination of techniques, and the presented integration of interdisciplinary field measurements with flume experiments appears to be a useful approach to study mechanisms, controlling factors and rates of fluvial bedload transport in steep mountain streams.

  20. Regional variations in the fluvial Upper Devonian and Lower Mississippian(?) Kanayut Conglomerate, Brooks Range, Alaska

    USGS Publications Warehouse

    Moore, T.E.; Nilsen, T.H.

    1984-01-01

    The wholly allochthonous Upper Devonian and Lower Mississippian(?) Kanayut Conglomerate is one of the most extensive fluvial deposits in North America. It crops out for 950 km along the crest of the Brooks Range in a series of thrust plates and is as thick as 2615 m. The Kanayut forms the fluvial part of a large, coarse-grained delta. The lower part of the Kanayut (the Ear Peak Member) overlies marginal-marine and prodelta turbidite deposits and consists of fining-upward meandering-stream-channel cycles of conglomerate and sandstone within black to maroon floodplain shale deposits. The middle part of the Kanayut (the Shainin Lake Member) lacks shale and consists of fining-upward couplets of channelized conglomerate and parallel- to cross-stratified sandstone interpreted as braidplain deposits. These deposits contain the largest clasts (23 cm) and were deposited during maximum progradation of the fluvial sequence. The upper part of the Kanayut (the Stuver Member), which consists of fining-upward meandering stream cycles similar to those of the lower part, grades upward into overlying Lower Mississippian tidal and marginal-marine deposits. Paleocurrent data and distribution of largest clasts indicate that the Kanayut was deposited by southwest-flowing streams fed by at least two major trunk streams that drained a mountainous region to the north and east. Comparison of stratigraphic and sedimentologic data collected at three selected locations representative of proximal, intermediate and distal parts of the Kanayut basin reveal regional variations in its fluvial character. These include a decrease in total thickness of fluvial strata, an increase in total thickness of associated marine sandstone, the pinch-out of the coarse-grained middle part of the Kanayut and decreases in the conglomerate/sandstone and sandstone/shale ratios from proximal to distal areas of the basin. The coarse-grained parts of the fluvial cycles decrease in thickness and lateral extent from proximal to distal areas of the basin. In more distal areas of sedimentation, the middle parts of some fluvial cycles consist of calcareous and bioturbated marine sandstone. Although thinner than in more proximal areas, the associated fine-grained upper parts of some cycles also contain marine features and suggest that these strata represent the deposits of interdistributary bays. These features are interpreted to indicate that the proximal deposits of the Kanayut Conglomerate were deposited by large, stable fine-grained meandering rivers (the Ear Peak and Stuver Members) and gravelly braided rivers (Shainin Lake Member) on the upper delta plain of the Kanayut delta. Sedimentation in more distal locations, interpreted to represent lower delta plain deposits, was by smaller distributary rivers with characteristics of both braided and meandering streams. Near their interface with marginal marine deposits the fluvial deposits were locally strongly influenced by tidal or estuarine conditions. ?? 1984.

  1. Fluvial development of major Alpine valleys since the mid-Pleistocene transition

    NASA Astrophysics Data System (ADS)

    Leith, Kerry; Fox, Matthew; Moore, Jeffrey R.

    2015-04-01

    The effects of both fluvial and glacial processes are evident in the morphology of bedrock hillslopes and river channels throughout the European Alps. While steep rock slopes in upper, U-shaped reaches of valleys provide clear evidence for a Pleistocene history that includes at least one period of major glacial erosion, river channels near the toe of blocky rock slopes in lower, V-shaped reaches suggest fluvial incision has played an important role in Alpine evolution. In order to differentiate the impact of these two process regimes on the development of the orogen, we use a combination of integral analysis and forward streampower models to identify a series of corresponding steepened channel reaches across a relatively homogeneous tectonic block of the southern Swiss Alps. We consider these steepened channel sections represent up to seven knickpoints that extend 800 m above the elevation of the present-day Rhone Valley. The uppermost (oldest) knickpoint is currently located approximately half-way into each valley, and effectively defines the front of fluvial erosion into a relict glacial landscape preserved in the upper reaches of each catchment. We expect that these knickpoints form near the outlet of tributary valleys as a result of bedrock uplift during major glacial cycles. The knickpoints are exposed during deglaciation, and propagate upstream as in response to increased streampower during major Pleistocene interglacials. By employing a forward streampower incision model regulated by the timing of global marine isotope stages we are able to reproduce both the form, and location of knickpoints across our study region, and correlate distinct breaks in cross-sectional valley slope to discrete glacial - interglacial transitions. Our results indicate that Alpine landscape evolution has been driven by a combination of tectonic uplift and fluvial incision since an initial period of enhanced glacial erosion prior to 0.7 Ma. We find that rates of tectonic uplift have been relatively consistent since this time, while transitional landscape forms have been largely preserved throughout each glacial cycle.

  2. Transient rock slope processes driven by Pleistocene fluvial incision in Alpine valleys

    NASA Astrophysics Data System (ADS)

    Leith, Kerry; Fox, Matthew; Moore, Jeffrey; Loew, Simon

    2013-04-01

    Major tributary valleys within Canton Valais (Switzerland) 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 flow out over the alluvial plane of the Rhone Valley, converging to discharge into Lake Geneva, which defines a long-term local baselevel for the system. Using a 2.5 m resolution LiDAR DEM, we correlate knickpoints common to several of the tributary valleys, which are assumed to be associated with the propagation of ongoing fluvial incision into the steep bedrock/talus sections the river channels. The morphology of valley walls several hundred metres above these steep channel sections is characteristically rough, and large deep-seated landslides which commonly intersect the upstream alluvial planes are not present within this rough region. Assuming knickpoints develop as a result of glacial erosion concentrated below the valley confluences, we use a 1-D stream power erosion model, modulated by mid- to late-Pleistocene glacial/interglacial cycles, to evaluate contemporaneous fluvial incision and knickpoint propagation. We assume baselevel is determined by the elevation of Lake Geneva, and differential uplift between the foreland and inner Alpine valleys is ongoing. We can therefore isolate bedrock erodibility as the sole independent variable for the valleys. The best-fit model results indicate fluvial bedrock incision has taken place during multiple interglacial cycles, possibly since marine isotope stage (MIS) 12 (~425 ka BP). Modelled erosion rates are typically between 2 and 10 mm/yr, and we calculate up to 700 m of total bedrock incision. We suggest rock slope morphologies associated with this long-term transition to a fluvial landscape have persisted through multiple glacial cycles.

  3. Identification of remaining oil resource potential in the Frio Fluvial/Deltaic Sandstone play, South Texas

    SciTech Connect

    Holtz, M.H.; McRae, L.E.; Tyler, N.

    1994-05-01

    The Frio Fluvial/Deltaic Sandstone (Vicksburg Fault Zone) oil play of South Texas has produced nearly 1 billion stock tank barrels (BSTB) of oil, yet still contains about 1.2 BSTB of unrecovered mobile oil and an even greater amount of residual oil resources (1.5 BSTB). More than half of the reservoirs in this depositionally complex play have been abandoned, and large volumes of oil may remain unproduced. Interwell-scale geological facies models of Frio fluvial/deltaic reservoirs will be combined with engineering assessments and geophysical evaluations in order to characterize Frio fluvial/deltaic reservoir architecture, flow unit boundaries, and the controls that these characteristics exert on the location and volume of unrecovered mobile and residual oil. Reservoir attribute data were statistically analyzed from oil and gas fields throughout the geographic area covered by the Frio Fluvial/Deltaic Sandstone oil play. General reservoir attributes analyzed in detail included porosity, initial water saturation, residual oil saturation, net pay, reservoir area, and fluid characteristics. Statistical analysis of variance demonstrated no difference between oil reservoir attributes and gas reservoir attributes. Probability functions that describe attribute frequency distributions were determined for use in risk adjusting resource calculations. The oil play was found to contain significant volumes of remaining oil. The volumetric probability distribution between 5- and 95-percent probability for original oil in place ranges from 3.8 to 5.6 BSTB, original mobile oil in place ranges from 2.5 to 3.6 BSTB, and residual oil ranges from 1.5 to 2.3 BSTB. The untapped oil resource may be 10 percent of the original oil in place, or 380 million stock tank barrels.

  4. Modeling Fluvial Incision and Transient Landscape Evolution: Influence of Dynamic Channel Adjustment

    NASA Astrophysics Data System (ADS)

    Attal, M.; Tucker, G. E.; Cowie, P. A.; Whittaker, A. C.; Roberts, G. P.

    2007-12-01

    Channel geometry exerts a fundamental control on fluvial processes. Recent work has shown that bedrock channel width (W) depends on a number of parameters, including channel slope, and is not only a function of drainage area (A) as is commonly assumed. The present work represents the first attempt to investigate the consequences, for landscape evolution, of using a static expression of channel width (W ~ A0.5) versus a relationship that allows channels to dynamically adjust to changes in slope. We consider different models for the evolution of the channel geometry, including constant width-to-depth ratio (after Finnegan et al., Geology, v. 33, no. 3, 2005), and width-to-depth ratio varying as a function of slope (after Whittaker et al., Geology, v. 35, no. 2, 2007). We use the Channel-Hillslope Integrated Landscape Development (CHILD) model to analyze the response of a catchment to a given tectonic disturbance. The topography of a catchment in the footwall of an active normal fault in the Apennines (Italy) is used as a template for the study. We show that, for this catchment, the transient response can be fairly well reproduced using a simple detachment-limited fluvial incision law. We also show that, depending on the relationship used to express channel width, initial steady-state topographies differ, as do transient channel width, slope, and the response time of the fluvial system. These differences lead to contrasting landscape morphologies when integrated at the scale of a whole catchment. Our results emphasize the importance of channel width in controlling fluvial processes and landscape evolution. They stress the need for using a dynamic hydraulic scaling law when modeling landscape evolution, particularly when the uplift field is non-uniform.

  5. Post Waterflood CO2 Miscible Flood in Light Oil, Fluvial-Dominated Deltaic Reservoir, Class I

    SciTech Connect

    Bou-Mikael, Sami

    2002-02-05

    This report demonstrates the effectiveness of the CO2 miscible process in Fluvial Dominated Deltaic reservoirs. It also evaluated the use of horizontal CO2 injection wells to improve the overall sweep efficiency. A database of FDD reservoirs for the gulf coast region was developed by LSU, using a screening model developed by Texaco Research Center in Houston. The results of the information gained in this project is disseminated throughout the oil industry via a series of SPE papers and industry open forums.

  6. Fluvial processes and vegetation - Glimpses of the past, the present, and perhaps the future

    USGS Publications Warehouse

    Osterkamp, W.R.; Hupp, C.R.

    2010-01-01

    Most research before 1960 into interactions among fluvial processes, resulting landforms, and vegetation was descriptive. Since then, however, research has become more detailed and quantitative permitting numerical modeling and applications including agricultural-erosion abatement and rehabilitation of altered bottomlands. Although progress was largely observational, the empiricism increasingly yielded to objective recognition of how vegetation interacts with and influences geomorphic process. A review of advances relating fluvial processes and vegetation during the last 50 years centers on hydrologic reconstructions from tree rings, plant indicators of flow- and flood-frequency parameters, hydrologic controls on plant species, regulation of sediment movement by vegetation, vegetative controls on mass movement, and relations between plant cover and sediment movement. Extension of present studies of vegetation as a regulator of bottomland hydrologic and geomorphic processes may become markedly more sophisticated and widespread than at present. Research emphases that are likely to continue include vegetative considerations for erosion modeling, response of riparian-zone forests to disturbance such as dams and water diversion, the effect of vegetation on channel and bottomland dynamics, and rehabilitation of stream corridors. Research topics that presently are receiving attention are the effect of woody vegetation on the roughness of stream corridors and, hence, processes of flood conveyance and flood-plain sedimentation, the development of a theoretical basis for rehabilitation projects as opposed to fully empirical approaches, the effect of invasive plant species on the dynamics of bottomland vegetation, the quantification of below-surface biomass and related soil-stability factors for use in erosion-prediction models, and the effect of impoundments on downstream narrowing of channels and accompanying encroachment of vegetation. Bottomland vegetation partially controls and is controlled by fluvial-geomorphic processes. The purposes of this paper are to identify and review investigations that have related vegetation to bottomland features and processes, to distinguish the present status of these investigations, and to anticipate future research into how hydrologic and fluvial-geomorphic processes of bottomlands interact with vegetation.

  7. Beaver ponds' impact on fluvial processes (Beskid Niski Mts., SE Poland).

    PubMed

    Giriat, Dorota; Gorczyca, Elżbieta; Sobucki, Mateusz

    2016-02-15

    Beaver (Castor sp.) can change the riverine environment through dam-building and other activities. The European beaver (Castor fiber) was extirpated in Poland by the nineteenth century, but populations are again present as a result of reintroductions that began in 1974. The goal of this paper is to assess the impact of beaver activity on montane fluvial system development by identifying and analysing changes in channel and valley morphology following expansion of beaver into a 7.5km-long headwater reach of the upper Wisłoka River in southeast Poland. We document the distribution of beaver in the reach, the change in river profile, sedimentation type and storage in beaver ponds, and assess how beaver dams and ponds have altered channel and valley bottom morphology. The upper Wisłoka River fluvial system underwent a series of anthropogenic disturbances during the last few centuries. The rapid spread of C. fiber in the upper Wisłoka River valley was promoted by the valley's morphology, including a low-gradient channel and silty-sand deposits in the valley bottom. At the time of our survey (2011), beaver ponds occupied 17% of the length of the study reach channel. Two types of beaver dams were noted: in-channel dams and valley-wide dams. The primary effect of dams, investigated in an intensively studied 300-m long subreach (Radocyna Pond), was a change in the longitudinal profile from smooth to stepped, a local reduction of the water surface slope, and an increase in the variability of both the thalweg profile and surface water depths. We estimate the current rate of sedimentation in beaver ponds to be about 14cm per year. A three-stage scheme of fluvial processes in the longitudinal and transverse profile of the river channel is proposed. C. fiber reintroduction may be considered as another important stage of the upper Wisłoka fluvial system development. PMID:26657380

  8. Applicability of Complexity Theory to Martian Fluvial Systems: A Preliminary Analysis

    NASA Technical Reports Server (NTRS)

    Rosenshein, E. B.

    2003-01-01

    In the last 15 years, terrestrial geomorphology has been revolutionized by the theories of chaotic systems, fractals, self-organization, and selforganized criticality. Except for the application of fractal theory to the analysis of lava flows and rampart craters on Mars, these theories have not yet been applied to problems of Martian landscape evolution. These complexity theories are elucidated below, along with the methods used to relate these theories to the realities of Martian fluvial systems.

  9. Paleohydrological methods and some examples from Swedish fluvial environments I. Cobble and boulder deposits.

    USGS Publications Warehouse

    Williams, G.P.

    1983-01-01

    Establishes approximate empirical relations for determining the minimum unit stream power, bed shear stress and mean flow velocity capable of moving cobbles and boulders on streambeds. The derived equations then are used to estimate the minimum paleoflows that could have transported the boulders of two ancient fluvial deposits in Sweden. The flow estimates are compared with those made by more conventional hydraulic methods. Bankfull flows also are estimated for one of the two deposits, using various hydraulic equations.-Author

  10. The Holocene landscape development of the Gareja region in eastern Georgia - a fluvial approach

    NASA Astrophysics Data System (ADS)

    Sukhishvili, Lasha; Elashvili, Mikheil; Janelidze, Zurab; Kikvadze, Bagrat; Navrozashvili, Levan; von Suchodoletz, Hans

    2013-04-01

    The semi-arid Gareja region in the Iori Highland in the southeastern part of the Republic of Georgia is characterized by an annual precipitation < 500 mm and shows an open steppic landscape today. As is known from historical sources, the landscape showed the same character already during the 6th century AD when the Gareja monastery located in the center of the region was founded by Assyrian monks. However, archaeological research carried out during the Soviet Period showed that there were dozens of settlements of bronze and iron age in this region almost devoid of water resources today, hinting to some sources of fresh water allowing people to live there during those periods. Furthermore, former archaeobotanical studies assume that the region was covered by forests instead of steppes during the past, although there is no final proof yet. The goal of this study is to shed light on the development of the palaeo-landscape during the prehistoric period and thus to address some of the issues described above. To do so, our work is based on the network of episodic streams that cross the region, running from the Iori mountains towards the Mtkvari (Kura) river as the main gaining stream of the region. Using rain water flow direction modeling in GIS we determined the main fluvial courses according to their. This pattern was compared with that of prehistoric settlements known from archaeologic studies, in order to get information about the possible perennial character of some rivers during the past. Furthermore, we did first investigations of outcrops with fluvial sediments found along some of such fluvial courses: Based on stratigraphic observations, pedologic investigations of potential palaeosols as indicators of landscape stability as well as on first numerical datings, we started to unravel the fluvial pattern of that region.

  11. Application of UAS photogrammetry for assessment of flood driven fluvial dynamics of montane stream. Case study - Roklansky creek, Sumava Mts.

    NASA Astrophysics Data System (ADS)

    Langhammer, Jakub; Miřijovský, Jakub; Hartvich, Filip; Kaiglová, Jana

    2014-05-01

    Current progress in hydrology and fluvial geomorphology is largely based on new field survey and analysis techniques, employing advanced technologies for monitoring the dynamics of the runoff process, field surveying and for remote monitoring of changes in riverbeds and of fluvial dynamics. Application of these techniques allows researchers to obtain information on a significantly higher qualitative level than using traditional methods of field survey and measurement, either in terms of spatial accuracy and resolution, frequency of sampling or qualitative characteristics of acquired data. The contribution demonstrates the potential of Unmanned Aerial Systems (UAS) for analysis of fluvial dynamics of montane stream, driven by flood in combination with other survey techniques, namely the ground LiDAR scanning, digital granulometry and automated water level monitoring. The UAS photogrammetry is employed in the study to acquire high precision DTMs, enabling reconstruction of riverbed and quantitative analysis of volumetric changes related to initial flood events. The hexacopter UAS platform has been used to acquire the data for photogrammetric analysis of complex stretch of stream with historically elevated fluvial dynamics. The photogrammetric reconstruction enabled to build accurate DTM of riverbed and floodplain before and after the initial event and to calculate the extent of volumetric changes. The potential of UAS photogrammetry for fluvio morphological study is in combination with other monitoring and survey techniques, enabling complex analysis of fluvial dynamics. The magnitude, duration and hydrological properties of initial flood event were derived from automated high frequency water level monitoring. The digital granulometry enabled to analyze the structure of sedimentary material in floodplain. The terrestrial LiDAR scanning allows construction of very detailed 3D models of selected fluvial forms, enabling deeper insight into the effects of fluvial dynamics and to verify the spatial information acquired using UAS photogrammetry. The results of above mentioned techniques are applied to build hydrodynamic model explaining threshold conditions for initiation of changes in fluvial morphology of the riverbed in relation to known and theoretical flood magnitude. The presented study proved the UAS photogrammetry to be unique source of spatial information, allowing analysis of dynamics of fluvial systems with unprecedented precision and flexibility. This technique has full potential to bring spatial information to a new qualitative level and in experimental areas with limited availability of spatial information. The preliminary results achieved in the study enabled us to discuss the synergic potential of coupling the UAS photogrammetry, sensor networks and other hydroinformatic techniques to enhance significantly our knowledge on the dynamics of fluvial systems. Key words: UAS photogrmmetry, DTM, fluvial processes, erosion, hydrodynamic modelling

  12. Fluvial deposits of Yellowstone tephras: Implications for late Cenozoic history of the Bighorn basin area, Wyoming and Montana

    USGS Publications Warehouse

    Reheis, M.C.

    1992-01-01

    Several deposits of tephra derived from eruptions in Yellowstone National Park occur in the northern Bighorn basin area of Wyoming and Montana. These tephra deposits are mixed and interbedded with fluvial gravel and sand deposited by several different rivers. The fluvial tephra deposits are used to calculate stream incision rates, to provide insight into drainage histories and Quaternary tectonics, to infer the timing of alluvial erosion-deposition cycles, and to calibrate rates of soil development. ?? 1992.

  13. Assesing Hydrophysical/Enivornmenal impacts by Dams in the Amazon (fluvial) Basin

    NASA Astrophysics Data System (ADS)

    Wight, C.; Latrubesse, E. M.

    2014-12-01

    Growing demands from human activities are increasing the pressure and impacts on the Amazon River basin. Covering almost 40% of South America, the Amazon River basin's health is of global importance. With tributaries in 6 different countries, the anthropogenic impacts on this large system are complex and hard to synthesize. However to better understand large system responses to human impacts such an analysis is called for. Our objective is to organize a rigorous analysis of the potential hydro-physical impacts of dams on the major sub-basins of the Amazon. We are incorporating existing data of sediment fluxes, deforestation and land-use land-change to include the entire extent of the basin as defined by the fluvial unit. In addition, we will be analyzing the spatial distributions of dams (planned, under construction, and constructed) within each sub-basin. Our preliminary results have used statistical analysis and remote sensing to calculate the extent of deforestation on fluvial regimes of the legal Amazon and concentrated to identify the potential disruptions of sediment fluxes. Combining the spatial distributions of dam sites, and deforestation per sub-basin we will develop a system to interpret land-use and land-change per catchment. This in turn will allow us to better predict changes in the fluvial regimes and allow for comparisons of vulnerability.

  14. Applying fluvial geomorphology to river channel management: Background for progress towards a palaeohydrology protocol

    NASA Astrophysics Data System (ADS)

    Gregory, K. J.; Benito, G.; Downs, P. W.

    2008-06-01

    Significant developments have been achieved in applicable and applied fluvial geomorphology as shown in publications of the last three decades, analyzed as the basis for using results of studies of environmental change as a basis for management. The range of types of publications and of activities are more pertinent to river channel management as a result of concern with sustainability, global climate change, environmental ethics, ecosystem health concepts and public participation. Possible applications, with particular reference to river channel changes, include those concerned with form and process, assessment of channel change, urbanization, channelization, extractive industries, impact of engineering works, historical changes in land use, and restoration with specific examples illustrated in Table 1. In order to achieve general significance for fluvial geomorphology, more theory and extension by modelling methods is needed, and examples related to morphology and process characteristics, integrated approaches, and changes of the fluvial system are collected in Table 2. The ways in which potential applications are communicated to decision-makers range from applicable outputs including publications ranging from review papers, book chapters, and books, to applied outputs which include interdisciplinary problem solving, educational outreach, and direct involvement, with examples summarized in Table 3. On the basis of results gained from investigations covering periods longer than continuous records, a protocol embracing palaeohydrological inputs for application to river channel management is illustrated and developed as a synopsis version (Table 4), demonstrating how conclusions from geomorphological research can be expressed in a format which can be considered by managers.

  15. A comprehensive fluvial geomorphology study of riverbank erosion on the Red River in Winnipeg, Manitoba, Canada

    NASA Astrophysics Data System (ADS)

    Kimiaghalam, Navid; Goharrokhi, Masoud; Clark, Shawn P.; Ahmari, Habib

    2015-10-01

    Riverbank erosion on the Red River in Winnipeg, Manitoba has raised concerns over the last 20 years and more. Although several recent studies have shown that fluvial erosion can reduce riverbank stability and promote geotechnical slope failure, there are too few that have focused on this phenomenon. The present study includes field measurements, experimental testing, and numerical modelling to quantify fluvial erosion through a 10 km reach of the Red River. Results have shown that seasonal freeze-thaw processes can dramatically reduce the critical shear stress and increase erodibility of the riverbanks. Moreover, a simple method has been employed using hydrodynamic numerical models to define the applied shear stresses on the river banks based on the river water level, which will be useful for further research and design purposes. The TEMP/W numerical model was used to define seasonal frost depth to estimate freeze-thaw effects. Finally all field measurements, experimental and numerical models results were used to predict annual fluvial erosion through this reach of the river.

  16. Isotope-based Fluvial Organic Carbon (ISOFLOC) Model: Model formulation, sensitivity, and evaluation

    NASA Astrophysics Data System (ADS)

    Ford, William I.; Fox, James F.

    2015-06-01

    Watershed-scale carbon budgets remain poorly understood, in part due to inadequate simulation tools to assess in-stream carbon fate and transport. A new numerical model termed ISOtope-based FLuvial Organic Carbon (ISOFLOC) is formulated to simulate the fluvial organic carbon budget in watersheds where hydrologic, sediment transport, and biogeochemical processes are coupled to control benthic and transported carbon composition and flux. One ISOFLOC innovation is the formulation of new stable carbon isotope model subroutines that include isotope fractionation processes in order to estimate carbon isotope source, fate, and transport. A second innovation is the coupling of transfers between carbon pools, including algal particulate organic carbon, fine particulate and dissolved organic carbon, and particulate and dissolved inorganic carbon, to simulate the carbon cycle in a comprehensive manner beyond that of existing watershed water quality models. ISOFLOC was tested and verified in a low-gradient, agriculturally impacted stream. Results of a global sensitivity analysis suggested the isotope response variable had unique sensitivity to the coupled interaction between fluvial shear resistance of algal biomass and the concentration of dissolved inorganic carbon. Model calibration and validation suggested good agreement at event, seasonal, and annual timescales. Multiobjective uncertainty analysis suggested inclusion of the carbon stable isotope routine reduced uncertainty by 80% for algal particulate organic carbon flux estimates.

  17. Pliocene-Quaternary fluvial and aeolian records in the Souss Basin, southwest Morocco: A geomorphological model

    NASA Astrophysics Data System (ADS)

    Aït Hssaine, Ali; Bridgland, David

    2009-09-01

    The Souss Basin in SW Morocco is filled by Pliocene-Quaternary fluvial, fluvio-lacustrine and aeolian sediments, representing an excellent archive of palaeohydrology, palaeoclimate and the effects of crustal deformation. In general these sediments indicate stream-dominated alluvial systems, influenced by fluctuations in climate (humidity/aridity). Lakes developed within the basin around the Pliocene-Pleistocene transition and persisted into the Early Pleistocene. During this early period, relatively humid conditions are indicated by the dominance of coarse-grained sedimentation in the upper reaches of fluvial systems, the existence of large lakes and the considerable sediment thicknesses in the centre of the basin. Uplift of the surrounding mountain ranges contributed to piedmont formation by providing large amounts of coarse-grained material that accumulated at the lowland margin. Climatic deterioration in the Middle Pleistocene was accompanied by progressively more irregular and disrupted fluvial regimes. These trends were evident in the Late Pleistocene and became clearer after the mid-Holocene, with aeolian activity becoming the dominant sedimentary agent. Differences between upstream and downstream depositional regimes became marked: while coarse-grained sedimentation has characterized the upper reaches of wadi catchments, fine-grained sedimentation has prevailed downstream. Hiatuses in sedimentation throughout the Pliocene and Quaternary are marked by palaeosol horizons interbedded within the sedimentary sequences, indicating alternate vegetated (stable) and unvegetated (unstable/active) phases (biostasy and 'rhexistasy').

  18. Validation of a stochastic digital packing algorithm for porosity prediction in fluvial gravel deposits

    NASA Astrophysics Data System (ADS)

    Liang, Rui; Schruff, Tobias; Jia, Xiaodong; Schüttrumpf, Holger; Frings, Roy M.

    2015-11-01

    Porosity as one of the key properties of sediment mixtures is poorly understood. Most of the existing porosity predictors based upon grain size characteristics have been unable to produce satisfying results for fluvial sediment porosity, due to the lack of consideration of other porosity-controlling factors like grain shape and depositional condition. Considering this, a stochastic digital packing algorithm was applied in this work, which provides an innovative way to pack particles of arbitrary shapes and sizes based on digitization of both particles and packing space. The purpose was to test the applicability of this packing algorithm in predicting fluvial sediment porosity by comparing its predictions with outcomes obtained from laboratory measurements. Laboratory samples examined were two natural fluvial sediments from the Rhine River and Kall River (Germany), and commercial glass beads (spheres). All samples were artificially combined into seven grain size distributions: four unimodal distributions and three bimodal distributions. Our study demonstrates that apart from grain size, grain shape also has a clear impact on porosity. The stochastic digital packing algorithm successfully reproduced the measured variations in porosity for the three different particle sources. However, the packing algorithm systematically overpredicted the porosity measured in random dense packing conditions, mainly because the random motion of particles during settling introduced unwanted kinematic sorting and shape effects. The results suggest that the packing algorithm produces loose packing structures, and is useful for trend analysis of packing porosity.

  19. Modeling fluvial incision and transient landscape evolution: Influence of dynamic channel adjustment

    NASA Astrophysics Data System (ADS)

    Attal, M.; Tucker, G. E.; Whittaker, A. C.; Cowie, P. A.; Roberts, G. P.

    2008-09-01

    Channel geometry exerts a fundamental control on fluvial processes. Recent work has shown that bedrock channel width depends on a number of parameters, including channel slope, and is not solely a function of drainage area as is commonly assumed. The present work represents the first attempt to investigate the consequences of dynamic, gradient-sensitive channel adjustment for drainage-basin evolution. We use the Channel-Hillslope Integrated Landscape Development (CHILD) model to analyze the response of a catchment to a given tectonic perturbation, using, as a template, the topography of a well-documented catchment in the footwall of an active normal fault in the Apennines (Italy) that is known to be undergoing a transient response to tectonic forcing. We show that the observed transient response can be reproduced to first order with a simple detachment-limited fluvial incision law. Transient landscape is characterized by gentler gradients and a shorter response time when dynamic channel adjustment is allowed. The differences in predicted channel geometry between the static case (width dependent solely on upstream area) and dynamic case (width dependent on both drainage area and channel slope) lead to contrasting landscape morphologies when integrated at the scale of a whole catchment, particularly in presence of strong tilting and/or pronounced slip-rate acceleration. Our results emphasize the importance of channel width in controlling fluvial processes and landscape evolution. They stress the need for using a dynamic hydraulic scaling law when modeling landscape evolution, particularly when the relative uplift field is nonuniform.

  20. Re-evaluating luminescence burial doses and bleaching of fluvial deposits using Bayesian computational statistics

    NASA Astrophysics Data System (ADS)

    Cunningham, A. C.; Wallinga, J.; Hobo, N.; Versendaal, A. J.; Makaske, B.; Middelkoop, H.

    2015-01-01

    The optically stimulated luminescence (OSL) signal from fluvial sediment often contains a remnant from the previous deposition cycle, leading to a partially bleached equivalent-dose distribution. Although identification of the burial dose is of primary concern, the degree of bleaching could potentially provide insights into sediment transport processes. However, comparison of bleaching between samples is complicated by sample-to-sample variation in aliquot size and luminescence sensitivity. Here we begin development of an age model to account for these effects. With measurement data from multi-grain aliquots, we use Bayesian computational statistics to estimate the burial dose and bleaching parameters of the single-grain dose distribution. We apply the model to 46 samples taken from fluvial sediment of Rhine branches in the Netherlands, and compare the results with environmental predictor variables (depositional environment, texture, sample depth, depth relative to mean water level, dose rate). Although obvious correlations with predictor variables are absent, there is some suggestion that the best-bleached samples are found close to the modern mean water level, and that the extent of bleaching has changed over the recent past. We hypothesise that sediment deposited near the transition of channel to overbank deposits receives the most sunlight exposure, due to local reworking after deposition. However, nearly all samples are inferred to have at least some well-bleached grains, suggesting that bleaching also occurs during fluvial transport.

  1. Multiwell Experiment final report: 4, The fluvial interval of the Mesaverde Formation

    SciTech Connect

    Not Available

    1990-01-01

    The Department of Energy's Multiwell Experiment (MWX) is a field laboratory in the Piceance Basin of Colorado which has two overall objectives: to characterize the low permeability gas reservoirs in the Mesaverde Formation and to develop technology for their production. Different depositional environments have created distinctly different reservoirs in the Mesaverde, and MWX has addressed each of these in turn. This report presents a comprehensive summary of results from the fluvial interval which lies between 4400 ft and 6000 ft at the MWX site. The reservoirs consist of heterogeneous, amalgamated point-bar sequences which form broad meanderbelts which create irregular, but roughly tabular, reservoirs with widths of 1000--2500 ft. Separate sections of this report are background and summary; site descriptions and operations; geology; log analysis; core analysis; in situ stress; well testing, stimulation, fracture diagnostics, and reservoir evaluation in two separate sandstones; stress, fracture diagnostic, and stimulation experiments in an additional sandstone; supporting laboratory studies; and a bibliography. Additional detailed data, results, analyses, and data file references are presented as appendices which are included on microfiche. The results show that stimulation of fluvial reservoirs can be successful if proper care is taken to minimize damage to the natural fracture system. Both an accelerated leakoff phenomenon and the ability to alter the in situ stress were quantified. Overall, the fluvial interval offers the highest production potential of the three nonmarine intervals studied. 116 refs., 230 figs., 28 tabs.

  2. Multiwell Experiment final report: 4, The fluvial interval of the Mesaverde Formation

    SciTech Connect

    Not Available

    1990-01-01

    The Department of Energy's Multiwell Experiment (MWX) is a field laboratory in the Piceance Basin of Colorado which has two overall objectives: to characterize the low permeability gas reservoirs in the Mesaverde Formation and to develop technology for their production. Different depositional environments have created distinctly different reservoirs in the Mesaverde, and MWX has addressed each of these in turn. This report presents a comprehensive summary of results from the fluvial interval which lies between 4400 ft and 600 ft at the MWX site. The reservoirs consist of heterogeneous, amalgamated point-bar sequences which form broad meanderbelts which create irregular, but roughly tabular, reservoirs with widths of 1000--2500 ft. Separate sections of this report are background and summary; site descriptions and operations; geology; log analysis; core analysis; in situ stress; well testing, stimulation, fracture diagnostics, and reservoir evaluation in two separate sandstones; stress, fracture diagnostic, and stimulation experiments in an additional sandstone; supporting laboratory studies; and a bibliography. Additional detailed data, results, analyses, and data file references are presented as appendices which are included on microfiche. The results show that stimulation of fluvial reservoirs can be successful if proper care is taken to minimize damage to the natural fracture system. Both an accelerated leakoff phenomenon and the ability to alter the in situ stress were quantified. Overall, the fluvial interval offers the highest production potential of the three nonmarine intervals studied. 141 refs., 92 figs., 33 tabs.

  3. Fluvial response to late Quaternary climatic fluctuations, central Kobuk Valley, northwestern Alaska

    SciTech Connect

    Ashley, G.M. . Dept. of Geological Sciences); Hamilton, T.D. )

    1993-09-01

    Much of northwestern Alaska remained unglaciated during the Pleistocene and thus offers a favorable setting for examining long-term records of high-latitude geological and biological change. Epiguruk, a large cut bank 3.5 km long and up to 36 m high on the Kobuk River south of the Brooks Range in eastern Beringia, exposes complex sedimentary successions representing cycles of upper quaternary alluviation and eolian sedimentation, downcutting, and soil formation. A rich record of plants and mammals is also preserved in the section. Deposits of fluvial channels and flood plains, eolian dunes, sand sheets, loess, and ponds, as well as organic soils (Histosols) are represented. Parallel-bedded fine sand and coarse silt couplets that commonly contain root structures, ripple cross-lamination, silt drapes are flood-plain sediments apparently deposited at the interface of fluvial and eolian environments. Multiple fluvial-to-eolian depositional sequences were caused by influx of eolian sediment to the river from intermittently active dune fields south of the Kobuk River. Alluviation in the Kobuk Valley was coeval with glaciation in the Brooks Range, whereas downcutting occurred during interstadials when dune stabilization limited sediment supply. The depositional model developed at Epiguruk may be useful in interpreting some of the widespread subhorizontally stratified late-glacial deposits of Europe and North America.

  4. 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.

  5. Thrust controlled foreland basin fluvial architecture, St. Mary River Formation, southwestern Alberta, Canada

    SciTech Connect

    Nadon, G.C. )

    1991-03-01

    The style of fluvial system in foreland basins varies depending on the distance from the fold-and-thrust belt, and is especially influenced by the location and timing of blind thrusts within the basin. The St. Mary River Formation (Campanian to Maestrichtian) in southwestern Alberta contains lenticular, medium- to fine-grained, single- to two-story, ribbon sandstones deposited in fluvial channels of an anastomosing river system that flowed to the north and northeast from northwestern Montana. Separating the sandstones is a complex assemblage of sandstone/siltstone crevasse splay sheets interbedded with lacustrine and marsh silstones and shales. The anastomosed fluvial system developed between (1) the region of maximum subsidence adjacent to the thrust front in northwestern Montana and (2) the region of uplift associated with contemporaneous blind thrusting in southwestern Alberta. The sandstone lenses are stacked vertically in two patterns: (1) lenses separated laterally by distances of up to 1 km, and (2) numerous lenses present in close lateral proximity to one another. The first stacking pattern represents normal sedimentation on a broad, low-gradient floodplain. The second pattern arises from the local confinement of channels because of topography produced by the growth of blind thrusts. The presence of lenticular or ribbon sandstone bodies in the stratigraphic record of foreland basins elsewhere may be a good indication of syndepositional compartmentation of a basin.

  6. Magnetic Properties of a Fluvial Chronosequence From the Eastern Wind River Range, Wyoming

    NASA Astrophysics Data System (ADS)

    Quinton, E. E.; Dahms, D. E.; Geiss, C. E.

    2010-12-01

    In order to constrain the rate of magnetic enhancement in glacial fluvial sediments, we sampled modern soils from eight fluvial terraces in the East Wind River Range in Wyoming. Soil profiles up to 1.2 meters deep were described in the field and sampled in five cm intervals from a series of hand-dug pits or natural river-bank exposure. The age of the studied profiles are estimated to range from >600 ka to modern. They include Sacagawea Ridge, Bull Lake and Pinedale-age fluvial terraces as well as one Holocene profile. To characterize changes in magnetic properties we measured low-field magnetic susceptibility, anhysteretic remanent magnetization, isothermal remanent magnetization and S-ratios for all, and hysteresis loops for a selected sub-set of samples. Our measurements show no clear trend in magnetic enhancement with estimated soil age. The observed lack of magnetic enhancement in the older soils may be due to long-term deflation, which continuously strips off the magnetically enhanced topsoil. It is also possible that the main pedogenic processes, such as the development of well-expressed calcic horizons destroy or mask the effects of long-term magnetic enhancement.

  7. Fluvial drainage systems: Margaritifer Sinus and Agyre (NC, NE) quadrangles, Mars

    NASA Technical Reports Server (NTRS)

    Boothroyd, J. C.; Grant, J. A.

    1984-01-01

    Fluvial drainage systems, delineated by mapping on stereo pairs of Viking Orbiter images, have developed in various-sized basins in the Margaritifer Sinus (MC-19) and Agyre (MC-26) Quadrangles, Mars. The Ladon Valles system is the largest, draining into and through two multi-ringed impact basins. Smaller fluvial basins to the southeast of the Ladon structural basin appear to have internal drainage. An intermediate-scale fluvial basin containing Himera Vallis extends along a north-south axis at 22 W and opens northward toward outflow channels south of Margaritifer Chaos. Stereo-pair mapping was extended furhter to the east, in MC-19 Ne, Se, and MC-26 NE, to investigate sources of outflow to the Ares Vallis system. The direction of flow in the channel at the northeast quadrant of the Ladon Basin is unresolved at present because of the poor quality of images available to form stereo pairs. However, an easterly drainage basin boundary running north-south along longitude 9 W, and extending westward at latitude 32-35 S, encloses a series of longitudinal drainage systems. Both the Parana Valles-Loire Vallis system and the Samara Valles system appear to drain in a northwesterly direction. The Samara flows to the Himera drainage basin, and the Parana-Loire to the northeast Ladon channel area.

  8. 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.

  9. Liquefaction susceptibility assessment in fluvial plains using airborne lidar: the case of the 2012 Emilia earthquake sequence area (Italy)

    NASA Astrophysics Data System (ADS)

    Civico, R.; Brunori, C. A.; De Martini, P. M.; Pucci, S.; Cinti, F. R.; Pantosti, D.

    2015-11-01

    We report a case study from the Po River plain region (northern Italy), where significant liquefaction-related land and property damage occurred during the 2012 Emilia seismic sequence. We took advantage of a 1 m pixel lidar digital terrain model (DTM) and of the 2012 Emilia coseismic liquefaction data set to (a) perform a detailed geomorphological study of the Po River plain area and (b) quantitatively define the liquefaction susceptibility of the geomorphologic features that experienced different abundance of liquefaction. One main finding is that linear topographic highs of fluvial origin - together with crevasse splays, abandoned riverbeds and very young land reclamation areas - acted as a preferential location for the occurrence of liquefaction phenomena. Moreover, we quantitatively defined a hierarchy in terms of liquefaction susceptibility for an ideal fluvial environment. We observed that a very high liquefaction susceptibility is found in coincidence with fluvial landforms, a high-to-moderate liquefaction susceptibility within a buffer distance of 100 and 200 m from mapped fluvial landforms and a low liquefaction susceptibility outside fluvial landforms and relative buffer areas. Lidar data allowed a significant improvement in mapping with respect to conventionally available topographic data and/or aerial imagery. These results have significant implications for accurate hazard and risk assessment as well as for land-use planning. We propose a simple geomorphological approach for liquefaction susceptibility estimation. Our findings can be applied to areas beyond Emilia that are characterized by similar fluvial-dominated environments and prone to significant seismic hazard.

  10. Heterogeneity in a Suburban River Network: Understanding the Impact of Fluvial Wetlands on Dissolved Oxygen and Metabolism in Headwater Streams

    NASA Astrophysics Data System (ADS)

    Cain, J. S.; Wollheim, W. M.; Sheehan, K.; Lightbody, A.

    2014-12-01

    Low dissolved oxygen content in rivers threatens fish populations, aquatic organisms, and the health of entire ecosystems. River systems with high fluvial wetland abundance and organic matter, may result in high metabolism that in conjunction with low re-aeration rates, lead to low oxygen conditions. Increasing abundance of beaver ponds in many areas may exacerbate this phenomenon. This research aims to understand the impact of fluvial wetlands, including beaver ponds, on dissolved oxygen (D.O.) and metabolism throughout the headwaters of the Ipswich R. watershed, MA, USA. In several fluvial wetland dominated systems, we measured diel D.O. and metabolism in the upstream inflow, the surface water transient storage zones of fluvial wetland sidepools, and at the outflow to understand how the wetlands modify dissolved oxygen. D.O. was also measured longitudinally along entire surface water flow paths (x-y km long) to determine how low levels of D.O. propagate downstream. Nutrient samples were also collected to understand how their behavior was related to D.O. behavior. Results show that D.O. in fluvial wetlands has large swings with periods of very low D.O. at night. D.O. swings were also seen in downstream outflow, though lagged and somewhat attenuated. Flow conditions affect the level of inundation and the subsequent effects of fluvial wetlands on main channel D.O.. Understanding the D.O. behavior throughout river systems has important implications for the ability of river systems to remove anthropogenic nitrogen.

  11. The Brahmaputra River: a stratigraphic analysis of Holocene avulsion and fluvial valley reoccupation history

    NASA Astrophysics Data System (ADS)

    Hartzog, T. R.; Goodbred, S. L.

    2011-12-01

    The Brahmaputra River, one of the world's largest braided streams, is a major component of commerce, agriculture, and transportation in India and Bangladesh. Hence any significant change in course, morphology, or behavior would be likely to influence the regional culture and economy that relies on this major river system. The history of such changes is recorded in the stratigraphy deposited by the Brahmaputra River during the Holocene. Here we present stratigraphic analysis of sediment samples from the boring of 41 tube wells over a 120 km transect in the upper Bengal Basin of northern Bangladesh. The transect crosses both the modern fluvial valley and an abandoned fluvial valley about 60 km downstream of a major avulsion node. Although the modern Brahmaputra does not transport gravel, gravel strata are common below 20 m with fluvial sand deposits dominating most of the stratigraphy. Furthermore, the stratigraphy preserves very few floodplain mud strata below the modern floodplain mud cap. These preliminary findings will be assessed to determine their importance in defining past channel migration, avulsion frequency, and the reoccupation of abandoned fluvial valleys. Understanding the avulsion and valley reoccupation history of the Brahmaputra River is important to assess the risk involved with developing agriculture, business, and infrastructure on the banks of modern and abandoned channels. Based on the correlation of stratigraphy and digital surface elevation data, we hypothesize that the towns of Jamalpur and Sherpur in northern Bangladesh were once major ports on the Brahmaputra River even though they now lie on the banks of small underfit stream channels. If Jamalpur and Sherpur represent the outer extent of the Brahmaputra River braid-belt before the last major avulsion, these cities and any communities developed in the abandoned braid-belt assume a high risk of devastation if the next major avulsion reoccupies this fluvial valley. It is important to scrutinize the entire Holocene stratigraphic record of Brahmaputra River avulsion and valley reoccupation to provide evidence for the assessment of risk involved with future occurrences. Thomas R. Hartzog, Steven L. Goodbred, Jr., Jennifer L. Pickering, Haley E. Briel, Dhiman R. Mondal, Zobayer Mahmud, Saddam Hossain

  12. Suspended sediment transport trough a large fluvial-tidal channel network

    USGS Publications Warehouse

    Wright, Scott A.; Morgan, Tara

    2015-01-01

    The confluence of the Sacramento and San Joaquin Rivers, CA, forms a large network of interconnected channels, referred to as the Sacramento-San Joaquin Delta (the Delta). The Delta comprises the transition zone from the fluvial influences of the upstream rivers and tidal influences of San Francisco Bay downstream. Formerly an extensive tidal marsh, the hydrodynamics and geomorphology of Delta have been substantially modified by humans to support agriculture, navigation, and water supply. These modifications, including construction of new channels, diking and draining of tidal wetlands, dredging of navigation channels, and the operation of large pumping facilities for distribution of freshwater from the Delta to other parts of the state, have had a dramatic impact on the physical and ecological processes within the Delta. To better understand the current physical processes, and their linkages to ecological processes, the USGS maintains an extensive network of flow, sediment, and water quality gages in the Delta. Flow gaging is accomplished through use of the index-velocity method, and sediment monitoring uses turbidity as a surrogate for suspended-sediment concentration. Herein, we present analyses of the transport and dispersal of suspended sediment through the complex network of channels in the Delta. The primary source of sediment to the Delta is the Sacramento River, which delivers pulses of sediment primarily during winter and spring runoff events. Upon reaching the Delta, the sediment pulses move through the fluvial-tidal transition while also encountering numerous channel junctions as the Sacramento River branches into several distributary channels. The monitoring network allows us to track these pulses through the network and document the dominant transport pathways for suspended sediment. Further, the flow gaging allows for an assessment of the relative effects of advection (the fluvial signal) and dispersion (from the tides) on the sediment pulses as they move through the system. Herein, we present analyses of the “first flush” sediment pulse that occurred on the Sacramento River in December 2012, documenting the transport pathways as well as the effects of advection and dispersion on the sediment as it moved through the fluvial-tidal transition in the Delta. The analyses identified an important transport pathway through the interior of the Delta toward the large pumping facilities in the south Delta, which has important implications for native fish (because their movements are triggered by sediment/turbidity). The results also reveal the dramatic transition from fluvial-dominated transport (advection) to tidal-dominated transport (dispersion) as the sediment pulse approaches the estuary.

  13. Preservation of distributive vs. tributive and other fluvial system deposits in the rock record (Invited)

    NASA Astrophysics Data System (ADS)

    Fielding, C. R.

    2010-12-01

    A recent paper (Weissmann et al., 2010, Geology 38, 39-42) has suggested that deposits of distributive fluvial systems (DFS) “may represent the norm in the continental rock record, with axial and incised river deposits composing a relatively minor proportion of the succession”. Herein, I examine this hypothesis by reference to a number of well-exposed fluvial successions from a variety of basinal settings. The cited paper suggests that DFS dominate modern fluvial landscapes in subsiding sedimentary basins, while acknowledging that many merge into a trunk stream in the basin depocenter. Most of the modern World’s largest rivers, however, are tributive, and many of them preserve significant thicknesses of alluvium beneath and lateral to the modern channel belt. Because DFS are abundant on modern landscapes does not necessarily mean that they will be proportionately well-represented in the ancient. Consideration must also be given to the location within a basin where fluvial systems are most likely to be preserved (the depocenter), and to other factors. DFS (or fluvial/alluvial fans) are commonly developed on the tilted margins of asymmetric basins (hangingwalls of half-grabens and supradetachment basins, transtensional and foreland basins), but not in the depocenters. Symmetrically subsiding basins and long wavelength passive margin basins, however, facilitate development of extensive, very low-gradient plains where trunk streams with tributive or anabranching planforms are typical. Such basins, and the depocenters of asymmetric basins, are most likely to facilitate long-term establishment of trunk systems that have the greatest preservation potential. Incised and/or trunk stream deposits have, furthermore, been interpreted from a large number of ancient examples, some long-lived on timescales of millions of years. In the latter cases it has been argued that tectonic stability of the drainage basin is a key characteristic. A survey of the modern landscape therefore represents only a snapshot of time and one minor component of any climatically- or tectonically-driven cycle. It seems unlikely that DFS dominate alluvial stratigraphy. Criteria for recognition of DFS in the ancient have not yet been fully formulated, but might include 1) a relatively tightly constrained width vs. thickness distribution of channel lithosomes, and 2) lack of outsized channel bodies, in association with 3) centrifugal palaeocurrent distributions, and 4) down-paleoslope decreases in channel body dimensions. Neither these criteria, nor those cited in Weissmann et al. (2010), are necessarily unique to DFS, however. Accordingly, I consider it unlikely that a dominance of DFS in the alluvial rock record could be persuasively demonstrated even it were true.

  14. Fluvial sedimentation on a quivering craton: Influence of slight crustal movements on fluvial processes, upper Jurassic Morrison formation, western Colorado plateau

    USGS Publications Warehouse

    Peterson, F.

    1984-01-01

    One of the most important challenges facing the fluvial sedimentologist is identification of processes outside the stream channel that influence deposition of fluvial sediments. Detailed studies in the lower sequence of the Salt Wash Member (Morrison Formation, Upper Jurassic) demonstrate that crustal deformation at the site of deposition may considerably influence braided-stream processes. Late Jurassic crustal movements in the western part of the Colorado Plateau are interpreted largely from thickness variations and facies distribution, but other features such as vertical repetition of facies, coincidence with at least parts of present-day folds, and the geographic distribution of bedding parameters measured in the fluvial deposits, are also used as corroborating evidence of syndepositional tectonism. These features indicate that several of the large uplifts and basins in the region as well as some of the smaller folds within them were actively moving during deposition of the lower sequence. Tectonic activity altered the stream gradients, which in turn governed sinuosity, flow regime, energy levels, and sediment distribution. Cross-bedding studies indicate that reduced gradients within downwarped areas led to slight increases in sinuosity of the braided-stream channels and of the small sub-channels within them. The lowered gradients apparently resulted in a decrease in the depth of the channels and allowed the streams to flood more readily, producing abundant upper-flow regime horizontal laminations in the channel deposits. In addition, greater quantities of sediment containing higher proportions of sand were deposited in downwarped areas than in positive localities. The inability of the streams to transport bed load through downwarped areas indicates loss of stream energy. However, an increase in the quantity of upper-flow regime horizontal laminations in the same downwarped areas suggests that an increase in flow regime is not necessarily accompanied by an increase in energy levels, at least in regions of slight tectonic activity where the local configuration of the stream channels may change appreciably. Strata presently dip less than 2?? throughout most of the region, and this relatively small amount of deformation reflects the combined effects of Late Jurassic, Cretaceous and Tertiary tectonism. This demonstrates that the amount of structural deformation at the site of deposition may appear to be insignificant, yet it can cause appreciable changes in the nature of braided-stream deposits. ?? 1984.

  15. A fluvial and pluvial probabilistic flood hazard analysis for Can Tho city, Vietnam

    NASA Astrophysics Data System (ADS)

    Apel, Heiko; Martinez, Oriol; Thi Chinh, Do; Viet Dung, Nguyen

    2014-05-01

    Can Tho city is the largest city and the economic heart of the Mekong Delta, Vietnam. Due to its economic importance and envisaged development goals the city grew rapidly in population size and extend over the last two decades. Large parts of the city are located in flood prone areas, and also the central parts of the city recently experienced an increasing number of flood events, both of fluvial and pluvial nature. As the economic power and asset values are constantly increasing, this poses a considerable risk for the city. The the aim of this study is to perform a flood hazard analysis considering both fluvial and pluvial floods and to derive probabilistic flood hazard maps. This requires in a first step an understanding of the typical flood mechanisms. Fluvial floods are triggered by a coincidence of high water levels during the annual flood period in the Mekong Delta with high tidal levels, which cause in combination short term inundations in Can Tho. Pluvial floods are triggered by typical tropical convective rain storms during the monsoon season. These two flood pathways are essentially independent in its sources and can thus be treated in the hazard analysis accordingly. For the fluvial hazard analysis we propose a bivariate frequency analysis of the Mekong flood characteristics, the annual maximum flood discharge Q and the annual flood volume V at the upper boundary of the Mekong Delta, the gauging station Kratie. This defines probabilities of exceedance of different Q-V pairs, which are transferred into synthetic flood hydrographs. The synthetic hydrographs are routed through a quasi-2D hydrodynamic model of the entire Mekong Delta in order to provide boundary conditions for a detailed hazard mapping of Can Tho. This downscaling step is necessary, because the huge complexity of the river and channel network does not allow for a proper definition of boundary conditions for Can Tho city by gauge data alone. In addition the available gauge data around Can Tho are too short for a meaningful frequency analysis. The detailed hazard mapping is performed by a 2D hydrodynamic model for Can Tho city. As the scenarios are derived in a Monte-Carlo framework, the final flood hazard maps are probabilistic, i.e. show the median flood hazard along with uncertainty estimates for each defined level of probabilities of exceedance. For the pluvial flood hazard a frequency analysis of the hourly rain gauge data of Can Tho is performed implementing a peak-over-threshold procedure. Based on this frequency analysis synthetic rains storms are generated in a Monte-Carlo framework for the same probabilities of exceedance as in the fluvial flood hazard analysis. Probabilistic flood hazard maps were then generated with the same 2D hydrodynamic model for the city. In a last step the fluvial and pluvial scenarios are combined assuming independence of the events. These scenarios were also transferred into hazard maps by the 2D hydrodynamic model finally yielding combined fluvial-pluvial probabilistic flood hazard maps for Can Tho. The derived set of maps may be used for an improved city planning or a flood risk analysis.

  16. Simulating the development of Martian highland landscapes through the interaction of impact cratering, fluvial erosion, and variable hydrologic forcing

    NASA Astrophysics Data System (ADS)

    Howard, Alan D.

    2007-11-01

    On the highlands of Mars early in the history of the planet precipitation-driven fluvial erosion competed with ongoing impact cratering. This disruption, and the multiple enclosed basins produced by impacts, is partially responsible for a long debate concerning the processes and effectiveness of fluvial erosion. The role of fluvial erosion in sculpting the early Martian landscape is explored here using a simulation model that incorporates formation of impact craters, erosion by fluvial and slope processes, deposition in basins, and flow routing through depressions. Under assumed arid hydrologic conditions, enclosed basins created by cratering do not overflow, drainage networks are short, and fluvial bajadas infill crater basins with sediment supplied from erosion of interior crater slopes and, occasionally from adjacent steep slopes. Even under arid conditions adjacent crater basins can become integrated into larger basins through lateral erosion of crater rims or by rim burial by sediment infilling. Fluvial erosion on early Mars was sufficient to infill craters of 10 km or more in diameter with 500 1500 m of sediment. When the amount of runoff relative to evaporation is assumed to be larger, enclosed basins overflow and deeply incised valleys interconnect basins. Examples of such overflow and interconnection on the Martian highlands suggest an active hydrological cycle on early Mars, at least episodically. When fluvial erosion and cratering occur together, the drainage network is often disrupted and fragmented, but it reintegrates quickly from smaller impacts. Even when rates of impact are high, a subtle fluvial signature is retained on the landscape as broad, smooth intercrater plains that feature craters with variable amounts of infilling and rim erosion, including nearly buried “ghost” craters. The widespread occurrence of such intercrater plains on Mars suggests a strong fluvial imprint on the landscape despite the absence of deep, integrated valley networks. Indisputable deltas and alluvial fans are rare in the crater basins on Mars, in part because of subsequent destruction of surficial fluvial features by impact gardening and eolian processes. Simulations, however, suggest that temporally-varying lake levels and a high percentage of suspended to bedload supplied to the basins could also result in poor definition of fan delta complexes.

  17. Gully annealing by fluvially-sourced Aeolian sand: remote sensing investigations of connectivity along the Fluvial-Aeolian-hillslope continuum on the Colorado River

    USGS Publications Warehouse

    Sankey, Joel B.; East, Amy E.; Collins, Brian D.; Caster, Joshua

    2015-01-01

    Processes contributing to development of ephemeral gully channels are of great importance to landscapes worldwide, and particularly in dryland regions where soil loss and land degradation from gully erosion pose long-term, land-management problems. Whereas gully formation has been relatively well studied, much less is known of the processes that anneal gullies and impede their growth. This work investigates gully annealing by aeolian sediment, along the Colorado River downstream of Glen Canyon Dam in Glen, Marble, and Grand Canyons, Arizona, USA (Figure 1). In this segment of the Colorado River, gully erosion potentially affects the stability and preservation of archaeological sites that are located within valley margins. Gully erosion occurs as a function of ephemeral, rainfall-induced overland flow associated with intense episodes of seasonal precipitation. Measurements of sediment transport and topographic change have demonstrated that fluvial sand in some locations is transported inland and upslope by aeolian processes to areas affected by gully erosion, and aeolian sediment activity can be locally effective at counteracting gully erosion (Draut, 2012; Collins and others, 2009, 2012; Sankey and Draut, 2014). The degree to which specific locations are affected by upslope wind redistribution of sand from active channel sandbars to higher elevation valley margins is termed “connectivity”. Connectivity is controlled spatially throughout the river by (1) the presence of upwind sources of fluvial sand within the contemporary active river channel (e.g., sandbars), and (2) bio-physical barriers that include vegetation and topography that might impede aeolian sediment transport. The primary hypothesis of this work is that high degrees of connectivity lead to less gullying potential.

  18. [Water birds from Agua Dulce lake and El Ermitaño estuary, Jalisco, Mexico].

    PubMed

    Hernández Vázquez, Salvador

    2005-01-01

    Waterbird abundance, and seasonal and spatial distribution, were studied in two natural water pools at Jalisco, Mexico, from December 1997 through November 1998. Maximum monthly abundance in Agua Dulce lake and El Ermitaño estuary was 86 471 birds (29 686 in Agua Dulce and 56 785 in Ermitaño), with a total cummulative abundance of 179 808 individuals (66 976 in Agua Dulce and 112 832 in Ermitaño). A total of 87 waterbirds species were recorded, 78 in Agua Dulce and 73 in Ermitaño. The higher species richness and abundance was observed during winter, when migratory species arrived. Most species prefered shallow waters, except seabirds which prefered protected areas such as dunes in Agua Dulce. Other groups, like clucks and related species. prefered low salinity areas, for example in the south-east area of Ermitaño. The higher abundance of the shorehirds was found when the water level on the estuary was low. Herons were seen often at areas with high salinity and influenced by tides (e.g. mouth of Ermitaño). PMID:17354436

  19. Unraveling the Interactions between Tidal and Fluvial Flood Wave Signals through the Fluvio-Tidal Transition, Chehalis River, USA

    NASA Astrophysics Data System (ADS)

    Prokocki, E.; Perillo, M. M.; Best, J.; Parsons, D. R.; Simpson, C.; Perillo, G. M.

    2014-12-01

    Bedload and suspended load transport and deposition within the fluvio-tidal zone is governed by the dynamic interplay between fluvially-derived unidirectional currents with bi-directional tidal flows of varying magnitudes that display significant spatio-temporal variation across a range of scales. These fluctuations in the governing hydraulics are represented directly in the differing characteristics of bar forms, bedforms, and silt/clay interbeds within this region that ultimately control the sedimentary facies observed within the fluvio-tidal transitional zone. In this study, we examined seven water surface elevation gages from both NOAA and the USGS located throughout the full expanse (~ 60 km) of the fluvio-tidal zone on the Chehalis River from the river mouth through the "backwater" reach to the fully-fluvial environment where normal flow prevails. Wavelet analysis coupled with computed water surface energy gradients was conducted for both the tidal (i.e. semi-diurnal and diurnal) and fluvial signals at low and high (i.e. flood wave) fluvial discharge conditions that captured all seasonal fluctuations in both the tidal range and fluvial hydrograph. Spatio-temporal analysis of the fluvio-tidal signal along the "backwater" reach shows that for particular hydrodynamic conditions the tidal flows are significantly altered, if not completely dampened, by upstream originating fluvial flood waves, and also displays where fluvial flood wave signals are absorbed by the tidal flow signal (i.e. tidal prism). Furthermore, the results of the above analysis coupled with: (i) salinity measurements, and (ii) suspended sediment concentrations, illuminates in a spatio-temporal context where/when along the "backwater" reach flocculation of fine-grained sediment is expected. Thus, here we will demonstrate how the large-scale hydrodynamics varies throughout the fluvio-tidal zone and will discuss the implications of these results for the preservation potential of sedimentary facies in this region.

  20. 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. PMID:24631916

  1. Facies architecture and sequence stratigraphy of an early post-rift fluvial succession, Aptian Barbalha Formation, Araripe Basin, northeastern Brazil

    NASA Astrophysics Data System (ADS)

    Scherer, Claiton M. S.; Goldberg, Karin; Bardola, Tatiana

    2015-06-01

    The Barbalha Formation (Aptian) records deposition in a fluvial and lacustrine environment accumulated in an early post-rift sag basin. Characterization of the facies architecture and sequence stratigraphic framework of the alluvial succession was carried out through detailed description and interpretation of outcrops and cored wells. The development of depositional sequences in this unit reflects variation in the accommodation-to-sediment supply (A/S) ratio. Two depositional sequences, showing an overall fining-upward trend, are preserved within the succession. The sequences are bounded by regional subaerial unconformities formed during negative A/S ratio, and may be subdivided in Low-accommodation Systems Tracts (LAST) (positive A/S ratio close to zero) and High accommodation Systems Tracts (HAST) (A/S ratio between 0.5 and 1). Sequence 1, with a minimum thickness of 100 m, is characterized by amalgamated, multi-storey, braided fluvial channel sand bodies, defining a LAST. These are interlayered with crevasse splay and floodplain deposits toward the top, passing to open lacustrine deposits, defining a HAST. Sequence 2, with minimum thickness ranging from 50 to 90 m, overlies the organic-rich lacustrine deposits. At the base, this sequence is composed of amalgamated, multistorey braided fluvial channel sand bodies (LAST), similar to Sequence 1, overlain by well-drained floodplain with fixed fluvial channel deposits, interpreted as an anastomosed fluvial system, which are in turn capped by lacustrine deposits, both grouped in a HAST. Paleocurrent data on fluvial deposits of sequences 1 and 2 show a consistent paleoflow to the SE. Sedimentological evidence indicates humid to sub-humid climatic conditions during deposition of sequences 1 and 2. Accumulation of fluvial sequences 1 and 2 was mainly controlled by tectonics. Variation in A/S ratios must be related to tectonic subsidence and uplift of the basin.

  2. Comparing OSL and CN techniques for dating fluvial terraces and estimating surface process rates in Pamir

    NASA Astrophysics Data System (ADS)

    Fuchs, Margret; Gloaguen, Richard; Pohl, Eric; Sulaymonova, Vasila; Merchel, Silke; Rugel, Georg

    2014-05-01

    The quantification of surface process rates is crucial for understanding the topographic evolution of high mountains. Spatial and temporal variations in fluvial incision and basin-wide erosion enable to decipher the role of tectonic and climatic drivers. The Pamir is peculiar in both aspects because of its location at the western end of the India-Asia collision zone, and its position at the edge of two atmospheric circulation systems, the Westerlies and the Indian Summer Monsoon. The architecture of the Panj river network indicates prominent variations across the main tectonic structures of the Pamir. The trunk stream, deflects from the predominantly westward river orientation and cuts across the southern and central Pamir domes before doubling back to the west and leaving the orogen. Optically stimulated luminescence (OSL) dating of fluvial terraces reveals short-term sedimentation along the trunk stream during the last ~25 kyr. The agreement of OSL results to new exposure ages based on the cosmogenic nuclide (CN) 10Be confirms accurate terrace age modelling and treatment of incomplete bleaching. The consistent terrace sedimentation and exposure ages suggest also fast terrace abandonment and rapid onset of incision. Considerable differences in terrace heights reflect high spatial variations of fluvial incision, independent of time interval, change in rock type or catchment increase. Highest rates of (5.9 ± 1.1) mm/yr to (10.0 ± 2.0) mm/yr describe the fluvial dynamic across the Shakhdara Dome and that related to the Darvaz Fault Zone. Lower rates of (3.9 ± 0.6) mm/yr to (4.5 ± 0.7) mm/yr indicate a transient stage north of the Yazgulom Dome. Fluvial incision decreases to rates ranging from (1.7 ± 0.3) mm/yr to (3.9 ± 0.7) mm/yr in graded river reaches associated to southern dome boundaries. The pattern agrees to the interpretation of successive upstream river captures across the southern and central Pamir domes inferred from morphometric analyses of river and valley profiles. Basin-wide erosion rates based on 10Be concentrations in modern fluvial sediments yield relatively consistent rates between (0.61 ± 0.1) mm/yr and (0.75 ± 0.14) mm/yr along the Panj. The increasing Panj catchment averages variations of tributary basins, but minor variations in erosion rates of along-stream sub-basins resemble the pattern of OSL-based incision rates. In contrast, basin-wide erosion rates of tributary basins clearly differentiate between plateau-related sub-basins of (0.05 ± 0.01) mm/yr to (0.17 ± 0.03) mm/yr, and plateau margin-related sub-basins of (0.38 ± 0.06) mm/yr to (1.43 ± 0.26) mm/yr. The differentiation in plateau-related and marginal sub-basins and the northward increase in erosion rates correlate with the 75-percentile of the slope distribution within respective basins and to a minor degree to cumulative annual precipitation.

  3. Agua Caliente Wind/Solar Project at Whitewater Ranch

    SciTech Connect

    Hooks, Todd; Stewart, Royce

    2014-12-16

    Agua Caliente Band of Cahuilla Indians (ACBCI) was awarded a grant by the Department of Energy (DOE) to study the feasibility of a wind and/or solar renewable energy project at the Whitewater Ranch (WWR) property of ACBCI. Red Mountain Energy Partners (RMEP) was engaged to conduct the study. The ACBCI tribal lands in the Coachella Valley have very rich renewable energy resources. The tribe has undertaken several studies to more fully understand the options available to them if they were to move forward with one or more renewable energy projects. With respect to the resources, the WWR property clearly has excellent wind and solar resources. The DOE National Renewable Energy Laboratory (NREL) has continued to upgrade and refine their library of resource maps. The newer, more precise maps quantify the resources as among the best in the world. The wind and solar technology available for deployment is also being improved. Both are reducing their costs to the point of being at or below the costs of fossil fuels. Technologies for energy storage and microgrids are also improving quickly and present additional ways to increase the wind and/or solar energy retained for later use with the network management flexibility to provide power to the appropriate locations when needed. As a result, renewable resources continue to gain more market share. The transitioning to renewables as the major resources for power will take some time as the conversion is complex and can have negative impacts if not managed well. While the economics for wind and solar systems continue to improve, the robustness of the WWR site was validated by the repeated queries of developers to place wind and/or solar there. The robust resources and improving technologies portends toward WWR land as a renewable energy site. The business case, however, is not so clear, especially when the potential investment portfolio for ACBCI has several very beneficial and profitable alternatives.

  4. 76 FR 63614 - Agua Caliente Solar, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-13

    ... Energy Regulatory Commission Agua Caliente Solar, LLC; Supplemental Notice That Initial Market-Based Rate...-referenced proceeding of Agua Caliente Solar, LLC's application for market-based rate authority, with an... above-referenced proceeding are accessible in the Commission's eLibrary system by clicking on...

  5. Digital stereo photogrammetry for grain-scale monitoring of fluvial surfaces: Error evaluation and workflow optimisation

    NASA Astrophysics Data System (ADS)

    Bertin, Stephane; Friedrich, Heide; Delmas, Patrice; Chan, Edwin; Gimel'farb, Georgy

    2015-03-01

    Grain-scale monitoring of fluvial morphology is important for the evaluation of river system dynamics. Significant progress in remote sensing and computer performance allows rapid high-resolution data acquisition, however, applications in fluvial environments remain challenging. Even in a controlled environment, such as a laboratory, the extensive acquisition workflow is prone to the propagation of errors in digital elevation models (DEMs). This is valid for both of the common surface recording techniques: digital stereo photogrammetry and terrestrial laser scanning (TLS). The optimisation of the acquisition process, an effective way to reduce the occurrence of errors, is generally limited by the use of commercial software. Therefore, the removal of evident blunders during post processing is regarded as standard practice, although this may introduce new errors. This paper presents a detailed evaluation of a digital stereo-photogrammetric workflow developed for fluvial hydraulic applications. The introduced workflow is user-friendly and can be adapted to various close-range measurements: imagery is acquired with two Nikon D5100 cameras and processed using non-proprietary "on-the-job" calibration and dense scanline-based stereo matching algorithms. Novel ground truth evaluation studies were designed to identify the DEM errors, which resulted from a combination of calibration errors, inaccurate image rectifications and stereo-matching errors. To ensure optimum DEM quality, we show that systematic DEM errors must be minimised by ensuring a good distribution of control points throughout the image format during calibration. DEM quality is then largely dependent on the imagery utilised. We evaluated the open access multi-scale Retinex algorithm to facilitate the stereo matching, and quantified its influence on DEM quality. Occlusions, inherent to any roughness element, are still a major limiting factor to DEM accuracy. We show that a careful selection of the camera-to-object and baseline distance reduces errors in occluded areas and that realistic ground truths help to quantify those errors.

  6. Analysis on the Characteristics of Fluvial Evolution with Climate Changes from Numerical Simulation

    NASA Astrophysics Data System (ADS)

    Yan, Zhenzhen

    2014-05-01

    Landform evolution is one part of the Earth system behaviors. Products from the landform evolution are faithful records for the global change. They are created by complex interaction between geomorphic processes and environmental factors, and be able to provide the most important and intuitive evidences for investigating the interaction between the Earth's tectonic processes and climate changes. Because of very limited geodetic and geological data, we need a profound understanding of how landscapes respond and erode in response to changes in tectonic or climate boundary conditions. Quantitative study on landform evolution in different spatial and temporal scales using numerical simulation has important scientific interest and practical significance for investigating the nonlinear coupling relationship and response mechanism between tectonic activity, climate change, and surface processes. Under background of the global climate change, rivers have been a major focus of research in landform evolution because they are patently sensitive to tectonic and climate forcing via their channel characteristics. According to the existing research on the channel profiles, in this study, we employ numerical method incorporated with remote sensing techniques to investigate the surface process response to climate-tectonic-landscape through analysis and verification exploration. We build a numerical model based on the theory of geomorphic evolution, and take study on dynamical processes of the channel profile evolution with tectonic and climate boundary. Primary simulation results show that the linear diffusion is not enough to demonstrate the whole evolution. The analyses show that erosion plays a major role in fluvial evolution. Analysis on the dynamic processes of fluvial evolution, clarification its morphological characteristics, and exploration its formation and evolution is helpful for thorough study and understanding the relationship between the various factors of fluvial evolution system, and making forecast for future significant changes in the system with global changes.

  7. The legacy of impact conditions in morphometrics of percussion marks on fluvial bedrock surfaces

    NASA Astrophysics Data System (ADS)

    Wilson, Andrew; Lavé, Jérôme

    2013-03-01

    Percussion, or impact, marks are a common type of bedrock bedform found on many fluvial bedrock channels and have been attributed to bedload impact. Little is known about the conditions under which they form and how these affect morphology and dimensions of impact mark craters. We present data from a set of experiments exploring the formation of percussion marks by bedload impact under controlled conditions (impact velocity, angle, and particle diameter) by quartz spheres onto polished marble plates through a water interface. Particle impact causes impact craters consisting of a central depressed pit and a surrounding raised crater rim under all impact conditions. Data from 699 impact experiments show that crater rims are always circular and crater diameter (ϕc, in m) scales with the kinetic energy of the particle normal to the surface immediately prior to impact (K.E., in J) by the relationship K.E. = 2.48 × 107ϕc3.188. We test this relationship on impact marks produced in a series of controlled flume experiments for a range of surface inclinations found in natural fluvial channel outcrops. Measurements of impact crater diameter were used to estimate K.E. using our empirical equation. Our model estimates very similar K.E. for impact craters produced in this quasinatural setting to those calculated from flume conditions when realistic values for mean impact velocity and mean impact angle are assumed. Applying this relationship to measurements of crater rim diameter in natural settings will allow the mapping of impact K.E. along and across channel reaches where these bedforms are found. Future numerical models of fluvial bedrock erosion based on impact K.E. could be field calibrated from measurements of percussion marks in marble channels or from installed marble slabs in other bedrock channel reaches.

  8. Classification of biological and non-biological fluvial particles using image processing and artificial neural network

    NASA Astrophysics Data System (ADS)

    Shrestha, Bim Prasad; Shrestha, Nabin Kumar; Poudel, Laxman

    2009-04-01

    Particles flowing along with water largely affect safe drinking water, irrigation, aquatic life preservation and hydropower generation. This research describes activities that lead to development of fluvial particle characterization that includes detection of biological and non-biological particles and shape characterization using Image Processing and Artificial Neural Network (ANN). Fluvial particles are characterized based on multi spectral images processing using ANN. Images of wavelength of 630nm and 670nm are taken as most distinctive characterizing properties of biological and non-biological particles found in Bagmati River of Nepal. The samples were collected at pre-monsoon, monsoon and post-monsoon seasons. Random samples were selected and multi spectral images are processed using MATLAB 6.5. Thirty matrices were built from each sample. The obtained data of 42 rows and 60columns were taken as input training with an output matrix of 42 rows and 2 columns. Neural Network of Perceptron model was created using a transfer function. The system was first validated and later on tested at 18 different strategic locations of Bagmati River of Kathmandu Valley, Nepal. This network classified biological and non biological particles. Development of new non-destructive technique to characterize biological and non-biological particles from fluvial sample in a real time has a significance breakthrough. This applied research method and outcome is an attractive model for real time monitoring of particles and has many applications that can throw a significant outlet to many researches and for effective utilization of water resources. It opened a new horizon of opportunities for basic and applied research at Kathmandu University in Nepal.

  9. Analysis of crater valleys, Noachis Terra, Mars: Evidence of fluvial and glacial processes

    NASA Astrophysics Data System (ADS)

    Hobbs, S. W.; Clarke, J. D. A.; Paull, D. J.

    2016-05-01

    The precise mechanism for the formation and evolution of crater valley networks in the Martian southern highlands remains under debate, with precipitation, groundwater flow, and melting induced by impact being suggested. We studied valley networks within four craters of the Noachis Terra highlands that were representative of similar features in Noachis Terra and where orbital data existed for analysis in order to characterise their morphology and infer possible processes involved in their formation and evolution. We found evidence for valleys carved by liquid water and ice-related processes. This included strong evidence of liquid water-based valley formation through melting of ice-rich deposits throughout our study area, suggesting an alternative to previously suggested rainfall or groundwater-based scenarios. The location of these valleys on steeply sloping crater walls, as opposed to the shallow slopes of the highlands where Martian valleys are typically found, suggested that our 'fluvial' valleys had not evolved a more structured fluvial morphology as valley networks found on the Martian plains. Our studied valleys' association with ice-rich material and abundant evidence for erosion caused by downslope flow of ice-rich material are consistent with a cold, wet Mars hypothesis where accumulation, flow, and melting of ice have been dominant factors in eroding crater valleys. Additionally, analysis of valley morphology with slope and aspect suggested a greater dependence on local geology and presence of volatiles than larger valley networks, though ice-related valleys were consistently wider for their length than valleys assessed as fluvial carved. We assessed that local conditions such as climate, geology, and availability of ice-rich material played a major role in the erosion of crater valleys at our study site.

  10. Architecture and Channel-Belt Clustering in the Fluvial lower Wasatch Formation, Uinta Basin, Utah

    NASA Astrophysics Data System (ADS)

    Pisel, J. R.; Pyles, D. R.; Bracken, B.; Rosenbaum, C. D.

    2013-12-01

    The Eocene lower Wasatch Formation of the Uinta Basin contains exceptional outcrops of low net-sand content (27% sand) fluvial strata. This study quantitatively documents the stratigraphy of a 7 km wide by 300 meter thick strike-oriented outcrop in order to develop a quantitative data base that can be used to improve our knowledge of how some fluvial systems evolve over geologic time scales. Data used to document the outcrop are: (1) 550 meters of decimeter to half meter scale resolution stratigraphic columns that document grain size and physical sedimentary structures; (2) detailed photopanels used to document architectural style and lithofacies types in the outcrop; (3) thickness, width, and spatial position for all channel belts in the outcrop, and (4) directional measurements of paleocurrent indicators. Two channel-belt styles are recognized: lateral and downstream accreting channel belts; both of which occur as either single or multi-story. Floodplain strata are well exposed and consist of overbank fines and sand-rich crevasse splay deposits. Key upward and lateral characteristics of the outcrop documented herein are the following. First, the shapes of 243 channels are documented. The average width, thickness and aspect ratios of the channel belts are 110 m, 7 m, and 16:1, respectively. Importantly, the size and shape of channel belts does not change upward through the 300 meter transect. Second, channels are documented to spatially cluster. 9 clusters are documented using a spatial statistic. Key upward patterns in channel belt clustering are a marked change from non-amalgamated isolated channel-belt clusters to amalgamated channel-belt clusters. Critically, stratal surfaces can be correlated from mudstone units within the clusters to time-equivalent floodplain strata adjacent to the cluster demonstrating that clusters are not confined within fluvial valleys. Finally, proportions of floodplain and channel belt elements underlying clusters and channel belts vary with the style of clusters and channel belts laterally and vertically within the outcrop.

  11. Study on fine geological modelling of the fluvial sandstone reservoir in Daqing oilfield

    SciTech Connect

    Zhoa Han-Qing

    1997-08-01

    These paper aims at developing a method for fine reservoir description in maturing oilfields by using close spaced well logging data. The main productive reservoirs in Daqing oilfield is a set of large fluvial-deltaic deposits in the Songliao Lake Basin, characterized by multi-layers and serious heterogeneities. Various fluvial channel sandstone reservoirs cover a fairly important proportion of reserves. After a long period of water flooding, most of them have turned into high water cut layers, but there are considerable residual reserves within them, which are difficult to find and tap. Making fine reservoir description and developing sound a geological model is essential for tapping residual oil and enhancing oil recovery. The principal reason for relative lower precision of predicting model developed by using geostatistics is incomplete recognition of complex distribution of fluvial reservoirs and their internal architecture`s. Tasking advantage of limited outcrop data from other regions (suppose no outcrop data available in oilfield) can only provide the knowledge of subtle changing of reservoir parameters and internal architecture. For the specific geometry distribution and internal architecture of subsurface reservoirs (such as in produced regions) can be gained only from continuous infilling logging well data available from studied areas. For developing a geological model, we think the first important thing is to characterize sandbodies geometries and their general architecture`s, which are the framework of models, and then the slight changing of interwell parameters and internal architecture`s, which are the contents and cells of the model. An excellent model should possess both of them, but the geometry is the key to model, because it controls the contents and cells distribution within a model.

  12. Hydrological and sedimentological variability of the peri-fluvial wetlands of the middle Loire river (France)

    NASA Astrophysics Data System (ADS)

    Gautier, E.; Kunesch, S.; Negrel, P.; Petelet-Giraud, E.

    2003-04-01

    With a catchment basin of 112,120 km^2 and a length of 1012 km, the Loire River is one of the most important fluvial hydrosystems in France. Notwithstanding numerous modifications (dikes, dams, nuclear power plants, gravel extractions), the Loire River hydrology has been saved from a total regularisation. Therefore, the spatial diversity of fluvial landforms creates a patchwork of wetlands: ox-bow lakes, dewatered channels... As one aim of this work was to determine the hydrological and sedimentological processes in the various wetlands, in a context of spatial variability of the fluvial landforms, we used a pluridisciplinarity approach: geomorphology, hydrology, geochemistry. The present study has targeted the functioning between the various hydro-geomorphologic units of the floodplain (main and secondary active channels, abandoned branches and the riverbank [alluvial] and perched aquifers), with regard to the spatial heterogeneity of the different fluxes and the temporal variations of bottom water level, full-bank stage and overflow discharge. In the upper part of the study area, mobile meanders prevail. The meanders migration results in oxbow lakes and the connection between the lakes and the other water reservoirs (e.g. river- and groundwaters) induce a strong lateral variability and a time delayed water input by the river as evidenced by the different geochemical and isotopic signatures. Downstream, the Loire River develops a multiple-channels pattern, of which numerous are abandoned. They are often dewatered along the year, only reconnected to the main channel during the periods of overflow discharges and the influence of the Loire riverwater is progressively substituted by the input of groundwaters (alluvial and perched aquifers). It appears that the submersion duration and the type of connection between the wetlands and the various reservoirs (inlet or outlet connection with the river, connection with the aquifers.) strongly influence the sedimentation rate and granulometric features.

  13. Quantifying fluvial topography using UAS imagery and SfM photogrammetry

    NASA Astrophysics Data System (ADS)

    Woodget, Amy; Carbonneau, Patrice; Visser, Fleur; Maddock, Ian; Habit, Evelyn

    2014-05-01

    The measurement and monitoring of fluvial topography at high spatial and temporal resolutions is in increasing demand for a range of river science and management applications, including change detection, hydraulic models, habitat assessments, river restorations and sediment budgets. Existing approaches are yet to provide a single technique for rapidly quantifying fluvial topography in both exposed and submerged areas, with high spatial resolution, reach-scale continuous coverage, high accuracy and reasonable cost. In this paper, we explore the potential of using imagery acquired from a small unmanned aerial system (UAS) and processed using Structure-from-Motion (SfM) photogrammetry for filling this gap. We use a rotary winged hexacopter known as the Draganflyer X6, a consumer grade digital camera (Panasonic Lumix DMC-LX3) and the commercially available PhotoScan Pro SfM software (Agisoft LLC). We test the approach on three contrasting river systems; a shallow margin of the San Pedro River in the Valdivia region of south-central Chile, the lowland River Arrow in Warwickshire, UK, and the upland Coledale Beck in Cumbria, UK. Digital elevation models (DEMs) and orthophotos of hyperspatial resolution (0.01-0.02m) are produced. Mean elevation errors are found to vary somewhat between sites, dependent on vegetation coverage and the spatial arrangement of ground control points (GCPs) used to georeference the data. Mean errors are in the range 4-44mm for exposed areas and 17-89mm for submerged areas. Errors in submerged areas can be improved to 4-56mm with the application of a simple refraction correction procedure. Multiple surveys of the River Arrow site show consistently high quality results, indicating the repeatability of the approach. This work therefore demonstrates the potential of a UAS-SfM approach for quantifying fluvial topography.

  14. Fluvial Erosion Measurements of Streambank Using Photo-Electronic Erosion Pins (peep)

    NASA Astrophysics Data System (ADS)

    Sutarto, T.; Papanicolaou, T.; Wilson, C. G.; Bertrand, F.

    2010-12-01

    Cohesive streambank erosion is characterized by two main mechanisms, fluvial entrainment of individual particles and bank failure due to gravity (Thorne, 1980). In this study, the relative importance of fluvial erosion (compared to mass failure) was determined in two reaches from different locations of the Clear Creek Watershed (CCW). The main goal of the project was the identification of the key erosion process at each site. Beyond the distinguished flow conditions (hydraulic forces), different stream orders, and land-use, no further attempts were made to identify other key driving agents behind the erosion, such subaerial processes (e.g., seepage, freeze/thaw) acting at the cohesive riverbanks (Lindow et al., 2009). Erosion lengths up to 38 cm were detected. The bank erosion monitoring at high resolution intervals due to the PEEPS allowed for better characterization the fluvial erosion occurring at this site and develop a correspondence between sedigraphs and hydrographs. .Similar statistical methods were used at both sites to support our findings. The moving average identified the dominant trend of the data and the variability of the erosion lengths at the two sites. Further, the use of the Shewhart Charts allowed us to detect the critical erosion events during the period of observation. Finally the overall performance of the PEEPs was evaluated during this study. A correlation analysis was conducted between the direct measurements of traditional methods (e.g., erosion pins, geodetical surveys, measure tape) and the automated data recorded by the PEEP. The maximum error between manual and automated measurements of the exposed length of the PEEPs was less than 27%. The error between the channel survey and the automated PEEP measurements was less than 14%.

  15. Human impacts on headwater fluvial systems in the northern and central Andes

    NASA Astrophysics Data System (ADS)

    Harden, Carol P.

    2006-09-01

    South America delivers more freshwater runoff to the ocean per km 2 land area than any other continent, and much of that water enters the fluvial system from headwaters in the Andes Mountains. This paper reviews ways in which human occupation of high mountain landscapes in the Andes have affected the delivery of water and sediment to headwater river channels at local to regional scales for millennia, and provides special focus on the vulnerability of páramo soils to human impact. People have intentionally altered the fluvial system by damming rivers at a few strategic locations, and more widely by withdrawing surface water, primarily for irrigation. Unintended changes brought about by human activities are even more widespread and include forest clearance, agriculture, grazing, road construction, and urbanization, which increase rates of rainfall runoff and accelerate processes of water erosion. Some excavations deliver more sediment to river channels by destabilizing slopes and triggering processes of mass-movement. The northern and central Andes are more affected by human activity than most high mountain regions. The wetter northern Andes are also unusual for the very high water retention characteristics of páramo (high elevation grass and shrub) soils, which cover most of the land above 3000 m. Páramo soils are important regulators of headwater hydrology, but human activities that promote vegetation loss and drying cause them to lose water storage capacity. New data from a case study in southern Ecuador show very low bulk densities (median 0.26 g cm - 3 ), high organic matter contents (median 43%), and high water-holding capacities (12% to 86% volumetrically). These data document wetter soils under grass than under tree cover. Effects of human activity on the fluvial system are evident at local scales, but difficult to discern at broader scales in the regional context of geomorphic adjustment to tectonic and volcanic processes.

  16. Fluvial sedimentology of a Mesozoic petrified forest assemblage, Shishu Formation, Junggar foreland basin, Xinjiang, China

    SciTech Connect

    McKnight, C.L.; Gan, O.; Carroll, A.R.; Dilcher, D.; Zhao, M.; Liang, Y.H.; Graham, S.A.

    1988-02-01

    The Upper Jurassic(.) Shishu Formation of the eastern Junggar basin, Xinjiang, northwest China, is a fluvial sand unit containing an important assemblage of well-preserved, silicified tree trunks and rooted stumps. Numerous logs, up to 83 ft (25.5 m) long, occur at several levels within a 33.6-ft (10.3 m) stratigraphic section of fluvial sand, gravel, and mud and several paleosol horizons. The uppermost logbearing layer includes a number of rooted tree stumps in growth position, with diameters of up to 8 ft (2.5 m). The maximum root length observed is 40 ft (12.3 m). The trees have been identified by Chinese paleontologists as Cupressinoxylon. The petrified forest assemblage is preserved on the northeast margin of the Mesozoic Junggar foreland basin, a large continental basin subsiding under thrust loading from the south. Logs found within channel gravel units are oriented with their log axes parallel to the channel axis. Sedimentary structures, including epsilon and trough cross-stratification and imbricated channel gravels, indicate paleocurrent flow generally to the south, toward the basin center. The size of the logs suggests the presence of a major fluvial system. The epsilon cross-sets suggest a channel depth of 26 ft (8 m). The oriented silicified logs and their enclosing clastic sediments provide important information on the depositional systems active on the northeastern margin of the Junggar basin in the Late Jurassic(.) time. Hopefully, further detailed study of the fossil trees, including the spacing of the rooted stumps, will provide new information on the paleoecology of Mesozoic forests and the climatic conditions prevailing in the region at the time of deposition.

  17. Fluvial particle characterization using artificial neural network and spectral image processing

    NASA Astrophysics Data System (ADS)

    Shrestha, Bim Prasad; Gautam, Bijaya; Nagata, Masateru

    2008-03-01

    Sand, chemical waste, microbes and other solid materials flowing with the water bodies are of great significance to us as they cause substantial impact to different sectors including drinking water management, hydropower generation, irrigation, aquatic life preservation and various other socio-ecological factors. Such particles can't completely be avoided due to the high cost of construction and maintenance of the waste-treatment methods. A detailed understanding of solid particles in surface water system can have benefit in effective, economic, environmental and social management of water resources. This paper describes an automated system of fluvial particle characterization based on spectral image processing that lead to the development of devices for monitoring flowing particles in river. Previous research in coherent field has shown that it is possible to automatically classify shapes and sizes of solid particles ranging from 300-400 μm using artificial neural networks (ANN) and image processing. Computer facilitated with hyper spectral and multi spectral images using ANN can further classify fluvial materials into organic, inorganic, biodegradable, bio non degradable and microbes. This makes the method attractive for real time monitoring of particles, sand and microorganism in water bodies at strategic locations. Continuous monitoring can be used to determine the effect of socio-economic activities in upstream rivers, or to monitor solid waste disposal from treatment plants and industries or to monitor erosive characteristic of sand and its contribution to degradation of efficiency of hydropower plant or to identify microorganism, calculate their population and study the impact of their presence. Such system can also be used to characterize fluvial particles for planning effective utilization of water resources in micro-mega hydropower plant, irrigation, aquatic life preservation etc.

  18. Patterns of Late Pleistocene proglacial fluvial sedimentation in the SE Lithuanian Plain

    NASA Astrophysics Data System (ADS)

    Blažauskas, Nerijus; Jurgaitis, Algirdas; Šinkūnas, Petras

    2007-01-01

    We investigated proglacial fluvial sedimentation processes in the SE Lithuanian Plain by means of lithofacies analysis. The main parameters on which interpretations were based, were depositional structures of sandy sediments, paleohydraulic parameters and grain-size distribution. The development of the SE Lithuanian Plain illustrates the phenomenal shift of proglacial fluvial sedimentation from outwash plain to ice-marginal river during the ice retreat of the last glaciation. Three facies assemblages of braidplain deposits and two facies assemblages of palaeovalley deposits were distinguished in the sandy plain by means of qualitative and quantitative sedimentological research. This raises the question how the commonly accepted development of a SE orientated outwash plain could turn into an almost perpendicular (SW running) ice-marginal river. The vertical and lateral transitions of outwash plain facies present a classical example of braidplain evolution on slightly inclined lowlands, with well expressed proximal, middle and distal parts. Mid- and side-channel (point-bar) deposits of the proglacial valley point, however, which is unusual for proglacial fluvial systems, to a meandering character of the ice-marginal river. River types of various scale show a change from braided into meandering in the proglacial subenvironment. Lithofacies analysis and paleohydraulic parameters show distinct differences of the hydrodynamic regime during the first stage of the sandy plain development: from sedimentation on an outwash plain in a proglacial valley to sedimentation on a braidplain in a wide ice-marginal valley. The outwash system is characterized by a distinct downstream decrease in energy, whereas the ice-marginal river maintained most of its power and velocity.

  19. Fluvial processes and streamflow variability: Interplay in the scale-frequency continuum and implications for scaling

    NASA Astrophysics Data System (ADS)

    Dodov, Boyko; Foufoula-Georgiou, Efi

    2005-05-01

    This paper explores the links between channel/floodplain morphometry, streamflow variability, and sediment transport across a wide range of scales and frequencies of discharge. On the basis of extensive analysis of observations from a climatologically and geologically homogeneous region in the midwestern United States, we provide evidence that streamflow statistics are significantly affected by the scale-dependent channel/floodplain interactions, which in turn are controlled by (and at the same time actively participate in defining) the dominant fluvial processes at a given scale. More specifically, we document that (1) the channel cross-sectional geometry exerts a strong control on the frequency distributions of both daily and maximum annual discharges; (2) the frequency of exceedance of bank-full discharge is scale dependent (particularly, channels draining large areas flood less often but stay overbank longer than channels draining small areas); (3) the critical area at which the variability of floods with scale changes from increasing to decreasing associates with the scale at which the fluvial regime changes from net-erosional to net-depositional and the floodplain gets well established due to its increased frequency of occupation by the flow; and (4) scaling in suspended sediment load reflects the scaling in channel and floodplain morphometry and depicts the signature of the aforementioned fluvial regime transition. The observation is made that maximum annual floods are composed of two distinct populations, one from below and one from above bank-full flows, and that the quantile at which this transition occurs depends on scale. On the basis of this observation, the notion of statistical multiscaling of floods is reexamined.

  20. Investigation of fluvial landforms in the north-eastern Pannonian Basin, using cartographic materials from the XIX-XXI Centuries

    NASA Astrophysics Data System (ADS)

    Robu, Delia; Niga, Bogdan; Perşoiu, Ioana

    2015-04-01

    The study area is located in the north-eastern Pannonian Basin, and covers approximately 3700 km2. Using cartographic materials for the last 155 years, we analyzed and defined river network and relict fluvial morphologies created by the rivers Tur, Someş, Homorod and Crasna. Database extraction from each set of historical maps was performed by field verification and validation, associated to GIS techniques. Relict fluvial morphologies on the Someş alluvial cone comprise a wide variety of channel typologies and sizes, drainage directions and their consequent typology, which indicates a complex fluvial evolution. The dominant category of relict fluvial morphology is represented by the meander loop. Following the quantitative analysis on the successive sets of maps we identified and delimited meander loops and meandering paths formed prior to the reference year 1860. Generally, the post-1860 relict fluvial morphologies are secondary morphologies, as the keynote is given by those formed previous to the reference moment 1860. An analysis of the share of the relict fluvial morphologies on the three sets of reference cartographic materials (the second Austro-Hungarian topographic survey, Google Earth and orthophotoplans) highlights that most relict fluvial morphologies were identified on the second Austro-Hungarian topographic survey, followed by those identified in Google Earth and orthophotoplans. The map of fluvial morphologies constructed in this study enables a discussion on drainage directions, based on the observation that a series of abandoned meander loops and segments follow clear directions. We applied several quantitative indices in assessing the relict fluvial morphology (radius of curvature, paleochannel width). Consequently, we identified underfit stream sectors with meander loops larger than the modern ones Someş meanders (on the Racta River), uncharacteristic features such as braided riverbed reaches, a high frequency of meander scrolls present on the right bank of Crasna at its entrance in the plain, or the occurrence of wetlands in an area affected by subsidence (the Ecedeea Plain). Despite the ample human intervention in our study area through sewers, dams, meander cuts, the river network evolution trend remained the same between 1860 and 2005, with evolution and formation of meanders, although the change rate has diminished. "ACKNOWLEDGMENT This paper has been financially supported within the project entitled "SOCERT. Knowledge society, dynamism through research", contract number POSDRU/159/1.5/S/132406. This project is co-financed by European Social Fund through Sectoral Operational Programme for Human Resources Development 2007-2013. Investing in people!"

  1. Multiple Epochs of Fluvial Denudation in a Changing Climate on Early Mars

    NASA Astrophysics Data System (ADS)

    Irwin, R. P.

    2011-12-01

    Studies of degraded impact craters and valley networks have shown that Mars experienced a severe climate change around the end of the Noachian Period, but the decline in landscape denudation appears to be complex. Prolonged, ubiquitous Noachian crater degradation included smoothing of the crater rims and ejecta, wall backwasting, and infilling. Late Noachian valley networks are also widespread but more limited in many aspects of their development, suggesting relatively short-lived activity or arid conditions by terrestrial standards. Younger fluvial features that appear to have more limited spatial distributions may reflect later clement environments on some parts of the planet. However, distinguishing post-Noachian fluvial erosion is challenging, because it requires slopes such as volcanoes, tectonic scarps, crater rims, or airfall deposits that can be convincingly dated to the Hesperian or later. Moreover, the slope or contributing surface must have been large enough to generate erosive quantities of runoff. Several locations described in the literature meet these conditions. Most large alluvial fans occur in Late Noachian to Hesperian craters within the 15-30° south band. In Margaritifer Terra, recent studies show that large alluvial deposits significantly post-date Late Noachian valley networks. A speculative possible explanation involves seasonal precipitation (snowmelt, rain, or both) that generated more runoff in this latitude band than elsewhere, sometime during the Late Hesperian to Early Amazonian Epochs. Gale crater crosscuts the Early Hesperian crustal dichotomy boundary scarp, but a valley network south of the crater appears to have reactivated sometime after the Gale impact and breached the crater rim. Late Noachian valley networks in Aeolis Mensae are hanging with respect to the boundary scarp but exhibit some later dissection and knickpoint propagation. Late fluvial activity in Valles Marineris and some Tharsis volcanoes has also been described, as has dissection of a deposit in the Electris region. Whether these features represent concurrent activity of global scale or a variety of local short-lived environments is not known. Estimates of the dominant discharge for fluvial channels are not consistent with intense meteorological floods, but perhaps with up to cm/day runoff production from watersheds. In Eberswalde crater, the best-constrained case, meandering inverted channels on the delta surface reflect a dominant discharge of hundreds of cubic meters per second and event runoff production up to 1 cm/day, but annual runoff production of <10 cm/yr was necessary to maintain the lake level. In nearby Holden crater, inverted channels on alluvial fans suggest transport of finer-grained sediment, which does not require intense runoff. These and other sites suggest that any late clement interval on Mars was not necessarily very wet relative to Earth.

  2. Fluvial filtering of land-to-ocean fluxes: from natural Holocene variations to Anthropocene

    NASA Astrophysics Data System (ADS)

    Meybeck, Michel; Vörösmarty, Charles

    2005-02-01

    The evolution of river systems and their related fluxes is considered at various time scales: ( i) over the last 18 000 years, under climatic variability control, ( ii) over the last 50 to 200 years (Anthropocene) due to direct human impacts. Natural Holocene variations in time and space depend on ( i) land-to-ocean connections (endorheism, glacial cover, exposure of continental shelf); ( ii) types of natural fluvial filters (e.g., wetlands, lakes, floodplains, estuaries). Anthropocene changes concern ( i) land-ocean connection (e.g., partial to total runoff reduction resulting from water management), ( ii) modification and removal of natural filters, ( iii) creation of new filters, particularly irrigated fields and reservoirs, ( iv) acceleration and/or development of material sources from human activities. The total river basin area directly affected by human activities is of the same order of magnitude ( >40 Mkm) as the total area affected over the last 18 000 years. A tentative analysis of 38 major river systems totaling 55 Mkm is proposed for several criteria: ( i) trajectories of Holocene evolution, ( ii) occurrence of natural fluvial filters, ( iii) present-day fluvial filters: most river basins are unique. Riverine fluxes per unit area are characterized by hot spots that exceed the world average by one order of magnitude. At the Anthropocene (i.e., since 1950), many riverine fluxes have globally increased (sodium, chloride, sulfate, nitrogen, phosphorous, heavy metals), others are stable (calcium, bicarbonate, sediments) or likely to decrease (dissolved silica). Future trajectories of river fluxes will depend on the balance between increased sources of material (e.g., soil erosion, pollution, fertilization), water abstraction for irrigation and the modification of fluvial filters, particularly the occurrence of reservoirs that already intercept half of the water and store at least 30% of river sediment fluxes. In some river systems, retention actually exceeds material production and river fluxes are actually decreasing. These trajectories are specific to each river and to each type of river material. Megacities, mining and industrial districts can be considered as hot spots of contaminants fluxes, while major reservoirs are global-scale sinks for all particulates. Global picture should therefore be determined at a fine resolution, since regional differences in Anthropocene evolution of river fluxes may reach one order of magnitude, as illustrated for total nitrogen. To cite this article: M. Meybeck, C. Vörösmarty, C. R. Geoscience 337 (2005).

  3. Computer programs for computing particle-size statistics of fluvial sediments

    USGS Publications Warehouse

    Stevens, H.H.; Hubbell, D.W.

    1986-01-01

    Two versions of computer programs for inputing data and computing particle-size statistics of fluvial sediments are presented. The FORTRAN 77 language versions are for use on the Prime computer, and the BASIC language versions are for use on microcomputers. The size-statistics program compute Inman, Trask , and Folk statistical parameters from phi values and sizes determined for 10 specified percent-finer values from inputed size and percent-finer data. The program also determines the percentage gravel, sand, silt, and clay, and the Meyer-Peter effective diameter. Documentation and listings for both versions of the programs are included. (Author 's abstract)

  4. The human role in changing fluvial systems: Retrospect, inventory and prospect

    NASA Astrophysics Data System (ADS)

    James, L. Allan; Marcus, W. Andrew

    2006-09-01

    Historical and modern scientific contexts are provided for the 2006 Binghamton Geomorphology Symposium on the Human Role in Changing Fluvial Systems. The 2006 symposium provides a synthesis of research concerned with human impacts on fluvial systems — including hydrologic and geomorphic changes to watersheds — while also commemorating the 50th anniversary of the 1955 Man's Role in Changing the Face of the Earth Symposium [Thomas, Jr., W. L. (Ed.), 1956a. Man's Role in Changing the Face of the Earth. Univ. Chicago Press, Chicago. 1193 pp]. This paper examines the 1955 symposium from the perspective of human impacts on rivers, reviews current inquiry on anthropogenic interactions in fluvial systems, and anticipates future directions in this field. Although the 1955 symposium did not have an explicit geomorphic focus, it set the stage for many subsequent anthropogeomorphic studies. The 1955 conference provided guidance to geomorphologists by recommending and practicing interdisciplinary scholarship, through the use of diverse methodologies applied at extensive temporal and geographical scales, and through its insistence on an integrated understanding of human interactions with nature. Since 1956, research on human impacts to fluvial systems has been influenced by fundamental changes in why the research is done, what is studied, how river studies are conducted, and who does the research. Rationales for river research are now driven to a greater degree by institutional needs, environmental regulations, and aquatic restoration. New techniques include a host of dating, spatial imaging, and ground measurement methods that can be coupled with analytical functions and digital models. These new methods have led to a greater understanding of channel change, variations across multiple temporal and spatial scales, and integrated watershed perspectives; all changes that are reflected by the papers in this volume. These new methods also bring a set of technical demands for the training of geomorphologists. The 2006 Binghamton Geomorphology Symposium complements the 1956 symposium by providing a more specific and updated view of river systems coupled with human interactions. The symposium focuses on linkages between human land use, structures, and channel modification with geomorphology, hydrology, and ecology. The emergence of sustainability as a central policy guideline in environmental management should generate greater interest in geomorphic perspectives, especially as they pertain to human activities. The lack of theories of anthropogeomorphic change, however, presents a challenge for the next generation of geomorphologists in this rapidly growing subfield.

  5. Hydrological and sedimentological regime of lower Vistula fluvial lakes (North Central Poland)

    NASA Astrophysics Data System (ADS)

    Kordowski, Jarosław; Kubiak-Wójcicka, Katarzyna; Tyszkowski, Sebastian; Solarczyk, Adam

    2015-04-01

    Regarding the outflow the Vistula River is the largest river in the Baltic catchment. In its lower course it has developed an anastomosing channel pattern modified strongly by intensive human hydrotechnical activity and by the regulation which have intensified about 200 years ago. Channel regulation apart from already existing lakes have left many new artificially created ones. This activity have also altered the hydrological and sedimentary regime. It turned out that only the small portion of the lakes infilled rapidly but the majority have persisted to present day almost unchanged in spite of regulation. The reason of this resistence to silting is connected with specific interaction of sediment removing during high flood water episodes and strong groundwater circulation in former river arms transformed in present-day lakes. As an example of a lake with an intensive groundwater exchange rate with the main Vistula channel and supposed Quaternary and Tertiary aquifers was selected the Old Vistula lake (Stara Wisła) near Grudziądz town. It has got an area of 50 ha, mean depth 1,73 m, maximum depth 8 m, length about 4 km and medium width about 100 m. In the years 2011-2015 in its surficial water were conducted measures with two weeks frequency which included: temperature, pH, Eh, suspended matter amount, total and carbonaceous mineralization. For comparison similar measurements were also conducted in other fluvial lakes and Vistula tributaries. Hydrological data were supplemented by geological investigations of floodplain sediments cover which has important impact on the rate of groundwater migration and circulation. Investigations carried proved that there exists distinct gradient of carbonaceous mineralization from small values in the Vistula channel to high values at the valley edges. PH and Eh parameters in the Old Vistula lake were different than in all other surveyed sites what leads to conclusion that it is fed by deeper groundwaters than in the case of other fluvial lakes and Vistula tributaries, particularly in low water stand times. This is because it has not continuous flood sediments cover on its floor. The sediments accumulated during the low stands of water are removed from fluvial lakes while high stands by flood waters. Temporarily deposited sediment is also removed due to high groundwater "exchange" rate when the fluvial lake has a sufficient hydrological connectivity to the main Vistula channel. Acknowledgements: This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution (ICLEA) of the Helmholtz Association.

  6. Stream capture and piracy recorded by provenance in fluvial fan strata

    NASA Astrophysics Data System (ADS)

    Mikesell, Leslie R.; Weissmann, Gary S.; Karachewski, John A.

    2010-03-01

    Stream capture and piracy in tectonically active regions have been described in geomorphic systems worldwide; however, few studies show the influence stream capture has on the rock record. We present an analysis of fluvial fan stratigraphy that developed as a result of multiple stream capture events, building a complex stratigraphic succession beneath the Lawrence Livermore National Laboratory (LLNL), California. The LLNL site is located in the southeast portion of the tectonically active Livermore Basin, a transpressional basin in the California Coast Ranges. Geomorphic evidence for this stream capture include: (1) the Arroyo Seco enters the basin from the south through an uplifted fault block, (2) south of this fault block lies an abandoned Arroyo Seco fluvial fan, (3) north of the fault block, in the Livermore Basin, Arroyo Seco built a 7-km 2 fluvial fan, apparently forcing the Arroyo Las Positas, a smaller stream that enters the basin from the east, northward around the Arroyo Seco fan, and (4) a knickpoint exists near the point of capture on Arroyo Seco. Stratigraphic evidence reflecting this shift in the Arroyo Seco position into the Livermore Basin was evaluated through a provenance study of 215 gravel units from 34 boreholes spaced evenly over the 2.6 km 2 LLNL site. The Arroyo Seco derives its sediment from both the Jurassic-Cretaceous Franciscan Assemblage and the Altamont Hills (which are comprised of Mesozoic Great Valley Group and Tertiary continental sediments). The Arroyo Las Positas drains only the Altamont Hills and thus lacks the Franciscan Assemblage-derived clasts. The origin of the individual gravel units was determined by the percentage of Franciscan Assemblage indicator pebbles (red chert, green chert and blueschist) in the samples. Through this analysis, we determined that high-percentage Franciscan Assemblage-derived clasts were present below a depth of approximately 35 m below the surface, low-percentage Franciscan Assemblage-derived clasts were present at depths between 35 m and 18 m, and high-percentage Franciscan Assemblage-derived clasts were present from depths of approximately 18 m to the surface of the fluvial fan. These results indicate that the Arroyo Seco flowed north and deposited sediments at the LLNL site, then was later absent from the basin at which time it formed a fan south of the fault block. During this absence of the Arroyo Seco, the Arroyo Las Positas, a westerly flowing stream, dominated the sediment supply at the LLNL site. The Arroyo Seco was then captured by a gully headward eroding through the uplifted fault block, redirecting the Arroyo Seco into the basin once again. This history of multiple stream captures created three stratigraphic units with alternating overall channel and paleoflow orientations.

  7. Comparison of knobs on Mars to isolated hills in eolian, fluvial and glacial environments

    NASA Technical Reports Server (NTRS)

    Manent, L. S.; El-Baz, F.

    1986-01-01

    The isolated knobs of Mars, characterized in terms of length, width, geographic location, proximity to streaks, and geologic surroundings through Viking Orbiters' photomosaics, are compared to isolated hills on earth eroded by eolian, fluvia, and glacial processes. Comparison of length-to-width ratios indicates similarity of the knobs to the hills formed in a hyperarid environment. The hills formed on earth by fluvial and glacial processes have length-to-width ratios significantly higher than those of the Martian knobs and have other diagnostic features not associated with the knobs. Moreover, streaks, splotches, dunes, and pitted and fluted rocks, all indicative of an eolian regime, are associated with the Martian knobs.

  8. Stochastic Modeling of Vegetation Growth, Mortality and Invasion in a Fluvial Floodplain in Interaction with Floods

    NASA Astrophysics Data System (ADS)

    Miyamoto, Hitoshi; Toshimori, Nobuhiko; Kimura, Ryo

    2013-04-01

    Vegetation overgrowth in fluvial floodplains and sand bars has become a serious engineering problem for riparian management in Japan. From both viewpoints of flood control and ecological conservation, it would be necessary to predict the vegetation dynamics accurately for long-term duration. In this research, we have tried to develop a stochastic model for predicting the dynamics of trees in fluvial floodplains with emphasis on the interaction with flood impacts. The model consists of the following four components: (i) long-term stochastic behavior of flow discharge, (ii) hydrodynamics in a channel with floodplain vegetation, (iii) variation of riverbed topography, and (iv) vegetation dynamics on floodplains. In the model, the flood discharge is stochastically simulated using a filtered Poisson process, one of the conventional approaches in hydrological time-series generation. The modeling for vegetation dynamics includes the effects of tree growth, mortality by flood impacts, and infant tree invasion. Vegetation condition has been observed mainly before and after flood impacts since 2008 at a field site located between 23.2-24.0 km from the river mouth in Kako River, Japan. The Kako River has the catchment area of 1,730 km2 and the main channel length of 96 km. This site is one of the vegetation overgrowth locations in the Kako River floodplains, where the predominant tree species are willows and bamboos. In the field survey, the position, trunk diameter and height of each tree as well as the riverbed materials were measured after several flood events to investigate their impacts on the floodplain vegetation community. In this presentation, the three effects in vegetation dynamics, i.e., the tree growth rate, mortality, and infant tree invasion, are refined for improving the model predictability. The growth rate curve proposed here is derived by introducing inhibition effect of larger trees into the conventional Richards growth curve. As for the mortality rate, Gaussian distribution is used to represent randomness of tree damage due to differences of individual tree conditions on fluvial floodplains. The infant tree invasion is modeled by taking both seed propagation and vegetative reproduction into account. The results of the present model for the fluvial floodplain in Kako River confirm the high applicability of the present refinement and its optimal model parameters for predicting current vegetation distributions in the floodplain.

  9. New insights from DEM's into form, process and causality in Distributive Fluvial Systems

    NASA Astrophysics Data System (ADS)

    Scuderi, Louis; Weissmann, Gary; Hartley, Adrian; Kindilien, Peter

    2014-05-01

    Recent developments in platforms and sensors, as well as advances in our ability to access these rich data sources in near real time presents geoscientists with both opportunities and problems. We currently record raster and point cloud data about the physical world at unprecedented rates with extremely high spatial and spectral resolution. Yet the ability to extract scientifically useful knowledge from such immense data sets has lagged considerably. The interrelated fields of database creation, data mining and modern geostatistics all focus on such interdisciplinary data analysis problems. In recent years these fields have made great advances in analyzing the complex real-world data such as that captured in Digital Elevation Models (DEM's) and satellite imagery and by LIDAR and other geospatially referenced data sets. However, even considering the vast increase in the use of these data sets in the past decade these methods have enjoyed only a relatively modest penetration into the geosciences when compared to data analysis in other scientific disciplines. In part, a great deal of the current research weakness is due to the lack of a unifying conceptual approach and the failure to appreciate the value of highly structured and synthesized compilations of data, organized in user-friendly formats. We report on the application of these new technologies and database approaches to global scale parameterization of Distributive Fluvial Systems (DFS) within continental sedimentary basins and illustrate the value of well-constructed databases and tool-rich analysis environments for understanding form, process and causality in these systems. We analyzed the characteristics of aggradational fluvial systems in more than 700 modern continental sedimentary basins and the links between DFS within these systems and their contributing drainage basins. Our studies show that in sedimentary basins, distributive fluvial and alluvial systems dominate the depositional environment. Consequently, we have found that studies of modern tributary drainage systems in degradational settings are likely insufficient for understanding the geomorphology expressed within these basins and ultimately for understanding the basin-scale architecture of dominantly distributive fluvial deposits preserved in the rock record.

  10. Progressive changes in the morphology of fluvial terraces and scarps along the Rappahannock River, Virginia.

    USGS Publications Warehouse

    Colman, Steven M.

    1983-01-01

    Progressive geomorphic changes in the flight of fluvial terraces along the Rappahannock River, Virginia, provide a framework for analysing the effect of time on landforms. Indices of terrace preservation, especially drainage densities and area to perimeter ratios, show systematic changes with terrace age. Higher scarps tend to have steeper slopes and, for a given scarp height, older scarps tend to have gentler slopes. Depositional features such as bars and channels with 1-3m of relief are preserved on terraces on the order of 105 yr old.-from Author

  11. Late Holocene fluvial activity and correlations with dendrochronology of subfossil trunks: Case studies of northeastern Romania

    NASA Astrophysics Data System (ADS)

    Rădoane, Maria; Nechita, Constantin; Chiriloaei, Francisca; Rădoane, Nicolae; Popa, Ionel; Roibu, Cătălin; Robu, Delia

    2015-06-01

    The main objective of this paper is to describe the late Holocene behaviour of rivers using an interdisciplinary approach combining fluvial geomorphology and subfossil trunk dendrochronology. The subfossil wood material collected along the rivers was investigated for dendrometric and dendrochronologic parameters. The research methods in these fields helped us to understand the effect of the fluvial environment on riparian trees and their records and helped in reconstructing the riparian palaeoenvironment. The study area consists of two rivers with different typologies but comparable sizes: the Moldova River, which features a braided to wandering channel in its lower reach, and the Siret River, which features a sinuous-meandering channel. Along the 100-km-long floodplain of the former and the 144-km-long floodplain of the latter, we found and sampled 77 subfossil trunks, of which 26 were subjected to 14C dating. The resulting data consist of floodplain facies mapping data, electric resistivity measurements, absolute dates, and dendrometric and dendrochronologic data. The results indicate that during a 100-year period, the two rivers were sensitive to climate change and anthropogenic effects, particularly a narrowing of the active channel by 76% in the braided channel and 38% in the sinuous-meandering channel. During the past 3300-3000 YBP, the Moldova River maintained its braided style, whereas the sinuous-meandering style has been characteristic of the Siret River for the previous 6800-4600 YBP. The two distinct fluvial environments are recorded in the dendrometric structure of the trunks buried in the channel-fill sediments. The braided fluvial environment was more effective in uprooting riparian trees and incorporating them in the floodplain deposits, whereas the sinuous-meandering style of stream effectively buried tree trunks in lateral accretion lobes. Absolute and dendrochronologic dating allowed for the reconstruction of timelines of the felling of the trees and estimates of the magnitude of the responsible hydrological event. The flood events on the Siret River with a recurrence interval of 200 years (Qmax ~ 2500-2800 m3/s) were those most effective in destroying riparian forests, and the events on the Moldova floods with a 100-year recurrence interval (Qmax ~ 1200-1400 m3/s) were the most effective. Dendrochronology allowed for identification of wet phases (i.e., 3500-2900 YBP, 2200-2075 YBP, and 1000-800 YBP) and dry phases (e.g., 3200-3150 or 2775-2700 YBP, 1400 YBP). Finally, we draw attention to the potential for creating a highly replicable dendrochronological series spanning at least 7000 YBP.

  12. 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.

  13. Unraveling past aeolian and fluvial inputs off NW Africa - a magnetic, sedimentological and geochemical perspective

    NASA Astrophysics Data System (ADS)

    Just, J.; Dekkers, M. J.; Heslop, D.; von Dobeneck, T. F.

    2012-12-01

    The properties of marine terrigenous sediments are widely used for paleo-environmental reconstructions. Here we adopt three sets of proxy parameters to unravel the eolian and fluvial contributions to a sedimentary archive off Gambia (NW Africa) during the past 70 kyrs at 300-500 years resolution. The proxies include: grain-size distributions, major elements, and magnetic properties, more specifically acquisition curves of isothermal remanent magnetization (IRM). Elemental ratios of terrigenous sediments are, similar as the pedogenic magnetic mineral assemblage, sensitive to environmental conditions during weathering. The grain-size distribution of the terrigenous fraction can provide information about the different pathways for terrigenous sediments and transport energy. If the magnetic mineral content in marine sediments is interpreted in terms of changing proportions of eolian and fluvial material, post-depositional processes such as authigenic mineral formation, dissolution, or biomineralization must be considered. Assessing end-member (EM) contributions to the magnetic mineral assemblage constitutes the first step of the present investigation. Dissolution is easily detected by low concentrations of magnetic minerals, two orders of magnitude lower than in unaffected sediment intervals. EM unmixing of the IRM acquisition curves shows that the remaining magnetic assemblage becomes harder, as documented in earlier studies. Bacterial magnetite is often considered a subordinate magnetic mineral phase in continental margin sediments because of dilution by terrigenous material and due to its low potential for preservation in sulfidic environments. Unexpectedly, EM unmixing prompted the importance of bacterial magnetite in our record: it is well-preserved below the present iron redox boundary and carries up to 60% of saturation IRM. Its presence was confirmed by transmission electron microscopy. Ignoring potential contributions of bacterial magnetite can lead to erroneous conclusions concerning terrestrial paleoclimatic conditions. In the second stage of the study, EM unmixing was performed on grain-size and element data sets. We compared and cross-validated these single-parameter EM systems and developed a numerical strategy to calculate so-called associated multi-parameter properties of eolian and fluvial EMs. We preprocessed the IRM data by subtracting the IRM curves of the bacterial EM to obtain acquisition curves that solely represent the terrigenous fraction. Peak contributions of the eolian EM appear to faithfully reproduce periods of increased dust export from the continent during Heinrich Stadials. Changing proportions of fine- and coarse-grained fluvial EMs are linked to sea-level variations and precipitation in the hinterland. The integration of the different proxies into a joint multi-proxy EM system leads to a full characterization of environmental conditions and processes affecting the marine terrigenous record from source-to-sink.

  14. Selective deposition response to aeolian-fluvial sediment supply in the desert braided channel of the upper Yellow River, China

    NASA Astrophysics Data System (ADS)

    Wang, H.; Jia, X.; Li, Y.; Peng, W.

    2015-09-01

    Rivers flow across aeolian dunes and develop braided stream channels. Both aeolian and fluvial sediment supplies regulate sediment transport and deposition in such cross-dune braided rivers. Here we show a significant selective deposition in response to both aeolian and fluvial sediment supplies in the Ulan Buh desert braided channel. The Ulan Buh desert is the main coarse sediment source for this desert braided channel, and the mean percentage of the coarser (> 0.08 mm) grains on the aeolian dunes surface is 95.34 %. The lateral selective deposition process is developed by the interaction between the flows and the aeolian-fluvial sediment supplies, causing the coarser sediments (> 0.08 mm) from aeolian sand supply and bank erosion to accumulate in the channel centre and the finer fluvial sediments (< 0.08 mm) to be deposited on the bar and floodplain surfaces, forming a coarser-grained thalweg bed bounded by finer-grained floodplain surfaces. This lateral selective deposition reduces the downstream sediment transport and is a primary reason for the formation of an "above-ground" river in the braided reach of the upper Yellow River in response to aeolian and fluvial sediment supplies.

  15. Fluvial and glacial implications of tephra localities in the western Wind River basin, Wyoming, U. S. A

    SciTech Connect

    Jaworowski, C. . Dept. of Geology)

    1993-04-01

    Examination of Quaternary fluvial and glacial deposits in the western Wind River Basin allows a new understanding of the Quaternary Wind River fluvial system. Interbedded fluvial sediments and volcanic ashes provide important temporal information for correlation of Quaternary deposits. In the western Wind River Basin, six mid-Pleistocene localities of tephra, the Muddy Creek, Red Creek, Lander, Kinnear, Morton and Yellow Calf ashes are known. Geochronologic studies confirm the Muddy Creek, Red Creek, Kinnear and Lander ashes as the 620--650ka Lava Creek tephra from the Yellowstone region in northwestern Wyoming. The stratigraphic position and index of refraction of volcanic glass from the Morton and Yellow Calf ashes are consistent with identification as Lava Creek tephra. Approximately 350 feet (106 meters) above the Wind River and 13 miles downstream from Bull Lake, interbedded Wind River fluvial gravels, volcanic glass and pumice at the Morton locality correlate to late (upper) Sacajawea Ridge gravels mapped by Richmond and Murphy. Associated with the oxygen isotope 16--15 boundary, the ash-bearing terrace deposits reveal the nature of the Wind River fluvial system during late glacial-early interglacial times. The Lander and Yellow Calf ashes, are found in terrace deposits along tributaries of the Wind River. Differences in timing and rates of incision between the Wind River and its tributary, the Little Wind River, results in complex terrace development near their junction.

  16. The source, discharge, and chemical characteristics of water from Agua Caliente Spring, Palm Springs, California

    USGS Publications Warehouse

    : Martin, Peter, (Edited By); Contributors: Brandt, Justin; Catchings, Rufus D.; Christensen, Allen H.; Flint, Alan L.; Gandhok, Gini; Goldman, Mark R.; Halford, Keith J.; Langenheim, V.E.; Martin, Peter; Rymer, Michael J.; Schroeder, Roy A.; Smith, Gregory A.; Sneed, Michelle

    2011-01-01

    Numerical models of fluid and temperature flow were developed for the Agua Caliente Spring to (1) test the validity of the conceptual model that the Agua Caliente Spring enters the valley-fill deposits from fractures in the underlying basement complex and rises through more than 800 feet of valley-fill deposits by way of a washed-sand conduit and surrounding low-permeability deposits (spring chimney) of its own making, (2) evaluate whether water-level declines in the regional aquifer will influence the temperature of discharging water, and (3) determine the source of thermal water in the perched aquifer. A radial-flow model was used to test the conceptual model and the effect of water-level declines. The observed spring discharge and temperature could be simulated if the vertical hydraulic conductivity of the spring orifice was about 200 feet per day and the horizontal hydraulic conductivity of the orifice (spring chimney) was about 0.00002 feet per day. The simulated vertical hydraulic conductivity is within the range of values reported for sand; however, the low value simulated for the horizontal hydraulic conductivity suggests that the spring chimney is cemented with increasing depth. Chemical data collected for this study indicate that the water at Agua Caliente Spring is at saturation with respect to both calcite and chalcedony, which provides a possible mechanism for cementation of the spring chimney. A simulated decline of about 100 feet in the regional aquifer had no effect on the simulated discharge of Agua Caliente Spring and resulted in a slight increase in the temperature of the spring discharge. Results from the radial-flow- and three-dimensional models of the Agua Caliente Spring area demonstrate that the distribution and temperature of thermal water in the perched water table can be explained by flow from a secondary shallow-subsurface spring orifice of the Agua Caliente Spring not contained by the steel collector tank, not by leakage from the collector tank.

  17. Episodic ocean-induced CO2 greenhouse on Mars: implications for fluvial valley formation.

    PubMed

    Gulick, V C; Tyler, D; McKay, C P; Haberle, R M

    1997-11-01

    Pulses of CO2 injected into the martian atmosphere more recently than 4 Ga can place the atmosphere into a stable, higher pressure, warmer greenhouse state. One to two bar pulses of CO2 added to the atmosphere during the past several billion years are sufficient to raise global mean temperatures above 240 or 250 K for tens to hundreds of millions of years, even when accounting for CO2 condensation. Over time, the added CO2 is lost to carbonates, the atmosphere collapses and returns to its buffered state. A substantial amount of water could be transported during the greenhouse periods from the surface of a frozen body of water created by outflow channel discharges to higher elevations, despite global temperatures well below freezing. This water, precipitated as snow, could ultimately form fluvial valleys if deposition sites are associated with localized heat sources, such as magmatic intrusions or volcanoes. Thus, if outflow channel discharges were accompanied by the release of sufficient quantities of CO2, a limited hydrological cycle could have resulted that would have been capable of producing geomorphic change sufficient for fluvial erosion and valley formation. Glacial or periglacial landforms would also be a consequence of such a mechanism. PMID:11541758

  18. 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.

  19. Sedimentological characterization of braided and meandering fluvial reservoirs: Prediction of size and heterogeneity

    SciTech Connect

    Davies, D.K. ); Vargas, J. )

    1993-02-01

    Fluvial reservoirs host significant volumes of hydrocarbons. They comprise a significant reserve base in areas and formations as diverse as the San Jorge Basin, Argentina, the Lagunillas Formation, Venezuela, and Cano Limon Field, Colombia. Effective development and reservoir management required detailed sedimentological characterization because fluvial reservoirs, irrespective of age and geographic location, are characterized by considerable variability in geometry and internal heterogeneity. This paper presents models of braided and meandering reservoirs in selected Tertiary and Cretaceous fields of South and North America, based on sedimentological characterization using conventional cores and wireline logs. Fieldwide (macro-scale) and inter-well (meso-scale) heterogeneity is determined through detailed evaluation of facies distribution, particularly the distribution and maturity of paleosol horizons (e.g. calcretes). Within a given reservoir, micro-scale variations in porosity, permeability and saturation are fundamentally related to depositional environment. Effective permeability to hydrocarbons varies with environment and bedding style. The size of meandering and braided channel reservoirs is predicted using empirical geological equations. Predicted dimensions are compared with the independent results of reservoir simulation analysis for the same sand bodies. Engineering and sedimentological predictions of reservoir size and heterogeneity are similar, particularly in reservoirs where median permeability to hydrocarbons is > 1 md. The size and heterogeneity of productive channel reservoirs can be predicted at an early stage in field development is channel style and channel depth are known. Determination of these two fundamental parameters required sedimentological characterization at the macro-, meso-, and micro-scale using wireline logs and cores.

  20. An inventory of published and unpublished fluvial-sediment data for California, 1956-70

    USGS Publications Warehouse

    Porterfield, George

    1972-01-01

    This inventory was prepared to provide a convenient reference to published and unpublished fluvial-sediment data for water years 1956-70, and updates substantially previous inventories. Sediment stations are listed in downstream order, and an alphabetical list of stations is also included. Figure 1 shows the approximate location of sediment stations in California. Most of the fluvial-sediment data in California were collected by the U.S. Geological Survey, under cooperative agreements with the following Federal, State, and local agencies: California Department of Water Resources, California Department of Navigation and Ocean Development, California Department of Fish and Game, Bolinas Harbor District, Monterey County Flood Control and Water Conservation District, Orange County Flood Control District, Riverside County Flood Control and Water Conservation District, San Diego County Department of Sanitation and Flood Control, San Luis Obispo County, San Mateo County, Santa Clara County Flood Control and Water District, Santa Cruz County Flood Control and Water Conservation District, Santa Cruz, city of, University of California, Ventura County Flood Control District, Forest Service, U.S. Department of Agriculture, Soil Conservation Service, U.S. Department of Agriculture, Corps of Engineers, U.S. Army, Bureau of Reclamation, U.S. Department of the Interior, National Park Service, U.S. Department of the Interior. This report was prepared by the Geological Survey under the general supervision of R. Stanley Lord, district chief in charge of water-resources investigations in California.

  1. Utilization of ancient permafrost carbon in headwaters of Arctic fluvial networks.

    PubMed

    Mann, Paul J; Eglinton, Timothy I; McIntyre, Cameron P; Zimov, Nikita; Davydova, Anna; Vonk, Jorien E; Holmes, Robert M; Spencer, Robert G M

    2015-01-01

    Northern high-latitude rivers are major conduits of carbon from land to coastal seas and the Arctic Ocean. Arctic warming is promoting terrestrial permafrost thaw and shifting hydrologic flowpaths, leading to fluvial mobilization of ancient carbon stores. Here we describe (14)C and (13)C characteristics of dissolved organic carbon from fluvial networks across the Kolyma River Basin (Siberia), and isotopic changes during bioincubation experiments. Microbial communities utilized ancient carbon (11,300 to >50,000 (14)C years) in permafrost thaw waters and millennial-aged carbon (up to 10,000 (14)C years) across headwater streams. Microbial demand was supported by progressively younger ((14)C-enriched) carbon downstream through the network, with predominantly modern carbon pools subsidizing microorganisms in large rivers and main-stem waters. Permafrost acts as a significant and preferentially degradable source of bioavailable carbon in Arctic freshwaters, which is likely to increase as permafrost thaw intensifies causing positive climate feedbacks in response to on-going climate change. PMID:26206473

  2. Automatic procedures for river reach delineation: Univariate and multivariate approaches in a fluvial context

    NASA Astrophysics Data System (ADS)

    Martínez-Fernández, V.; Solana-Gutiérrez, J.; González del Tánago, M.; García de Jalón, D.

    2016-01-01

    Segmenting the continuum of rivers into homogeneous reaches is an important issue in river research and management. Automatic procedures provide significance, objectivity, and repeatability. Although univariate techniques are frequently used to identify river reaches, multivariate approaches offer a more integrative context. Three nonparametric methods (multi-response permutation procedures (MRPP) with an advance in the significance level estimation, the Pettitt and Mann-Kendall tests) are applied for segmenting the river based on three geomorphic variables (valley width, active channel width, and channel slope) systematically measured in a GIS environment. The cited techniques have been applied to the Curueño River (NW Spain) to illustrate the methods, we analyse reach distribution along the river longitudinal profile. The methods successfully characterize the evident transitions along fluvial systems and also others less noticeable. The three methods provide more reaches according to valley width and less reaches according to channel slope (18.0 and 3.7 reaches on average, respectively). In contrast to the Mann-Kendall test, MRPP and Pettitt tests provide more stable segmentations when significance level varies. However, the Pettitt test provides irregular segmentations for regular patterns. The MRPP both univariate and multivariate applications enables a wider scope for the segmentation issue, which is useful in diverse aspects of fluvial domain.

  3. Interaction of marine and fluvial clastic sedimentation, central Italy, Tyrrhenian coast

    SciTech Connect

    Evangelista, S.; Full, W.E.; Tortora, P.

    1989-03-01

    An integrated approach was used to study the interaction of fluvial, beach, and marine processes on sedimentation at the west-central coast of Italy along the Tyrrhenian Sea. The study area, 120 km northwest of Rome, is bounded on the north by Mt. Argentario, on the east by Pleistocene volcanics, on the south by the St. Augustine River, and on the west by the 50-mn bathymetric isopleth. The primary tools used included field work, textural analysis, high-resolution marine seismic, SEM, and Fourier shape analysis. Field work revealed incised streams, potentially relict beach ridges and lagoons, and relatively steep nearshore marine slopes in the northern portions of the study area. The result of the shape analysis performed on 56 samples was the definition of four end members. Each end member reflects a sedimentation process. Three end members were directly associated with fluvial sedimentation, and the fourth reflected marine processes. The seismic data along with the SEM analysis strongly supported the interpretation of four processes that dominate the recent sedimentation history. The sand interpreted to be associated with marine processes was found to represent the smoothest end member. SEM analysis suggests that the smoothing is not due to abrasion but to plastering associated with biologic processes (digestion.) and/or with silica precipitation associated with clay alteration at the freshwater/saltwater interface.

  4. Environmental magnetism in fluvial and loessic Holocene sediments and paleosols from the Chacopampean plain (Argentina)

    NASA Astrophysics Data System (ADS)

    Orgeira, M. J.; Walther, A. M.; Tófalo, R. O.; Vásquez, C.; Berquó, T.; Favier Dobois, C.; Bohnel, H.

    2003-08-01

    The magnetic signals of fluvial and loessic sediments and paleosol sequences developed in the Chacopampean plain (Buenos Aires province, Argentina) are described and interpreted. To provide an analysis of the rock magnetism, sedimentological studies were performed, which led to a stratigraphic framework of so-called 'post-Pampean' sediments deposited in different paleoenvironments. The Luján formation, composed of fine sand and pelitic sediments, is fluvial and includes floodplain facies, whereas the La Postrera Formations is eolian but particularly loessic. Variations in the magnetic signals observed in paleosols in the units were ascribed to pedogenic processes that occurred at different stages of soil development. An extensive process of dissolution of detrital ferrimagnetic minerals was recognized. In one paleosol, dissolution was accompanied by the appearance of a superparamagnetic (SP) fraction, which may indicate that the loss is connected to subsequent formation of ferrimagnetic minerals in the same paleosol. Both processes did not act simultaneously. The abundant rainfall and absence of CO 3Ca in the parent material could be necessary conditions for a defensible scenario for SP genesis. In the loessic sediments (Tapalqué locality), dissolution could be associated with the genesis of a high coercive fraction. The presence of high coercivity minerals may indicate a climate with a distinctly dry season, though their lack does not necessarily imply the absence of a dry season.

  5. Hydraulics are a first-order control on CO2 efflux from fluvial systems

    NASA Astrophysics Data System (ADS)

    Long, Hazel; Vihermaa, Leena; Waldron, Susan; Hoey, Trevor; Quemin, Simon; Newton, Jason

    2015-10-01

    Evasion of carbon dioxide (CO2) from fluvial systems is now recognized as a significant component of the global carbon cycle. However, the magnitude of, and controls on, this flux remains uncertain, and improved understanding of both is required to refine global estimates of fluvial CO2 efflux. CO2 efflux data show no pattern with latitude suggesting that catchment biological productivity is not a primary control and that an alternative explanation for intersite variability is required. It has been suggested that increased flow velocity and turbulence enhance CO2 efflux, but this is not confirmed. Here using contemporaneous measurements of efflux (range: 0.07-107 µmol CO2 m-2 s-1), flow hydraulics (mean velocity range: 0.03-1.39 m s-1), and pCO2 (range: 174-10712 µatm) at six sites, we find that flow intensity is a primary control on efflux across two climatically different locations (where pH is not a limiting factor) and that the relationship is refined by incorporating the partial pressure of CO2 (pCO2) of the water. A remaining challenge is how to upscale from point to reach or river basin level. Remote imaging or river surface may be worth exploring if subjectivity in interpreting surface state can be overcome.

  6. Evidence of population resistance to extreme low flows in a fluvial-dependent fish species

    USGS Publications Warehouse

    Katz, Rachel A; Freeman, Mary C.

    2015-01-01

    Extreme low streamflows are natural disturbances to aquatic populations. Species in naturally intermittent streams display adaptations that enhance persistence during extreme events; however, the fate of populations in perennial streams during unprecedented low-flow periods is not well-understood. Biota requiring swift-flowing habitats may be especially vulnerable to flow reductions. We estimated the abundance and local survival of a native fluvial-dependent fish species (Etheostoma inscriptum) across 5 years encompassing historic low flows in a sixth-order southeastern USA perennial river. Based on capturemark-recapture data, the study shoal may have acted as a refuge during severe drought, with increased young-of-the-year (YOY) recruitment and occasionally high adult immigration. Contrary to expectations, summer and autumn survival rates (30 days) were not strongly depressed during low-flow periods, despite 25%-80% reductions in monthly discharge. Instead, YOY survival increased with lower minimum discharge and in response to small rain events that increased low-flow variability. Age-1+ fish showed the opposite pattern, with survival decreasing in response to increasing low-flow variability. Results from this population dynamics study of a small fish in a perennial river suggest that fluvial-dependent species can be resistant to extreme flow reductions through enhanced YOY recruitment and high survival

  7. Fluvial architecture of dinosaur bonebeds in the Cretaceous Judith River Formation, south-central Montana

    SciTech Connect

    Wilson, K.M. ); Dodson, P. ); Fiorillo, A.R. )

    1991-03-01

    Fluvial architecture of dinosaur bonebeds in the Cretaceous Judith River Formation, south-central Montana, has been the subject of intensive paleontological study for many years. However, little has been published on the sedimentology of the formation in this area. The authors have completed a preliminary field study of fluvial facies, with a view towards correcting this omission. Initial results include detailed facies descriptions and maps for five quarries along a line of transect stretching some 40 km parallel to depositional dip. Facies identified are predominantly overbank splays and levees, with common point bar/alluvial channel units and occasional small, possibly estuarine sand bodies in parts of the section. Shell beds (mainly oysters) and bedded, 1 m thick coals are also significant in some sections. Preliminary attempts at paleohydrology suggest river channels in some parts of the section were about 100 m wide and 2 m deep; however, other parts of the section exhibit much larger channel widths. Channel stacking is common. Preliminary results suggest a strong correlation between the occurrence of reddish brown carbonaceous silty shales, and dinosaur bone deposits.

  8. Floodplain forest succession reveals fluvial processes: A hydrogeomorphic model for temperate riparian woodlands.

    PubMed

    Egger, Gregory; Politti, Emilio; Lautsch, Erwin; Benjankar, Rohan; Gill, Karen M; Rood, Stewart B

    2015-09-15

    River valley floodplains are physically-dynamic environments where fluvial processes determine habitat gradients for riparian vegetation. These zones support trees and shrubs whose life stages are adapted to specific habitat types and consequently forest composition and successional stage reflect the underlying hydrogeomorphic processes and history. In this study we investigated woodland vegetation composition, successional stage and habitat properties, and compared these with physically-based indicators of hydraulic processes. We thus sought to develop a hydrogeomorphic model to evaluate riparian woodland condition based on the spatial mosaic of successional phases of the floodplain forest. The study investigated free-flowing and dam-impacted reaches of the Kootenai and Flathead Rivers, in Idaho and Montana, USA and British Columbia, Canada. The analyses revealed strong correspondence between vegetation assessments and metrics of fluvial processes indicating morphodynamics (erosion and shear stress), inundation and depth to groundwater. The results indicated that common successional stages generally occupied similar hydraulic environments along the different river segments. Comparison of the spatial patterns between the free-flowing and regulated reaches revealed greater deviation from the natural condition for the braided channel segment than for the meandering segment. This demonstrates the utility of the hydrogeomorphic approach and suggests that riparian woodlands along braided channels could have lower resilience than those along meandering channels and might be more vulnerable to influences such as from river damming or climate change. PMID:26160662

  9. Episodic Ocean-Induced CO2 Greenhouse on Mars: Implications for Fluvial Valley Formation

    NASA Technical Reports Server (NTRS)

    Gulick, V. C.; Tyler, D.; McKay, C. P.; Haberle, R. M.

    1997-01-01

    Pulses of CO2 injected into the martian atmosphere more recently than 4 Ga can place the atmosphere into a stable, higher pressure, warmer greenhouse state. One to two bar pulses of CO2 added to the atmosphere during the past several billion years are sufficient to raise global mean temperatures above 240 or 250 K for tens to hundreds of millions of years, even when accounting for CO2 condensation. Over time, the added CO2 is lost to carbonates, the atmosphere collapses and returns to its buffered state. A substantial amount of water could be transported during the greenhouse periods from the surface of a frozen body of water created by outflow channel discharges to higher elevations, despite global temperatures well below freezing. This water, precipitated as snow, could ultimately form fluvial valleys if deposition sites are associated with localized heat sources, such as magmatic intrusions or volcanoes. Thus, if outflow channel discharges were accompanied by the release of sufficient quantities of CO2, a limited hydrological cycle could have resulted that would have been capable of producing geomorphic change sufficient for fluvial erosion and valley formation. Glacial or periglacial landforms would also be a consequence of such a mechanism.

  10. Influence of small-scale fluvial architecture on CO2 trapping processes in deep brine reservoirs

    NASA Astrophysics Data System (ADS)

    Gershenzon, Naum I.; Ritzi, Robert W.; Dominic, David F.; Soltanian, Mohamadreza; Mehnert, Edward; Okwen, Roland T.

    2015-10-01

    A number of important candidate CO2 reservoirs exhibit sedimentary architecture reflecting fluvial deposition. Recent studies have led to new conceptual and quantitative models for sedimentary architecture in fluvial deposits over a range of scales that are relevant to CO2 injection and storage. We used a geocellular modeling approach to represent this multiscaled and hierarchical sedimentary architecture. With this model, we investigated the dynamics of CO2 plumes, during and after injection, in such reservoirs. The physical mechanism of CO2 trapping by capillary trapping incorporates a number of related processes, i.e., residual trapping, trapping due to hysteresis of the relative permeability, and trapping due to hysteresis of the capillary pressure. Additionally, CO2 may be trapped due to differences in capillary entry pressure for different textural sedimentary facies (e.g., coarser-grained versus finer-grained cross sets). The amount of CO2 trapped by these processes depends upon a complex system of nonlinear and hysteretic characteristic relationships including how relative permeability and capillary pressure vary with brine and CO2 saturation. The results strongly suggest that representing small-scale features (decimeter to meter), including their organization within a hierarchy of larger-scale features, and representing their differences in characteristic relationships can all be critical to understanding trapping processes in some important candidate CO2 reservoirs.

  11. Utilization of ancient permafrost carbon in headwaters of Arctic fluvial networks

    PubMed Central

    Mann, Paul J.; Eglinton, Timothy I.; McIntyre, Cameron P.; Zimov, Nikita; Davydova, Anna; Vonk, Jorien E.; Holmes, Robert M.; Spencer, Robert G. M.

    2015-01-01

    Northern high-latitude rivers are major conduits of carbon from land to coastal seas and the Arctic Ocean. Arctic warming is promoting terrestrial permafrost thaw and shifting hydrologic flowpaths, leading to fluvial mobilization of ancient carbon stores. Here we describe 14C and 13C characteristics of dissolved organic carbon from fluvial networks across the Kolyma River Basin (Siberia), and isotopic changes during bioincubation experiments. Microbial communities utilized ancient carbon (11,300 to >50,000 14C years) in permafrost thaw waters and millennial-aged carbon (up to 10,000 14C years) across headwater streams. Microbial demand was supported by progressively younger (14C-enriched) carbon downstream through the network, with predominantly modern carbon pools subsidizing microorganisms in large rivers and main-stem waters. Permafrost acts as a significant and preferentially degradable source of bioavailable carbon in Arctic freshwaters, which is likely to increase as permafrost thaw intensifies causing positive climate feedbacks in response to on-going climate change. PMID:26206473

  12. Fluvial and Lacustrine Processes in Meridiani Planum and the Origin of the Hematite by Aqueous Alteration

    NASA Technical Reports Server (NTRS)

    Newsom, H. E.; Barber, C. A.; Schelble, R. T.; Hare, T. M.; Feldman, W. C.; Sutherland, V.; Livingston, A.; Lewis, K.

    2003-01-01

    The prime MER landing site in Meridiani Planum is located on layered materials, including hematite, whose origin as lacustrine or aeolian sediments, or volcanic materials is uncertain. Our detailed mapping of the region provides important constraints on the history of the region. Our mapping of the location of fluvial and lacustrine land forms in the region relative to the layered deposits provides new evidence of a long history of erosion and deposition as has long been noted . In addition, our detailed mapping of the southern boundary of the hematite deposit strongly supports an association between longlived fluvial channels and lacustrine basins and the strongest hematite signatures. This evidence supports an origin of the hematite deposits by interaction with water under ambient conditions in contrast to suggestions of hydrothermal processes due to volcanic or impact crater processes. An important part of the story is the evidence for the localization of the layered deposits due to topographic control induce by the presence of a large early basin we have identified that extends to the north-east of the landing site. Distribution of current channel networks, drainages,

  13. Depositional controls on tidally influenced fluvial successions, Neslen Formation, Utah, USA

    NASA Astrophysics Data System (ADS)

    Shiers, M. N.; Mountney, N. P.; Hodgson, D. M.; Cobain, S. L.

    2014-08-01

    The stratigraphic architecture of marginal marine successions records the interplay of autogenic and allogenic processes, and discerning their relative role in governing the morphology of the palaeoenvironment and the architecture of the preserved sedimentary succession is not straightforward. The Campanian Neslen Formation, Mesaverde Group, Utah, is a tidally influenced fluvial succession sourced from the Sevier Orogen, which prograded eastwards into the Western Interior Seaway. Detailed mapping in three dimensions of architectural relationships between sandstone bodies has enabled documentation of lateral and vertical changes in the style of channel-body stacking and analysis of the distribution of sedimentary evidence for tidal influence. Upwards, through the succession, sandstone channel bodies become larger and more amalgamated. Laterally, the dominant style of channel bodies changes such that ribbon channel-fills are restricted to the east of the study area whereas lateral accretion deposits dominate to the west. Combined allogenic and autogenic controls gave rise to the observed stratigraphy. A temporal decrease in the rate of accommodation generation resulted in an upward increase in amalgamation of sand-bodies. Autogenic processes likely played a significant role in moderating the preserved succession: up-succession changes in the style of stacking of channelized bodies could have arisen either from progradation of a distributive fluvial system or from an upstream nodal avulsion of a major trunk channel; accumulation of tide influenced, wave dominated units likely record episodes of delta-lobe abandonment, subsidence and submergence to allow accumulation of near shore sand bars with associated washover complexes.

  14. Archaeological horizons and fluvial processes at the Lower Paleolithic open-air site of Revadim (Israel).

    PubMed

    Marder, Ofer; Malinsky-Buller, Ariel; Shahack-Gross, Ruth; Ackermann, Oren; Ayalon, Avner; Bar-Matthews, Miryam; Goldsmith, Yonaton; Inbar, Moshe; Rabinovich, Rivka; Hovers, Erella

    2011-04-01

    In this paper we present new data pertaining to the paleo-landscape characteristics at the Acheulian site of Revadim, on the southern coastal plain of Israel. Sedimentological, isotopic, granulometric and micromorphological studies showed that the archaeological remains accumulated in an active fluvial environment where channel action, overbank flooding and episodic inundation occurred. Measurements of total organic matter and its carbon isotopic composition indicate that the hominin activity at the site started at a period of relatively drier conditions, which coincided with erosion of the preceding soil sequence. This process led to the formation of a gently-undulating topography, as reconstructed by a GIS model. Later deposition documents relatively wetter conditions, as indicated by carbon isotopic composition. Formation processes identified at the site include fluvial processes, inundation episodes that resulted in anaerobic conditions and formation of oxide nodules, as well as small-scale bioturbation and later infiltration of carbonate-rich solutions that resulted in the formation of calcite nodules and crusts. The combination of micro-habitats created favorable conditions that repeatedly drew hominins to the area, as seen by a series of super-imposed archaeological horizons. This study shows that site-specific paleo-landscape reconstructions should play an important role in understanding regional variation among hominin occupations and in extrapolating long-term behavioral patterns during the Middle Pleistocene. PMID:20304463

  15. Hydrological and sedimentary controls over fluvial thermal erosion, the Lena River, central Yakutia

    NASA Astrophysics Data System (ADS)

    Tananaev, Nikita I.

    2016-01-01

    Water regime and sedimentary features of the middle Lena River reach near Yakutsk, central Yakutia, were studied to assess their control over fluvial thermal erosion. The Lena River floodplain in the studied reach has complex structure and embodies multiple levels varying in height and origin. Two key sites, corresponding to high and medium floodplain levels, were surveyed in 2008 to describe major sedimentary units and properties of bank material. Three units are present in both profiles, corresponding to topsoil, overbank (cohesive), and channel fill (noncohesive) deposits. Thermoerosional activity is mostly confined to a basal layer of frozen channel fill deposits and in general occurs within a certain water level interval. Magnitude-frequency analysis of water level data from Tabaga gauging station shows that a single interval can be deemed responsible for the initiation of thermal action and development of thermoerosional notches. This interval corresponds to the discharges between 21,000 and 31,000 m3 s- 1, observed normally during spring meltwater peak and summer floods. Competence of fluvial thermal erosion depends on the height of floodplain level being eroded, as it acts preferentially in high floodplain banks. In medium floodplain banks, thermal erosion during spring flood is constrained by insufficient bank height, and erosion is essentially mechanical during summer flood season. Bank retreat rate is argued to be positively linked with bank height under periglacial conditions.

  16. Magmatic Intrusions and a Hydrothermal Origin for Fluvial Valleys on Mars

    NASA Technical Reports Server (NTRS)

    Gulick, Virginia C

    1998-01-01

    Numerical models of Martian hydrothermal systems demonstrate that systems associated with magmatic intrusions greater than several hundred cubic kilometers can provide sufficient groundwater outflow to form the observed fluvial valleys, if subsurface permeability exceeds about 1.0 darcy. Groundwater outflow increases with increasing intrusion volume and subsurface permeability and is relatively insensitive to intrusion depth and subsurface porosity within the range considered here. Hydrothermally-derived fluids can melt through 1 to 2 km thick ice-rich permafrost layers in several thousand years. Hydrothermal systems thus provide a viable alternative to rainfall for providing surface water for valley formation. This mechanism can form fluvial valleys not only during the postulated early warm, wet climatic epoch, but also during more recent epochs when atmospheric conditions did not favor atmospheric cycling of water. The clustered distribution of the valley networks on a given geologic surface or terrain unit of Mars may also be more compatible with localized, hydrothermally-driven groundwater outflow than regional rainfall. Hydrothermal centers on Mars may have provided appropriate environments for the initiation of life or final oases for the long-term persistence of life.

  17. Fluvial and marine controls on combined subaerial and subaqueous delta progradation: Morphodynamic modeling of compound-clinoform development

    NASA Astrophysics Data System (ADS)

    Swenson, John B.; Paola, Chris; Pratson, Lincoln; Voller, Vaughan R.; Murray, A. Brad

    2005-06-01

    Fluviodeltaic systems commonly display a compound-clinoform geometry that consists of a subaerial/subaqueous delta couplet. The extent of subaqueous delta development varies significantly and, in modern systems, is a function of fluvial input and basin hydrodynamics. We present a model of fluviodeltaic progradation in which the repeated occurrence of characteristic terrestrial floods and large coastal storms drives fluvial and shallow marine morphodynamics, respectively. We couple fluvial and shallow marine sediment dynamics via the surf zone, which we collapse to a shock condition and treat as a moving boundary. With steady sediment supply and sea level and simple basin geometry, our model naturally develops prograding deltas with compound-clinoform geometries. The subaerial delta grows via fluvial aggradation and shoreface progradation, whereas the subaqueous delta expands through foreset progradation, with only minor topset aggradation. The interplay of fluvial input with the wave/current field controls the basic partitioning of sediment between subaerial and subaqueous deltas and, by extension, the compound-clinoform geometry. Increasing the frequency or magnitude of coastal storms, decreasing flood frequency or discharge, and reducing grain size all increase the fraction of sediment delivered to the shallow marine environment and the extent of subaqueous delta progradation relative to subaerial delta development. Our model, which emphasizes the intrinsic coupling of fluvial and shallow marine sediment dynamics and downplays the importance of allogenic fluctuations, can explain many of the first-order morphologic features of natural delta systems, including significant lateral separation of the shoreline and clinoform rollover and differing rates of subaerial and subaqueous delta progradation.

  18. Fluvial-aeolian interactions in sediment routing and sedimentary signal buffering: an example from the Indus Basin and Thar Desert

    USGS Publications Warehouse

    East, Amy E.; Clift, Peter D.; Carter, Andrew; Alizai, Anwar; VanLaningham, Sam

    2015-01-01

    Sediment production and its subsequent preservation in the marine stratigraphic record offshore of large rivers are linked by complex sediment-transfer systems. To interpret the stratigraphic record it is critical to understand how environmental signals transfer from sedimentary source regions to depositional sinks, and in particular to understand the role of buffering in obscuring climatic or tectonic signals. In dryland regions, signal buffering can include sediment cycling through linked fluvial and eolian systems. We investigate sediment-routing connectivity between the Indus River and the Thar Desert, where fluvial and eolian systems exchanged sediment over large spatial scales (hundreds of kilometers). Summer monsoon winds recycle sediment from the lower Indus River and delta northeastward, i.e., downwind and upstream, into the desert. Far-field eolian recycling of Indus sediment is important enough to control sediment provenance at the downwind end of the desert substantially, although the proportion of Indus sediment of various ages varies regionally within the desert; dune sands in the northwestern Thar Desert resemble the Late Holocene–Recent Indus delta, requiring short transport and reworking times. On smaller spatial scales (1–10 m) along fluvial channels in the northern Thar Desert, there is also stratigraphic evidence of fluvial and eolian sediment reworking from local rivers. In terms of sediment volume, we estimate that the Thar Desert could be a more substantial sedimentary store than all other known buffer regions in the Indus basin combined. Thus, since the mid-Holocene, when the desert expanded as the summer monsoon rainfall decreased, fluvial-eolian recycling has been an important but little recognized process buffering sediment flux to the ocean. Similar fluvial-eolian connectivity likely also affects sediment routing and signal transfer in other dryland regions globally.

  19. Fluvial dissection, isostatic uplift, and geomorphological evolution of volcanic islands (Gran Canaria, Canary Islands, Spain)

    NASA Astrophysics Data System (ADS)

    Menéndez, Inmaculada; Silva, Pablo G.; Martín-Betancor, Moises; Pérez-Torrado, Francisco José; Guillou, Hervé; Scaillet, S.

    2008-11-01

    Digital analysis of torrential gullies ('barrancos') deeply incised into the volcanic Island of Gran Canaria (Canary Islands) allows us to extract the longitudinal profiles and pre-incision surfaces for individual basins, from which morphometric parameters (length, elevation, area, slope) have been calculated. Other derived parameters, such as ridgeline profiles, maximum incision values, volume removed by fluvial erosion, geophysical relief and isostatic uplift, have also been computed. Based on K/Ar ages for the island, well-constrained incision-uplift rates have been calculated by means of the combination of different methodological approaches commonly used in orogens and large mountain ranges. The geomorphological and morphometric analyses reveal that the island is clearly divided into four environmental quadrants determined by the combination of a couple of key-factors: the age of the volcanic surfaces and the climatic conditions. These factors determine a young sector covered with Plio-Quaternary platform-forming lavas (finished at 1.9-1.5 Ma) evolving under contrasting wet (NE) to dry (SE) climates, and an older sector, conserving the residual surfaces of the Miocene shield building (14.5-8.7 Ma) at the ridgelines, also subjected to wet (NW) and dry (SW) climates. Incision is related to the age zonation of the island. Maximum incisions (< 1200 m) are logically recorded in the older SW sector of the island, but incision rates are directly related to the climatic zonation, with maximum mean values in the wet Northern quadrants (0.18-0.12 mm/yr). The evaluation of the material removed by fluvial erosion for individual basins allows us to assess the consequent theoretical isostatic response in the different sectors of the island. The obtained uplift rates indicate that water availability (by drainage area and elevation) is a relevant controlling factor: the records from the wet Northern sectors show uplift values of between 0.09 and 0.03 mm/yr, whereas in the drier Southern sectors, the maximum values are under 0.015 mm/yr. Mean uplift rates obtained in this study are within the range of those inferred from stratigraphical markers, as is the case for horizons of raised Pliocene pillow-lavas (c.a. 4 Ma) uplifted between 46 and 143 m (0.014-0.024 mm/yr). The estimation of the bulk uplift promoted by fluvial unloading is of + 143 m for the entire island, and of + 71 m for the wet NE sector. These data explain 73% to 99% of the maximum uplift recorded by the raised Pliocene sea-level markers. This reflects that erosional unloading is a critical control factor in the uplift of the oceanic island, but is not capable of explaining the full recorded uplift in Gran Canaria. Additional sources of uplift, such as gravitational unloading, lithospheric flexure induced by adjacent islands, and/or volcanic underplating, are required. The theoretical onset of lithospheric bulging beneath Gran Canaria, as exerted by Tenerife, promoted a broad westwards tilting of the former from 3.8-3.5 Ma ago. This overall tilting accelerated fluvial incision, erosional unloading, and, therefore, the sustained differential uplift on the Eastern slope of the island over its last erosional stage. Considering mean uplift rates for the East and West sectors, Eastern values (0.024 mm/yr) are double than those in the West (0.011 mm/yr), supporting the role of lithospheric flexure of adjacent islands as an additional source of uplift. Complex feedback between fluvial unloading, differential uplift, orographic effect, lithospheric flexure, and volcanic underplating, seems to control the geomorphological development of hot-spot volcanic islands, after the gravitational collapse of stratovolcanos during their rejuvenation stage.

  20. Modern Landform Distribution of the Gilbert River Distributive Fluvial System (DFS) and Predictions Regarding Ancient Coastal Plain Progradational Successions

    NASA Astrophysics Data System (ADS)

    McNamara, K. C.; Weissmann, G. S.; Scuderi, L. A.; Owen, A.; Nichols, G. J.; Hartley, A. J.

    2011-12-01

    Distributive fluvial systems (DFSs) are modern fluvial deposits of radial distributive channel patterns and encompass a continuum from small-scale alluvial fans to large-scale fluvial megafans. Given that DFSs have been shown to comprise most continental regimes, we hypothesize that these systems form fluvial deposits in sedimentary basins at the fluvial-marine interface. Few modern examples of DFSs spanning this realm exist, as modern coastlines are presently flooded due to high-amplitude Quaternary sea level changes. The Gilbert River DFS of north Queensland, Australia, represents a modern example of a DFS terminating in the Gulf of Carpentaria. Remote sensing analyses on this system show the same recognizable depositional patterns as purely continental DFS: 1) a radial channel pattern originating from an apex, 2) a down-DFS decrease in both channel and grain size, 3) a lack of lateral channel confinement, 4) a broad fan shape, and 5) a down-DFS increase in floodplain/channel area ratio. The distal portion (influenced by sea level changes) exhibits: a) a sharp contact between DFS and marginal-marine deposits, b) channel incision, confinement and lateral movement, c) channel width increasing due to tidal influence, d) sediment redistribution (spits, small-scale deltas), and e) shoreline progradation (wave-cut platforms and beach ridges). These observations ultimately lead to sedimentologic and stratigraphic predictions regarding coastal DFS deposits in the geologic record. Data from the Gilbert system are compared with facies and facies transitions in Cordilleran foreland basin Cretaceous strata that cross the fluvial-marine interface, such as the John Henry Mbr. of the Straight Cliffs Formation and the Williams Fork Formations of Utah and Colorado, respectively. If these strata are DFS, then the following succession (in ascending order) should exist in a single progradational succession: 1) Distal channel deposits with evidence of tidal influence (herringbone cross-stratification, brackish fossils, inclined heterolithic stratification) that cut into underlying foreshore strata and laterally equivalent fine-grained strata, overlain by 2) medial deposits of coarsening-upward packages due to avulsion and well-developed, laterally extensive mature paleosols, topped by 3) proximal deposits consisting of amalgamated sandstone bodies separated by regionally discontinuous erosional surfaces and relatively rare, well-drained, immature paleosols. Thus, progradational successions should exhibit an upsection increase in grain size, sand:mud ratios, and channel downcutting. Coastal plain fluvial and marginal marine progradational successions have proven to be important hydrocarbon and carbon dioxide sequestration reservoirs, coal accumulations, and aquifers. However, existing fluvial facies models used to predict sandbody distribution and connectivity are typically based on aggradational valley fill successions at the outcrop- and borehole-scale.

  1. 25 CFR 115.106 - Assets of members of the Agua Caliente Band of Mission Indians.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 25 Indians 1 2013-04-01 2013-04-01 false Assets of members of the Agua Caliente Band of Mission Indians. 115.106 Section 115.106 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR FINANCIAL ACTIVITIES TRUST FUNDS FOR TRIBES AND INDIVIDUAL INDIANS IIM Accounts § 115.106 Assets of members of the...

  2. 25 CFR 115.106 - Assets of members of the Agua Caliente Band of Mission Indians.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 25 Indians 1 2012-04-01 2011-04-01 true Assets of members of the Agua Caliente Band of Mission Indians. 115.106 Section 115.106 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR FINANCIAL ACTIVITIES TRUST FUNDS FOR TRIBES AND INDIVIDUAL INDIANS IIM Accounts § 115.106 Assets of members of the...

  3. 25 CFR 115.106 - Assets of members of the Agua Caliente Band of Mission Indians.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Assets of members of the Agua Caliente Band of Mission Indians. 115.106 Section 115.106 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR FINANCIAL ACTIVITIES TRUST FUNDS FOR TRIBES AND INDIVIDUAL INDIANS IIM Accounts § 115.106 Assets of members of the...

  4. Geologie study off gravels of the Agua Fria River, Phoenix, AZ

    USGS Publications Warehouse

    Langer, W.H.; Dewitt, E.; Adams, D.T.; O'Briens, T.

    2010-01-01

    The annual consumption of sand and gravel aggregate in 2006 in the Phoenix, AZ metropolitan area was about 76 Mt (84 million st) (USGS, 2009), or about 18 t (20 st) per capita. Quaternary alluvial deposits in the modern stream channel of the Agua Fria River west of Phoenix are mined and processed to provide some of this aggregate to the greater Phoenix area. The Agua Fria drainage basin (Fig. 1) is characterized by rugged mountains with high elevations and steep stream gradients in the north, and by broad alluvial filled basins separated by elongated faultblock mountain ranges in the south. The Agua Fria River, the basin’s main drainage, flows south from Prescott, AZ and west of Phoenix to the Gila River. The Waddel Dam impounds Lake Pleasant and greatly limits the flow of the Agua Fria River south of the lake. The southern portion of the watershed, south of Lake Pleasant, opens out into a broad valley where the river flows through urban and agricultural lands to its confluence with the Gila River, a tributary of the Colorado River.

  5. 25 CFR 115.106 - Assets of members of the Agua Caliente Band of Mission Indians.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 25 Indians 1 2011-04-01 2011-04-01 false Assets of members of the Agua Caliente Band of Mission Indians. 115.106 Section 115.106 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR FINANCIAL ACTIVITIES TRUST FUNDS FOR TRIBES AND INDIVIDUAL INDIANS IIM Accounts § 115.106 Assets of members of the...

  6. The Crucial Role of Particulate Matter in Fluvial Degradation of Thaw-Released Arctic Carbon

    NASA Astrophysics Data System (ADS)

    Vonk, J.; Sobczak, W. V.; Mann, P. J.; Bulygina, E. B.; Zimov, S. A.; Holmes, R. M.

    2010-12-01

    Half of the global pool of soil organic carbon (OC) is stored in Arctic permafrost. Thaw-release of this pool, triggered by ongoing climate warming, will mobilize old OC into streams and rivers that actively process this material. Studies suggest that thawing permafrost will mostly manifest itself in the amounts of particulate OC (POC), and is expected to increase POC fluxes. While the fluvial loads of terrestrial POC might be an order of magnitude lower than the dissolved fraction DOC, the degradation rate for POC appears to be much higher. Consequently, the resulting flux of outgassed CO2 might be of similar magnitude. This essential difference between POC and DOC has shown to be valid for Russian Arctic coastal waters, but has not yet been quantified in the Arctic watersheds that drain the most climate-sensitive regions on our planet. In July 2010, a team of scientists and students as part of the Polaris Project (http://www.thepolarisproject.org) travelled to the Northeast Science station in Cherskii in the Kolyma delta, Eastern Siberia. One goal was to improve our understanding on the degradation fluxes of fluvial POC and the differences among different (sub-)watersheds. We sampled the Kolyma River along with a wide range of tributaries draining watersheds of different size, topography, vegetation and permafrost coverage. Biological oxygen demand (BOD) was measured on filtered (0.7 um) and unfiltered water samples. Additionally, an incubation experiment was set-up with resuspended particulate matter from different tributaries and Kolyma springflood material throughout late May/early June. Hereby we excluded the DOC fraction and gained degradation information on POC. Preliminary results of the BOD experiment show mineralization rates that are far higher in the unfiltered bottles than the increase one would expect solely based on the difference in OC concentrations. This implies that fluvial POC is far more reactive than the dissolved fraction. Furthermore, it is likely that particle-associated bacteria consume DOC. We will present further results on POC versus DOC degradation rates and their spatial and temporal differences.

  7. Late Quaternary fluvial incision rates in a marine terraced landscape, southeastern Crete, Greece

    NASA Astrophysics Data System (ADS)

    Karymbalis, Efthimios; Papanastassiou, Dimitris; Valkanou, Kanella; Gaki-Papanastassiou, Kalliopi

    2014-05-01

    Along the southern coast of the island of Crete, a series of five east-west oriented Late Pleistocene marine terraces exist, demonstrating the significant coastal uplift of this area. These terraces, ranging in elevation from 10 to 160m, are deformed by the vertical movements of the NNE-SSW trending and dipping west normal fault of Ierapetra. This study focuses on defining rates of fluvial incision for the last 410 Ka along valley systems that drain the tectonically uplifting area of Ierapetra, south Crete. The studied streams have a N-S flow direction and discharge into the Libyan Sea. Some of them are developed on the uplifted block of the Ierapetra normal fault whereas others drain the subsiding area west of the fault. The lower reaches of the study streams cut down through these marine terraces, which have been recognized, mapped in detail and correlated with Late Pleistocene Oxygen-Isotope Stages of high sea-level stands following the global sea-level fluctuations. These terraces of known age were used as reference surfaces in order to determine fluvial incision rates as the lower reaches of the streams cut down through these platforms. To evaluate incision rates, thirty five topographic valley cross-sections were drawn through fieldwork measurements as well as using a digital elevation model (DEM) produced by detailed topographic diagrams at the scale of 1:5,000. Cross valley profiles were constructed at specific locations where streams cut down the inner edges of the marine terraces because these points correspond precisely to the age of the palaeo-shoreline during the interglacial stage. For each cross-section the ratio of valley floor width to valley height (Vf) and long-term mean stream incision rates were estimated for the last 410 Ka. The geomorphic evolution of the valleys has been mainly affected by the lithology of the bedrock, sea level fluctuations during the late Quaternary, the head-ward erosion and incision of the channels, as well as both the regional uplift and the uplift due to the activity of the Ierapetra fault. Fluvial incision rates are higher for the streams developed at the footwall depending strongly on the distance from the trace of the fault. Downcutting rates are comparable with the slip rate of the Ierapetra fault over the last 410 Ka.

  8. Tidal Simulations of an Incised-Valley Fluvial System with a Physics-Based Geologic Model

    NASA Astrophysics Data System (ADS)

    Ghayour, K.; Sun, T.

    2012-12-01

    Physics-based geologic modeling approaches use fluid flow in conjunction with sediment transport and deposition models to devise evolutionary geologic models that focus on underlying physical processes and attempt to resolve them at pertinent spatial and temporal scales. Physics-based models are particularly useful when the evolution of a depositional system is driven by the interplay of autogenic processes and their response to allogenic controls. This interplay can potentially create complex reservoir architectures with high permeability sedimentary bodies bounded by a hierarchy of shales that can effectively impede flow in the subsurface. The complex stratigraphy of tide-influenced fluvial systems is an example of such co-existing and interacting environments of deposition. The focus of this talk is a novel formulation of boundary conditions for hydrodynamics-driven models of sedimentary systems. In tidal simulations, a time-accurate boundary treatment is essential for proper imposition of tidal forcing and fluvial inlet conditions where the flow may be reversed at times within a tidal cycle. As such, the boundary treatment at the inlet has to accommodate for a smooth transition from inflow to outflow and vice-versa without creating numerical artifacts. Our numerical experimentations showed that boundary condition treatments based on a local (frozen) one-dimensional approach along the boundary normal which does not account for the variation of flow quantities in the tangential direction often lead to unsatisfactory results corrupted by numerical artifacts. In this talk, we propose a new boundary treatment that retains all spatial and temporal terms in the model and as such is capable to account for nonlinearities and sharp variations of model variables near boundaries. The proposed approach borrows heavily from the idea set forth by J. Sesterhenn1 for compressible Navier-Stokes equations. The methodology is successfully applied to a tide-influenced incised valley fluvial system and the resulting stratigraphy is shown and discussed for different tide amplitudes. 1 Sesterhenn, J.: "A characteristic-type formulation of the Navier-Stokes equations for high-order upwind schemes", Computers & Fluids 30 (1) 37-67, 2001.;

  9. Rock strength along a fluvial transect of the Colorado Plateau - quantifying a fundamental control on geomorphology

    NASA Astrophysics Data System (ADS)

    Bursztyn, N.; Pederson, J. L.; Tressler, C.; Mackley, R. D.; Mitchell, K. J.

    2015-11-01

    Bedrock strength is a key parameter that influences slope stability, landscape erosion, and fluvial incision. Yet, it is often ignored or indirectly constrained in studies of landscape evolution, as with the K erodibility parameter in stream-power models. Empirical datasets of rock strength suited to address geomorphic questions are rare, in part because of the difficulty in measuring those rocks at Earth's surface that are heterolithic, weak, or poorly exposed. Here we present a large dataset of measured bedrock strength organized by rock units exposed along the length of the trunk Green-Colorado River through the iconic Colorado Plateau of the western U.S. Measurements include field compressive tests, fracture spacing, and Selby Rock Mass Strength at 168 localities, as well as 672 individual tensile-strength tests in the laboratory. Tensile strength results are compared to geomorphic metrics of unit stream power, river gradient, and channel and valley-bottom width through the arid Colorado Plateau, where the influence of bedrock is intuitive but unquantified. Our dataset reveals logical trends between tensile and compressive strength as well as between strength, rock type and age. In bedrock reaches of the fluvial transect, there is a positive rank-correlation and a strong power-law correlation between reach-averaged rock strength and unit stream power, as well as a linear relation between tensile strength and river gradient. Expected relations between fracture spacing and topography are masked partly by the massive yet weak sandstones in the dataset. To constrain values for weak rock types such as shale, we utilize the inverse power-law scaling between tensile strength and valley-bottom width to estimate their "effective" tensile strength. Results suggest that tensile strength varies to at least an order-of-magnitude smaller values than evident with directly testable rocks in this landscape, and values for erodibility (K) in numerical simulations may be informed by this dataset. In terms of landscape evolution, these results support the finding that equilibrium adjustment to bedrock strength, not differential uplift or transient incision, is the first-order control on large-scale fluvial geomorphology in the Colorado Plateau. This has broad implications for the interpretation of topography in terms of tectonic drivers.

  10. How the eastern Qilian Shan Mountain was deformed, revealed by deformed fluvial terraces

    NASA Astrophysics Data System (ADS)

    Hu, X.; Pan, B.; Gao, H.; Hu, Z.; Geng, H.; Cao, B.

    2012-12-01

    The northwest-southeastern treading Qilian Shan Mountain, margining the northeastern Tibetan Plateau, has been uplifting and deforming related to thrust faults bordering the mountain range in the north. By now, the fault thrust rate and how the mountain was uplifted and deformed is poorly documented along the eastern Qilian Shan. In this study, several flights of late Quaternary fluvial terraces along two rivers (Xiying River and Jinta River), sourced from the mountain crest and flowing transecting these thrust faults and folds, are surveyed by differential GPS with the accuracy of lower than 10 centimeters. Meanwhile, the abandonment times of terrace surfaces were dated by OSL dating on the overlying loess above the fluvial deposits. Analysis results of height data show that fluvial terrace surfaces were obviously deformed related to thrusting and folding. At first, we derive an average uplift rate of 0.05~0.2 mm/yr, which is contributed by folding along the low-mountain range since 120 ka B.P. When the uplift contributed by thrust is added, the total rate of uplift would be 0.45-0.60 mm/yr. The second, by the geometry of terrace surface height, the thrust geometry under the surface is deduced. Along the low-mountain range (with elevation from 2000 m to 3000 m), the dip angle of thrust is bended from ~30° to ~50° at the depth of around 15 km, and at the depth of ~20 km, the thrust dip angle is changed to ~26°. Along the Huangcheng-Taerzhuang Fault, which bordering the high-mountain range (with elevation from 3000 m to 5000 m) and the low-mountain range, the dip angle is bended from ~70° at the surface to ~47° below the depth of ~5 km, and at the depth below 23 km, the dip angel of the thrust is >30°. We conclude that in the late Quaternary, the deforming of mountain range along the eastern Qilian Shan is accomplished both by thrusting and folding; the different uplift rate is mainly caused by different thrust angle in the depth along the eastern Qilian Shan Mountain.

  11. Developing an Understanding of Vegetation Change and Fluvial Carbon Fluxes in Semi-Arid Environments

    NASA Astrophysics Data System (ADS)

    Puttock, A.; Brazier, R. E.; Dungait, J. A. J.; Bol, R.; Macleod, C. J. A.

    2012-04-01

    Dryland environments are estimated to cover around 40% of the global land surface (Okin et al, 2009) and are home to approximately 2.5 billion people (Reynolds et al. 2007). Many of these areas have recently experienced extensive land degradation. One such area and the focus of this project is the semi-arid US Southwest, where degradation over the past 150 years has been characterised by the invasion of woody vegetation into grasslands. Transition from grass to woody vegetation results in a change in ecosystem structure and function (Turnbull et al, 2008). Structural change is typically characterised by an increased heterogeneity of soil and vegetation resources, associated with reduced vegetation coverage and an increased vulnerability to soil erosion and the potential loss of key nutrients to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is sequestered by these environments and the amount of carbon that is lost as the land becomes more degraded. Therefore, understanding these vegetation transitions is significant for sustainable land use and global biogeochemical cycling. This project uses an ecohydrological approach, monitoring natural rainfall-runoff events over six bounded plots with different vegetation coverage. The experiment takes advantage of a natural abundance stable 13C isotope shift from C3 piñon-juniper (Pinus edulis-Juniperus monosperma) mixed stand through a C4 pure-grass (Bouteloua eriopoda) to C3 shrub (Larrea tridentata). Data collected quantify fluvial fluxes of sediment and associated soil organic matter and carbon that is lost from across the grass-to-shrub and grass-to-woodland transition (where change in space is taken to indicate a similar change through time). Results collected during the 2010 and 2011 monsoon seasons will be presented, illustrating that soil and carbon losses are greater as the ecosystem becomes more dominated by woody plants. Additionally this project utilises novel biogeochemical techniques, using stable 13C isotope and lipid biomarker analyses, to trace and partition fluvial soil organic matter and carbon fluxes during these events. Results show that biomarkers specific to individual plant species can be used to define the provenance of carbon, quantifying whether more piñon or juniper derived carbon is mobilised from the upland plots, or whether more Larrea tridentata carbon is lost when compared to Bouteloa eripoda losses in the lowlands. The combined approach of monitoring carbon fluxes and tracing types of carbon shows great promise for improved understanding of carbon dynamics in areas subject to rapid vegetation change.

  12. Vegetation change in dryland environments: understanding changes in fluvial fluxes via changes in hydrological connectivity

    NASA Astrophysics Data System (ADS)

    Puttock, A.; Brazier, R. E.; Dungait, J. A. J.; Bol, R.; Macleod, C. J. A.

    2012-04-01

    Dryland environments are estimated to cover around 40% of the global land surface (Okin et al, 2009) and are home to approximately 2.5 billion people (Reynolds et al. 2007). Many of these areas have recently experienced extensive land degradation. One such area and the focus of this project is the semi-arid US Southwest, where degradation over the past 150 years has been characterised by the invasion of woody vegetation into grasslands. The transition from grass to woody vegetation results in a change in ecosystem structure and function (Turnbull et al, 2008). Structural change is typically characterised by an increased heterogeneity of soil and vegetation resources, associated with reduced vegetation coverage. Functional change is characterised by an increased vulnerability to soil erosion and the potential loss of key nutrients to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is sequestered by these environments and the amount of carbon that is lost as the land becomes more degraded. Therefore, understanding these vegetation transitions is significant for sustainable land use and global biogeochemical cycling. Connectivity is a key concept in understanding the hydrological response to this vegetation change, with reduced vegetation coverage in woody environments being associated with longer and more connected overland flow pathways. This increase in hydrological connectivity results in an accentuated rainfall-runoff response and increased fluvial fluxes of eroded sediment and associated soil organic carbon and other nutrients. This project uses an ecohydrological approach, characterising ecological structure and monitoring natural rainfall-runoff events over bounded plots with different vegetation covering the transitions from C4 pure-grass (Bouteloua eriopoda) to C3 creosote (Larrea tridentate) shrubland and C3 piñon-juniper (Pinus edulis-Juniperus monosperma) mixed stand woodland. Data collected quantifies fluvial fluxes of sediment and associated soil organic matter and carbon that is lost from across the grass-to-shrub and grass-to-woodland transition (where change in space is taken to indicate a similar change through time). Structural characterisation data along with results collected during the 2010 and 2011 monsoon seasons will be presented; illustrating the usefulness of viewing environmental structure via the concept of connectivity when trying to understand fluxes of water, sediment and associated nutrients.

  13. The Regulation of Peace River: a Large-scale Experiment on Fluvial Governing Conditions

    NASA Astrophysics Data System (ADS)

    Church, M.

    2004-12-01

    In 1967, British Columbia Hydro and Power Authority closed W.A.C.Bennett Dam, creating what was then the sixth largest hydropower project in the world. The dam is located in the Rocky Mountain front range so that, although it controls about half the runoff of the 293 000 sq.km basin, almost all of the sediment load originates downstream from the dam in the Alberta Plateau. Hence, the effects of these two principal governing conditions of fluvial systems can be separated. The 378 km immediately downstream to the Smoky River confluence are a wandering, cobble-gravel reach It has effectively ceased to be alluvial and the channel pattern has been simplified. Aggradation is occurring at major tributary junctions, whilst the tributaries themselves have degraded in their lowermost reaches. Smoky River, the principal tributary, delivers a large sand load. The 250 km reach to Carcajou is sandy gravel and the final 600 km to the Peace-Athabasca delta is sand-bed. Aggradation, with a change in fluvial style toward low-order braiding, appears to be underway in the proximal sand-bed reach. More generally, channel shrinkage in response to the regulated flow regime is controlled by the rate of progradation of riparian vegetation onto former bar surfaces In 1996, after 29 years of regulated flow, reservoir drawdown for dam repairs led to full spillway flows for 8 consecutive weeks, creating an effectively bankfull condition in the proximal post-regulation channel. Significant degradation was observed for the first time in many cross-sections but overall changes were surprisingly modest, reflecting the refractory bed and the degree to which riparian vegetation has become firmly established in former channel areas. Overall, sediment supply and flow competence are the principal controls of fluvial response in the system. The experimental aspect of this study of a large, northward flowing, boreal river can be controlled by before-after comparison. However, this strategy must take into account a changing hydroclimate which has seen increased precipitation but decreased winter snowfall, the latter being the chief source of runoff. However, it can also be pursued by comparison with Liard River, of comparable scale and morphology, located to the north. In both rivers, winter ice regime represents a significant additional dimension for study.

  14. Palynostratigraphy and sedimentary facies of Middle Miocene fluvial deposits of the Amazonas Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Dino, Rodolfo; Soares, Emílio Alberto Amaral; Antonioli, Luzia; Riccomini, Claudio; Nogueira, Afonso César Rodrigues

    2012-03-01

    Palynostratigraphic and sedimentary facies analyses were made on sedimentary deposits from the left bank of the Solimões River, southwest of Manaus, State of Amazonas, Brazil. These provided the age-dating and subdivision of a post-Cretaceous stratigraphic succession in the Amazonas Basin. The Novo Remanso Formation is subdivided into upper and lower units, and delineated by discontinuous surfaces at its top and bottom. The formation consists primarily of sandstones and minor mudstones and conglomerates, reflecting fluvial channel, point bar and floodplain facies of a fluvial meandering paleosystem. Fairly well-preserved palynoflora was recovered from four palynologically productive samples collected in a local irregular concentration of gray clay deposits, rich in organic material and fossilized wood, at the top of the Novo Remanso Formation upper unit. The palynoflora is dominated by terrestrial spores and pollen grains, and is characterized by abundant angiosperm pollen grains ( Tricolpites, Grimsdalea, Perisyncolporites, Tricolporites and Malvacearumpollis). Trilete spores are almost as abundant as the angiosperm pollen, and are represented mainly by the genera Deltoidospora, Verrutriletes, and Hamulatisporis. Gymnosperm pollen is scarce. The presence of the index species Grimsdalea magnaclavata Germeraad et al. (1968) indicates that these deposits belong to the Middle Miocene homonymous palynozone (Lorente, 1986; Hoorn, 1993; Jaramillo et al., 2011). Sedimentological characteristics (poorly sorted, angular to sub-angular, fine to very-coarse quartz sands facies) are typical of the Novo Remanso Formation upper part. These are associated with a paleoflow to the NE-E and SE-E, and with an entirely lowland-derived palinofloristic content with no Andean ferns and gymnosperms representatives. All together, this suggests a cratonic origin for this Middle Miocene fluvial paleosystem, which was probably born in the Purus Arch eastern flank and areas surrounding the crystalline. The palynological analysis results presented herein are the first direct and unequivocal evidence of the occurrence of Middle Miocene deposits in the central part of the Amazonas Basin. They also provide new perspectives for intra- and interbasin correlations, as well as paleogeographic and paleoenvironmental interpretations for the later deposition stages in the northern Brazilian sedimentary basins.

  15. Fluvial Tufa Evidence of Late Pleistocene Wet Intervals from Santa Barbara, Southern California

    NASA Astrophysics Data System (ADS)

    Ibarra, Y.; Corsetti, F. A.; Feakins, S. J.; Rhodes, E. J.; Kirby, M. E.

    2014-12-01

    Past pluvials in the western United States provide valuable context for understanding regional hydroclimate variability. Here we report evidence of conditions substantially wetter than today from fluvial tufa deposits located near Zaca Lake, Santa Barbara County, California that have been dated by radiocarbon (14C) and Infra-Red Stimulated Luminescence (IRSL). Two successions of tufa deposition occur within a small catchment that drains Miocene Monterey Formation bedrock: 1) a fluvial deposit (0-0.5 m thick, 200 m in extent) that formed along a narrow valley below a modern spring, and 2) a perched deposit about 10 m higher (2 m thick, 15 m in extent). IRSL and radiocarbon dating of the perched carbonates suggests at least two episodes of carbonate growth: one at 19.4 ± 2.4 (1σ) through 17.8 ± 2.8 (1σ) ka and another at 11.9 ± 1.5 (1σ) ka verified with a charcoal 14C age of 10.95 ± 0.12 (2σ) cal ka BP. The relationship between the perched and fluvial spring deposits is inferred to represent a drop in the water table of more than 10 m associated with a transition from a wet climate in the late glacial to a dry Holocene today. The wet period indicated by tufa growth between 19.4 and 17.8 ka is relatively consistent with other California climate records both north and south of Zaca Lake. However, tufa growth ca. 12 to 11 ka demonstrates wet conditions occurred as far south as Zaca Lake during the Younger Dryas event, in contrast to climate records farther south in Lake Elsinore indicating persistently dry conditions through this interval. A small shift north in the average position of the winter season storm track could explain wet winters at Zaca while at the same time generating dry winters at Lake Elsinore, 275 km southwest of Zaca. If true, these data indicate that rather small latitudinal shifts in the average winter season storm track can produce large changes in regional hydroclimate.

  16. Development a fluvial detachment rate model to predict the erodibility of cohesive soils under the influence of seepage

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seepage influences the erodibility of streambanks, streambeds, dams, and embankments. Usually the erosion rate of cohesive soils due to fluvial forces is computed using an excess shear stress model, dependent on two major soil parameters: the critical shear stress (tc) and the erodibility coefficie...

  17. Paleocurrent and fabric analyses of the imbricated fluvial gravel deposits in Huangshui Valley, the northeastern Tibetan Plateau, China

    USGS Publications Warehouse

    Miao, X.; Lu, H.; Li, Z.; Cao, G.

    2008-01-01

    Gravel deposits on fluvial terraces contain a wealth of information about the paleofluvial system. In this study, flow direction and provenance were determined by systematic counts of more than 2000 clasts of imbricated gravel deposits in the Xining Region, northeastern Tibetan Plateau, China. These gravel deposits range in age from the modern Huangshui riverbed to Miocene-aged deposits overlain by eolian sediments. Our major objectives were not only to collect first-hand field data on the fluvial gravel sediments of the Xining Region, but also to the reconstruct the evolution of the fluvial system. These data may offer valuable information about uplift of the northeastern Tibetan Plateau during the late Cenozoic era. Reconstructed flow directions of the higher and lower gravel deposits imply that the river underwent a flow reversal of approximately 130-180??. In addition, the lithological compositions in the higher gravel deposits differ significantly from the lower terraces, suggesting that the source areas changed at the same time. Eolian stratigraphy overlying the gravel deposits and paleomagnetic age determination indicate that this change occurred sometime between 1.55??Ma and 1.2??Ma. We suggest that tectonic activity could explain the dramatic changes in flow direction and lithological composition during this time period. Therefore, this study provides a new scenario of fluvial response to tectonic uplift: a reversal of flow direction. In addition, field observation and statistical analyses reveal a strong relationship between rock type, size and roundness of clasts. ?? 2007 Elsevier B.V. All rights reserved.

  18. Monitoring Fluvial Erosion of Cohesive Materials Using the Photo-Electronic Erosion Pin Sensor in Clear Creek, IA

    NASA Astrophysics Data System (ADS)

    Bertrand, F.; Papanicolaou, T.

    2009-12-01

    Fluvial erosion incites significant bridge scour and large-scale bank erosion causing estimated $1.1 billion damage in the Midwest. Conventional, manual, field monitoring methods, typically erosion pins, cross-section resurveys or terrestrial photogrammetry, used to monitor fluvial erosion rates merely provide a net change in bank surface retreat since the previous measurement. If mass wasting has occurred, the ongoing fluvial erosion would be masked. Erosion event timing, and the precise bank response to individual flow or flow hydrograph changes, is generally uncertain. Thus, a technique that automatically quantifies bank erosion on a continuous basis is needed. This study will monitor the bank response to individual flow (i.e., fluvial erosion) using the Photo-Electronic Erosion Pin (PEEP) sensors in Clear Creek Iowa. It attends to monitor a full episode of bank change, including event timings and magnitude information for specific erosion and deposition events, which can be compared to flow discharges and hydrographs. If exploited, this method can lead to more detailed analysis of bank erosion related to temporal fluctuations in the suspected hydraulic forces.

  19. Turbidity in the fluvial Gironde Estuary (S-W France) based on 10 year continuous monitoring: sensitivity to hydrological conditions

    NASA Astrophysics Data System (ADS)

    Jalón-Rojas, I.; Schmidt, S.; Sottolichio, A.

    2015-03-01

    Climate change and human activities impact the volume and timing of freshwater input to estuaries. These modifications in fluvial discharges are expected to influence estuarine suspended sediment dynamics, and in particular the turbidity maximum zone (TMZ). Located in the southwest France, the Gironde fluvial-estuarine systems has an ideal context to address this issue. It is characterized by a very pronounced TMZ, a decrease in mean annual runoff in the last decade, and it is quite unique in having a long-term and high-frequency monitoring of turbidity. The effect of tide and river flow on turbidity in the fluvial estuary is detailed, focusing on dynamics related to changes in hydrological conditions (river floods, periods of low-water, inter-annual changes). Turbidity shows hysteresis loops at different time scales: during river floods and over the transitional period between the installation and expulsion of the TMZ. These hysteresis patterns, that reveal the origin of sediment, locally resuspended or transported from the watershed, may be a tool to evaluate the presence of remained mud. Statistics on turbidity data bound the range of river flow that promotes the TMZ installation in the fluvial stations. Hydrological indicators of the persistence and turbidity level of the TMZ are also defined. The long-term evolution of these indicators confirms the influence of discharge decrease on the intensification of the TMZ in tidal rivers, and provides a tool to evaluate future scenarios.

  20. A comparison of factors controlling sedimentation rates and wetland loss in fluvial-deltaic systems, Texas Gulf coast

    USGS Publications Warehouse

    White, W.A.; Morton, R.A.; Holmes, C.W.

    2002-01-01

    Submergence of coastal marshes in areas where rates of relative sea-level rise exceed rates of marsh sedimentation, or vertical accretion, is a global problem that requires detailed examination of the principal processes that establish, maintain, and degrade these biologically productive environments. Using a simple 210Pb-dating model, we measured sedimentation rates in cores from the Trinity, Lavaca-Navidad, and Nueces bayhead fluvial-deltaic systems in Texas where more than 2000 ha of wetlands have been lost since the 1950s. Long-term average rates of fluvial-deltaic aggradation decrease southwestward from 0.514 ?? 0.008 cm year -1 in the Trinity, 0.328 ?? 0.022 cm year -1 in the Lavaca-Navidad, to 0.262 ?? 0.034 cm year -1 in the Nucces. The relative magnitudes of sedimentation and wetland loss correlate with several parameters that define the differing fluvial-deltaic settings, including size of coastal drainage basin, average annual rainfall, suspended sediment load, thickness of Holocene mud in the valley fill, and rates of relative sea-level rise. There is some evidence that upstream reservoirs have reduced wetland sedimentation rates, which are now about one-half the local rates of relative sea-level rise. The extant conditions indicate that fluvial-deltaic marshes in these valleys will continue to be lost as a result of submergence and erosion. ?? 2002 Elsevier Science B.V. All rights reserved.

  1. Relationships Between the Medusae Fossae Formation (MFF), Fluvial Channels, and the Dichotomy Boundary Southeast of Nicholson Crater, Mars

    NASA Technical Reports Server (NTRS)

    Bradley, B. A.; Sakimoto, S. E. H.

    2001-01-01

    We use Mars Global Surveyor's Mars Orbiter Laser Altimeter (MOLA) and Mars Orbiter Camera (MOC) data to investigate the Medusae Fossae Formation (MFF) and its relationship to fluvial channels southeast of Nicholson Crater. In this area the MFF shows small-scale layering and is draped over Labou Vallis. Additional information is contained in the original extended abstract.

  2. A comparison of factors controlling sedimentation rates and wetland loss in fluvial deltaic systems, Texas Gulf coast

    NASA Astrophysics Data System (ADS)

    White, William A.; Morton, Robert A.; Holmes, Charles W.

    2002-04-01

    Submergence of coastal marshes in areas where rates of relative sea-level rise exceed rates of marsh sedimentation, or vertical accretion, is a global problem that requires detailed examination of the principal processes that establish, maintain, and degrade these biologically productive environments. Using a simple 210Pb-dating model, we measured sedimentation rates in cores from the Trinity, Lavaca-Navidad, and Nueces bayhead fluvial-deltaic systems in Texas where more than 2000 ha of wetlands have been lost since the 1950s. Long-term average rates of fluvial-deltaic aggradation decrease southwestward from 0.514±0.008 cm year -1 in the Trinity, 0.328±0.022 cm year -1 in the Lavaca-Navidad, to 0.262±0.034 cm year -1 in the Nueces. The relative magnitudes of sedimentation and wetland loss correlate with several parameters that define the differing fluvial-deltaic settings, including size of coastal drainage basin, average annual rainfall, suspended sediment load, thickness of Holocene mud in the valley fill, and rates of relative sea-level rise. There is some evidence that upstream reservoirs have reduced wetland sedimentation rates, which are now about one-half the local rates of relative sea-level rise. The extant conditions indicate that fluvial-deltaic marshes in these valleys will continue to be lost as a result of submergence and erosion.

  3. When do plants modify fluvial processes? Plant-hydraulic interactions under variable flow and sediment supply rates

    NASA Astrophysics Data System (ADS)

    Manners, Rebecca B.; Wilcox, Andrew C.; Kui, Li; Lightbody, Anne F.; Stella, John C.; Sklar, Leonard S.

    2015-02-01

    Flow and sediment regimes shape alluvial river channels; yet the influence of these abiotic drivers can be strongly mediated by biotic factors such as the size and density of riparian vegetation. We present results from an experiment designed to identify when plants control fluvial processes and to investigate the sensitivity of fluvial processes to changes in plant characteristics versus changes in flow rate or sediment supply. Live seedlings of two species with distinct morphologies, tamarisk (Tamarix spp.) and cottonwood (Populus fremontii), were placed in different configurations in a mobile sand-bed flume. We measured the hydraulic and sediment flux responses of the channel at different flow rates and sediment supply conditions representing equilibrium (sediment supply = transport rate) and deficit (sediment supply < transport rate). We found that the hydraulic and sediment flux responses during sediment equilibrium represented a balance between abiotic and biotic factors and was sensitive to increasing flow rates and plant species and configuration. Species-specific traits controlled the hydraulic response: compared to cottonwood, which has a more tree-like morphology, the shrubby morphology of tamarisk resulted in less pronation and greater reductions in near-bed velocities, Reynolds stress, and sediment flux rates. Under sediment-deficit conditions, on the other hand, abiotic factors dampened the effect of variations in plant characteristics on the hydraulic response. We identified scenarios for which the highest stem-density patch, independent of abiotic factors, dominated the fluvial response. These results provide insight into how and when plants influence fluvial processes in natural systems.

  4. Stratigraphy of the fluvial deposits of the Salado river basin, Buenos Aires Province: Lithology, chronology and paleoclimate

    NASA Astrophysics Data System (ADS)

    Fucks, E.; Pisano, M. F.; Huarte, R. A.; Di Lello, C. V.; Mari, F.; Carbonari, J. E.

    2015-07-01

    The regional landscape of the Salado depression is related to weathering, eolian and fluvial processes generated under different climatic conditions. Although during most of the Holocene the climatic conditions were warm and humid, previously, a vast plain dominated by deflation processes and enhanced by weathering processes was developed in an arid environment. Fluvial deposits produced afterwards are continuous and lithologically homogeneous, which allows differentiation and characterization of the entire stratigraphic sequence. The stratigraphic units of this area, closely related to the paleoclimatic conditions, are recognized and characterized. Three lithostratigraphic units of fluvial origin (Members) and two paleosols have been differentiated. The first ones were grouped in the Luján Formation. Some of the units are related to other ones previously recognized in this area (La Chumbiada Member and La Pelada Geosol), but others have no similarity or relationship with previously known units (Gorch and Puente Las Gaviotas Members, and Frigorífico Belgrano Geosol). Radiocarbon ages suggest that the fluvial sequences were deposited after the glacial maximum, corresponding to MIS 1, except for the basal levels of the lower member which is late Late Pleistocene. Although the general paleoclimatic conditions were related to warm and humid climate, events related to water deficits were also recognized, which could be related to the Younger Dryas, the middle Holocene and the late Holocene.

  5. Geoarchaeology, the four dimensional (4D) fluvial matrix and climatic causality

    NASA Astrophysics Data System (ADS)

    Brown, A. G.

    2008-10-01

    Geoarchaeology is the application of geological and geomorphological techniques to archaeology and the study of the interactions of hominins with the natural environment at a variety of temporal and spatial scales. Geoarchaeology in the UK over the last twenty years has flourished largely because it has gone beyond technological and scientific applications. Over the same period our ability to reconstruct the 3-dimensional stratigraphy of fluvial deposits and the matrix of fluvial sites has increased dramatically because of a number of technological advances. These have included the use of LiDAR (laser imaging) and radar to produce high-resolution digital surface models, the use of geophysics, particularly ground penetrating radar and electrical resistivity, to produce sediment depth models, and the use of GIS and data visualisation techniques to manipulate and display the data. These techniques along with more systematic and detailed sedimentological recording of exposed sections have allowed the construction of more precise 3-dimensional (volumetric) models of the matrix of artefacts within fluvial deposits. Additionally a revolution in dating techniques, particularly direct sediment dating by luminescence methods, has enabled the creation of 4-dimensional models of the creation and preservation of these sites. These 4-dimensional models have the ability to provide far more information about the processes of site creation, preservation and even destruction, and also allow the integration of these processes with independent data sources concerning cultural evolution and climatic change. All improvements in the precision of dating fluvial deposits have archaeological importance in our need to translate events from a sequential or geological timeframe to human timescales. This allows geoarchaeology to make a more direct contribution to cultural history through the recognition of agency at the individual or group level. This data can then form a component of biocomplexity or agent-based modelling which is becoming increasingly used in the natural sciences, particularly ecology and geomorphology and which can be used to test scenarios including the impact on, and response of, hominins to abrupt or catastrophic environmental change. Whilst catastrophic events clearly represent the atypical they can be illuminating in revealing cognitive processes resulting in abandonment, coping, mitigation and innovation. These points are exemplified using two in-depth case studies: one from the Holocene geoarchaeological record of the River Trent in Central England and the other from the Palaeolithic record from rivers in South West Britain. In the former the interaction between climate change and human activity is illustrated at the year to century timescale whilst in the other the timescale is millennial. These case studies have deliberately been chosen to be as different as possible in temporal and spatial scale with the aim of examining the applicability of methodological and theoretical aspects of geoarchaeology. Lastly the paper considers the problem of scale in geoarchaeology and concludes it is process-dependency, which ultimately affects the questions we can ask, and that questions of human response to climate change are fundamentally a product of materiality and cognitive processes. This demands an in-depth contextual approach to such questions rather than database-driven assertions of causality.

  6. Stream restoration in dynamic fluvial systems: Scientific approaches, analyses, and tools

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2012-04-01

    In the United States the average annual investment in river restoration programs is approximately $1 billion. Despite this burgeoning industry, the National Water Quality Inventory, which tracks the health of the nation's rivers, has shown no serious improvement in cumulative river health since the early 1990s. In the AGU monographStream Restoration in Dynamic Fluvial Systems: Scientific Approaches, Analyses, and Tools, editors Andrew Simon, Sean J. Bennett, and Janine M. Castro pull together the latest evidence-based understanding of stream restoration practices, with an aim of guiding the further development of the field and helping to right its apparently unsuccessful course. In this interview, Eos talks to Sean J. Bennett, University of Buffalo, about the culture, practice, and promise of restoring rivers.

  7. Reservoir Characterization, Production Characteristics, and Research Needs for Fluvial/Alluvial Reservoirs in the United States

    SciTech Connect

    Cole, E.L.; Fowler, M.L.; Jackson, S.R.; Madden, M.P.; Raw-Schatzinger, V.; Salamy, S.P.; Sarathi, P.; Young, M.A.

    1999-04-28

    The Department of Energy's (DOE's) Oil Recovery Field Demonstration Program was initiated in 1992 to maximize the economically and environmentally sound recovery of oil from known domestic reservoirs and to preserve access to this resource. Cost-shared field demonstration projects are being initiated in geology defined reservoir classes which have been prioritized by their potential for incremental recovery and their risk of abandonment. This document defines the characteristics of the fifth geological reservoir class in the series, fluvial/alluvial reservoirs. The reservoirs of Class 5 include deposits of alluvial fans, braided streams, and meandering streams. Deposit morphologies vary as a complex function of climate and tectonics and are characterized by a high degree of heterogeneity to fluid flow as a result of extreme variations in water energy as the deposits formed.

  8. Glacial, fluvial and volcanic landscape evolution in the Laguna Potrok Aike maar area, Southern Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Coronato, Andrea; Ercolano, Bettina; Corbella, Hugo; Tiberi, Pedro

    2013-07-01

    We describe the Pleistocene evolution of the landscape in the Laguna Potrok Aike area in southern Patagonia, Argentina, based on a geomorphological survey. Basaltic eruptions generated tablelands and scoria cones between the Late Miocene and Middle Pleistocene, and phreatomagmatic eruptions produced maars during Middle and Late Pleistocene time. The first glaciations during the Early Pleistocene generated a gently undulating to flat landscape that was affected by cryogenic processes; they are documented but not dated. Outwash surfaces indicate that the Greatest Patagonian Glaciation was multi-phased. The eruption that produced Potrok Aike maar truncated terrace levels dating to a Middle Pleistocene glaciation. The abundance of maars dating to this time may be linked to large amounts of water associated with meltwater streams and permafrost. The landscape in the Potrok Aike area has changed little since the Middle Pleistocene and only minor modifications of landforms have occurred due to cryogenesis, moderate fluvial incision, mass wasting and eolian activity.

  9. Temporal trends in fluvial-sediment discharge in Ohio, 1950-1987

    USGS Publications Warehouse

    Hindall, S.M.

    1991-01-01

    Long-term fluvial-sediment records of annual suspended-sediment discharge data are available for eight daily suspended-sediment stations operated in Ohio. Graphical and statistical analyses of long-term sediment records indicate that, in general, no long-term (>3- to 5-year) trends are readily apparent in the relation between annual mean suspended-sediment discharge and water discharge in Ohio; however, some short-term, year-to-year changes in that relation occur for Ohio streams. Double-mass curves for five daily suspended-sediment stations and seasonal Kendall analysis of data from eight daily suspended-sediment stations clearly illustrate the lack of any discernible changes in the suspended-sediment-discharge/water-discharge relation or in suspended-sediment concentration for most Ohio streams over the past 36 years. -from Author

  10. The Origin of Warrego Valles: A Case Study for Fluvial Valley Formation on Early Mars

    NASA Technical Reports Server (NTRS)

    Gulick, Virginia C.; Dohm, James; Tanaka, Ken; Hare, Trent

    2000-01-01

    Warrego Valles is one of the best examples of a well integrated fluvial valley system that formed early in the geological history of Mars, the lack of similar erosion elsewhere along the edge of Thaumasia plateau is not consistent with a formation by rainfall. Instead the radial pattern of this valley system centered on a region of localized uplift argues for a more localized water source. We conclude that this uplift was most likely the result of a subsurface magmatic intrusion and that the estimated volume of this intrusion is sufficient to cause enough hydrothermal ground-water outflow to form the valley system. A possible alternative to this scenario is hydrothermal ground-water outflow combined with a melting snow pack.

  11. A unified framework for stability of channel bifurcations in gravel and sand fluvial systems

    NASA Astrophysics Data System (ADS)

    Bolla Pittaluga, Michele; Coco, Giovanni; Kleinhans, Maarten G.

    2015-09-01

    Bifurcating rivers shape natural landscapes by distributing water and sediments on fluvial plains and in deltas. Symmetrical bifurcations were often found to be unstable so that one branch downstream of the bifurcation enlarged while the other dwindled. A unified theory able to predict bifurcation stability in both gravel bed and sand bed rivers is still lacking. Here we develop a new theory for the stability of bifurcations for the entire range of gravel bed to sand bed rivers. The theory indicates opposite behavior of gravel bed and sand bed rivers: we predict that symmetrical bifurcations are inherently stable for intermediate Shields stresses but are inherently unstable for the low and high Shields stresses found in the majority of rivers on Earth. In the latter conditions asymmetrical bifurcations are stable. These predictions are corroborated by observations and have ramifications for many environmental problems in fluviodeltaic settings.

  12. Quality assurance practices for the chemical and biological analyses of water and fluvial sediments

    USGS Publications Warehouse

    Friedman, Linda C.; Erdmann, David E.

    1982-01-01

    This chapter contains practices used by the U.S. Geological Survey to assure the quality of analytical data for water, fluvial sediment, and aquatic organisms. These practices are directed primarily toward personnel making water quality measurements. Some detail specific quality control techniques, others document quality assurance procedures being used by the Central Laboratories System of the U.S. Geological Survey, and still others describe various statistical techniques and give examples of their use in evaluating and assuring the quality of analytical data. The practices are arranged into eight sections: Analytical Methods Development Procedures, Standard Quantitative Analysis Techniques, Instrumental Techniques, Reference Material, Laboratory Quality Control; Quality Assurance Monitoring; Documentation, Summary, and Evaluation of Data, Materials Evaluation. Each section is preceded by a brief description of the material covered. Similarly within each section, each practice is preceded by a description of its application or scope.

  13. Holocene monsoonal dynamics and fluvial terrace formation in the northwest Himalaya, India

    NASA Astrophysics Data System (ADS)

    Bookhagen, B.; Fleitmann, D.; Nishiizumi, K.; Strecker, M. R.; Thiede, R. C.

    2006-07-01

    Aluminum-26 and beryllium-10 surface exposure dating on cut-and-fill river-terrace surfaces from the lower Sutlej Valley (northwest Himalaya) documents the close link between Indian Summer Monsoon (ISM) oscillations and intervals of enhanced fluvial incision. During the early Holocene ISM optimum, precipitation was enhanced and reached far into the internal parts of the orogen. The amplified sediment flux from these usually dry but glaciated areas caused alluviation of downstream valleys up to 120 m above present grade at ca. 9.9 k.y. B.P. Terrace formation (i.e., incision) in the coarse deposits occurred during century-long weak ISM phases that resulted in reduced moisture availability and most likely in lower sediment flux. Here, we suggest that the lower sediment flux during weak ISM phases allowed rivers to incise episodically into the alluvial fill.

  14. Effect of metals on Daphnia magna and cladocerans representatives of the Argentinean fluvial littoral.

    PubMed

    Luciana, Regaldo; Reno, Ulises; Gervasio, Susana; Horacio, Troiani; Gagneten, Ana María

    2014-07-01

    Chronic toxicity tests were conducted to assess the effect of Cu, Cr and Pb on Moinodaphnia macleayi and Ceriodaphnia dubia -two cladoceran species from the Argentinian Fluvial Littoral Zone (AFLZ)- and Daphnia magna -an holarctic species-. The specimens were exposed to three concentrations of each metal. As endpoints, the number of living and dead organisms, molts, neonates released, and the age of first reproduction were recorded. Chronic assays showed that Cu significantly affected the analyzed life history traits in the three species. The lowest Pb and Cr concentrations did not affect survival, molting or fecundity in D. magna. Conversely, in M. macleayi and C. dubia, survival, molting and fecundity showed highly significant differences in all the concentrations tested compared to control assay. The present study stresses the importance of using biological parameters as bioindicators, as well as the study species from the Southern Hemisphere to assess metal pollution. PMID:25004754

  15. Lower Vistula fluvial lakes as possible places of deep groundwaters effluence (Grudziądz Basin, North Central Poland)

    NASA Astrophysics Data System (ADS)

    Kordowski, Jaroslaw; Kubiak-Wójcicka, Katarzyna; Solarczyk, Adam; Tyszkowski, Sebastian

    2014-05-01

    Regarding the outflow the Vistula River is the largest river in the Baltic catchment. In its lower course, below Bydgoszcz, in the Late Holocene Vistula channel adopted an weakly anastomosing fluvial pattern destroyed by intensive human hydrotechnical activity and by the regulation which have intensified about 200 years ago. Channel regulation have left many artificially separated fluvial lakes. Part of them infilled rapidly but the majority have persisted to present day almost unchanged. It has also arised the question: what drives the resistence for silting? To solve the problem there were conducted simultaneous hydrological and geomorphological investigations, because there were two concepts: one that the mineral material is removed from fluvial lakes while high stands by flood waters and second that the material is removed due to high groundwater "exchange" rate when the fluvial lake has a sufficient hydrological connectivity to the main Vistula channel. The Vistula valley crosses morainic plains of the last glaciation. On the average it has about 10 km width and is incised about 70 - 80 m deep, compared to neighbouring plains, dissecting all the Quaternary aquifers. On the floodplain area the Quaternary sediments lay with a layer of only 10-20 m thickness over Miocene and Oligocene sands. In favourable conditions, particularly while a low stand there exists the possibility of Tertiary water migration toward the surface of fluvial lakes provided they have not continuous flood sediments cover on their floors. As an example of such a lake with an intensive water exchange rate by supposed deep groundwaters was chosen the Old Vistula lake (Stara Wisła) near Grudziądz town. The lake has an area of 40 ha, mean depth 1,73 m, maximum depth 8 m, length about 4 km and medium width about 100 m. In the years 2011-2014, with two weeks frequency, in its surficial water layer were conducted measures which included temperature, pH, Eh, suspended matter amount, total and carbonaceous mineralization. Similar measurements were also conducted in other fluvial lakes and Vistula tributaries. Investigations carried proved the general similarity between physical and chemical properties of lakes and watercourses analysed. However, there exists distinct gradient of carbonaceous mineralization from small values in the Vistula channel to high values at the valley edges. PH and Eh parameters in the Old Vistula lake were different than in all other surveyed sites what leads to conclusion that it is fed by deeper groundwaters than in the case of other fluvial lakes and Vistula tributaries, particularly in low water stand times. Acknowledgements: This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution (ICLEA) of the Helmholtz Association.

  16. Fluvial system evolution and environmental changes during the Holocene in the Mue valley (Western France)

    NASA Astrophysics Data System (ADS)

    Lespez, Laurent; Clet-Pellerin, Martine; Limondin-Lozouet, Nicole; Pastre, Jean-François; Fontugne, Michel; Marcigny, Cyril

    2008-06-01

    Geomorphological and palaeoenvironmental research on Holocene sedimentation in the Mue valley provides evidence for fluvial system changes related to climate and human activities in Normandy, a poorly studied area of the Paris basin. The 24-km long valley bottom has been investigated through a systematic survey. It shows an original longitudinal sedimentary pattern in relation with valley morphology and local geological controls. Minerogenic, tufaceous and peaty deposits provide opportunities for multi-proxy analyses and radiocarbon dating control. Sedimentation began around 9500 14C BP with silt deposition in a meandering system. The Boreal and the Lower Atlantic periods (8500-6000 14C BP) were mainly characterized by unlithified calcareous tufa. Locally, these deposits are very thick (7 to 13 m). The tufa formed barrages across the valley bottom, providing an autogenic control on upstream sedimentation. During the Upper Atlantic period (6000-4700 14C BP), the valley experienced a decrease in calcareous sedimentation and the development of organic deposits. At the beginning of the Subboreal (4700-3500 14C BP), peat deposits expanded, especially behind the tufa barrages. The valley bottom was characterized by large marshy areas whereas the regional vegetation was progressively modified by human activities. At the end of the Subboreal (3300-3000 14C BP) the infilling of the valley by calcareous silt was caused by an increase of river activity related to climatic and land use changes. From the Iron Age and Gallo-Roman periods (2800-1700 14C BP), the valley bottom was filled by silty overbank deposits related to an increase of soil erosion. The slopes and river system were once again coupled and the fluvial system functioned as a continuum from upstream to downstream. The alluvial record of the Mue valley reflects a broad regional pattern of environmental changes but presents particular features, which highlight the need of longitudinal studies to take into account spatial and temporal discontinuities of Holocene hydro-sedimentary systems, even in small order valleys.

  17. 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.

  18. Interacting effects of climate and agriculture on fluvial DOM in temperate and subtropical catchments

    NASA Astrophysics Data System (ADS)

    Graeber, D.; Goyenola, G.; Meerhoff, M.; Zwirnmann, E.; Ovesen, N. B.; Glendell, M.; Gelbrecht, J.; Teixeira de Mello, F.; Gonzalez-Bergonzoni, I.; Jeppesen, E.; Kronvang, B.

    2015-05-01

    Dissolved organic matter (DOM) is an important factor in aquatic ecosystems, which is involved in a large variety of biogeochemical and ecological processes, and recent literature suggests that it could be strongly affected by agriculture in different climates. Based on novel monitoring techniques, we investigated the interaction of climate and agriculture effects on DOM quantity and quality. To examine this, we took water samples over 2 years in two paired intensive and extensive farming catchments in each of Denmark (temperate climate) and Uruguay (subtropical climate). We measured dissolved organic carbon (DOC) and nitrogen (DON) concentrations and DOC and DON molecular fractions with size-exclusion chromatography. Moreover, we characterized DOM quality with absorbance and fluorescence measurements, as well as parallel factor analysis (PARAFAC). We also calculated the DOC and DON loads based on daily discharge measurements, as well as measured precipitation and air temperature. The fluvial DOM in the catchments in Uruguay was characterized by higher temporal variability of DOC and DON loads which were clearly to a higher temporal variability of precipitation and a DOM composition with rather plant-like character relative to the Danish catchments. Moreover, we found a consistently higher temporal variability of DOC and DON loads in the intensive farming catchments than in the extensive farming catchments, with highest temporal variability in the Uruguayan intensive farming catchment. Furthermore, the composition of DOM exported from the intensive farming catchments was consistently complex and always related to microbial processing in both Denmark and Uruguay. This was indicated by low C : N ratios, several spectroscopic DOM composition indices and PARAFAC fluorescence components. We propose that the consistent effect of intensive farming on DOM composition and the temporal variability of DOC and DON loads is related to similarities in the management of agriculture, which may have widescale implications for fluvial DOM composition, as well as related ecological processes and biogeochemical cycles.

  19. Mineralogical and chemical variability of fluvial sediments. 1. Bedload sand (Ganga-Brahmaputra, Bangladesh)

    NASA Astrophysics Data System (ADS)

    Garzanti, Eduardo; And, Sergio; France-Lanord, Christian; Vezzoli, Giovanni; Censi, Paolo; Galy, Valier; Najman, Yani

    2010-11-01

    This study investigates the natural processes that control concentration of detrital minerals and consequently chemical elements in river sand. The novelty of our approach consists in the systematic integration of detailed textural, petrographical, mineralogical and chemical data, and in the quantitative description and modeling of relationships among mineralogical and chemical variables for each sample and each grain-size class in each sample. Bed sediment in transit in the largest sedimentary system on Earth chiefly consists of fine-grained lithofeldspathoquartzose sand including rich amphibole-epidote-garnet suites, mixed with minor very-fine-grained-sand to silt subpopulations containing less heavy minerals and representing intermittent suspension. Mineralogical and particularly chemical differences between Ganga and Brahmaputra bedload are orders of magnitude less than both intersample variability associated with selective-entrainment effects and intrasample variability associated with settling-equivalence effects. Any provenance interpretation of mineralogical, chemical, or detrital-geochronology datasets therefore requires quantitative understanding of hydraulically controlled compositional variability. Mineralogical and chemical, intrasample and intersample variability can be deduced with simple equations and numerical solutions. The underlying assumptions on the chemical composition of detrital minerals, as well as the possible pitfalls, uncertainties and approximations involved are discussed. Principal results include calibration of rare REE-bearing ultradense minerals, ill-determined by optical analyses but crucial in both detrital-geochronology and settling-equivalence studies, and assessment of progressively changing concentration for any detrital component with increasing intensity of selective-entrainment effects. Contributions by each mineral group to the chemical budget were inferred with sufficient precision and accuracy. Although complex because of diverse controlling factors including provenance, weathering and anthropogenic pollution, mineralogical and consequently chemical variability of fluvial sediments can be quantitatively predicted. This path, difficult because of insufficient information but far from hopeless, shall eventually lead to more accurate calculation of sediment fluxes and chemical budgets, as well as to a deeper understanding of sedimentary geochemistry and fluvial sedimentology.

  20. Short-term post-wildfire dry-ravel processes in a chaparral fluvial system

    NASA Astrophysics Data System (ADS)

    Florsheim, Joan L.; Chin, Anne; O'Hirok, Linda S.; Storesund, Rune

    2016-01-01

    Dry ravel, the transport of sediment by gravity, transfers material from steep hillslopes to valley bottoms during dry conditions. Following wildfire, dry ravel greatly increases in the absence of vegetation on hillslopes, thereby contributing to sediment supply at the landscape scale. Dry ravel has been documented as a dominant hillslope erosion mechanism following wildfire in chaparral environments in southern California. However, alteration after initial deposition is not well understood, making prediction of post-fire flood hazards challenging. The majority of Big Sycamore Canyon burned during the May 2013 Springs Fire leaving ash and a charred layer that covered hillslopes and ephemeral channels. Dry-ravel processes following the fire produced numerous deposits in the hillslope-channel transition zone. Field data focus on: 1) deposition from an initial post-wildfire dry-ravel pulse; and 2) subsequent alteration of dry ravel deposits over a seven-month period between September 2013 and April 2014. We quantify geomorphic responses in dry ravel deposits including responses during the one small winter storm that generated runoff following the fire. Field measurements document volumetric changes after initial post-wildfire deposition of sediment derived from dry ravel. Erosion and deposition mechanisms that occurred within dry-ravel deposits situated in the hillslope-channel transition zone included: 1) mobilization and transport of a portion or the entire deposit by fluvial erosion; 2) rilling on the surface of the unconsolidated deposits; 3) deposition on deposits via continued hillslope sediment supply; and 4) mass wasting that transfers sediment within deposits where surface profiles are near the angle of repose. Terrestrial LiDAR scanning point clouds were analyzed to generate profiles quantifying depth of sediment erosion or deposition over remaining dry ravel deposits after the first storm season. This study contributes to the understanding of potential effects of wildfire on fine sediment delivery to fluvial systems in chaparral ecosystems.

  1. Neotectonic characteristics of Liuchia fault, southwestern Taiwan, from the analysis of fluvial channel morphology

    NASA Astrophysics Data System (ADS)

    Du, Kuan-Ying; Shyu, J. Bruce H.

    2013-04-01

    The Liuchia fault in southwestern Taiwan has been considered as one of major active faults in the active Taiwan orogen. It is identified by its clear geomorphic features, and forms a major geologic boundary of Taiwan's Western Foothills. In the twentieth century, several large earthquakes occurred in southwestern Taiwan and caused significant damages. However, there is no unanimous historical evidence for the activity on the Liuchia fault. Therefore, the Liuchia fault poses large hazard potentials for this populous area. Several previous studies have shown that fluvial channel morphology, such as channel slope and width, is strongly influenced by tectonic activities. As river channels reach steady state, the rock uplift would be balanced by the incision of river channels. Base on these hypotheses, it has been shown previously that the analysis of river channel morphology can successfully estimate the activity of potentially active faults in central Taiwan. As a result, we attempted to obtain information of recent activity of the Liuchia fault by analyzing the channel morphology of the Erchung River, which flows across the fault. We also attempted to calculate the actual river incision rates from the age of river terraces along the river. Such information would enable us to construct the subsurface geometry of this important active structure. We have obtained a detailed river long profile of the Erchung River from surveys using RTK-GPS, and the channel width profile from actual field measurements using a Laser Rangefinder. The fluvial channel morphology of the Erchung River appears to have been affected by active folding in the hanging-wall block of the Liuchia fault. Such active deformation pattern is also evident from river incision rate patterns, calculated from the ages and elevations of river terraces along the channel. We have also measured bedrock attitudes across the Liuchia fault and into its hanging-wall block. Combing these different datasets, we are able to construct a realistic model of the subsurface geometry of the Liuchia fault in southwestern Taiwan.

  2. Fluvial Morphology and Bedform Migration in the Ebb Tidal Dominated Duplin River, Georgia

    NASA Astrophysics Data System (ADS)

    Straub, J. A.; Hill, J. C.; Viso, R. F.; Peterson, R. N.; Carter, M. L.

    2014-12-01

    The Duplin River is an ebb-domintated, salt marsh drainage system west of Sapelo Island, Georgia. With no riverine input, flow in the Duplin is dependent on local surface run off, groundwater discharge and tidal flushing. Repeat multibeam bathymetry surveys within this system provide insight into sediment transport, current dynamics, and the migration of bottom features. Examination of bathymetric changes and the rate of bedform migration can be used to help estimate net sediment transport in fluvial and tidal systems. The swath bathymetry data presented here were collected during December 2009, March 2013, and June 2013 (high and low tide) aboard a small survey vessel, using a pole-mounted Kongsberg EM3002d multibeam bathymetry system. Along-stream profiles from bathymetry data collected during a single spring tidal cycle show little bedform migration, while the more temporally distant profiles record significant shifts in both small (cm-scale) and large (m-scale) bedform position, as well as changes in the morphology of large erosional scour depressions. Previous work has suggested the larger bedforms, which maintain an ebb-oriented geometry through both ebb and flood tide, are indicative of sediment transport rates that are an order of magnitude greater during the ebb tide (Zarillo, 1985). The new data suggest punctuated events, such as storm surges, may also play an important role in the fluvial transport, although more analysis is needed to determine how sediment storage changes in the Duplin river system over multiple tidal cycles. Integration of topographic LiDAR data, vegetation patterns, sediment composition, groundwater inputs and planform river morphology will also provide insight into sediment storage and transport within the system.

  3. Quantifying fluvial gravel surface and sub-surface topography using photogrammetry

    NASA Astrophysics Data System (ADS)

    Pattison, Ian; Chandler, Jim; Rice, Stephen

    2013-04-01

    Quantifying the structure of river beds is important for many aspects of fluvial geomorphology, including understanding small scale sediment transport/entrainment processes and the functionality of aquatic habitats. Close range photogrammetry can be used to obtain high resolution representations of the river bed structure. However, previous work has been limited to 2D (and a maximum of 2.5D) digital elevation models. This study aims to quantify the 3D structure of fluvial gravels using close range photogrammetry. This will provide knowledge of both the surface topography and additionally the sub-surface gravel structure. The 3D structure will be obtained by taking digital photographs of the gravel surface, before then incrementally removing the surface layer and repeating the process. The sequential photographs are then analysed using PhotoModeller software and the modelled DEM's extracted for further analysis. Obtaining a 3D structure will allow important properties such as grain size, shape, porosity, intra-gravel pore connectivity to be extracted. This technique will have applications in studies concerning salmonid spawning habitat, where our understanding of the egg incubation zone (also called a redd) is minimal, with only bulk properties known. This approach will allow a greater insight and understanding of the sub-surface intra-gravel habitat and processes that occur. Another application of this approach could be investigating the impact of flood flows on sub-surface gravel structure. Surface imbrication of the river bed gravels results from high flows, but it is unknown whether there is any sub-surface distinction between gravels that have been water-worked and ones that have not.

  4. Microbiological Comparisons within and across Contiguous Lacustrine, Paleosol, and Fluvial Subsurface Sediments

    PubMed Central

    Kieft, T. L.; Fredrickson, J. K.; McKinley, J. P.; Bjornstad, B. N.; Rawson, S. A.; Phelps, T. J.; Brockman, F. J.; Pfiffner, S. M.

    1995-01-01

    Twenty-six subsurface samples were collected from a borehole at depths of 173.3 to 196.8 m in the saturated zone at the Hanford Site in south-central Washington State. The sampling was performed throughout strata that included fine-grained lacustrine (lake) sediments, a paleosol (buried soil) sequence, and coarse-grained fluvial (river) sediments. A subcoring method and tracers were used to minimize and quantify contamination to obtain samples that were representative of subsurface strata. Sediment samples were tested for total organic carbon, inorganic carbon, total microorganisms by direct microscopic counts, culturable aerobic heterotrophs by plate counts, culturable anaerobes by most-probable-number enumeration, basal respiration rates, and mineralization of (sup14)C-labeled glucose and acetate. Total direct microscopic counts of microorganisms were low, ranging from below detection to 1.9 x 10(sup5) cells g (dry weight)(sup-1). Culturable aerobes and anaerobes were below minimum levels of detection in most samples. Direct microscopic counts, basal respiration rates, and (sup14)C-glucose mineralization were all positively correlated with total organic carbon and were highest in the lacustrine sediments. In contrast to previous subsurface studies, these saturated-zone samples did not have higher microbial abundance and activities than unsaturated sediments sampled from the same borehole, the fine-textured lacustrine sediment had higher microbial numbers and activities than the coarse-textured fluvial sands, and the paleosol samples did not have higher biomass and activities relative to the other sediments. The results of this study expand the subsurface microbiology database to include information from an environment very different from those previously studied. PMID:16534940

  5. Enhancing the natural removal of As in a reactive fluvial confluence receiving acid drainage

    NASA Astrophysics Data System (ADS)

    Abarca, M. I.; Arce, G.; Montecinos, M.; Guerra, P. A.; Pasten, P.

    2014-12-01

    Fluvial confluences are natural reactors that can determine the fate of contaminants in watersheds receiving acid drainage. Hydrological, hydrodynamic and chemical factors determine distinct conditions for the formation of suspended particles of iron and aluminum oxyhydroxides. The chemical and physical properties of these particle assemblages (e.g. particle size, chemical composition) can vary according to inflow mixing ratios, hydrodynamic velocity profiles, and chemical composition of the flows mixing at the confluence. Due to their capacity to sorb metals, it is important to identify the optimal conditions for removing metals from the aqueous phase, particularly arsenic, a contaminant frequently found in acid drainage. We studied a river confluence in the Lluta watershed, located in the arid Chilean Altiplano. We performed field measurements and laboratory studies to find optimal mixing ratio for arsenic sorption onto oxyhydroxide particles at the confluence between the Azufre (pH=2, As=2 mg/L) and the Caracarani river (pH=8, As<0.1 mg/L). As the contribution of the acidic stream increased, the concentration of Fe and Al in the solid phase reached a peak at different pHs. Although the optimal pH for As sorption was ~3, the overall maximum removal of As at the confluence, ocurred for pH~4. This is produced because optimal As sorption does not occur necessarily for the highest concentrations of particles being formed. We propose that fluvial confluences could be engineered to enhance the natural attenuation of contaminants. An analogy between confluences and coagulation-flocculation-sedimentation drinking water plants could be used to engineer such intervention.Acknowledgements: Proyecto Fondecyt 1130936 and Proyecto CONICYT FONDAP 15110020

  6. Fluvial changes of the Guadalquivir river during the Holocene in Córdoba (Southern Spain)

    NASA Astrophysics Data System (ADS)

    Uribelarrea, David; Benito, Gerardo

    2008-08-01

    Holocene fluvial changes of the Guadalquivir River at Córdoba City were studied with an emphasis on floodplain development, river migration rates, sedimentation rates and environmental history. During the Holocene, the Guadalquivir River has developed a large meander (El Arenal) with a general southwards lateral migration, undercutting Tertiary bedrock, and with a total incision of 9 m, which developed three alluvial surfaces: Fp1, Fp2 and Fp3. The oldest floodplain surface Fp1 (+ 7-9 m) was deposited during the early Holocene and reached its maximum extent around 1000 yr BP. The next floodplain surface Fp2 (+ 5 m) accumulated 500 to 1000 yr ago. Finally, the youngest floodplain surface (Fp3, + 1-2 m) was developed in the last 500 yr. Migration rates and direction changed from 690-480 m 2 yr - 1 in Fp1 (to the southeast), 2280 m 2 yr - 1 in Fp2 and 620 m 2 yr - 1 in Fp3 (to the west). The stratigraphical study of palaeomeanders and chute channel deposits show evidence of river position and dynamics through recent times: (1) "San Eduardo" was filled 4000 yr BP; (2) "Madre Vieja" has been active since 2100 yr BP to the present day; and (3) "El Cortijo" was formed and filled during historical times (the last 1000 yr). The chronology of the alluvial stratigraphy and fluvial dynamics are discussed within the context of historical hydrologic, climatic and anthropogenic changes. In addition, the geomorphological reconstruction of the riverine landscape in historical times provided some clue to the location of Medinat al-Zahira, a lost Muslim settlement built in the 10th century AD and believed to be situated at, or nearby, the Arenal meander. Paleogeographical analysis shows that the most suitable conditions for this medieval settlement were found on the northeast part of the Arenal meander.

  7. Contrasting vulnerability of drained tropical and high-latitude peatlands to fluvial loss of stored carbon

    NASA Astrophysics Data System (ADS)

    Evans, Chris D.; Page, Susan E.; Jones, Tim; Moore, Sam; Gauci, Vincent; Laiho, Raija; Hruška, Jakub; Allott, Tim E. H.; Billett, Michael F.; Tipping, Ed; Freeman, Chris; Garnett, Mark H.

    2014-11-01

    Carbon sequestration and storage in peatlands rely on consistently high water tables. Anthropogenic pressures including drainage, burning, land conversion for agriculture, timber, and biofuel production, cause loss of pressures including drainage, burning, land conversion for agriculture, timber, and biofuel production, cause loss of peat-forming vegetation and exposure of previously anaerobic peat to aerobic decomposition. This can shift peatlands from net CO2 sinks to large CO2 sources, releasing carbon held for millennia. Peatlands also export significant quantities of carbon via fluvial pathways, mainly as dissolved organic carbon (DOC). We analyzed radiocarbon (14C) levels of DOC in drainage water from multiple peatlands in Europe and Southeast Asia, to infer differences in the age of carbon lost from intact and drained systems. In most cases, drainage led to increased release of older carbon from the peat profile but with marked differences related to peat type. Very low DOC-14C levels in runoff from drained tropical peatlands indicate loss of very old (centuries to millennia) stored peat carbon. High-latitude peatlands appear more resilient to drainage; 14C measurements from UK blanket bogs suggest that exported DOC remains young (<50 years) despite drainage. Boreal and temperate fens and raised bogs in Finland and the Czech Republic showed intermediate sensitivity. We attribute observed differences to physical and climatic differences between peatlands, in particular, hydraulic conductivity and temperature, as well as the extent of disturbance associated with drainage, notably land use changes in the tropics. Data from the UK Peak District, an area where air pollution and intensive land management have triggered Sphagnum loss and peat erosion, suggest that additional anthropogenic pressures may trigger fluvial loss of much older (>500 year) carbon in high-latitude systems. Rewetting at least partially offsets drainage effects on DOC age.

  8. Contrasting depositional styles in Tertiary fluvial deposits of Nenana coal field, central Alaska

    SciTech Connect

    Stanley, R.G.; Flores, R.M.; Wiley, T.J. )

    1989-03-01

    Oligocene and Miocene fluvial deposits contain about 1.4 billion tons of minable subbituminous coal in the Nenana coal field and are prospective for petroleum in the nearby Middle Tanana basin. These deposits, in ascending stratigraphic order, are in the Healy Creek, Suntrana, and Lignite Creek Formations of the Usibelli Group. To better understand the depositional setting of these units, the authors studied their facies and microarchitecture in outcrops along Suntrana and Healy Creeks, about 120 km southwest of Fairbanks. The lower Healy Creek Formation consists mainly of amalgamated, basally scoured, lenticular conglomerates and sandstones. The conglomerates are normally graded and crudely imbricated, and the sandstones exhibit planar, trough, and ripple cross-stratification. These were likely deposited by migrating longitudinal and transverse bars in braided streams. Minor channel-form lenses of mudstone also occur and probably represent quiet-water deposition in abandoned channels. In contrast, the Suntrana Formation includes several fining-upward sequences in which normally graded pebble conglomerates and cross-stratified sandstones are overlain by mudstones and finally by coals as much as 6 m thick. The conglomerates and sandstones are interpreted as stacked high-energy fluvial channels that were filled by longitudinal gravel bars, sandy midchannel bars, and point bars. The overlying mudstones occupy a series of crosscutting abandoned channels that suggest a complex history of channel abandonment and reoccupation by high-sinuosity streams. Fining-upward sequences also occur in the Lignite Creek Formation, but they differ from those in the underlying Suntrana Formation by having fewer mud-filled abandoned channels, thick intervals of flood-plain mudstone with well-developed crevasse-splay sandstones, and thinner coals (generally < 1 m thick).

  9. Dynamic connectivity in a fluvial network for identifying hotspots of geomorphic change

    NASA Astrophysics Data System (ADS)

    Czuba, Jonathan A.; Foufoula-Georgiou, Efi

    2015-03-01

    Dynamical processes occurring on the hierarchical branching structure of a river network tend to heterogeneously distribute fluxes on the network, often concentrating them into "clusters," i.e., places of excess flux accumulation. Here, we put forward the hypothesis that places in the network predisposed (due to process dynamics and network topology) to accumulate excess sediment over a considerable river reach and over a considerable period of time reflect locations where a local imbalance in sediment flux may occur thereby highlighting a susceptibility to potential fluvial geomorphic change. We develop a dynamic connectivity framework which uses the river network structure and a simplified Lagrangian transport model to trace fluxes through the network and integrate emergent "clusters" through a cluster persistence index (CPI). The framework was applied to sand transport in the Greater Blue Earth River Network in the Minnesota River Basin. Three hotspots of fluvial geomorphic change were defined as locations where high rates of channel migration were observed and places of high CPI coincided with two of these hotspots of possibly sediment-driven change. The third hotspot was not identified by high CPI, but instead is believed to be a hotspot of streamflow-driven change based on additional information and the fact that high bed shear stress coincided with this hotspot. The proposed network-based dynamic connectivity framework has the potential to place dynamical processes occurring at small scales into a network context to understand how reach-scale changes cascade into network-scale effects, useful for informing the large-scale consequences of local management actions.

  10. 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. PMID:23128230

  11. A power-law approximation for fluvial incision by tools and bed coverage processes

    NASA Astrophysics Data System (ADS)

    Brandon, M. T.; Gasparini, N. M.

    2005-12-01

    The stream-power model is widely used to represent fluvial incision in bedrock channels. The model does not account for the amount of sediment in the channel, which can abrade the channel at low concentrations or armor the channel at high concentrations. Here we use a natural example (Clearwater River, Washington State, USA) and numerical experiments to explore how sediment flux influences bedrock incision at a drainage-wide scale. We have generated numerical landscapes with different uplift patterns using the CHILD numerical model and incision rules that include a tools-and-coverage formulation. We then use regression analysis to fit a power-law function I=K*Am*Sn*, where I is incision rate, S slope, and A drainage area, and K*, m*, and n* are fit parameters. We find that this formulation works very well for the Clearwater and all of our numerical experiments. The function has the same form as the stream-power model, but the parameters are empirically defined (as indicated by the asterisks) and can take on values quite different than those inferred from process-based arguments. The best-fit parameters appear to be constant at the scale of a single drainage, but they vary between drainages depending on the pattern of uplift, and whether or not the landscape has reached steady-state. In all cases, slope-area steepness analysis works well for estimating relative incision rates. Our analysis indicates that, in some cases, m* can be quite low, apparently due to the fact that bed coverage increases with increasing area. We conclude that the power-law formulation provides a good functional representation of fluvial incision, but that there are no universal values for m* and n*. These conclusions have important implications for the size of mountain belts and feedbacks between tectonic uplift and surface processes.

  12. Stratigraphic controls on facies characteristics and petrophysical attributes in fluvial channel sandstones

    SciTech Connect

    Cross, T.A.; Kusumanegara, Y.

    1995-08-01

    Previous studies of fluvial, alluvial fan and lacustrine strata have documented changes in stratigraphic architecture and facies that occur as a function of accommodation. One of the most pervasive change of this type is the degree to which original geomorphic elements, such as bedforms, bars and other macroforms, are preserved. In high accommodation conditions, a greater diversity and greater diversity and greater proportion of original bedforms are preserved in continental strata. The same continental environment will be represented by lower facies diversity, and more amalgamated and cannibalized bedforms under conditions of low accommodation. This study sought to determine whether these predictable changes in facies would be accompanied by changes in porosity and permeability, and whether very subtle changes in facies would have marked changes in porosity and permeability. We also wished to identify how subtle variations in facies would affect flow of hydrocarbons through reservoirs. To this end, we conducted stratigraphic, facies and petrophysical analyses of fluvial channelbelt sandstones and associated floodplain and lacustrine mudstones in an exhumed oil reservoir of Tertiary age in the Uinta basin, Utah (USA). Through measurements, we determined that visual estimates of the intensity of surface oil staining were an accurate proxy measurement of the pore volume, and all pore volumes were fully filled with dead, waxy oil. Three genetic sequences are exposed in quarry highwalls. Contrary to intuition, the most porous and permeable sandstones characteristic of the lowest unit would not make the most efficient reservoirs because permeability variations are so great they would be difficult to sweep effectively. Channelbelt sandstones of the intermediate accommodation have less variation in permeability, and yet retain sufficient porosity and permeability that they would be more efficient reservoirs.

  13. Time and the persistence of alluvium: River engineering, fluvial geomorphology, and mining sediment in California

    NASA Astrophysics Data System (ADS)

    James, Allan

    1999-12-01

    River managers need to understand fluvial systems as they change through time. Many river systems are presently in a state of flux as a result of substantial anthropogenic changes to water and sediment regimes and channel hydraulics. Yet, historical approaches to understanding river systems rarely receive adequate attention because historical methodologies are not conducive to the application of quantitative analysis. While there is limited precision in most historical reconstructions, the information derived from these studies constrains other interpretations and is essential to a full understanding of the behavior of fluvial systems. Geomorphology provides a perspective on river systems in which time — at various scales — is interwoven into practical and theoretical aspects of scientific inquiry. Thus, geomorphology is important to our understanding of not only physical systems but also fundamental concepts of time. This study examines channel morphological changes in the Bear and American basins brought about by two episodes of sedimentation from hydraulic gold mining. The primary event was the production of more than 1 billion m 3 of sediment throughout the northern Sierra Nevada from 1853 to 1884 which caused aggradation in many channels across the Sierra foothills and Sacramento Valley. Assumptions by both engineers and geomorphologists that morphologic responses to this event were ephemeral, that sediment loads have returned to previous levels, and that deposits have stabilized, are not borne out by field and historical data in the Sacramento Valley. A secondary sedimentation event, not previously studied, was the production of at least 24 million m 3 of sediment during a period of licensed mining from 1893 to 1953. This episode of sedimentation has been largely overlooked as a geomorphic, hydrologic, or water quality event. Yet, channel morphologic responses in phase with mining during this period are demonstrated. Systematic changes in stage-discharge relationships reflect channel morphological changes that are relevant to flood risk assessments, stability of engineering structures on floodplains, and geomorphic interpretations.

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

    SciTech Connect

    Lewis, Claudia J; Mcdonald, Eric; Sancho, Carlos; Pena, Jose- Luis

    2008-01-01

    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 {+-} 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.

  15. Fluvial architecture variations linked to changes in accommodation space: Río Chico Formation (Late Paleocene), Golfo San Jorge basin, Argentina

    NASA Astrophysics Data System (ADS)

    Foix, Nicolás; Paredes, José M.; Giacosa, Raúl E.

    2013-08-01

    The Upper Paleocene Río Chico Formation is a 50-180 m thick fluvial succession developed in a passive-margin setting, Golfo San Jorge basin, Central Patagonia, Argentina. A detailed description and interpretation of outcrops was carried out, analyzing exposures from the northern basin margin to the most complete successions at the southern depocenter. The unit is characterized by a regional fluvial system that flowed to the south-east. Five main lithofacies associations were defined: (I) active fluvial channels, with three sub-types: braided, meandering and low-sinuosity, (II) sheet-flood deposits, (III) proximal floodplain (natural levee and crevasse-splay), (IV) distal floodplain, and (V) abandoned channels. Lateral/vertical changes in fluvial architecture of the Río Chico Formation were recognized by variations in preserved thickness, fluvial styles, geometry of fluvial channels, regional paleoflow directions, and channel/floodplain ratios. Close to the northern basin margin, the fluvial succession is 50-60 m thick, composed of braided channels, sheet-flow deposits, and high channel/floodplain ratio. In a basinward direction, the alluvial succession increases to 180 m in thickness, the dominant fluvial styles change to low-sinuosity and meandering channels and channel/floodplain ratio reduces. The fluvial architecture of the Río Chico Formation shows two main depositional trends that resulted from changes in accommodation space across the basin. The interpreted break-point coincides with the underlying Cretaceous basin-boundary, thus the synsedimentary extensional reactivation of the pre-existing tectonic lineament generated differential subsidence, delimiting two different accommodation settings.

  16. 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.

  17. Application of Uav Photogrammetry for Assessment of Fluvial Dynamics of a Montane Stream. Case Study - Roklanský Creek, Šumava Mts., Europe.

    NASA Astrophysics Data System (ADS)

    Langhammer, J.; Miřijovský, J.; Hartvich, F.; Kaiglová, J.

    2014-12-01

    Current progress in hydrology and fluvial geomorphology is largely driven by the newly emerging survey and detection techniques, employing advanced technologies for remote sensing and monitoring of the runoff processes and fluvial dynamics. The contribution demonstrates the potential of the fusion of experimental survey methods for analysis of fluvial dynamics of a montane stream. The UAV photogrammetry, optical granulometry, ground LiDAR scanning and sensor network monitoring were applied as a base for building hydrodynamic model for simulation of fluvial dynamics. The UAV photogrammetry is employed to acquire high precision DTM and especially for quantitative analysis of volumetric changes related to initial flood events. The hexacopter platform has been used to acquire the data for photogrammetric analysis of complex stretch of stream with historically elevated fluvial dynamics. The SfM algorithm was used to extract accurate DTM of the channel and to consequently analyze the volumetric changes after a flood event. The sensor network with automated high frequency water level monitoring was used to derive information on hydrological properties of initial flood event. The digital granulometry enabled to analyze the structure of sedimentary material in floodplain. The terrestrial LiDAR scanning allows construction of very detailed 3D models of selected fluvial forms, enabling deeper insight into the effects of fluvial dynamics and to verify the spatial information acquired using UAS photogrammetry. The results of above mentioned techniques are applied to build hydrodynamic model explaining threshold conditions for initiation of changes in fluvial morphology of the riverbed in relation to known and theoretical flood magnitude. The results achieved in the study enabled us to discuss the synergic potential of coupling the UAV photogrammetry, sensor networks and other high precision survey techniques to enhance significantly our knowledge on the dynamics of fluvial systems.

  18. Fluvial landscapes - human societies interactions during the last 2000 years: the Middle Loire River and its embanking since the Middle Ages (France)

    NASA Astrophysics Data System (ADS)

    Castanet, Cyril; Carcaud, Nathalie

    2015-04-01

    This research deals with the study of fluvial landscapes, heavily and precociously transformed by societies (fluvial anthroposystems). It aims to characterize i), fluvial responses to climate, environmental and anthropogenic changes ii), history of hydraulical constructions relative to rivers iii), history of fluvial origin risks and their management - (Program: AGES Ancient Geomorphological EvolutionS of the Loire River hydrosystem). The Middle Loire River valley in the Val d'Orléans was strongly and precociously occupied, particularly during historical periods. Hydrosedimentary flows are there irregular. The river dykes were built during the Middle Ages (dykes named turcies) and the Modern Period, but ages and localizations of the oldest dykes were not precisely known. A systemic and multi-scaled approach aimed to characterize i), palaeo-hydrographical, -hydrological and -hydraulical evolutions of the Loire River, fluvial risks (palaeo-hazards and -vulnerabilities) and their management. It is based on an integrated approach, in and out archaeological sites: morpho-stratigraphy, sedimentology, geophysics, geochemistry, geomatics, geochronology, archaeology. Spatio-temporal variability of fluvial hazards is characterized. A model of the Loire River fluvial activity is developed: multicentennial scale variability, with higher fluvial activity episodes during the Gallo-Roman period, IX-XIth centuries and LIA. Fluvial patterns changes are indentified. Settlement dynamics and hydraulical constructions of the valley are specified. We establish the ages and localizations of the oldest discovered dikes of the Middle Loire River: after the Late Antiquity and before the end of the Early Middle Ages (2 dated dykes), between Bou and Orléans cities. During historical periods, we suggest 2 main thresholds concerning socio-environmental interactions: the first one during the Early Middle Ages (turcies: small scattered dykes), the second during the Modern Period (levees: high quasi-continuous dykes).

  19. Dispersion of channel-sediment contaminants in distributary fluvial systems: Application to fluvial tephra and radionuclide redistribution following a potential volcanic eruption at Yucca Mountain

    NASA Astrophysics Data System (ADS)

    Pelletier, Jon D.; DeLong, Stephen B.; Cline, Michael L.; Harrington, Charles D.; Keating, Gordon N.

    2008-02-01

    Predicting the fluvial transport and mixing of channel-sediment contaminants is necessary for assessing and mitigating heavy-metal and nuclear-waste contamination in rivers. The dilution-mixing model is widely used for this purpose in tributary channel systems that transport contaminants as bed-material load without significant overbank sedimentation. Here a more general, three-dimensional (3D) contaminant transport numerical model is developed and tested based on bed scour, turbulent mixing of contaminant material with uncontaminated channel-bed sediments, and re-deposition of the mixture by the cumulative effect of many flood events. First, the model is applied to a synthetic alluvial-fan environment downstream from a localized contaminant source in order to illustrate the model behavior. Second, the model is validated against measured tephra concentrations in channels downstream from the Lathrop Wells scoria cone volcano, a localized source of basaltic tephra to downstream channels otherwise comprised of non-basaltic sediments. Third, the model is applied to the problem of predicting the concentration of radionuclide-bound tephra in channels downstream from the proposed nuclear-waste repository at Yucca Mountain, Nevada, in the event of a volcanic eruption through the repository. Contaminated tephra is mobilized from the landscape in this model using threshold criteria for hillslope gradient and channel stream power. Mobilized contaminated tephra is mixed with uncontaminated channel-bed sediments using the contaminant transport model and deposited in channels of the Fortymile Wash alluvial fan where the residents nearest to the proposed repository live. The results of twenty Monte Carlo simulations of eruption fallout and post-eruption redistribution corresponding to a range of wind conditions and eruption magnitudes provide information on the mean and variability of contaminated tephra concentrations to be expected in channels of the Fortymile Wash alluvial fan in the event of an eruption. Mean tephra concentrations are approximately 1% but vary from nearly zero to as high as 26%, reflecting the combined effects of wind direction, eruption magnitude, and dilution of tephra with uncontaminated channel-bed sediments during transport.

  20. Sediment accumulation rates and high-resolution stratigraphy of recent fluvial suspension deposits in various fluvial settings, Morava River catchment area, Czech Republic

    NASA Astrophysics Data System (ADS)

    Sedláček, Jan; Bábek, Ondřej; Kielar, Ondřej

    2016-02-01

    We present a comprehensive study concerning sedimentary processes in fluvial sediment traps within the Morava River catchment area (Czech Republic) involving three dammed reservoirs, four meanders and oxbow lakes, and several natural floodplain sites. The objective of the study was to determine sediment accumulation rates (SAR), estimate erosion rates, calculating these using a combination of the 137Cs method and historical data. Another purpose of this study was to provide insight into changing erosion and accumulation rates over the last century. Extensive water course modifications were carried out in the Morava River catchment area during the twentieth century, which likely affected sedimentation rates along the river course. Other multiproxy stratigraphic methods (X-ray densitometry, magnetic susceptibility, and visible-light reflectance spectrometry) were applied to obtain additional information about sediment infill. Sediment stratigraphy revealed distinct distal-to-proximal patterns, especially in reservoirs. Granulometrically, silts and sandy silts prevailed in sediments. Oxbow lakes and meanders contained larger amounts of clay and organic matter, which is the main difference between them and reservoirs. Pronounced 137Cs peaks were recorded in all studied cores (maximum 377 Bq·kg- 1), thus indicating Chernobyl fallout from 1986 or older events. Calculated sediment accumulation rates were lowest in distal parts of reservoirs (0.13-0.58 cm/y) and floodplains (0.45-0.88 cm/y), moderately high rates were found in proximal parts of reservoirs and oxbow lakes (2.27-4.4 cm/y), and the highest rates in some oxbow lakes located near the river (6-8 cm/y). The frequency of the inundation still can be high in some natural areas as in the Litovelské Pomoraví protected area, whereas the decreasing frequency of the inundation in other modified parts can contribute to a lower sedimentation rate. The local effects such as difference between SARs in oxbow lakes and reservoirs, different grain size distribution in both systems, and high variability in thickness of their proximal and distal parts play a crucial role in the analysis of regional accumulation rates. Local effects are much stronger than regional effects, such as rainfall and land use. Combined with the low resolution of time scales (usually only three datums are available: reservoir construction datum, 137Cs fallout event, and top of sediment), these effects may obscure the general trends of regionally increasing or decreasing net SARs, making the analysis of erosion rates from the sedimentary record an extremely difficult task.

  1. Flood of February 1980 along the Agua Fria River, Maricopa County, Arizona

    USGS Publications Warehouse

    Thomsen, B.W.

    1980-01-01

    The flood of February 20, 1980, along the Agua Fria River below Waddell Dam, Maricopa County, Ariz., was caused by heavy rains during February 13-20. The runoff filled Lake Pleasant and resulted in the largest release--66,600 cubic feet per second--from the reservoir since it was built in 1927; the maximum inflow to the reservoir was about 73,300 cubic feet per second. The area inundated by the releases includes about 28 miles along the channel from the mouth of the Agua Fria River to the Beardsley Canal flume crossing 5 miles downstream from Waddell Dam. The flood of 1980 into Lake Pleasant has a recurrence interval of about 47 years, whereas the flood of record (1919) has a recurrence interval of about 100 years. (USGS)

  2. SEISMIC STUDY OF THE AGUA DE PAU GEOTHERMAL PROSPECT, SAO MIGUEL, AZORES.

    USGS Publications Warehouse

    Dawson, Phillip B.; Rodrigues da Silva, Antonio; Iyer, H.M.; Evans, John R.

    1985-01-01

    A 16 station array was operated over the 200 km**2 central portion of Sao Miguel utilizing 8 permanent Instituto Nacional de Meterologia e Geofisica stations and 8 USGS portable stations. Forty four local events with well constrained solutions and 15 regional events were located. In addition, hundreds of unlocatable seismic events were recorded. The most interesting seismic activity occurred in a swarm on September 6 and 7, 1983 when over 200 events were recorded in a 16 hour period. The seismic activity around Agua de Pau was centered on the east and northeast slopes of the volcano. The data suggest a boiling hydrothermal system beneath the Agua de Pau volcano, consistent with a variety of other data.

  3. Agua Caliente Solar Feasibility and Pre-Development Study Final Report

    SciTech Connect

    Carolyn T. Stewart, Managing Partner; Red Mountain Energy Partners

    2011-04-26

    Evaluation of facility- and commercial-scale solar energy projects on the Agua Caliente Band of Cahuilla Indians Reservation in Palm Springs, CA. The Agua Caliente Band of Cahuilla Indians (ACBCI) conducted a feasibility and pre-development study of potential solar projects on its lands in southern California. As described below, this study as a logical and necessary next step for ACBCI. Support for solar project development in California, provided through the statewide California Solar Initiative (CSI), its Renewable Portfolio Standard and Feed-in Tariff Program, and recently announced Reverse Auction Mechanism, provide unprecedented support and incentives that can be utilized by customers of California's investor-owned utilities. Department of Energy (DOE) Tribal Energy Program funding allowed ACBCI to complete its next logical step to implement its Strategic Energy Plan, consistent with its energy and sustainability goals.

  4. Lower Permian fluvial cyclicity and stratigraphic evolution of the northern margin of Gondwanaland: Warchha Sandstone, Salt Range, Pakistan

    NASA Astrophysics Data System (ADS)

    Ghazi, Shahid; Mountney, Nigel P.; Sharif, Sadaf

    2015-06-01

    During the Lower Permian (Artinskian), fluvial conditions prevailed in what is now the Salt Range of northern Pakistan. Deposits of the Warchha Sandstone are characterised by a range of fluvial facies and architectural elements that together record both the proximal and distal parts of a meandering river system that drained the northern margin of Gondwanaland. Stratigraphic units are arranged into vertically stacked fining-upward cycles represented by thin accumulations of channel-lag deposits at their bases, and sandstone-dominated channel fill and thicker accumulations of overbank mudstone at their tops. Sedimentary cyclicity records fluvial system development on a variety of spatial and temporal scales. Overall, the Warchha Sandstone preserves a series of three to ten vertically stacked fining-upward cycles that form part of a larger-scale, third-order sequence that is itself bounded by regionally extensive and laterally correlatable unconformities that were generated in response to combined tectonic and eustatic changes. The sequence-stratigraphic architecture reflects regional palaeogeographic development of the Salt Range region. The small-scale fluvial cycles originated through autogenic mechanisms, predominantly as a result of repeated channel avulsion processes that occurred concurrently with on-going subsidence and the progressive generation of accommodation. Each erosively based fining-upward fluvial cycle is divided into three parts: a lower part of trough cross-bedded conglomerate and coarse sandstone; a middle part of tabular cross-bedded, ripple cross-laminated and horizontally laminated sandstone; and an upper part of predominantly horizontally laminated and massive mudstone. Overall, the Warchha Sandstone records the progradation of a wedge of non-marine strata into a previously shallow-marine depositional setting. The underlying marine Dandot Formation is terminated by a major unconformity that represents a type-I sequence boundary associated with a regional relative sea-level fall and a significant regression of the Tethyan shoreline. The overlying Warchha Sandstone represents the onset of the subsequent lowstand systems tract in which a northward-flowing meandering river system redistributed clastic detritus derived from a tectonically-active source area (the Aravalli and Malani ranges) that lay to the south. This episode of fluvial sedimentation was terminated by a widespread marine transgression recorded by an abrupt upward transition to estuarine and shallow-marine deposits of the overlying Sardhai Formation. This change marks the transition from lowstand deposits to a transgressive system tract.

  5. Spatio-temporal variability and rates of fluvial bedload transport in steep mountain catchments in western Norway

    NASA Astrophysics Data System (ADS)

    Beylich, Achim A.; Laute, Katja

    2014-05-01

    The timing and rate of fluvial bedload transport are of central importance within sediment budget studies and in many applications in river science and engineering. Bedload transport rates are very difficult to measure and, in many sites, only suspended load and solute data are included in sediment budget studies. During four years (2010 - 2013) detailed field measurements with portable impact sensors as a non-invasive technique for indirectly determining fluvial bedload transport intensity were conducted at several selected channel stretches within two instrumented and supply-limited drainage basin systems (Erdalen and Bødalen) in the steep fjord landscape in western Norway. The selected stream test stretches where impact sensor field measurements were conducted were located (i) downstream of steep channels in headwater areas of the two drainage basin systems Erdalen and Bødalen, (ii) downstream of selected stream channel segments with temporary in-channel storage of bedload material in Erdalen and Bødalen and (iii) at the outlets of the two drainage basin systems Erdalen and Bødalen. The collected impact sensor field data were calibrated with laboratory flume experiments and were combined with field data from continuous discharge monitoring, repeated surveys of channel morphometry and sediment texture, particle tracer measurements, Helley-Smith samplings, underwater videofilming and biofilm analyses. The combination of methods and techniques applied provides detailed insights into the spatio-temporal variability and rates of fluvial bedload transport within Erdalen and Bødalen. Fluvial bedload transport in steep headwater streams is strongly related to sediment delivery from slopes, especially through fluvial transfers in small creeks draining the slope systems and through snow avalanches in spring and debris flows in fall. Channel reaches with temporary in-channel storage of bedload material in the middle parts of the Erdalen and Bødalen drainage basin systems can modify this temporal pattern of fluvial bedload transport. The measured bedload yield in Bødalen is five times higher than the bedload yield in Erdalen which reflects a valley-morphometric determined higher level of slope-channel coupling in Bødalen than in the Erdalen drainage basin system.

  6. Hydrologic characteristics of the Agua Fria National Monument, central Arizona, determined from the reconnaissance study

    USGS Publications Warehouse

    Fleming, John B.

    2005-01-01

    Hydrologic conditions in the newly created Agua Fria National Monument were characterized on the basis of existing hydrologic and geologic information, and streamflow data collected in May 2002. The study results are intended to support the Bureau of Land Management's future water-resource management responsibilities, including quantification of a Federal reserved water right within the monument. This report presents the study results, identifies data deficiencies, and describes specific approaches for consideration in future studies. Within the Agua Fria National Monument, the Agua Fria River flows generally from north to south, traversing almost the entire 23-mile length of the monument. Streamflow has been measured continuously at a site near the northern boundary of the monument since 1940. Streamflow statistics for this site, and streamflow measurements from other sites along the Agua Fria River, indicate that the river is perennial in the northern part of the monument but generally is intermittent in downstream reaches. The principal controls on streamflow along the river within the monument appear to be geology, the occurrence and distribution of alluvium, inflow at the northern boundary and from tributary canyons, precipitation, and evapotranspiration. At present, (2004) there is no consistent surface-water quality monitoring program being implemented for the monument. Ground-water recharge within the monument likely results from surface-water losses and direct infiltration of precipitation. Wells are most numerous in the Cordes Junction and Black Canyon City areas. Only eight wells are within the monument. Ground-water quality data for wells in the monument area consist of specific-conductance values and fluoride concentrations. During the study, ground-water quality data were available for only one well within the monument. No ground-water monitoring program is currently in place for the monument or surrounding areas.

  7. OSL dating of fluvial terraces for incision rate estimation and indication of neotectonic activity in Pamir

    NASA Astrophysics Data System (ADS)

    Fuchs, M. C.; Gloaguen, R.; Krbetschek, M.; Szulc, A.

    2012-04-01

    ThePamir owes its special attraction for geo-scientists to being among Earth's largest intra-continental orogens and to display some of the highest uplift rates as well as to host among the most powerful river systems on the planet. The evolution of the drainage network as a proxy for the landscape's response to tectonic signals provides a powerful tool to study neotectonics. The relation between tectonic forcing and surface response is indicated by structural anomalies (e.g. river-capture, river-reversal or -deflection) and spatial differences of process rates (e.g. incision rates). We combine OSL dating with remote sensing tectonic geomorphology in order to determine the zones of active deformation in the Quaternary. The local drainage system of the study region aligns mainly to the east-west-trending belts of shortening, which results from the ongoing northward propagation of the Indian plate. In contrast the major trunk river, the Panj, is unusual in that it deflects northwards and then doubles back to the southwest, cutting the southern and central Pamir doming and several other major Cenozoic deformation zones. We use fluvial terraces along the deflected north-south orientated part including the doubled back prolongation of the more or less normal orientated Panj. These sediment bodies are used as a geomorphic record to reveal changes in the balance between sediment flux and discharge. Dating these fluvial terraces by OSL provides the burial ages of the sediments indicating periods of sedimentation. The remains of those periods are far from equally distributed and mark the time of local conditions for sedimentation as especially the close neighbourhood of most of the terraces from the two youngest periods demonstrate. Precise measurements of the heights of the dated terraces with respect to the present river level based on relative kinematic GPS quantify the total vertical incision of the river subsequent to the sedimentation and abandonment. Incision rates from about 2 mm/a to more than 11 mm/a are measured. Young fluvial terraces generally provide high incision rates (7 - 11 mm/a), whereas the oldest terraces give incision rates of about 5 mm/a. This likely reflects the averaging effect over much longer period of time including several distinct periods of fast and maybe event-related incision altered by periods of low geomorphologic activity in the sense of no incision, maybe even sedimentation. Further evidence for the important role of neotectonic forcing to surface response processes in Pamir is deduced from remote sensing techniques. Prominent knickpoints do not refer to lithological boundaries and therefore, illustrate a rather composite character of the longitudinal river profile pointing at certain localities of neotectonic activity. Very small valley shape ratios were derived from valley cross-sections orthogonal to the longitudinal profile and demonstrate generally deep valleys relative to their valley floor width. The analysed geomorphological indices (incision rates, longitudinal profile, valley shape ratios) speak for enhanced geomorphological activity after sedimentation (especially of the last terrace generation) driven by local base level changes, which result most likely from feedbacks to neotectonic processes.

  8. Creating High Quality DEMs of Large Scale Fluvial Environments Using Structure-from-Motion

    NASA Astrophysics Data System (ADS)

    Javernick, L. A.; Brasington, J.; Caruso, B. S.; Hicks, M.; Davies, T. R.

    2012-12-01

    During the past decade, advances in survey and sensor technology have generated new opportunities to investigate the structure and dynamics of fluvial systems. Key geomatic technologies include the Global Positioning System (GPS), digital photogrammetry, LiDAR, and terrestrial laser scanning (TLS). The application of such has resulted in a profound increase in the dimensionality of topographic surveys - from cross-sections to distributed 3d point clouds and digital elevation models (DEMs). Each of these technologies have been used successfully to derive high quality DEMs of fluvial environments; however, they often require specialized and expensive equipment, such as a TLS or large format camera, bespoke platforms such as survey aircraft, and consequently make data acquisition prohibitively expensive or highly labour intensive, thus restricting the extent and frequency of surveys. Recently, advances in computer vision and image analysis have led to development of a novel photogrammetric approach that is fully automated and suitable for use with simple compact (non-metric) cameras. In this paper, we evaluate a new photogrammetric method, Structure-from-Motion (SfM), and demonstrate how this can be used to generate DEMs of comparable quality to airborne LiDAR, using consumer grade cameras at low costs. Using the SfM software PhotoScan (version 0.8.5), high quality DEMs were produced for a 1.6 km reach and a 3.3 km reach of the braided Ahuriri River, New Zealand. Photographs used for DEM creation were acquired from a helicopter flying at 600 m and 800 m above ground level using a consumer grade 10.1mega-pixel, non-metric digital camera, resulting in object space resolution imagery of 0.12 m and 0.16 m respectively. Point clouds for the two study reaches were generated using 147 and 224 photographs respectively, and were extracted automatically in an arbitrary coordinate system; RTK-GPS located ground control points (GCPs) were used to define a 3d non-linear transformation to convert the point clouds to the absolute NZTM coordinate system, with average errors of 0.06 m in the horizontal and 0.11 m in the vertical dimensions. The final point clouds extracted had typical point spacings of 0.25 m, well above the metric resolution of airborne LiDAR. To improve data handling, the final point cloud was decimated to point spacings of 0.5 m using a recently developed gridding procedure (Rychkov, Brasington, & Vericat, 2012), and finally converted into a DEM using a Delaunay constrained TIN in ArcGIS. Results reveal SfM's ability to produce high quality terrain products of large scale fluvial environments that can outperform LiDAR, and can potentially compare with TLS. PhotoScan offers a straightforward method to generate, transform, and export DEMs that requires little user knowledge of photogrammetric processes. Further, the affordability and reduced field work offer low budget researchers the ability to produce repeat surveys for in-depth temporal studies. Funding supported by the New Zealand Department of Conservation.

  9. Geomorphic response to agricultural land use in small fluvial systems - The role of landscape connectivity

    NASA Astrophysics Data System (ADS)

    Poeppl, R.; Keiler, M.; Glade, T.; Engage-Geomorphological Systems; Risk Research

    2010-12-01

    Nearly all river catchments are affected directly or indirectly by human actions, e.g. varying agricultural land use or interventions into to river course and flow lead to significant geomorphic changes. The rates of fluvial change are accelerating in many river catchments and public and institutional awareness of these changes and their consequences has grown. This trend leads to an increasing need for a deeper understanding of how the system elements are interrelated (connected) and how fluvial systems respond to human activities. Most of the studies relating to such topics focus on extrinsic (e.g. climatic) factors, although vegetation cover is one of the primary intrinsic factors on sediment yield to a river and even the most susceptible factor for human alterations. Furthermore, nearly all of the published studies are dealing with large rivers, disregarding the much more abundant smaller ones, which in sum do also influence larger rivers. The presented study contributes to gain a deeper understanding of how river systems geomorphologically respond to human activities. The focus in this study is on the importance of hillslope-channel connectivity relationships, as well as on connectivity relationships between the channel reaches in catchments with agricultural land use. Therefore, aerial photograph and airborne laserscan-interpretations were used to create detailed land use and river maps in order to gather current land use and river planform geometry conditions. The land use data was integrated to a GIS-related spatial soil erosion model so as to determine sources of fine sediment from eroding top soil in agricultural areas. Furthermore, a DEM-based multiple-flow model was applied to examine hillslope-channel connectivity relationships. River bed sediment composition, sediment embeddedness and in-channel accumulation of fine sediments were surveyed as potential indicators for geomorphic system response to agricultural land-use, as well as to determine connectivity relationships between the different channel reaches. The study area watersheds of the mixed-load rivers Fugnitz and Kaja are located in the Eastern part of the Bohemian Massif in Austria (Europe). These drainage basins can be morphologically subdivided into two units: The upper and middle reaches exhibit low river gradients, low slope angles (plateau character) and wide open valleys with sides flaring out. The lower reaches show high river gradients, high slope angles, V-shaped valleys, some of them with alluvial fills. In the upper and middle reaches, land-use is prevalently characterized by agriculture with only partially forested zones, whereas the lower reaches are dominated by forests and woodlands. This study area conditions allow comprehensive comparison of the connectivity between several system components. The results highlight that agricultural land use is a major driving factor in altering the sediment regime of fluvial systems, leading to bed sediment fining, especially in areas with high channel-hillslope connectivity. Converging to the lower reaches of the study areas, where minimum agricultural land-use is present, amounts of fine sediments are decreasing continuously because of sediment storage in pools or in the hyporheic zone.

  10. Ground Penetrating Radar Field Studies of Planetary Analog Geologic Settings: Impact Ejecta, Volcanics, and Fluvial Terrains

    NASA Astrophysics Data System (ADS)

    Russell, P. S.; Grant, J. A.; Carter, L. M.; Garry, W.; Williams, K. K.; Morgan, G. A.; Daubar, I.; Bussey, B.

    2012-12-01

    Ground-Penetrating Radar (GPR) data from terrestrial analog environments can help constrain models for evolution of the lunar and martian surfaces, aid in interpretation of orbital SAR data, and help predict what might be encountered in the subsurface during future landed scientific or engineering operations. Results and interpretations presented here from impact ejecta (Barringer Meteorite Crater), volcanic deposits (Northern Arizona cinders overlying lavas, columnar-jointed Columbia River flood basalts, Hawaii lava flows), and terrains influenced by fluvial-related activity (channeled scablands megaflood bar, Mauna Kea glacio-fluvial deposits) focus on defining the radar "fingerprint" of geologic materials and settings that may be analogous to those found on the Moon and Mars. The challenge in using GPR in geologic investigations is the degree to which different geologic features and processes can be uniquely identified and distinguished in the data. Our approach to constraining this is to qualitatively and quantitatively characterize GPR signatures of different geological environments and to compare them with "ground-truth" observations of subsurface exposures immediately adjacent or subjacent to our GPR transects. Several sites were chosen in each field area based on accessibility, visual access to the subsurface, and presence of particular geologic features of interest. The interpreted distribution of blocks in impact ejecta at Meteor Crater, using a 400 MHz antenna (wavelength of 75 cm) is 1.5-3 blocks per m^3 in the upper 1 m (and 0.5-1 blocks per m^3 in the upper two meters), which is close to the in situ measured block distribution of 2-3 blocks larger than 0.25-0.30 m per m^3. This is roughly the detection limit to be expected from the λ/3 resolution approximation of radar wavelength and indicates that the 400 MHz GPR is characterizing the block population in ejecta. While megaflood bar deposits are also reflector-rich, individual reflectors are in general more easily distinguished. At multiple sites, cinders appear smoothly, regularly layered, and allow for excellent GPR penetration. Consequently, the often rough relief of underlying lava flows is discernable, allowing thickness and volume estimates to be made, as well as giving some idea of structure within/on the buried flow. Alternations of massive and clinkery horizons within a'a' flows are detected, as are features representing the interface of overlapping pahoehoe flows (likely due to relatively high relief and fracturing associated with squeeze-ups, etc). Accumulations of gravel, pebbles, and fines derived from lavas and cinders and emplaced by alluvial and mass-wasting processes (along the margins of Apollo Valley, Mauna Kea) appear similar to the pure cinders, as it is likely the same porosity and grain-size characteristics that cause layered GPR reflections. In any case, such layers allow interpretation of how successive events filled in surface relief of the underlying (lava) substrate. GPR data of the interior fill of western Apollo Valley reveals relatively flat reflectors in the along-valley direction and inter-fingering, pinching-out, and dome- and trough-shaped reflectors in the cross-valley direction, indicating accumulation by multiple overlapping lobes coming down the valley, possibly due to multiple fluvial events over time.

  11. Evidences of Paleoearthquakes in Palaeolithic settlements within fluvial sequences of the Tagus Basin (Madrid, Central Spain).

    NASA Astrophysics Data System (ADS)

    Silva, Pablo G.; Rodríguez Pascua, M. A.; Pérez López, R.; Giner Robles, J. L.; Roquero, E.; Tapias, F.; López Recio, M.; Rus, I.; Morin, J.

    2010-05-01

    Multiple evidences of soft-sediment to brittle deformation within the Pleistocene fluvial terraces of the Tagus, Jarama, Tajuña and Manzanares river valleys have been described since the middle 20th Century. Cryoturbation, hydroplastic deformations due to underlying karstic collapses or halokinesis on the substratum of neogene gypsums, and seismic shaking have been proposed to interpret these structures. These deformations are typically concentrated in the +18-20 m terrace levels, and closely linked to well-known Palaeolithic sites, in some cases overlaying and/or affecting true prehistoric settlements (i.e. Arganda, Arriaga and Tafesa sites) within the Jarama and Manzanares valleys. The affected settlements typically display acheulian lithic industry linked to the scavenging of large Pleistocene mammals (i.e. Elephas antiquus). Commonly, deformational structures are concentrated in relatively thin horizons (10-50 cm thick) bracketed by undeformed fluvial sands and gravels. The soft-sediment deformations usually consist on medium to fine sized sands injected and protruded in overlaying flood-plain clayey silts, showing a wide variety of convolutes, injections, sand-dikes, dish and pillar structures, mud volcanoes, faults and folds, some times it is possible to undertake their 3D geometrical analysis due to the exceptional conservation of the structures (Tafesa). Recent geo-archaeological prospecting on the for the Palaeolithic Site of Arriaga (South Madrid City) conducted during the year 2009, let to find out an exceptional horizon of deformation of about 1.20 m thick. It consisted on highly disturbed and pervasively liquefacted sands, which hardly can be attributed to no-seismic processes. The acheulian lithic industry of the Madrid Region have been classically attributed the Late Middle Pleistocene (< 350 kyr BP), but recent OSL dating indicate that the basal horizons of the +18-20 m fluvial terraces hold ages younger than c.a. 120-100 kyr BP in this zone. All the evidences point to the occurrence of concentrated seismic activity during the OIS 5 (Last Interglaciar) interfering early human activity in the zone. Presently, the Tagus Basin is subject to moderate seismic activity with strongest seismic events not exceeding intensity VI MSK (1954 AD), but most of them related to the Jarama, Tajuña and Tagus river valleys, which are bounded by large linear escarpments carved in Miocene gypsums. These escarpments display a wide variety of brittle and ductile deformations, as well as clear geomorphological indicators of late Quaternary tectonic activity. Considering the recent ESI-2007 Scale, the reported structures indicate the occurrence of larger paleoearthquakes during the Middle-Late Pleistocene of at least local intensity VIII. This study has been supported by the DGPH de la Comunidad de Madrid, AUDEMA S.A. (Proyecto Arriaga-2009). This is a contribution of GQM-AEQUA.

  12. Developing an Understanding of Vegetation Change and Fluvial Carbon Fluxes in Semi-Arid Environments

    NASA Astrophysics Data System (ADS)

    Puttock, A. K.; Dungait, J.; Bol, R.; MacLeod, C. J.; Brazier, R.

    2011-12-01

    Dryland environments are estimated to cover around 40% of the global land surface (Okin et al, 2009) and are home to approximately 2.5 billion people (Reynolds et al. 2007). Many of these areas have recently experienced extensive land degradation. One such area and the focus of this project is the semi-arid US Southwest, where degradation over the past 150 years has been characterized by the invasion of woody vegetation into grasslands. Transition from grass to woody vegetation results in a change in ecosystem structure and function (Turnbull et al, 2008). Structural change is typically characterised by an increased heterogeneity of soil and vegetation resources, associated with reduced vegetation coverage and an increased vulnerability to soil erosion and the potential loss of key nutrients to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is sequestered by these environments and the amount of carbon that is lost as the land becomes more degraded. Therefore, understanding these vegetation transitions is significant for sustainable land use and global biogeochemical cycling. This project uses an ecohydrological approach, monitoring natural rainfall-runoff events over six bounded plots with different vegetation coverage. The experiment takes advantage of a natural abundance stable 13C isotope shift from C3 piñon-juniper (Pinus edulis-Juniperus monosperma) mixed stand through a C4 pure-grass (Bouteloua eriopoda) to C3 shrub (Larrea tridentate). Data collected quantify fluvial fluxes of sediment and associated soil organic matter and carbon that is lost from across the grass-to-shrub and grass-to-woodland transition (where change in space is taken to indicate a similar change through time). Results collected during the 2010 and 2011 monsoon seasons will be presented, illustrating that soil and carbon losses are greater as the ecosystem becomes more dominated by woody plants. Additionally this project utilises novel biogeochemical techniques, using stable 13C isotope and lipid biomarker analyses, to trace and partition fluvial soil organic matter and carbon fluxes during these events. Results show that biomarkers specific to individual plant species can be used to define the provenance of carbon, quantifying whether more piñon or juniper-derived carbon is mobilised from the upland plots, or whether more Larrea tridentate carbon is lost when compared to bouteloa eripoda losses in the lowlands. The combined approach of monitoring carbon fluxes and tracing types of carbon shows great promise for improved understanding of carbon dynamics in areas subject to rapid vegetation change. References Okin, G. S., A. J. Parsons, J. Wainwright, J. E. Herrick, B. Bestelmeyer, T., D. C. Peters, and E. L. Fredrickson. 2009. Do Changes in Connectivity Explain Desertification? Bioscience 59:237-244. Reynolds JF, et al. 2007. Global desertification: Building a science for dryland development. Science 316: 847-851. Turnbull, L., J. Wainright, and R. E. Brazier. 2008. A conceptual framework for understanding semi-arid land degradation: ecohydrological interactions across multiple-space and time scales. Ecohydrology 1:23-34.

  13. A consistent magnetic polarity stratigraphy of Plio-Pleistocene fluvial sediments from the Heidelberg Basin (Germany)

    NASA Astrophysics Data System (ADS)

    Scheidt, Stephanie; Hambach, Ulrich; Rolf, Christian

    2014-05-01

    Deep drillings in the Heidelberg Basins provide access to one of the thickest and most complete successions of Quaternary and Upper Pliocene continental sediments in Central-Europe [1]. In absence of any comprehensive chronostratigraphic model, these sediments are so far classified by lithological and hydrogeological criteria. Therefore the age of this sequence is still controversially discussed ([1], [2]). In spite of the fact that fluvial sediments are a fundamental challenge for the application of magnetic polarity stratigraphy we performed a thorough study on four drilling cores (from Heidelberg, Ludwigshafen and nearby Viernheim). Here, we present the results from the analyses of these cores, which yield to a consistent chronostratigraphic framework. The components of natural remanent magnetisation (NRM) were separated by alternating field and thermal demagnetisation techniques and the characteristic remanent magnetisations (ChRM) were isolated by principle component analysis [3]. Due to the coring technique solely inclination data of the ChRM is used for the determination of the magnetic polarity stratigraphy. Rock magnetic proxies were applied to identify the carriers of the remanent magnetisation. The investigations prove the NRM as a stable, largely primary magnetisation acquired shortly after deposition (PDRM). The Matuyama-Gauss boundary is clearly defined by a polarity change in each core, as suggested in previous work [4]. These findings are in good agreement with the biostratigraphic definition of the base of the Quaternary ([5], [6], [7]). The Brunhes-Matuyama boundary could be identified in core Heidelberg UniNord 1 and 2 only. Consequently, the position of the Jaramillo and Olduvai subchron can be inferred from the lithostratigraphy and the development of fluvial facies architecture in the Rhine system. The continuation of the magnetic polarity stratigraphy into the Gilbert chron (Upper Pliocene) allows alternative correlation schemes for the cores Viernheim and Heidelberg. All things considered, the application of magnetic polarity stratigraphy on Pliocene and Pleistocene fluvial sediments from the Heidelberg Basin provides a consistent and independent chronology and opens the perspective for global correlations where other approaches hardly come to results. [1] GABRIEL, G., ELLWANGER, D., HOSELMANN, C. & WEIDENFELLER, M. 2008. Preface: The HeidelbergBasin Drilling Project. E & G (Quaternary Science Journal), 57, 253-260. [2] ELLWANGER, D. & WIELAND-SCHUSTER, U. 2012. Fotodokumentation und Schichtenverzeichnis der Forschungsbohrungen Heidelberg UniNord I und II. LGRB-Informationen, 26, 25-86. [3] KIRSCHVINK, J. L. 1980. The least-squares line and plane and the analysis of palaeomagnetic data. Geophysical Journal, Royal Astronomical Society, 62, 699-718. [4] ROLF, C., HAMBACH, U. & WEIDENFELLER, M. 2008. Rock and palaeomagnetic evidence for the Plio-/Pleistocene palaeoclimatic change recorded in Upper Rhine Graben sediments (Core Ludwigshafen-Parkinsel), Neth. J. Geosci., 87 (1), 41-50. [5] KNIPPING, M. 2008. Early and Middle Pleistocene pollen assemblages of deep core drillings in the northern Upper Rhine Graben, Germany, Neth. J. Geosci., 87(1), 51-65. [6] HEUMANN, G., pers. Comm. [7] HAHNE, J., pers. Comm.

  14. The Atlas of Natural Hazards and Risks of Austria: first results for fluvial and pluvial floods

    NASA Astrophysics Data System (ADS)

    Mergili, Martin; Tader, Andreas; Glade, Thomas; Neuhold, Clemens; Stiefelmeyer, Heinz

    2015-04-01

    Incoherent societal adaptation to natural processes results in significant losses every year. A better knowledge of the spatial and temporal distribution of hazards and risks, and of particular hot spots in a given region or period, is essential for reducing adverse impacts. Commonly, different hazard and risk estimations are performed within individual approaches based on tailor-made concepts. This works well as long as specific cases are considered. The advantage of such a procedure is that each individual hazard and risk is addressed in the best possible manner. The drawback, however, consists in the fact that the results differ significantly in terms of quality and accuracy and therefore cannot be compared. Hence, there is a need to develop a strategy and concept which uses similar data sources of equivalent quality in order to adequately analyze the different natural hazards and risks at broader scales. The present study is aiming to develop such a platform. The project Risk:ATlas focuses on the design of an atlas visualizing the most relevant natural hazards and, in particular, possible consequences for the entire territory of Austria. Available as a web-based tool and as a printed atlas, it is seen as a key tool to improve the basis for risk reduction, risk adaptation and risk transfer. The atlas is founded on those data sets available for the entire territory of Austria at a consistent resolution and quality. A 1 m resolution DEM and the official cadastre and building register represent the core, further data sets are employed according to the requirements for each natural hazard and risk. In this contribution, the methodology and the preliminary results for fluvial and pluvial floods and their consequences to buildings for three selected test areas in different types of landscapes (rural, urban and mountainous) are presented. Flooding depths expected for annualities of 30, 100 and 300 are derived from existing data sets for fluvial floods and are computed using the model FloodArea for pluvial floods. Land cover parameters necessary for flood routing are deduced from the official cadastre. The values exposed to each flood scenario are quantified on the basis of objects. In this study, the focus is on buildings, thus the official building register is employed as a major data source. The same register is used to derive the vulnerability of each building with regard to floods. Combining exposed values and vulnerability, the risk for each building, expressed as the expected damage per unit of time, is derived. Furthermore, a methodology to automatically regionalize the object-based hazards, exposures, vulnerabilities and risks to any spatial unit desired is presented. This enables us (i) to adapt the web-based atlas to different zooming levels and to flexibly react to (ii) the needs of the users of the atlas and (iii) the availability of reference data for validation of the analyses. The next steps will include (1) extending the analyses for fluvial and pluvial floods to the entire territory of Austria, employing advanced computational techniques such as the use of a cluster; (2) deriving hazards, exposures, vulnerabilities and risks related to a variety of other hazardous processes as well as to chains and combinations of processes (multi-hazard); (3) considering the consequences of hazardous processes not only for buildings, but also for infrastructures and even humans; and (4) elaborating future scenarios, based on possible environmental (including climatic) and socio-economic changes.

  15. Relative importance of fluvial and glacial erosion in shaping the Chandra Valley, western Himalaya, India

    NASA Astrophysics Data System (ADS)

    Eugster, P.; Scherler, D.; Thiede, R. C.; Codilean, A.; Strecker, M. R.

    2013-12-01

    In deeply incised, high-elevation orogens, such as the Himalaya, it is challenging to quantify the contribution of glaciers to long-term erosion and exhumation due to vigorous fluvial erosion and mass wasting. This is especially true for the humid sectors of the orogen. In the Himalaya, the majority of studies has been conducted in internal arid sectors of the orogen, where present-day ice coverage is low and glacial landforms and deposits are well preserved. The Chandra Valley of the greater Lahul area (NW-Himalaya), situated between the southern front of the range (bulk precipitation during summer) and the more arid Trans-Himalaya to the north (most precipitation during winter) is sensitive to fluctuations of the Indian Summer Monsoon and the Westerlies. In this region we intend to determine spatial and temporal variations in valley incision through fluvial and glacial erosion on different timescales by combining information obtained from cosmogenic radionuclide (CRN) dating of glacially-carved and striated surfaces, low-temperature thermochronometers, field mapping and morphometric analysis. A prominent feature in the upper Chandra Valley, also the headwater region of the Chenab River, is a large knickpoint in the present-day channel profile of the Chandra/Chenab River at an elevation of ~3900 m asl. This knickpoint spatially coincides with (1) a pronounced change in AFT ages along the course of the valley; (2) the joining of a tributary where one of the largest glaciers in the entire area is found; (3) a significant lithological break; and (4) a steep climatic gradient that accompanies the northward turn of the valley. Further knickpoints were found in tributary valleys of the Chandra Valley at approximately the same elevation of ~3900 m asl. Our field observations and preliminary CRN data suggest extensive glacial coverage of the upper Chandra Valley. Based on field evidence the minimum ice thicknesses for the main trunk glacier in the Chandra Valley must have been at least 700 m above the present-day valley bottom until ~15 ka. Our data confirm previous glacial chronological work in this area that also proposed that deglaciation of the Chandra Valley must have been rapid and accomplished within 15 ka, but additionally shows that the late glacial ice cover in the upper Chandra was more extensive than previously thought and also reached the Spiti Valley. Combining all preliminary results and observations, we hypothesize that glacial carving has been the first-order erosional agent during the Quaternary of all regions in Lahul above an elevation of 4100 m asl. Apatite fission-track ages suggest slower erosional exhumation in the more arid upper Chandra Valley. In this context a former blocking of the valley by the Bara Shigri glacier is possible and glacial processes may have outpaced fluvial erosion in the upper part of the Chandra Valley.

  16. Fluvial sediments a summary of source, transportation, deposition, and measurement of sediment discharge

    USGS Publications Warehouse

    Colby, B.R.

    1963-01-01

    This paper presents a broad but undetailed picture of fluvial sediments in streams, reservoirs, and lakes and includes a discussion of the processes involved in the movement of sediment by flowing water. Sediment is fragmental material that originates from the chemical or physical disintegration of rocks. The disintegration products may have many different shapes and may range in size from large boulders to colloidal particles. In general, they retain about the same mineral composition as the parent rocks. Rock fragments become fluvial sediment when they are entrained in a stream of water. The entrainment may occur as sheet erosion from land surfaces, particularly for the fine particles, or as channel erosion after the surface runoff has accumulated in streams. Fluvial sediments move in streams as bedload (particles moving within a few particle diameters of the streambed) or as suspended sediment in the turbulent flow. The discharge of bedload varies with several factors, which may include particle size and a type of effective shear on the surface of the streambed. The discharge of suspended sediment depends partly on concentration of moving sediment near the streambed and hence on discharge of bedload. However, the concentration of fine sediment near the streambed varies widely, even for equal flows, and, therefore, the discharge of fine sediment normally cannot be computed theoretically. The discharge of suspended sediment also depends on velocity, turbulence, depth of flow, and fall velocity of the particles. In general, the coarse sediment transported by a stream moves intermittently and is discharged at a rate that depends on properties of the flow and of the sediment. If an ample supply of coarse sediment is available at the surface of the streambed, the discharge of the coarse sediment, such as sand, can be roughly computed from properties of the available sediment and of the flow. On the other hand, much of the fine sediment in a stream usually moves nearly continuously at about the velocity of the flow, and even low flows can transport large amounts of fine sediment. Hence, the discharge of fine sediments, being largely dependent on the availability of fine sediment upstream rather than on the properties of the sediment and of the flow at a cross section, can seldom be computed from properties, other than concentrations based directly on samples, that can be observed at the cross section. Sediment particles continually change their positions in the flow; some fall to the streambed, and others are removed from the bed. Sediment deposits form locally or over large areas if the volume rate at which particles settle to the bed exceeds the volume rate at which particles are removed from the bed. In general, large particles are deposited more readily than small particles, whether the point of deposition is behind a rock, on a flood plain, within a stream channel, or at the entrance to a reservoir, a lake, or the ocean. Most samplers used for sediment observations collect a water-sediment mixture from the water surface to within a few tenths of a foot of the streambed. They thus sample most of the suspended sediment, especially if the flow is deep or if the sediment is mostly fine; but they exclude the bedload and some of the suspended sediment in a layer near the streambed where the suspended-sediment concentrations are highest. Measured sediment discharges are usually based on concentrations that are averages of several individual sediment samples for a cross section. If enough average concentrations for a cross section have been determined, the measured sediment discharge can be computed by interpolating sediment concentrations between sampling times. If only occasional samples were collected, an average relation between sediment discharge and flow can be used with a flow-duration curve to compute roughly the average or the total sediment discharges for any periods of time for which the flow-duration c

  17. Late Holocene and present-day fluvial morphodynamics in small catchment areas of Central Germany

    NASA Astrophysics Data System (ADS)

    Englhard, Michael; Damm, Bodo; Frechen, Manfred; Terhorst, Birgit

    2010-05-01

    During the past decades strong runoff events repeatedly occurred in small drainage basins of the European low mountains. In numerous events runoff was connected with erosion and transport of extensive bed load. Runoff events were predominantly triggered by rainstorms, which were limited to the catchment areas. They partly caused severe economic loss. The present study focuses on fluvial morphodynamics in northern Hesse and Lower Saxony. In this area runoff and transport of bed load occurred in small tributary catchment areas of the Fulda, Werra and Oberweser rivers. In general, the small drainage basins are used by agriculture and forestry. Drainage channels are developed as gullies and are incised into solid bedrock, Quaternary hillslope sediments, alluvial fills, and anthropogenic deposits. Vertical incision into the bedrock may amount to 1 meter per event. Furthermore, in single cases sediment discharge amounted to 16.000 m³ in addition to the suspension load. On the base of historical analyses about 50 severe runoff events with a maximum frequency of 10 events during 1965 are recorded during the past 150 years in the study area. Field survey, sedimentological analyses and dating reveal intensive runoff processes since the Neolithic age in a comparable catchment area. In this context potsherds could be dated to the Linear Pottery culture, which were detected in an alluvial cone of the "Rehgraben gully", close to the city of.Kassel. Furthermore, findings of fossil wood were recovered in the same alluvial cone. Radiocarbon dating reveals calibrated ages which are for the most parts younger than AD. In younger sediments we suppose the severe runoff event of 1342. Current studies in the catchment area of the Rehgraben aim to distinguish different processes of the fluvial morphodynamics on a temporal scale and to estimate potential Holocene erosional rates. References Damm, B., 2004. Geschiebe führende und murfähige Wildbäche in Mittelgebirgsräumen. Interpraevent 10/3, Themenbereich VII Wildbach, 61-72. Dreibrodt, S., Lubos, C., Terhorst, B., Damm, B., Bork, H.-R., 2009. Historical Soil Erosion by Water in Germany. A Review. - Quaternary International, doi:10.1016/ j.quatint.2009.06.014. Kreikemeier, A., Damm, B., Böhner, J., Hagedorn, J., 2004. Wildbäche im Fulda- und Oberwesereinzugsgebiet (Nordhessen und Südniedersachsen) - Fallbeispiele und Ansätze zur Abfluss- und Abtragsmodellierung. Zeitschrift für Geomorphologie N.F., Suppl. Vol. 135, 69-94.

  18. The causes and consequences of particle size change in fluvial systems

    NASA Astrophysics Data System (ADS)

    Miller, Kimberly Louise Litwin

    One of the most common features in fluvial environments is the systematic downstream decline in grain size, which is usually attributed to either abrasion - the reduction in sediment size due to attrition of mass - or selective sorting - the size segregation of grains due to their relative transport mobility. Despite the ubiquity of this grain pattern and the extensive research on both of these processes, there remains questions regarding the underlying principles driving abrasion and sorting, as well as the relative contribution of these processes to grain fining. Therefore, a mechanistic understanding of these processes is necessary to observe their direct effect on pattern formation. This dissertation investigates the controls and limits on abrasion and sorting through field studies and laboratory experiments. First, using the well-defined boundary conditions of an alluvial fan, we examine how grain hiding limits gravel sorting by tracking changes in the grain size distribution measured using a novel image-based technique. Further downfan, we compare surface sand fractions measured in the field with those from the lab and show that the gravel-sand sorting profiles are self-similar, suggesting generality in their development. In a second field study, using detailed hand and image-based measurements characterizing size and shape of thousands of grains throughout a watershed, we are able to directly observe the effectiveness of abrasion. We then input these measurements into a simple numerical model to tease apart the contribution of abrasion and sorting to downstream grains size and shape evolution. Finally, we conduct laboratory experiments to isolate the effects of impact energy on abrasion rates and use material properties of the grains to collapse mass loss curves between different lithologies. We measure the grain size distribution of the products of abrasion to show that they are in agreement with expectations from brittle fracture theory. The results from this work indicate that both sorting and abrasion are effective mechanisms in producing downstream grain size patterns. Because grain size exerts a strong control on channel morphology, understanding the controls on particle size change fosters a more complete picture of the fluvial system.

  19. Fluvial engineering works in the river bed of the Middle Loire

    NASA Astrophysics Data System (ADS)

    Nabet, Fouzi

    2010-05-01

    Since 1995, the Loire riverbed has been a field of restoration and maintenance. These interventions took place within the Plan Loire Grandeur Nature and consisted of the following points: the protection of the inhabitants against flooding risks (opening of the secondary channels), the preservation of the ecological assets and the elimination of the sinking of the water line at it's lower level. This research occurred in a specific part of the Loire riverbed, which is situated between Nevers and Orleans (on both banks). We tried by using a geomorphologic analysis to put in evidence the impact of the interventions on the evolution of the secondary channels and dikes. The Geographical Information System (GIS) put in place for the studies sector helps the space analysis by the superposition and the comparison of the different layers of information. This information tool helps creating a database, which can be updated and extended. This way, the managers of this site can easily integrate new thematic (ecological, pedagogical, tourism activity…) and benefit from a precise mapping of the intervention's areas and the impact of the restoration works. The main objective of the PhD is to analyse the functioning of hydrological and fluvial dynamics of the river bed of the Middle Loire, particularly in areas covered by maintenance work. These fluvial engineering works aim to improve flow and transfer of sediment in the river bed. This approach will evaluate the effectiveness of such maintenance work. It is necessary to set up a very fine scale model to quantify sediment transfer between secondary and main channels. The situation of secondary channels is contrasted, but the excessive growth of vegetation in some channels triggers their perennial functioning. The fine scale analysis is based on studies on seasonal and inter-annual evolution of secondary channels. Digital Elevation models (DEM), longitudinal profiles and topographic cross-sections integrated GIS help to quantify precisely erosion and sedimentation, according to the hydrological year. This work should be conducted according to hydrological events on the basis of topographical, bathymetric and sedimentary surveys. Therefore, a limited number of sites has been chosen in collaboration with AITL, DIREN Centre, and Conservatoire des Espaces Naturels. The result of the thesis brings tools to the Loire river management.

  20. Fluvial reservoir characterization using topological descriptors based on spectral analysis of graphs

    NASA Astrophysics Data System (ADS)

    Viseur, Sophie; Chiaberge, Christophe; Rhomer, Jérémy; Audigane, Pascal

    2015-04-01

    Fluvial systems generate highly heterogeneous reservoir. These heterogeneities have major impact on fluid flow behaviors. However, the modelling of such reservoirs is mainly performed in under-constrained contexts as they include complex features, though only sparse and indirect data are available. Stochastic modeling is the common strategy to solve such problems. Multiple 3D models are generated from the available subsurface dataset. The generated models represent a sampling of plausible subsurface structure representations. From this model sampling, statistical analysis on targeted parameters (e.g.: reserve estimations, flow behaviors, etc.) and a posteriori uncertainties are performed to assess risks. However, on one hand, uncertainties may be huge, which requires many models to be generated for scanning the space of possibilities. On the other hand, some computations performed on the generated models are time consuming and cannot, in practice, be applied on all of them. This issue is particularly critical in: 1) geological modeling from outcrop data only, as these data types are generally sparse and mainly distributed in 2D at large scale but they may locally include high-resolution descriptions (e.g.: facies, strata local variability, etc.); 2) CO2 storage studies as many scales of investigations are required, from meter to regional ones, to estimate storage capacities and associated risks. Recent approaches propose to define distances between models to allow sophisticated multivariate statistics to be applied on the space of uncertainties so that only sub-samples, representative of initial set, are investigated for dynamic time-consuming studies. This work focuses on defining distances between models that characterize the topology of the reservoir rock network, i.e. its compactness or connectivity degree. The proposed strategy relies on the study of the reservoir rock skeleton. The skeleton of an object corresponds to its median feature. A skeleton is computed for each reservoir rock geobody and studied through a graph spectral analysis. To achieve this, the skeleton is converted into a graph structure. The spectral analysis applied on this graph structure allows a distance to be defined between pairs of graphs. Therefore, this distance is used as support for clustering analysis to gather models that share the same reservoir rock topology. To show the ability of the defined distances to discriminate different types of reservoir connectivity, a synthetic data set of fluvial models with different geological settings was generated and studied using the proposed approach. The results of the clustering analysis are shown and discussed.

  1. Relative importance of fluvial and glacial erosion in shaping the Chandra Valley, western Himalaya, India

    NASA Astrophysics Data System (ADS)

    Eugster, Patricia; Thiede, Rasmus C.; Scherler, Dirk; Codilean, Alexandru T.; Strecker, Manfred

    2013-04-01

    Although glaciers are often believed to be the principal erosional agents and the cause for increasing the relief of mountain belts, quantifying their contribution to long-term erosion and exhumation is challenging. This is particularly true for the Himalaya, where present-day ice coverage is relatively high, but evidence for extensive glaciations in the past more limited, presumably due to high erosion rates that quickly remove the depositional and geomorphic evidence of glacial impacts. Previous work indicates that the Chandra Valley, in the headwaters of the Chenab River, was strongly glaciated during the Quaternary. In addition, existing thermochronological data suggest a large change in exhumation rates along the valley. This change spatially corresponds to a major fluvial knickpoint, the joining of several large glaciers, a lithological break, and a steep precipitation gradient. In this study we determine spatial and temporal variations in valley incision through fluvial and glacial erosion on different timescales by using cosmogenic radionuclide (CRN) dating of glacially-carved and striated surfaces, various low-temperature thermochronometers, and morphometric analysis. Knickzones are found at elevations of ~3900 m asl along several tributaries of the Chandra/Chenab valleys and other valleys throughout Lahul, potentially indicating a causal relationship with glacial processes. Our field observations and preliminary CRN data suggest major glacial occupation of the Chandra Valley, particularly by the Bara Shigri Glacier, prior to 14 ka. Our data also confirm former CRN measurements in that area. We hypothesize that these observations coincide with the glacially carved surface of the valley, which indicates a minimum altitude of ~4100 m asl for glaciation in the lower Chandra Valley. Here, glacial carving has been the first-order erosional agent during the Quaternary. Furthermore, published AFT cooling ages are young below an elevation of 4100 m asl and increase strongly in the upper part of the valley above this elevation and the observed knickpoints, suggesting slower erosional exhumation in the more arid upper Chandra Valley. The ultimate goal of this study is to better understand the regional erosion pattern within the Chandra Valley, and to possibly determine whether glaciers influenced by local conditions (tectonics, climate), impede or accelerate erosion.

  2. Dynamic Processes of Large Wood and Their Effects on Fluvial Export at the Watershed Scale

    NASA Astrophysics Data System (ADS)

    Seo, J.; Nakamura, F.; Chun, K.

    2008-12-01

    The presence of large wood (LW) has a pronounced impact on the geomorphic and ecological character of river corridors, yet relatively little is known about the patterns and processes at the watershed scale. To understand these patterns we monitored the volumetric input of LW into 131 reservoirs and a suite of watershed characteristics. Of all geomorphic and hydrologic variables tested, watershed area was most important in explaining LW export. LW export per unit watershed area was relatively high in small watersheds, peaked in intermediate-sized watersheds and decreased in large watersheds. To explain these variations, we surveyed the amount of LW with respect to channel morphology in 78 segments (26 segments in each size class) in the Nukabira River, northern Japan, and examined the differences in LW dynamics, including its recruitment, transport, storage, and fragmentation and decay along the spectrum of watershed sizes. We found in small watersheds a larger proportion of LW produced by forest dynamics and hillslope processes was retained due to narrower valley floors and lower stream power. The retained LW pieces may eventually be exported during debris flows. In intermediate-sized watersheds the volume of LW pieces derived from hillslopes decreased substantially with reductions of proportion of channel length bordered by hillslope margins, which potentially deliver large quantities of LW. Because these channels have lower wood piece length to channel width ratios and higher stream power, LW pieces can be transported downstream. During transport, LW pieces are further fragmented and can be more easily transported; and therefore, the fluvial export of LW is maximized in intermediate-sized watersheds. Rivers in large watersheds, where the recruitment of LW is limited by the decreasing hillslope margins, cannot transport LW pieces because of their low stream power and thus LW pieces accumulate at various storage sites. Although these stored LW pieces can be re-floated and transported by subsequent flood events, they may be also combed by obstacles such as log jams and standing trees on floodplains and in secondary channels. Redistribution on these surfaces can be up to decades with eventual decay into fine organic particles resulting in the reduction of fluvial export of LW in larger watersheds. Our findings provide important information for a role of LW pieces in regulating the dynamic character of geomorphic processes and aquatic habitats, and the transfer and residence time of energy for stream-dwelling organisms at the watershed scale.

  3. The River Orontes in Syria and Turkey: Downstream variation of fluvial archives in different crustal blocks

    NASA Astrophysics Data System (ADS)

    Bridgland, David R.; Westaway, Rob; Romieh, Mohammad Abou; Candy, Ian; Daoud, Mohamad; Demir, Tuncer; Galiatsatos, Nikolaos; Schreve, Danielle C.; Seyrek, Ali; Shaw, Andrew D.; White, Tom S.; Whittaker, John

    2012-09-01

    The geomorphology and Quaternary history of the River Orontes in western Syria and south-central Turkey have been studied using a combination of methods: field survey, differential GPS, satellite imagery, analysis of sediments to determine provenance, flow direction and fluvial environment, incorporation of evidence from fossils for both palaeoenvironments and biostratigraphy, uranium-series dating of calcrete cement, reconciliation of Palaeolithic archaeological contents, and uplift modelling based on terrace height distribution. The results underline the contrasting nature of different reaches of the Orontes, in part reflecting different crustal blocks, with different histories of landscape evolution. Upstream from Homs the Orontes has a system of calcreted terraces that form a staircase extending to ~200 m above the river. New U-series dating provides an age constraint within the lower part of the sequence that suggests underestimation of terrace ages in previous reviews. This upper valley is separated from another terraced reach, in the Middle Orontes, by a gorge cut through the Late Miocene-Early Pliocene Homs Basalt. The Middle Orontes terraces have long been recognized as a source of mammalian fossils and Palaeolithic artefacts, particularly from Latamneh, near the downstream end of the reach. This terraced section of the valley ends at a fault scarp, marking the edge of the subsiding Ghab Basin (a segment of the Dead Sea Fault Zone), which has been filled to a depth of ~ 1 km by dominantly lacustrine sediments of Pliocene-Quaternary age. Review of the fauna from Latamneh suggests that its age is 1.2-0.9 Ma, significantly older than previously supposed, and commensurate with less uplift in this reach than both the Upper and Lower Orontes. Two localities near the downstream end of the Ghab have provided molluscan and ostracod assemblages that record somewhat saline environments, perhaps caused by desiccation within the former lacustrine basin, although they include fluvial elements. The Ghab is separated from another subsiding and formerly lacustrine depocentre, the Amik Basin of Hatay Province, Turkey, by a second gorge, implicit of uplift, this time cut through Palaeogene limestone. The NE-SW oriented lowermost reach of the Orontes is again terraced, with a third and most dramatic gorge through the northern edge of the Ziyaret Dağı mountains, which are known to have experienced rapid uplift, probably again enhanced by movement on an active fault. Indeed, a conclusion of the research, in which these various reaches are compared, is that the crust in the Hatay region is significantly more dynamic than that further upstream, where uplift has been less rapid and less continuous.

  4. Exploring controls on valley spacing in higher order fluvial channels with the CHILD Model

    NASA Astrophysics Data System (ADS)

    Han, J.; Gasparini, N. M.; Johnson, J. P.

    2013-12-01

    Across a wide range of landscapes the ratio between the width of a mountain and the distance separating trunk channels exiting the mountain front (generally termed the valley spacing ratio) has been observed to be fairly constant, but the reasons for its uniformity are not well understood. Recent work also suggests that the ratio between the spacing of valleys and the characteristic length, or distance from the divide to where hillslopes transition to fluvial channels, (here termed the characteristic length ratio) is relatively constant in first order channels. We propose that the characteristic length ratio of higher order channels is a primary control on the valley spacing ratio. We explore how these ratios are linked together and the variables that may affect both of these ratios using the CHILD numerical landscape evolution model. Previous studies observed a linear relationship between valley spacing and characteristic length in first order channels, and we find that the relationship remains linear in higher order channels, demonstrating that the competition between hillslope and fluvial processes influences landscape morphology at all scales. Moreover, we also find that the characteristic length ratio for a given order channel is fairly robust and does not appear to be impacted by model initial conditions (such as initial topography) and precipitation patterns (such as orographic precipitation). For a fixed domain in our model, although the characteristic length may vary, the valley spacing ratio remains in the range observed in real landscapes. The ratio of mountain width to valley spacing remains relatively constant because the order of trunk channels varies with the characteristic length. In other words, for a given domain size (or mountain range width), a larger characteristic length can produce lower order trunk channels but with the same spacing value as higher order trunk channels with a smaller characteristic length. This competition between channel order and characteristic length may be one of the reasons why the valley spacing ratio is relatively constant across diverse natural settings. However, our model results also show that initial and boundary conditions may affect the maximum stream order in a domain, even though they do not affect valley spacing. As a result, the valley spacing ratio is more variable than the characteristic length ratio. For example, we find that more pronounced orographic precipitation patterns, or much steeper initial surfaces, can lead to more linear streams, less tributary branching and lower order trunk channels. In this case, the ratio between valley spacing and characteristic length remains the same, whereas the ratio between mountain width and valley spacing increases, but still remains within the observed range in natural landscapes. Finally, DEM analysis of three study areas supports our numerical results.

  5. Modeling the implications of fluvial erosion and bank failures on gully development and growth

    NASA Astrophysics Data System (ADS)

    Istanbulluoglu, E.; Flores, H.; Bras, R.; Tucker, G.

    2003-12-01

    Exploring landscape development due to gully erosion has been an important component in Michael J. Kirkby's scientific career. Gully erosion is most commonly triggered by fluvial erosion due to natural and anthropogenic disturbances, or as a response to changes in climate and tectonic forcing, and base level drop. Field observations suggest that following the development of fluvial incisions, headward growth and widening of many gully systems can be attributed to the instability and collapse of steepened gully walls. Soil saturation, sapping and development of tension cracks contribute to the instability. Recent landscape evolution models treat such mass failures as slope dependent continuous sediment transport processes, sometimes conditioned on a slope threshold or with nonlinear dependence on slope gradient. In this study, first we present a theory for stability analysis of gully head and walls. The theory is based on force balance equation of an assumed planar failure geometry of a steep gully wall, with a potential failure plane dipping to the incised gully bed. We consider development of vertical tension cracks behind the face of the gully head that extend down to the failure plane. In the theory, storm water infiltrates in the tension cracks and generates hydrostatic forces in the vertical crack face, and uplift forces along the failure plane. During storms, water level in the crack is related to steady-state basin hydrology. In our model when tension cracks are either dry or completely filled with runoff water, instability occurs when headcut height exceeds a critical threshold (higher for the dry case). For the case when cracks are partially filled, our theory predicts an inverse relationship between headcut height and drainage area. We used field observations in Colorado and another published data set to test our model. Second, we have implemented this theory in the CHILD landscape evolution model and explored the effects of soil cohesion, erosion thresholds and climate on the tempo of gully development and morphology of eroding gullies. Preliminary results indicate that wider and shallower gullies develop and integrate forming wide valleys, when soil cohesion is small. As soil cohesion increases, gullies become deeper with steeper walls and episodic mass failures occur. Introducing a high runoff erosion threshold produces gentler headcuts. Variations in storm duration and intensity are predicted to have a significant impact on gully morphology.

  6. Latitudinal Controls on Topography: The Role of Precipitation and Fluvial Erosion

    NASA Astrophysics Data System (ADS)

    Sorensen, C.; Yanites, B.

    2014-12-01

    Observations from the North and South American Cordillera show that mean and maximum elevations decrease with increasing latitude. The trend in elevation follows the latitudinal dependence of snowline altitudes. This correlation between elevation and snowline altitude has been the impetus behind the glacial 'buzzsaw' hypothesis, which states that glaciers limit the elevation of mountain peaks. Underlying this hypothesis is an assumption that elevations prior to glaciation were either uniform, randomly distributed, or followed a pattern that is no longer present. However, there may be other factors that are responsible for these patterns, such as latitudinal trends in precipitation. Here, we address this assumption and the necessity of glacial erosion in explaining the latitudinal trend in elevation. We use the CHILD landscape evolution model parameterized by modern precipitation data along a latitudinal gradient in the Andes to predict the topography in the absence of glaciation. Using NCEP/NCAR Reanalysis precipitation data from 1981-2010, we derive storm duration, intensity, and frequency statistics for a series of locations along the Andean orogen. For each location, we run a model using a sequence of storms generated from these statistics. Erodibility and rock-uplift are held constant between the different locations and the models are run until topographic steady-state is achieved. We also present runs exploring the role of a threshold for bedrock detachment in the modeled results. For each run, we track the maximum and mean elevation as well as the time to steady-state. Preliminary results for all cases show that fluvial processes alone are sufficient to account for the latitudinal dependence of topography. For example, landscapes produced with precipitation statistics similar to the dry central Andes are more than an order of magnitude higher than landscapes from the southern, wetter, part of the orogen. Future analysis will use precipitation data from Pliocene climate models as well as link CHILD with a spatially-distributed hydrology model (TopoFlow). Although preliminary, our results potentially challenge the glacial 'buzzsaw' hypothesis and present fluvial erosion as a capable mechanism of generating latitudinal trends in topography.

  7. Human impacts on fluvial systems - A small-catchment case study

    NASA Astrophysics Data System (ADS)

    Pöppl, Ronald E.; Glade, Thomas; Keiler, Margreth

    2010-05-01

    Regulations of nearly two-thirds of the rivers worldwide have considerable influences on fluvial systems. In Austria, nearly any river (or) catchment is affected by humans, e.g. due to changing land-use conditions and river engineering structures. Recent studies of human impacts on rivers show that morphologic channel changes play a major role regarding channelization and leveeing, land-use conversions, dams, mining, urbanization and alterations of natural habitats (ecomorphology). Thus 'natural (fluvial) systems' are scarce and humans are almost always inseparably interwoven with them playing a major role in altering them coincidentally. The main objective of this study is to identify human effects (i.e. different land use conditions and river engineering structures) on river bed sediment composition and to delineate its possible implications for limnic habitats. The study area watersheds of the 'Fugnitz' River (~ 140km²) and the 'Kaja' River (~ 20km²) are located in the Eastern part of the Bohemian Massif in Austria (Europe) and drain into the 'Thaya' River which is the border river to the Czech Republic in the north of Lower Austria. Furthermore the 'Thaya' River is eponymous for the local National Park 'Nationalpark Thayatal'. In order to survey river bed sediment composition and river engineering structures facies mapping techniques, i.e. river bed surface mapping and ecomorphological mapping have been applied. Additionally aerial photograph and airborne laserscan interpretation has been used to create land use maps. These maps have been integrated to a numerical DEM-based spatial model in order to get an impression of the variability of sediment input rates to the river system. It is hypothesized that this variability is primarily caused by different land use conditions. Finally river bed sites affected by river engineering structures have been probed and grain size distributions have been analyzed. With these data sedimentological and ecological/ecomorphological effects of various river engineering structures (i.e. dams, weirs, river bank- and river bed protection works) on river bed sediment composition and on limnic habitats are evaluated. First results reveal that 'land use' is a dominant factor concerning river bed sediment composition and limnic habitat conditions. Further outcomes will be presented on European Geosciences Union General Assembly, 2010.

  8. Interpreting ancient fluvial and deltaic environments on Mars: what can Earth analogs tell us?

    NASA Astrophysics Data System (ADS)

    Gupta, S.; Goddard, K.; Rice, M. S.; Warner, N. H.; Kim, J.; Muller, J.

    2011-12-01

    Reconstructing ancient sedimentary environments on Earth is not a trivial task. Sedimentologists typically use detailed analysis of sedimentary features in rocks together with geometrical stratigraphic relationships and couple this with models of modern systems to reconstruct palaeo-river and deltaic landform features and environments. However, the fidelity of these reconstructions is dependent on good outcrop control and an understanding of how geomorphic elements become frozen in the stratigraphic record. On Mars reconstruction of ancient fluvial and deltaic is on the one hand easier because in numerous examples the planform morphology of such systems preserved in the present-day landscape as relic palaeolandscape features. Such features are very rarely preserved on Earth's landsurface. However, care must be taken in such interpretations. Whilst we can observe point-sourced sedimentary bodies within craters typically emanating from channels that enter the crater, interpreting these as deltaic and determining the type of delta is hazardous. Prior studies have largely focused on establishing geomorphic relations from the large-scale planform bedrock morphology, however, this is dependent on the preservation state. On Earth, we reconstruct ancient deltas by careful analysis of sedimentary bedding patterns as observed in vertical sections. By lateral tracing of bedding we constrain the morphostratigraphy of depositional elements and the surfaces that bound them. The stratigraphy preserved however is not a static state of the river or delta, but instead is a complex of surfaces and sediment bodies that records lateral migration and vertical accumulation of landscape elements. The integration of HiRISE imagery with HiRISE digital terrain models enables Mars sedimentologists and stratigraphers to explore bedding patterns exposed in martian canyons. Whilst we cannot get a handle on the internal sedimentology of these deposits, the analysis of architectural elements and their geometrical disposition enables us to reconstruct the large-scale architecture of inferred martian fluvial and deltaic systems. Understanding this architecture is crucial to informed interpretation of such sedimentary deposits. Here, we analyse the morphology of fluvio-deltaic systems in Eberswalde crater, Mars, using a variety of Earth analogs to aid our analysis. We will examine large scale bedding geometries of the sort visible in spacecraft imagery, and consider how best one can make interpretations.

  9. Inputs and Fluvial Transport of Pharmaceutical Chemicals in An Urban Watershed

    NASA Astrophysics Data System (ADS)

    Foster, G. D.; Shala, L.

    2006-05-01

    Pharmaceuticals and personal care products (PPCPs) are classes of emerging chemical contaminants thought to enter the aquatic environment primarily through wastewater treatment plant (WTP) discharges. As the use of drugs is expected to rise with the aging demographics of the human population and with more river water being diverted to meet potable water demands, the presence of PPCPs in surface water is becoming an issue of public concern. The intent of our study was to quantify potential WTP inputs of PPCPs to rivers in the Wasington, DC (USA) region, and to investigate the fluvial transport of PPCPs in the Anacostia River (AR), the mainstem of a highly contaminated urban watershed in Washington, DC. The approach was to sample WTP water at various stages of treatment, and to measure seasonal concentrations of PPCPs in fluvial transport in the AR. Surface water from the AR was collected through the use of automated samplers during normal flow and storm flow regimes near the head of tide of the AR, just upstream from the confluence of the Northeast (NE) and Northwest (NW) Branches, the two prominent drainages in the watershed. The water samples were filtered to separate river particles from water, and the filtered water was extracted using solid phase extraction (SPE) cartridges. The filters were extracted by sonication in methanol. The SPE and filter extracts were analyzed for a group of widely distributed PPCPs as trimethylsilyl derivatives by using gas chromatography/mass spectrometry. The most frequently detected PPCPs at WTPs included ibuprofen, caffeine, naproxen and triclosan, which ranged from 45 μg/L (caffeine) to 5 μg/L (triclosan) in WTP influent and from 0.08 μg/L (triclosan) to 0.02 μg/L (ibuprofen) in effluent water. Similar PPCPs were detected in both the NE and NW Branches of the AR, but higher concentrations on average were observed in the NE Branch, which receives WTP effluent upstream from the sampling point. The incidence of PPCPs correlated with WTP discharge, but other sources appear to exist based on the occurrence of PPCPs in the NW Branch, which does not receive WTP discharge. Surface water concentrations of the PPCPs were only weakly dependent on the flow regime of the Anacosita River, ranging from 10 to 250 ng/L in AR water. PPCPs are transported in surface waters at parts per trillion concentrations throughout the year, but sources to the AR are not confined to WTPs.

  10. Fluvial diffluence episodes reflected in the Pleistocene tufa deposits of the River Piedra (Iberian Range, NE Spain)

    NASA Astrophysics Data System (ADS)

    Vázquez-Urbez, M.; Pardo, G.; Arenas, C.; Sancho, C.

    2011-01-01

    The Pleistocene deposits of the valley of the River Piedra (NE Spain) are represented by thick tufas with small amounts of detrital material; the development of these deposits correlates with marine isotopic stages 9, 7, 6, and 5. The sedimentary scenario in which they formed mostly corresponded to stepped fluvial systems with barrage-cascade and associated dammed areas separated by low gradient fluvial stretches. Mapping and determining the sedimentology and chronology of these deposits distinguished two main episodes of fluvial diffluence that originated as a result of the temporary blockage of the river — a consequence of the vertical growth of tufa barrages in the main channel. In both episodes, water spilt out toward a secondary course from areas upstream of barrages where the water level surpassed the height of the divide between the main and secondary course. As a consequence, extensive and distinct tufa deposits with very varied facies formed over a gently inclined area toward and, indeed, within the secondary course. The hydrology of this secondary course was episodic, fed only by surface water. The two diffluence episodes detected occurred during MIS 7 and 7-6 and were interrupted by incision events, reflected by detrital deposits at the base of each tufa sedimentation stage in the main channel. Incision, which caused the breakage of the barrages, allowed water to again flow through the main channel. No evidence of diffluence was seen in any younger (MIS 5 to present-day) tufa deposits. The proposed diffluence model might help explain other carbonate fluvial systems in which (1) tufas appear in areas with no permanent water supply, and (2) tufas are absent over extensive areas despite conditions favourable to their formation.

  11. Rates and kinematics of deformations along the eastern Qilian Shan Mountain, NE Tibetan Plateau, constraint by deformed fluvial terraces

    NASA Astrophysics Data System (ADS)

    Hu, X.; Pan, B.; Gao, H.; Hu, Z.; Geng, H.; Cao, B.

    2012-04-01

    We derive slip rates of a series of thrust faults and deforming patterns along the eastern Qilian Shan Mountain by detailed survey of deformed fluvial terraces and OSL dating on the terrace surfaces. The northwest-southeastern treading Qilian Shan Mountain, margining the northeastern Tibetan Plateau, has been uplifting and deforming related to thrust faults bordering the mountain range in the north. By now, the fault thrust rate and how the mountain was uplifted and deformed is poorly documented along the eastern Qilian Shan. In this study, several flights of late Quaternary fluvial terraces along two rivers (Xiying River and Jinta River), sourced from the mountain crest and flowing transecting these thrust faults, are surveyed by differential GPS with the accuracy of lower than 10 centimeters. Meanwhile, the abandonment times of terrace surfaces were dated by OSL dating on the overlying loess above the fluvial deposits. Analysis results of height data show that fluvial terrace surfaces were obviously deformed near these thrust faults, and slip rates of these thrust faults were calculated by deformations and age data. Late Quaternary vertical slip rates of the Huangcheng-Taerzhuang Fault, the KangNingQiao Fault, the NanYing Fault, and the QingDaBan Fault are estimated as 0.15-0.28 mm/a, 0.26-0.47 mm/a, 0.21-0.37 mm/a, and 0.09-0.30 mm/a, respectively. By the geometry of terrace surface height, we find that the hanging-walling planes are slightly warped along these thrust faults, which indicates that the folding amount in the hanging wall is relatively small. This evidence suggests that in the late Quaternary, the deforming of mountain range along the eastern Qilian Shan is accomplished mainly by thrust, and the mountain is uplifted through approximately uniform uplift in hanging-wall planes of the series of thrust faults.

  12. Fluvial incision into bedrock: Insights from morphometric analysis and numerical modeling of gorges incising glacial hanging valleys (Western Alps, France)

    NASA Astrophysics Data System (ADS)

    Valla, Pierre G.; van der Beek, Peter A.; Lague, Dimitri

    2010-06-01

    Bedrock gorges incising glacial hanging valleys potentially allow measurements of fluvial bedrock incision in mountainous relief. Using digital elevation models, topographic maps, and field reconnaissance, we identified and characterized 30 tributary hanging valleys incised by gorges near their confluence with trunk streams in the Romanche watershed, French Western Alps. Longitudinal profiles of these tributaries are all convex and have abrupt knickpoints at the upper limit of oversteepened gorge reaches. We reconstructed initial glacial profiles from glacially polished bedrock knobs surrounding the gorges in order to quantify the amount of fluvial incision and knickpoint retreat. From morphometric analyses, we find that mean channel gradients and widths, as well as knickpoint retreat rates, display a drainage area dependence modulated by bedrock lithology. However, there appears to be no relation between horizontal retreat and vertical downwearing of knickpoints. Assuming a postglacial origin of these gorges, our results imply high postglacial fluvial incision (0.5-15 mm yr-1) and knickpoint retreat (1-200 mm yr-1) rates that are, however, consistent with previous estimates. Numerical modeling was used to test the capacity of different fluvial incision models to predict the inferred evolution of the gorges. Results from simple end-member models suggest transport-limited behavior of the bedrock gorges. A more sophisticated model including dynamic width adjustment and sediment-dependent incision rates predicts present-day channel geometry only if a significant supply of sediment from the gorge sidewalls (˜10 mm yr-1) is triggered by gorge deepening, combined with pronounced inhibition of bedrock incision by sediment transport and deposition.

  13. 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.

  14. Fluvial transport and surface enrichment of arsenic in semi-arid mining regions: examples from the Mojave Desert, California.

    PubMed

    Kim, Christopher S; Stack, David H; Rytuba, James J

    2012-07-01

    As a result of extensive gold and silver mining in the Mojave Desert, southern California, mine wastes and tailings containing highly elevated arsenic (As) concentrations remain exposed at a number of former mining sites. Decades of weathering and erosion have contributed to the mobilization of As-enriched tailings, which now contaminate surrounding communities. Fluvial transport plays an intermittent yet important and relatively undocumented role in the migration and dispersal of As-contaminated mine wastes in semi-arid climates. Assessing the contribution of fluvial systems to tailings mobilization is critical in order to assess the distribution and long-term exposure potential of tailings in a mining-impacted environment. Extensive sampling, chemical analysis, and geospatial mapping of dry streambed (wash) sediments, tailings piles, alluvial fans, and rainwater runoff at multiple mine sites have aided the development of a conceptual model to explain the fluvial migration of mine wastes in semi-arid climates. Intense and episodic precipitation events mobilize mine wastes downstream and downslope as a series of discrete pulses, causing dispersion both down and lateral to washes with exponential decay behavior as distance from the source increases. Accordingly a quantitative model of arsenic concentrations in wash sediments, represented as a series of overlapping exponential power-law decay curves, results in the acceptable reproducibility of observed arsenic concentration patterns. Such a model can be transferable to other abandoned mine lands as a predictive tool for monitoring the fate and transport of arsenic and related contaminants in similar settings. Effective remediation of contaminated mine wastes in a semi-arid environment requires addressing concurrent changes in the amounts of potential tailings released through fluvial processes and the transport capacity of a wash. PMID:22718027

  15. Turbidity in the fluvial Gironde Estuary (southwest France) based on 10-year continuous monitoring: sensitivity to hydrological conditions

    NASA Astrophysics Data System (ADS)

    Jalón-Rojas, I.; Schmidt, S.; Sottolichio, A.

    2015-06-01

    Climate change and human activities impact the volume and timing of freshwater input to estuaries. These modifications in fluvial discharges are expected to influence estuarine suspended sediment dynamics, and in particular the turbidity maximum zone (TMZ). Located in southwest France, the Gironde fluvial-estuarine system has an ideal context to address this issue. It is characterized by a very pronounced TMZ, a decrease in mean annual runoff in the last decade, and it is quite unique in having a long-term and high-frequency monitoring of turbidity. The effect of tide and river flow on turbidity in the fluvial estuary is detailed, focusing on dynamics related to changes in hydrological conditions (river floods, periods of low discharge, interannual changes). Turbidity shows hysteresis loops at different timescales: during river floods and over the transitional period between the installation and expulsion of the TMZ. These hysteresis patterns, that reveal the origin of sediment, locally resuspended or transported from the watershed, may be a tool to evaluate the presence of remained mud. Statistics on turbidity data bound the range of river flow that promotes the upstream migration of TMZ in the fluvial stations. Whereas the duration of the low discharge period mainly determines the TMZ persistence, the freshwater volume during high discharge periods explains the TMZ concentration at the following dry period. The evolution of these two hydrological indicators of TMZ persistence and turbidity level since 1960 confirms the effect of discharge decrease on the intensification of the TMZ in tidal rivers; both provide a tool to evaluate future scenarios.

  16. Lateglacial/early Holocene fluvial reactions of the Jeetzel river (Elbe valley, northern Germany) to abrupt climatic and environmental changes

    NASA Astrophysics Data System (ADS)

    Turner, Falko; Tolksdorf, Johann Friedrich; Viehberg, Finn; Schwalb, Antje; Kaiser, Knut; Bittmann, Felix; von Bramann, Ullrich; Pott, Richard; Staesche, Ulrich; Breest, Klaus; Veil, Stephan

    2013-01-01

    Mechanisms of climatic control on river system development are still only partially known. Palaeohydrological investigations from river valleys often lack a precise chronological control of climatic processes and fluvial dynamics, which is why their specific forces remain unclear. In this multidisciplinary case study from the middle Elbe river valley (northern Germany) multiple dating of sites (palynostratigraphy, radiocarbon- and OSL-dating) and high-resolution analyses of environmental and climatological proxies (pollen, plant macro-remains and ostracods) reveal a continuous record of the environmental and fluvial history from the Lateglacial to the early Holocene. Biostratigraphical correlation to northwest European key sites shows that river system development was partially out of phase with the main climatic shifts. The transition from a braided to an incised channel system predated the main phase of Lateglacial warming (˜14.6 ka BP), and the meandering river did not change its drainage pattern during the cooling of the Younger-Dryas period. Environmental reconstructions suggest that river dynamics were largely affected by vegetation cover, as a vegetation cover consisting of herbs, dwarf-shrubs and a few larger shrubs seems to have developed before the onset of the main Lateglacial warming, and pine forests appear to have persisted in the river valley during the Younger Dryas. In addition, two phases of high fluvial activity and new channel incision during the middle part of the Younger Dryas and during the Boreal were correlated with changes from dry towards wet climatic conditions, as indicated by evident lake level rises. Lateglacial human occupation in the river valley, which is shown by numerous Palaeolithic sites, forming one of the largest settlement areas of that period known in the European Plain, is assigned to the specific fluvial and environmental conditions of the early Allerød.

  17. 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.

  18. Use of Ground Imagery to Study Wood Raft and Ice Dynamics in Fluvial Systems: Potential and Challenges.

    NASA Astrophysics Data System (ADS)

    Benacchio, V.; Piegay, H.; Buffin-Belanger, T. K.; Vaudor, L.; Michel, K.

    2014-12-01

    Automatic cameras allow acquisition of large amounts of information at high resolution in both temporal and spatial dimensions, with a roughly close range. Recently, ground cameras have been used to study the morphological evolution of fluvial environments (e.g. bank erosion, bar mobility, braided pattern changes) or to quantify components of fluvial dynamics (e.g. flow velocity, wood transport or river ice development). As the amount of information increases, automation of the data processing becomes essential, but many challenges arise to improve features detection, taking into account light contrasts, shadow and reflection, or to calculate surfaces and volumes from image orthorectification. This study illustrates the high potential of ground cameras to observe and quantify rapid, stochastic or complex events in fluvial systems and the numerous challenges we have to face. In order to automatically monitor such key fluvial processes, two ground cameras were installed. The first one was placed on the Genissiat dam (Rhône River, France) focusing on the reservoir where pieces of wood are trapped, creating a large raft. The objective is to survey wood raft area over time as a surrogate of the basin wood production. The second camera was installed along the St Jean River (Gaspesia, Québec) focusing on a pool section. The objective here is to characterize the evolution of ice cover, in terms of growing rate and ice types. The snowy environment is particularly challenging because of brightness or fairly homogeneous radiometric conditions amongst ice types. In both cases, remote sensing technics, especially feature based classification are used. Radiometric and texture indexes are used to discriminate both wood and water and ice types.

  19. Facies and sequence stratigraphic modeling of a Upper Pliocene-Lower Pleistocene fluvial succession (Valdelsa Basin, central Italy)

    NASA Astrophysics Data System (ADS)

    Benvenuti, Marco; Del Conte, Sara

    2013-08-01

    This paper illustrates the results of sedimentologic and stratigraphic analyses of the upper Piacenzian-Gelasian fluvial succession exposed in the Neogene-Quaternary Valdelsa Basin (central Italy). The succession shows a cyclothemic stacking of gravelly, sandy and muddy lithofacies organized into four monogenic facies associations (A-D). These record depositional environments ranging from braided to low-sinuosity river channels to flood basins. Associations A-D attest to lowstand (A-B), transgressive and high-stand (C-D) depositions in a full cycle of base-level variations. In each association, internal erosional surfaces separate early transgressive association C from the late lowstand association B. The systematic B/C channel scouring is interpreted as the result of a high water/sediment discharge ratio determined by a decrease of coarse-grained sediment supply to the fluvial systems during rise of base level. This erosive surface is conceptually analogous to the ravinement surface sculpted by wave erosion during the transgressive, landward migration of a shoreface. The late transgressive and highstand mud-dominated association D records the flood basin, a depositional environment indicative of a high base level which transformed a former channel belt in a plain dominated by fine-grained sediment settling, bio- and pedoturbation. The studied succession records rhythmic variations of base level and sediment supply to the fluvial systems, in turn regulated by different-rank relative fluctuations of Piacenzian sea level. In this perspective, concepts of sequence stratigraphy and facies analysis are exploited for producing a reliable fluvial sequence stratigraphic model.

  20. Fluvial trace fossils in the Middle Siwalik (Sarmatian-Pontian) of Darjeeling Himalayas, India

    NASA Astrophysics Data System (ADS)

    Chakraborty, Abhijit; Hasiotis, Stephen T.; Ghosh, Bhaskar; Bhattacharya, Harendra Nath

    2013-08-01

    Trace fossils that record animal and plant activity are described for the first time from the Middle Siwalik, Neogene deposits of Darjeeling Himalaya. Sedimentary facies association attests to a channel-interchannel floodplain fluviatile setting. The intimate association of the burrows with phytoliths, rhizoliths, leaf compressions and coal lenses suggest that the tracemakers dominated a floodplain habitat. Point bar deposits host a low diversity Planolites-Naktodemasis-Macanopsis-Cylindricum equilibrium ichnocoenosis in the heterolithic fine sandstone-siltstone-shale facies that alternates with dense, monospecific colonization of Planolites as opportunistic pioneers relocating under stressed condition. Interlayered floodplain deposits in the fluvial successions preserve enigmatic large diameter, vertical tubes within thin to thick-bedded, dark silty shale facies. These tubes bear mixed characters assignable to both crayfish burrows and large-diameter rhizoliths. Further work on these tubes is necessary to make more accurate interpretations of those structures. Shallow to moderate burrow depths; intermittent, short-lived colonization events and preservation of rhizoliths and rhizohalos under fluctuating moisture content indicate short-term fluctuations of a relatively high water table (close to the paleosurface) in an imperfectly drained proximal floodplain setting. Ichnotaxa distribution and their inferred ethology provide significant faunal data that may put constraints on the reconstruction of Middle Siwalik depositional environment.

  1. Self-similarity and multifractality of fluvial erosion topography: 2. Scaling properties

    NASA Astrophysics Data System (ADS)

    Veneziano, Daniele; Niemann, Jeffrey D.

    2000-07-01

    In a companion paper [Veneziano and Niemann, this issue] the authors have proposed self-similarity and multifractality conditions for fluvial erosion topography within basins and have shown that topographic surfaces with this property can evolve from a broad class of dynamic models. Here we use the same self-similarity and multifractality conditions to derive geomorphological scaling laws of hydrologic interest. We find that several existing relations should be modified, as they were obtained using definitions of the quantities involved or measurement techniques that are inappropriate under self-similarity. These relations include Hack's law, the power law decay of the distributions of contributing area and main channel length, the scaling of channel slope with contributing area, and the self-similarity condition for river courses. Most results are further generalized by replacing main stream flow length and drainage area with generic measures of basin size. The relations we obtain among properly measured topographic variables have simple universal exponents. For example, the exponent of Hack's law is 0.5, the exponent of the distribution of contributing area is -0.5, and the exponent of the distribution of main stream length is -1.0. We also suggest a stochastic condition of drainage network self-similarity that incorporates topological as well as geometric and hydrologic features and a reformulation of Horton's laws using drained area rather than stream order.

  2. Increasing the scope of riverine ecology with state-of-the-art fluvial remote sensing (Invited)

    NASA Astrophysics Data System (ADS)

    Torgersen, C.

    2009-12-01

    Remote sensing is literally changing the way ecologists see rivers and streams and the organisms that live within them. Predominantly site-specific, spatially limited views of lotic environments that were so common in the past are evolving rapidly into high-resolution, geographically extensive remotely sensed surveys of physical and biological characteristics. This more rigorous, spatially explicit approach to pattern detection will make it possible to (1) determine with more precision the initial ecological conditions of rivers and associated biota, and (2) monitor the effects and, ultimately, the success, of ecosystem restoration. The broad array of techniques described in this review of the “state of the art” in fluvial remote sensing illustrate that increasing the geographic extent and resolution of our perception through technical means amplifies the power and flexibility of studies to evaluate ecological patterns at multiple scales. Such approaches aim to align data collection and analysis with the innate process of pattern detection in humans and, thus, offer a more complete view that better reflects ecologists’ understanding of heterogeneity, context, and scale in stream ecosystems. Changes brought about by remote sensing in the way studies are designed and conducted will yield great potential for creativity and new discoveries in riverine ecology.

  3. Monitoring of fluvial transport in small upland catchments - methods and preliminary results

    NASA Astrophysics Data System (ADS)

    Janicki, Grzegorz; Rodzik, Jan; Chabudzi?ski, ?ukasz; Franczak, ?ukasz; Si?uch, Marcin; St?pniewski, Krzysztof; Dyer, Jamie L.; Ko?odziej, Grzegorz; Maciejewska, Ewa

    2014-06-01

    In April 2011 a study was initiated, financed from resources of the Polish National Science Centre, entitled: Rainstorm prediction and mathematic modelling of their environmental and social-economical effects (No. NN/306571640). The study, implemented by a Polish-American team, covers meteorological research, including: (1) monitoring of single cell storms developing in various synoptic situations, (2) detection of their movement courses, and (3) estimation of parameters of their rain field. Empirical studies, including hydrological and geomorphological measurements, are conducted in objects researched thoroughly in physiographic terms (experimental catchments) in the Lublin region (SE Poland), distinguished by high frequency of occurrence of the events described. For comparative purposes, studies are also carried out on selected model areas in the lower course of the Mississippi River valley (USA), in a region with high frequency of summer rainstorms. For detailed studies on sediment transport processes during rainstorm events, catchments of low hydrological rank and their sub-catchments in a cascade system were selected. For the basic, relatively uniform geomorpho logical units distinguished this way, erosion and deposition balance of material transported was determined. The aim of work was to determine influence of weather condition on fluvial transport rate in small catchment with low hydrological order

  4. Sensitivity of fluvial sediment source apportionment to mixing model assumptions: A Bayesian model comparison

    NASA Astrophysics Data System (ADS)

    Cooper, Richard J.; Krueger, Tobias; Hiscock, Kevin M.; Rawlins, Barry G.

    2014-11-01

    Mixing models have become increasingly common tools for apportioning fluvial sediment load to various sediment sources across catchments using a wide variety of Bayesian and frequentist modeling approaches. In this study, we demonstrate how different model setups can impact upon resulting source apportionment estimates in a Bayesian framework via a one-factor-at-a-time (OFAT) sensitivity analysis. We formulate 13 versions of a mixing model, each with different error assumptions and model structural choices, and apply them to sediment geochemistry data from the River Blackwater, Norfolk, UK, to apportion suspended particulate matter (SPM) contributions from three sources (arable topsoils, road verges, and subsurface material) under base flow conditions between August 2012 and August 2013. Whilst all 13 models estimate subsurface sources to be the largest contributor of SPM (median ˜76%), comparison of apportionment estimates reveal varying degrees of sensitivity to changing priors, inclusion of covariance terms, incorporation of time-variant distributions, and methods of proportion characterization. We also demonstrate differences in apportionment results between a full and an empirical Bayesian setup, and between a Bayesian and a frequentist optimization approach. This OFAT sensitivity analysis reveals that mixing model structural choices and error assumptions can significantly impact upon sediment source apportionment results, with estimated median contributions in this study varying by up to 21% between model versions. Users of mixing models are therefore strongly advised to carefully consider and justify their choice of model structure prior to conducting sediment source apportionment investigations.

  5. Mechanisms and timescales of fluvial activity at Mojave and other young Martian craters

    NASA Astrophysics Data System (ADS)

    Goddard, Kate; Warner, Nicholas H.; Gupta, Sanjeev; Kim, Jung-Rack

    2014-03-01

    Mojave Crater, and five other relatively young Late Hesperian to Amazonian-age Martian craters exhibit channelized alluvial fans that are sourced from bedrock-eroded catchments. These catchments emerge from the crests of sloping surfaces, suggesting a formation mechanism that involved precipitation. The evidence for fluvial activity at all six craters is restricted to their interiors and the immediate surrounding regions. Detailed mapping at Mojave reveals the highest density of channels, catchments and fans interior to the crater. Similar landforms are identified outside of the crater, but not beyond ~200 km from the rim. Irregular pits on the floor of Mojave, interpreted as degassing structures from hot impact melt, directly superpose several fan surfaces, and partly destroy the fan toes. This suggests that sediment was mobilized immediately after crater formation, while the crater was still hot. Based on the patterns and timing of channel-fan development at all six craters we favor several hypotheses for the precipitation mechanism: (1) snowfall and melt on young, hot impact craters, (2) impact plume precipitation, and (3) degassing of volatiles from impact melt terrain. Scenario (1) suggests a different global or regional climate relative to modern conditions, requiring equatorial and midlatitude snowfall accumulation. Scenarios (2) and (3) do not necessarily require unique climate conditions, as water may have been mobilized from the target or the impactor.

  6. Spatial Coupling Among Landslides, Geological Structures, Cataclinal Slopes, and Fluvial Knick Zones in Nepal Himalayas

    NASA Astrophysics Data System (ADS)

    Ojha, T. P.; DeCelles, P. G.

    2014-12-01

    This work aims to identify potential landslide hazard zones in the event of heavy precipitation and seismic activity by examining spatial relationships among existing landslides, earthquake epicenters, fault zones, cataclinal (dip) slopes, anaclinal (escarp) slopes, and river steepness index in the Nepal Himalaya. In order to understand this relationship we have mapped existing landslides on Google Earth images and ESRI base maps, assembled high-resolution digital topographic data by digitizing Nepal Government published topographic maps, and gathered geological data from detailed field mapping and compilation of published geological maps. Slope angle and aspect, and dip direction and angle were extracted from GIS-based digital topographical and geological datasets to develop the new slope maps with cataclinal (dip) and anaclinal (escarp) slope distributions. Longitudinal river profiles were also extracted from high resolution DEM's derived from manually digitized contours. The slope maps with cataclinal and anaclinal slope distributions, earthquake epicenters, major geological structures, longitudinal river profiles, and landslide inventories were visualized in ESRI ArcMap 10.2 to examine the spatial correlation among landslides, fault zones, cataclinal slopes and river steepness index. We have found that landslides are spatially correlated with cataclinal slopes and fluvial knick zones with high steepness index in certain thrust boundaries. The main finding of this work is that the topographic slope threshold alone is a crude measure of landslide susceptibility. The analysis of slope using the geometric relationship among topography and geological bedding is crucial for determining landslide susceptibility in the Himalayan region.

  7. Ice jam-caused fluvial gullies and scour holes on northern river flood plains

    NASA Astrophysics Data System (ADS)

    Smith, Derald G.; Pearce, Cheryl M.

    2002-01-01

    Two anomalous fluvial landforms, gullies and scour holes, eroded into flood plains bordering meandering and braiding river channels have not been previously reported. We observed these features along the Milk River in southern Alberta, Canada, and northern Montana, USA, which has a history of frequent (50% probability of recurrence) and high-magnitude (12% probability of recurrence greater than bankfull) ice jam floods. Gullies have palmate and narrow linear shapes with open-ends downvalley and measure up to 208 m long×139 m wide×3.5 m deep (below bankfull). Channel ice jams reroute river water across meander lobes and cause headward gully erosion where flow returns to the main channel. Erosion of the most recent gully was observed during the record 1996 ice breakup flood and ice jams. Scour holes (bowl-shaped, closed depressions), eroded by water vortices beneath and between grounded ice jam blocks, measure up to 91 m long×22 m wide×4.5 m deep. Ice jam-caused gullies may be precursors to the formation of U-shaped oxbow lakes and multiple channels, common in many northern rivers.

  8. An environmental model of fluvial tufas in the monsoonal tropics, Barkly karst, northern Australia

    NASA Astrophysics Data System (ADS)

    Carthew, K. D.; Taylor, M. P.; Drysdale, R. N.

    2006-01-01

    Spring-fed streams that deposit tufa (ambient temperature freshwater calcium carbonate deposits) in the tropics of northern Australia are influenced strongly by perennially warm water temperatures, high evaporation rates, and monsoon driven high-magnitude floods. This paper presents an environmental model that will aid interpretation of fossil fluvial tufas throughout monsoonal Australia. In the Barkly karst, northern Australia, tufas form in dam, cascade and pool/waterhole geomorphic environments. Each environment is represented in the morphostratigraphical record by a specific combination of tufa geomorphic units and facies associations. A diverse array of tufa facies is present, including microphytic, larval, calcite raft, macrophytic and allochthonous types. Preservation of particular Barkly karst tufa facies is thought to reflect the strength of monsoonal floods. A strong monsoon is represented by an abundance of flood indicators such as the allochthonous phytoclastic, lithoclastic and intraclastic tufa facies. Conversely, evidence of weak monsoons or a prolonged absence of floods may include oncoids, calcite rafts and thick accumulations of fine carbonate sediments. The history of the Australian monsoon is not fully understood. However, fossil tufa deposits, which record terrestrial climate information, have been preserved throughout northern Australia and hold great potential for reconstructing the region's climate history. Fossil tufa sequences at two Barkly karst sites have been interpreted using the new model. It can be applied to other Barkly karst fossil tufas as well as those in similar environments elsewhere in the world.

  9. New microbioassays based on biomarkers are more sensitive to fluvial water micropollution than standard testing methods.

    PubMed

    Esteban, S; Fernández Rodríguez, J; Díaz López, G; Nuñez, M; Valcárcel, Y; Catalá, M

    2013-07-01

    Recent investigations suggest that, despite lack of lethality in validated bioassays, micropollutants in surface waters could induce sublethal toxicity in sensitive taxa, jeopardizing their biological performance and eventually leading to populations' extinction. A broader array of testing species, the miniaturization of bioassays and the development of reliable biomarkers of damage are sought in order to improve ecological relevance and cost efficiency of environmental monitoring. Our aim is to assess the different sensitivity of validated bioassays and new approaches using biomarkers as sensitive endpoints of toxicity in spores of Polystichum setiferum and Danio rerio embryos. Six water samples were collected in Tagus basin in summer and winter. Samples tested induce no acute toxicity in validated methods (algae growth inhibition and daphnia mobility inhibition). Summer water samples induced acute membrane damage (lipid peroxidation) in Danio rerio embryos and hormetic increases in fern spore mitochondrial activity. One of the samples dramatically reduced mitochondrial activity indicating severe acute sublethal phytotoxicity. All the winter samples induced significant decreases in fern spore mitochondrial activity and membrane damage increases in Danio rerio embryo. Furthermore, three samples induced lethal phytotoxicity in fern spores. We conclude that the new microbioassays show a better sensitivity to fluvial water micropollution and confirm the necessity to test critical life stages such as development and provide cost-efficient methods for environmental monitoring. PMID:23618774

  10. High fluvial export of dissolved organic nitrogen from a peatland catchment with elevated inorganic nitrogen deposition.

    PubMed

    Edokpa, D A; Evans, M G; Rothwell, J J

    2015-11-01

    This study investigates seasonal concentrations and fluxes of nitrogen (N) species under stormflow and baseflow conditions in the peat dominated Kinder River catchment, south Pennines, UK. This upland region has experienced decades of high atmospheric inorganic N deposition. Water samples were collected fortnightly over one year, in combination with high resolution stormflow sampling and discharge monitoring. The results reveal that dissolved organic nitrogen (DON) constitutes ~54% of the estimated annual total dissolved nitrogen (TDN) flux (14.3 kg N ha(-1) yr(-1)). DON cycling in the catchment is influenced by hydrological and biological controls, with greater concentrations under summer stormflow conditions. Dissolved organic carbon (DOC) and DON are closely coupled, with positive correlations observed during spring, summer and autumn stormflow conditions. A low annual mean DOC:DON ratio (<25) and elevated dissolved inorganic N concentrations (up to 63μmoll(-1) in summer) suggest that the Kinder catchment is at an advanced stage of N saturation. This study reveals that DON is a significant component of TDN in peatland fluvial systems that receive high atmospheric inputs of inorganic N. PMID:26119385

  11. Single and mixture effects of pesticides and a degradation product on fluvial biofilms.

    PubMed

    Tiam, Sandra Kim; Libert, Xavier; Morin, Soizic; Gonzalez, Patrice; Feurtet-Mazel, Agnès; Mazzella, Nicolas

    2014-06-01

    The Morcille River located in the Beaujolais vineyard area (Eastern France) is subjected to strong vine-growing pressure leading to the contamination by a range of herbicides and fungicides of the surrounding freshwater environment. Particularly high concentrations of norflurazon, desmethyl norflurazon and tebuconazole were recorded in spring 2010 at the downstream site of the river. Despite their occurrence in rivers, scarce toxicity data are available for these products, in particular in the case of desmethyl norflurazon (main norflurazon degradation product). Furthermore, the toxicity data are generally available only for single compounds and are issued from single species toxicity tests, leading to a lack of ecological relevance. Consequently, this study was undertaken to evaluate the toxic effects of norflurazon, desmethyl norflurazon and tebuconazole singly and in a ternary mixture on fluvial biofilm. Toxicity tests were performed in microplates for 48 h. Photosynthetic endpoints were measured using pulse amplitude-modulated fluorometry; diatom densities and taxonomic composition were determined. After 48 h of exposure, significant effects on optimal quantum yield (F v/F m) for desmethyl norflurazon and mixture were observed. PMID:24549942

  12. Stream classification using hierarchical artificial neural networks: A fluvial hazard management tool

    NASA Astrophysics Data System (ADS)

    Besaw, Lance E.; Rizzo, Donna M.; Kline, Michael; Underwood, Kristen L.; Doris, Jeffrey J.; Morrissey, Leslie A.; Pelletier, Keith

    2009-06-01

    SummaryWatershed managers and planners have long sought decision-making tools for forecasting changes in stream-channels over large spatial and temporal scales. In this research, we apply non-parametric, clustering and classification artificial neural networks to assimilate large amounts of disparate data types for use in fluvial hazard management decision-making. Two types of artificial neural networks (a counterpropagation algorithm and a Kohonen self-organizing map) are used in hierarchy to predict reach-scale stream geomorphic condition, inherent vulnerability and sensitivity to adjustments using expert knowledge in combination with a variety of geomorphic assessment field data. Seven hundred and eighty-nine Vermont stream reaches (+7500 km) have been assessed by the Vermont Agency of Natural Resources' geomorphic assessment protocols, and are used in the development of this work. More than 85% of the reach-scale stream geomorphic condition and inherent vulnerability predictions match expert evaluations. The method's usefulness as a QA/QC tool is discussed. The Kohonen self-organizing map clusters the 789 reaches into groupings of stream sensitivity (or instability). By adjusting the weight of input variables, experts can fine-tune the classification system to better understand and document similarities/differences among expert opinions. The use of artificial neural networks allows for an adaptive watershed management approach, does not require the development of site-specific, physics-based, stream models (i.e., is data-driven), and provides a standardized approach for classifying river network sensitivity in various contexts.

  13. Basic principles and ecological consequences of changing water regimes on nitrogen cycling in fluvial systems.

    PubMed

    Pinay, Gilles; Clément, Jean Christophe; Naiman, Robert J

    2002-10-01

    Understanding the environmental consequences of changing water regimes is a daunting challenge for both resource managers and ecologists. Balancing human demands for fresh water with the needs of the environment for water in appropriate amounts and at the appropriate times are shaping the ways by which this natural resource will be used in the future. Based on past decisions that have rendered many freshwater resources unsuitable for use, we argue that river systems have a fundamental need for appropriate amounts and timing of water to maintain their biophysical integrity. Biophysical integrity is fundamental for the formulation of future sustainable management strategies. This article addresses three basic ecological principles driving the biogeochemical cycle of nitrogen in river systems. These are (1) how the mode of nitrogen delivery affects river ecosystem functioning, (2) how increasing contact between water and soil or sediment increases nitrogen retention and processing, and (3) the role of floods and droughts as important natural events that strongly influence pathways of nitrogen cycling in fluvial systems. New challenges related to the cumulative impact of water regime change, the scale of appraisal of these impacts, and the determination of the impacts due to natural and human changes are discussed. It is suggested that cost of long-term and long-distance cumulative impacts of hydrological changes should be evaluated against short-term economic benefits to determine the real environmental costs. PMID:12481915

  14. Plant biodiversity effects in reducing fluvial erosion are limited to low species richness.

    PubMed

    Allen, Daniel C; Cardinale, Bradley J; Wynn-Thompson, Theresa

    2016-01-01

    It has been proposed that plant biodiversity may increase the erosion resistance of soils, yet direct evidence for any such relationship is lacking. We conducted a mesocosm experiment with eight species of riparian herbaceous plants, and found evidence that plant biodiversity significantly reduced fluvial erosion rates, with the eight-species polyculture decreasing erosion by 23% relative to monocultures. Species richness effects were largest at low levels of species richness, with little increase between four and eight species. Our results suggest that plant biodiversity reduced erosion rates indirectly through positive effects on root length and number of root tips, and that interactions between legumes and non-legumes were particularly important in producing biodiversity effects. Presumably, legumes increased root production of non-legumes by increasing soil nitrogen availability due to their ability to fix atmospheric nitrogen. Our data suggest that a restoration project using species from different functional groups might provide the best insurance to maintain long-term erosion resistance. PMID:27008770

  15. Fluvial transitions and paleogeography in upper part of Maroon Formation (Pennsylvanian and Permian), northwestern Colorado

    SciTech Connect

    Johnson, S.Y.

    1986-08-01

    Six detailed lateral profiles (as much as 7 m thick and 50 m long) of fluvial channel sandstone bodies were measured at different locations in the northern part of the Eagle basin, northwestern Colorado. Contrasts in the grain size, internal geometry, and architecture of the sandstone bodies reveal significant facies changes across the basin. Proximal bodies that formed closest to the basin-margin ancestral Uncompahgre and Front Range uplifts consists of massive cross-bedded and flat-bedded coarse-grained to conglomeratic sandstone deposited mainly channel scour and fill and by vertical and lateral accretion on sand-gravel bars in low-sinuosity rivers. Medial sandstone bodies consist mostly of cross-bedded and flat-bedded fine to coarse-grained sandstone that was also deposited in low-sinuosity rivers on sand flats and in sandy bars. Bankfull discharge in proximal and medial channels was probably about 400 to 1000 m/sup 3//sec. The most distal sandstone body is composed of flat- and ripple-laminated, very fine to fine-grained sandstone that probably was deposited in a distributary area, in part by sheet floods. Overall facies changes indicate down-system decreases in competence and depth of flow. Paleocurrent data indicate that Maroon rivers draining the ancestral Uncompahgre uplift flowed northeastward across most of the basin before merging with rivers draining the ancestral Front Range uplift. The depositional axis of the basin was therefore probably strongly skewed to the northeast during late Maroon time.

  16. Geology of Hebrus Valles and Hephaestus Fossae, Mars: evidence for basement control of fluvial patterns

    SciTech Connect

    Christiansen, E.H.

    1985-01-01

    Hebrus Valles (HV) and Hephaestus Fossae (HF) are valley systems located SW of Elysium Mons in the low northern plains of Mars. HV share many of their characteristics with other martian outflow channels--widely interpreted as having formed by catastrophic flooding. The NW-trending HV system is 250 km long and begins in an elongate depression. Individual channels are less than 1 km wide; a braided reach is about 10 km wide. Streamlined islands are abundant in the middle reach. HV terminate as a series of narrow distributaries. No sedimentary deposits are obviously related to the development of the channel. HV cut across a broad expanse of older plains dotted by irregular mesas and smaller knobs. HF are a connected series of linear valley segm