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1

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

Microsoft Academic Search

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

Hamed Zeidan El-Mowafy

2003-01-01

2

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

SciTech Connect

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.

Ambrose, W.A.; Levey, R.A. (Univ. of Texas, Austin, TX (United States)); Vidal, J.M. (ResTech, Inc., Houston, TX (United States)); Sippel, M.A. (Research and Engineering Consultants, Inc., Englewood, CA (United States)); Ballard, J.R. (Envirocorp Services and Technology, Houston, TX (United States)); Coover, D.M. Jr. (Pintas Creek Oil Company, Corpus Christi, TX (United States)); Bloxsom, W.E. (Coastal Texas Oil and Gas, Houston, TX (United States))

1993-09-01

3

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

NASA Astrophysics Data System (ADS)

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.

El-Mowafy, Hamed Zeidan

4

Discharge and fluvial sediment transport in a semi-arid high mountain catchment, Agua Negra, San Juan, Argentina  

Microsoft Academic Search

The measurements of discharge and fluvial sediment transport carried out in a semi-arid catchment of the High Andes of Cuyo\\u000a show that the concentration of suspended sediment increases as the catchment area becomes larger, whereas the discharge shows\\u000a only a minimal increase further downstream or even a decrease in certain parts, due to the high rates of seepage and evaporation.

Dietrich Barsch; Hans Happoldt; Roland Mäusbacher; Lothar Schrott; Gerd Schukraft

1994-01-01

5

Understanding the Fluvial Critical Zone  

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

6

Fluvial sediment in Ohio  

USGS Publications Warehouse

Characteristics of fluvial sediment in Ohio streams and estimates of sediment yield are reported. Results are based on data from several daily record stations and 5 years of intermittent record from a 38-station network. Most of the sediment transported by Ohio streams is in suspension. Mean annual bedload discharge, in percentage of mean annual suspended-sediment discharge, is estimated to be less than 10 percent at all but one of the sediment stations analyzed. Duration analysis shows that about 90 percent of the suspended sediment is discharged during 10 percent of the time. Concentration of suspended sediment averages less than 100 milligrams per liter 75 percent of the time and less than 50 milligrams per liter 50 percent of the time. Suspended sediment in Ohio streams is composed mostly of silt and clay. Sand particle content ranges from 1 to 2 percent in northwestern Ohio to 15 percent in the east and southeast. Sediment yields range from less than 100 tons per square mile per year (35 tonnes per square kilometer per year) in the northwest corner of Ohio to over 500 tons per square mile per year (17,5 tonnes per square kilometer per year) in the southern part, in Todd Fork basin, lower Paint Creek basin, and the Kentucky Bluegrass area. Yield from about 63 percent of Ohio's land area ranges from 100 to 200 tons per square mile per year (35 to 70 tonnes per square kilometer per year).

Anttila, Peter W.; Tobin, Robert L.

1978-01-01

7

What is a fluvial levee?  

Microsoft Academic Search

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

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

1997-01-01

8

Meandering: fluvial versus tidal. (Invited)  

NASA Astrophysics Data System (ADS)

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.

Seminara, G.

2009-12-01

9

Computation of fluvial-sediment discharge  

USGS Publications Warehouse

This report is one of a series concerning the concepts, measurement, laboratory procedures, and computation of fluvial-sediment discharge. Material in this report includes procedures and forms used to compile and evaluate particle-size and concentration data, to compute fluvial-sediment discharge, and to prepare sediment records for publication.

Porterfield, George

1972-01-01

10

La FDA Regula la Seguridad del Agua Envasada - Incluidas ...  

Center for Food Safety and Applied Nutrition (CFSAN)

... El agua con efervescencia agregada, la soda (o agua mineral con gas), el agua tónica y el agua "seltzer", siempre han sido reguladas por la FDA ... More results from www.fda.gov/food/foodborneillnesscontaminants/buystoreservesafefood

11

The fluvial record of climate change.  

PubMed

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

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

2012-05-13

12

Quantifying the fluvial autogenic processes: Tank Experiments  

NASA Astrophysics Data System (ADS)

The evolution of deltaic shorelines has long been explained by allogenic changes in the environment such as changes in tectonics, base level, and sediment supply. Recently, the importance of autogenic cyclicity has been recognized in concert with allogenic forcing. Decoupling autogenic variability from allogenic signatures is essential in order to understand depositional systems and the stratigraphic record; however, autogenic behavior in sedimentary environments is not understood well enough to separate it from allogenic factors. Data drawn from model experiments that isolate the autogenic variability from allogenic forcing are the key to understanding and predicting autogenic responses in fluvial and deltaic systems. Here, three experiments using a constant water discharge (Qw) with a varying sediment flux (Qs) are conducted to examine the autogenic variability in a fluviodeltaic system. The experimental basin has dimensions of 1 m x 1 m, and a sediment/water mixture was delivered into the experimental basin. The sediment mixture contained 50% fine sand (.1 mm) and 50% coarse sand (2 mm) by volume and was delivered into the basin. The delta was built over a flat, non-erodible surface into a standing body of water with a constant base level and no subsidence. The autogenic responses of the fluvial and deltaic systems were captured by time-lapse images and the shoreline position was mapped to quantify the autogenic processes. The autogenic response to varying sediment supply while maintaining constant water supply include changes in 1) the slope of the fluvial-surface, 2) the frequency of autogenic storage and release events, and 3) shoreline roughness. Interestingly, the data shows a non-linear relationship between the frequency of autogenic cyclicity and the ratio of sediment supply to water discharge. The successive increase in the sediment supply and thus the increase in the ratio of Qs to Qw caused the slope of the fluvial surface to increase, and the frequency of autogenic sediment storage and release events to increase, but in a non-linear nature. This non-linear increase results from the autogenic frequency not increasing by a factor of 2 when the sediment flux increases by a factor of 2. Since the experimental data suggests that the frequency of autogenic variability is also related to the slope of the fluvial-surface, an increase in the fluvial slope would force the fluvial system to experience larger autogenic processes over a longer period of time. These three experiments are part of a larger matrix of nine total flume experiments, which explore variations in sediment supply, water discharge, and Qs/Qw to better understand fluvial autogenic processes.

Powell, E. J.; Kim, W.; Muto, T.

2010-12-01

13

The Stochastic Theory of Fluvial Landsurfaces  

Microsoft Academic Search

A stochastic theory of fluvial landsurfaces is developed for transport-limited erosion, using well-established models for the water and sediment fluxes. The mathematical mod- els and analysis is developed showing that some aspects of landsurface evolution can be described by Markovian stochastic processes. The landsurfaces are described by non- deterministic stochastic processes, characterized by a statistical quantity the variogram, that exhibits

Björn Birnir; J. Hernandez; T. R. Smith

2007-01-01

14

Mars: Fluvial Erosion Driven by Magmatism  

Microsoft Academic Search

Mars at present has a thin, dry, and cold atmosphere relative to Earth's. The cold temperatures suggest that any subsurface water (perhaps combined with carbon dioxide as clathrate) would likely be frozen within a couple kilometers or more of the surface. This condition may have been prevalent following widespread fluvial dissection that formed numerous valley networks in highland rocks during

K. L. Tanaka; J. A. Skinner; M. G. Chapman

2002-01-01

15

Fluvial geomorphology and paleohydrology in Japan  

Microsoft Academic Search

An introduction to fluvial geomorphology and paleohydrology in Japan is provided for researchers who are unfamiliar with these topics. Studies by Japanese geomorphologists are reviewed including those published only in Japanese-language journals. Emphasis is placed upon the following aspects: (1) abundant sediment yields from steep watersheds subjected to frequent heavy rains despite heavily vegetated conditions, (2) extensive sedimentation in mountain

Takashi Oguchi; Kyoji Saito; Hiroshi Kadomura; Michael Grossman

2001-01-01

16

A Field Exercise in Fluvial Sediment Transport.  

ERIC Educational Resources Information Center

|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…

Tharp, Thomas M.

1983-01-01

17

Chapter 3 Fluvial and Associated Carbonate Deposits  

Microsoft Academic Search

Fluvial and associated carbonate deposits are common nowadays and in the Quaternary record, but are less abundant further back in time. At present, they develop under climate conditions ranging from cool temperate to arid. A complex interaction among climate, tectonics, topography, hydrology and hydrochemistry controls their development. Their formation is primarily related to calcium- and bicarbonate-rich waters, the presence of

C. Arenas-Abad; M. Vázquez-Urbez; G. Pardo-Tirapu; C. Sancho-Marcén

2010-01-01

18

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

Microsoft Academic Search

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

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

2007-01-01

19

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

Microsoft Academic Search

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

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

2007-01-01

20

Martian fluvial conglomerates at Gale crater.  

PubMed

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

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

21

Geomorphic elements on modern distributive fluvial systems  

NASA Astrophysics Data System (ADS)

Analysis of over 400 fluvial megafans (> 30 km in length) in aggradational continental sedimentary basins reveals that geomorphic channel and floodplain changes on these distributive fluvial systems (DFS) generally behave in predictable ways with increasing distance from the apex. These changes can include: a decrease in discharge, a decrease in bed material transport and calibre of sediment, a decrease in stream power, an overall decrease in channel width, an overall decrease in channel depth, an increase in avulsive behaviour, and sinuosity becomes more variable.Three generic geomorphic element models are proposed - reflecting observed changes in channel behaviour - based on measurable changes in channel width and planform characteristics with increasing distance downstream. The three models are derived from (1) a single braided channel that bifurcates downstream into low sinuosity channels; (2) a dominant, sinuous, single-thread channel that anabranches and bifurcates with distance downstream, creating smaller channels with varying sinuosity; and (3) a dominant multi-thread channel that anabranches and bifurcates with distance downstream, creating smaller channels with varying sinuosity.The changes in fluvial behaviour and landforms on DFS are in response to variable discharge and sediment supply ratios from the upstream catchment. In contrast to examples described in hydrogeomorphological literature for tributary fluvial systems where channel dimensions tend to increase downstream, observations from DFS suggest that - where the formative DFS channel does not retain the same dimensions - intrinsic geomorphic thresholds lead to the breakdown of the main trunk channel into smaller anabranching and distributary channels with distance downstream; in some instances the majority of channelised flow at the DFS termination may even be disintegrated. The observed range of termination types and floodplain soils for each DFS type are interchangeable dependent on local conditions. The modern geomorphic elements and floodplain soils are dependent on climate in the upstream catchment and in the downstream receiving sedimentary basin.

Davidson, Stephanie K.; Hartley, Adrian J.; Weissmann, Gary S.; Nichols, Gary J.; Scuderi, Louis A.

2013-01-01

22

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

SciTech Connect

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.

Kerr, D.R.; Jirik, L.A. (Univ. of Texas, Austin (USA))

1990-09-01

23

Can anomalous diffusion describe depositional fluvial profiles?  

NASA Astrophysics Data System (ADS)

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 ? in the range 1.1 < ? + 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.

Voller, V. R.; Paola, C.

2010-06-01

24

¡Truco Con Agua!  

NSDL National Science Digital Library

En esta actividad los aprendices aprenderán un truco de magia donde la magia es la presión del aire. Los participantes tomarán un vaso de agua medio lleno y lo taparán con un pedazo de plástico o cartón. Sosteniendo la tarjeta contra el vaso, lo voltearán boca abajo y cuando quiten la mano debajo del vaso, ¡abracadabra! no se caerá el agua. En la tira cómica, Mateo explica a los aprendices que la presión que hace el aire en todas las direcciones es la que sostiene la tarjeta.

Science, Lawrence H.

2009-01-01

25

Mars: Fluvial Erosion Driven by Magmatism  

NASA Astrophysics Data System (ADS)

Mars at present has a thin, dry, and cold atmosphere relative to Earth's. The cold temperatures suggest that any subsurface water (perhaps combined with carbon dioxide as clathrate) would likely be frozen within a couple kilometers or more of the surface. This condition may have been prevalent following widespread fluvial dissection that formed numerous valley networks in highland rocks during the Noachian. The sources of some ancient and of most relatively young valley systems, particularly the large outflow channels, occur within or near volcanic rocks or display morphologic evidence for volcanic and/or tectonic associations. Such geologic relations have led many investigators to propose that magmatic activity has been a significant (if not dominant) driver of younger fluvial erosion on the surface of Mars. Magmatism may have provided the heat to raise local subsurface temperatures to near or above the freezing point of water; furthermore, intrusive activity may have fractured aquifers that provided conduits for release of substantial volumes of ground volatiles. Evidence of such interactions includes lengthy outflow channels sourced from fissures or depressions in volcanic rocks of the Tharsis/Valles Marineris, Elysium, and eastern Hellas regions. Depressions filled with chaotic terrain at the heads of the circum-Chryse outflow channels may be sites where large volumes of magmatic material may have interacted with water and perhaps carbon dioxide in rocks beneath the cryosphere, leading to catastrophic expulsion of the volatiles and collapse of country rock. Other evidence for magmatically driven erosion may include the low Hellas rim areas, where Malea and Hesperia Plana reside, and the channeled flanks of possible Noachian volcanoes in Thaumasia (south Tharsis region). Mars Global Surveyor's MOLA topography data and MOC images and Mars Odyssey's THEMIS images are providing new insights into the possible interactions between magmatism and fluvial erosion on Mars.

Tanaka, K. L.; Skinner, J. A.; Chapman, M. G.

2002-12-01

26

INTERACTIONS BETWEEN FLUVIAL SYSTEMS AND LARGE SCALE HYDRO-PROJECTS  

Microsoft Academic Search

A large-scale hydro-project is defined as one or a chain of engineering structures, whose operation may obviously change the hydrological or hydraulic conditions of the river on which it is constructed. This paper studies the fluvial processes in the upstream reaches and tributaries and downstream reaches affected by dams, and the fluvial impacts of channelization and water diversions. Damming of

Zhaoyin WANG; Chunhong HU

2004-01-01

27

Fluvial Processes Project - Analysis of Redwood Creek Field Data  

NSDL National Science Digital Library

This exercise is intended to give student experience using field data they collected to analyze the fluvial processes that occur in Redwood Creek, and the landforms that result. Designed for a geomorphology course

Sklar, Leonard

28

Holocene fluvial processes in Troy plain  

NASA Astrophysics Data System (ADS)

The Troy plain is the lower part of Scamander (Karamenderes) River basin before its mouth in the Dardanelle straits. The fluvial processes of the deltaic progradation and floodplain aggradation have changed the landscape of the plain during the past 10,000 years. They transformed a sheltered gulf reaching the Ancient Troy into an extensive plain. Ancient Troy is today 7 km inland while Simois (Dumrek) River is a tributary of Scamander (Karamenderes) River. A detailed geomorphological survey with high resolution topographical measurements was carried out using of a TOPCON FC100 differential GPS. This survey took place not only along the Troy plain but further southwards in Araplar gorge and Ezine basin. The morphological analysis of the data showed that the graded channel profile of the Scamander River is lower than its alluvial plain. The channel incision ranging from 2 to 5 meters is responsible for the formation of a pair of alluvial terraces along the channel. These aggradational terraces formed into the resent alluvial sandy deposits of the basin. The channel morphology of an alluvial river like Scamander is highly sensitive in changes concerning the discharge and the sediment load at downstream points. Active tectonics, climate change and sea level rise are the main causes of changes in the channel equilibrium. Ten sediment samples, from the alluvial terraces in Araplar gorge, were dated with OSL technique. The sample ages allowed the time estimation of the channel changes.

Vouvalidis, Konstantinos; Ates, Ozkan; Syrides, George; Pavlides, Spyros; Tutkun, Zeki; Chatzipetros, Alexandros; Ozden, Suha; Mavroudis, Petros; Sboras, Sotirios; Kurcer, Akin; Valkaniotis, S.

2010-05-01

29

Seismic modeling of fluvial reservoirs in outcrop  

SciTech Connect

Three-dimensional (3-D) seismics and concomitant improvements in processing techniques have increased the amount of reservoir-scale information that can be obtained from the seismic waveform reaching the surface. However, the geological significance of these seismic events remains unclear. The seismic modeling of reservoir formations in outcrops allows analogs to be drawn to the seismic response of reservoirs at depth. Previous outcrop modeling studies are mostly high-frequency approximations, suitable for large-scale geometrical imaging but unsuitable for imaging lateral variations in lithology and geometry of bodies that lie on or below the [open quotes]visual[close quotes] resolution of the seismic tool. This study examines finite-difference seismic modeling of Tertiary, fluvial-sandstone bodies in outcrop from central Spain. The outcrops were well known from reservoir characterization studies, easily accessible, and well exposed. Outcrop geometry was converted into a finite-difference grid, with density and velocity values coming from measurements of cores and blocks from each of the lithologies. Synthetic traces were generated. The traces were then processed in the conventional manner. Full solution of the wave equation allows all wave types to be modeled, e.g., diffraction sand multiples. Models were generated to simulate reservoir conditions at the surface and at depth. Seismic wave-forms could then be related back to reservoir characteristics. Seismic modeling of reservoir sands in outcrop can aid in the interpretation of such bodies at depth. Seismic modeling of reservoirs is a low-cost interpretation tool that may aid field development by delineation of reservoirs in area of complex sedimentology where surface analogs exist.

Campbell, E. (IGG-TNO, Delft (Netherlands))

1993-09-01

30

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

31

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

32

Accommodation controls on fluvial-deltaic reservoir architecture  

SciTech Connect

Hydrocarbon recovery efficiency is controlled by reservoir heterogeneities resulting from geometric arrangements of strata, or {open_quotes}stratal architecture{close_quotes}. Traditional reservoir characterization relates depositional systems to stratal architecture. High-resolution sequence stratigraphy of outcrop analogs provides a chronostratigraphic framework for evaluating accommodation conditions of depositional systems. Key stratigraphic surfaces and/or correlative strata define a hierarchy of chronostratigraphic units of different periodicities. The Upper Cretaceous Ferron Sandstone, an analog to high accommodation and sediment supply fluvial-deltaic reservoirs, comprises an intermediate-term stratigraphic sequence consisting of seven short-term stratigraphic cycles. Each short-term stratigraphic cycle contains fluvial- to storm-dominated shallow-marine deposits laterally replaced by distributary channel deposits. The Lower Cretaceous Fall River Formation, an analog to low accommodation fluvial-deltaic reservoirs, comprises an intermediate-term stratigraphic sequence consisting of six short-term stratigraphic cycles. Detailed outcrop study of valley fill strata shows unconformities controlling permeability distributions, segregating the reservoir, and juxtaposing low and high permeability strata. Hence, in low accommodation fluvial-deltaic strata the most important stratal element affecting fluid flow are unconformity bounded short-term stratigraphic cycles. This contrasts with high accommodation fluvial-deltaic strata where smaller-scale depositional elements comprising individual short-term stratigraphic cycles form flow units.

Gardner, M.H.; Willis, B.J.; Barton, M.D. [Univ. of Texas, Austin, TX (United States)

1995-08-01

33

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

NASA Astrophysics Data System (ADS)

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.

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

2009-12-01

34

Incision of Fluvial Channels on Titan  

NASA Astrophysics Data System (ADS)

Networks of sinuous channels have been observed on the surface of Titan, most notably by the imaging experiment on the Huygens probe [1], and these channels may be carved into the icy surface by infrequent torrential downpours of liquid methane from the thick atmosphere [2]. A methane stream on Titan with water ice sediment will operate at a higher transport stage than a stream on the Earth with the same shear velocity, due to the lower gravity and increased sediment buoyancy on Titan [3]. The low gravity also requires steeper slopes or greater flow depths to achieve the same shear velocity, which cancels out part of the increased transport stage on Titan. The incision of stream channels into Titan's ice bedrock may take place by abrasion, plucking, and/or cavitation [e.g. 4]. Bedload abrasion is investigated using the Sklar and Dietrich model [5] and by measuring the abrasion resistance of water ice at near-Titan temperatures. The resulting erosion rates are similar to what would be expected in a sandstone channel on Earth, for the same values of slope, discharge, and sediment supply. Abrasion by suspended particles may scale in a similar way. Plucking could be slightly enhanced by higher transport stage in Titan streams, but the production of pluckable bedrock blocks depends on unknown ice bedrock parameters such as jointing or layering. Due to the high atmospheric pressure, cavitation is probably a slightly less effective erosive agent on Titan than on the Earth. The result of comparing fluvial incision processes on Earth and Titan is that despite orders of magnitude differences in some of the physical parameters that govern these processes on the two bodies, the erosion rates are likely to be fairly similar, given similar stream conditions. It remains to be seen whether the assumption of similar stream conditions (slope, discharge, sediment supply) is valid, and this can be addressed with further modeling and analysis of data from the Cassini-Huygens mission, as well as data that could be collected by a future Titan-focused mission. References: [1] Tomasko et al., Nature, 2005; [2] Lorenz et al., GRL, 2005; [3] Burr et al., Icarus, submitted; [4] Whipple et al., GSA Bull., 2000; [5] Sklar and Dietrich, Water Resour. Res., 2004.

Collins, G. C.

2005-12-01

35

Hesperian fluvial landforms on Mars : Regional or global activity? (Invited)  

NASA Astrophysics Data System (ADS)

Fluvial activity on Mars is identified from well organized valley networks, which activity peaked in the Late Noachian - Early Hesperian transition. Nevertheless, a growing trend of evidence supports the presence of fluvial activity later in the Hesperian period (3 to 3.5 Gy), after the traditional period of early Mars activity ceased. Small post-noachian valleys such as those on volcanoes, could suggest that regional effects are predominant. However, more regions of post-Noachian activity are now identified, and some of them contain lacustrine deposits dated of the same epoch. In this study, we propose to examine the morphology and chronology of two types of fluvial landforms. First, in regions such as Valles Marineris, Thaumasia highlands and Nili Fossae, fluvial valleys are associated with depositional fans (sometimes being delta) that lay on Hesperian bedrock. Despite valleys are less branched than typical early Mars valleys, these landforms require sustained liquid water to form. Second, fretted channels are known as post-Noachian erosional valleys of unknown origin, rectangular in section and poorly branched. They are re-assessed using most recent orbital data. Results show that they likely consist of fluvial valleys, with local lacustrine activity and fan deposition in lows. A set of depositional fans are also identified on plateaus near these fretted channels in Deuteronilus Mensae showing that this fluvial activity was not limited to putative subsurface aquifers and sapping erosion forming rectangular valleys. Even if regional activity certainly exists and explain some landforms, these results mainly favor a role of a global climate to form these Hesperian landforms. Nevertheless, an episodic activity, rather than a continuous activity, can explain most observations. The origin of such a episodic global activity will be discussed.

Mangold, N.

2009-12-01

36

Fluvial landforms on fresh impact ejecta on Mars  

NASA Astrophysics Data System (ADS)

Fluvial valleys provide critical clues to the distribution and state of water throughout the history of the planet Mars. Early in Mars' history (<3.7 Gy), the climate may have been warmer than at present leading to the development of valley networks. Younger valleys formed on volcanic and glacial landforms under colder conditions than experienced in Mars' early history. Only rare examples of fluvial valleys over fresh impact craters have been reported. In the present study, a survey of hundreds of fresh post-Noachian impact craters (of 12 to 150 km in diameter) has been done to identify fluvial landforms, especially in regions lacking ancient valleys, using images from the High Resolution Stereo Camera (HRSC) instrument onboard Mars Express and from the Context Camera (CTX) instrument onboard Mars Reconnaissance Orbiter. Observations show that these valleys are locally sinuous, display isolated channels, a poor connectivity and frequent braiding. Valleys were most likely formed over a short duration with high discharge rates, estimated from 500 to 40,000 m3 s-1. In Arabia Terra, a total of 27 out of the 204 surveyed craters were found to have fluvial landforms on the ejecta blanket, exclusively in the mid-latitude band (25-45°). Dating of impact ejecta gives young ages from the Late Hesperian to the Middle Amazonian, thus providing a temporal constraint for the fluvial activity. Late climatic episodes of snow deposition and subsequent melting scattered in space and time could explain observations. Alternatively, the thermal anomaly of impacts and their ejecta over ice-bearing terrains is a possible triggering mechanism for the observed fluvial valleys. Calculations show that the thermal anomaly can persist in the ejecta over several hundreds of years for mid-size craters (20-40 km). Such a process would not explain all Martian fluvial activity because of the marked difference between the pristine landforms described and Late Noachian valley networks. Nevertheless, fluvial landforms on preserved ejecta blankets can be used as a new proxy for the temporal distribution of water on Mars.

Mangold, N.

2012-03-01

37

Relative size of fluvial and glaciated valleys in central Idaho  

Microsoft Academic Search

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

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

2008-01-01

38

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

Microsoft Academic Search

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

R. J. Janda; D. F Meyer

1985-01-01

39

Isochronous fluvial systems in Miocene deposits of Northern Pakistan  

Microsoft Academic Search

A palaeomagnetic isochron dated at about 8.1 Myr BP and detailed lithostratigraphy of a 40 m interval exposed along strike for 40 km establish the depositional patterns of two contemporaneous, interfingering fluvial systems in the upper part of the Middle Siwalik sequence. The two systems, referred to as the buff and blue-grey, differ in unit shape, lithofacies, bedding sequence, palaeocurrent

Anna K. Behrensmeyer; Lisa Tauxe

1982-01-01

40

Taphonomy of plants in a paratropical fluvial system  

Microsoft Academic Search

Investigation of the subenvironments of a modern paratropical fluvial system in southern Mexico indicates that certain depositional settings are relatively accurate in representing the local flora. Epiphytes, lianas, and those woody plants that are a small fraction of the standing biomass occur in sediments in approximate proportion to their representation (number of individuals) in the vegetation. A paleoenvironmental reconstruction of

Burnham

1986-01-01

41

Fluvial systems in the Siwalik Miocene and Wyoming Paleogene  

Microsoft Academic Search

The 3 km thick Miocene Siwalik Group (Himalayan foredeep in northern Pakistan) and the 2 km thick Paleogene Fort Union\\/Willwood formations (Bighorn Basin in Wyoming) both preserve long records of fluvial deposition adjacent to rising mountain belts. Depositional environments and associated habitats change across large basins along with changing physiography and with the location of different river systems that may

B. J. Willis; A. K. Behrensmeyer

1995-01-01

42

Processes, facies and architecture of fluvial distributary system deposits  

Microsoft Academic Search

There is evidence from the stratigraphic record of examples of fluvial deposits that were the products of deposition from river systems which had decreasing discharge down-flow and transitions from proximal, channelised to distal, unconfined flow. These deposits form fan-shaped bodies several tens of kilometres in radius, and their stratigraphic architecture is aggradational, with no evidence of deep incision driven by

G. J. Nichols; J. A. Fisher

2007-01-01

43

Ecotones and fluvial regimes in arctic lotic environments  

Microsoft Academic Search

The fluvial regime in arctic streams is influenced by size of stream, the presence and storage capacity of lakes in the drainage basin, groundwater, and permafrost. Exchange of material with terrestrial environments depends on the season and is more or less suspended in winter. Permafrost and water storage in ice and snow control run off and erosion. Damage to vegetation

G. Power; M. Power

1995-01-01

44

Hillslope to fluvial process domain transitions in headwater catchments  

NASA Astrophysics Data System (ADS)

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

Williams, Karen Mary

45

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

NASA Astrophysics Data System (ADS)

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.

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

2010-03-01

46

Fluvial response to subsidence determined from remote sensing  

Microsoft Academic Search

Well-exposed rocks of the fluvial Willwood Formation covering approximately 5,000 km² of the central part of the Big Horn basin, Wyoming, were analyzed with Thematic Mapper (TM) data. False-color images and field analysis were used to characterize and map large-scale lithologic packages in this lower Eocene unit. Field criteria used to distinguish among the packages include mudstone coloration and type

Kraus

1990-01-01

47

Fluvial channels on Titan: Initial Cassini RADAR observations  

Microsoft Academic Search

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

Ralph D. Lorenz; Rosaly M. Lopes; Flora Paganelli; Jonathan I. Lunine; Randolph L. Kirk; Karl L. Mitchell; Lawrence A. Soderblom; Ellen R. Stofan; Gian Ori; Melissa Myers; Hideyaki Miyamoto; Jani Radebaugh; Bryan Stiles; Stephen D. Wall; C. A. Wood

2008-01-01

48

Fluvially-deposited large wood and riparian plant diversity  

Microsoft Academic Search

Out-of-channel wood jams centred by fluvially-deposited large wood represent an important habitat for riparian plant species\\u000a along large rivers dominated by exposed riverine sediments. Such wood jams often display distinct physical features associated\\u000a with the jams, such as areas of scour immediately upstream, plumes of fine sediment downstream and abundant organic material\\u000a deposited throughout the jam. This paper examines the

Robert A. Francis; Paolo Tibaldeschi; Luke McDougall

2008-01-01

49

Interaction of fluvial and lacustrine/marine processes on Titan  

NASA Astrophysics Data System (ADS)

Synthetic Aperture Radar images of Titan's surface acquired by Cassini reveal a host of lakes and seas at high latitudes, dominantly in the north. Channel systems are seen to drain into some bodies, while other shorelines appear relatively undissected at the resolution of the available data (?300 m/pix). Digital Elevation Models derived from stereo SAR imagery allow quantitative analysis of near-shore topography, with improved accuracy due to an innovative de-noising algorithm (see also Lucas et al., AGU 2011). Here we consider the interaction of fluvial systems with lakes and seas, and their relative contribution to the liquid filling these as a function of size. We find evidence for the topographic effect of near-shore incision at the shorelines of Kraken Mare, at and near the island Mayda Insula. We identify a shoulder in the histogram (at an elevation of approximately -240 m in Figure 1) suggesting that fluvial and/or lacustrine processes redistributed near-shore material forming a topographic bench. Terrestrial examples show similar patterns in the hypsometric distribution, owing to fluvial erosion. These results are consistent with observations from SAR images and show that erosion and sediment transport have influenced the topography substantially, with their integrated action quantifiable volumetrically.

Aharonson, O.; Lucas, A.; Hayes, A. G.; Cassini Radar Science Team

2011-12-01

50

Headwaters are critical reservoirs of microbial diversity for fluvial networks.  

PubMed

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

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

2013-10-02

51

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

NASA Astrophysics Data System (ADS)

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.

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

2007-11-01

52

Fluvial geomorphology: where do we go from here?  

NASA Astrophysics Data System (ADS)

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

Smith, Derald G.

1993-07-01

53

The Agua Salud Project, Central Panama  

NASA Astrophysics Data System (ADS)

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.

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

2007-12-01

54

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

USGS Publications Warehouse

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.

Simon, A.

1992-01-01

55

Fluvial response to subsidence determined from remote sensing  

SciTech Connect

Well-exposed rocks of the fluvial Willwood Formation covering approximately 5,000 km{sup 2} of the central part of the Big Horn basin, Wyoming, were analyzed with Thematic Mapper (TM) data. False-color images and field analysis were used to characterize and map large-scale lithologic packages in this lower Eocene unit. Field criteria used to distinguish among the packages include mudstone coloration and type and abundance of nodules, both of which reflect the type of alluvial paleosol that developed; abundance, geometry, and paleotransport direction of sand bodies; and abundance and geometry of carbonaceous shales. The lithologic packages reflect both spatial and temporal variability; biostratigraphic data were used to establish which packages are time correlative. Differences among time-correlative fluvial packages (facies) reflect variability in local moisture regimes and sediment accumulation rates, factors that influenced the location of major stream channels and the types of palesols that formed on overbank deposits. Facies distribution demonstrates that east-west-trending lineaments, which segment the Bighorn Mountains, extend into the basin and were active faults during the early Eocene. The lithologic heterogeneity is attributed to differential crustal subsidence on either side of the lineament. Vertical changes in lithology record temporal variability in basin subsidence rates. Subsidence rates slowed over time producing brighter mudstones (more mature paleosols) higher in the section and changes in carbonaceous shale type and abundance. The location of major channel sand bodies also appears to have shifted westward over time. Fluvial Willwood rocks arc capped by the lacustrine Tatman Formation in certain parts of the basin. TM images suggest that the north-south extent of the lake deposits was determined by the location of several of the lineaments.

Kraus, M.J. (Univ. of Colorado, Boulder (USA))

1990-05-01

56

Modelling complex geomorphic systems: the example of fluvial obstacle marks  

NASA Astrophysics Data System (ADS)

Obstacles in fluvial environments cause local flow separation and the emergence of three-dimensional flow fields that can lead to scour and deposition around an obstacle, even well before the initiation of general particle movement at the bed. Resulting forms are commonly denoted as 'fluvial obstacle marks'. Typically, fluvial obstacle marks consist of an upstream scour hole and a downstream depositional sediment ridge. However, the specific morphology of these forms is depended on the interaction between obstacle-, flow- and sediment characteristics. Dynamic interrelations between hydraulic and sedimentary processes lead to non-linear patterns of form genesis. As observation and analysis of form genesis and formative processes is difficult in the field, laboratory flume experiments were conducted, which allowed to directly observe obstacle mark development under controlled boundary conditions. For the individual experimental set-ups cylinders of different sizes and shapes were used, each placed in a layer of coarse sand and exposed to steady currents of different magnitudes for at least 20h. Under these conditions quasi-equilibrium obstacle marks developed. The turbulent flow field around the obstacles was analysed by injecting special dye-tracers and by conducting three-dimensional velocity measurements. Bed form morphologies and dynamics were recorded using a laser distance sensor. Although this type of (physical) modelling accompanies complexity-reduction, it helped to systematically identify and quantify order and control parameters as well as thresholds, phase transitions and emergent form features. For utilisation of the experimental results, the values of major order (e.g. maximum depth of scour) and control parameters (e.g. obstacle Reynolds number) were incorporated into different statistical models (non-linear regression curves and artificial neural networks) and finally validated against data from other lab and field studies. Validation showed that the present method works well in comparison to other data attained in the laboratory and to a certain extend in comparison with field data. The overall results of this study suggest that research approaches based on intertwined experimental, field and mathematical methods with a specific focus on on formative processes might smooth the way from the vast theoretical construct of complex systems theory to applicable model building in (fluvial) geomorphology.

Euler, Thomas

2010-05-01

57

Impacts of fluvial sedimentary heterogeneities on CO2 storage performance  

NASA Astrophysics Data System (ADS)

The heterogeneity of fluvial systems is a key parameter in sedimentology due to the associated impacts on flow performance. In a broader context, fluvial reservoirs are now targets for CO2 storage projects in several sedimentary basins (Paris Basin, North German Basin), thus calling for detailed characterization of reservoir behaviour and capacity. Fluvial reservoirs are a complex layout of highly heterogeneous sedimentary bodies with varying connectivity, depending on the sedimentary history of the system. Reservoir characterization must determine (a) the nature and dimension of the sedimentary bodies, and (b) the connectivity drivers and their evolution throughout the stratigraphic succession. Based on reservoir characterization, geological modelling must account for this information and can be used as a predictive tool for capacity estimation. Flow simulation, however, describes the reservoir behaviour with respect to CO2 injection. The present work focuses on fluvial reservoir performance and was carried out as part of a PhD (2008-2011) dedicated to the impact of sedimentary heterogeneity on CO2 storage performance. The work comprises three steps: ? Reservoir characterization based on detailed fieldwork (sedimentology and sequence stratigraphy) carried out in Central Arabia on the Minjur Sandstone. Twelve depositional environments and their associated heterogeneity are identified, and their layout is presented in a high-resolution sequence stratigraphy analysis. This step is summed up in a 3D geological model. ? Conceptual modelling based on this field data, using gOcad software and an in-house python code. The purpose was to study, for a given architecture, the impact of sedimentary heterogeneity on storage capacity estimations using two models: one with heterogeneity within the sedimentary fill (model A); the other without heterogeneity within the sedimentary fill (model B). A workflow was designed to estimate and compare the storage capacities for a series of some 50 scenarios. The results show that a strong compartmentalization, due to a shaly barrier, may decrease storage capacity by 11 to 25 percent. ? Flow-simulation of an 8-scenario sample extracted from the 50 possible scenarios. In contrast to the static modelling estimated capacities, the preliminary flow-simulation results indicate that capacity remains similar whichever model is applied (A or B). This is because the scale of the heterogeneity is similar to the extent of the CO2 plume, meaning that heterogeneity does not affect the amount of injected CO2 that can be stored in the sedimentary body. Nevertheless, connectivity strongly influences storage capacity, as determined by the 8 scenarios (model A) in which the total amount of CO2 injected ranges between 7 and 12 Mt over a 50-year period. Moreover, heterogeneity significantly increases pressure build-up, and may strongly disrupt the hydrodynamics in the aquifer.

Issautier, B. H.; Viseur, S.; Audigane, P. D.

2011-12-01

58

Fluvial deposits as an archive of early human activity  

NASA Astrophysics Data System (ADS)

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.

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

59

Currents and Bathymetry at the Fluvial-tidal Transition  

NASA Astrophysics Data System (ADS)

We monitored stage, velocity profile and bathymetry at the fluvial-tidal transition of a coastal plain river. Time-lagged correlation coefficients between the free surface and flow velocity oscillations indicate that abruptly decreasing channel depth in the direction of upstream tidal propagation has a greater impact on the tidal wave attenuation than the bottom friction over a shoal. We hypothesize that this dissipation of long wave tidal energy over highly variable bathymetry produces a self-sustaining loop, being the cause and product of flood tide energy dissipation. The net result is a highly variable alluvium cover and a potential energy source for the maintenance and formation of channel deeps. For the Santee River, with the sediment supply diminished by a dam and little apparent bank erosion, the interactions of flood tide and fluvial hydrodynamic processes appear to maintain a channel reach with up to 3m of alluvium, abruptly transitioning to a 4km long predominantly bedrock reach with large channel deeps.

Torres, R.; Yankovsky, A. E.

2011-12-01

60

Facies controls on the distribution of diagenesis and compaction in fluvial-deltaic deposits  

Microsoft Academic Search

The Upper Triassic – Lower Jurassic Åre Formation comprising the deeper reservoir in the Heidrun Field offshore mid-Norway consists of fluvial channel sandstones (FCH), floodplain fines (FF), and sandy and muddy bay-fill sediments (SBF, MBF) deposited in an overall transgressive fluvial to lower delta plain regime. The formation has been investigated to examine possible sedimentary facies controls on the distribution

Erik Hammer; Mai Britt E. Mørk; Arve Næss

2010-01-01

61

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

Microsoft Academic Search

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

L. Allan James; W. Andrew Marcus

2006-01-01

62

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

Microsoft Academic Search

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

L. Allan James; W. Andrew Marcus

2006-01-01

63

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

Microsoft Academic Search

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

Jeffrey J Whicker; Jason P Field; David D Breshears

2008-01-01

64

Lahar hazards at Agua Volcano, Guatemala  

USGS Publications Warehouse

At 3,760 meters, Agua volcano towers more than 3,500 meters above the Pacific coastal plain to the south and 2,000 meters above the Guatemalan highlands to the north. The volcano is within 5 to 10 kilometers 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 kilometers 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. -- Schilling, et.al., 2001

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

2001-01-01

65

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

Microsoft Academic Search

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

Alan D. Howard

2007-01-01

66

Spectral gradients of downwelling light in a fluvial lake (Lake Saint-Pierre, St-Lawrence River)  

Microsoft Academic Search

Large fluvial lakes are understudied with respect to their underwaterlight climates. Fluvial lakes pose unique challenges for photobiologistsinterested in the interactions amongst light climate, nutrients and microbialcommunity structure and biodiversity. This is because fluvial lakes are typifiedby highly dynamic flow regimes often incorporating different inflows anddischarges each characterized by their own unique physico-chemical composition.These compositional characteristics include the concentrations of

Jean-Jacques Frenette; Michael T. Arts; Jean Morin

2003-01-01

67

GUÍA DE INSPECCIONES DE SISTEMAS DE AGUA DE ALTA ...  

Center for Drug Evaluation (CDER)

... Esta guía trata, principalmente desde un aspecto microbiológico, el examen y la evaluación de sistemas de agua de alta pureza que se utilizan ... More results from www.fda.gov/drugs/guidancecomplianceregulatoryinformation/guidances

68

Nuevas Especies de Algas de Agua Dulce Italiano-Españolas  

Microsoft Academic Search

Este modesto, deslabazado e insignificante trabajo de Algas de agua dulce, se lo dedico con mucho cariñ, veneració y respeto, al gran maestro de la Ficologia Prof. De Toni (q. e. p.d.).Las tres especies nuevas y la variedad, se las dedico a él. Oedogonium De-Tonii, Phythelios De-Tonii y Rivularia beccariana var. De toniana, han sido cogidas en las aguas dulces

Pedro González Guerrero

1964-01-01

69

Modeling fluvial erosion on regional to continental scales  

NASA Astrophysics Data System (ADS)

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.

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

1994-07-01

70

Probabilistic approaches to the modelling of fluvial processes  

NASA Astrophysics Data System (ADS)

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.

Molnar, Peter

2013-04-01

71

Identification and Evaluation of Fluvial-Dominated Deltaic Reservoirs.  

SciTech Connect

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.

Baken, Mary K.; Andrews, Richard

1997-11-15

72

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

SciTech Connect

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.

Kerr, D.R. (Univ. of Texas, Austin (USA))

1990-09-01

73

Determinacao de (sup 210) Pb em aguas minerais da cidade de Aguas da Prata. (Determination of (sup 210) Pb in mineral spring waters of Aguas da Prata city).  

National Technical Information Service (NTIS)

Concentration levels of (sup 210) Pb have been analyzed in 12 mineral spring waters of Aguas da Prata city. The (sup 210) Pb concentration was determined through (sup 210) Bi, by measuring the gross beta activity of the (sup 210) Pb Cr O(sub 4) precipitat...

S. R. D. Moreira

1993-01-01

74

Listeria monocytogenes aguA1, but Not aguA2, Encodes a Functional Agmatine Deiminase: BIOCHEMICAL CHARACTERIZATION OF ITS CATALYTIC PROPERTIES AND ROLES IN ACID TOLERANCE.  

PubMed

Listeria monocytogenes is adaptable to low pH environments and therefore crosses the intestinal barrier to establish systemic infections. L. monocytogenes aguA1 and aguA2 encode putative agmatine deiminases (AgDIs) AguA1 and AguA2. Transcription of aguA1 and aguA2 was significantly induced at pH 5.0. Deletion of aguA1 significantly impaired its survival both in gastric fluid at pH 2.5 and in mouse stomach, whereas aguA2 deletion did not show significant defect of survival in gastric fluid. With agmatine as the sole substrate, AguA1 expressed in Escherichia coli was optimal at 25 °C and over a wide range of pH from 3.5 to 10.5. Recombinant AguA2 showed no deiminase activity. Site-directed mutagenesis revealed that all nine AguA1 mutants completely lost enzymatic activity. AguA2 acquired AgDI activity only when Cys-157 was mutated to glycine. AguA1 mutation at the same site, G157C, also inactivated the enzyme. Thus, we have discovered Gly-157 as a novel residue other than the known catalytic triad (Cys-His-Glu/Asp) in L. monocytogenes that is critical for enzyme activity. Of the two putative AgDIs, we conclude that only AguA1 functionally participates in the AgDI pathway and mediates acid tolerance in L. monocytogenes. PMID:23918931

Cheng, Changyong; Chen, Jianshun; Fang, Chun; Xia, Ye; Shan, Ying; Liu, Yuan; Wen, Guilan; Song, Houhui; Fang, Weihuan

2013-08-05

75

Hydrated Minerals and Fluvial Features In and Around the Melas Chasma Basin  

NASA Astrophysics Data System (ADS)

Using a synergy of mineralogy derived from CRISM data and morphology interpreted from HiRISE and CTX images, we map geologic units within and around the Melas basin. Numerous hydrated minerals and fluvial features indicate a complex aqueous history.

Weitz, C. M.; Williams, R. M. E.; Noe Dobrea, E.; Baldridge, A.

2012-03-01

76

Studies on the Fluvial Environment, ARctic Coastal Plain Province, Northern Alaska. Volume I.  

National Technical Information Service (NTIS)

The studies on the fluvial environment of the Arctic Coastal Plain Province, Northern Alaska, include research which ranges in magnitude from small polygon troughs to the Inaru River Basin. The 208 figures include stereograms, ground and aerial photograph...

R. I. Lewellen

1972-01-01

77

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

Microsoft Academic Search

Geologic and geomorphic analyses of highland terrains reveal the effects of fluvial erosion by well-integrated valley networks. Hydrologic modeling using 128 pix\\/deg MOLA gridded topography is being done to quantitatively characterize these systems.

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

2002-01-01

78

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

NASA Astrophysics Data System (ADS)

Geologic and geomorphic analyses of highland terrains reveal the effects of fluvial erosion by well-integrated valley networks. Hydrologic modeling using 128 pix/deg MOLA gridded topography is being done to quantitatively characterize these systems.

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

2002-03-01

79

Permeability patterns in some fluvial sandstones. An outcrop study from Yorkshire, North East England.  

National Technical Information Service (NTIS)

The distribution of permeability in some fluvial sandbodies (lenticular bedded sheet sandstone, lateral accretion-bedded sandstone and crevasse splay complex) in The Middle Jurassic Scalby Formation was measured on two-dimensional outcrops with a miniperm...

T. Jacobsen H. Rendall

1989-01-01

80

Impact of historic mining activities on fluvial sediment dynamics  

NASA Astrophysics Data System (ADS)

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.

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

2009-04-01

81

What can we learn from fluvial incision in high mountains?  

NASA Astrophysics Data System (ADS)

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.

Fuchs, Margret; Gloaguen, Richard; Krbetschek, Matthias

2013-04-01

82

Differences in trace metal concentrations among fluvial morphologic units and implications for sampling  

Microsoft Academic Search

This study examines the segregation of trace metals within and between fluvial morphologic units in sand-sized and finer\\u000a bed sediments in a cobble bed stream. The types of fluvial morphologic units sampled are low gradient riffles, high gradient\\u000a riffles, glides, eddy drop zones, lateral scour pools, attached bars, and detached bars. Three to nine samples were collected\\u000a from ten of

S. C. Ladd; W. A. Marcus; S. Cherry

1998-01-01

83

Processes of fluvial island formation, with examples from Plum Creek, Colorado and Snake River, Idaho  

Microsoft Academic Search

A fluvial island is a landform, elevated above and surrounded by stream-channel branches or waterways, that persists sufficiently\\u000a long to establish permanent vegetation. Natural fluvial islands occur in any part of a drainage network but most commonly\\u000a in montane, piedmont-valley, and coastal flood-plain environments. Processes, often interactive, by which islands form include\\u000a avulsion (the sudden separation of land by a

W. R. Osterkamp; W. Anklam

1998-01-01

84

Correlation of fluvial terraces within the Hikurangi Margin, New Zealand: implications for climate and baselevel controls  

Microsoft Academic Search

A correlation of fluvial terraces is presented for eight non-glacial catchments of the eastern North Island, New Zealand, within the actively uplifting Hikurangi Margin. Using a combination of loess and tephra coverbed stratigraphy, and radiocarbon and OSL dating of fluvial deposits and loess coverbeds, we demonstrate correlation of four fill terraces, T1–T4. The available age constraints suggest T1=15–30 ka, T2=31–50

Nicola J. Litchfield; Kelvin R. Berryman

2005-01-01

85

Assessing the nonconservative fluvial fluxes of dissolved organic carbon in North America  

NASA Astrophysics Data System (ADS)

Fluvial transport of dissolved organic carbon (DOC) is an important link in the global carbon cycle. Previous studies largely increased our knowledge of fluvial exports of carbon to the marine system, but considerable uncertainty remains about in-stream/in-river losses of organic carbon. This study presents an empirical method to assess the nonconservative behavior of fluvial DOC at continental scale. An empirical DOC flux model was trained on two different subsets of training catchments, one with catchments smaller than 2,000 km2 (n = 246, avg. 494 km2) and one with catchments larger than 2,000 km2 (n = 207, avg. 26,525 km2). A variety of potential predictors and controlling factors of fluvial DOC fluxes is discussed. The predictors retained for the final DOC flux models are runoff, slope gradient, land cover, and areal proportions of wetlands. According to the spatially explicit extrapolation of the models, in North America south of 60°N, the total fluvial DOC flux from small catchments (25.8 Mt C a-1, std. err.: 12%) is higher than that from large catchments (19.9 Mt C a-1, std. err.: 10%), giving a total DOC loss of 5.9 Mt C a-1 (std. err.: 78%). As DOC losses in headwaters are not represented in this budget, the estimated DOC loss is rather a minimum value for the total DOC loss within the fluvial network.

Lauerwald, Ronny; Hartmann, Jens; Ludwig, Wolfgang; Moosdorf, Nils

2012-03-01

86

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

NASA Astrophysics Data System (ADS)

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.

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

2010-05-01

87

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

NASA Astrophysics Data System (ADS)

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.

Banham, Steven G.; Mountney, Nigel P.

2013-10-01

88

An Early Warning System for fluvial flooding in the Netherlands  

NASA Astrophysics Data System (ADS)

Fluvial flooding is one of the major natural hazards in the modern world. In a densely populated area, such as The Netherlands, the possibility of flooding of the Rhine and Meuse poses a significant threat to society. There is a clear need for reliable and robust hydrological forecasting. The Water Management Centre for the Netherlands and Deltares have developed an early warning system that uses real-time data provided by a large number of European meteorological and hydrological gauging stations, weather forecasts from three different weather services, and rainfall-runoff and hydraulic models. Data assimilation techniques are used to update both model states and parameter outputs. In addition, a post processing method, quantile regression, is applied to hydrological ensemble output. This presentation will demonstrate the operational flood early warning system (based on Delft-FEWS) applied to these rivers. Recent challenges are, for example, the visualization of uncertainties on deterministic and probabilistic forecasts, the clear communication and visualization of the enormous amount of data available, and snow modelling.

Davids, Femke; Stam, Jasper; Sprokkereef, Eric; van Dijk, Marc

2013-04-01

89

Characterization of fluvial sedimentology for reservoir simulation modeling  

SciTech Connect

This paper presents a critical study of 3D stochastic simulation of a fluvial reservoir and of the transfer of the geological model to a reservoir simulation grid. The stochastic model is conditioned by sand-body thickness and position in wellbores. Geological input parameters-sand-body orientation and width/thickness ratios-are often difficult to determine, and are invariably subject to interpretation. Net/gross ratio (NGR) and sand-body thickness are more easily estimated. Sand-body connectedness varies, depending on the modeling procedure; however, a sedimentary process-related model gives intermediate values for connectedness between the values for a regular packing model and the stochastic model. The geological model is transferred to a reservoir simulation grid by use of transmissibility multipliers and an NGR value for each block. The transfer of data smooths out much of the detailed geological information, and the calculated recovery factors are insensitive to the continuity measured in the geological model. Hence, the authors propose improvements to the interface between geological and reservoir simulation models.

Henriquez, A.; Tyler, K.J.; Hurst, A. (Statoil, Stavanger (NO))

1990-09-01

90

Vegetation roots and fluvial ecomorphodynamics: processes and related timescales  

NASA Astrophysics Data System (ADS)

The biological dynamics of riparian and riverbed vegetation has been recognized to play a fundamental role in fluvial ecomorphodynamics. Contrarily to terrain slopes, the role of vegetation roots in alluvial (non-cohesive) sediment is quite unexplored both at the field and laboratory scales. Hydrologic and biologic growth processes can interact at certain timescales and be determinant to the colonization and successive stabilization of alluvial bedforms. This influences the reworking return period (i.e., the magnitude of impacting floods) of islands and bars in the absence of vegetation and may lead to specific riverbed morphological features. In this paper we first discuss how river hydrology may influence root tropisms and the related growing architecture at the field scale (Pasquale et al., 2012). Different root density vertical distributions can thus be determinant to uprooting and transport processes (Edmaier et al., 2011). Results from a number of laboratory experiments aimed at relating floods intertime and root growth timescales to uprooting statistics are then presented (Perona et al., 2012). We show the biomass selection mechanism operated by flow disturbances on riverbed vegetation, and discuss :i) the related impact that this process may have to select young vegetation in and among species (Crouzy and Perona, 2012; ii) two exemplary vegetation patterns that have been observed in rivers with converging boundaries and ephemeral streams. This study is a first step to better understand and model the sediment stabilization mechanism by vegetation roots in the equations of morphodynamics.

Perona, P.

2012-04-01

91

Borehole flowmeter application in fluvial sediments: Methodology, results, and assessment  

SciTech Connect

In many situations, inadequate design or performance of ground-water remediation systems is the result of underestimation of aquifer hydraulic heterogeneity, and in particular, the vertical variation of hydraulic conductivity which plays an important role in contaminant migration. Described herein are applications of the electromagnetic (EM) borehole flowmeter to fluvial sediments in Louisiana and South Carolina. The direction of natural vertical flow in the test aquifers was defined easily, and short pumping tests enabled the calculation of hydraulic conductivity profiles for each test well. The results correlated well with other information obtained independently, including natural gamma logs, driller`s logs and a hydraulic conductivity profile based on grain size analysis. Large variations in hydraulic conductivity over short vertical and horizontal distances were documented. Tests in gravel-packed wells suggested that flowmeters produce misleading data for a variety of reasons in such situations. Among other things, an annulus of high permeability around a well screen allows flow to bypass the meter, and the phenomenon is amplified by high pumping rates. The resulting error is displayed as an erroneous high permeability zone at the top of the well screen. This observation deserves further study. In its present form the EM flowmeter is awkward to handle on a routine basis. However, none of the present design flaws preclude its effective use.

Boman, G.K. [Auburn Univ., AL (United States). Dept. of Civil Engineering; Molz, F.J.; Boone, K.D. [Clemson Univ., SC (United States). Dept. of Environmental Systems Engineering

1997-05-01

92

Fluvial Placement of Radioactive Contaminants a Weldon Spring Case Study  

SciTech Connect

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.

Meier, J.

2002-02-26

93

The origin of dose distributions in fluvial sediments, and the prospect of dating single grains from fluvial deposits using optically stimulated luminescence  

Microsoft Academic Search

We examine the causes of the asymmetric distributions of dose observed from measurements of the optically stimulated luminescence emitted by small aliquots of fluvial quartz, and deduce that the asymmetry arises as a result of samples being composed of a mix of mainly well bleached grains with grains that were effectively unbleached at the time of deposition. We demonstrate that

J. M Olley; G. G Caitcheon; R. G Roberts

1999-01-01

94

¿RAZÕN DE AMOR O DENUESTOS DEL AGUA Y EL VINO?  

Microsoft Academic Search

Las dificultades que plantea para su clasificación genérica, su filiación lingüística y su interpretación estética hacen de la Razón de amor con los Denuestos del agua y el vino un apasionante enigma de la poesía medieval castellana; y el problema central en torno al cual parecen gravitar todas esas dificultades es la aparente dicotomía y falta de unidad de la

Arsenio Pacheco

1974-01-01

95

Climate Controls on Sediment Discharge in Selected Fluvial Systems in Indonesia  

NASA Astrophysics Data System (ADS)

Sediment discharge was evaluated in selected rivers in Indonesia where catchment basin size, relief, and gradient are somewhat similar, but where tectonic setting, bedrock lithology, and atmospheric circulation and rainfall, are variables. Rivers were studied in humid to perhumid regions where the Intertropical Convergence Zone (ITCZ) is relatively stable and rainfall exceeds evapotranspiration for all or most months of the year (Sumatra, Borneo, Seram, and Irian Jaya). In contrast, fluvial sediment discharge was evaluated in rivers in Timor where 85 percent of all rainfall occurs during a four-month rainy season (dry subhumid climate) in response to the passage of the ITCZ. Stream sampling was conducted for solid suspended sediment concentrations, solute concentrations, and pH. In addition, the nature of stream channels (meandering or braided), streambed materials, the degree and source of estuarine fill, the degree of delta formation, and the nature of coastlines were used to evaluate fluvial sediment discharge. Very low sediment concentrations (10 mg/l suspended and 10mg/l solute) in rivers in the perhumid to humid regions are indicative of a very low fluvial sediment discharge. The absence of fluvially derived bed loads, river mouth deltas, the lack of fluvial fill of estuaries, and mud-dominated coastal zones are consistent with this observation. In contrast, very high sediment concentrations (2100 mg/l suspended and 340 mg/l dissolved) during rainy season discharge in dry-subhumid regions (Timor) are indicative of very high sediment discharge in dry subhumid climates. Coarse-grained braided streams, the complete fluvial fill of estuaries, the formation of river-mouth deltas, cobbles transported to the coast, and coarse-grained beaches are consistent with this observation. All factors indicate that fluvial sediment discharge is exceedingly low in humid and perhumid areas where denudation is dominated by chemical weathering, whereas fluvial sediment discharge is exceedingly high in relatively dry seasonal climates where denudation appears to be primarily controlled by both chemical and mechanical processes. The dominant variable affecting fluvial sediment discharge among the islands of Indonesia, therefore, appears to be the degree of seasonality in rainfall regardless of tectonic setting.

Cecil, C. B.

2004-12-01

96

An unnamed fluvial valley system formed under different climates at Xanthe Terra, Mars  

NASA Astrophysics Data System (ADS)

Analyzing an unnamed fluvial system (at 5.2N 301.4E) in Xanthe Terra on Mars for the first time, the following chronology could be reconstructed. The first period of the fluvial erosion of the area produced channels with higher drainage density than later events, but some resurfacing after this period erased these early, probably interconnected tributary systems and left behind only separate channel sections with eroded appearance. In the second period of fluvial erosion three deep and obvious channels were formed. In a third period, the main inlet to the terminal crater was eroded even more heavily. The last two episodes produced two different, characteristic cross sectional and longitudinal profiles: (1) narrow, shallow and nearly straight profiles, and (2) a wider, deeper and somewhat convex shaped profile. These two profile shapes resemble to other fluvial systems' in the Xanthe Terra region. The existence of these two different types of channel morphology suggests the change in the erosional process could be at least regional and probably related to the change of fluvial erosion's style on Mars forced by climatic changes.

Kereszturi, Akos

2013-09-01

97

The Pleistocene climate-controlled fluvial sedimentary record in the Be?chatów mine (central Poland)  

NASA Astrophysics Data System (ADS)

Sedimentological analyses of fluvial formations in the Be?chatów mine have yielded results that have more than regional significance. They concern the reaction of rivers to climatic changes in the Pleistocene. Changes in river geometry and their depositional records are examined from two fluvial formations. These formations represent different times, but show similar palaeoenvironmental changes. Cool temperate climate conditions resulted in meandering (or anastomosing) river sedimentation, which was controlled by equalized precipitation and by a well-developed vegetation cover. Cold periglacial climate conditions resulted in braided river sedimentation immediately before the Glacial Maximum, with high discharges and a high sediment load. The palaeoclimatic and palaeohydrologic analyses of the Weichselian fluvial deposits in Be?chatów provide additional information to that from similar studies in Germany and the Netherlands, thus jointly resulting in a consistent palaeogeographic model of western-middle Europe.

Zieli?ski, Tomasz

2007-01-01

98

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

PubMed

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

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

99

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

NASA Astrophysics Data System (ADS)

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.

Assine, Mario Luis; Silva, Aguinaldo

2009-12-01

100

Effect of Subsidence Styles and Fractional Diffusion Exponents on Depositional Fluvial Profiles  

NASA Astrophysics Data System (ADS)

Diffusion transport models provide a reliable means of modeling the sediment transport in fluvial depositional systems. In a typical application, the steady state diffusion prediction for a constant input flux into a subsiding system predicts a fluvial surface with a well define concaved up profile. Often in experimental systems, however, observed profiles are flatter(less concaved) than those predicted by diffusion. A possible reason is that heterogeneities, which can scale up to the size of the system, lead to so-called anomalous diffusion; a phenomenon more appropriately modeled with a fractional diffusion equation. In recent work two of the authors (VRV & CP) investigated how well a fractional (anomalous) diffusion treatment fits observed steady state experimental depositional fluvial profiles. In the case of a piston subsidence it was observed that a fractional diffusion equation with the sediment flux modeled by a right-hand Caputo derivative could successfully match observed fluvial profiles. In particular the fractional diffusion model was able to predict flatter more realistic profiles than the normal diffusion model. The current effort extents the previous work in three ways. First we propose a simple physically description of anomalous diffusion and show how it can be easily related to the right-hand Caputo flux model. Secondly we investigate how different subsidence styles, in combination with a fractional diffusion model, might influence the shape of the steady-state fluvial depositional profile. Of particular note is the observation that a right-hand Caputo model in a region with a hinge subsidence can predict fluvial profiles with concaved down profiles. Finally, through recently available data we explore the possible connections between the fractional diffusion models and experimental depositional systems.

Voller, V. R.; Paola, C.; Hajek, L.

2010-12-01

101

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

NASA Astrophysics Data System (ADS)

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.

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

2007-04-01

102

Three-dimensional geometry of fluvial reservoir sands: steam-drive case study  

SciTech Connect

The three-dimensional geometry of fluvial sands in South Belridge heavy oil field was investigated as part of an Enhanced Oil Recovery study. It was shown that only close-spaced well data are sufficient to define the sand-body geometries and heterogeneities of multichannelled fluvial systems. Reservoir flow-unit patterns cannot necessarily be correctly delineated by isolated vertical sequence analysis. Wireline logs from 19 wells and conventional cores from seven wells in a 10-ac (660 ft x 660 ft) pattern were correlated in detail, using additional input from sedimentology, steam-flow patterns, and reservoir flow-unit continuity.

McPherson, J.G.; Miller, D.D.

1989-03-01

103

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

Microsoft Academic Search

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

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

2005-01-01

104

Unconfined flow deposits in distal sectors of fluvial distributary systems: Examples from the Miocene Luna and Huesca Systems, northern Spain  

Microsoft Academic Search

Thin sheet sandstone beds in a continental succession may be the products of unconfined overbank flow or deposition in lacustrine environments. In the distal parts of fluvial distributary systems these two settings may be intercalated, recording fluctuations in lake level in response to climatic changes. Field studies of the Luna and Huesca fluvial distributary systems in the Miocene of the

J. A. Fisher; G. J. Nichols; D. A. Waltham

2007-01-01

105

Precambrian fluvial deposits: Enigmatic palaeohydrological data from the c. 2–1.9 Ga Waterberg Group, South Africa  

Microsoft Academic Search

Precambrian fluvial systems, lacking the influence of rooted vegetation, probably were characterised by flashy surface runoff, low bank stability, broad channels with abundant bedload, and faster rates of channel migration; consequently, a braided fluvial style is generally accepted. Pre-vegetational braided river systems, active under highly variable palaeoclimatic conditions, may have been more widespread than are modern, ephemeral dry-land braided systems.

Patrick G. Eriksson; Adam J. Bumby; Jacobus J. Brümer; Markus van der Neut

2006-01-01

106

Precambrian fluvial deposits: Enigmatic palaeohydrological data from the c. 2 1.9 Ga Waterberg Group, South Africa  

Microsoft Academic Search

Precambrian fluvial systems, lacking the influence of rooted vegetation, probably were characterised by flashy surface runoff, low bank stability, broad channels with abundant bedload, and faster rates of channel migration; consequently, a braided fluvial style is generally accepted. Pre-vegetational braided river systems, active under highly variable palaeoclimatic conditions, may have been more widespread than are modern, ephemeral dry-land braided systems.

Patrick G. Eriksson; Adam J. Bumby; Jacobus J. Brümer; Markus van der Neut

2006-01-01

107

Diagenesis of Eolian and fluvial feldspathic sandstones, Norphlet formation (upper Jurassic), Rankin County, Mississippi, and Mobile County, Alabama  

Microsoft Academic Search

Norphlet sandstones in seven cores from Mississippi and Alabama are arkoses and subarkoses deposited in eolian-dune, interdune, and fluvial environments. Similar to the deeply buried (> 5 km) Tertiary feldspathic sandstones of the Gulf basin, all detrital plagioclase that survived dissolution has been albitized. Fluvial red sandstone lost all initial porosity by the introduction of preburial pedogenic calcite and compaction.

L. S. Land; L. E. Mack

1987-01-01

108

Volcanic or Fluvial: Comparison of an Ascraeus Mons, Mars, Braided and Sinuous Channel with Features of the 1859 Mauna Loa Flow and Mare Imbrium Flows  

NASA Astrophysics Data System (ADS)

A channel on Ascraeus Mons, previously suggested to indicate fluvial activity, is shown in its entirety. Distal portions indicate that this feature is of a volcanic origin despite similarities in the proximal sections to fluvial features.

Bleacher, J. E.; de Wet, A. P.; Garry, W. B.; Zimbelman, J. R.; Trumble, M. E.

2010-03-01

109

Young Quartenary Paleofloods in the Sinai Mts., Egypt - Reconstruction of changes in a fluvial regime using Wadi fillings and corresponding fluvial fan sediments of the South Sinai Footplain  

NASA Astrophysics Data System (ADS)

The mapping, characterisation and dating of wadi sediment fillings in arid regions offer a good possibilities to reconstruct certain climatical and environmental components. In Southern Sinai in Egypt, an arid region with current precipitation < 20 mm/a, such sediments have been described and intensively investigated in the biggest wadi system, the Wadi Feiran and its tributaries. However, large wadi systems get influenced by many processes which complicate the final interpretation of sediments and according processes. Thus, we studied the Wadi Timan and several neighboured valleys, important wadi systems in the South of the Sinai Mountains near El Tor. Fluvial sediments fill the sides of the valleys up to 50 m. The fillings are cut by a deep channel which is also used by the sparse modern flood events. The fluvial filling change drastically within the vertical profile, so three main units can be distinguished. The bottom unit (1) consist of clearly laminated coarse sands and gravels with angular blocks probably represent short flood events in the sense of a muddy flow along the valley. The middle unit (2) consist of fine stratified layers of silt and sand. This unit, which has a large distribution also in the surrounding of the Wadi Timan, probably represents alluvial loess similar of that described in literature in the Wadi Feiran. The top unit (3) is characterised by fluvially transported sands and gravels with interbeddings of fine silt rich layers similar to those of unit (2). The sediments are partly cemented by carbonates and/or gypsum. At the valley end towards the West, several generations of alluvial fans have formed. The stratification starts rather flat at the bottom of the fan and gets steeper towards the top indicating gradual accumulation. The large difference between the units 1-3 and the several generations of alluvial fans offer a rich geoarchive to reconstruct changes in the fluvial system of the past, which might be a consequence of climate changes.

Voelkel, J.; Leopold, M.; Huerkamp, K.; Huber, J.; Murrey, A.; Grunert, J.

2009-04-01

110

Intensity and spatio-temporal variability of fluvial sediment transfers in an Arctic-oceanic periglacial environment in northernmost Swedish Lapland (Latnjavagge catchment)  

Microsoft Academic Search

Intensity and spatio-temporal variability of fluvial sediment transfers and mechanical fluvial denudation were analyzed in the periglacial Latnjavagge catchment (9km2; 950–1440m a.s.l.; 68.20N, 18.30E) in Arctic-oceanic northernmost Swedish Lapland. The present-day rates of fluvial sediment transfer are low. The mean annual mechanical fluvial denudation rate at the inlet of lake Latnjajaure, as calculated after five years of process monitoring (2000–2004),

Achim A. Beylich; Olga Sandberg; Ulf Molau; Susan Wache

2006-01-01

111

ÉVOLUTION HISTORIQUE DE LA MORPHO- GENÈSE ET DE LA DYNAMIQUE FLUVIALE D'UNE RIVIÈRE MÉDITERRANÉENNE : L'EXEMPLE DE LA MOYENNE DURANCE (FRANCE DU SUD-EST)  

Microsoft Academic Search

Fluvial morphogenesis evolu- tion of a mediterranean river: The example of the Durance fluvial system (south-eastern France). Based on stratigraphical and sedi- mentological analysis of floodplain sedi- ments, aerial photographies, ancient maps and texts preserved in local archives, the historical evolution of the Durance fluvial system (south-eastern France) is recon- structed. The amount of data allows to sug- gest a

Cécile MIRAMONT; Maurice JORDA; Robert Schuman; Georges PICHARD

112

Simulating the Fluvial Erosion of Fine-Grained River Banks  

NASA Astrophysics Data System (ADS)

River bank erosion is the product of a suite of specific processes that together contribute significantly to the sediment yielded from river catchments. Many studies have emphasised that hydraulic erosion of bank-toe materials may exert a dominant influence on the long term rate of river bank retreat. Fluvial bank erosion rates are normally quantified using an excess shear stress model of the form E = k(?b-?c)a, where E is the erosion rate per unit time and unit bank area, ?b is the boundary shear stress applied by the flow, k and ?c are erodibility parameters (erodibility coefficient, k, and critical shear stress, ?c), and a is an empirically derived exponent (equated to unity in bank erosion studies). This model has the advantage of simplicity, but in practice difficulties in estimating the values of the erodibility and shear stress parameters seriously inhibit its accuracy. We are seeking to improve the parameterization of the excess shear stress model through the use of field measurements and analytical modelling, at field sites on the Mekong River in Laos. Specifically, ?b is estimated using a new model [Kean and Smith, 2006, J. Geophys. Res., 111(4), F04009, doi:10.1029/2006JF000467] of flow over irregular bank topography. Data from our study sites indicate that the form roughness induced by natural topographic bank features (slumps, embayments, etc) is a major component of the spatially-averaged total shear stress, with the skin friction component (i.e, ?b) typically an order of magnitude less than the total stress. This indicates that previous bank erosion investigations, that employ estimates of the total shear stress, may grossly misparameterize the true value of ?b. To estimate ?c, we have employed a Cohesive Strength Meter [CSM, Tolhurst et al., 1999, Estuarine, Coastal & Shelf Sci., 49, 281-294], a jet-testing device that is normally used in studies of the stability of cohesive sediments on inter-tidal flats, but which has not previously been employed in the context of river bank studies. Our data show that values of ?c are typically of the order of 1 Pa, again indicating that previous studies may have over-estimated the true critical stress. Moreover, compared to conventional jet-testing devices, the portability and small size of the CSM's sampling chamber, together with the speed of individual tests, allows the collection of large numbers of replicate samples within discrete sedimentary horizons, such that the inherent natural variability of each bank material horizon can be defined. This has allowed us to modify the excess shear stress erosion model to include a probabilistic component associated with the measured statistical distribution of ?c for a specific bank-toe material. We have used our data to estimate bank erosion rates for a range of flow discharges, with annual erosion rates subsequently determined by integration across the predictable annual (monsoonal) flow regime. To assess the predictive ability of our model we have compared annual rates of bank-toe retreat (assumed to be a good proxy of bank retreat rates) with estimates of bank retreat derived from analysis of aerial photographs and satellite imagery.

Darby, S. E.; Sarkkula, J.; Koponen, J.; Kummu, M.

2007-12-01

113

Dynamique sédimentaire actuelle d'un système fluvial méditerranéen: l'Agly (France)  

Microsoft Academic Search

The purpose of this study is to investigate the mechanical and chemical erosion rates in the Agly catchment (1 045 km2) in order to estimate the whole sediment budget of a Mediterranean fluvial system. The climate of the catchment is characterized by a marked contrast between dry and humid conditions, with the occurrence of heavy downpours during only a few

Pierre Serrat

1999-01-01

114

Summer Microhabitat Use of Fluvial Bull Trout in Eastern Oregon Streams  

Microsoft Academic Search

The management and recovery of populations of bull trout Salvelinus confluentus requires a comprehensive understanding of habitat use across different systems, life stages, and life history forms. To address these needs, we collected microhabitat use and availability data in three fluvial populations of bull trout in eastern Oregon. We evaluated diel differences in microhabitat use, the consistency of microhabitat use

Robert Al-Chokhachy; Phaedra Budy

2007-01-01

115

Fluvial depositional systems of Carrizo-Upper Wilcox in south Texas  

SciTech Connect

In the Rio Grande embayment of south Texas, the Carrizo-upper Wilcox interval (Eocene) consists of two sand-rich coastal plain fluvial depositional systems that grade basinward into several deltaic complexes. The bedload channel system is dominated by multi-story, multi-lateral, fluvial, channel-fill sandstones. This system is typically > 90% sandstone. Shales are thin and laterally discontinuous, the remnants of abandoned channel fills. Bedload channel sandstones dominate the major fluvial axes and form the depositional framework of the interval. The mixed alluvial system consists of a more typical suite of coastal plain facies. Mixed-load channel-fill sandstones tend to be isolated and surrounded by overbank shales and thin sandstones. Crevasse splay and lacustrine facies occur in the flood-plain area. Total-interval isopach patterns, sandstone geometries, and depositional systems distributions indicate that fluvial sediment input was converging upon the embayment from the west, northwest, and north. Economically, the Carrizo-upper Wilcox of south Texas has a three-fold significance. The updip Carrizo sandstone is a major source of fresh groundwater, includes several large oil fields, and also contains deposits of uranium minerals. The downdip upper Wilcox trend is an area of active hydrocarbon exploration.

Hamlin, H.S.

1983-09-01

116

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

Microsoft Academic Search

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

J. Lorenz

1987-01-01

117

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

Microsoft Academic Search

This paper begins to differentiate the major drivers and chronology of erosion and aggradation in the fluvial and fluviokarst landscapes of the southern and central Maya Lowlands. We synthesize past research on erosion and aggradation and add new data from water, soils, radiocarbon dating, and archaeology to study the quantity, timing, and causes of aggradation in regional landscape depressions. Geomorphic

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

2008-01-01

118

Assessing the reproducibility and accuracy of optical dating of fluvial deposits  

Microsoft Academic Search

Optical dating is increasingly being applied to fluvial deposits to derive rates of geomorphological and sedimentary processes. Partial bleaching of the water-transported sediment grains is a common occurrence, however, and creates problems in deriving burial ages. This paper presents results from optically stimulated luminescence (OSL) dating performed on samples collected from discrete reaches of palaeochannels of the Klip River, South

H. Rodnight; G. A. T. Duller; A. G. Wintle; S. Tooth

2006-01-01

119

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

Microsoft Academic Search

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

Mary J. Kraus; Larry T. Middleton

1987-01-01

120

Equivalent dose distribution analysis of Holocene eolian and fluvial quartz sands from Central Oklahoma  

Microsoft Academic Search

Holocene quartz sands were collected from fluvial terrace deposits and eolian dune deposits adjacent to the North Canadian and Cimarron Rivers and their tributaries in Central Oklahoma. Single aliquot regenerative dose optically stimulated luminescence techniques were employed to generate equivalent dose (ED) distribution histograms for each sample. We hypothesize that the ED distributions are convolutions of the distribution arising from

Kenneth Lepper; Niels Agersnap Larsen; Stephen W. S McKeever

2000-01-01

121

Distinguishing Long-Term Controls on Fluvial Architecture in the Lance Formation, Bighorn Basin, Wyoming  

Microsoft Academic Search

Allogenic processes are considered a prime control on the stratigraphic distribution of channel bodies, however, recent studies have indicated that autogenic stratigraphic organization may occur within fluvial systems on basin- filling time scales (105-106 years). Groupings or clusters of closely-spaced channel bodies can be produced by several different mechanisms, including both allogenic and autogenic processes. Commonly, sand- dominated intervals in

J. L. McHarge; E. A. Hajek; P. L. Heller

2007-01-01

122

Fluvial transport of bovid long bones fragmented by the feeding activities of hominins and carnivores  

Microsoft Academic Search

This study explores the hydraulic transportability of bovid long bone fragments created through hominin and carnivore carcass consumption in order to determine the effect of fluvial transport on the incidences of hominin- and carnivore-induced bone surface modifications. Transportability was determined using an oval race track flume and 311 long bone fragments from modern control collections of hominin- and carnivore-modified bone.

Michael C. Pante; Robert J. Blumenschine

2010-01-01

123

Evidences of Paleoearthquakes in Palaeolithic settlements within fluvial sequences of the Tagus Basin (Madrid, Central Spain)  

Microsoft Academic Search

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

Pablo G. Silva; M. A. Rodríguez Pascua; R. Pérez López; J. L. Giner Robles; E. Roquero; F. Tapias; M. López Recio; I. Rus; J. Morin

2010-01-01

124

Physical and human influences on fluvial water quality in the Tagus river catchment, Portugal  

Microsoft Academic Search

Rivers are important resources of drinkable water, ecosystems with a high biologic potency and places of entertainment. Water quality at the catchment scale depends on climate, geology, geomorphology, soils and mainly of land use and land cover. Different activities such as agriculture, livestock, industrial and urban drains have promoted the deterioration of the fluvial water quality. The announced climate changes,

A. Nunes

2009-01-01

125

Reconstructing multi-decadal variations in fluvial flood risk using atmospheric circulation patterns  

NASA Astrophysics Data System (ADS)

Objective weather types are used to reconstruct fluvial floods since the 1870s. Flood frequencies but not magnitudes are reproduced at various spatial scales. Flood rich episodes are found in 1908-1934, 1977-1988 and from 1998 onwards. Key weather types show no change in frequency, persistence, or rain since 1930s. The source of atmospheric pressure data affects reconstructed flood indices.

Wilby, Robert L.; Quinn, Nevil W.

2013-04-01

126

Effects of earthquake and cyclone sequencing on landsliding and fluvial sediment transfer in a mountain catchment  

Microsoft Academic Search

Patterns and rates of landsliding and fluvial sediment transfer in mountain catchments are determined by the strength and location of rain storms and earthquakes, and by the sequence in which they occur. To explore this notion, landslides caused by three tropical cyclones and a very large earthquake have been mapped in the Chenyoulan catchment in the Taiwan Central Range, where

Guan-Wei Lin; Hongey Chen; Niels Hovius; Ming-Jame Horng; Simon Dadson; Patrick Meunier; Max Lines

2008-01-01

127

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

Microsoft Academic Search

South America delivers more freshwater runoff to the ocean per km2 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

Carol P. Harden

2006-01-01

128

Optically Stimulated Luminescence Analysis on the Modern Debris and Fluvial Deposits  

Microsoft Academic Search

Continuous technological development in luminescence dating techniques facilitates luminescence dating method to be applied widely to the sediments from various geomorphic settings, such as completely bleached sediments from aeolian and shore face environments or even partially bleached sediments from fluvial and debris environments. Burial ages since sediments exposed to the last daylight are supposed to be determined, and hence it

K. Jaiswal; Ya-Wen Chen; Yue-Gau Chen; Yu-Nong Lin

129

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

Microsoft Academic Search

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

A. Matoshko; P. Gozhik; V. Semenenko

2009-01-01

130

River Restoration Through Bank Stabilization Using FLUVIAL12: Case Study of Raia River, Ipoh, Perak  

Microsoft Academic Search

River restoration defined as the return of a degraded river ecosystem to a close approximation of its remaining natural potential. Many types of practices such as dam removal, levee breaching, modified flow control, bio-engineering methods for riverbank erosion control are useful on channel construction. A tension exists between restoring natural fluvial processes and ensuring stability of the completed project. Sediment

AHMAD DARUS; Jalan Sultan Salahuddin; AMINUDDIN AB; NOR AZAZI ZAKARIA; ROZI ABDULLAH; CHANG CHUN KIAT

131

The Late Quaternary fluvial dynamcis of the Marneuli depression in eastern Georgia  

NASA Astrophysics Data System (ADS)

The Marneuli depression, located in the southeastern part of the Republic of Georgia, is a tectonic basin at the transition of the Lesser Caucasus Mountains towards the Transcaucasian depression in the north. It is filled with several decameters of loose Quaternary deposits of marine, fluvial, colluvial and aeolian origin, and crossed by the lower reaches of five rivers that left several meters of fluvial sediments along their courses. Stratigraphic, sedimentologic and chronologic investigations of these naturally outcropped sediments along two of the rivers (Algeti, Shulavericai) demonstrate a strong fluvial dynamics during the Holocene, leading to the formation of several morphological terrace levels encompassing different time slices. Causes of this active dynamics can only be assumed yet, but a comparison with palaeoclimatic and archaeologic data possibly hints at a mostly climatic trigger. Furthermore, morphologic and stratigraphic data indicate a young westward shift of the course of the Kura river, the main receiving stream of all rivers of the Marneuli depression. This shift is thought to be caused by recent tectonic activity along the western margin of the Kura thrust-and-fold-belt, and had probably also influenced the fluvial dynamics of the investigated rivers by a change of their erosion base.

von Suchodoletz, H.; Faust, D.; Menz, M.

2012-04-01

132

Paleocurrent and fabric analyses of fluvial conglomerates of the Paleogene Noda Group, northeast Japan  

Microsoft Academic Search

Clast-supported fluvial conglomerates of the Paleogene Noda Group, northeast Japan, consist of two contrasting formations; the lower Minato Formation comprising dominantly acidic volcanic gravels, and the conformably overlying Kuki Formation of Mesozoic basement gravels. Crudely horizontally stratified or massive sheets of conglomerates, facies Gm, comprise most of the sediments of both the formations, and show no abrupt lateral changes of

Koji Yagishita

1997-01-01

133

Paleobiology and paleoecology of an arid–semiarid Miocene South American ichnofauna in anastomosed fluvial deposits  

Microsoft Academic Search

Miocene deposits of the Toro Negro Formation in La Rioja province, Argentina, host a rich vertebrate and invertebrate ichnofauna. Trace fossils are recorded from the lower part of the Lower Member of the Toro Negro Formation at Quebrada de La Troya. This succession consists of sandstone, intraformational breccia, mudstone and few conglomerate deposited in sandy anastomosing fluvial systems developed under

Verónica Krapovickas; Patricia L. Ciccioli; M. Gabriela Mángano; Claudia A. Marsicano; Carlos O. Limarino

2009-01-01

134

Formation and preservation of a Tertiary to Pleistocene fluvial gold placer in northwest British Columbia  

Microsoft Academic Search

A unique longitudinal section through 2km of a fluvial placer deposit in northwest British Columbia provides an excellent sedimentologic and stratigraphic record of the placer sequence and insight into the Pleistocene history of the region. The section is exposed as a result of long-term, open pit, placer gold mining along Otter Creek. Deposition of the auriferous gravels is believed to

Victor M Levson; Heather Blyth

2001-01-01

135

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

National Technical Information Service (NTIS)

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 rain...

V. C. Gulick J. Dohm K. Tanaka T. Hare

2000-01-01

136

Characterizing physical habitats in rivers using map-derived drivers of fluvial geomorphic processes  

NASA Astrophysics Data System (ADS)

New understanding of fluvial geomorphological processes has successfully informed flood mitigation strategies and rehabilitation schemes in recent years. However well established geomorphological assessments are location-specific and demanding in terms of resource and expertise required, and their routine application for regional or national river characterization, although desirable, is unlikely at present. This paper proposes a framework based on GIS procedures, empirical relationships and the self organized map for the analysis and classification of map-derived drivers of fluvial morphological processes. The geomorphic controls analysed are: channel gradient and hydrology, specific stream power, river order and floodplain extent. The case study is a gravel bed river in England. Using the self organized map, we analyse patterns of these controls along the river longitudinal profile and identify clusters of similar configuration. The reciprocal relationships that emerge amongst the geomorphic controls reflect the hierarchical nature of fluvial systems and are consistent with the current theoretical understanding of fluvial processes. Field observations from the River Habitat Survey are used to prove the influence of geomorphic drivers on reach-scale morphological forms. Six clusters are identified which describe six distinctive channel types. These proved to be characterized by distinctive configurations of geomorphic drivers and specific sets of physical habitat features. The method successfully characterizes the notable transitions in channel character along the river course. The framework is suitable for regional or national scale assessments through automatic GIS and statistical procedures with moderate effort.

Bizzi, Simone; Lerner, David N.

2012-10-01

137

Evaporite dissolution and pore fluid pressure as controls on diagenesis in complex fluvial HPHT reservoirs  

Microsoft Academic Search

Continental depositional systems influenced by salt movement are characterized by rapid lateral and vertical facies changes that are difficult to predict at reservoir scale. The Triassic Skagerrak Formation of the Central North Sea, UK is an excellent example of how the onset of Permian Zechstein salt movement strongly influenced the thickness, stratigraphy and facies distributions of this large fluvial system.

Binh Nguyen; Stuart Jones; Neil Goulty; Neil Grant; Jamie Middleton

2010-01-01

138

Infiltration in Unsaturated Layered Fluvial Deposits at Rio Bravo: Macroscopic Anisotropy and Heterogeneous Transport  

Microsoft Academic Search

and Yeh, 1996; Roth and Hammel, 1996; Birkholzer and Tsang, 1997) suggest that in unsaturated media, An infiltration and dye transport experiment was conducted to the macrodispersivity for the equivalent homogeneous visualize flow and transport processes in a heterogeneous, layered, medium, which is in general anisotropic, increases with sandy-gravelly fluvial deposit adjacent to Rio Bravo Boulevard in Albuquerque, NM. Water

R. J. Glass; J. R. Brainard; T.-C. J. Yeh

2005-01-01

139

Variability of the fluvial thermal process during ice breakups of the Lena river (Siberia)  

NASA Astrophysics Data System (ADS)

A 4-years observation program was initiated to quantify the variability of the fluvial thermal erosion during the ice breakups of the Lena River in Central Siberia. Parameters affecting fluvial thermal erosion have been collected in the middle valley near Yakutsk city where active fluvial thermal erosion on frozen islands has been recorded. The heads of islands undergo strong erosion with mean values of 12 m per year and maximal values reaching 40 m. The careful analysis of the annual data shows a high variability of the erosion rate, mostly due to the variability of the water stream temperature and to the duration and timing of the flood season. A laboratory simulation was proposed to quantify the potential impact of the recent global warming, by means of an increase of the water stream temperature. A hydraulic channel in a cold chamber simulate the ground thawing produced by heat transfer from the flow of water through the frozen ground; followed by mechanical transport of the thawed sediments. The measured increase up to 2°C of the water stream temperature could alone multiply the erosion rate by 16% and explains the acceleration of the mobility of fluvial islands on the Lena river.

Costard, Francois; Gautier, Emmanuele; Fedorov, Alexander; Konstantinov, Pacha; Dupeyrat, Laure

2013-04-01

140

Pleistocene tectonics inferred from fluvial terraces of the northern Upper Rhine Graben, Germany  

Microsoft Academic Search

This study of fluvial terraces of the River Rhine and tributaries aims to search for indications of Pleistocene tectonic activity. The study area includes the northern Upper Rhine Graben (URG), the Mainz Basin and the adjacent Rhenish Massif with the Middle Rhine Valley. High rates of Quaternary surface processes, large amount of human modifications, relatively slow tectonic deformation and presently

Gwendolyn Peters; Ronald T. van Balen

2007-01-01

141

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

Microsoft Academic Search

Beaver habitation is an important component of many fluvial landscapes that can impact a variety of hydrologic, geomorphic, and ecologic processes. Beaver damming, via long term valley aggradation, is thought to be important to the postglacial geomorphic evolution of many smaller mountain stream networks in the western United States. Loss of beaver dams can also cause rapid channel incision. Although

L. Persico; G. Meyer

2008-01-01

142

3. Fluvial Processes in Puget Sound Rivers and the Pacific Northwest  

Microsoft Academic Search

The variability of topography, geology, climate, vegetation, and land use in the Pacific Northwest creates considerable spatial and temporal variability of fluvial processes and reach-scale channel type. Here we identify process do- mains of typical Pacific Northwest watersheds and examine local physi- ographic and geologic controls on channel processes and response potential in the Puget Sound region. We also review

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

143

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

SciTech Connect

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.

Wescott, W.A. (Amoco Production Company, Houston, TX (United States))

1993-07-01

144

The origin and timing of fluvial activity at Eberswalde crater, Mars  

NASA Astrophysics Data System (ADS)

The fan deposit in Eberswalde crater has been interpreted as strong evidence for sustained liquid water on early Mars with a paleolake formed during the Noachian period (>3.7 Gy). This location became a key region for understanding the Mars paleo-environment. Eberswalde crater is located 50 km north of the rim of the 150 km diameter crater Holden. Stratigraphic relationships and chronology obtained using recent Mars Express High Resolution Stereo Camera and Mars Reconnaissance Orbiter Context Camera images show that Eberswalde fluvial activity crosscuts Holden ejecta and thus postdates Holden crater, whose formation age is estimated from crater counts as Late Hesperian (˜3.5 Gy, depending on models). Fluvial modeling shows that short term activity (over several years to hundreds of years) involving dense flows (with sediment:water ratio between 0.01 and 0.3) may be as good an explanation of the fluvial landforms as dilute flow over longer durations. Modeling of the thermal effect of the Holden impact in the Eberswalde watershed is used to evaluate its potential role in aqueous activity. The relative timing of the Holden impact and Eberswalde's fan is a constraint for future studies about the origin of these landforms. Holden ejecta form a weak and porous substrate, which may be easy to erode by fluvial incision. In a cold climate scenario, impact heating could have produced runoff by melting snow or ground ice. Any attempt to model fluvial activity at Eberswalde should take into account that it may have formed as late as in the Late Hesperian, after the great majority of valley network formation and aqueous mineralization on Mars. This suggests that hypotheses for fan formation at Eberswalde by transient and/or localized processes (i.e. impact, volcanism, unusual orbital forcing) should be considered on a par with globally warmer climate.

Mangold, N.; Kite, E. S.; Kleinhans, M. G.; Newsom, H.; Ansan, V.; Hauber, E.; Kraal, E.; Quantin, C.; Tanaka, K.

2012-08-01

145

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

SciTech Connect

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.

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

1983-03-01

146

Metodologia de Sensoriamento Remoto No Monitoramento de Modificacoes No Canal Fluvial E Atualizacao de Cartas Nauticas (Methodology of Remote Sensing for Monitoring Modifications in the Fluvial Channel and Updating Nautical Charts).  

National Technical Information Service (NTIS)

A methodology of remote sensing is proposed for monitoring the fluvial morphology of a section of the Solimoes River (Brazil), as support for cartographic updating of nautical charts. In developing of the methodology, the following material was used; LAND...

W. Santosdealmeida

1989-01-01

147

Impacts of dams on the geomorphodynamics of fluvial systems - Complex system response?  

NASA Astrophysics Data System (ADS)

In Europe, for more than 5.000 years humans impact fluvial systems in various ways, e.g. also through building dams. These constructions change the interdependencies between the components of the fluvial system. 'Natural (fluvial) systems' are scarce and humans play an active and major role in changing river systems. In return the geomorphic response of fluvial systems like channel bed degradation downstream or sedimentation upstream of dams also affects the human system which again leads to 'human responses' such as building (or abandoning) river engineering structures. Geomorphic response or geomorphic system behavior can change and feature linear or nonlinear/complex behavior depending on the internal systemic structure and system history. The study area, the 'Kaja' River watershed is located in the Eastern part of the Bohemian Massif in Austria (Europe) and drains into the 'Thaya' River which builds the northern border to the Czech Republic in Lower Austria. Furthermore it is eponymous for the local National Park 'Nationalpark Thayatal'. In the study area 14 dams are located in total, 13 along the Kaja River, and one along a tributary river. The study area influenced by dams amounts 1.615 ha. All dams are embankment dams whose cross-sections show hill-shaped forms. They are made of various compositions of soil, sand, clay, and rock. Four dams are currently active, ten are abandoned. The main objectives of this study are to identify if nonlinear/complex geomorphic system behavior occurs in this small and highly dam-affected watershed and to investigate geomorphic effects on fluvial systems due to dams. In order to find nonlinear/complex system behavior those sites are probed in which geomorphic effects due to dams are highly expected: reservoirs, channels, and floodplains. Sedimentary records, numerical modeling and mapping techniques will be used to reveal geomorphic changes and perturbations within the fluvial system. Spatial and temporal reconstructions and interpretation of geomorphic effects due to dams will be used to reconstruct system behavior. River bed surface mapping, observations of river engineering structures, and land use changes already reveal that geomorphic effects due to dams do exist within our study area. Sediment cores show that reservoir sediments of abandoned dams are preserved. These will be especially useful for further quantitative and qualitative investigations. First results of the study will be presented on European Geosciences Union General Assembly, 2010.

Pöppl, Ronald E.; Keiler, Margreth; Glade, Thomas

2010-05-01

148

Fluvial Channel Networks as Analogs for the Ridge-forming Unit, Sinus Meridiani, Mars  

NASA Astrophysics Data System (ADS)

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. Figure 1. Channel patterns in Saharan upland and lowland landscapes, compared to RFU ridge patterns. Left panel—southern Sudan uplands (ctr 11.1N 28.4E); center panel—part of a large fan, Muglad basin, immediately downstream of sediment-source upland shown in left panel (10.15N 28.6E); right panel—discontinuous inverted ridge patterns, Mars (ctr 2.1N 1.0W). Arrows show direction of regional stream flow (left, center panels) and regional slope in Mars study area (right panel). North to top.

Wilkinson, M. J.; Dubois, J. B.

2010-12-01

149

Estimating the fluvial sediment input to the coastal sediment budget: A case study of Ghana  

NASA Astrophysics Data System (ADS)

Knowledge of fluvial sediment supply to the coastal sediment budget is important for the assessment of the impacts on coastal stability. Such knowledge is valuable for designing coastal engineering schemes and the development of shoreline management planning policies. It also facilitates understanding of the connection between rivers in the hinterland and adjoining coastal systems. Ghana's coast has many fluvial sediment sources and this paper provides the first quantitative assessments of their contributions to the coastal sediment budget. The methods use largely existing data and attempt to cover all of Ghana's significant coastal rivers. Initially work was hindered by insufficient direct measured data. However, the problem was overcome by the application of a regression approach, which provides an estimated sediment yield for non-gauged rivers based on data from gauged rivers with similar characteristics. The regression approach was effective because a regional coherence in behaviour was determined between those rivers, where direct measured data were available. The results of the assessment revealed that Ghana's coast is dissected by many south-draining rivers, stream and lagoons. These rivers, streams and lagoons supply significant amounts of sediment to coastal lowlands and therefore contribute importantly to beaches. Anthropogenic impoundment of fluvial sediment, especially the Akosombo dam on the Volta River, has reduced the total fluvial sediment input to the coast from about 71 × 106 m3/a before 1964 (pre-Akosombo dam) to about 7 × 106 m3/a at present (post-Akosombo dam). This sharp reduction threatened the stability of the east coast and prompted an expensive ($83 million) defence scheme to be implemented to protect 8.4 km-long coastline at Keta. Sections of Ghana's coast are closely connected to the hinterland through the fluvial sediment input from local rivers. Therefore, development in the hinterland that alters the fluvial sediment input from those local rivers could have significant effects on the coast. There is the need, therefore, to ensure that catchment management plans and coastal management plans are integrated or interconnected.

Boateng, Isaac; Bray, Malcolm; Hooke, Janet

2012-02-01

150

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

Microsoft Academic Search

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.

D. R. Kerr; L. A. Jirik

1990-01-01

151

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

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Assets of members of the Agua Caliente Band of Mission Indians. 115.106 Section 115...INDIANS IIM Accounts § 115.106 Assets of members of the Agua Caliente Band of Mission Indians. (a) The...

2009-04-01

152

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

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Assets of members of the Agua Caliente Band of Mission Indians. 115.106 Section 115...INDIANS IIM Accounts § 115.106 Assets of members of the Agua Caliente Band of Mission Indians. (a) The...

2010-04-01

153

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

NASA Astrophysics Data System (ADS)

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.

Kraus, Mary J.; Middleton, Larry T.

1987-01-01

154

A spatially lumped model to investigate downstream sediment flux propagation within a fluvial catchment  

NASA Astrophysics Data System (ADS)

A spatially lumped process–response model, PaCMod, is presented, which calculates long time series (103–106 years) of fluvial water discharge and sediment load at the river catchment outlet, based on climatic data, drainage basin characteristics and user-defined parameters. Key aspects of the model are (i) the lumped approach, allowing for fast simulations and preserving the same resolution from palaeoclimatic conditions and geomorphological reconstructions; (ii) the parameterization of sediment routing and storage within the catchment. PaCMod was successfully tested on observed data from three present-day fluvial systems: the Meuse, the Waipaoa, and the Po Rivers. Moreover, the simulated sediment flux for the Meuse and for the Waipaoa Rivers in the late Quaternary is in agreement with published field and modelling work. PaCMod experiments show how the downstream propagation of the original climatic signal is hampered by sediment routing and storage within the catchment.

Forzoni, Andrea; de Jager, Gerben; Storms, Joep E. A.

2013-07-01

155

Applicazione dell'Indice di Funzionalità Fluviale (IFF) ad un fiume minore della pianura trevigiana: il Meolo  

Microsoft Academic Search

Riassunto Nel corso dell'anno 2003 la Provincia di Treviso in collaborazione con l'Università Ca' Foscari di Venezia ha svolto una campagna di applicazione dell'Indice di Funzionalità Fluviale (IFF) all'asta del Fiume Meolo. Obiettivo della ricerca è stato quello di ampliare le conoscenze relative al fiume attraverso una prima individuazione dei fattori che incidono maggiormente sulla funzionalità dell'ecosistema fluviale e l'identificazione

Ornella De Ros; Mara Zanette; Maurizio Siligardi; Pier Francesco Ghetti; Paolo Negri; Paola Camuccio

156

Fluvial sedimentology and architecture of the middle Frio Formation (Oligocene), Jim Wells, Klegerg, and Nueces Counties, south Texas  

Microsoft Academic Search

The middle Frio Formation of the northeastern Gueydan fluvial system comprises fluvial and overbank deposits averaging 2,000 to 3,000 ft in thickness. Discrete genetic intervals are defined from subsurface studies using four cores totaling 575 ft, high-resolution resistivity borehole images, and electrical logs. A genetic interval is composed of four facies: (1) Channel-fill facies (30-ft thick and 2,500-ft wide) includes

1991-01-01

157

Dissolved organic matter composition in a fragmented Mediterranean fluvial system under severe drought conditions  

Microsoft Academic Search

In Mediterranean regions, drought is one of the main factors shaping fluvial ecosystems. Droughts cause a shift from lotic\\u000a to lentic conditions, triggering a gradual fragmentation of the longitudinal hydrological continuum, and a severe alteration\\u000a of water chemical properties. However, within a biogeochemical perspective, little is known about how and to which extend\\u000a droughts modify the chemical properties of dissolved

Eusebi Vazquez; Stefano Amalfitano; Stefano Fazi; Andrea Butturini

2011-01-01

158

Movement Patterns of Japanese Fluvial Sculpin Cottus pollux in a Headwater Stream  

Microsoft Academic Search

Movements of the Japanese fluvial sculpin Cottus pollux were studied over a 2-year period using a mark-recapture technique in two reaches (100 and 300 m) of a small, temperate stream system, the Fujii River, Japan. Of 321 recaptures, 62 fish (19.3%) moved across at least one riffle (i.e., were “mobile”). Fish moved distances of up to 192 m (median =

Takaharu Natsumeda

2007-01-01

159

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

NASA Astrophysics Data System (ADS)

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.

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

2007-12-01

160

Fluvial sedimentology of an Upper Jurassic petrified forest assemblage, Shishu Formation, Junggar Basin, Xinjiang, China  

Microsoft Academic Search

McKnight, C. L.. Graham, S A.. Carroll. A. R.. Gan. Q., Dilcher, D. L, Min Zhao and Yun Hal Liang. 1990 Fluvial sedimeutology of au Upper JurassIC petflfied forest assemblage. Shishu Formation. Junggar Basm, Xinjiang, Chma. Palaeogeogr.. PalaeoclImatol. Palueoecol., 79' 1-9. A remarkable petflfied forest assemblage is preserved 10 the Upper Jurassic Shishu FonnatlOn of the northeastern Junggar basin. Xmjiang

Cleavy L. McKnight; S. A. Graham; A. R. Carrollb; Q GAN; D DILCHER; M ZHAO; Y HAILIANG

1990-01-01

161

Late Glacial fluvial response of the Niers-Rhine (western Germany) to climate and vegetation change  

NASA Astrophysics Data System (ADS)

The Niers valley was part of the Rhine system that came into existence during the maximum Saalian glaciation and was abandoned at the end of the Weichselian. The aim of the study was to explain the Late Pleniglacial and Late Glacial fluvial dynamics and to explore the external forcing factors: climate change, tectonics and sea level.The sedimentary units have been investigated by large-scale coring transects and detailed cross-sections over abandoned channels. The temporal fluvial development has been reconstructed by means of geomorphological relationships, pollen analysis and 14C dating.The Niers-Rhine experienced a channel pattern change from braided, via a transformational phase, to meandering in the early Late Glacial. This change in fluvial style is explained by climate amelioration at the Late Pleniglacial to Late Glacial transition (at ca. 12.5 k 14C yr BP) and climate-related hydrological, lithological and vegetation changes. A delayed fluvial response of ca. 400 14C yr (transitional phase) was established. The channel transformations are not related to tectonic effects and sea-level changes. Successive river systems have similar gradients of ca. 35-40 cm km-1.A meandering river system dominated the Allerød and Younger Dryas periods. The threshold towards braiding was not crossed during the Younger Dryas, but increased aeolian activity has been observed on the Younger Dryas point bars. The final abandonment of the Niers-Rhine was dated shortly after the Younger Dryas to Holocene transition.Traces of Laacher See pumice have been found in the Niers valley, indicating that the Niers-Rhine was still in use during the Younger Dryas. Copyright

Kasse, C.; Hoek, W. Z.; Bohncke, S. J. P.; Konert, M.; Weijers, J. W. H.; Cassee, M. L.; van der Zee, R. M.

2005-05-01

162

Subsystems, flowpaths, and the spatial variability of nitrogen in a fluvial ecosystem  

Microsoft Academic Search

Nutrient dynamics in rivers affect biogeochemical fluxes from land to oceans and the atmosphere. Fluvial ecosystems are thus\\u000a important environments for understanding spatial variability in nutrient concentrations. At the San Pedro River in semi-arid\\u000a Arizona, USA, we investigated how variability in dissolved inorganic nitrogen (DIN) was regulated by subsystem type and hydrological\\u000a flowpaths. The three subsystems we compared were the

David Bruce Lewis; Nancy B. Grimm; Tamara K. Harms; John D. Schade

2007-01-01

163

Grain size, geochemistry and organic pollutants in modern fluvial deposits in eastern Moravia (Czech Republic)  

Microsoft Academic Search

Modern fluvial deposits from both small and large rivers were studied at 14 monitoring sites over 2 years (4 successive sampling\\u000a seasons) in the area of eastern Moravia (Czech Republic). Grain size, geochemistry, content of persistent organic pollutants\\u000a (PAHs, PCBs, HCHs, DDTs, HCBs and PeCB) and TOC were examined with the aim to understand their mutual relations and seasonal\\u000a variations in

Slavomír Nehyba; K. Hilscherova ´; J. Jarkovský; L. Dušek; T. Kuchovský; J. Zeman; J. Klánová; I. Holoubek

2010-01-01

164

A stability diagram for fine-grained, cohesive fluvial-channel bifurcations  

Microsoft Academic Search

Although the evolution of fine-grained fluvial distributive networks depends upon the stability of channel bifurcations, neither the stability field nor the stabilizing processes of bifurcations are currently well-known. Here we define the theoretical stability field for fine-grained bifurcations using Delft3D, a morphodynamic numerical model, and test the model predictions using field data collected on eight natural bifurcations in the Mossy

D. A. Edmonds; R. L. Slingerland; J. L. Best; J. S. Bridge; D. Janesko; F. E. Klein; D. R. Parsons; N. D. Smith

2007-01-01

165

Extraction of fluvial networks from SPOT panchromatic data in a low relief, arid basin  

Microsoft Academic Search

Euclidean distance classification of SPOT panchromatic data was used to delineate ephemeral, fluvial networks on low-relief, alluvial fan surfaces in an arid basin in the southwestern United States. The SPOT classified channel network was registered to a Universal Transverse Mercator (UTM) projection and compared to areas of channelized flow and a Strahler-ordered channel network extracted from U.S. Geological Survey 7½ minute

THOMAS W. GARDNER; KATHRYN F. CONNORS; Haiyan Hu

1989-01-01

166

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

SciTech Connect

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.

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

1994-05-01

167

Fingerprinting the sources of fluvial sediment using fallout and in-situ radionuclides in forested watershed in Japan  

NASA Astrophysics Data System (ADS)

To study the fluvial sediment sources in forested watershed in Shikoku island, Japan, the concentration of Cs-137 and Pb-210ex, U and Th decay series radaionuclides were analyzed. The soil sampling was conducted in hillslopes in various locations such as landslide scar, surface erosion in unmanaged Hinoki (Chamaecyparis obtusa) plantation, and detailed sampling in the channel deposit was also conducted in several tributaries. The activities of Cs-137, Pb-210ex, Bi-214 and Tl-208 of soils and fluvial sediments were determined by gammaspectroscopy. We also analyzed landuse of the watershed and forest logging area and landslide area were measured by air photo interpretation. The study area is Shimanto river basin, located 700 km southwest of Tokyo. The 2270 km2 area watershed ranges in elevation from 0 m to 1485 m above sea level. Low concentration of Cs-137 and Pb-210ex in fine sediments and surface soil at landslide scar suggest that fluvial sediments are derived from surface soil of the landslide scars or from channel walls. The concentrations of Cs-137 and Pb-210ex of fluvial sediment are found to be decrease as the landslide area increases. The data of U and Th decay series radionuclides, Bi-214 and Tl-208, indicate that the sources of fluvial sediment are adjacent to the sampling sites. The results suggest that landslide scar and adjacent to the channel are dominant sources of fluvial sediment in this watershed.

Kato, H.; Onda, Y.; Hiramatsu, S.; Seki, R.

2003-12-01

168

The Holocene fluvial chronology of Spain: evidence from a newly compiled radiocarbon database  

NASA Astrophysics Data System (ADS)

A critical analysis of 74 radiocarbon dates, selected from a total of 102 published and unpublished dates from Holocene fluvial environments in Spain, has identified a number of periods of increased fluvial activity in Spain, namely: 11,170 10,230; 9630 8785; 7980 6860; 5800 4800; 3880 3085; 2895 1820; 1300 0 cal BP, the latter period reflecting sustained fluvial response to increased human impact. The radiocarbon samples were classified according to type of depositional environment: (a) alluvial overbank, (b) flood basin, (c) alluvial channel gravels, (d) fluvio-torrential deposits and (e) slackwater flood deposits (palaeofloods). Dates from slackwater flood deposits indicated at least five phases of increased frequency of large magnitude floods during the Holocene: 10,855 10,230; 9530 8780; 2880 2430; 975 790; and 520 265 cal yr BP. Flood basin type deposition occurred from 7980 to 4830 cal yr BP. The main clusters of dates from alluvial floodplain deposits occurred at 2750 2150 and 930 520 cal yr BP. The record is discussed in relation to other palaeoenvironmental archives including pollen records of Holocene vegetation change and palaeoclimatic proxies such as the North Atlantic drift ice record. Comparison with the latter indicates that major Holocene flooding coincided with cold climate phases during 9530 9280, 2880 2430 and 520 265 cal yr BP; a cooling phase at 10,855 10,230; and warming phases at 9030 8780 and 975 790 cal yr BP.

Thorndycraft, V. R.; Benito, G.

2006-02-01

169

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

170

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

NASA Astrophysics Data System (ADS)

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.

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

2008-09-01

171

Fractal topography and subsurface water flows from fluvial bedforms to the continental shield  

USGS Publications Warehouse

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.

Worman, A.; Packman, A. I.; Marklund, L.; Harvey, J. W.; Stone, S. H.

2007-01-01

172

Fluvial thermal erosion during the ice break-up of the Lena river (Siberia)  

NASA Astrophysics Data System (ADS)

The Lena River is one of the largest Arctic rivers; its periglacial environment implies an excessive fluvial regime and a spectacular flood occurring at the end of the winter. From the beginning of November to May, a continuous ice cover can be observed as thick as 2 m on the Lena River in Central Siberia. The break up starts around May 15 at the latitude of Yakutsk, corresponding to a flood wave coming from the South and to an increase of the water stream temperature up to 18°C. In spite of a relatively good understanding of the initial stage of the breakup period of these periglacial rivers [Beltaos and Burrell, 2002; Shen, 2003; Billfalk, 1982], only a few studies report on the role of mechanical and thermal erosion during the breakup Observations and measurements of erosion of the island heads during the first days of the ice breakup were made during breakup periods over a 4-year period (2008-2011). Here, we reassess the efficiency of the fluvial thermal erosion using both high resolution records from field measurements and modeling. We analyze the impact of the breakup on the erosional process on the head of several fluvial islands. Only a few days are enough to produce erosion rate as high as 30 m. The protective effect of the ice cover at the very beginning of the break up has been studied in more detailed during 3 field trips. These values are relatively high but are in good agreement with our modeling.

Costard, F.; Gautier, E.; Fedorov, A.; Konstantinov, P.; Dupeyrat, L.

2012-04-01

173

Mount Kenya volcanic activity and the Late Cenozoic landscape reorganisation in the upper Tana fluvial system  

NASA Astrophysics Data System (ADS)

Volcanic-fluvial landscape interaction of the late Cenozoic Mt Kenya region in the upper Tana catchment has been reconstructed. The oldest newly dated phonolite flow is 5.78 Ma (40Ar/39Ar), placing the initiation of Mt Kenya volcanic activity within the Late Miocene, much earlier than reported before, 3-3.5 Ma (K/Ar). The main body of the stratovolcano was already in existence around 4.22-5.27 Ma (40Ar/39Ar) supplying lahars to its lower footslopes. The final recorded volcanic main vent phase in the study area produced multiple phonolitic flows and lahars around 2.8 Ma (40Ar/39Ar). There is evidence of at least two major Pliocene drainage blocking events between 3.89 and 2.81 Ma (40Ar/39Ar) causing lava dammed lakes in which volcanic tuff deposits accumulated. Around this time the river Tana did not incise much and shaped an extensive fluvial plain, whose remnants can now be found around 1150 m altitude. This fluvial plain has been incising during the last 2.8 Ma, whereby the incision rate changed in time due to changing uplift rate and volcanic events. A flood basalt eruption covering 1150 km2, estimated to be 5 km3, on the south flank of Mt Kenya of the Thiba basalts at 0.80 Ma (40Ar/39Ar) plugged the Upper Tana basin and caused significant drainage reorganisation. The Tana was diverted southwards abandoning its former valley. The terrace record in the Tana valley downstream the Thiba basalts appears to register this event as a post 0.8 Ma accelerated incision. Current Thiba valley morphology is relatively young and appears to register uplift controlled terraces with interbedded lahars for the last 300 ka only, indicating a delayed fluvial response of approximately 0.5 Ma. The landscape reconstruction demonstrates that the Tana was well able to compensate for many volcanic events such as lahars and lava flows. Only the build-up of a stratovolcano body and a large flood basalt caused prolonged impact on fluvial landscape development.

Veldkamp, A.; Schoorl, J. M.; Wijbrans, J. R.; Claessens, L.

2012-04-01

174

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

NASA Astrophysics Data System (ADS)

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.

Fielding, C. R.

2010-12-01

175

Fluvial Interpretation of Ridged Units, Northern Sinus Meridiani/Southwest Arabia Terra, Mars  

NASA Astrophysics Data System (ADS)

THEMIS, MOC, and HiRISE imagery shows features at various scales that suggest fluvial emplacement of the ridge-forming rock units exposed in northern Sinus Meridiani and southwestern Arabia Terra. The study area -- 10 N to 2 S latitude and 10 W to 8 E longitude -- spans the interface from the southern highlands to the northern plains. Numerous, linear ridges of varying width, orientation and sinuosity (mainly lower sinuosity) are suggestive of fluvial channels. Sets of features can be interpreted as braided channel reaches. Cross-cutting relationships, a common feature of channels on terrestrial fluvial plains, are ubiquitous. Many sinuous features appear as twinned parallel lines, suggesting preferential cementing of coarser channel-bank sediments. A few examples exist of features that can be interpreted as scroll bars and channel augmentation in locally narrow reaches. Layering and internal discontinuities of the Meridiani rocks are consistent with a fluvial interpretation. The regional setting of study-area units accords closely with many terrestrial basins which are occupied by fluvially emplaced sediment bodies known as megafans. Contiguous megafan surfaces (characterized by numerous channel traces, of varied orientation) cover large areas -- 1.25 million sq. km. in S. America -- with radii of hundreds of km. Megafans characteristically lie at the foot of a backing highland, from which rivers supply sediment. The ridged units on Mars lie at the foot of the southern highlands from which numerous river valleys have drained towards Meridiani Planum/southwest Arabia Terra. Further, the present regional slope is apparently away from the highlands, with downslope dimensions of hundreds of km. The low slopes of the northern Meridiani units mirror the typically low regional slopes of terrestrial megafans. Low slopes are conducive to the development of water bodies, which are numerous on some terrestrial megafans. The lacustrine model for the formation of the hematite-bearing unit is thus consistent with a megafan analog. Eroded desert landscapes on Earth show chemically cemented paleo-channels as inverted topography. Paleo- megafans in terrestrial deserts, displaying inverted topography, are the closest morphologic analogs to the ridges of northern Meridiani/southwest Arabia Terra. Further studies -- including quantitative comparisons of ridge characteristics and spectroscopic investigation of cementing minerals -- are underway to determine the origin of these widespread martian units.

Wilkinson, J.; Allen, C. C.; Oehler, D. Z.

2007-12-01

176

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

NASA Astrophysics Data System (ADS)

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.

Howard, Alan D.

2007-11-01

177

Environmental magnetic record of the fluvial sediments from the Tianzhu borehole in Beijing for the last 800 ka  

NASA Astrophysics Data System (ADS)

A high-resolution environmental magnetic investigation has been carried out on a 186.3-m-thick sequence of fluvial sediments from the Tianzhu borehole in the Beijing Plain. Magnetic stratigraphic analysis revealed that the sediment sequence spans the last 800 ka without significant hiatuses. Comparison of the magnetic susceptibility (k) with pollen records suggests that the magnetic susceptibility serves as a good proxy for climate changes. The high k values of the sediments reflect warm climate conditions, and the low k values match cold periods. Magnetic susceptibility records correlate well with the ODP 677 oxygen isotope proxy, with high/low k values corresponding to the interglacial/glacial stages, implying a climate alternation of glacial-interglacial cycles in the Beijing Plain. The lithologic analysis of the Tianzhu borehole cores suggests that climate change was the primary factor in controlling the fluvial sedimentary cycles in the studied area. A fluvial sedimentary model in which precipitation affected the fluvial sediment by controlling the discharge and transport capacity of rivers in different stages may be applied to our research. The rock magnetic records of the Tianzhu fluvial sequence display two extreme events at 750-720 ka and 270-250 ka, respectively, which are regarded as a two-period cycle of aridification and cooling in the Asian interior. The extreme event at 750-720 ka likely resulted from the fast uplift of the Himalayan-Tibetan Plateau and the expansion of Arctic ice-sheet.

Shi, L.; Yang, Z.; Zheng, L.; Jia, S.; Tong, Y.; Zhang, S.; Xu, D.; Guo, G.

2010-08-01

178

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

SciTech Connect

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.

Jaworowski, C. (Univ. of Wyoming, Laramie, WY (United States). Dept. of Geology)

1993-04-01

179

Fluvial particle characterization using artificial neural network and spectral image processing  

NASA Astrophysics Data System (ADS)

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 ?m 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.

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

2008-03-01

180

Defining Spatial Gradients in Fluvial Erosion Across the Eastern Himalayan Syntaxis  

NASA Astrophysics Data System (ADS)

The Eastern Himalayan Syntaxis is a region with high relief, the most powerful river in the Himalaya (Finlayson et al., 2002) and exceptionally rapid exhumation over the last 3 million years (Burg et al.,1997). Due to the spatial coincidence of the 5000 m deep Tsang-Po River gorge and the young, rapidly exhumed Namche Barwa metamorphic massif within the Eastern Himalayan Syntaxis, it has been suggested that river erosion is localizing crustal advection in the region (Zeitler et al., 2001). To help define the surface boundary conditions that would enable development of such a self-organized balance between erosion and rock uplift, we calculate an index of fluvial erosion rate for major rivers (Parlung, Jiong and Tsang-Po) in the Eastern Himalayan Syntaxis. We compute the annual mean unit stream power drawing on high resolution data from a number of sources. We use elevation profiles derived from DMA DTED 90 m and ASTER 30 m digital elevation models to generate river slope measurements. We use maps of river width generated from Landsat TM scenes to define continuous river width changes. Apart from being essential for stream power calculations, these data also highlight the importance of river width as a first-order control on a river's ability to erode bedrock. Finally, we use TRMM satellite rainfall measurements verified with Chinese Hydrological Bureau statistics (Anders et al., this meeting) to define spatial variation in river discharge. The stream power calculations predict a heterogeneous pattern of erosion along major river channels which is consistent both with the pattern of rock uplift implied by the geologic structure of the region and with exhumation patterns revealed by thermochronologic work, suggesting a topographic steady-state condition. To evaluate this prediction and clarify the relationship of unit stream power to fluvial incision rate and landscape lowering rate, we are measuring in-situ cosmogenic 10Be from fluvially polished bedrock surfaces and in sediments from small, non-glaciated catchments along the Parlung River.

Finnegan, N. J.; Anders, A. M.; Hallet, B.; Montgomery, D. R.; Stone, J. O.

2002-12-01

181

Late Quaternary changes in flow-regime on the Gwydir distributive fluvial system, southeastern Australia  

NASA Astrophysics Data System (ADS)

Ages for large palaeochannels of the Gwydir distributive fluvial system (DFS) in northern New South Wales, Australia have been determined using single grain optically stimulated luminescence. Two palaeochannel systems have been found to dominate; the here named Coocalla (43-34 ka) and Kamilaroi (19-16 ka) which have inferred palaeodischarges 25-100 times the bankfull discharges of nearby channels of the contemporary Gwydir system, which appears to have been established during the Mid-Holocene. This scale differential is very much larger than that reported for other catchments in southeastern Australia, and reflects both a decline in catchment runoff through the Last Glacial cycle and the adoption of a distributary pattern sometime after 16 ka. Actual decline in catchment runoff, determined by comparing estimated palaeodischarge with contemporary flows upstream of the DFS where flow is confined to a single channel, indicate contemporary discharge to be 0.1 times and 0.25 times that of the Coocalla and Kamilaroi, respectively.The chronology presented here shows periods of increased discharge in the Gwydir to be more or less coincident with those observed elsewhere in the Murray Darling Basin. Although no evidence of a 'Gum Creek' fluvial phase (from 35 to 25 ka) was found, the Coocalla and Kamilaroi palaeochannel systems broadly conform in age to 'Kerarbury' and 'Yanco' fluvial phases on the Murrumbidgee and Murray systems. This synchronicity with more southern catchments supports the hypothesis that La Nina - like conditions were semi-permanent for much of the Last Glacial cycle with moisture derived largely from the western Pacific Ocean.

Pietsch, Timothy J.; Nanson, Gerald C.; Olley, Jon M.

2013-06-01

182

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

NASA Astrophysics Data System (ADS)

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 (?c, 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 × 107?c3.188. 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.

Wilson, Andrew; Lavé, Jérôme

2013-03-01

183

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

NASA Astrophysics Data System (ADS)

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%.

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

2010-12-01

184

Fluvial response to rapid episodic erosion by earthquake and typhoons, Tachia River, central Taiwan  

NASA Astrophysics Data System (ADS)

Analysis of typhoon- and earthquake-triggered landsliding and fluvial response in the Tachia River, central Taiwan, documents highly episodic sediment supply over decade to century timescales. Landslide data from the Chi-Chi earthquake (1999) and subsequent typhoons (2001, 2004, and 2005) quantify the sediment supply from these events. Fluvial response was investigated by decadal-scale and century-scale longitudinal river profile data spanning 1904 to 2008 and by sediment delivery recorded in suspended sediment load and reservoir sedimentation data. Our results show that the different time periods of satellite images and aerial photographs used in previous studies make it difficult to unambiguously identify the causes of landslides previously attributed by some studies to the effects of the Chi-Chi earthquake rather than subsequent high intensity precipitation. In response to significant variability in sediment delivery from hillslopes, century-scale profile variation data indicate substantial bed surface elevation change of 2.6 ± 6.7 m, and decade-scale bed surface elevation change of 1.1 ± 3.3 m. Since 1993, the downstream reaches incised in response to bedload sediment trapping by reservoirs while headwater reaches aggraded in response to increased sediment delivery from uplands. A tremendous increase in reservoir sedimentation after 2000 likely reflects the effects of the highest decade-average daily rainfall since 1900. Suspended sediment load data indicate a post Chi-Chi earthquake increase in sediment concentration in low-flow events but do not exhibit the clear influence on sediment yields at higher flows as (e.g., typhoons) reported by others for fluvial response in the epicentral region.

Huang, Michelle Y.-F.; Montgomery, David R.

2012-11-01

185

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

NASA Astrophysics Data System (ADS)

South America delivers more freshwater runoff to the ocean per km2 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.

Harden, Carol P.

2006-09-01

186

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

SciTech Connect

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.

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

1988-02-01

187

Fluvial response to horizontal shortening and glaciations: A study in the Southern Alps of New Zealand  

NASA Astrophysics Data System (ADS)

It has been postulated that a steady state between erosional and tectonic processes may develop in continental collision. However, it is not clear whether steady state conditions can be reached for all components of the landscape. Here we show, using landscape evolution models and field evidence, that a true geomorphic steady state may never be reached in the Southern Alps of New Zealand. The strong asymmetries in tectonic uplift and tectonic advection and the onset of glaciations constantly interact to prevent the landscape from reaching a topographic steady state. Evidence suggests that the first-order geomorphology on the western side of the Southern Alps is controlled by orographic precipitation combined with extreme rates of tectonic uplift, whereas the development of deep glacial valleys on the eastern side is initiated by differential uplift along large faults. We also develop a first-order equation, governing the dynamics of the Main Divide, to show that both tectonic advection and fluvial erosion efficiency control the position and the height of the main drainage divide. Using a two-dimensional landscape evolution model, we demonstrate that the transition from glacial to fluvial conditions at the end of the last glaciation led to substantial modifications of the landscape: While the main trunk channels get slowly uplifted, ridges are leveled down, causing the relief to decrease. Hillslopes appear to be affected by fluvial processes which seem to be driven by incision of river tributaries. This reduction of relief will probably never reach a steady state since warmer interglacial periods are substantially shorter than glacial periods.

Herman, Frédéric; Braun, Jean

2006-02-01

188

Geological Relationships Between Hydrated Minerals And Fluvial Landforms In Tyrrhena Terra, Mars.  

NASA Astrophysics Data System (ADS)

The phyllosian period of Mars displays rocks that are altered at different levels, containing phyllosilicates of various nature, revealing that liquid water played a strong role in their formation. However, debates currently exist to know if this alteration was conduced at the surface due to a different climate, or in the subsurface from hydrothermal circulation. Here, we display results in the Tyrrhena Terra region, which is of interest to address this issue. Indeed, Tyrrhena Terra is located in cratered Noachian highlands in the southern hemisphere, south of Isidia Planitia and north of Hellas basin. This region displays highland terrains partially dissected by fluvial valleys and several intercrater plains. Phyllosilicates are identified by the combination of 1.9 and 2.3 micron features in the OMEGA imaging spectrometer data. They are frequently located on craters ejecta and pieces of outcrops close to the highlands. Olivine and pyroxenes are also identified, and are associated mainly to the intercrater plains when present together. We focus our interest on regions where a single 1.9 micron signature is observed (with small 2.3 micron features observed locally), and where pyroxene is found in the same area. This detection suggests a partial alteration or a spatial mixing with unaltered material as highlighted by the presence of pyroxene signatures at the same location. The geologic study of these areas of interest shows that these hydrous minerals are located at the foothills of highlands, especially in locations where valley networks end in plains. This leads to the conclusion that these hydrous minerals are observed in alluvial plains collecting material from the highlands. This example shows that external cycles of running water are involved in alteration minerals deposition. We currently study these regions in details to know if the alteration was a result of this process during sedimentation (alteration coeval to fluvial activity), or if the alteration occurred earlier in the crust with later erosion and transport into the alluvial plains (without relation with fluvial episodes).

Bouley, S.; Loizeau, D.; Mangold, N.; Poulet, F.; Ansan, V.; Le Mouelic, S.; Bibring, J.; Langevin, Y.

2008-12-01

189

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

NASA Astrophysics Data System (ADS)

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.

Irwin, R. P.

2011-12-01

190

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

USGS Publications Warehouse

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

Colman, S. M.

1983-01-01

191

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

NASA Astrophysics Data System (ADS)

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

Braun, J.

2012-04-01

192

Geomorphological facies reconstruction of Late Quaternary alluvia by the application of fluvial architecture concepts  

NASA Astrophysics Data System (ADS)

This paper investigates the methodical implications, the benefits, and the constraints of applying the fluvial architecture concept to Late Quaternary shallow-subsurface alluvial deposits. The focus is upon a typical small- to mesoscale valley floor of the temperate zone. The studied reach is part of the river Wetter catchment (517 km2) in central Germany. A large number of studies on Late Quaternary terrestrial paleoenvironmental change of the temperate zone refer to such small- to mesoscale catchments, which are mostly occupied by mixed- to suspended-load rivers. As in many cases mostly coring-based evidence is available, the observation and measurement is limited to lithology and lithofacies boundaries; facies geometry must be inferred. Moreover, in those environments differences in lithofacies are obscured by a significantly reduced range of grain size distributions. An example of an ancient channel belt of Late Glacial to Holocene age serves to delineate the methodical practice and utility of the fluvial architecture approach. Field evidence is obtained from detailed cross-sectional surveys and comprises descriptions of lithofacies, structural, pedogenetical, biotic features, Munsell color, and total organic carbon magnetic volume susceptibility. Cross-sectional lithofacies information is represented by spatially attributed, scaled borehole logs. The example also accentuates the need for applying additional stratigraphical methods such as physical age determination, macrofossil analysis, and tephrological stratigraphy. These methods form the basis to discern stacked channel facies and derive a diachrony of channel forms. Thus, the adapted architecture approach provides a significant surplus of information on channel dimensions, ages, and channel floodplain interconnectedness. Distinct fluvial landforms such as channels, levees, abandoned channels, swamps, and floodplain flats can be highlighted. A number of methodical constraints are discussed in detail, e.g., the sharpness of channel element geometry and the underlying ordering of bounding surfaces. Moreover, it is shown that the analytical process resembles an iterative looping process that is led by deduction. Many geomorphologists and multi-disciplinary floodplain researchers collect sedimentary data but still neglect utilizing the potential of architectural analysis. The study makes clear that sedimentological approaches used in 'big river' floodplains also apply to small valleys; in fact, the procedures for facies reconstruction need to be adjusted to each individual case study. Alluvial architecture analysis provides the tools to reveal interconnectedness (or disconnectedness) of channel, near-channel, and overbank fluvial landforms, which is essential for a geomorphological understanding of floodplain evolution.

Houben, Peter

2007-04-01

193

Some observations on Titan's fluvial networks and channel/valley delineation using Cassini radar imagery  

NASA Astrophysics Data System (ADS)

Data from the Cassini-Huygens mission have revealed fluvial networks on Titan’s surface. Past research found that fluvial sediment transport and erosion processes at the grain scale on Titan would be comparable to similar processes on Earth [1,2]. On this basis, we assume that basin-scale fluvial processes would also be similar to terrestrial processes and that analytical approaches derived for Earth would give meaningful results for Titan. An algorithm had been developed from terrestrial data to classify fluvial networks (e.g., as dendritic, rectangular, parallel, etc.) [3]. This algorithm was simplified and has been applied to classify networks in Cassini Titan Radar Mapper synthetic aperture radar (SAR) images of Titan [4,5]. It was also uncertain how much the direction of radar illumination impacted the interpretation of features visible in the imagery; overlapping radar swaths can provide useful information about that effect. We delineated channel/valley features on several radar swaths based on the distinguishability, morphology, and illumination [3]. In recently released data, at least 2 networks containing a minimum of 7 visible links or 3 junction angles were found in swaths T41 and T44, and were analyzed using the simplified algorithm [3]. T41 overlapped with T43, and T44 overlapped with T13, allowing comparison of network delineations and analysis of the effect of illumination angle on network classification. Channel delineation in overlap areas was compared, and differences were noted. The largest differences were attributed to human delineation error, poor effective resolution, or the directions of radar illumination (Figure 1). However, they did not affect the network classification; in both T13 and T44, the networks were classified as rectangular, which is commonly caused by subsurface tectonic activity. In contrast, the networks in T41 were classified as parallel, indicating variation in the controlling factors, such as steeper terrain or less tectonic influence. References: [1] Burr, D.M. et al (2006) Icarus, 181, 235-242. [2] Collins, G.C. Geophys. Res. Lett., 32 (22).[3] Ichoku, I. & Chorowicz, J. (1994) Water Resources Research, 30, 161-174. [4] Jacobsen, R.E. et al (2008) AGU abstract#P21A-1315 [5] Burr, D.M. et al (sub. 2009) Geophys. Res. Lett. Figure 1: Channel feature visible in T13 (left) was not readily apparent in T44 (right) due to the direction of radar illumination (see arrows).

Viola, D.; Burr, D. M.; Phillips, C. B.

2009-12-01

194

Experimental insights on the effects of varying discharge on fluvial landscape evolution  

NASA Astrophysics Data System (ADS)

River floods are known to have large impacts on fluvial morphology as the capacity to carry water and rework sediment during these events is large. However, recent experimental findings are conflicting: some suggest that varying discharge contributes to a more single-thread pattern whereas others suggest that discharge variations cause multiple threads to be active, and yet others show no significant effect on the morphology. Our objective is to study the effect of varying discharge on experimental river patterns with otherwise similar conditions, and to quantitatively compare the resulting morphology and deposits. Our experiments were conducted in a flume of 10x6 meter, which was split up into two separate fluvial plains (each 10x3 m). Fluvial landscape evolution was recorded by high-resolution line-laser scanning and digital Single Lens Reflex (SLR) camera used for channel-floodplain segmentation and particle size estimation. The bed sediment consisted of a poorly sorted sediment mixture ranging from fine sand to fine gravel. First, a braided and meandering river pattern evolved for identical and constant boundary conditions, except that slightly cohesive silt-sized silica flour was added to the feed sediment of the meandering channel. A second set of experiments had an identical cycled discharge regime with a long-duration low flow and a short-duration high flow.The varying discharge largely affected the fluvial landscape by biasing the morphology towards the high flow conditions. This was reflected by an increase of the bar wave length with nearly a factor 2. Also, the depth of maximum erosion increased, which affects the preservation potential. The meandering and braided patterns responded differently to the floods. The noncohesive sediment combination with varying discharge results in a higher degree of braiding when compared to constant discharge. This was observed as a higher number of re-activating channels during high flow. In contrast, the silica flour acted as floodplain builder, which was more efficiently distributed during floods. As a result, the system with slightly cohesive sediment remained mostly confined to one migrating meandering channel that developed scroll bars, channel fills, splays and levees. We conclude that the response to varying discharge depends on the availability and cohesion of fine floodplain-forming sediment in combination with the potential of high flows to re-activate residual channels.

van de Lageweg, W. I.; van Dijk, W. M.; Kleinhans, M. G.

2012-04-01

195

Experimental insights on the effects of varying discharge on fluvial landscape evolution  

NASA Astrophysics Data System (ADS)

River floods are known to have large impacts on fluvial morphology as the capacity to carry water and rework sediment during these events is large. However, recent experimental findings are conflicting: some suggest that varying discharge contributes to a more single-thread pattern whereas others suggest that discharge variations cause multiple threads to be active, and yet others show no significant effect on the morphology. Our objective is to study the effect of varying discharge on experimental river patterns with otherwise similar conditions, and to quantitatively compare the resulting morphology and deposits. Our experiments were conducted in a flume of 10x6 meter, which was split up into two separate fluvial plains (each 10x3 m). Fluvial landscape evolution was recorded by high-resolution line-laser scanning and digital Single Lens Reflex (SLR) camera used for channel-floodplain segmentation and particle size estimation. The bed sediment consisted of a poorly sorted sediment mixture ranging from fine sand to fine gravel. First, a braided and meandering river pattern evolved for identical and constant boundary conditions, except that slightly cohesive silt-sized silica flour was added to the feed sediment of the meandering channel. A second set of experiments had an identical cycled discharge regime with a long-duration low flow and a short-duration high flow.The varying discharge largely affected the fluvial landscape by biasing the morphology towards the high flow conditions. This was reflected by an increase of the bar wave length with nearly a factor 2. Also, the depth of maximum erosion increased, which affects the preservation potential. The meandering and braided patterns responded differently to the floods. The noncohesive sediment combination with varying discharge results in a higher degree of braiding when compared to constant discharge. This was observed as a higher number of re-activating channels during high flow. In contrast, the silica flour acted as floodplain builder, which was more efficiently distributed during floods. As a result, the system with slightly cohesive sediment remained mostly confined to one migrating meandering channel that developed scroll bars, channel fills, splays and levees. We conclude that the response to varying discharge depends on the availability and cohesion of fine floodplain-forming sediment in combination with the potential of high flows to re-activate residual channels.

van de Lageweg, W. I.; Van Dijk, W. M.; Kleinhans, M. G.

2011-12-01

196

Impact of the global warming on the fluvial thermal erosion over the Lena River in Central Siberia  

NASA Astrophysics Data System (ADS)

The hydrology of the Lena and its tributaries is characterized by an extremely episodic flow regime. Here we report recent climatic change in Central Siberia, and its impact on the fluvial thermal erosion. We point out three major changes since the 1980s: a marked reduction of the river ice thickness in winter, a pronounced increase of the water stream temperature in spring and a slight increase of the discharge during the break up (May-June). A GIS analysis based on aerial pictures and satellite images highlights the impact of the water warming on the frozen banks. The vegetated islands appear to be very sensitive to the water temperature increase, showing an acceleration of their head retreat (+21-29%). This suggests that recent global warming directly affects the fluvial dynamics and the erosional process of one of the largest arctic fluvial system.

Costard, F.; Gautier, E.; Brunstein, D.; Hammadi, J.; Fedorov, A.; Yang, D.; Dupeyrat, L.

2007-07-01

197

Fluvial armor  

Microsoft Academic Search

Mobile armor layers which form during bed load transport of non-uniform sediments are shown to be closely related to the static armor layers that form by selective erosion as a result of the action of clear water flows. Two previously published numerical models of the transport of non-uniform sediments are used as a basis for the discussion. Each model is

G. Parker; A. J. Sutherland

1990-01-01

198

Single-grain cosmogenic 21Ne concentrations in fluvial sediments reveal spatially variable erosion rates  

NASA Astrophysics Data System (ADS)

We evaluated the hypothesis that the spatial variation in erosionin a catchment is reflected in the distribution of the cosmogenicnuclide concentrations in sediments leaving the catchment. Usingpublished data and four new 10Be measurements in fluvial sedimentcollected from the outlets of small river catchments, we constrainedthe spatial variability of erosion rates in the Gaub River catchmentin Namibia. We combined these catchment-averaged erosion rates,and the mean slope values with which they are associated, ina digital elevation model (DEM)-based analysis to predictdistributions of cosmogenic 21Ne concentrations in the sedimentleaving the Gaub catchment. We compared these synthetic distributionswith the distribution of concentrations of cosmogenic 21Ne (21NeC)in 32 quartz fluvial pebbles (16-21 mm) collected fromthe catchment outlet. The 21NeC concentrations span nearly twoorders of magnitude (2.6-160 x 106 atoms/g) and are highlyskewed toward low values. The DEM-based analysis confirms thisskew—the measured 21NeC distribution plots within theenvelope of distributions predicted for the catchment. Thismatch between measured and synthetic 21Ne distributions impliesthat the measured distribution is a signature of the spatialvariation in erosion rates.

Codilean, Alexandru T.; Bishop, Paul; Stuart, Finlay M.; Hoey, Trevor B.; Fabel, Derek; Freeman, Stewart P. H. T.

2008-02-01

199

Tidal sedimentation from a fluvial to estuarine transition, Douglas Group, Missourian -- Virgilian, Kansas  

SciTech Connect

The Tonganoxie Sandstone Member of the Stranger Formation (Douglas Group, Upper Pennsylvanian, Kansas) was deposited in a funnel-shaped, northeast-southwest-trending paleovalley that was incised during the uppermost Missourian sealevel lowstand and backfilled during the subsequent transgression. Quarry exposures of the Tonganoxie near Ottawa, Kansas, include [approximately] 5 m of sheetlike, vertically accreted siltstones and sandy siltstones, bounded above and below by thin coals with upright plant fossils and paleosols. Strata range from submillimeter-thick, normally graded rhythmites to graded bedsets up to 12.5 cm thick with a vertical sedimentary structure sequence (VSS) consisting of the following intervals: (A) a basal massive to normally graded interval; (B) a parallel-laminated interval; (C) a ripple-cross-laminated interval; and (D) an interval of draped lamination. The Tonganoxie succession has many similarities to fluvial overbank/floodplain deposits: sheetlike geometry, upright plant fossils, lack of bioturbation and body fossils, dominance of silt, and a punctuated style of rapid sedimentation from suspension-laden waning currents. Analysis of stratum-thickness variations through the succession suggests that tides significantly influenced sediment deposition. A fluvial-to-estuarine transitional depositional setting is interpreted for the Tonganoxie by analogy with modern depositional settings that show similar physical and biogenic sedimentary structures, vertical sequences of sedimentary structures, and aggradation rates.

Lanier, W.P. (Emporia State Univ., Emporia, KS (United States). Dept. of Earth Sciences); Feldman, H.R. (Univ. of Kansas, Lawrence, KS (United States). Kansas Geological Survey); Archer, A.W. (Kansas State Univ., Manhattan, KS (United States). Dept. of Geology)

1993-09-01

200

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

SciTech Connect

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.

Wilson, K.M. (Bryn Mawr College, PA (United States)); Dodson, P. (Univ. of Pennsylvania, Philadelphia (United States)); Fiorillo, A.R. (Carnegie Museum, Pittsburgh, PA (United States))

1991-03-01

201

Evaluation of Ground-Based LiDAR for use in Fluvial Geomorphology and River Restoration  

NASA Astrophysics Data System (ADS)

Ground-based LiDAR (Light Detection And Ranging) techniques have been used for a variety of engineering and geomorphic applications, but as yet have not been evaluated for use in fluvial geomorphology or river restoration. For this pilot project, we evaluated the usefulness of ground-based LiDAR for a variety of projects in fluvial geomorphology and river restoration throughout the United States, including surveys of incised streams, bank erosion, levees, as-built maps of restoration sites, under-canopy vegetation, gully incision rates, fen encroachment by upland trees, and riparian vegetation growth rates. We developed new approaches for surveying using ground-based LiDAR that are efficient at covering ground in streams and would be useful for other geomorphic applications. We found that ground-based LiDAR has great potential in many areas of ecology and geomorphology that have not yet been fully explored. As with other types of LiDAR, development of more-advanced filtering and visualization techniques will greatly enhance the usefulness of final LiDAR products.

Storesund, R.; Minear, J.

2006-12-01

202

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

PubMed

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

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

1997-11-01

203

Lakota Formation, southern Black Hills, South Dakota: an Early Cretaceous evolving fluvial system  

SciTech Connect

The fluvial, Early Cretaceous Lakota Formation consists of four spatially and temporally distinct sandstone units in the southern Black Hills and southeastern Powder River basin. Three of these units crop out in proximity to an area of uranium roll-front development (Edgemont mining district) where approximately 2300 wells were drilled and logged. Comparison of the resistivity logs of several of these wells with continuous cores of the Lakota Formation confirms their lithologic sensitivity. These logs (utilized to assist in subsurface facies interpretations where cores were not available), cores, and outcrops are the basis for the following facies interpretations. The discharge, sediment load, and resulting sinuosity of this fluvial system varied substantially throughout the time of Lakota deposition. The oldest unit consists of tabular deposits with complex internal architecture comprised of cross-cutting lateral accretion deposits. Upward-fining grain size, upward-decreasing scale of sedimentary structures, and the angular relationship between lateral accretion surfaces and overlying crevasse-splay deposits support this conclusion. The intermediate unit of ephemeral stream sediments is characterized by abundant pebble- and cobble-strewn erosional surfaces with up to 1.5 m relief, very poor clast sorting, and trough and planar cross-bedding with concave-upward foresets. The youngest unit has a predominance of tabular cross-bedding with back flow climbing ripples and low dispersion of paleocurrent directions, suggesting a relatively straight, bed-load-type channel dominated by trains of sand waves.

Dahlstrom D.J.; Fox, J.E.

1986-08-01

204

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

205

Reconstruction of the diagenesis of the fluvial-lacustrinedeltaic sandstones and its influence on the reservoir quality evolution  

Microsoft Academic Search

The reservoir quality of Jurassic and Triassic fluvial and lacustrine-deltaic sandstones of the Yanchang Oil Field in the\\u000a Ordos Basin is strongly influenced by the burial history and facies-related diagenetic events. The fluvial sandstones have\\u000a a higher average porosity (14.8%) and a higher permeability (12.7 × 10?3 ?m2) than those of the deltaic sandstones (9.8% and 5.8 ×10?3) ?m2, respectively).

Jinglan Luo; S. Morad; Xiaoli Zhang; Shike Yan; Fuli Wu; Yuhong Li; Junmin Xue

2002-01-01

206

Sand composition in an Iberian passive-margin fluvial course: the Tajo River  

NASA Astrophysics Data System (ADS)

The Tajo River, the 10th largest river in Europe, drains part of the western passive margin of Europe that includes multiple tectonic elements of the Iberian plate. Modern fluvial sand composition in the Tajo River drainage basin reflects the nature of the source region, which lies in the central part of the Iberian Peninsula. Four fluvial petrographic provinces (A, B, C and D) can be established in the Tajo drainage basin, corresponding well with the four principal structural units drained: (1) the Iberian Range; (2) the Hesperian massif; (3) The Tertiary Tajo basin; and (4) the Neogene Santarem Lisboa basin. Province A corresponds to the Tajo River head and is characterized by quartzolithic sedimenticlastic sands (Qm67F4Lt29 and Rs79Rg3Rm18). These sands have been derived from diverse Mesozoic siliciclastics and carbonates of the Iberian Range. Province B appears in the upper reaches of the Tajo River course and is quartzofeldspathic (Qm57F34Lt9) with diverse rock fragments (Rs34Rg23Rm43). Sources are Hercynian granitoids and metasediments and Neogene clastics and minor carbonates of the Tertiary Tajo basin. Province C extends along the middle course of the Tajo River with quartzofeldspathic metamorphiclastic sand modes (Qm60F33Lt7; Rs4Rg21Rm75). The sources are metamorphic rocks intruded by plutonites of the Hesperian Massif. Province D is quartzofeldspathic (Qm55F39Lt6) with a dominance of phaneritic rock fragments (Rs5Rg33Rm62) and corresponds to the lower reaches of the Tajo River, where siliciclastic deposits of the Neogene Santarem Lisboa basin are the main sources. Sands plot on provenance-discrimination diagram (QmFLt) within the recycled-orogen field (Tajo River head) and continental-block fields (upper, middle and lower course). In addition, we have proven the usefulness of the RsRgRm diagram to discriminate the defined fluvial provinces, originating from heterogeneous parent-rock textures and mineralogy. Climate does not exert any strong influence on the petrogenesis of the Tajo River drainage basin sand, and erosion in the source areas may be described in terms of weathering-limited denudation regime. By contrast, mixing with tributary supplies is the main process that modifies composition in the Tajo River sand. The establishment of fluvial provinces related to the main bedrock structural units reflects the great relevance of tributaries from each province in the generation of the Tajo River sand and the low significance of inherited sandy load from previous provinces. The abundance of granitoid rock fragments (RsRgRm%Rg) in fluvial sand of both tributaries and main channel of the Tajo River drainage basin faithfully represents the relative abundance of granodiorite+monzogranite bedrock exposure in each subbasin. Metasedimentary and metamorphic bedrock outcrop area is overrepresented by metamorphic rock fragments (RsRgRm%Rm) in both sand from tributaries and from the Tajo main trunk river. This is manifested by differences of 18 23% between means of metasedimentary outcrop area and the RsRgRm%Rm mean in the sand from Provinces B and C+D, respectively. Sedimentary (mainly carbonate) outcrop area is underrepresented or not represented by sedimentary rock fragments (RsRgRm%Rs) in sand of the Tajo River. This underrepresentation causes a difference between means of sedimentary outcrop area and the RsRgRm%Rs mean of 21%, 17.1% and 10.7% in sands from Province A, B and C+D, respectively. This fact confirms the rapid loss of these grains during transport because of their labile nature.

Le Pera, Emilia; Arribas, José

2004-10-01

207

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

NASA Astrophysics Data System (ADS)

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.

Church, M.

2004-12-01

208

Reach-Scale Influence of Riparian Vegetation on Fluvial Erosion (Invited)  

NASA Astrophysics Data System (ADS)

A strong link exists between riparian vegetation and stream channel morphology. With increased emphasis on water quality and aquatic habitat in headwater streams, a complete understanding of the role of riparian vegetation on channel form is important for effective stream management and restoration. Streambank fluvial erosion plays a key role in channel migration; streambank undercutting leads to slope instability, mass wasting, and bank retreat. By influencing the local microclimate, streambank hydrology and soil strength, and reach-scale hydraulics, riparian vegetation exerts considerable influence on the processes involved in channel form. The susceptibility of streambank soils to fluvial entrainment depends not only on the soil type, but also on soil moisture, bulk density, and the soil stress history due to wet/dry and freeze/thaw cycling. Riparian vegetation exerts significant influence on all of these factors through precipitation interception, increased infiltration and evapotranspiration, and altered exposure to day time solar heating and night time cooling. The timing and magnitude of these influences depends on the vegetation form, root distribution, and temporal growth patterns. Riparian vegetation also increases the physical resistance of streambank soils to hydraulic shear stress through root reinforcement; the roots of herbaceous plants are typically very fine and are located primarily within the top 30 cm of the soil. In comparison, woody plants have a more uniform root distribution over the upper 1 m of the streambank, providing root reinforcement with greater depth. The presence of above-ground vegetation on streambanks increases hydraulic resistance and alters both flow and turbulence patterns in the channel. Dense riparian vegetation creates a zone of uniform velocity adjacent to the streambank, with an additional boundary layer and area of increased turbulence at the interface between the vegetation and the main channel. At high flows, flexible herbaceous vegetation folds and reduces shear stress near the boundary. In contrast, rigid woody vegetation increases shear stress near the streambank, particularly at the streambank toe. This area is susceptible to fluvial erosion and the presence of dense, semi-rigid vegetation may encourage the formation of a wider channel with a vertical streambank. Through these multiple complex interactions, riparian vegetation exerts significant control on headwater stream form. Increased understanding of the interactions between stream channel morphology and riparian vegetation is needed to guide stream management and restoration decision-making.

Wynn, T.; Hopkinson, L. C.

2009-12-01

209

Fluvial response to the Paleocene-Eocene Thermal Maximum in northwest Wyoming and western Colorado, USA  

NASA Astrophysics Data System (ADS)

The Willwood and Wasatch formations of northwest Wyoming and western Colorado record alluvial deposition within the intermontane Bighorn and Piceance Creek basins, respectively. Both display substantial shifts in the character of fluvial sand-bodies coincident with an abrupt negative carbon isotope excursion linked to the Paleocene Eocene Thermal Maximum (PETM) climate change event at ~55 Ma. In the northern Bighorn Basin, an anomalously thick and laterally persistent multi-story fluvial sand-body crops out within the main body of the PETM isotopic excursion. The internal architecture and lithofacies within the sand-body are similar to pre- and post-PETM sand-bodies, and mean paleo-flow depths do not appear to change substantially. The most significant change is the increase in vertical and lateral amalgamation within the PETM sand-body. Long-term basin sedimentation rates are constant spanning the event implying a transient increase in channel mobility via avulsion and meandering processes during the PETM, which preferentially evacuated fine-grained overbank material out of the basin to the north. Similarly, fluvial sand-bodies are more laterally and vertically amalgamated during the PETM in the Piceance Creek Basin. Yet here the sand-bodies are a recurrent phenomenon throughout the PETM, persist after the PETM, and show dramatic internal architectural changes. Flow depths increase by ~50% and are twice as variable during the PETM, lithofacies are dominated by upper flow regime structures, and crevasse splay deposits are ubiquitous in the associated floodplain strata. In both basins enhanced channel mobility was likely facilitated by a combination of vegetation overturn and alteration of precipitation patterns. Sediment stored higher in the catchment and on related hill-slopes was released, choked basin river systems, instigated greater in-channel deposition, and caused more rapid avulsions. Introduction of coarser sediment loads and vegetation change would have weakened bank strengths allowing more rapid meandering by river systems. However, the differential response in the two basins suggests that vegetation overturn played a greater role in the Bighorn Basin as channel size, discharge, and flow conditions did not substantially change whereas increases in the seasonality of precipitation likely played a more dominant role in the Piceance Creek Basin where discharge and flow conditions were greatly altered during the event.

Foreman, B. Z.; Heller, P.; Clementz, M. T.

2011-12-01

210

Fluvial stratigraphy and palaeoenvironments of River Han: Preliminary results from Hanam, Korea  

NASA Astrophysics Data System (ADS)

Valley floor sediments from the Pungsan land development area of Hanam, east of Seoul, provide evidence for Pleistocene and Holocene floodplain conditions of lower Han River. Two terrace surfaces are present in studied area. The upper terrace (30m above current channel bed) has been regarded as remnant of dissected pediment. However, it should be mentioned that severely weathered fluvial sediment particles were found from the top of the hill. So, theses features could be originated from fluvial action rather than other processes. The lower terrace, alluvial deposits, has been thought to be formed during the Pleistocene. Using 125 boring core samples, fluvial stratigraphy of the area is reconstructed and a 3 dimensional map is presented. In situ weathered basal surface found from 0-10m from current mean sea level (Stage 1). This weathered layer could be bedrock surface rather than weathered surface when it formed in the time of lower sea level. About 10m thick gravel with sand matrix layer covers the bedrock surface (Stage2). This layer interpreted as channel bed sediment. The thickness of this gravel dominant layer increases northward (towards current river channel). Transition from stage 1 to stage 2 could be related with sea level rising. Up to 5m thick sand layer overlays the gravel layer (Stage 3). The change from the gravel layer to sand layer is abrupt rather than gradual. This change could happen with channel shifting northward. The colour of the sand deposits is dark brown to brown when it overlays thick gravel layer (up to 10m), but greenish grey to grey when it covers weathered bedrock surface or thin (up to 2m) gravel deposits. Upper most part of deposits consists with clay and silt (up to 7m in thickness). Peat layers imbedded in this layer with various thickness. Physical characteristics of greenish grey silt and clay deposits similar with marine sediments found from the coast of Yellow sea. It is too early to say the origin of these deposits but further chemical and biological analysis will provide better information on the origin. The age of each layer will be measured with proper measurement methods, including 14C and OSL. Results from pollen and diatom analysis also will be performed to reconstruct the climate of past and changes.

Kim, J.; Yang, D.; Rhee, S.

2005-12-01

211

Paleoclimate cycles and tectonic controls on fluvial, lacustrine, and eolian strata in upper Triassic Chinle Formation, San Juan basin  

Microsoft Academic Search

Sedimentologic study of the Upper Triassic Chinle Formation in the San Juan basin (SJB) indicates that Late Triassic paleoclimate and tectonic movements influenced the distribution of continental lithofacies. The Shinarump, Monitor Butte, and Petrified Forest Members in the lower part of the Chinle consist of complexly interfingered fluvial, floodplain, marsh, and lacustrine rocks; the Owl Rock and Rock Point Members

Russell F. Dubiel

1989-01-01

212

Clay mineral, geochemical and Sr-Nd isotopic fingerprinting of sediments in the Murray-Darling fluvial system, southeast Australia  

Microsoft Academic Search

Clay minerals, trace elements and isotopic signatures ( 87 Sr\\/ 86 Sr; 143 Nd\\/ 144 Nd) were investigated to fingerprint fine-grained sediments (52mm) from the major tributaries of the Murray-Darling fluvial system. Mineralogical, chemical and isotopic signatures in the river clays are clearly inherited from the assemblage of source rocks and soils in the upper catchments of each river. As

F. X. Gingele; P. de Deckker

2005-01-01

213

Changes in Fluvial Deposition Associated with the Paleocene-Eocene Thermal Maximum (PETM) in the Bighorn Basin, WY (Invited)  

Microsoft Academic Search

The Paleocene-Eocene Thermal Maximum (PETM) was an ~200 ky period of rapid global warming at the onset of the Eocene. Excellent exposures of the PETM interval in the southeastern Bighorn Basin, WY provide an opportunity to examine the impact of this event on the architecture of fluvial strata, particularly floodplain deposits. In the study area, the PETM interval overlies the

M. J. Kraus; F. A. McInerney; S. Newbury; S. Wing; A. A. Baczynski

2010-01-01

214

Knickpoint initiation and distribution within fluvial networks: 236 waterfalls in the Waipaoa River, North Island, New Zealand  

Microsoft Academic Search

If knickpoints transmit signals of base level fall in river networks, then improvements in our understanding of their retreat rate and basin wide distribution helps constrain the transient response following perturbation. Many studies of knickpoint retreat focus on the response of trunk streams to base level fall. Here we examine the response of an entire fluvial network, as recorded by

Benjamin T. Crosby; Kelin X. Whipple

2006-01-01

215

Late Pleistocene–early Holocene paraglacial and fluvial sediment history in the Turbio valley, semiarid Chilean Andes  

Microsoft Academic Search

The transitional character of climatic conditions confers great relevance to paleoclimate studies in the semiarid region where glacial and Holocene geomorphologic records are scarce. Here we present the paraglacial and fluvial evolution of the Turbio valley (30°S) using both field observations and 14C AMS chronology. Two key sites at the uppermost Turbio valley show glacial margins which likely formed during

Rodrigo Riquelme; Constanza Rojas; Germán Aguilar; Pablo Flores

2011-01-01

216

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

NASA Astrophysics Data System (ADS)

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.

Bertrand, F.; Papanicolaou, T.

2009-12-01

217

Palynology of the Bryn Mawr Formation (Miocene): insights on the age and genesis of middle atlantic margin fluvial deposits  

Microsoft Academic Search

The ages of fluvial deposits at the head of Chesapeake Bay, thought to be the updip, chronostratigraphic equivalents of a well-dated late Oligocene to Quaternary marine sequence in the Salisbury Embayment, are poorly known. We present data regarding a new occurrence of a palynoflora recovered from the Bryn Mawr Formation in Cecil County, Maryland. The floral assemblage for the Bryn

F. J. Pazzaglia; R. A. J. Robinson; A. Traverse

1997-01-01

218

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

USGS Publications Warehouse

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.

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

2002-01-01

219

Inverted fluvial features in the Aeolis\\/Zephyria Plana region, Mars: Formation mechanism and initial paleodischarge estimates  

Microsoft Academic Search

A subset of the sinuous ridges (SRs) in the Aeolis\\/Zephyria Plana (AZP) region of Mars has been previously hypothesized to be inverted fluvial features, although the precise induration and erosion mechanisms were not specified. Morphological observations and thermal inertia data presented here support this hypothesis. A variety of mechanisms can cause inversion, and identification of the specific events that lead

Devon M. Burr; Rebecca M. E. Williams; Kimberly D. Wendell; Matthew Chojnacki; Joshua P. Emery

2010-01-01

220

Fluvial geomorphology and hydrology in the dispersal and fate of pyrite mud particles released by the Aznalcóllar mine tailings spill  

Microsoft Academic Search

The Agrio-Guadiamar River reach affected by the Aznalcóllar mine tailings spill can be divided into three main sectors taking account of geomorphic characteristics and human-induced changes. Along the first 15 km, the valley presents the characteristics of a middle fluvial reach of moderate sinuosity and gradient; the floodplain declines gently towards the main channel and is built up mainly by

Francesc Gallart; Gerardo Benito; Juan Pedro Mart??n-Vide; Alfonso Benito; Josep Maria Prió; David Regüés

1999-01-01

221

Holocene fluvial geochronologies, global databases and hydrological proxies: rethinking people-river interactions and rapid climate change impacts (Invited)  

Microsoft Academic Search

The assumption of the constancy of climate over time periods of around a century, which was the basis of much engineering and hydrological forward planning until recently, is now widely felt to be unsatisfactory. This re-evaluation has been prompted by a number of important empirical, interdisciplinary and technological advances in fluvial science research over the last decade that is increasingly

M. G. Macklin

2009-01-01

222

The relation of Holocene fluvial terraces to changes in climate and sediment supply, South Fork Payette River, Idaho  

Microsoft Academic Search

Well-preserved Holocene terraces along the South Fork Payette River in central Idaho provide a record of fluvial system behavior in a steep mountain watershed characterized by weathered and erodible Idaho Batholith granitic rocks. Terrace deposit ages were provided by 14C dating of charcoal fragments and optically stimulated luminescence (OSL) dating of sandy sediments. Along with pairing of many terrace tread

Jennifer L. Pierce; Grant A. Meyer; Tammy Rittenour

2011-01-01

223

Sedimentation in a discharge dominated fluvial-lacustrine system: the Neogene Productive Series of the South Caspian Basin, Azerbaijan  

Microsoft Academic Search

The largely lower Pliocene Productive Series and its regional equivalents contain the major hydrocarbon reservoirs of the South Caspian Basin. Examination of outcrops in the Apsheron region, Azerbaijan, has resulted in re-interpretation of the depositional environments of the Productive Series. The lower part of the Productive Series consists of sandstones and mudstones interpreted as channelised and sheetflood fluvial deposits, intercalated

D. J Hinds; E Aliyeva; M. B Allen; C. E Davies; S. B Kroonenberg; M. D Simmons; S. J Vincent

2004-01-01

224

The effect of salt crust on the thermal conductivity of one sample of fluvial particulate materials under Martian atmospheric pressures  

Microsoft Academic Search

A line-heat source apparatus was used to measure thermal conductivities of a lightly cemented fluvial sediment (salinity = 1.1 g · kg?1), and the same sample with the cement bonds almost completely disrupted, under low pressure, carbon dioxide atmospheres. The thermal conductivities of the cemented sample were approximately 3× higher, over the range of atmospheric pressures tested, than the thermal

Marsha A. Presley; Robert A. Craddock; Natalya Zolotova

2009-01-01

225

Fluvial\\/lacustrine diagenesis: Significance for hydrocarbon production and entrapment in the carboniferous Albert Fm, Moncton basin, NB  

Microsoft Academic Search

The Carboniferous Horton Group Albert Formation sediments include lacustrine source-rock oil shales and fluvial porous reservoir sandstones. The petrography, stable isotopes, fluid inclusions, cathodoluminescence and mirror\\/trace element chemistry of these sandstones are used to establish the diagenetic history and controlling factors. Early diagenetic calcite, quartz and albite cements with minor chlorite and kaolinite are variably present and related to depositional

J. P. A. Noble; A. H. Chowdhury; H. Yu

1996-01-01

226

Regional distribution of wave- and fluvial-dominated deltaic deposits of Olmos formation (upper Cretaceous) in Maverick basin, southwest Texas  

Microsoft Academic Search

Regional subsurface analysis in southwest Texas indicates that the Olmos Formation (Gulfian) was deposited by a complex of wave- and fluvial-dominated delta systems in two depocenters. Sediment influx was from the north and northwest. Five deltaic submits, A through E, were deposited in the western depocenter. Three other deltaic wedges (F, G, H) formed the second depocenter farther east in

W. Ambrose; N. Tyler

1984-01-01

227

Sedimentology of the fluvial and fluvio-marine facies of the Bahariya Formation (Early Cenomanian), Bahariya Oasis, Western Desert, Egypt  

Microsoft Academic Search

The Lower Cenomanian Bahariya Formation in the Bahariya Oasis, Western Desert, Egypt, was deposited under two coeval environmental conditions. A fully fluvial system occurs in the southern portion of the Bahariya Oasis, including depositional products of meandering and braided streams, and a coeval fluvio-marine setting is dominant to the north. These deposits are organized into four unconformity-bounded depositional sequences, whose

M. A. Khalifa; O. Catuneanu

2008-01-01

228

Taenidium and Associated Ichnofossils in Fluvial Deposits, Cretaceous Tuscaloosa Formation, Eastern Alabama, Southeastern U.S.A  

Microsoft Academic Search

Exposures of the Tuscaloosa Formation in eastern Alabama (U.S.A.) provided an opportunity to examine ichnofossils and ichnofabrics within Cretaceous fluvial facies. Floodplain mudstones are completely bioturbated and dominated by backfilled burrows most allied with Taenidium serpentinum. These burrows likely reflect the work of insects or oligochaetes that occupied soft, moist proximal floodplain substrates. Although the affinities and ethology of the

Charles E. Savrda; Jonathan W. Collier; Robert A. Drake; Robert L. Graves; Anthony G. Hall; Anne I. Nelson; James C. Slone; Daphne D. Williams; H. Alexander Wood

2000-01-01

229

Impact of the global warming on the fluvial thermal erosion over the Lena River in Central Siberia  

Microsoft Academic Search

The hydrology of the Lena and its tributaries is characterized by an extremely episodic flow regime. Here we report recent climatic change in Central Siberia, and its impact on the fluvial thermal erosion. We point out three major changes since the 1980s: a marked reduction of the river ice thickness in winter, a pronounced increase of the water stream temperature

F. Costard; E. Gautier; D. Brunstein; J. Hammadi; A. Fedorov; D. Yang; L. Dupeyrat

2007-01-01

230

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

SciTech Connect

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.

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

231

Use of sediment-trace element geochemical models for the identification of local fluvial baseline concentrations  

USGS Publications Warehouse

Studies have demonstrated the utility of fluvial bed sediment chemical data in assesing local water-quality conditions. However, establishing local background trace element levels can be difficult. Reference to published average concentrations or the use of dated cores are often of little use in small areas of diverse local petrology, geology, land use, or hydrology. An alternative approach entails the construction of a series of sediment-trace element predictive models based on data from environmentally diverse but unaffected areas. Predicted values could provide a measure of local background concentrations and comparison with actual measured concentrations could identify elevated trace elements and affected sites. Such a model set was developed from surface bed sediments collected nationwide in the United States. Tests of the models in a small Louisiana basin indicated that they could be used to establish local trace element background levels, but required recalibration to account for local geochemical conditions outside the range of samples used to generate the nationwide models.

Horowitz, A. J.; Elrick, K. A.; Demas, C. R.; Demcheck, D. K.

1991-01-01

232

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

NASA Astrophysics Data System (ADS)

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 monograph Stream 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.

Schultz, Colin

2012-04-01

233

Insight on watershed development along the actively uplifting Mount Lebanon range (Lebanon) from marine and fluvial terraces  

NASA Astrophysics Data System (ADS)

Active uplift in the Mt. Lebanon range results from regional transpression along a ~200-km-long restraining bend within the Dead Sea fault system. Thus, the resultant landscape is characterized by the combined influences of tectonic, eustatic, and climatic controls. Marine terraces in northern Mt. Lebanon range provide significant constraints on regional uplift and, consequently, base level control on watershed development. Detailed geologic mapping reveals at least six coastal terrace levels between the cities of Tripoli and Batroun in northern Lebanon, ranging in elevation from 5 m to 113 m above sea level. The marine terraces are primarily abrasional platforms with little to no sediment cover. However, at certain locations, the terraces comprise of a thick (up to 20 m towards the coast) sedimentary cover that are the result of episodic periods of cut and fill into older Pliocene deposits. The majority of these sediments are well-rounded, cobble-size clasts of limestone cemented by a calcite matrix with occasional clasts of basalt and marine fossils. Travertine formations, fossil remnants, and limestone clasts are available to constrain ages on terrace formations and, in turn, coastal uplift rates. Correlation of terrace heights with Pleistocene sea level variations suggests an average, regional uplift rate of 0.3 m/ka. Fluvial terraces in the northern Mt. Lebanon allow reconstruction of longitudinal profiles that grade into base levels represented by the corresponding marine terraces. Hence, this correlation constrains the ages of fluvial terraces and consequently permits estimates of fluvial erosion. Temporal variations in fluvial transport capacity are suggested by episodic aggradation of massive boulder-size clasts of basalt and dolomite that originate over 20 km upstream. Furthermore, knickpoints in the present-day drainage also appear to correlate with the former base levels. Hence, the retreat of these knickpoints permits assessing the lag time in the response of the fluvial system to base level changes.

Lepley, S.; Gomez, F.; Nader, F.

2005-12-01

234

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

SciTech Connect

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.

Lewis, Claudia J [Los Alamos National Laboratory; Mcdonald, Eric [NON LANL; Sancho, Carlos [NON LANL; Pena, Jose- Luis [NON LANL

2008-01-01

235

Fluvial systems response to rift margin tectonics: Makhtesh Ramon area, southern Israel  

NASA Astrophysics Data System (ADS)

The geomorphic evolution of Makhtesh Ramon, a feather-shaped erosional valley, and the Nahal Neqarot drainage system to the south occurred largely in response to tectonic activity along the Dead Sea Rift and its western shoulder. Remnants of Miocene clastic sediments (Hazeva Formation) deposited on an erosional peneplain that formed over this area during the Oligocene epoch provide a datum plane for reconstructing subsequent fluvial evolution. These clastic remnants are presently located on the shoulders of Makhtesh Ramon at various elevations. The peneplain truncating the Makhtesh Ramon block has been tilted 0.7% northeastward since the Pliocene epoch (post-Hazeva Formation), whereas that of the Neqarot syncline, south of the Ramon, has been tilted 1.2%. The elliptical exposure of friable Lower Cretaceous sandstone, exposed in the core of the truncated Ramon structure, governed the development of a new ENE directed (riftward) drainage system through capture of streams that previously drained toward the Mediterranean Sea to the northwest. Incised fluvial gaps in the southern rim of Makhtesh Ramon and alluvial fan relicts within Makhtesh Ramon attest to original drainage into the Makhtesh from the south. Remnants of the Plio-Pleistocene Arava Conglomerate on the eastern end of the Neqarot syncline contain clasts from rocks exposed within Makhtesh Ramon, also indicating that streams flowed into the Makhtesh from the southern Neqarot block through the western gaps, then turning eastward and exiting the Makhtesh via the next (Sha'ar-Ramon) gap to the east. Further down-faulting of the Neqarot block during Mid-Late Pleistocene time led to westward retreat of the Neqarot valley and capture of the last stream flowing northward into the Ramon, leaving the modern Makhtesh Ramon isolated from the southern drainage system.

Ben-David, Ram; Eyal, Yehuda; Zilberman, Ezra; Bowman, Dan

2002-06-01

236

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

NASA Astrophysics Data System (ADS)

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.

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

2005-12-01

237

Quantifying fluvial gravel surface and sub-surface topography using photogrammetry  

NASA Astrophysics Data System (ADS)

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.

Pattison, Ian; Chandler, Jim; Rice, Stephen

2013-04-01

238

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

USGS Publications Warehouse

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.

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

2007-01-01

239

Fluvial response to Holocene volcanic damming and breaching in the Gediz and Geren rivers, western Turkey  

NASA Astrophysics Data System (ADS)

This study discusses the complex late Holocene evolution of the Gediz River north of Kula, western Turkey, when a basaltic lava flow dammed and filled this river valley. Age control was obtained using established and novel feldspar luminescence techniques on fluvial sands below and on top of the flow. This dating constrained the age of the lava flow to 3.0–2.6 ka. Two damming locations caused by the lava flow have been investigated. The upstream dam caused lake formation and siltation of the upstream Gediz. The downstream dam blocked both the Gediz and a tributary river, the Geren. The associated lake was not silted up because the upstream dam already trapped all the Gediz sediments. Backfillings of the downstream lake are found 1.5 km upstream into the Geren valley. The downstream dam breached first, after which the upstream dam breached creating an outburst flood that imbricated boulders of 10 m3 size and created an epigenetic gorge. The Gediz has lowered its floodplain level at least 15 m since the time of damming, triggering landslides, some of which are active until present. The lower reach of the Geren has experienced fast base level lowering and changed regime from meandering to a straight channel. Complex response to base level change is still ongoing in the Geren and Gediz catchments. These findings are summarized in a diagram conceptualizing lava damming and breaching events. This study demonstrates that one lava flow filling a valley floor can block a river at several locations, leading to different but interrelated fluvial responses of the same river system to the same lava flow.

van Gorp, W.; Veldkamp, A.; Temme, A. J. A. M.; Maddy, D.; Demir, T.; van der Schriek, T.; Reimann, T.; Wallinga, J.; Wijbrans, J.; Schoorl, J. M.

2013-11-01

240

Destruction of a fluvial reservoir by hydrothermal activity (Cameros Basin, Spain)  

NASA Astrophysics Data System (ADS)

This study provides an example of a high-quality fluvial hydrocarbon reservoir that was completely destroyed by hydrothermal processes. The reservoir unit was deposited in the Cameros Basin, located in the NW sector of the Iberian Chain (Spain). The basin was filled with clastic fluvial deposits (sandstones and conglomerates) between Late Berriasian and Early Aptian times. Provenance of sands was mainly from coarse crystalline rocks. A humid tropical climate produced intense weathering of K-feldspar during transport from source to basin. Thus, a mineralogically mature rigid framework with high porosity existed at the time of deposition, which would have constituted a high-quality hydrocarbon reservoir. At present however, the porosity of the reservoir is negligible. Porosity was reduced by a sequence of diagenetic processes: (1) mechanical compaction (i.e. crushing of metamorphic lithic grains) and chemical compaction, (2) kaolinite and siderite cementation, and (3) early quartz cementation. Hydrocarbon emplacement probably occurred between phases (2) and (3). A low-grade metamorphic (hydrothermal) event, reaching greenschist facies, took place during the Late Cenomanian. It dramatically reduced the remaining porosity of the reservoir and destroyed the hydrocarbon charge. Hydrothermal processes which affected the sandstones include (1) re-compaction; (2) late quartz cementation and silicification of remaining feldspars; (3) carbonate cementation; (4) chloritization of feldspars, metamorphic lithic fragments and intrabasinal argillaceous grains; and (5) growth of pyrite and chloritoid crystals on argillaceous material of intrabasinal, extrabasinal or even diagenetic origin. Hydrocarbons that migrated to the margins of the basin escaped these hydrothermal modifications and were preserved. The results of this study may be used to predict the diagenetic and hydrothermal evolution of other potential reservoirs in similar tectonic settings.

Ochoa, M.; Arribas, J.; Mas, R.; Goldstein, R. H.

2007-11-01

241

EVALUACIÓN DE LOS MODELOS NUMÉRICOS DE FLUJO DE AGUA EN EL SUELO HYDRUS-2D Y SIMDAS EN RIEGO LOCALIZADO  

Microsoft Academic Search

RESUMEN. En un sistema de riego localizado resulta muy importante conocer la distribución de agua en el suelo para evitar pérdidas por percolación y conseguir un nivel de producción óptimo. Para ello, en la fase inicial de diseño agronómico deben realizarse pruebas de campo previas, consistentes en aplicar un volumen de agua acorde a las necesidades del cultivo con un

G. Arbat; J. Puig; F. Ramírez de Cartagena

2003-01-01

242

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)

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.

Pelletier, Jon D.; DeLong, Stephen B.; Cline, Michael L.; Harrington, Charles D.; Keating, Gordon N.

2008-02-01

243

Geomorphic response to agricultural land use in small fluvial systems - The role of landscape connectivity  

NASA Astrophysics Data System (ADS)

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.

Poeppl, R.; Keiler, M.; Glade, T.; Engage-Geomorphological Systems; Risk Research

2010-12-01

244

External controls on formation and preservation of fluvial terrace staircases in the Southern Pyrenees foreland  

NASA Astrophysics Data System (ADS)

The fluvial network of the Southern Pyrenees is an example of transverse drainage systems in young (alpine) mountain belts and it features well preserved fluvial terrace records. Some of the major Southern Pyrenees tributaries, like the Cinca and the Gallego, have been studied previously and have some age controls on their fluvial terrace levels. We extend these records to the largest drainage system of the Southern Pyrenees, the Segre river system, presenting new GIS and field data, as well as exposure ages obtained from in situ produced 10Be cosmogenic nuclides. The terrace staircase of the Segre River is built up by cut and fill type terraces, ranging from 112 to 3 meter above the present-day riverbed. Gravel deposits have commonly thicknesses of 2 to 7 meter over bedrock. Locally they have extensive thicknesses of up to 20 meter and show evidence for the impact of ongoing tectonics (i.e. gypsum doming, tectonic basin) featuring faults and folds as primary features. The terrace record can be subdivided into four groups of terraces that are separated by large incisive steps of about 20 meter: I) old extensive single terrace surfaces (TQ1, ~112m), II) terraces of limited extent preserved as remnant hills (TQ2, ~80m), III) two extensive terrace levels (TQ3 and TQ4, 60-45m), and IV) a well-preserved and extensive lower terrace complex (TQ5-TQ7, 30-3m). The staircase morphology (extent and elevations) of the Segre River shows analogies with other streams of the Southern Pyrenees indicating regional scale causes for the formation of terraces. The terraces TQ1, TQ2,TQ3 and TQ4 have been sampled for in situ produced 10Be cosmogenic nuclides. Our results show preliminary minimum ages of Middle to Late Pleistocene terrace abandonment: TQ1: 274 ka (MIS 9a), TQ2: 135 ka (MIS 5e), TQ3: 106 ka (MIS 5c), and TQ4: 65 ka (MIS 3), and erosion rates of 0.3 cm/ka (TQ1, TQ4), 0.45 cm/ka (TQ3), and 0.73 cm/ka for TQ2. The obtained ages indicate a causal relationship between terrace abandonment (incision) and interglacial periods, and point to a terrace formation (aggradation) related to glacial periods in the Pyrenean headwaters. Sedimentological outcrop observations corroborate a cold-climate based genesis of the terraces and present numerous braided channels, ice rafted boulders and frozen sand clasts. Morphologically, the extensive terraces surfaces point to a more than 4km wide presumably braided river system during formation of TQ1 and TQ2. The longitudinal terraces correlation reveals a downstream diverging trend along the lower reaches (foreland stretch) which is most likely base-level controlled. We link the divergence of the Segre terraces to the downcutting history of the Catalan Coastal Range that borders the Ebro foreland basin to the Mediterranean Sea. The stepped morphology with several topographic levels at the breach record the downcutting history of the Catalan Coastal Range. Our longitudinal Segre terrace profiles point to a base-level of about 200m a.s.l. at the begin of terrace formation at the Segre and indicate gradual incision since at least the Middle Pleistocene. We argue, that the Catalan Coastal Range functioned as a local base-level upstream the sea outlet presumably until the Late Pleistocene. Hence, the preservation of terrace staircases at the Southern Central Pyrenees does not require tectonic uplift (although it can not be excluded) and can be explained by base-level mechanisms, while the terrace formation is climate triggered and the result of glacial-interglacial-cycles in the Pyrenees.

Stange, K. M.; van Balen, R. T.; Carcaillet, J.

2012-04-01

245

OSL dating of fluvial terraces for incision rate estimation and indication of neotectonic activity in Pamir  

NASA Astrophysics Data System (ADS)

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.

Fuchs, M. C.; Gloaguen, R.; Krbetschek, M.; Szulc, A.

2012-04-01

246

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

NASA Astrophysics Data System (ADS)

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.

Puttock, A. K.; Dungait, J.; Bol, R.; MacLeod, C. J.; Brazier, R.

2011-12-01

247

Evidences of Paleoearthquakes in Palaeolithic settlements within fluvial sequences of the Tagus Basin (Madrid, Central Spain).  

NASA Astrophysics Data System (ADS)

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.

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

248

Martian Fluvial Landforms: A THEMIS Perspective After One Year At Mars  

NASA Astrophysics Data System (ADS)

THEMIS (Thermal Emission Imaging System) began mapping operations on February 19, 2002 and is providing both visible and infra-red imaging observations of the martian surface at two scales (18 m/p and 100 m/p respectively). IR observations are being conducted during both day and night. IR imagery records temperature variations, which are primarily due to differences in abundances of rocks, indurated materials, sand, and dust on the surface. THEMIS has imaged all of the major outflow channels and valley networks. The source regions for the outflow channels contain large blocks of collapsed chaotic terrain with very coarse (rocky) slopes and talus aprons while the tops of these blocks appear smooth and mantled with finer grained materials (dust) or alternatively the tops of these blocks may be capped by a different material (relatively finer grained than the lower coarser talus producing material). This suggests that the blocks are made of strongly consolidated material capable of eroding into rocky debris. Layering along with cliff and ledge forming members as well as spur and gully morphology is also seen on the chaotic blocks and suggests materials of varying lithologic strengths. THEMIS IR data also indicates that the streamlined islands are composed of pre-existing laterally extensive, layered, weakly consolidated rock. This observation is based upon the fact that the islands do not exhibit coarse talus aprons unlike the chaotic terrain blocks mentioned above. The streamlined islands appear to be primarily erosional landforms and not depositional. No major depositional bedforms (boulder bars, mega ripples, boulder tails) are seen. This observation (lack of depositional bedforms) may be suggesting information on the consolidation and size of sediment transported by the outflow channels. We propose that the overall sediment transported by the floods was derived from layered weakly consolidated materials that break down into relatively fine-grained material that gets washed through the fluvial system. Sediment will flow over longer distances and have lower settling velocities due to the lower acceleration of gravity on Mars. These factors contribute to allowing the sediment to be deposited over very extensive areas and not in discrete sediment packages (bars and fans). It should also be mentioned that MOC imagery does not reveal any depositional bedforms. These observations and interpretations help explain the lack of major depositional bedforms similar to those associated with catastrophic floods on Earth (Channeled Scabland and Iceland). Clearly, coarse material is seen at the Pathfinder site but the large size material (30 cm and up) was transported only short distances 10’s of km (eroded from Twin Peaks and other knobby outliers and craters). Additionally, younger post diluvial nearby impact craters have also supplied ejecta material to the Pathfinder site. THEMIS imagery has also discovered and mapped two major flows. One is found near the mouth of the northern branch of Kasei Valles. It shows up well in both day and night IR imagery. Ma’adim Vallis has a flow that can be traced over 150 km from its mouth into the floor of Gusev crater. We suggest that these features are hyperconcentrated flows and not lava flows based on their morphology, geologic setting, and lack of nearby volcanic sources. Valley Networks have also been imaged with THEMIS. The following observations have been noted: Narrow, incised, discontinuous inner channels with finer grained materials seen on the floors of many valley networks such as Bahram and Nanedi Valles. Stripped channel floors suggesting exhumation of the channel. Valley network dissection also appears much more prevalent in some regions (Libya Montes) than has ever been seen before. This suggests prolonged fluvial activity. Fluvial deposits are also seen at the mouths of many valley networks such as Samara Vallis and an unnamed channel. These terminal deposits are interpreted to be fans. Gusev Crater is a candidate MER landing site and THEMIS is providing new information on this

Rice, J.; Christensen, P.; Malin, M.; McEwen, A.

2003-04-01

249

Modeling the implications of fluvial erosion and bank failures on gully development and growth  

NASA Astrophysics Data System (ADS)

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.

Istanbulluoglu, E.; Flores, H.; Bras, R.; Tucker, G.

2003-12-01

250

Distinguishing Long-Term Controls on Fluvial Architecture in the Lance Formation, Bighorn Basin, Wyoming  

NASA Astrophysics Data System (ADS)

Allogenic processes are considered a prime control on the stratigraphic distribution of channel bodies, however, recent studies have indicated that autogenic stratigraphic organization may occur within fluvial systems on basin- filling time scales (105-106 years). Groupings or clusters of closely-spaced channel bodies can be produced by several different mechanisms, including both allogenic and autogenic processes. Commonly, sand- dominated intervals in stratigraphic successions are interpreted as incised-valley fills produced by base-level changes. In contrast, long-timescale organization of river avulsion can generate similar stratigraphic patterns. For example, sand-dominated intervals in the fluvial Lance Formation (Maastrichtian; Bighorn Basin, WY) have been interpreted as incised-valley fills formed during sea-level lowstand. However, closely-spaced sand bodies in the Ferris Formation (Lance equivalent; Hanna Basin, WY) are interpreted as aggradational in origin, and have been compared to autogenic avulsion stratigraphy produced in experimental basins. We evaluate the Lance Formation in the southern Bighorn Basin in an effort to determine whether these sand-dominated intervals are truly incised- valley fills resulting from sea-level changes, or if they were generated by autogenic processes. The Lance Formation crops out in the western and southern margins of the basin, exposing relatively proximal and distal portions of the system. By comparing alluvial architecture between exposures, we evaluate similarities and differences from upstream to downstream and look for evidence of intrinsic and extrinsic controls on deposition. In both localities, the Lance Formation comprises multi-story sheet sandstones and smaller, single-story sandstones. Observed changes from upstream to downstream in the system include: 1) increasing paleoflow depths (from ~30-60 cm to ~70-120 cm); 2) decreasing preservation of fine-grained material within channel bodies; 3) increasing proportion of amalgamated, multi-story sand bodies; and 4) increasing lateral continuity of multi-story sand bodies. These results indicate that upstream, channel-body spacing is dominantly controlled by aggradational processes and may be the result of autogenic avulsion clustering, whereas downstream, evidence of incision and amalgamation indicate that base-level may have limited and controlled sand-body architecture.

McHarge, J. L.; Hajek, E. A.; Heller, P. L.

2007-12-01

251

Human impacts on fluvial systems - A small-catchment case study  

NASA Astrophysics Data System (ADS)

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.

Pöppl, Ronald E.; Glade, Thomas; Keiler, Margreth

2010-05-01

252

Relative importance of fluvial and glacial erosion in shaping the Chandra Valley, western Himalaya, India  

NASA Astrophysics Data System (ADS)

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.

Eugster, Patricia; Thiede, Rasmus C.; Scherler, Dirk; Codilean, Alexandru T.; Strecker, Manfred

2013-04-01

253

Fluvial engineering works in the river bed of the Middle Loire  

NASA Astrophysics Data System (ADS)

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.

Nabet, Fouzi

2010-05-01

254

Pleistocene tectonics inferred from fluvial terraces of the northern Upper Rhine Graben, Germany  

NASA Astrophysics Data System (ADS)

This study of fluvial terraces of the River Rhine and tributaries aims to search for indications of Pleistocene tectonic activity. The study area includes the northern Upper Rhine Graben (URG), the Mainz Basin and the adjacent Rhenish Massif with the Middle Rhine Valley. High rates of Quaternary surface processes, large amount of human modifications, relatively slow tectonic deformation and presently low intra-plate seismic activity characterize this area. Therefore, the records of relatively slow tectonic deformation are less well preserved and thus difficult to detect. This study uses the relative position of fluvial terraces to determine the more local effects of fault movements on the terraces and to evaluate their displacement rates and patterns. The research is based on a review of previous terrace studies and new terrace mapping from the eastern Mainz Basin and the bordering URG using topographic map interpretations and field observations. This newly mapped sequence of terrace surfaces can be correlated to other terraces in the vicinity on the basis of relative height levels. Terrace correlation between the western Mainz Basin and Middle Rhine Valley relies on a single chronostratigraphic unit (Mosbach sands) and additional relative height correlations. This is the first study to present a continuous correlation of terraces from the western margin of the URG to the Rhenish Massif and enables the study of the transition from the subsiding graben to the uplifted Rhenish Massif. By means of a longitudinal profile, which ranges from the URG to the Rhenish Massif, the influence of individual fault movements on the terrace levels and the large-scale regional uplift is demonstrated. It is evident from the profile that the uplift of Early to Middle Pleistocene terraces increases northwards, towards the Rhenish Massif. The uplift was diachronic, with a significant pulse occurring first in the northern URG (Lower Pleistocene) and later in the Rhenish Massif (Middle Pleistocene). The largest vertical displacements are recorded for the boundary fault separating the Mainz Basin and the Rhenish Massif (Hunsrück Taunus Boundary Fault) and for faults bounding the northeastern Mainz Basin. The motions and displacement rates calculated for individual faults indicate deformation rates in the order of 0.01 0.08 mm/year. At this stage, the calculation of displacement rates depends mostly on a single dated stratigraphic unit. Additional dating of terrace deposits is urgently needed to better constrain the temporal development of the terrace sequence and the impact of tectonic movements.

Peters, Gwendolyn; van Balen, Ronald T.

2007-02-01

255

The River Orontes in Syria and Turkey: Downstream variation of fluvial archives in different crustal blocks  

NASA Astrophysics Data System (ADS)

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 Da?? 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.

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

256

Geology and Petrophysical Characterization of the Ferron Sandstone for 3-D Simulation of a Fluvial-Deltaic Reservoir  

SciTech Connect

The objective of this project is to develop a comprehensive, interdisciplinary, and quantitative characterization of a fluvial-deltaic reservoir which will allow realistic inter-well and reservoir-scale modeling to be constructed for improved oil-field development in similar reservoirs world-wide. The geological and petrophysical properties of the Cretaceous Ferron Sandstone in east-central Utah will be quantitatively determined. Both new and existing data will be integrated into a three-dimensional representation of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Four activities continued this quarter as part of the geological and petrophysical characterization of the fluvial-deltaic Ferron Sandstone in the Ivie Creek case-study area: (1) regional stratigraphic interpretation, (2) case-study evaluation, (3) reservoir modeling, and (4) technology transfer.

Ann Mattson; Craig B. Forster; Paul B. Anderson; Steve H. Snelgrove; Thomas C. Chidsey, Jr.

1997-05-20

257

Non-marine successions in the northwestern part of Kyongsang Basin (Early Cretaceous): Fluvial styles and stratigraphic architecture  

Microsoft Academic Search

Non-marine successions in the northwestern part of Kyongsang Basin (Early Cretaceous) are divided into successive stratigraphic\\u000a units based on facies assemblages and architecture of sandstone bodies. In the present study, two stratigraphic units (Sinpyong-Anpyong\\u000a and Jotap units) are documented in detail in terms of fluvial architecture. The Sinpyong-Anpyong unit is divided into thick\\u000a sandstone, thin sandstone, and mudstone-dominated bodies, representing

Hyung Rae Jo

2003-01-01

258

Lateglacial/early Holocene fluvial reactions of the Jeetzel river (Elbe valley, northern Germany) to abrupt climatic and environmental changes  

NASA Astrophysics Data System (ADS)

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.

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

259

The Role of Bed Coverage in Reducing the Area Dependence of Fluvial Incision: Implications for the Maximum Relief of Mountains.  

NASA Astrophysics Data System (ADS)

Analytical models of the coupled behavior between fluvial incision and wedge tectonics predict that the dependence of fluvial incision on drainage area is an important factor for understanding how climate (through precipitation) affects the height of active mountain belts. These models use a stream-power formulation I=KAmS^n to represent fluvial incision, but this equation is only an approximation of the many processes that control fluvial incision. Although stream power is widely applied, it is not well tested. Using first principles and scaling laws for channel flow, the value of m in the stream-power equation is derived to be between 0.3 and 1.0. Our contribution here is to consider empirical estimates of m and n, which we will refer to as ? and ? . These estimates are made by fitting a power-law function to slope, area, and incision rate data and are independent from assumptions about the incision process. We use data from both natural settings (the Clearwater River, Washington State, USA, and the Lachlan River, SE Australia) and synthetic examples obtained using the CHILD landscape-evolution model. In both of the natural settings, all estimates of ? are less than 0.2 and sometimes negative. Likewise for the simulated landscapes, when sediment load is included in the incision model and uplift varies spatially, power-law estimates produce a wide range of ? values and also include negative values. The CHILD model demonstrates that the estimated ? is quite different from the value of m used in the model calculation. The reason seems to be that the bed-coverage effect is correlated with drainage area for these examples. The results raise the question of what parameter values should be used in coupled analytical models. If the empirical estimates are relevant, then the low-area dependence of incision rate (as indicated by estimates of ? ) suggests that climate plays a very weak role in controlling the height of mountains.

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

2004-12-01

260

Pluvial and fluvial flooding: integration in probabilistic flood hazard assessment using a coupled rainfall-discharge generator  

NASA Astrophysics Data System (ADS)

Unlike fluvial flooding, pluvial flooding can occur almost anywhere, especially in areas with depressions in the topography and flow paths on the surface. Pluvial flooding is defined as flooding that results from rainfall-generated overland flow before the water enters a river. It is usually associated with rainstorm events >30mm/h. Although a pluvial flood event may be limited to a relatively small area, it can potentially lead to exceptionally high losses. In the UK, for instance, 40% of the property damage from the large-scale autumn 2000 floods was related to properties outside the indicative flood zone maps. To date, probabilistic flood hazard assessment has mainly focused on fluvial flooding, with the hazard of pluvial flooding commonly being treated separately, neglected or oversimplified. A new approach for simultaneously assessing the joint hazard of pluvial and fluvial flooding is suggested. It comprises the application of a copula-based stochastic rainfall-discharge generator. Inundation is simulated with ANUGA Hydro, an open source 2D hydrodynamic model. ANUGA Hydro is based on a finite volume method to solve the shallow water equation and it is suitable for modelling rainstorms and hydrographs. Two medium catchments in Europe have been examined for their suitability for the application and validation of the proposed approach. This new probabilistic approach to simultaneously determine the hazard of pluvial and fluvial flooding is a step forward towards the development of more reliable, all-embracing probabilistic flood hazard and risk assessment techniques. This is especially true as - according to the IPCC - the risk of pluvial flooding is likely to increase even further across most of Europe due to climate change. Moreover, pluvial flooding clearly falls under the scope of the European Flood Directive 2007/60/EC.

Breinl, K.

2012-04-01

261

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

Microsoft Academic Search

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

William A White; Robert A Morton; Charles W Holmes

2002-01-01

262

Inverted fluvial features in the Aeolis-Zephyria Plana, western Medusae Fossae Formation, Mars: Evidence for post-formation modification  

NASA Astrophysics Data System (ADS)

The Aeolis and Zephyria Plana contain the western-most portion of the Medusae Fossae Formation (MFF), an enigmatic and extensive light-toned deposit located in the Martian equatorial region and dated from the Hesperian to Amazonian epochs. This area hosts a large population of sinuous ridges (SRs), interpreted as inverted fluvial features, formed by precipitation, indurated by chemical cementation, buried by subsequent deposition, and finally exhumed. This interpretation of SRs as uniformly fluvial represents a modification to an earlier hypothesis for one particular SR of possible glaciofluvial (i.e. esker) formation. These SRs provide a tool to investigate the degree and character of post-fluvial modification processes in this region. We combined digital terrain models made from Context Camera (CTX) and High Resolution Imaging Science Experiment (HiRISE) stereo image pairs with individual data points from the Mars Orbiter Laser Altimeter (MOLA) to estimate relief, cross-sectional profiles, longitudinal profiles and slope directions of selected SRs. Longitudinal profiles of several SRs display undulations with amplitudes of up to order 100 m. While some of the lower amplitude undulations may be due to differential erosion, undulations having amplitudes in excess of SR relief require alternative explanations. Our combined morphologic and topographic analysis suggests that multiple post-flow processes, including compaction of the deposits and tectonic displacements, have modified the original SR profiles. Specification of the type(s) and magnitudes of these modification processes will contribute to understanding both the potential of post-flow modification of fluvial profiles elsewhere on Mars as well as the nature and properties of the MFF.

Lefort, Alexandra; Burr, Devon M.; Beyer, Ross A.; Howard, Alan D.

2012-03-01

263

Holocene interdependences of changes in sea surface temperature, productivity, and fluvial inputs in the Iberian continental shelf (Tagus mud patch)  

Microsoft Academic Search

Sea surface temperature (SST), marine productivity, and fluvial input have been reconstructed for the last 11.5 calendar (cal) ka B.P. using a high-resolution study of C37 alkenones, coccolithophores, iron content, and higher plant n-alkanes and n-alkan-1-ols in sedimentary sequences from the inner shelf off the Tagus River Estuary in the Portuguese Margin. The SST record is marked by a continuous

Teresa Rodrigues; Joan O. Grimalt; Fátima G. Abrantes; Jose A. Flores; Susana M. Lebreiro

2009-01-01

264

Integrating field measurements and flume experiments for analysing fluvial bedload transport and channel morphodynamics in steep mountain streams  

NASA Astrophysics Data System (ADS)

Fluvial bedload transport, temporal storage of material and channel morphodynamics have high importance for sedimentary budgets of steep catchments and steep mountain streams. In addition, headwater catchments and steep mountain streams can be relevant sediment sources for lowland river systems. Since 2004 extended and interdisciplinary field investigations on fluvial bedload transport and channel morphodynamics have been conducted in a number of selected stream segments in supply-limited fluvial systems in the inner Nordfjord (Erdalen and Bødalen drainage basins) in western Norway. A range of different methods and techniques have been used. Field studies in the Erdalen drainage basin (79.5 km2) and the Bødalen drainage basin (60.1 km2) have included (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 channel segments. Additional field studies with impact sensors were carried out in selected transport-limited fluvial systems in the Coast Mountains of British Columbia (Canada) in 2010 and 2011. The field studies have been combined with flume experiments for calibration of field measurements, especially for the calibration of the measurements that have been carried out with impact sensors in Norway and Canada. As a key achievement, the entire range of different bedload component grain sizes can be covered by the applied combination of techniques. The flux of bedload material can be quantified and is related to the spatio-temporal variability of sediment supply / availability within the drainage basins and to temporal sediment storage within the channel systems.

Beylich, Achim A.; Laute, Katja; Liermann, Susan

2013-04-01

265

A conservative, semi-Lagrangian fate and transport model for fluvial systems—II. numerical testing and practical applications  

Microsoft Academic Search

In this paper a semi-Lagrangian fate and transport model for fluvial systems (DISCUS) is tested against exact solutions and against field data. Benchmark comparisons with an exact solution for the uniform advection–dispersion–decay equation (single reacting species) show that DISCUS possesses excellent accuracy characteristics over a wide range of time step sizes with accuracy usually highest at Courant numbers in excess

J. Russell Manson; Steve G Wallis; Dali Wang

2000-01-01

266

PREDICTION OF ATMOSPHERIC  13CO2 USING PLANT CUTICLE ISOLATED FROM FLUVIAL SEDIMENT: TESTS ACROSS A GRADIENT IN SALT CONTENT  

Microsoft Academic Search

In order to test the assertion that the carbon-isotopic composition of the ancient atmosphere (13CO2) can be reconstructed from the car- bon-isotopic composition of fossil terrestrial plant tissues across a variety of environments, the 13C value of land-plant tissues isolated from modern fluvial sediments was compared to that of today's at- mosphere. Plant stem and leaf fragments were isolated from

A. HOPE JAHREN; NAN CRYSTAL ARENS

2009-01-01

267

Facies and sequence stratigraphic modeling of a Upper Pliocene–Lower Pleistocene fluvial succession (Valdelsa Basin, central Italy)  

NASA Astrophysics Data System (ADS)

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.

Benvenuti, Marco; Del Conte, Sara

2013-08-01

268

Influence of a large fluvial island, streambed, and stream bank on surface water-groundwater fluxes and water table dynamics  

NASA Astrophysics Data System (ADS)

Substantial research on how hydraulic and geomorphologic factors control hyporheic exchange has resulted in reasonable process understanding; however, the role of fluvial islands on the transient nature of spatial flux patterns remains elusive. We used detailed field observations of the Truckee River, Nevada from 2003 to 2009 to quantify fluid flux between the river and a fluvial island, the streambed, and the adjacent stream bank. We constructed a 3-D numerical flow and heat transport model to further quantify the complex flow paths. Our study expands on previous research typically confined to less comprehensive scales and dimensions, and highlights the transient multidimensionality of the flow field. In fact, 1-D vertical streambed flux estimates indicated that the channel bar tail displayed the highest upward flux throughout the summer; however, 3-D model results indicated that the horizontal contribution was two orders of magnitude higher than the vertical contribution. The channel bar net flux is typically 1.5 orders of magnitude greater than the adjacent stream banks and an order of magnitude less than net streambed fluxes, indicating significant differences in river-aquifer interactions between each of the geomorphic units. Modeling simulations further indicated that the channel bar induces 6 times more fluid flux than an identical location without a fluvial island, consistent with flux estimates from a nearby river restoration location. Moreover, event-based and seasonal transient antecedent moisture and near-stream storage conditions contribute to multidimensional river-groundwater interactions. These results suggest that fluvial islands are a key driver and significant component of river-groundwater interactions and hyporheic flow.

Shope, Christopher L.; Constantz, James E.; Cooper, Clay A.; Reeves, Donald M.; Pohll, Greg; McKay, W. Alan

2012-06-01

269

Accommodation-based controls on fluvial-deltaic reservoir compartmentalization: Examples from the Oligocene Frio Formation, south Texas  

Microsoft Academic Search

Accurate prediction of compartment architecture and intracompartment heterogeneity is necessary to locate and recover the estimated 15 billion barrels of mobile oil remaining in U.S. fluvial-dominated deltaic reservoirs. To improve this prediction, facies-specific relationships between accommodation trends and sand-body architecture that were established by outcrop studies in the western interior were Successfully applied in a study of Oligocene Frio Formation

Paul R. Knox

1996-01-01

270

Origin of ferricretes in fluvial-marine deposits of the Lower Cenomanian Bahariya Formation, Bahariya Oasis, Western Desert, Egypt  

Microsoft Academic Search

The type section of the Lower Cenomanian Bahariya Formation at Gebel El-Dist (Bahariya Oasis, Western Desert), Egypt, comprises claystones, mudstones, siltstones and sandstones deposited in fluvial-deltaic coastal plain, lagoonal, estuarine and shallow marine environments. The formation is characterized by an abundance of ferruginous sandstones that locally weather to form prominent iron crusts. These centimeter to decimeter-scale ferruginous horizons display a

Lawrence H. Tanner; Mohamed A. Khalifa

2010-01-01

271

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

USGS Publications Warehouse

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.

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

2010-01-01

272

Deciphering the Late Quaternary fluvial dynamics at the foothill of an active orogen - the example of the Transcaucasian depression in eastern Georgia  

NASA Astrophysics Data System (ADS)

Generally, the dynamics of fluvial systems can be triggered by climate, tectonics, anthropogenic activity or internal mechanisms. The lowland of the Transcaucasian depression is located between the Greater Caucasus in the north and the Lesser Caucasus in the south. Both mountainous massifs form a part of the Alpidic orogenic belt and are thus characterized by a high tectonic activity. During the Weichselian glaciation, due to their altitude >3000 m the massifs were strongly glaciated. During the last years, we investigated fluvial sediment sequences of several rivers that originate from the mountain belts and cross the eastern semi-arid part of the Transcauscasian depression towards the Caspian Sea (e.g. Algeti, Khrami, Kura, Alazani), in order to decipher changes of their fluvial dynamics during the past. The investigated sediments of Late Pleistocene and Holocene age show thicknesses up to 50 m and are mostly well outcropped. Our morphologic, sedimentologic and chronostratigraphic investigations of different sediment sequences demonstrate distinctive changes of the fluvial dynamics between the Late Pleistocene and the Holocene, and show that high-frequent Holocene changes of the fluvial pattern of the rivers are probably linked to climatic and/or anthropogenic triggers. Additionally, on a longer time scale the fluvial dynamics of the rivers is obviously controlled by ongoing tectonic processes.

von Suchodoletz, Hans; Faust, Dominik

2013-04-01

273

Geomorphological and sedimentological features in Quaternary fluvial systems affected by solution-induced subsidence (Ebro Basin, NE-Spain)  

NASA Astrophysics Data System (ADS)

The Quaternary evolution and the morpho-sedimentary features of some of the most important rivers in Spain (Ebro and Tagus rivers among others) have been controlled by subsidence due to alluvial karstification of the evaporitic bedrock. The subsidence mechanism may range from catastrophic collapse to slow sagging of the alluvium by passive bending. In the Ebro Basin, the mechanisms and processes involved in karstic subsidence were studied through the analysis of present-day closed depressions as well as through old subsidence depressions (palaeocollapses and solution-induced basins) and associated deformations recorded in the Quaternary alluvial sediments. The Gállego-Ebro river system is presented as a case study of channel adjustments and geomorphic and sedimentary evolution of fluvial systems in dissolution-induced subsidence areas. In this fluvial system, evaporite dissolution during particular Quaternary time intervals (namely early and middle Pleistocene) have lead to the development of a solution-induced basin, approximately 30 km-long by 8 km-wide, filled by Quaternary deposits with a total thickness in excess of 190 m. The main river response to balance the subsidence in the alluvial plain was aggradation in the central reach of the subsiding area, and degradation both in the upstream reach and in the valley sides where alluvial fans and covered pediments may prograde over the fluvial sediments. The main sinking areas are recognized in the sedimentary record by anomalous thickenings in the alluvial deposits and fine-grained sediments deposited in backswamp and ponded areas.

Benito, Gerardo; Gutiérrez, Francisco; Pérez-González, Alfredo; Machado, Maria J.

2000-06-01

274

Riparian vegetation patterns in relation to fluvial landforms and channel evolution along selected rivers of Tuscany (Central Italy)  

USGS Publications Warehouse

Riparian vegetation distribution patterns and diversity relative to various fluvial geomorphic channel patterns, landforms, and processes are described and interpreted for selected rivers of Tuscany, Central Italy; with emphasis on channel evolution following human impacts. Field surveys were conducted along thirteen gauged reaches for species presence, fluvial landforms, and the type and amount of channel/riparian zone change. Inundation frequency of different geomorphic surfaces was determined, and vegetation data were analyzed using BDA (binary discriminate analysis) and DCA (detrended correspondence analysis) and related to hydrogeomorphology. Multivariate analyses revealed distinct quantitative vegetation patterns relative to six major fluvial geomorphic surfaces. DCA of the vegetation data also showed distinct associations of plants to processes of adjustment that are related to stage of channel evolution, and clearly separated plants along disturbance/landform/soil moisture gradients. Species richness increases from the channel bed to the terrace and on heterogeneous riparian areas, whereas species richness decreases from moderate to intense incision and from low to intense narrowing. ?? 2007 by Association of American Geographers.

Hupp, C. R.; Rinaldi, M.

2007-01-01

275

Regional distribution of wave- and fluvial-dominated deltaic deposits of Olmos formation (upper Cretaceous) in Maverick basin, southwest Texas  

SciTech Connect

Regional subsurface analysis in southwest Texas indicates that the Olmos Formation (Gulfian) was deposited by a complex of wave- and fluvial-dominated delta systems in two depocenters. Sediment influx was from the north and northwest. Five deltaic submits, A through E, were deposited in the western depocenter. Three other deltaic wedges (F, G, H) formed the second depocenter farther east in present-day Frio and LaSalle Counties. Subsidence was greater in the western half of the Maverick basin where thickest (1,300 ft; 395 m) deltaic sediments were deposited. Lower Olmos strata represent a succession from wave-reworked, strike-elongate deltas of subunit A, similar to those of the underlying San Miguel Formation, to fluvial-dominated, dip-elongate deltas of subunits B and C. Extensive (1200 mi/sup 2/ or 3100 km/sup 2/ in Texas) aggradational floodplain deposits of B and C are characterized by diverse electric-log patterns; variation in log character is a response to complex depositional facies on the delta platform. Downdip, toward the Cretaceous shelf edge, delta-plain facies merge with upward-coarsening delta-front sandstones. Uppermost subunits D and E were deposited by a prograding barrier-island system in an interdeltaic embayment marginal to high constructive deltas of the easter depocenter. Lagoonal and fluvial-channel deposits are recognized from cores. Eastward migration of deposition was accompanied by an abrupt change of depositional style in the western depocenter from deltaic to coastal-interdeltaic.

Ambrose, W.; Tyler, N.

1984-04-01

276

Origin of arsenic pollution in Southwest Tuscany: comparison of fluvial sediments.  

PubMed

The Colline Metallifere in SW Tuscany are characterized by strong anomalies in arsenic concentrations and distribution. The area is sparsely populated and largely wild, though it has been subject to human impact due to mining and metal processing since Etruscan and Roman times. In the Middle Ages it was exploited intensively for silver and copper. Until 1995, pyrite (FeS2) was mined and roasted to produce sulphuric acid and iron. Hypotheses based on geological and mineralogical factors formulated in the last 20 years have failed to explain the peculiar distribution of arsenic in the Colline Metallifere. Here we report preliminary results of widespread sampling and analysis of the fluvial sediments of rivers originating in this mining area. The data was analysed in relation to the archaeological features of the area, since the presence of ancient mining and ore processing sites can shed light on the peculiar distribution of arsenic. Comparison of data from two rivers and their respective contaminated and uncontaminated coastal lagoons also clarified the general mechanisms of arsenic mobility, pinpointing the source of arsenic contamination. The study methods also promise to be useful for discovering unknown archaeological sites. PMID:16485657

Donati, Alessandro; Pulselli, Federico Maria; Riccobono, Francesco; Dallai, Luisa; Francovich, Riccardo; Tiezzi, Enzo

277

Fluvial stacking due to plate collision and uplift during the Early Pleistocene in Cyprus  

NASA Astrophysics Data System (ADS)

Southern Cyprus is situated within a mosaic terrane that has been fragmented between the northward drifting African and Arabian plates and the Eurasian plate. Enormous uplift of the earth mantle in the Tróodos Mountains is explained by two models. The subduction model explains subduction along the Cyprean arc to be the driving force for uplift whereas after the restraining bend model westward squeezing of Cyprus along strike-slip faulting is responsible for the enormous uplift at restraining bends. Since its emergence as an island in early Miocene times, landscape formation on Cyprus has been strongly controlled by this uplift. Until the Plio-Pleistocene, a strait belt separated the southern unroofed ophiolitic core region-the Tróodos Mountains-from the folded Kyrenia range to the north. This former sea basin, nowadays the Mesaoría Basin, is linked with the Tróodos Mountains by a dissected glacis with a thick cover of river deposits. The highest and oldest river deposits (Apalós Formation) were studied in the Vlokkariá hill southwest of Lefkosía. The 45.5 m thick Apalós Formation of Early Pleistocene age exhibits 24 sedimentary units (Fluviatile Series). Their magnetostratigraphical characters align with the Matuyama chron including the Olduvai and Jaramillo subchrons thus comprising about 1.15 Ma within the Early Pleistocene. This fluvial stack indicates a very flat and deeply lying river environment flowing from a slowly uplifting Tróodos hinterland. It happened during the end of Early Pleistocene when the enhanced Tróodos uplift started the dissection of the stacked river plain.

Schirmer, Wolfgang; Weber, Josef; Bachtadse, Valerian; Boudagher-Fadel, Marcelle; Heller, Friedrich; Lehmkuhl, Frank; Panayides, Ioannis; Schirmer, Ursula

2010-12-01

278

Investigating Spatial Interpolation of Light Detection and Ranging Data for Analyzing Fluvial Geomorphic Properties of Streams  

NASA Astrophysics Data System (ADS)

Streams are intricate components of the landscape system that vary across temporal and spatial scales while transporting and storing water, sediment, energy, nutrients as well as aquatic and terrestrial species from one part of the system to another. Such changes have traditionally been captured with extensive expert assessment and/or remote sensing analysis (i.e. photo interpretation). In collaboration with the Vermont Agency of Natural Resources River Management Program, this study aims to enhance the capabilities of traditional remote sensing studies by incorporating Light Detection and Ranging (LiDAR) data in the geomorphic assessment of fluvial channels to quantify stream adjustment properties and gain insight into a stream's state of dynamic equilibrium with greater accuracy than traditional methods. A series of 18 digital elevation models (DEM) were generated using three interpolation methods (inverse distance weighting (IDW), natural neighbor (NN), and ordinary kriging), varying raster grid cell sizes (1, 2 and 3m) and different amounts of LiDAR data (bare earth data alone and bare earth with additional reflective data that reduce the mean point spacing) and compared with survey data (n = 689) to determine the optimal interpolation parameters for an agricultural study area, a portion of Allen Brook watershed in northern Vermont. Through analytical comparison, 1m IDW with the additional reflective data was the optimal method for minimizing error metrics but 1m NN (with additional reflective data) was best for retaining maximum elevation range, computational simplicity, and identifying small stream channels.

Besaw, L. E.; Pelletier, K.; Morrissey, L. A.; Rizzo, D. M.

2007-12-01

279

Infiltration in unsaturated layered fluvial deposits at Rio Bravo : photo essay and data summary.  

SciTech Connect

An infiltration and dye transport experiment was conducted to visualize flow and transport processes in a heterogeneous, layered, sandy-gravelly fluvial deposit adjacent to Rio Bravo Boulevard in Albuquerque, NM. Water containing red dye followed by blue-green dye was ponded in a small horizontal zone ({approx}0.5 m x 0.5 m) above a vertical outcrop ({approx}4 m x 2.5 m). The red dye lagged behind the wetting front due to slight adsorption thus allowing both the wetting front and dye fronts to be observed in time at the outcrop face. After infiltration, vertical slices were excavated to the midpoint of the infiltrometer exposing the wetting front and dye distribution in a quasi three-dimensional manner. At small-scale, wetting front advancement was influenced by the multitude of local capillary barriers within the deposit. However at the scale of the experiment, the wetting front appeared smooth with significant lateral spreading {approx} twice that in the vertical, indicating a strong anisotropy due to the pronounced horizontal layering. The dye fronts exhibited appreciably more irregularity than the wetting front, as well as the influence of preferential flow features (a fracture) that moved the dye directly to the front, bypassing the fresh water between.

Brainard, James Robert; Glass, Robert John, Jr.

2007-08-01

280

An environmental model of fluvial tufas in the monsoonal tropics, Barkly karst, northern Australia  

NASA Astrophysics Data System (ADS)

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.

Carthew, K. D.; Taylor, M. P.; Drysdale, R. N.

2006-01-01

281

Fluvial trace fossils in the Middle Siwalik (Sarmatian-Pontian) of Darjeeling Himalayas, India  

NASA Astrophysics Data System (ADS)

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.

Chakraborty, Abhijit; Hasiotis, Stephen T.; Ghosh, Bhaskar; Bhattacharya, Harendra Nath

2013-08-01

282

Geology of Hebrus Valles and Hephaestus Fossae, Mars: evidence for basement control of fluvial patterns  

SciTech Connect

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 segments which branch and cross downslope but have high junction angles. Locally, the channel pattern is polygonal. HF are parallel to HV but are considerably deeper and longer (600 km). HF also originate in a depression, but to the NW they terminate near the gradational boundary between the knobby plains and polygonally fractured terrain of Utopia Planitia. The valley pattern has led some to suggest that HF are tectonic features. It is suggested that like HV, HF are also of fluvial origin. Downcutting to, or subsurface flow at this pre-existing surface red to a channel pattern that was strongly controlled by the polygonal troughs buried beneath the younger knobby plains materials.

Christiansen, E.H.

1985-01-01

283

Fluvial processes, morphology and sediment budgets in the Coon Creek Basin, WI, USA, 1975-1993  

NASA Astrophysics Data System (ADS)

Sediment budget processes in Coon Creek, Wisconsin, from 1975 to 1993 changed only moderately, generally continuing the trends that were evident in 1975. Perhaps most importantly, sediment yield to the Mississippi River appears to be unabated, with much of this clearly coming from storage loss, especially stream bank erosion. Vertical accretion continued on the lower (new) floodplains inset within their meander plains in tributaries and the upper main valley. The lower main valley also continued to aggrade but at the rate of about 6% of that occurring in the 1920s and 1930s. The major revision from earlier studies is that the upper main valley is a less significant net source of sediment than previously thought and the earlier prognostications of it being a significant net source of sediment in the future may be wrong. Perturbations have been caused by changes of riparian vegetation and, much more importantly, by the introduction of fish shelter structures and protected cut banks along the stream system reaching downstream to the end of the upper main valley. Because these structures do not permit natural stream migration, bank erosion and downstream sediment transfer, the Coon Creek basin has lost much of its suitability as a natural laboratory of fluvial processes.

Trimble, Stanley W.

2009-07-01

284

Mechanically infiltrated clays: recognition and influence in fluvial reservoirs of Reconcavo basin, Brazil  

SciTech Connect

Fluvial sandstones and conglomerates of the Sergi Formation (Jurassic) are the main reservoirs of the Reconcavo basin in northeastern Brazil. These reservoirs contain significant amounts of interstitial detrital clays resulting from early diagenetic mechanical infiltration. The infiltration developed under arid/semiarid conditions, where the lowered water table allowed muddy waters of episodic runoff to infiltrate through the coarse alluvium. The main clay concentrations occurred in the upper phreatic zone and in proximity to sources of influent seepage. It is difficult to identify infiltrated clays in ancient sedimentary rocks due to a lack of well-established petrographic criteria. In this work, a series of petrographic criteria is proposed to recognize these clays in clastic reservoirs. These criteria include the anisophachous coatings of tangentially accreted lamellae and the geometric patterns developed due to shrinkage. The infiltrated clays are among the main controls of reservoir properties, and the horizons of maximum clay concentration are the main internal barriers in most Sergi reservoirs. In general, infiltrated clays damage reservoir quality by creating macroheterogeneities and microheterogeneities, by decreasing recovery efficiency and permeability, and by increasing water saturation. Also, they can cause formation damage either by their swelling properties or through the migration of loose particles left by shrinkage. As demonstrated in the Sergi Formation, infiltrated clays must be adequately identified for the definition of proper procedures for drilling, completion, reservoir development, and EOR programs.

Moraes, M.A.S.; De Ros, L.F.

1989-03-01

285

New aspects of deformed cross-strata in fluvial sandstones: Examples from Neoproterozoic formations in northern Norway  

NASA Astrophysics Data System (ADS)

Extensive (20 200 m long) exposures of tabular cross-sets in Neoproterozoic fluvial sandstone in Northern Norway demonstrate that deformed cross-strata, in the form of recumbently folded cross-strata with associated massive sand, are localized features passing in both up- and down-current direction into undeformed, concave-upward or sigmoidal cross-strata. The deformation occurs in down-current inclined, tangential wedge-shaped zones beneath reactivation surfaces, and less commonly as flat-topped lenticular zones. The localized nature of the sediment deformation is attributed to local liquefaction below the top of the bed in the case of the flat-topped lenses and at the dune front in the case of the more common tangential wedges. The position of the flat-topped lenses suggests deformation by the shear stress of high-velocity, suspension-laden currents. Although liquefaction of the dune front implies the action of gravity forces, it is argued that the fluvial currents were the main driving force at the instant of bed liquefaction. Post-folding gravitational shearing probably enhanced the deformation within the upper part of the wedges, with their long, flat-lying toeset resulting from redeposition of downslope-moving liquefied sand. The down-current alternation of deformed tangential wedges and undeformed cross-strata suggests that the mechanism that triggered the liquefaction of the dune lee side was related to the fluvial system itself and hence was of autokinetic origin. The tabular cross-sets have previously been interpreted as a product of the dune upper-stage plane-bed flow regime. In this flow context, it can be speculated that the liquefaction and deformation occurred when the flow conditions approached the plane-bed phase, probably inducing a highly differential turbulent pattern and pressure fluctuations sufficient to liquefy the fine/medium sand. The small flat-topped deformation lenses also suggest liquefaction by cyclic loading, whereas the solitary nature of the large lenses may, alternatively, be the result of impulsive loading from bank collapse. In less well-exposed fluvial successions, the auto- or allokinetic origin of recumbently folded cross strata may be difficult to determine. However, the common occurrence of recumbent folds in cross-stratified fluvial sandstones and their virtual absence in marine cross-stratified deposits suggests strongly that, in the majority of cases, the deformation was autokinetic, resulting from flow phenomena typical of river channels. This kind of deformation structure should thus not be attributed to an allokinetic seismic triggering mechanism unless independent evidence of fault activity can be documented.

Røe, Signe-Line; Hermansen, Marita

2006-05-01

286

Eradication and Surveillance of 'Caulerpa taxifolia' within Agua Hedionda Lagoon, Carlsbad, California. Fifth Year Status Report, January to December 2005.  

National Technical Information Service (NTIS)

On June 12, 2000 the first known infestation in the Western Hemisphere of the invasive strain of the tropical marine alga, Caulerpa taxifolia, was discovered in Agua Hedionda Lagoon, in Carlsbad, California. This document reports the results of the fifth ...

2006-01-01

287

Fluvial response in a sequence stratigraphic framework: Example from the Montserrat fan delta, Spain  

SciTech Connect

Exceptional exposure of the Montserrat fan-delta system (Eocene) in northeastern Spain provides an excellent framework to evaluate the alluvial response to sea-level changes over two different time scales. The alluvial system contains multiple fifth-order cycles ({approximately}10{sup 4} yr) and eight fourth-order cycles ({approximately}10{sup 4} yr). Fifth-order cycles are characterized by long-distance shoreline migrations and, occasionally, by incised basal scour surfaces but not by changes in fluvial style, lithofacies, or channel stacking pattern. Fourth-order cycles are composed of stacked fifth-order cycles and have non-erosional basal boundaries. Changes in the alluvial system during fourth-order cycles are most pronounced adjacent to shoreline and die away upstream over just a few kilometers--indicating that the base-level signal decays away over the distance of a few backwater lengths. Higher-frequency (fifth-order) changes in relative sea level appear to produce the largest shoreline migrations, but lower-frequency (fourth-order) changes have more impact on the channel stacking architecture of the alluvial systems. Observed changes in alluvial stacking pattern may be most commonly found in tectonically active, rapidly subsiding, foreland basins because of their back-tilted geometry. The authors propose a model in which sediment is trapped in the proximal basin during times of rapid tectonic subsidence and attendant relative sea-level rise. Progradation occurs as erosion rates in the mountain belt increase, and rates of subsidence and relative sea-level rise diminish. Changes in alluvial architecture reflect an increase in sediment flux towards the shoreline as less sediment is trapped upstream. Hence, changes in channel-stacking pattern coincident with transgressions and regressions likely reflect the interplay between subsidence and sediment supply in the proximal part of the basin and are not necessarily driven by eustatic sea-level changes.

Burns, B.A.; Heller, P.L. [Univ. of Wyoming, Laramie, WY (United States). Dept. of Geology and Geophysics; Marzo, M. [Univ. de Barcelona (Spain); Paola, C. [Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Geology and Geophysics

1997-03-01

288

Improved oil recovery in fluvial dominated reservoirs of Kansas--near-term. Annual report  

SciTech Connect

Common oil field problems exist in fluvial dominated deltaic reservoirs in Kansas. The problems are poor waterflood sweep efficiency and lack of reservoir management. The poor waterflood sweep efficiency is due to (1) reservoir heterogeneity, (2) channeling of injected water through high permeability zones or fractures, and (3) clogging of injection wells due to solids in the injection water. In many instances the lack of reservoir management results from (1) poor data collection and organization, (2) little or no integrated analysis of existing data by geological and engineering personnel, (3) the presence of multiple operators within the field, and (4) not identifying optimum recovery techniques. Two demonstration sites operated by different independent oil operators are involved in this project. The Stewart Field is located in Finney County, Kansas and is operated by North American Resources Company. This field was in the latter stage of primary production at the beginning of this project and is currently being waterflooded as a result of this project. The Nelson Lease (an existing waterflood) is located in Allen County, Kansas, in the N.E. Savonburg Field and is operated by James E. Russell Petroleum, Inc. The objective is to increase recovery efficiency and economics in these type of reservoirs. The technologies being applied to increase waterflood sweep efficiency are (1) in situ permeability modification treatments, (2) infill drilling, (3) pattern changes, and (4) air flotation to improve water quality. The technologies being applied to improve reservoir management are (1) database development, (2) reservoir simulation, (3) transient testing, (4) database management and (5) integrated geological and engineering analysis. Results of these two field projects are discussed.

Green, D.W.; Willhite, G.P.; Walton, A.; Schoeling, L.; Reynolds, R.; Michnick, M.; Watney, L.

1996-11-01

289

Fluvial response to Holocene volcanic damming and breaching in the Gediz and Geren rivers, Western Turkey  

NASA Astrophysics Data System (ADS)

This study discusses the complex late Holocene evolution of the Gediz River North of Kula, Western Turkey, when a basaltic lava flow dammed and filled this river valley. Age control was obtained using established and novel feldspar luminescence techniques on sands below and on top of the flow. This constrained the age of the lava flow to 3.0 - 2.1 ka. In addition, 40Ar/39Ar dating was attempted but due a combination of the young age and low potassium content of the basalt this technique was unsuitable. Two damming locations caused by the lava flow have been investigated. The upstream dam caused lake formation and silting of the upstream Gediz. The downstream dam blocked both the Gediz and its tributary, the Geren. The associated lake was not silted up because the upstream dam already trapped all the Gediz sediments. Backfillings of the downstream lake are found 1.5 km upstream into the Geren valley. The downstream dam breached first, after which the upstream dam breached creating an outburst flood that imbricated boulders of approx. 10 m3 size and created an epigenetic gorge. The Gediz lowered its floodplain level with at least 15 m in a short time, triggering landslides, some of which are active until present. The lower reach of the Geren has experienced fast base level lowering and changed regime from meandering to a straight channel. Complex response to base level change is still on-going in both Geren and Gediz catchments. These findings are summarized in a diagram conceptualizing lava damming and breaching events. It is concluded that one lava flow filling a valley floor can block a river several times, leading to different, but interrelated fluvial responses of the same river system to the same lava flow.

van Gorp, Wouter; Veldkamp, Antonie; Temme, Arnaud; Maddy, Darrel; Demir, Tuncer; van der Schriek, Tim; Reimann, Tony; Wallinga, Jakob; Wijbrans, Jan; Schoorl, Jeroen

2013-04-01

290

Linking Surface Morphological Change to Subsurface Fluvial Architecture: What Imprints do big Floods Leave?  

NASA Astrophysics Data System (ADS)

Ideas concerning the origin of alluvial deposits and their paleoenvironmental interpretation have usually resulted in two schools of thought: that such deposits are either the result of ordinary 'day-to-day' processes that acted uniformly through time, or that they are related to rare events that had a disproportionate effect on erosion and deposition rates. Despite the long running debate of gradualism and catastrophism within the Earth Sciences, there is surprisingly little quantitative data to assess what magnitude of event is represented in many fluvial sequences. This paper reports results of a unique natural 'experiment' where surface (digital elevation models obtained from digital photogrammetry) and subsurface (ground penetrating radar, GPR) data were taken immediately prior to, and after, a large (1 in 40 year) flood event that occurred in 2005 on the sand-bed, braided South Saskatchewan River, Canada. We surveyed several reaches of the river both before and after this major flood event, and collected repeat aerial surveys of the entire channel, as well as GPR surveys along identical survey lines. This allows us to examine the morphological change in the channel form during this flood, quantify the probability distributions of bed heights within the channels, and assess the amount of erosion and/or deposition represented within the subsurface architecture. Results indicate that although this high-magnitude flood had a marked geomorphic impact, the style and scale of both scour and deposition were the same as that measured during lower-magnitude, annual, floods. Hence, rather than being a reflection of either frequent or rare events, alluvial deposits in the South Saskatchewan contain the record of both but these different scale events may be virtually indistinguishable in the subsurface alluvial architecture.

Ashworth, P. J.; Best, J. L.; Sambrook-Smith, G. H.; Parker, N.; Lane, S. N.; Lunt, I. A.; Simpson, C. J.; Widdison, P. E.

2008-12-01

291

Evaluation of statistical models for predicting Escherichia coli particle attachment in fluvial systems.  

PubMed

Modeling surface water Escherichia coli fate and transport requires partitioning E. coli into particle-attached and unattached fractions. Attachment is often assumed to be a constant fraction or is estimated using simple linear models. The objectives of this study were to: (i) develop statistical models for predicting E. coli attachment and virulence marker presence in fluvial systems, and (ii) relate E. coli attachment to a variety of environmental parameters. Stream water samples (n = 60) were collected at four locations in a rural, mixed-use watershed between June and October 2012, with four storm events (>20 mm rainfall) being captured. The percentage of E. coli attached to particles (>5 ?m) and the occurrences of virulence markers were modeled using water quality, particle concentration, particle size distribution, hydrology and land use factors as explanatory variables. Three types of statistical models appropriate for highly collinear, multidimensional data were compared: least angle shrinkage and selection operator (LASSO), classification and regression trees using the general, unbiased, interaction detection and estimation (GUIDE) algorithm, and multivariate adaptive regression splines (MARS). All models showed that E. coli particle attachment and the presence of E. coli virulence markers in the attached and unattached states were influenced by a combination of water quality, hydrology, land-use and particle properties. Model performance statistics indicate that MARS models outperform LASSO and GUIDE models for predicting E. coli particle attachment and virulence marker occurrence. Validating the MARS modeling approach in multiple watersheds may allow for the development of a parameterizing model to be included in watershed simulation models. PMID:24075474

Piorkowski, Gregory; Jamieson, Rob; Bezanson, Greg; Hansen, Lisbeth Truelstrup; Yost, Chris

2013-09-12

292

Improved Oil Recovery In Fluvial Dominated Deltaic Reservoirs of Kansas - Near Term  

SciTech Connect

Common oil field problems exist in fluvial dominated deltaic reservoirs in Kansas. The problems are poor waterflood sweep efficiency and lack of reservoir management. The poor waterflood sweep efficiency is due to (1) reservoir heterogeneity, (2) channeling of injected water through high permeability zones or fractures, and (3) clogging of injection wells due to solids in the injection water. In many instances the lack of reservoir management results from (1) poor data collection and organization, (2) little or no integrated analysis of existing data by geological and engineering personnel, (3) the presence of multiple operators within the field, and (4) not identifying optimum recovery techniques. Two demonstration sites operated by different independent oil operators are involved in this project. The Stewart Field is located in Finney County, Kansas and is operated by PetroSantander, Inc. This field was in the latter stage of primary production at the beginning of this project and is currently being waterflooded as a result of this project. The Nelson Lease (an existing waterflood) is located in Allen County, Kansas, in the N.E. Savonburg Field and is operated by James E. Russell Petroleum, Inc. The objective is to increase recovery efficiency and economics in these types of reservoirs. The technologies being applied to increase waterflood sweep efficiency are (1) in situ permeability modification treatments, (2) infill drilling, (3) pattern changes, and (4) air flotation to improve water quality. The technologies being applied to improve reservoir management are (1) database development, (2) reservoir simulation, (3) transient testing, (4) database management, and (5) integrated geological and engineering analysis.

Green, Don W.; McCune, D.; Michnick, M.; Reynolds, R.; Walton, A.; Watney, L.; Willhite, G. Paul

1999-01-14

293

Fracture density as a controlling factor of postglacial fluvial incision rate, Granite Range, Alaska.  

NASA Astrophysics Data System (ADS)

The relations between lithosphere and atmosphere to shape the landscape are disputed since the last two decades. The classical "chicken or egg" problem raised the idea that erosion can promote creation of topography thanks to isostatic compensation of eroded material and subsequent positive feedback. Quaternary glaciations and high erosion rates are supposed to be the main agent of such process. More recently, "tectonic activity" has been considered not only as a rock uplift agent, but also as a rock crusher, that in turn promote erosion, thanks to the reduction of size of individual rock elements, more easily transported. The Granite Range in Alaska presents a contrasted morphology: its western part shows preserved glacial landscape, whereas its eastern part presents a strong fluvial / hillslope imprint, and only a few relicts of glacial surfaces. We quantify these differences by 1) qualitative appreciation of the landscape, 2) quantification of post-glacial erosion, and 3) hypsometric quantification of the landscape. On the field, the eastern part appears to be highly fractured, with many, large, penetrative faults, associated with km-thick fault gouges and cataclasites. The westernmost part shows massive bedrock, with minor, localised faults. Remote-sensed fracture mapping confirms this: fracture density is much higher to the east, where hypsometric parameters (HI and HIP) display anomalies, and where high post-glacial incision (up to 600m) is observed. We provide here an impressive case study for tectonic-erosion interactions through rock crushing effect, and document that half of the sediments coming out of the range come from the ~10% of the most fractured area, all other being equal. This challenges the usual view of tectonic "driving" rock uplift, while erosion removes material: In our case, tectonics is the main erosional agent, rivers and glaciers being (efficient) transport agents.

Champagnac, J.-D.; Sternai, P.; Herman, F.; Guralnik, B.; Beaud, F.

2012-04-01

294

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

NASA Astrophysics Data System (ADS)

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

Dearing, John; Hoffmann, Thomas

2010-05-01

295

Reservoir characterization of Mesaverde (Campanian) bedload fluvial meanderbelt sandstones, northwestern Colorado  

SciTech Connect

Reservoir characterization of Mesaverde meanderbelt sandstones is used to determined directional continuity of permeable zones. A 500-m (1600 ft) wide fluvial meanderbelt in the Mesaverde Group is exposed as laterally continuous 3-10-m (10-33-ft) high sandstone cliffs north of Rangely, Colorado. Forty-eight detailed measured sections through 3 point bar complexes oriented at right angles to the long axis of deposition and 1 complex oriented parallel to deposition were prepared. Sections were tied together by detailed sketches delineating and tracing major bounding surfaces such as scours and clay drapes. These complexes contain 3 to 8 multilateral sandstone packages separated by 5-20 cm (2-8 in.) interbedded siltstone and shale beds. Component facies are point bars, crevasse splays, chute bars, and floodplain/overbank deposits. Two types of lateral accretion surfaces are recognized in the point bar facies. Gently dipping lateral accretions containing fining-upward sandstone packages. Large scale trough cross-bedding at the base grades upward into ripples and plane beds. Steeply dipping lateral accretion surfaces enclose beds characterized by climbing ripple cross laminations. Bounding surfaces draped by shale lags can seal vertically stacked point bars from reservoir communication. Scoured boundaries allow communication in some stacked point bars. Crevasse splays showing climbing ripples form tongues of very fine-grained sandstone which flank point bars. Chute channels commonly cut upper point bar surfaces at their downstream end. Chute facies are upward-fining with small scale troughs and common dewatering structures. Siltstones and shales underlie the point bar complexes and completely encase the meanderbelt system. Bounding surfaces at the base of the complexes are erosional and contain large shale rip-up clasts.

Jones, J.R. Jr.

1984-04-01

296

An objective approach to marginal benefit functions for environmental flows: an example for fluvial systems  

NASA Astrophysics Data System (ADS)

Environmental flows can result from the economical competition for water allocation between traditional and non-traditional water uses. This requires the definition of convenient benefit functions (bf) associated with the use of the resource. Since the use of water by the riparian ecosystem is an intangible good, common ways based for instance on the “willingness to pay” have the dramatic weakness of not being objective with regard to the environmental rights. That is, water withdrawal from a given stream environment would depend on the importance and, in turn, on the economical value that people assign to this environment. In this work we discuss a possible objective criterion to establish benefit functions for the environmental uses of the water resource. Our approach is based on studying the optimal water allocation between the users as resulting from marginal economic analysis. That is, we show that the parameters of the marginal demand curve for the riparian ecosystem are intrinsically defined by knowing: (a) the ecological status of the riverine system in pristine conditions, and (b) the marginal benefit function of the potential competitor (e.g., exploitation activity). We solve analytically the water allocation problem for the simple case of water withdrawal from a fluvial system. We show the link between the parameters of the marginal benefit functions and the minimal environmental flow arising from classic engineering analysis, as well as their ecological meaning. This approach allows to restore a more natural variability of the streamflow regime in impounded reaches, to the cost of a profit reduction for the resource exploitation. However, on the long term, the overall idea is that the benefit for having preserved more natural environmental flow conditions since exploitation began would balance the future cost for potential restoration of the riverine corridor and the missing revenues.

Perona, P.; Burlando, P.

2009-12-01

297

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

Microsoft Academic Search

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

D. R. Kerr

1990-01-01

298

Agua Caliente Solar Feasibility and Pre-Development Study Final Report  

SciTech Connect

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.

Carolyn T. Stewart, Managing Partner; Red Mountain Energy Partners

2011-04-26

299

Lateglacial fluvial activity in an upland basin following deglaciation, River Tyne, Northumberland, UK: drivers, complications and chronology  

NASA Astrophysics Data System (ADS)

In contrast to the well-dated and documented Holocene valley floor sequences, understanding of Lateglacial fluvial activity in upland Britain is poor. In part, this is due to the fragmentary nature of the Lateglacial fluvial record and problems of establishing dating control, and part due to the complications caused by local ice histories, the effects of neotectonics (glacio-isostatic) and base level change (sea level rise). In order to fully understand and utilise the postglacial fluvial record, we need to improve our understanding of the critical Lateglacial period when the Holocene fluvial systems first started to develop as ice sheets retreated and decayed, and disentangle the the linkages between river development and glaciation, climate and sea level change. Here, we present the results of a recent study on the pre-Holocene terraces of the River Tyne, a major river system in North East England. The River Tyne drains the greater part of Northumberland, UK, with an area encompassing approximately 2, 927 km2. The Tyne is fed by two major rivers: the River South Tyne and the River North Tyne, and it ranges in elevation from headwater peaks of 893 m OD in the South Tyne to sea level. Recent investigation of the Lateglacial glacigenic environments in North East England (Yorke, 2008) has highlighted new evidence of postglacial fluvial sequences that have been preserved between the glacigenic and Holocene valley floor infills. This has provided the opportunity to better understand the Lateglacial evolution of the valley and its incised valley fills. We present evidence for Lateglacial fluvial activity along a 40 km reach of the Tyne valley corridor between Haltwhistle (South Tyne) and Blaydon (Tyne), where the most complete sequence is preserved. To identify the extent and distribution of terraces, valley floor mapping between was undertaken, based upon interpretation of NEXTMap™ Digital Surface Model (DSM) data. Sediment sequences were accessed at actively eroding cut-bank sections and supplemented with British Geological Survey (BGS) borehole data. Dating involved taking optically stimulated luminescence (OSL) samples from carefully selected lithofacies. Results show that terrace surfaces (T1-T4) lie at 8, 10, 15 and 20 m above present river level, with valley floor cut-and-fill sequences lying between 1 and 7 m above the river. The precise timing of incision of the glacigenic valley infill is unclear, but at least 30 m of incision through the infill took place before 11.5 ka, leading to the formation of the two highest terraces, T3 and T4. OSL dates for T1 and T2 indicate that they formed during the early Holocene period (11.4 - 7.9 ka). We show that the quasi-continuous incision trend in the Tyne that has preserved the upper terraces is a consequence of both isostatic rebound, change in sediment delivery and runoff related to climate instability, as well as (probably) a degree of coastal shortening in the early Holocene.

Yorke, L.; Rumsby, B. T.

2010-12-01

300

Optimización mediante algoritmos genéticos de la gestión del agua en el regadío  

Microsoft Academic Search

El uso de un recurso como el agua, esencial y escaso, tiene gran trascendencia ambiental, social, económica,\\u000apolítica, etc., siendo su adecuada gestión fundamental para conseguir la sostenibilidad de sus aprovechamientos.\\u000aPara alcanzar ese objetivo, la agricultura actual necesita modelos de ayuda a la toma de decisiones para\\u000ala gestión y explotación agrícola.\\u000aSe presenta un modelo de optimización del

Pedro Carrión; Eulogio López; José Fernando Ortega; Arturo de Juan

1970-01-01

301

Threshold-dominated fluvial styles in an arid-zone mud-aggregate river: The uplands of Fowlers Creek, Australia  

NASA Astrophysics Data System (ADS)

Fowlers Creek is a mud-aggregate fluvial system. Floodplain muds dominate the river's deposits and consist of silt, fine to very fine quartzose sand, and clay. Up to ˜ 80% of the silts and clays are bound into sand- and silt-sized aggregates and comprise a substantial component (> 42%) of the floodplain muds. Mud-aggregate sediments behave like sands during transport, and as a result, muds can be deposited under conditions of greater flow velocity than would otherwise be the case. Newly deposited floodplain muds are loose and easily entrained, but older floodplain muds are cohesive, and the distribution of modern and older floodplain muds influences erosion patterns across Fowlers Creek. In the lower order streams of the Fowlers Creek uplands, alternate reaches of shallow rectangular channels and unchannelled floodplains collectively form discontinuous ephemeral streams. These landform sequences consist of gullies, coalescing downstream to arroyos, which terminate in distributary intermediate floodouts. At Fowlers Creek, floodouts are preferentially located at tributary junctions, reflecting their origin during very large floods. At floodouts, low slope and high vegetation density promote sheetflow infiltration and landform stability. Their efficiency in retaining runoff make floodouts drought refugia; they are an important ecological element in this arid area. The higher order channel of the mid-uplands is a mobile, low-sinuosity, single-thread arroyo, incised into wide muddy unstable floodplains. Fluvial processes are dominated by episodic flood-driven channel avulsion, and variability in stream energy and boundary resistance contributes to a non-equilibrium fluvial style. Frequent reach-scale channel relocation is accompanied by the burial of the abandoned channel in floodplain muds and both erosion and aggradation in downstream floodplains.

Wakelin-King, Gresley A.; Webb, John A.

2007-03-01

302

Fluvial processes and morphological response in the Yellow and Weihe Rivers to closure and operation of Sanmenxia Dam  

NASA Astrophysics Data System (ADS)

The fluvial and morphological processes induced by impoundment of the Sanmenxia Reservoir and relevant human activities on the Yellow River and its tributaries are complex. The long-term annual sediment load of the Yellow River was 1.6 billion tons, ranking first of all the world's rivers. In 1960, Sanmenxia Dam began filling. Sediment transport in the river then was greatly disturbed and a new cycle of the fluvial processes was induced. First, the dam caused not only anticipated sedimentation in the reservoir, but also serious sedimentation in the largest tributary of the river (the Weihe River). The response of fluvial process to the dam closure varies in space and time. Second, the downstream reaches of the dam experienced erosion and resiltation, changes of river pattern, and development of meanders. Moreover, the downstream reaches of the dam have experienced more and more water diversion, which has induced readjustment of the longitudinal profile of the river. The study reveals that sedimentation in the Sanmenxia Reservoir enhanced the bed elevation at Tongguan, where the Weihe River flows into the Yellow River. The rising Tongguan's elevation caused retrogressive siltation waves in the Weihe River, which propagated at a speed of about 10 km/yr. An equilibrium sedimentation model is proposed, which agrees well with the data of sedimentation in the Weihe River. In the reaches below the dam the river changes from braided to wandering, or from wandering braided to wandering meandering. The discharge released to the downstream reaches has been regulated by the reservoir and it decreases along the course because the quantity of water diversions is more than the inflow from tributaries. The reduction in discharge causes readjustment of the longitudinal bed profile. By using the minimum stream power theory, we prove that the riverbed profile is developing toward an “S-shape” profile.

Wang, Zhao-Yin; Wu, Baosheng; Wang, Guangqian

2007-10-01

303

Integrated reservoir characterization of mature oil reservoirs: An example from Oligocene Frio fluvial/deltaic sandstones, Rincon Field, south Texas  

SciTech Connect

The Frio fluvial/deltaic sandstone along the Vicksburg fault zone play of south Texas has produced nearly 1 billion bbl of oil from fluvial/deltaic sandstones since field development began in the 1940s. More than half of the reservoirs in this depositionally complex play have been abandoned, even though large volumes of oil remain. Current efforts integrating geological and engineering reservoir characterization are being used to identify the location of unrecovered mobile oil, estimated at more than 1 billion bbl, that remains in unproduced reservoir zones in fields within this very mature play. Engineering data from Frio reservoirs in Rincon field were used to assess past production behavior, determine completion density, and prioritize zones for incremental reserve growth opportunities. Geologic data have been evaluated to identify interwell stratigraphic heterogeneity and potential for compartmentalization of significant volumes of unrecovered oil. Major oil reservoirs represent deposition in broad, dip-elongate fluvial systems. Individual zones consist of multiple thin (0-40 ft) sandstone units that stack to form gross thicknesses of 50 to 100 ft. They occur both as narrow channel fills isolated vertically and laterally by very low-permeability overbank facies and flood-plain mudstones and as large channel complexes with multiple laterally coalescing sand lobes. Large dip-elongate channel-sandstone complexes provide ideal conditions for the isolation of oil accumulations in multiple reservoir compartments, many of which are now incompletely drained or completely untapped. Reservoir architectural mapping and core analysis data from more than 100 wells are being combined with reserve volumetrics to describe heterogeneity and to identify possible locations of additional reserves within a 100-ft reservoir interval that has already produced more than 15 million bbl of oil.

McRae, L.E.; Holtz, M.H. [Univ. of Texas, Austin, TX (United States)

1994-09-01

304

Geological and seismic evidence of a new branch of the Agua Blanca Fault  

NASA Astrophysics Data System (ADS)

The Agua Blanca fault is a major, trans-peninsular, right-lateral fault located in northern Baja California. Its WNW-ESE orientation is markedly different from the general trend of the San Andreas-Gulf of California fault system. From a geological point of view, the Agua Blanca fault is considered active, but there has been little significant seismic activity directly associated with it. On October 9, 1981, the onset of an earthquake swarm was detected at the Ensenada seismic station (ENX), with a S-P time average of 2 sec. Shortly after this, an array of up to seven portable seismic stations was installed by CICESE around Todos Santos Bay. More than 180 events were recorded during the following 10 days, after which the local seismicity decreased. A second swarm consisting of 100 microearthquakes was detected between November 28 and December 5, 1981. The epicentral locations of those events recorded at four or more local stations all lie inside Todos Santos Bay. The composite fault plane solution for both swarms indicates a right-lateral strike-slip vertical fault with a strike of N52°W. Geological observations allow us to conclude that the seismic activity reported here is associated with the Agua Blanca fault zone.

González, J. Javier; Suárez, Francisco

1984-01-01

305

Clay mineral assemblages and analcime formation in a Palaeogene fluvial lacustrine sequence (Maíz Gordo Formation Palaeogen) from northwestern Argentina  

NASA Astrophysics Data System (ADS)

The Palaeogene Maíz Gordo Formation is one of the main lacustrine events recorded in northwestern Argentina. It consists of sandstone, mudstone, and limestone beds 200 m thick, deposited in a brackish alkaline lake and braided alluvial systems. The Maíz Gordo Lake evolved mainly as a closed system, with brief periods as an open one. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study samples from seven sites, corresponding respectively to proximal, intermediate, and transitional positions of the fluvial environment and marginal and inner-lake environment, focusing on the clay mineralogy and analcime formation. The basinward zonation of diagenetic minerals identified in the Maíz Gordo Lake was: mordenite ? analcime ? K-feldspar. Although not a typical zonation of saline alkaline lakes, it does indicate an increase in salinity and alkalinity towards the centre. In proximal fluvial settings, smectite predominates at the base of the sequence, with scarce kaolinite. Towards the top, a striking increase in kaolinite content suggests a change from a relatively arid climate with alternating humid and dry seasons, towards a warm and humid climate. Kaolinite content clearly decreases in a basinward direction. Such a variation is attributable to changes in hydro-geochemistry, denoting the progressive influence of the brackish and alkaline lake water on interstitial pores. SEM images of intermediate fluvial samples reveal authigenesis of illite at the expense of kaolinite booklets. In littoral and inner-lake settings the clay fraction is composed of muscovite, sometimes with subordinate smectite. Analcime occurs in variable amounts in all sedimentary facies, in rock pores or filling veins. It forms subhedral square to hexagonal, or anhedral rounded crystals, denoting that they coarsened at low to moderate degrees of supersaturation. Although the mordenite identified in a fluvial level would have been the precursor of analcime in the Maíz Gordo Basin, no textural evidence of analcime formation through replacement of mordenite or other precursor zeolite was found. Hence it is more probable that analcime formation took place by direct authigenic precipitation or through the reaction between interstitial brines and clay minerals or plagioclase.

Do Campo, M.; Del Papa, C.; Jiménez-Millán, J.; Nieto, F.

2007-09-01

306

On the control of climate- and human-modulated fluvial sediment delivery on river delta development: The Indus  

NASA Astrophysics Data System (ADS)

Deltas are particularly vulnerable coasts, affected by changes in both continental and coastal ocean processes. The currently accelerated loss of deltaic lands across the world is primarily due to fluvial sediment starvation following the pandemic construction of river dams and water diversions. However, the influence on deltas of human- or even climate-modulated changes in fluvial sediment discharge has been studied less comprehensively than other controls e.g., the sea-level rise. We examined the Indus delta to understand how the sediment source (i.e., available fluvial sediment) has affected the development of the sediment sink (i.e., the subaerial and subaqueous delta evolution). With an elevated topography and generally arid climate in the watershed, the Indus has been, in natural conditions (i.e., before dams reduced its flow and sediment discharge by over 80%), one of the most important sediment-producing rivers in the world. Bathymetric data show that the Indus shelf morphology exhibits a compound clinoform morphology. Whereas the inner shoreface-connected clinoform has clearly developed as the subaqueous part of the modern Indus delta, the offshore clinoform is either a relict or a contemporaneous prodelta clinoform. Following the reduction in sediment discharge after the late 1950's, the deltaic shoreline in the central part of the delta coast started to recede providing sediment for the southeastern and northwestern coast sectors that remained largely progradational. This differential behavior of the delta shoreline indicates that even a drastic loss of fluvial sediment is initially buffered by an erosional smoothing of the delta coast. New data from onland drilling shows that unlike most Holocene deltas, the Indus delta prograded through the later part of the deglacial sea level rise, starting no later than 12,000 cal. years BP. Neodymium isotope data indicate that sediments comprising the entire Holocene delta originated predominantly in the monsoon-affected Himalayas. This early inception of the Indus delta was probably controlled by an augmented sediment delivery from the Indus basin occurring between 13000 and 9500 years BP during a period of abrupt increase in the intensity of the summer monsoon. Subsequently, a centuries-long phase of reduced precipitations in the Indus basin resulted in an abrupt decrease of the Indus discharge sometimes between 9000 and 8000 years. During this phase, almost the entire early Indus delta was flooded as marine waters penetrated deep inland, providing a grim analog for the future of currently sediment starved river deltas. Furthermore, it will be discussed that this complex evolution of the Indus delta points toward a fundamental change in paradigm for the dynamics deltas at centennial to millennial time scales and for interpreting the sedimentary architecture of transgressive and highstand deltaic deposits.

Giosan, L.; Clift, P. D.; Blusztajn, J.; Tabrez, A.; Constantinescu, S.; Filip, F.

2006-12-01

307

Decades of change: contributions of geomorphology to fluvial and coastal engineering and management  

NASA Astrophysics Data System (ADS)

Major developments in the contribution of geomorphology to engineering and environmental management have taken place over the past ten years in the United Kingdom, particularly in the coastal and fluvial spheres. Considerable achievements have been gained in raising awareness of the nature of geomorphic processes and their dynamics, and of how the understanding of geomorphology can aid effective management and decisions on engineering strategies. Specifically, this has meant gaining an understanding of interconnectedness in geomorphic systems and the long-term variability of processes and landforms. Radical changes in both policies and decision-making frameworks have taken place such that the approach to coastal and river management adopted by the British Government is now to 'work with nature'. Likewise, management structures have been implemented to facilitate and encourage integrated planning. Such changes have not, of course, occurred from the influence of geomorphologists alone, but they do align policy much more with geomorphological principles than in the past. Examples are presented of geomorphological involvement in coastal engineering in Britain. Engineering geomorphology is now in a second phase of answering geomorphological questions, providing geomorphological information, and implementing management in accordance with the principles advocated. This is involving much case-study work at specific locations. A third phase of major development in the future is envisaged in this paper, mainly stemming from major changes in geomorphology itself and underlain by radical alterations of scientific theories, philosophy, and methods. This will involve modelling and predicting responses in ways that adequately deal with complexity, positive feedback, non-linearity, and holism. Questions remain, with regard to the links between geomorphology and engineering, about the type of predictions that are possible and acceptable, and about the extent to which geomorphology will provide solutions, both nationally and internationally. Whatever strategies or solutions are suggested, there remains the issue of political acceptability in specific applications and the need for mechanisms to make public gain compatible with private loss. Geomorphologists arguably have the potential for another major leap forward, stimulated by theoretical and technological developments, in which the results of research will feed directly into environmental engineering, provided that the requisite spatial and temporal data are available.

Hooke, J. M.

1999-12-01

308

Experimental investigation of fluvial incision on Titan by low-velocity sediment impacts  

NASA Astrophysics Data System (ADS)

Images returned by the Cassini-Huygens mission reveal evidence for widespread fluvial incision in the polar regions of Titan. Dendritic channel networks draining to large lakes and the absence of cratering suggest active incision into Titan's water-ice bedrock surface. Previous work using the saltation-abrasion bedrock incision model suggests that a terrestrial channel transposed to Titan conditions would incise at remarkably similar rates, because the effects of Titan's lower gravity and less-dense sediments are offset by a much lower resistance to abrasion for ice than rock of similar strength. Here we report new laboratory measurements of ice erosion by low-velocity sediment impacts, part of a larger study investigating the temperature dependence of the material properties that control ice erodibility. We measure the energy required to erode a unit volume of ice using drop tests, in which a 110-150 g ice clast falls 5-10 cm onto a 20 cm diameter ice disk, and differences in mass and measurements of ice density are used to calculate the volume eroded. We construct the 10cm thick ice disks using 2-4 mm seed crystals and near-freezing distilled water. After freezing at 253 K a disk is placed in the bottom of a steel cylinder surrounded by dry ice and liquid nitrogen is pumped into the cylinder from below, chilling the ice to near-Titan temperatures for several hours but never submerging the samples (all drop test trials are completed in air). Our preliminary drop test results show that 4 J and 25 J are required to erode 1 cm3 of ice at temperatures of 205 K and110 K respectively, suggesting that ice may be no more than 2-3 times more erodible than previously-tested rocks of similar tensile strengths. A key limitation of this experimental method is the small size of our target disks, which fail catastrophically by through-cracking after several hundred drops. To avoid through-cracking and obtain direct measurements of ice surface erosion, we are preparing new experiments using a large ice block (~1.25x105 cm3) enclosed in an insulated test chamber, and a laser topographic scanning system. The drop-test results will then be used to design ice-flume experiments in a walk-in freezer to investigate controls on rates of ice incision by mobile sediments and the morphodynamics of incising ice channels.

Polito, P. J.; Zygielbaum, B. R.; Sklar, L. S.; Collins, G.

2008-12-01

309

Fluvial processes along a tectonically active coast, eastern Coastal Range, Taiwan  

NASA Astrophysics Data System (ADS)

The eastern Coastal Range of Taiwan is part of the accreted north Luzon arc, which belongs to the Philippine Sea plate that is colliding with the Eurasian plate margin. Many authors have described the intensive collision and the rigorous neotectonic activity of eastern Taiwan. In the working area along the eastern coast of Taiwan, this affects river morphology. This is expressed in knick points, a location at which stream gradient is locally large and intensive erosion occurs. A knick point has been regarded as an important geomorphic feature in river morphology. The distribution of knick points can provide evidences about active faults. In the study area there is no other climatic or lithological control that could result in different steepness along river profiles. This study will examine the distribution of fluvial knick points along the main rivers in the Coastal Range in Taiwan (mainly in between the cities of Changping and Chengkung). Based on a digital elevation model (ASTER DEM), hydrological analyses, such as flow accumulation, flow directions and watershed analyses were made. On this fundamental information a stream grid was calculated, limited to rivers with a threshold of 2000 cells to exclude smaller streams. For further analysis only rivers of the Strahler order 1 were used to exclude knick points resulting from changes in the additional amount of water. After the classification, the knick points of every single stream were studied, including the calculations of the stream gradient and the stream length index. Nearly every river shows the similar knick points independent from the river length but on different heights or positions. Furthermore, all major river catchments show a similar asymmetry of catchments in hill slope analysis, and such asymmetry is difficult to explain solely by lithological controls. The stream gradient of the rivers was calculated by using a wiggling window along every stream profile to calculate the slope. To compare the different rivers, we evaluated the results using an approach of statistics that contains the height, length, gradients and knick point frequency of the rivers. The results will be compared by field observations.

Pflanz, D.; Shyu, B. H.

2012-04-01

310

Fluvial dissolved inorganic C dynamics in the Western Amazonian basin: where does this carbon come from?  

NASA Astrophysics Data System (ADS)

The Amazon river and tributaries constitute globally a significant freshwater body and thus a source of atmospheric carbon dioxide. Aquatic carbon dioxide may originate from biological or physicochemical reprocessing of allochthonous dissolved, particulate or inorganic C (ecosystem-derived C, EDC) or it may derive from groundwater inputs of dissolved inorganic C through lithological weathering by soil-derived organic acids or by the dissolution of atmospheric carbon dioxide (minerogenic-derived C, MDC). In addition to quantifying and scaling catchment source import and export terms, accurate budgeting requires additional source differentiation. The significance of MDC is not usually considered by those assessing carbon dioxide efflux, yet differentiating MDC from EDC is crucial. For example, MDC should be less directly affected than EDC by future climatic change, becoming proportionally more important to fluvial carbon dioxide efflux in drought episodes. We are measuring the stable carbon isotopic ratio of dissolved inorganic C to determine the relative importance of MDC and EDC to total C loads in the Tambopata basin in Western Peru. This is an area little studied for C cycling, but important as the soils here are more nutrient rich than the remainder of the Amazon basin which is more studied. Our field station is in the Tambopata national park and since 2010 we have sampled four different river systems which vary in size and drainage characteristics: the Tambopata, (CA ~14,000 km sq.; ~30% of its in the Andes Mountains); La Torre (~2000 km sq.), New Colpita and Main Trail (both < 2 km sq. forest drainage but Main Trail only active in the wet season). Additionally the pH, conductivity, dissolved oxygen, water temperature and stage height have been monitored in these drainage systems where possible by logging at 15 minute intervals. Our data shows that there are statistically significant differences in carbon isotopic composition (ranging from -14 to -29 ‰) and [DIC] concentration (ranging from 0.1 to 0.7 mM) between rivers, which we interpret to represent differences in the MDC / EDC input. We will present this data and discuss in more detail local, seasonal and regional controls on composition, and its application in source contribution apportionment. Whilst we are utilising this DIC isotope tracer to differentiate the source of DIC (and ultimately effluxed carbon dioxide) this study shows the potential of utilising the DIC-C isotopic composition as a tracer of groundwater-surface water interaction.

Waldron, S.; Vihermaa, L. E.; Newton, J.; Krusche, A.; Salimon, C.

2012-04-01

311

Implications of bank failures and fluvial erosion for gully development: Field observations and modeling  

NASA Astrophysics Data System (ADS)

Gully erosion is most commonly triggered by fluvial erosion following natural and anthropogenic disturbances or as a response to changes in climate and tectonic forcing and base level drop. Field observations attribute the headward growth and widening of many gully systems to gravitational mass-wasting processes of oversteepened sidewalls. Soil saturation, groundwater sapping, and tension crack development 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 we first present an explicit physically based theory for the stability analysis of gully heads and walls. The theory is based on the force balance equation of an assumed planar failure geometry of a steep gully wall, with a potential failure plane dipping into the incised gully bed and tension cracks developing behind the scarp face. Then, we test the theory against field data collected in our field site in Colorado and against other published data. Second, the theory is implemented in a one-dimensional hillslope profile development model and the three-dimensional channel-hillslope integrated landscape development (CHILD) to study the effects of soil cohesion, erosion thresholds, and stochastic climate on the tempo of gully development and morphology. Preliminary results indicate that wider and shallower gullies develop and integrate, forming wide valleys, when soil cohesion is small. As soil cohesion increases, erosion slows down, gullies become deeper with vertical walls, and episodic mass failures occur. Differences in storm intensity-duration characteristics and erosion thresholds are predicted to have a significant impact on gully development. Vertical gully walls develop rapidly, and gullies enlarge by slab failures in a climate characterized by high-intensity, short-duration storm pulses. However, under low-intensity, long-duration storms, gullies quickly stabilize, and vertical walls are eliminated and rounded, forming diffusion-dominated hilltops. Erosion thresholds have a similar impact on the tempo of gully erosion but in the opposite direction. Lowering the erosion threshold enhances gully widening by slab failures. Gully walls stabilize when the erosion threshold is high due to a reduction in the erosion of the failure material on the toe of gully walls.

Istanbulluoglu, Erkan; Bras, Rafael L.; Flores-Cervantes, Homero; Tucker, Gregory E.

2005-03-01

312

Continental-scale models of water balance and fluvial transport: An application to South America  

NASA Astrophysics Data System (ADS)

A coupled water balance and water transport model (WBM / WTM) was constructed as part of a larger study of global biogeochemistry. The WBM / WTM provides critical hydrologic information to models of terrestrial primary production, organic matter decay, riverine nutrient flux and trace gas exchanges with the troposphere. Specifically, it creates high-resolution data sets for monthly soil moisture, evapotranspiration, runoff, river discharge and floodplain inundation. As a first step toward eventual global coverage, the WBM / WTM was applied to South America, represented by more than 5700 1/2° (latitude / longitude) grid cells. The WBM transforms spatially complex data on long-term climate, vegetation, soils and topography into predictions of soil moisture (SM), evapotranspiration (ET) and runoff (RO). For South America, field capacity in soils ranged from 27 to 582 mm of water, and computed values for mean annual SM, ET and RO were 284 mm, 1059 mm/yr and 619 mm/yr, respectively. There were large differences regionally and over the year. The transport model uses WBM-derived runoff, information on fluvial topology, linear transfer through river channels and a simple representation of floodplain inundation to generate monthly discharge estimates for any cell within a simulated catchment. The WTM successfully determined the timing and magnitude of discharge at selected locations within the Amazon / Tocantins basin. It also demonstrated the importance of floodplain inundation in defining flow regime on the mainstem Amazon. Estimated mean annual discharge was 207,000 m3/s for the Amazon River and 17,000 m3/s for the Tocantins. In these basins, 45% of the incident precipitation emerges as river flow; 55% is lost to ET. The model described in this paper will be expanded to include the dynamics of carbon, major nutrients and sediments. It will serve as a semimechanistic tool to quantify the transport of materials from the landscape to the world's oceans. Such a capability becomes increasingly important as we seek to understand the impacts of climate and land use change on major river systems of the globe.

VöRöSmarty, Charles J.; Moore, Berrien; Grace, Annette L.; Gildea, M. Patricia; Melillo, Jerry M.; Peterson, Bruce J.; Rastetter, Edward B.; Steudler, Paul A.

1989-09-01

313

Modeling the Long-Term Fluvial Redistribution of Tephra in Fortymile Wash, Yucca Mountain, Nevada  

NASA Astrophysics Data System (ADS)

In the unlikely event of a volcanic eruption in the potential repository at Yucca Mountain, Nevada, radioactive waste may be transported in the volcanic plume. Contaminated basaltic tephra could be deposited on hillslopes around Yucca Mountain, which are part of the Fortymile Wash catchment basin, as an ephemeral stream system that is the primary drainage for Yucca Mountain. Potential deposition of radionuclides at or near a receptor (reasonably maximally exposed individual) location could occur either from direct sedimentation from the plume or from the remobilization of tephra by water and wind after initial deposition. Erosion and sediment transport rates in this arid region are difficult to measure directly. As an alternative, we have used a sediment budget approach to model the long-term fluvial redistribution of basaltic tephra at Yucca Mountain. Our model input addresses uncertainties in data and site-specific processes to demonstrate the quantitative (or mass flux) relationship between sediment budget components. These components include sediment yield, dilution by mixing with ambient sediment, balance of remaining tephra, associated changes in sediment storage, and discharge to the depositional basin as a function of time after the eruption. Using mean values for sediment yield and mass of erupted tephra, the model estimates that approximately 98 percent of the tephra deposit remains in the Fortymile Wash catchment basin 100 years after an eruption. An average of 4,100 years of erosion is estimated to deplete the deposit from the catchment basin. Using these same values, the ratio of eroded tephra to total sediment transported into the depositional basin is estimated to range between 0.4 and 0.5. These results suggest that potential basaltic tephra deposits within the Fortymile Wash drainage system may not be rapidly diluted within a few hundred years of deposition and that their erosion may not be explained by a simple decay relationship. The posteruption redistribution of tephra may, therefore, be an important consideration in the performance assessment of a potential Yucca Mountain repository. This abstract was prepared to document work performed by the Center for Nuclear Waste Regulatory Analyses (CNWRA) and it contractors for the U.S. Nuclear Regulatory Commission (NRC) under Contract No. NRC-02-02-012. The activities reported here were performed on behalf of the NRC Office of Nuclear Material Safety and Safeguards, Division of High Level Waste Repository Safety. This paper is an independent product of the CNWRA and does not necessarily reflect the view or regulatory position of the NRC.

Hooper, D. M.

2005-12-01

314

Physical and human influences on fluvial water quality in the Tagus river catchment, Portugal  

NASA Astrophysics Data System (ADS)

Rivers are important resources of drinkable water, ecosystems with a high biologic potency and places of entertainment. Water quality at the catchment scale depends on climate, geology, geomorphology, soils and mainly of land use and land cover. Different activities such as agriculture, livestock, industrial and urban drains have promoted the deterioration of the fluvial water quality. The announced climate changes, the increase of food requirements, as well as the urban concentration of people pose new challenges for the assessment and sustainable management of water quality on the catchment scale. At present about 2/3 of portuguese population live near coast, in urban centers. Since the last three decades, the largest part of the marginal agricultural land has been abandoned whilst the most productive soils have experienced an intensification on its productivity. The Tagus river catchment, with an area of 24.850 km2 only in the Portuguese territory, shows very important contrasts in climate, geology, geomorphology, land use and population density. The main objectives of this work are to evaluate and compare the surface water quality in different sub catchments of Tagus river and to contribute to a better understanding of how physical and human factors (such as geology, precipitation, temperature, runoff, land use and land cover and population density) interfere in their spatial-temporal variability. In order to achieve this issue, twenty sub catchments were selected. The chosen catchments show different locations and areas, and a quite long data series of physical, chemical and biology properties of water, such as nitrates, phosphates, dissolved oxygen, total coliforms, etc. Making use of Geographic Information System (GIS) tools, a database was created for each sub-catchment containing all the physical and human characteristics. Afterwards, statistical analysis was carried out by using SPSS programme (11.0 for Windows. One-way analysis of variance and the Tukey multiple comparison procedure was performed in order to assess whether differences in physical and human factors and water properties existed among the selected sub catchments. Other statistical procedures were carried out to determine correlations and dependencies between available data. Obtained results show significant statistical differences (p<0,001) among sub catchments concerning surface water quality. Results allow us to conclude that such water is in good quality, contrary to other water which contains a very high nitrates, phosphates and total coliform levels. The factors which better explain this variability are related to the land use, chiefly when social use is preponderate.

Nunes, A.

2009-04-01

315

Late Weichselian fluvial evolution on the southern Kara Sea Shelf, North Siberia  

NASA Astrophysics Data System (ADS)

Glaciations had a profound impact on the global sea-level and particularly on the Arctic environments. One of the key questions related to this topic is, how did the discharge of the Siberian Ob and Yenisei rivers interact with a proximal ice sheet? In order to answer this question high-resolution (1-12 kHz), shallow-penetration seismic profiles were collected on the passive continental margin of the Kara Sea Shelf to study the paleo-drainage pattern of the Ob and Yenisei rivers. Both rivers incised into the recent shelf, leaving filled and unfilled river channels and river canyons/valleys connecting to a complex paleo-drainage network. These channels have been subaerially formed during a regressive phase of the global sea-level during the Last Glacial Maximum. Beyond recent shelf depths of 120 m particle transport is manifested in submarine channel-levee complexes acting as conveyor for fluvial-derived fines. In the NE area, uniform draping sediments are observed. Major morphology determining factors are (1) sea-level fluctuations and (2) LGM ice sheet influence. Most individual channels show geometries typical for meandering rivers and appear to be an order of magnitude larger than recent channel profiles of gauge stations on land. The Yenisei paleo-channels have larger dimensions than the Ob examples and could be originated by additional water release during the melt of LGM Putoran ice masses. Asymmetrical submarine channel-levee complexes with channel depths of 60 m and more developed, in some places bordered by glacially dominated morphology, implying deflection by the LGM ice masses. A total of more than 12,000 km of acoustic profiles reveal no evidence for an ice-dammed lake of greater areal extent postulated by several workers. Furthermore, the existence of the channel-levee complexes is indicative of unhindered sediment flow to the north. Channels situated on the shelf above 120-m water depth exhibit no phases of ponding and or infill during sea-level lowstand. These findings denote the non-existence of an ice sheet on large areas of the Kara Sea shelf.

Dittmers, K.; Niessen, F.; Stein, R.

2008-02-01

316

Mineralogical and chemical variability of fluvial sediments 2. Suspended-load silt (Ganga-Brahmaputra, Bangladesh)  

NASA Astrophysics Data System (ADS)

Sediments carried in suspension represent a fundamental part of fluvial transport. Nonetheless, largely because of technical problems, they have been hitherto widely neglected in provenance studies. In order to determine with maximum possible precision the mineralogy of suspended load collected in vertical profiles from water surface to channel bottom of Rivers Ganga and Brahmaputra, we combined Raman spectroscopy with traditional heavy-mineral and X-ray diffraction analyses, carried out separately on low-density and dense fractions of all significant size classes in each sample (multiple-window approach). Suspended load resulted to be a ternary mixture of dominant silt enriched in phyllosilicates, subordinate clay largely derived from weathered floodplains, and sand mainly produced by physical erosion and mechanical grinding during transport in Himalayan streams. Sediment concentration and grain size increase steadily with water depth. Whereas absolute concentration of clay associated with Fe-oxyhydroxides and organic matter is almost depth-invariant, regular mineralogical and consequently chemical changes from shallow to deep load result from marked increase of faster-settling, coarser, denser, or more spherical grains toward the bed. Such steady intersample compositional variability can be modeled as a mixture of clay, silt and sand modes with distinct mineralogical and chemical composition. With classical formulas describing sediment transport by turbulent diffusion, absolute and relative concentrations can be predicted at any depth for each textural mode and each detrital component. Based on assumptions on average chemistry of detrital minerals and empirical formulas to calculate their settling velocities, the suspension-sorting model successfully reproduces mineralogy and chemistry of suspended load at different depths. Principal outputs include assessment of contributions by each detrital mineral to the chemical budget, and calibration of dense minerals too rare to be precisely estimated by optical or Raman analysis but crucial in both detrital-geochronology and settling-equivalence studies. Hydrodynamic conditions during monsoonal discharge could also be evaluated. Understanding compositional variability of suspended load is a fundamental pre-requisite to correctly interpret mineralogical and geochemical data in provenance analysis of modern and ancient sedimentary deposits, to accurately assess weathering processes, sediment fluxes and erosion patterns, and to unambiguously evaluate the effects of anthropogenic modifications on the natural environment.

Garzanti, Eduardo; Andó, Sergio; France-Lanord, Christian; Censi, Paolo; Vignola, Pietro; Galy, Valier; Lupker, Maarten

2011-02-01

317

Paleochannel and paleohydrology of a Middle Siwalik (Pliocene) fluvial system, northern India  

NASA Astrophysics Data System (ADS)

Late Cenozoic fresh water molasses sediments (+6000 m thick) deposited all along the length of the Himalayan fore deep, form the Siwalik Supergroup. This paper reports the results of the paleodrainage and paleohydrology of the Middle Siwalik sub-group of rocks, deposited in non-marine basins adjacent to a rising mountain chain during Pliocene. Well-exposed sections of these rocks have provided adequate paleodrainage data for the reconstruction of paleochannel morphology and paleohydrological attributes of the Pliocene fluvial system. Cross-bedding data has been used as inputs to estimate bank full channel depth and channel sinuosity of Pliocene rivers. Various empirical relationships of modern rivers were used to estimate other paleohydrological attributes such as channel width, sediment load parameter, annual discharge, and channel slope and flow velocity. Computed channel depth, channel slope and flow velocity are supported independently by recorded data of scour depth, cross-bedding variability and Chezy's equation. The estimates indicate that the Middle Siwalik sequence corresponds to a system of rivers, whose individual channels were about 400 m wide and 5.2-7.3 m deep; the river on an average had a low sinuous channel and flowed over a depositional surface sloping at the rate of 53 cm/km. The 700-km-long Middle Siwalik (Pliocene) river drained an area of 42925 km2 to the north-northeast, with a flow velocity of 164-284 cm/s, as it flowed generally south-southwest of the Himalayan Orogen. Bed-load was about 15% of the total load of this river, whose annual discharge was about 346-1170 m3/s normally and rose to approximately 1854 m3/s during periodic floods. The Froude number of 0.22 suggests that the water flows in the Pliocene river channels were tranquil, which in turn account for the profuse development of cross-bedded units in the sandstone. The estimated paleochannel parameters, bedding characteristics and the abundance of coarse clastics in the lithic fill are rather similar to the modern braided rivers of Canada and India such as South Sackatchewan and Gomti, respectively.

Khan, Z. A.; Tewari, R. C.

2011-06-01

318

POST WATERFLOOD CO2 MISCIBLE FLOOD IN LIGHT OIL FLUVIAL DOMINATED DELTAIC RESERVOIR  

SciTech Connect

Texaco Exploration and Production Inc. (TEPI) and the US Department of Energy (DOE) entered into a cost sharing cooperative agreement to conduct an Enhanced Oil Recovery demonstration project at Port Neches. The field is located in Orange County near Beaumont, Texas, and shown in Appendix A. The project would demonstrate the effectiveness of the CO{sub 2} miscible process in Fluvial Dominated Deltaic reservoirs. It would also evaluate the use of horizontal CO{sub 2} injection wells to improve the overall sweep efficiency and determine the recovery efficiency of CO{sub 2} floods in waterflooded and partial waterdrive reservoirs. Texaco's objective on this project was (1) to utilize all available technologies, and to develop new ones, and (2) to design a CO{sub 2} flood process which is cost effective and can be applied to many other reservoirs throughout the US. A database of potential reservoirs for the gulf coast region was developed by LSU, using a screening model developed by Texaco Research Center in Houston. A PC-based CO{sub 2} screening model was developed and the aforementioned database generated to show the utility of this technology throughout the US. Finally, the results and the information gained from this project was disseminated throughout the oil industry via a series of SPE papers and industry open forums. Reservoir characterization efforts for the Marginulina sand shown in Appendix C, were accomplished utilizing conventional and advanced technologies including 3-D seismic. Sidewall and conventional cores were cut and analyzed, lab tests were conducted on reservoir fluids and reservoir voidage was monitored as shown in Appendices B through M. Texaco has utilized the above data to develop a Stratamodel to best describe and characterize the reservoir and to use it as input for the compositional simulator. The compositional model was revised several times to integrate the new data from the 3-D seismic and field performance under CO{sub 2} injection, to ultimately develop an accurate economic model. The Port Neches CO{sub 2} Project concentrated upon the tertiary oil recoveries, to be obtained from two sections of the reservoir, which were at different stages of depletion. The large waterflooded fault block had an average remaining oil saturation of 31% while the small partial waterdrive fault block had an oil saturation of 43%.

Tim Tipton

2004-04-06

319

Evidence for an early land use in the Rhône delta (Mediterranean France) as recorded by late Holocene fluvial paleoenvironments (1640-100 BC)  

NASA Astrophysics Data System (ADS)

The overall objective of this paper is to describe the late Holocene (1640-100 BC) sedimentary and biological evolution of the Rhône-delta-plain, to interpret the sedimentary facies and palynofacies as the result of the effects of fluvial dynamic fluctuations and relative sea level change and to evaluate the paleohydrological constraints in the development of the land use and settlements of the Camargue. Focus is made on the upper part of V III core drilled on NE of the Vaccarès lagoon. By combining sedimentology, palynology, magnetic susceptibility and archeological data, this study allowed to identify the superposition of three types of paleo-environments (marsh, fluvial floodplain, levee/crevasse splay). This sequence indicates a gradual extension of fluvial environments between the end of the second millennium BC and the 1st century BC. The variability of fluvial dynamic is evident during this period with important flood events which contrast with periods of low flow. Pollen record can be a good marker of the fluvial dynamic variability. The expression of the riparian tree pollen grains in the coarser floodplain deposits could correspond to increased fluvial influence and probably to erosion of riverbank during flood events. The local plants are associated to the low energy sedimentary environments. Focuses are made on the relations between the evolution of the environment and land use. The development of the cereal culture in the floodplain of the Rhône delta has been demonstrated between 1640-1410 and 100 BC. The last alluviation of the Rhône perturbs the research of the archaeological sites in the central part of the delta but the existence of the rural villages from the first part of the first millennium BC is highly possible.

Arnaud-Fassetta, Gilles; De Beaulieu, Jacques-Louis; Suc, Jean-Pierre; Provansal, Mireille; Williamson, David; Leveau, Philippe; Aloïsi, Jean-Claude; Gadel, François; Giresse, Pierre; Oberlin, Christine; Duzer, Danièle

320

Morphologic and stratigraphic investigations in Eastern Libya Montes, Mars: Implications for long-term fluvial activity  

NASA Astrophysics Data System (ADS)

Introduction: The Noachian highland Libya Montes, located at the southern edge of Isidis Planitia, represents one of the oldest regions [1] that have been most heavily modified by fluvial processes. In this ancient region, long and broad "longitudinal valleys" are pervasive. They are indication for intensive, longterm and multiple fluvial processes [2-4]. In addition, widespread "dendritic valley networks", particularly their extended branching, are evidence for atmospheric precipitation [5]. Within the Libya Montes, three distinct valley systems are defined by [2]: a western, a middle and an eastern system. Here, we present our morphologic and stratigraphic investigations of the eastern valley system located between 75°E and 90°E and 5°N and 5°S (Figure 1). Here we focus on investigating morphologic features in order to produce a morphologic map. A morphologic map was constructed on the basis of visual mapping. In a second step, we performed crater counts for our geomorphologic units in order to determine their stratigraphy. Data: Several datasets from current missions, including the High Resolution Stereo Camera (HRSC), the Context Camera (CTX), the High Resolution Imaging Science Experiment (HiRISE), the Mars Orbiter Camera (MOC), the Mars Orbiter Laser Altimeter (MOLA) and the Thermal Emission Imaging System (THEMIS) were used to create our map. These images were also used for the regional and local analysis of morphologic features and their stratigraphic relationships. Morphology: Our morphologic mapping builds on the classification of [2], but has been altered based on newer, higher resolution data. Therefore, existing units were modified and a couple of new units were added. Our detailed morphologic map is shown in Figure 2. The Noachian highlands (Nm) are the oldest surfaces in the study area and are shown in dark-brown in the morphologic map (Figure 2). Adjacent to the basement material, unit NHf displays steep and heavily degraded slopes. Widespread within the NHf are small "dendritic valley networks" (Figure 3) which are shown in dark green and labeled with NHf_d. The "longitudinal valleys" are long stretched and broad in geometry (Figure 3). They are shown as unit NHf_l. Downstream and within their middle reaches, the "longitudinal valleys" become incorporated into broad plains. The "longitudinal valleys" are interrupted several times by "intermontane plains" Hi_ip (light blue) and "highland basins" Hi_hb (dark blue). Stratigraphy: In total, we performed 141 crater counts on 62 homogeneous surface units. Our model ages [6-7] determined by crater counts vary between ~4.1 and ~3.3 Ga. This corresponds to the period from the middle Noachian to the upper Hesperian [6]. The oldest model ages were measured in the "Noachian massifs" (Nm) within the range from ~4.1 to ~3.8 Ga. These remnants of the ancient highlands show an average age of ~4.0 Ga. The "dendritic valley networks" show the same average age of ~4.0 Ga, which corresponds to a formation within the middle Noachian. Our crater counts reveal that the formation of the dendritic drainage patterns occurred within ~300 My, between ~4.1 and ~3.8 Ga. The sloped surfaces next to the "longitudinal valleys" exhibit model ages of approximately ~3.8 to ~3.5 Ga. The main valley of eastern Libya Montes shows a model age of ~3.5 Ga (Figure 4). Hence, the surfaces are upper Noachian and lower to upper Hesperian in age. The average age of approximately ~3.7 Ga corresponds to the Noachian-Hesperian transition. The difference in age between the older middle regions of the "longitudinal valleys" and their younger downstream regions, amounts to nearly ~200 My. Our results are consistent with the ages of the western valley system, which has been dated to be ~3.7 - ~3.3 Ga old [4] The age determinations for units Hi_ip and Hi_hb showed a formation period of about ~500 My within the range from ~3.8 to ~3.3 Ga. The average age amounts to ~3.6 Ga. We find that

Erkeling, G.; Reiss, D.; Hiesinger, H.; Jaumann, R.

2008-09-01

321

Sequence stratigraphic-structural analysis of the East Midlands Carboniferous oil field, UK: Implications for fluvial reservoir models  

SciTech Connect

The integration of seismic, well log and core data from, the Scampton North and Welton oil fields, Lincolnshire, UK, has enabled the development of a sequence stratigraphic-structural model for late Namurian and early Westphalian fluvial reservoirs. The tectonic and sequence stratigraphic setting is remarkably similar to that in the Southern North Sea which extends more than 250 km to the east. Closer onshore well spacing, supplemented with coal exploration borehole data, provides an excellent analogue for new Carboniferous Southern North Sea developments and prospects. The reservoirs comprise medium-grained, low sinuosity fluvial aggradational packages within a coal-bearing, fluvio-deltaic depositional environment. Although major active faults occur within the Namurian, tectonic activity had ceased by the start of the Westphalian which has a tramline-like appearance on seismic. The reservoirs are poorly interconnected as a consequence of small-scale faults and extensive shale baffles, which have resulted in considerable production problems, accentuated by an initial poor reservoir correlation. Palynology has proven to be highly imprecise, consequently, the use of seismic picks as chronostratigraphic markers combined with the coal stratigraphy from British Coal boreholes and the application of sequence stratigraphic, concepts has enabled a more precise reservoir correlation to be made.

Aitken, J.F.; Quirk, D.G. (Oxford Brookes Univ., Oxford (United Kingdom))

1996-01-01

322

Paleo-fluvial sedimentation on the outer shelf of the East China Sea during the last glacial maximum  

NASA Astrophysics Data System (ADS)

Evidence from lithology, foraminiferal assemblages, and high-resolution X-ray fluorescence scanning data of core SFK-1 indicates tidally influenced paleo-fluvial sedimentation during the last glacial maximum (LGM) on the outer shelf of the East China Sea. The paleo-fluvial deposits consist of river channel facies and estuarine incised-valley-filling facies. Different reflections on the seismic profile across core SFK-1 suggest that the river channels shifted and overlapped. River channel deposition formed early in the LGM when sea level fell and the estuary extended to the outer shelf. Channel sediments are yellowish-brown in color and rich in foraminifera and shell fragments owing to the strong tidal influence. Following the LGM, the paleo-river mouth retreated and regressive deposition of estuarine and incised-valley-filling facies with an erosion base occurred. The river channel facies and estuarine incised-valley-filling facies have clearly different sedimentary characteristics and provenances. The depositional environment of the paleoriver system on the wide shelf was reconstructed from the foraminiferal assemblages, CaCO3 content and Ca/Ti ratio. The main results of this study provide further substantial constraints on the recognition of late Quaternary stratigraphy and land-sea interactions on the ECS shelf.

Wang, Zhongbo; Yang, Shouye; Zhang, Zhixun; Lan, Xianhong; Gu, Zhaofeng; Zhang, Xunhua

2013-07-01

323

Accommodation-based controls on fluvial-deltaic reservoir compartmentalization: Examples from the Oligocene Frio Formation, south Texas  

SciTech Connect

Accurate prediction of compartment architecture and intracompartment heterogeneity is necessary to locate and recover the estimated 15 billion barrels of mobile oil remaining in U.S. fluvial-dominated deltaic reservoirs. To improve this prediction, facies-specific relationships between accommodation trends and sand-body architecture that were established by outcrop studies in the western interior were Successfully applied in a study of Oligocene Frio Formation reservoirs along the Vicksburg Fault Zone of South Texas. Compartment architecture and internal heterogeneity were determined for mature upper and lower delta-plain reservoirs within two 4th-order genetic units to document reserve growth potential. In lower delta-plain settings, low-accommodation conditions at the base of genetic units produce narrow distributary channels that feed many small mouth bars, whereas high-accommodation conditions near the top of genetic units yield broader distributaries arid an expansive wave-dominated delta front. In proximal upper delta-plain settings, low accommodation produces few narrow fluvial channels that are commonly internally trough cross-strata predominate, with the finer grained silty upper point-bar deposits being removed by successive scour events during which base level has not risen substantially. In contrast, high accommodation yields many broad internally heterogeneous channels in which high and erosion of fine-grained channel-top facies. This study documents the profound effect that accommodation conditions can have suiting production behavior. Similar studies in other settings are needed to identify these relationships for the entire spectrum of depositional systems.

Knox, P.R. (Univ. of Texas, Austin, TX (United States))

1996-01-01

324

Research Opportunities for Studies of Contaminant Transport in Fluvial Systems at the TIMS Branch - Steed Pond System, Savannah River Site  

SciTech Connect

A workshop to identify the scientific issues associated with contamination in riparian, fluvial, and hyporheic systems was held in March 2003 at the Savannah River Site (SRS). The workshop examined the general scientific remediation challenges and research opportunities in such systems and on Tims Branch - Steed Pond, a specific uranium- and heavy-metal-contaminated riparian system at SRS. A diverse group of scientists representing a wide range of scientific disciplines came from academia, national laboratories, and research centers to develop recommendations for future ERSD research opportunities. There was agreement among the workshop participants that riparian, fluvial, and hyporheic systems represent a unique opportunity to advance science and to enable progress on DOE's environmental cleanup of contaminated sites. The participants at this workshop documented both the critical need and the great promise for research on hydrological and biogeochemical processes controlling contaminant transport and fate in contaminated surface and near-surface systems. The approach of the workshop was to assess the Tims Branch - Steed Pond system at the SRS as an appropriate site to identify research needs that support potential remediation strategies.

Looney, B.B.

2003-08-13

325

Timing of the last sequence boundary in a fluvial setting near the highstand shoreline—Insights from optical dating  

NASA Astrophysics Data System (ADS)

We investigated, by means of optical dating, the chronostratigraphic nature of the sequence boundary associated with the last glacial in a sandy to gravelly compound paleovalley fill, just landward of the highstand shoreline in the Rhine-Meuse Delta (Netherlands). Laterally extensive fluvial strata deposited during oxygen isotope stage 4, coeval with a major sea-level fall, unconformably overlie estuarine deposits from stage 5 or fluvial deposits from the penultimate glacial (stage 6). These chronostratigraphic relationships differ substantially from widely used models and indicate (1) that sequence-boundary formation in this setting was associated with the onset of pronounced sea-level fall, shortly after 80 ka; (2) that the time gap represented by the sequence boundary may be extremely small (<10 k.y.); (3) that the age of the sequence boundary may decrease both updip and downdip of the highstand shoreline; and (4) that our study does not provide viable diagnostic criteria for a sea-level controlled sequence boundary above the falling-stage systems tract. Despite the high-frequency, high-amplitude glacio-eustatic regime that might be considered ideal for the formation of an unambiguous unconformity, the last sequence boundary in this setting is commonly cryptic.

Törnqvist, Torbjörn E.; Wallinga, Jakob; Busschers, Freek S.

2003-03-01

326

Geological and Petrophysical Characterization of the Ferron Sandstone for 3-D Simulation of a Fluvial-Deltaic Reservoir  

SciTech Connect

The objective of this project is to develop a comprehensive, interdisciplinary, and quantitative characterization of a fluvial-deltaic reser v oir which will allow realistic inter-well and reservoir-scale modeling to be constructed for improved oil-field development in similiar reservoirs world-wide. The geological and petrophysical properties of the Cretaceous Ferron Sandstone in east-central Utah will be quantitatively determined . Both new and existing data will be integrated into a three-dimensional representation of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Results could improve reservoir management through proper infill and extension drilling strategies, reduction of economic risks, increased recovery from existing oil fields, and more reliable reserve calculations . Transfer of the project results to the petroleum industry is an integral component of the project. Four activities continued this quarter as part of the geological and petrophysical characterization of the fluvial-deltaic Ferron Sandstone in the Ivie Creek case-study area: (1) geostatistics, (2) field description of clinoform bounding surfaces, (3) reservoir modeling, and (4) technology transfer.

M. Lee Allison

1997-03-01

327

Estudo da evolução dinâmica fluvial dos rios do Amazonas com base em imagens de RADAR e satélite nos últimos 30 anos, balanço entre área de erosão e deposição e possíveis conseqüências para a ocupação humana  

Microsoft Academic Search

The Amazon region as resultant of geologic history and the climate, shelters a more extensive fluvial system and of bigger liquid mass of the Land. The analysis of products of remote sensing in the Amazônia is the technique that still persists as the main tool to assist in the execution of diverse scientific works. The agreement of the fluvial dynamics

Amaro Luiz Ferreira

328

Strategies for reservoir characterization and identification of incremental recovery opportunities in mature reservoirs in Frio Fluvial-Deltaic sandstones, south Texas: An example from Rincon Field, Starr County. Topical report.  

National Technical Information Service (NTIS)

Fluvial-deltaic sandstone reservoirs in the United States are being abandoned at high rates, yet they still contain more than 34 billion barrels of unrecovered oil. The mature Oligocene-age fluvial-deltaic reservoirs of the Frio Formation along the Vicksb...

L. McRae M. Holtz T. Hentz

1995-01-01

329

Secondary Natural Gas Recovery: Targeted Technology Applications for Infield Reserve Growth in Fluvial Reservoirs in the Frio Formation, Seeligson Field, South Texas. Topical Report, September 1, 1988-December 31, 1991.  

National Technical Information Service (NTIS)

The potential for secondary incremental recovery of natural gas exists in complex fluvial-deltaic reservoirs in the Texas Gulf Coast. Reservoirs in the Frio Fluvial-Deltaic Sandstone along the Vicksburg Fault Zone play (FR-4) in South Texas commonly conta...

W. A. Ambrose J. D. Grigsby B. A. Hardage R. P. Langford L. A. Jirik

1992-01-01

330

Fluvial depositional environment evolving into deltaic setting with marine influences in the buntsandstein of northern vosges (France)  

NASA Astrophysics Data System (ADS)

The Buntsandstein in the Northern Vosges (France) originates mainly in an inland braidplain fluvial environment which passes in the upper part of the sequence into deltaic milieu in the coastal plain along the border of the sea, with the continental environment finally being drowned with the transgression of the shallow sea. The fluvial sedimentation is characterized by the presence of two facies throughout the Buntsandstein : channel facies and overbank plain facies. The channel facies comprises sandy and conglomeratic deposits forming within active streams by strong currents, whereas the overbank plain facies is built up of silty-clayey sandstones or silt/clay originating in stagnant water in abandoned watercourses, ponds, pools and puddles. The significance of particularly the floodplain sediments is subjected to considerable changes throughout the Buntsandstein sequence. There are all stages of transition between overbank plain deposits being only preserved in ghost-like facies as reworked clasts due to effective secondary removal of primarily occasionally formed suspension fines, and an abundance of autochthonous floodplain sediments in the depositional record resulting from favourable conditions of primary origin and secondary preservation. Reworked ventifacts within fluvial channel sediments testify to subordinate aeolian influences in the alluvial plain, with reasonable reworking, however, having removed all in situ traces of wind activity. Declining aridity of palaeoclimate towards the top is indicated by the appearance of violet horizon palaeosols in the Zone-Limite-Violette and the Couches intermédiaires being accompanied by Bröckelbank carbonate breccias originating from concentration of reworked fragments of pedogenic carbonate nodules. Biogenic traces are in the lower part of the sequence mainly present as Planolites burrows in the finer-grained sediments. Palaeosalinities as revealed from boron contents indicate progressively increasing supersaturation of stagnant waters with time. The fluvial environment persists up to the lower part of the Grès à Voltzia where the progression of the sea towards the west gives rise to a close intertonguing of fluvial and marine influences in a deltaic setting. Lenticular sandstone bodies are laid down as stream mouth bars at the end of the distributary channels and as river bars in the watercourses during both normal and flood discharge. Silty-clayey sediments settle out in stagnant water in restricted ponds, pools and puddles as well as in extensive veneers of shallow water in the overbank plain between the streams. Carbonate-bearing deposits originate in the coastal littoral mud flat, marsh seam, beach belt and tidal flat. The Grès à Voltzia has the greatest palaeoenvironmental and palaeoecological significance in the Buntsandstein of the Northern Vosges due to the occurrence of a wealth of extraordinarily well-preserved plant and animal fossils (having been recovered by Louis Grauvogel during almost 50 years and since abt. 25 years by Jean-Claude Gall). The rich suite of faunal and floral elements includes aquatic invertebrates, terrestrial animals and continental plants. The aquatic invertebrate fauna lives in fresh lakes and brackish ponds in the overbank plain and in brackish lagoons in the coastal seam as well as in hypersaline and euhaline marginal marine waters. The terrestrial plants colonize both dry and wet substrates, and the continental fauna consists of mainly arthropods, amphibians and reptiles inhabiting the levee zones of standing and flowing waters and strolling across the desiccated flats. The marine euryhaline association of invertebrates is with time replaced by a stenohaline community, and the deltaic plain of the Grès à Voltzia is finally inundated by a pellicular transgression representing the first stage of the Muschelkalk sea setting an end to Buntsandstein continental deposition.

Gall, Jean-Claude

331

Depositional mechanisms and facies models of intertonguing aeolian environment and fluvial milieu in the middle buntsandstein of the mid-european triassic basin  

NASA Astrophysics Data System (ADS)

Intertonguing aeolian sand seas and fluvial braidplains occur abundantly in the upper part of the Middle Buntsandstein in various parts of the Mid-European Triassic Basin and are especially well-developed in the Eifel North-South-zone at the western margin of the depositional area. Based on assessment of the Buntsandstein regions and on comparative evaluation of other examples of interference between aeolian environment and fluvial milieu, the specific mechanisms controlling the significance of numerous distinctive sedimentary processes and the importance and nature of the mutual relationships are discussed. The main depositional mechanisms comprise migration, modification and merging of bedforms which are characterized by both similarities and distinctive features in each environment. The significance of migration, modification and merging in the aeolian milieu is ameliorated or deteriorated by the association of dune fields and river systems intersecting the erg in comparison to an extensive dune belt without coexisting stream networks. Common features in both aeolian environment and fluvial milieu are the cyclic composition of the sequence as well as depositional and erosional multistoreying of sediments by primary restriction of formation and secondary removal of parts of the cyclothems. The general facies zones of aeolian sand seas comprise the marginal or peripheral erg facies, the medial or transitional erg facies and the central or interior erg facies which are characterized by the extension of aeolian subenvironments, distribution of aeolian bedforms and degree of interference with associated fluvial systems as well as with the morphology of the pre-Triassic basement. The medial erg facies zone has the greatest significance for the evaluation of the mutual relationships as a consequence of the close association of nearly equally distributed aeolian and fluvial milieus. Considerable interference of the fluvial river systems with the aeolian belt result in overprinting and further subdivision of the general erg facies zones by regional environmental diversification which is best expressed in the complex of intertonguing aeolian dunes with fluvial channels and floodplains in the Middle Buntsandstein of the Eifel North-South-zone. The main influence in the narrow elongated depositional area is the regional variation of the dynamics of the fluvial systems as result of the sheltering, deflecting und punctuating function of the pre-Triassic basement bounding the basin at both sides, and as a consequence of supply of additional amounts of sediment material of lateral-marginal provenance to the axial-longitudinal transport. The Eifel North-South-zone is divided into five regions with different distribution and type of lithofacies associations in aeolian environment and fluvial milieu, comprising Southern Saar area, Northern Saar area, Southern Eifel, Western Eifel and Northern Eifel. The regional diversification of aeolian depositional environment stresses particularly the significance of the alluvial network and its behaviour in time and space as the dominant control on the distribution of dunes and interdunes. The distribution of small dune fields and large sand seas which are internally governed by division into the general aeolian facies zones and by regional diversification can be summarized in a basinal depositional model that comprises from the margin to the centre the succession of the proximal zone, medial zone I, medial zone II and distal zone. The occurrence of aeolian patches and complexes within these zones is controlled by major longitudinal and lateral changes of the river patterns as a consequence of variation of distance from the source area, palaeoslope gradient, and climatic and topographic influence of the margins. The four basin zones are characterized by variations in fluvial style predominantly in an ordered manner which are to a minor amount regionally punctuated by random changes. The intertonguing of aeolian and fluvial systems reaches its climax in the medial zone I. The major ultimate controls

Mader, Detlef

332

Fluvial Bank Erosion in the Meandering River Asker, UK: Insights from Computational Fluid Dynamics (CFD) Modelling  

NASA Astrophysics Data System (ADS)

River bank erosion often significantly contributes to the catchment sediment yield. Knowledge of the rates & controls on bank erosion events is therefore important in understanding sediment flux. In recent years progress has been made in understanding processes controlling large-scale mass failure (MF) of stream banks, but less attention has been paid to the role that direct fluvial erosion (FE) plays in bank retreat. This is an important omission, not only because FE is a significant process in its own right, but because FE also often triggers mass failure. FE models are typically of the form: E = k(? - ? c)b where E is the bank erosion rate, ? is the applied fluid shear stress, ? c is the critical stress for entrainment of the bank material, k is an empirically-derived erodibility parameter, and b is an empirically-derived exponent, often assumed to be close to unity. To apply this model, accurate observations of applied fluid stresses, FE rates & bank erodibility are required. Recent developments in bank erosion monitoring technology [e.g. Lawler, 1993], and in the quantification of the bank erodibility parameters k and ? c using jet-testing devices [e.g. Hanson and Simon, 2001; Dapporto, 2001], offer the means of determining FE rates and bank erodibility. Nevertheless, the problem of collecting the high-resolution spatially-distributed data needed to characterise near-bank fluid stresses remains. One possible solution is to use Computational Fluid Dynamics (CFD) models as a substitute for empirical data. CFD simulations potentially offer a means of acquiring near-bank, distributed, boundary shear stress data at very high spatial resolution. In contrast, empirical data sets of comparable spatial extent and resolution are very difficult to obtain, particularly during the large (competent) flows of interest here. The critical question is therefore whether CFD-derived data are sufficiently accurate for this purpose. Herein we evaluate a series of 3-dimensional CFD simulations for a (200 m long) meander loop on the River Asker at Bridport in southern England. CFD models under specific steady (peak) flow conditions were developed using FLUENT, with peak flow discharge estimates obtained from an adjacent gauging station. The geometry of each model was specified using DEMs of the channel created from high-resolution tacheometric surveys of the study reach, with water surface elevation defined using a network of crest gauges spaced at 20 m intervals along the reach. Zero slip boundary conditions were defined at all sidewall nodes and initial flow velocity vectors at all nodes at the upstream inlet were estimated with reference to 3D flow velocity data acquired using Acoustic Doppler Velocimetry (ADV) at this location. Simulated flow fields for the extent of the study reach were then evaluated by comparing simulated and observed surface velocity vectors, the latter being derived from Particle Image Velocimetry (PIV), supplemented by ADV data in selected (accessible) locations. Finally, we use the near-bank boundary shear stress data obtained from the CFD models to develop insight into the nature and effectiveness of FE processes within the study reach.

Darby, S. E.; Rinaldi, M.; Rossi Romanelli, L.; Spyropoulos, E.

2003-12-01

333

Human impact on late-Holocene hillslope and fluvial sediment dynamics: a field and modeling approach  

NASA Astrophysics Data System (ADS)

The human impact on sediment fluxes is evidenced by numerous integrated field studies. Most of these studies, however, remain qualitative and site-specific, leaving several questions on landscape response unresolved. How intense is the landscape response to human impact compared to the response to natural environmental change ? When did humans took over control and to what extent ? What is the importance of internal catchment dynamics in regulating sediment fluxes ? How do human and natural induced environmental change interact ? Detailed field-based approaches have recently been made for several areas that now provide partial answers to several of these questions. These include time-differentiated catchment sediment budgets, catchment-wide analysis of historic sedimentation rates and cumulative density functions of colluvial and alluvial activity. However, the poor temporal resolution of the sedimentary record makes it in most cases impossible to decipher e.g. the impact of short-lasting climatic events. Spatial modelling techniques could provide a means for estimating the impact of past (and future) environmental change on hillslope and fluvial sediment dynamics. But which model approach needs to be used ? Which variables and process-interactions need to be included ? Here, we present results from the application of the geomorphic WATEM/SEDEM model on two contrasting environments in Belgium and SW Turkey. For the Dijle catchment (Loess Belt, Belgium), this model was combined with a climate reconstruction model and a spatially distributed land use model driven by historical and archaeological data. Model results match the history of sediment dynamics as evidenced by the time-differentiated sediment budget very well. Moreover, the model approach made it possible to estimate the relative importance of human and climatic impact on the Holocene sediment dynamics. Compared to the mid-Holocene time period, human induced land use change increased sediment fluxes by 6000%, whilst climate change modified sediment flux by only 6%. Furthermore, with the model it is possible to simulate the importance of settlement density and patterns on slop-channel coupling as illustrated by changing sediment delivery ratios. Contrary to loess catchments in western and central Europe, many regions in the Mediterranean are confronted with much smaller contemporary sedimentation rates compared to Hellenistic and Roman times. Results of the WATEM/SEDEM model for a small basin in SW-Turkey shows that this is not due to an increase in erosion-reducing vegetation cover after this period (as evidenced in pollen studies), nor due to a drying of the climatic conditions, but rather due to a decrease in soil erodibility through time. Intensive land use during Hellenistic and Roman times eroded the topsoil, thereby increasing its stoniness, which prevented further erosion. The dynamic nature of soils thus needs to be taken into account when modelling the landscape response to human or climatic impact. However, this process of soil depletion is not important in catchments with thick loess cover such as in the Dijle catchment. Hence, depending in the environmental settings of the area considered, a more complex model approach may be needed.

Verstraeten, Gert; Notebaert, Bastiaan; Dusar, Bert; Peeters, Iris; Govers, Gerard; van Rompaey, Anton; Poesen, Jean; Lang, Andreas

2010-05-01

334

Geological and petrophysical characterization of the Ferron Sandstone for 3-D simulation of a fluvial-deltaic reservoir. Technical progress report, July 1, 1996--September 30, 1996.  

National Technical Information Service (NTIS)

The objective of this project is to develop a comprehensive, interdisciplinary, and quantitative characterization of a fluvial-deltaic reservoir which will allow realistic inter-well and reservoir-scale modeling to be constructed for improved oil-field de...

M. L. Allison

1996-01-01

335

The distribution of the Rocky Mountain tailed frog ( Ascaphus montanus ) in relation to the fluvial system: implications for management and conservation  

Microsoft Academic Search

The mating, egg-laying, and larval development of tailed frogs occur in dynamic mountain streams. During the lengthy (up to 5 years) aquatic residency these species are vulnerable to channel disturbances that can be exacerbated by land uses. Researchers have highlighted specific tailed frog habitat associations but never in the context of fluvial system processes. Based on an extensive regional study with

Linda Dupuis; Pierre Friele

2006-01-01

336

Evolution and preservation potential of fluvial and transgressive deposits on the Louisiana inner shelf: understanding depositional processes to support coastal management  

Microsoft Academic Search

The barrier-island systems of the Mississippi River Delta plain are currently undergoing some of the highest rates of shoreline retreat in North America (~20 m\\/year). Effective management of this coastal area requires an understanding of the processes involved in shoreline erosion and measures that can be enacted to reduce loss. The dominant stratigraphy of the delta plain is fluvial mud

James Flocks; Michael D. Miner; David C. Twichell; Dawn L. Lavoie; Jack Kindinger

2009-01-01

337

Determining controls on sediment storage volumes and residence times on valley bottoms in steeplands: debris flow and fluvial evacuation of tributaries and their respective confluence deposits  

Microsoft Academic Search

Approximately 10% of basin denudation is stored for ~103 yr at the transition between highly episodic debris flows and relatively continual fluvial transport. This storage is a critical link in the source-to-sink sediment system and may force widening of valley bottoms. We hypothesize that tributaries dominated by debris flow evacuation of sediment from their mouths (``debris flow tributaries'') form larger

W. T. Frueh; S. T. Lancaster

2010-01-01

338

Detailed chronology of mid-altitude fluvial system response to changing climate and societies at the end of the Little Ice Age (Southwestern Alps and Cévennes, France)  

Microsoft Academic Search

Over a historical timescale, landscapes have been strongly affected by fluctuations in climate and by the impact of human societies. This study examines the historical evolution of mid-altitude fluvial systems in the Western Alps and Cévennes (SE Massif Central) in the context of marked climate and anthropogenic change at the end of the Little Ice Age (late 19th century). This

Laurent Astrade; Nicolas Jacob-Rousseau; Jean-Paul Bravard; Françoise Allignol; L. Simac

2011-01-01

339

Linking diagenesis to sequence stratigraphy in fluvial and shallow marine sandstones: Evidence from the Cambrian–Ordovician lower sandstone unit in southwestern Sinai, Egypt  

Microsoft Academic Search

By integrating diagenesis and sequence stratigraphy, the distribution of diagenetic alterations and their impact on reservoir quality was investigated within a sequence stratigraphic framework using the fluvial and shallow marine sandstones in the Cambrian–Ordovician succession of southwest Sinai. The perographic and geochemical analysis of the studied sandstone revealed that the eogenetic alterations display fairly systematic spatial and temporal distribution patterns

Masoumeh Kordi; Brian Turner; Alaa M. K. Salem

2011-01-01

340

Deposition and diagenesis of the lacustrine-fluvial Cangfanggou Group (uppermost Permian to Lower Triassic), southern Junggar Basin, NW China: a contribution from sequence stratigraphy  

Microsoft Academic Search

The Junggar Basin in NW China contains lacustrine hydrocarbon source rocks which are among the highest quality of hydrocarbon potential in the world. Oil reservoirs in the basin are very substantial: target reservoirs span Carboniferous to Tertiary strata and include Permo-Triassic lacustrine and fluvial sandstones. The Junggar Basin was a foreland basin during the late Permian to Cenozoic, possibly with

Zhaohui Tang; John Parnell; Alastair H. Ruffell

1994-01-01

341

The Association of Anastomosed fluvial deposits and dinosaur tracks, eggs, and nests: Implications for the interpretation of floodplain environments and a possible survival strategy for ornithopods  

SciTech Connect

The St. Mary River Formation (Maastrichtian) consists of anastomosed fluvial deposits containing several hundred track-bearing beds. Paleontologic and sedimentologic analyses of these beds indicate that large herbivores, ornithopods, inhabited a seasonal wetland dominated by marshes and lakes. Shallow tracks in fine-grained sediments, formed as the sediments dewatered to the point of stiffness, display the highest resolution of detail. The preservation potential of tracks in anastomosed fluvial deposits is large because of the abundance of soft substrates to record the tracks and the occurrence of annual flooding to rapidly bury the footprints. Comparison of the St. Mary River Formation to other anastomosed fluvial deposits as old as the Early Jurassic confirms that tracks are common in this type of deposit. The variation in preservation of track types and depth of penetration raises the possibility that ornithopods employed a survival strategy involving seasonal wetlands. The wetlands provided an abundant food source and at the same time the combination of a soft substrate and flooded conditions would have effectively countered the superior speed and agility of large carnivores. The relatively common occurrence of ornithopod eggshells from anastomosed fluvial deposits suggests that the abundant food supply accompanying the wet season also made the wetlands an ideal location to rear young. These data can be used to refine the interpretations of depositional environment derived from the sediments by allowing estimates to be made regarding the early post-depositional conditions of the sediments. 95 refs., 7 figs., 1 tab.

Nadon, G.C. (Univ. of Wisconsin, Madison (United States))

1993-02-01

342

Geogene and anthropogenic controls on the mineralogy and geochemistry of modern alluvial–(fluvial) gold placer deposits in man-made landscapes in France, Switzerland and Germany  

Microsoft Academic Search

Five study areas in the Cévennes, France, the Gotthard Massif, Switzerland, and from the western edge of the Bohemian Massif, Germany, have been selected for an investigation of the natural and human impacts on modern alluvial–(fluvial) gold placer deposits. The current investigation involved the study of grain-related parameters such as morphology, grain size and accessory minerals in gold aggregates in

H. G. Dill

2008-01-01

343

Recent exhumational pattern across the Lhasa Terrain: Revealed by detrital zircon fission track and U\\/Pb ages from modern fluvial sediments along Yarlung-Tsangpo, South Tibet  

Microsoft Academic Search

Detrital samples from the foreland basin and so forth depositional environments archive the evolutional phases of adjacent orogens. Modern fluvial sediments, similarly, provide the integrated information of exposed bedrocks in the studied drainages where sometimes few access is allowed to get the in situ samples. However, the nature of the dispersed detrital ages has long hampered our interpretation in thermal

Shao-Yi Huang; Yue-Gau Chen; Tsung-Kwei Liu; Zhongquan Cao

2010-01-01

344

Large striated burrows from fluvial deposits of the Neogene Vinchina Formation, La Rioja, Argentina: A crab origin suggested by neoichnology and sedimentology  

Microsoft Academic Search

This study includes three aspects: 1) the ichnotaxonomic treatment of large and dominantly vertical burrows ornamented with sharp bioglyphs from the fluvial Neogene Vinchina and Toro Negro formations (northwest Argentina); 2) the description and interpretation of the sedimentary facies where these burrows occur; and 3) neoichnologic observations on large ornamented burrows from seasonal wetlands of the Río Pilcomayo National Park

Ricardo N. Melchor; Jorge F. Genise; Juan L. Farina; María V. Sánchez; Laura Sarzetti; Graciela Visconti

2010-01-01

345

The response of a high sediment yield depositional system to episodic rises in sea level: The record from the Brazos fluvial system, central Texas coast  

SciTech Connect

High resolution seismic data, cores, and platform borings have been utilized to investigate the response of the Brazos fluvial system, a high sediment yield depositional system, to late Pleistocene-Holocene episodic rises in sea level. This investigation was conducted in order to provide control for a related study of the Trinity-Sabine fluvial system, a low sediment yield depositional system. The Brazos incised valley, which was carved during the Wisconsin eustatic lowstand, was abandoned during an interval of rapid eustatic rise. The fluvial-deltaic system occupied the adjacent interfluve following abandonment of the incised valley. This behavior contrasts sharply with the responses of the Trinity-Sabine low sediment yield depositional system to rapid base level rises. Stream piracy, triggered by the episodic eustatic rises, played an important role in diverting the fluvial system of the high sediment yield system out of the lowstand entrenched valley and onto the interfluve. The research presented in this paper suggests that exploration geologists working with up-dip portions of high sediments yield depositional systems in the transgressive systems tract may find prospects (slightly modified wave-dominated delta deposits encased in marine shales) by searching along strike, away from the abandoned incised valley, at positions along depositional dip that correspond to eustatic stillstands. Accretionary structures observed in recently acquired seismic data indicate that the down-dip portion of the high sediment yield incised valley also contains a large volume of sand.

Bartek, L.R.; Anderson, J.B.; Abdulah, K.C. (Rice Univ., Houston, TX (United States))

1991-03-01

346

Post Waterflood CO2 Miscible Flood in Light Oil, Fluvial-Dominated Deltaic Reservoir (Pre-Work and Project Proposal), Class I  

SciTech Connect

This project outlines a proposal to improve the recovery of light oil from waterflooded fluvial dominated deltaic (FDD) reservoir through a miscible carbon dioxide (CO2) flood. The site is the Port Neches Field in Orange County, Texas. The field is well explored and well exploited. The project area is 270 acres within the Port Neches Field.

Bou-Mikael, Sami

2002-02-05

347

Signatures and significance of aeolian, fluvial, bacterial and diagenetic magnetic mineral fractions in Late Quaternary marine sediments off Gambia, NW Africa  

NASA Astrophysics Data System (ADS)

Two gravity cores retrieved off NW Africa at the border of arid and subtropical environments (GeoB 13602-1 and GeoB 13601-4) were analyzed to extract records of Late Quaternary climate change and sediment export. We apply end-member (EM) unmixing to 350 acquisition curves of isothermal remanent magnetization (IRM). Our approach enables to discriminate rock magnetic signatures of aeolian and fluvial material, to determine biomineralization and reductive diagenesis. Based on the occurrence of pedogenically formed magnetic minerals in the fluvial and aeolian EMs, we can infer that goethite formed in favor to hematite in more humid climate zones. The diagenetic EM dominates in the lower parts of the cores and within a thin near-surface layer probably representing the modern Fe2+/Fe3+ redox boundary. Up to 60% of the IRM signal is allocated to a biogenic EM underlining the importance of bacterial magnetite even in siliciclastic sediments. Magnetosomes are found well preserved over most of the record, indicating suboxic conditions. Temporal variations of the aeolian and fluvial EMs appear to faithfully reproduce and support trends of dry and humid conditions on the continent. The proportion of aeolian to fluvial material was dramatically higher during Heinrich Stadials, especially during Heinrich Stadial 1. Dust export from the Arabian-Asian corridor appears to vary contemporaneous to increased dust fluxes at the continental margin of NW Africa emphasizing that meltwater discharge in the North Atlantic had an enormous impact on atmospheric dynamics.

Just, Janna; Dekkers, Mark J.; Dobeneck, Tilo; Hoesel, Annelies; Bickert, Torsten

2012-09-01

348

Fluvial terrace formation in the northern Upper Rhine Graben during the last 20 000 years as a result of allogenic controls and autogenic evolution  

Microsoft Academic Search

The northern Upper Rhine Graben hosts a well-preserved Late Weichselian and Holocene fluvial terrace sequence. Terraces differ in elevation, morphology, and overbank sediment characteristics. The purpose of this study was to determine the relative importance of allogenic controlling factors versus autogenic evolution on the successive formation of these terraces. For a representative valley segment (the Gernsheim region), results from previous

Gilles Erkens; Rainer Dambeck; Koen P. Volleberg; Marjolein T. I. J. Bouman; Johanna A. A. Bos; Kim M. Cohen; Jakob Wallinga; Wim Z. Hoek

2009-01-01

349

Impacts of a Swine Manure Spill on Phosphorus Partitioning in a Fluvial System: Evaluation of an alternative Manure Spill Remediation Method  

Technology Transfer Automated Retrieval System (TEKTRAN)

Within the last decade there has been an international shift in livestock production that has resulted in an increased herd size per farm and a greater frequency of manure spills. Therefore, the objectives of this study were to determine the P partitioning between fluvial sediments following a manur...

350

Seasonal Movement and Distribution of Fluvial Adult Bull Trout in Selected Watersheds in the Mid-Columbia River and Snake River Basins  

Microsoft Academic Search

From 1997 to 2004, we used radio telemetry to investigate movement and distribution patterns of 206 adult fluvial bull trout (mean, 449 mm FL) from watersheds representing a wide range of habitat conditions in northeastern Oregon and southwestern Washington, a region for which there was little previous information about this species. Migrations between spawning and wintering locations were longest for

Steven J. Starcevich; Philip J. Howell; Steven E. Jacobs; Paul M. Sankovich

2012-01-01

351

Fossil Energy: Post Waterflood CO(2) Miscible Flood in Light Oil Fluvial Dominated Deltaic Reservoir - Project Performance Years 1995-1997.  

National Technical Information Service (NTIS)

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 ...

S. B. Mikael

2002-01-01

352

Using fluvial terraces to determine Holocene coastal erosion and Late Pleistocene uplift rates: An example from northwestern Hawke Bay, New Zealand  

Microsoft Academic Search

In order to make robust predictions of future coastal processes and hazards, historical rates of coastal processes such as coastal erosion need to be put into a long-term (Holocene) context. In this study a methodology is proposed that uses fluvial terraces to construct longitudinal profiles which can be projected offshore to infer paleo-coastline positions. From these positions, an average Holocene

Nicola J. Litchfield

2008-01-01

353

Constraining Basin Geometry and Fault Kinematics on the Santo Tomas Segment of the Agua Blanca Fault Through a Combined Geophysical and Structural Study  

Microsoft Academic Search

The Santo Tomas basin, located in northern Baja California, formed at a right step in the dextral Agua Blanca fault (ABF). The ABF extends for more than 120km east from Punta Banda, with an east-west strike, and represents the southernmost fault in the San Andreas system of faulting. The basin is located roughly 40km south of Ensenada where the Agua

A. Springer; P. Wetmore; J. Fletcher; C. B. Connor; S. Callihan; J. Beeson; J. Wilson

2008-01-01

354

Stratigraphy of the Arriaga Palaeolithic sites. Implications for the geomorphological evolution recorded by thickened fluvial sequences within the Manzanares River valley (Madrid Neogene Basin, Central Spain)  

NASA Astrophysics Data System (ADS)

The Arriaga Palaeolithic sites, located within the Middle–Late Pleistocene thickened terrace (TCMZ: + 18–22 m) of the Manzanares River valley (Madrid, Central Spain), were subject to intensive archaeological and palaeontological prospecting during the 1980s. Compilation of documents from these old excavations, together with new geoarchaeological, sedimentological, pedological and geophysical data, allow us to locate the morpho-stratigraphic position of the analysed sites within the overall stratigraphy of the TCMZ. This thickened terrace comprises two main fluvial sequences (Lower and Upper) topped by a thick (2.5–5 m) alluvial–colluvial formation. The fluvial sequences are stacked in the study site located in the lowermost reach of the valley, but display complex inset relationships upstream, where they are individualized in two different terrace levels at + 18–22 and + 12–15 m. Terrace thickening was primarily controlled by synsedimentary subsidence caused by dissolution of the evaporitic substratum and locally influenced and backfed by tectonic activity. The regional analysis of the dated (TL and OSL) fluvial sequences containing Palaeolithic sites within the TCMZ, together with new TL dates provided in this study, indicate that the three sedimentary sequences in the TCMZ are time-transgressive valley-fill bodies. Terrace thickening started before the Last Interglacial Period (MIS 6 or older) and continued during whole MIS 5 (lower fluvial sequence) and MIS 4 (upper fluvial sequence) reaching the MIS 3 (top alluvial formation), the latter characterized by the accumulation of alluvial–colluvial sequences derived from the main tributaries and valley slopes. The TCMZ records the Middle–Late Pleistocene boundary, but also the transition between the Lower and Middle Palaeolithic periods during the Late MIS 5 (ca. 96 to 74 ka). The studied Arriaga sites contain evolved Lower Palaeolithic industry (evolved Acheulean techno-complexes) and warm faunal assemblages located within the Lower fluvial sequence, but apparently well constrained Middle Palaeolithic sites are placed within the Upper fluvial sequence at other upstream locations. Deposition of the thickened alluvium was mainly controlled by the upstream advance of dissolution-induced subsidence phenomena, blurring the impact of Late Pleistocene climatic cycles and producing time-transgressive longitudinal valley-fill bodies (i.e. sedimentary sequences). Late Quaternary climatic changes only seem to control the incision/aggradation cycles after the termination of the TCMZ from the Late MIS 3. Dates related to the development of younger inset terraces indicate that they are apparently linked with cold Heinrich events H4 to H1. These younger inset terraces yield cold faunal assemblages and abundant Middle Palaeolithic "Mousterian" assemblages.

Silva, P. G.; López-Recio, M.; Tapias, F.; Roquero, E.; Morín, J.; Rus, I.; Carrasco-García, P.; Giner-Robles, J. L.; Rodríguez-Pascua, M. A.; Pérez-López, R.

2013-08-01

355

Bimodal palaeocurrents in braided-type inland fluvial environments in the buntsandstein of middle europe and other continental formations  

NASA Astrophysics Data System (ADS)

Bimodal directional distributions can form on various scales and by numerous mechanisms in fluvial environments including braided river systems. The examination of case studies from the Lower Triassic Buntsandstein of Middle Europe and comparative assessment of other fluvial successions reveal five scales of bimodalities which are ordered in a hierarchical manner: very small-scale, small-scale, medium-scale, large-scale and very large-scale bimodalities. The different hierarchical orders of bimodalities are interrelated in four ways depending on length of the sequence, occurrence or absence of subordinate bimodalities and type of organization of the divergent palaeocurrent directions. Very small-scale bimodalities comprise differences between subsets within sets and between sets within cosets (herring-bone cross-stratification) and originate by cross or reverse flow during isolated phases within stages of infilling of individual channels. Small-scale bimodalities comprise differences between sets within cosets and originate by cross or reverse flow during repeated phases within stages of infilling of individual channels. Medium-scale bimodalities comprise differences between cosets within cyclothems and between cyclothems within megacycles and originate by cross or reverse flow between stages of infilling of several channels and various orientations of the streams, combined with effects of condensation of the depositional record. Large-scale bimodalities comprise differences between cyclothems within megacycles and originate by changes of current direction between stages of aggradation of parts of the alluvial plain. Very large-scale bimodalities comprise differences between megacycles within the magnacycle and originate by changes of current direction during stages of aggradation of the alluvial plain or by superimposition of successive separate alluvial plains. The effect of medium-scale bimodalities in the depositional record is strongly enhanced by condensation of the sequence by two mechanisms: primary-sedimentary restriction to suppression of formation and secondary-erosional degradation to removal of floodplain deposits and finer-grained watercourse sands. As a consequence of vertical stacking of successive channel sediments to multistorey complexes and amalgamation of adjoining stream deposits to multilateral sheets by horizontal coalescence, different orientations of successive channels are emphasized by juxtaposition due to cut out of products of intervening subenvironments. The most prominent example of large-scale bimodalities is a time-cyclic trend of sedimentation with spatially continuous and time-concordant shifting of the dominantly braided river channels in a transitional meandering thalweg — braided stream pattern, resulting in changes of transport directions with time in a sinusoidal manner. The sinuous reaches between both negative and positive extremes of deviation values and the meandering deviation curves can be correlated. The subdivision of the Buntsandstein sequence into units with comparable palaeocurrent deviations gives evidence of the applicability of the palaeoflow interpretation in the stratigraphical analysis of continental formations. In contrast to the smaller-scale bimodalities which are exclusively controlled by autocyclic processes of aggradation of the alluvial plain, the formation of very large-scale bimodalities is often governed by allocyclic influences from tectonical events. The palaeoenvironmental interpretation and depositional modelling of fluvial successions can be greatly enhanced by an integrated approach including both examination of energy-sensitive sedimentary structures and analysis of the bidirectional distribution of the palaeocurrents. The numerous possibilities of changes and variations of palaeocurrent directions in time and space on several scales underline the architectural complexity of fluvial systems due to extrabasinal and internal controls on the orientation of flows.

Mader, Detlef

356

Fluvial-marine transitional depositional environment influencing the diagenesis in the buntsandstein of thuringia (German Democratic Republic)  

NASA Astrophysics Data System (ADS)

The Buntsandstein in Thuringia (German Democratic Republic) consists predominantly of sandy and gravelly fluvial sediments which in parts of the sequence pass into marine deposits. Extensive braided-river systems produced vast stream sand bar and sand sheet sediments which coalesced by lateral amalgamation and vertical stacking to persisting complexes that permit the stratigraphical connection of the Folgen megacycles. In the marginal parts of the basin, a higher amount of channel conglomerates occurs, whereas towards the centre of the depression, fine-grained overbank deposits become more abundant and thicker. Marine influences are frequent in the estuarine reach, and the fluvial magnacycle is terminated by the major transgression of the R'ot sea. The palaeocurrent directions reflect three main sources of sediment material, with the flows deriving from Gallian Massif, western part of Bohemian Massif and northern border of Bohemian Massif (Western Erzgebirge) and being directed towards northnortheast, northwest and westnorthwest, respectively. The infilling of the depositional area results in a seaward migration of facies being typical for progradation. The geological framework for the diagenetic alterations of the sediments comprises a large epicontinental basin with platform deposition, resulting in low total thickness of the sequence and shallow depth of burial due to thin overburden. Progressive burial diagenesis is terminated by uplift and weathering descending from the surface during Cretaceous and Tertiary, resulting in overprinting effects of a retrograde or diaphthoritic weathering diagenesis. The postsedimentary phenomena and processes in sandstones include formation of rim cements comprising hematite, feldspar, quartz and chalcedony; growth of basal cements being dolomite and calcite, gypsum and anhydrite, and kaolinite; phase changes and transformations representing mainly illitic, kaolinitic and carbonatic degradation of feldspars; and authigenesis of heavy minerals such as anatase, brookite, barite and garnet. The reconstruction of the temporal succession of diagenetic processes from intergrowth and contact relationships and from minus-cement-porosities shows that most of the phenomena are of an early nature thus being still controlled by the depositional environment and the palaeogeographical setting. The establishment of a more intense burial diagenesis was suppressed by the only shallow subsidence and by the inhibition of immigration of extraformational solutions due to the sealing effect of the underlying Zechstein and the overlying Röt halites, respectively. The influence of the fluvial-marine transitional depositional environment on the diagenesis is best reflected by the areal restriction of cement types fitting into the palaeogeographical framework. The transitional belt between the central and marginal parts of the basin is characterized by an evolution of diagenetic pore waters from concentrated sea water containing enriched amounts of Ca, Mg, CO3 and SO4 thus producing carbonate and sulphate cements, whereas the post-sedimentary history in the marginal areas is controlled by undersaturated fluvial fresh waters giving rise to precipitation of quartz and feldspar cements. In contrast to the progressive burial diagenesis, the retrograde weathering diagenesis is not related to the original depositional environment, but is only bound to the tectonical position of the sequence. Compaction is insignificant in sandstones, but is of considerable importance in mudstones. A large amount of the compaction finally resulting in reduction of the thickness to abt. one fifth already takes place in the first hundred metres of burial thus being almost in equilibrium with sedimentation. Differential subsidence due to compaction of mudstones in diversified milieu results in lateral differentiations between deposition and omission, with additional sediments forming in the muddy central part of the basin being equivalent to gaps in the sandy marginal belt. The increasingly marginal nature of the sediments from the bot

Langbein, Rolf

357

Post waterflood CO{sub 2} miscible flood in light oil, fluvial-dominated deltaic reservoir. FY 1993 annual report  

SciTech Connect

The project is a Class 1 DOE-sponsored field demonstration project of a CO{sub 2} miscible flood project at the Port Neches Field in Orange County, Texas. The project will determine the recovery efficiency of CO{sub 2} flooding a waterflooded and a partial waterdrive sandstone reservoir at a depth of 5,800. The project will also evaluate the use of a horizontal CO{sub 2} injection well placed at the original oil-water contact of the waterflooded reservoir. A PC-based reservoir screening model will be developed by Texaco`s research lab in Houston and Louisiana State University will assist in the development of a database of fluvial-dominated deltaic reservoirs where CO{sub 2} flooding may be applicable. This technology will be transferred throughout the oil industry through a series of technical papers and industry open forums.

Davis, D.W.

1995-03-01

358

Seasonal Movement and Distribution of Fluvial Adult Bull Trout in Selected Watersheds in the Mid-Columbia River and Snake River Basins  

PubMed Central

From 1997 to 2004, we used radio telemetry to investigate movement and distribution patterns of 206 adult fluvial bull trout (mean, 449 mm FL) from watersheds representing a wide range of habitat conditions in northeastern Oregon and southwestern Washington, a region for which there was little previous information about this species. Migrations between spawning and wintering locations were longest for fish from the Imnaha River (median, 89 km) and three Grande Ronde River tributaries, the Wenaha (56 km) and Lostine (41 km) rivers and Lookingglass Creek (47 km). Shorter migrations were observed in the John Day (8 km), Walla Walla (20 km) and Umatilla river (22 km) systems, where relatively extensive human alterations of the riverscape have been reported. From November through May, fish displayed station-keeping behavior within a narrow range (basin medians, 0.5–6.2 km). Prespawning migrations began after snowmelt-driven peak discharge and coincided with declining flows. Most postspawning migrations began by late September. Migration rates of individuals ranged from 0.1 to 10.7 km/day. Adults migrated to spawning grounds in consecutive years and displayed strong fidelity to previous spawning areas and winter locations. In the Grande Ronde River basin, most fish displayed an unusual fluvial pattern: After exiting the spawning tributary and entering a main stem river, individuals moved upstream to wintering habitat, often a substantial distance (maximum, 49 km). Our work provides additional evidence of a strong migratory capacity in fluvial bull trout, but the short migrations we observed suggest adult fluvial migration may be restricted in basins with substantial anthropogenic habitat alteration. More research into bull trout ecology in large river habitats is needed to improve our understanding of how adults establish migration patterns, what factors influence adult spatial distribution in winter, and how managers can protect and enhance fluvial populations.

Starcevich, Steven J.; Howell, Philip J.; Jacobs, Steven E.; Sankovich, Paul M.

2012-01-01

359

Determining controls on sediment storage volumes and residence times on valley bottoms in steeplands: debris flow and fluvial evacuation of tributaries and their respective confluence deposits  

NASA Astrophysics Data System (ADS)

Approximately 10% of basin denudation is stored for ~103 yr at the transition between highly episodic debris flows and relatively continual fluvial transport. This storage is a critical link in the source-to-sink sediment system and may force widening of valley bottoms. We hypothesize that tributaries dominated by debris flow evacuation of sediment from their mouths (“debris flow tributaries”) form larger mainstem deposits than those dominated by fluvial evacuation from their mouths (“fluvial tributaries”). In six ~103 m-long, mainstem valley reaches that span contributing areas of 0.1-5.1 km2 in predominantly uncut forests of the Tyee Formation of the Oregon Coast Range, we measured: 1) deposit volumes from surveyed long profiles and valley transects, and mapped in-stream bedrock outcrops; and, 2) sediment residence time distributions from radiocarbon dating of 30-35 charcoal samples per reach. We found the largest deposits (> 20 x 103 m3; ~40-60% of total reach storage) are at, or due to, mainstem confluences with debris flow tributaries, some debris flow confluences have deposits < 3 x 103 m3, and deposits at confluences of fluvial tributaries range ~2.5-10 x 103 m3. Results also show that (1) mainstem reaches dominated by fluvial evacuation store more sediment, but not necessarily for longer, than those dominated by debris flow evacuation; (2) sediment storage volumes and residence times do not vary systematically with mainstem contributing area; (3) residence times do not vary systematically with deposit mechanisms; (4) debris flow deposits that dam mainstem valley bottoms store more sediment than those that only form discrete fans; and 5) formation of persistent, or repeatedly-forming, debris dams may be favored by debris flow deposition from symmetric sources such as two debris flow-dominated tributaries opposite from one-another across a valley bottom.

Frueh, W. T.; Lancaster, S. T.

2010-12-01

360

Seasonal movement and distribution of fluvial adult bull trout in selected watersheds in the mid-Columbia River and Snake River basins.  

PubMed

From 1997 to 2004, we used radio telemetry to investigate movement and distribution patterns of 206 adult fluvial bull trout (mean, 449 mm FL) from watersheds representing a wide range of habitat conditions in northeastern Oregon and southwestern Washington, a region for which there was little previous information about this species. Migrations between spawning and wintering locations were longest for fish from the Imnaha River (median, 89 km) and three Grande Ronde River tributaries, the Wenaha (56 km) and Lostine (41 km) rivers and Lookingglass Creek (47 km). Shorter migrations were observed in the John Day (8 km), Walla Walla (20 km) and Umatilla river (22 km) systems, where relatively extensive human alterations of the riverscape have been reported. From November through May, fish displayed station-keeping behavior within a narrow range (basin medians, 0.5-6.2 km). Prespawning migrations began after snowmelt-driven peak discharge and coincided with declining flows. Most postspawning migrations began by late September. Migration rates of individuals ranged from 0.1 to 10.7 km/day. Adults migrated to spawning grounds in consecutive years and displayed strong fidelity to previous spawning areas and winter locations. In the Grande Ronde River basin, most fish displayed an unusual fluvial pattern: After exiting the spawning tributary and entering a main stem river, individuals moved upstream to wintering habitat, often a substantial distance (maximum, 49 km). Our work provides additional evidence of a strong migratory capacity in fluvial bull trout, but the short migrations we observed suggest adult fluvial migration may be restricted in basins with substantial anthropogenic habitat alteration. More research into bull trout ecology in large river habitats is needed to improve our understanding of how adults establish migration patterns, what factors influence adult spatial distribution in winter, and how managers can protect and enhance fluvial populations. PMID:22655037

Starcevich, Steven J; Howell, Philip J; Jacobs, Steven E; Sankovich, Paul M

2012-05-24

361

Fluvial terrace formation in the eastern Fenwei Basin, China, during the past 1.2 Ma as a combined archive of tectonics and climate change  

NASA Astrophysics Data System (ADS)

The key to understanding the fluvial response to climate change and surface uplift is a thorough distinguishing between their roles in terrace formation. Previous studies have tended to attribute the fluvial behavior of deposit-incision alternation to climate cyclicity. A preliminary explanation is proposed here for terrace formation in the eastern part of the Fenwei Basin, China. The observed fluvial terrace sequence was developed by the Yellow River deeply downcutting into the Emei Platform, which was uplifted within the eastern Fenwei Basin, and therefore it probably records the tectonic history of this platform. On the basis of the magnetostratigraphy and optically stimulated luminescence (OSL) dating, a ca. 1.2 Ma chronology was established for this terrace sequence. Pedostratigraphic analysis of the loess deposits accumulated on each tread reveals that the terrace deposits are overlain immediately by a paleosol bed, suggesting that the abandonment of these terraces due to fluvial incision occurred at the transitions from glacial to interglacial climates. The glacial-interglacial climate cycle probably has a temporal control on the fluvial behavior of deposit-incision alternation, even though the Yellow River develops in the subsiding Fenwei Basin. The terrace generation may be sporadic and in the form of unusual stacked pattern before the Emei Platform was uplifted within the eastern Fenwei Basin. The terrace staircases however, formed in synchrony with glacial-interglacial climate cycles since this platform began to uplift in the late Middle Pleistocene. This result indicates that uplift may be necessary in large terrace staircase genesis. It can force the river system to downcut deeply enough during climatic transitions to separate terrace levels adequately, favoring the generation and subsequent preservation of the terrace treads. The terrace sequence of the Yellow River in the eastern Fenwei Basin therefore can be considered as a combined archive of climate change and local tectonic activity.

Hu, Zhenbo; Pan, Baotian; Wang, Junping; Cao, Bo; Gao, Hongshan

2012-10-01

362

Towards a holistic sediment budget in a glacier forefield (Gepatschferner/Austria) - The contribution of fluvial sediment transport  

NASA Astrophysics Data System (ADS)

Glaciers in the European Alps have been retreating since the end of the Little Ice Age around 1850. Where the glaciers shrink, they leave unconsolidated sediment stores (moraines, till, glacifluvial deposits). These deposits are highly vulnerable to subsequent erosion. But knowledge of sediment fluxes and the interrelated geomorphological processes in proglacial areas, based on field-data, is lacking. Therefore, a new joint research project PROSA (High resolution measurements of the morphodynamic in rapidly changing PROglacial Systems of the Alps), is set up in the Kaunertal valley, Austrian Alps. It is focussed on the quantification of recent and subrecent sediment transport processes in the entire catchment in order to construct a holistic sediment budget. The fluvial system (main river) in proglacial areas is more or less continuously fed with (fine) sediment by glacial melt water (glacial milk) and infrequently (e.g. during rainstorm events) supplied with sediment by landslides, debris flows, rock fall from the slopes. A part of the sediment input is temporary stored in intermitted sinks, such as the river bed, bars or braid plains. These stores can be reworked and become a source for fluvial sediment transport mainly during floods. These sediment transporting processes are highly variable in both time and space. So the main aim of this project is the investigation of the interrelations of the sediment transport rates in the proglacial river below the Gepatschferner in the Kaunertal valley and the connected sediment sources and how these interrelations influence the sediment budget of the river. Suspended sediment load, solute load and bed load will be measured at several locations in the river on different time scales (event-based, daily, weekly etc.). Additionally the surface changes of important sediment sources (moraines, bars), which are directly connected to the river system, will be quantified by a comparison of multitemporal terrestrial and airborne laserscanning data.

Morche, D.; Baewert, H.; Schmidt, K.-H.

2012-04-01

363

Geological and Petrophysical Characterization of the Ferron Sandstone for 3-D Simulation of a Fluvial-Deltaic Reservoir.  

SciTech Connect

The objective of this project is to develop a comprehensive, interdisciplinary, and quantitative characterization of a fluvial- deltaic reservoir which will allow realistic inter-well and reservoir-scale modeling to be constructed for improved oil-field development in similar reservoirs world-wide. The geological and petrophysical properties of the Cretaceous Ferron Sandstone in east-central Utah will be quantitatively determined. Both new and existing data will be integrated into a three-dimensional representation of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Results could improve reservoir management through proper infill and extension drilling strategies, reduction of economic risks, increased recovery from existing oil fields, and more reliable reserve calculations. Transfer of the project results to the petroleum industry is an integral component of the project. Two activities continued this quarter as part of the geological and petrophysical characterization of the fluvial-deltaic Ferron Sandstone: (1) evaluation of the Ivie Creek case-study area and (2) technology transfer. The Ivie Creek case-study evaluation work during the quarter focused on the two parasequence sets, the Kf-1 and Kf-2, in the lower Ferron Sandstone. This work included: (1) clinoform characterization, (2) parasequence characterization from elevation and isopach maps, and (3) three-dimensional facies modeling. Scaled photomosaic panels from the Ivie Creek amphitheater (south-facing outcrop belt) and Quitchupah Canyon (Fig. 1) provide a deterministic framework for two apparent-dip cross sections. These panels along with other photomosaic coverage and data from five drill holes, ten stratigraphic sections, and 22 permeability transacts (Fig. 1), acquired during two field seasons, provided the necessary information for this geologic evaluation and creation of the models to be used in reservoir simulations.

Allison, M.L.

1997-07-01

364

Provenance of fluvial sandstones at the start of late Jurassic Early Cretaceous rifting in the Cameros Basin (N. Spain)  

NASA Astrophysics Data System (ADS)

The Cameros Basin (Iberian Chain, Central Spain) developed during the latest Jurassic Early Cretaceous in an extensional regime characterized by high rates of subsidence. Its sedimentary fill has been subdivided into eight depositional sequences (DS) mainly composed of continental sediments. DS 1 and DS 2 represent the first rifting stage (Tera Group, Tithonian). The purpose of this study is to characterize the Tera Group in the eastern part of the basin based on provenance criteria derived from fluvial sandstones. In this area of the basin, the Tera Group can be subdivided into three formations: the Ágreda Formation, the Magaña Formation and the Sierra de Matute Formation. These formations are composed of alluvial-fan deposits, meandering fluvial sediments and lacustrine palustrine mudstones. A quantitative petrographic study indicated the presence of three main petrofacies in the Tera Group. The close correlation between petrofacies and lithostratigraphic units indicates that sandstone composition is a powerful tool for deciphering the tectonic processes active during the initial rift stages of the Cameros Basin. Petrofacies 1 is sedimentolithic (mean: Qm54F3Lt43) and represents erosion of the Jurassic marine pre-rift substratum (mainly Kimmeridgian limestones) during deposition of the DS 1 alluvial fan deposits (Ágreda Fm.). Petrofacies 2 is quartzofeldspathic, and can be subdivided into Petrofacies 2A, with an average composition of Qm84F15Lt1 and Petrofacies 2B, whose average composition is Q71F23Lt6. Petrofacies 2 was generated by the erosion of low to medium-grade metamorphic terranes and plutonic source rocks. It characterizes the Magaña Fm. (DS 2). Petrofacies 3 is quartzolithic (mean: Qm67F16Lt17), and is attributed to tectonic reactivation of the basin. This petrofacies characterizes the Sierra de Matute Fm. (DS 2). Thus, the provenance evolution of this basin is characterized by erosion of the pre-rift sedimentary substratum, followed by unroofing of the basement, as recorded in other ancient and modern rifted basins.

González-Acebrón, Laura; Arribas, José; Mas, Ramón

2007-11-01

365

The igapó of the Negro River in central Amazonia: Linking late-successional inundation forest with fluvial geomorphology  

NASA Astrophysics Data System (ADS)

Despite important progress on Amazonian floodplain research, the flooded forest of the Negro River "igapó" has been little investigated. In particular, no study has previously focused the linkage between fluvial geomorphology and the floristic variation across the course of the river. In this paper we describe and interpret relations between igapó forest, fluvial geomorphology and the spatial evolution of the igapó forest through the Holocene. Therefore, we investigate the effect of geomorphological units of the floodplain and channel patterns on tree diversity, composition and structural parameters of the late-successional igapó forest. Our results show that sites sharing almost identical flooding regime, exhibit variable tree assemblages, species richness and structural parameters such as basal area, tree density and tree heights, indicating a trend in which the geomorphologic styles seem to partially control the organization of igapó's tree communities. This can be also explained by the high variability of well-developed geomorphologic units in short distances and concentrated in small areas. In this dynamic the inputs from the species pool of tributary rivers play a crucial role, but also the depositional and erosional processes associated with the evolution of the floodplain during the Holocene may control floristic and structural components of the igapó forests. These results suggest that a comprehensive approach integrating floristic and geomorphologic methods is needed to understand the distribution of the complex vegetation patterns in complex floodplains such as the igapó of the Negro River. This combination of approaches may introduce a better comprehension of the temporal and spatial evolutionary analysis and a logic rationale to understand the vegetation distribution and variability in function of major landforms, soil distributions and hydrology. Thus, by integrating the past into macroecological analyses will sharpen our understanding of the underlying forces for contemporary floristic patterns along the inundation forests of the Negro River.

Montero, Juan Carlos; Latrubesse, Edgardo M.

2013-10-01

366

Diagenesis and reservoir potential of Permian-Triassic fluvial/lacustrine sandstones in the southern Junggar basin, northwestern China  

SciTech Connect

The Junggar basin is one of the largest oil-producing areas in China, and contains Upper Permian lacustrine oil shales with some of the greatest hydrocarbon potential in the world. In this study, we present the diagenetic characteristics of Permian-Triassic sandstones from the southern Junggar basin and evaluate their reservoir potential. The uppermost Permian and Lower Triassic Cangfanggou Group in the southern Junggar basin is characterized by alternating fluvial and lacustrine deposits, whereas the Middle-upper Triassic Xiaoquangou Group was deposited predominantly in a lacustrine environment; fluvial and deltaic sedimentation was subordinate. The sandstones of the Cangfanggou and Xiaoquangou groups are volcanic litharenites. Their detrital modes and textures of volcanic fragments suggest a primarily andesitic/basaltic volcanic-arc provenance. Early diagenesis of the sandstones is characterized by nonferroan calcite cementation, grain-coating, pore-lining clay minerals, and the initial dissolution of detrital grains. Authigenic quartz; pore-filling phyllosilicates; pore-filling, grain-replacive zeolites; albitized detrital plagioclase; authigenic K-feldspar; illite; and late calcite dominate burial diagenesis. The formation of iron oxides and dissolution of calcite cement resulted from tectonic uplift during the Tertiary. Albitization and zeolite formation during burial are among the most pronounced diagenetic processes that affected these sandstones. Pore-filling clay minerals, calcite, and zeolites have substantially reduced sandstone porosity. However, appreciable primary porosity has been preserved by the formation of early clay coats and pore linings, which retarded further cementation. Secondary porosity is present to varying degrees in the sandstones and is the result of dissolution of unstable framework grains.

Tang, Zhaohui; Longstaffe, F.J. [Univ. of Western Ontario, London (Canada); Parnell, J. [Queen`s Univ. of Belfast (United Kingdom)

1997-11-01

367

Fluvial sedimentology and architecture of the middle Frio Formation (Oligocene), Jim Wells, Klegerg, and Nueces Counties, south Texas  

SciTech Connect

The middle Frio Formation of the northeastern Gueydan fluvial system comprises fluvial and overbank deposits averaging 2,000 to 3,000 ft in thickness. Discrete genetic intervals are defined from subsurface studies using four cores totaling 575 ft, high-resolution resistivity borehole images, and electrical logs. A genetic interval is composed of four facies: (1) Channel-fill facies (30-ft thick and 2,500-ft wide) includes an overall fining-upward texture and upward diminution in sedimentary structure scale: intraclast gravel lag; large-scale trough cross-stratified, medium-grained sandstone; parallel-stratified and ripple-laminated fine-grained sandstone to sandy mudstone containing pedogenic nodule and root molds; (2) splay fine-grained sandstones (up to 20-ft thick) are parallel-stratified and ripple-laminated and are organized into beds with variable vertical thickness trends; (3)Levee sandstones and mudstones are thinly bedded with low-angle surfaces and slump structures; (4) floodplain mudstones contain structures and fabrics indicating variable wet and dry conditions. Three scales of architectural elements are readily identifiable in the subsurface. (1) Multitiered lateral accretion bars are the principal; channel-filling element; (2) Levee-confined channel systems have a lower tortuosity than the inferred thalweg, and splay complexes extend up to 2 mi from channel systems; (3) discrete genetic intervals form a continuum of stacking patterns: from laterally stacked, where sandstone bodies contact one another or are vertically separated by only a few feet of the floodplain facies, to vertically stacked, where floodplain facies substantially separate sandstone bodies.

Kerr, D.R. (Univ. of Texas, Austin (United States))

1991-03-01

368

Fluvial sedimentary styles and associated depositional environments in the buntsandstein west of river rhine in saar area and pfalz (F.R. Germany) and vosges (France)  

NASA Astrophysics Data System (ADS)

The Buntsandstein west of river Rhine in Saar area, Pfalz and Vosges consists of three fluvial magnacycles which are characterized by different associated non-alluvial environments. The stratigraphic sequence is divided by several unconformities reflecting tectonic movements which were connected with periods of extension of the depositional area. Two major phases and two minor events are recognized by the evaluation of the Pfalz unconformity and the Lothringen unconformity, and the Leuter unconformity and the Saar unconformity, respectively. The Lower Buntsandstein (including Zechstein) compries the first magnacycle and is built up of alluvial-fan deposits, fluvial braidplain sediments and marine to lagoonal deposits. Some aeolian sands as well as several palaeosols are also present. The palaeolandscape consists of alluvial fans seaming the margin of the basin and fluvial braidplains reaching from the toes of the fan belt to the centre of the depositional area which is occupied by a lagoonal sea that partially evolves into a playa-lake with progressive refreshment. The Middle Buntsandstein comprises the second magnacycle and is composed of an alternation of aeolian Dünnschichten and fluvial Felsbänke. The third facies are alluvial-fan deposits of palaeogeographically restricted distribution along the margins of the basin. The aeolian Dünnschichten originate in the marginal parts of chott-type depressions (in comparison with the recent Chott Djerid in Tunesia) where rising ground water moistens the dry sediments that are laid down on the playa floor and thus allows their enhanced preservation. In dry periods, wind-blown sand is spread out as plane sheets or as migrating wind ripple trains, or accumulates to barchanoid-type dunes that advance across the flat. Depending on supply of sand, all stages of transition between dune fields with only narrow interdune corridors between the ridges and interdune playas with isolated widely-spaced dunes are developed. The individual sand storms operating in the erg are recorded in a mm-scale graded grain-size lamination. The desert-type setting is divided into depositional sand ergs where aeolian bedforms migrate, and deflationary gravel serirs where pebbly fluvial sediments are winnowed, resulting in concentration of the gravel to residual lags and in abundant grinding of clasts to ventifacts. During time of flooding of the chotts by atmospheric precipitation, fluvial incursions or rising ground water level, lacustrine playa deposits settle out in shallow stagnant water. The fluvial Felsbänke originate in wadi-type braided river systems intersecting the erg and serir zones and often redepositing aeolian sand which is derived from undercutting during abandonment and displacement of the watercourses. The stream complexes are partially fed at their proximal ends by runoff from local alluvial fans which are aligned along parts of the margins of the basin. The Upper Buntsandstein comprises the third magnacycle which is split into three megacycles that in turn are divided into several phases. A change from generally arid to primarily semi-arid climate along with tectonical up-lift in the source area results in extinction of aeolian deposition and gives rise to formation of Violette Horizonte calcrete palaeosols which are widespread throughout the Upper Buntsandstein, if their origin was not inhibited by the dynamics of the fluvial systems. The palaeosols occur in different evolutionary stages and are mainly characterized by the typical blue-violet colour, presence of root tubes, carbonate nodules and carbonate crusts, destratification and polyedric jointing. The fluvial fining-upwards cyclothems are formed in braided river systems which partially pass into meandering stream complexes. At the top of the Upper Buntsandstein, the alluvial inland plain is converted into a delta complex in the coastal plain along the approaching sea, and with a sequence of alternating progradation and recession events, the Muschelkalk transgression finally inundates the continental setting.

Dachroth, Wolfgang

369

Precio del agua y relocalización del recurso en la economía andaluza. Una aproximación desde un modelo de equilibrio general aplicado  

Microsoft Academic Search

El objetivo de este trabajo consiste en analizar los efectos que tendría un incremento en la tarifa del agua del sector agrario sobre la conservación del recurso, la eficiencia en el consumo y la posible relocalización del mismo entre los diferentes sectores productivos. La política tarifaria se aplicará sobre el sector agrario debido, por un lado, al excesivo consumo de

M. Alejandro Cardenete; G. J. D. Hewings; E. Velázquez

2005-01-01

370

An assessment of Spain's Programa AGUA and its implications for sustainable water management in the province of Almería, southeast Spain  

Microsoft Academic Search

Spain's Programa AGUA was proposed in 2004 as a replacement for the Spanish National Hydrological Plan and represented a fundamental policy shift in national water management from large inter-basin water transfers to a commitment to desalination. Twenty-one desalination facilities are planned for six provinces on the Spanish Mediterranean coast to supplement their water needs. These include the province of Almería

Stuart R. Downward; Ros Taylor

2007-01-01

371

Unmanned aerial monitoring of fluvial changes in the vicinity of selected gauges of the Local System for Flood Monitoring in Klodzko County, SW Poland  

NASA Astrophysics Data System (ADS)

Only high resolution spatial data enable precise measurements of various morphometric characteristics of river channels and ensure meaningful effects of research into fluvial changes. Using ground-based measurement tools is time-consuming and expensive. Traditional photogrammetry often does not reach a desired resolution, and the technology is cost effective only for the large-area coverage. The present research introduces potentials of UAV (Unmanned Aerial Vehicle) for monitoring fluvial changes. Observations were carried out with the ultralight UAV swinglet CAM produced by senseFly. This lightweight (0,5 kg), small (wingspan: 80 cm) aircraft allowed frequent (with approximately monthly sampling resolution) and low-cost missions. Three hydrologic gauges, the surroundings of which were the target of series of photos taken by camera placed in airplane frame, belong to the Local System for Flood Monitoring in K?odzko County (SW Poland). The only way of obtaining reliable results is an appropriate image rectification, in order to measure morphometric characteristics of terrain, free of geometrical deformations induced by the topographical relief, the tilt of the camera axis and the distortion of the optics. Commercially available software for the production of digital orthophotos and digital surface models (DSMs) from a range of uncalibrated oblique and vertical aerial images was successfully used to achieve this aim. As a result of completing the above procedure 9 orthophotos were generated (one for each of 3 study areas during 3 missions). For extraction of terrain parameters, a DSM was produced as a result of bundle block adjustment. Both products reached ultra-high resolution of 4cm/px. Various fluvial forms were classified and recognized, and a few time series of maps from each study area were compared in order to detect potential changes within the fluvial system. We inferred on the origins of the short-term responses of fluvial systems, and such an inference was feasible due to the analysis of metrological and hydrological data recorded by the Local System for Flood Monitoring in K?odzko County. Orthophotos and DSMs, generated from imagery obtained by UAV, show high accuracy of results and are suitable for measuring fluvial changes. This approach moves beyond current restrictions of traditional data collecting, due to its unprecedented spatial and temporal resolution and low cost of application.

Jeziorska, Justyna; Witek, Matylda; Niedzielski, Tomasz

2013-04-01

372

The contribution of fluvial and mass wasting processes to sedimentary budget in mountain catchments of the southern Apennines, Italy  

NASA Astrophysics Data System (ADS)

Erosion quantification is an important topic for both scientific and social community, although the large number of prediction models developed in the last decades showed controversial results and limited reliability (Boardman, 2006 and references therein). On the other hand, direct measurements of sediment flux are extremely rare and limited to a few years. This is true also for southern Apennines where, in this work, the sedi