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1

ANLISIS DE CAMBIOS EN LA CALIDAD DEL AGUA EN PUERTO RICO UTILIZANDO SISTEMAS DE INFORMACIN GEOGRFICA  

E-print Network

ANÁLISIS DE CAMBIOS EN LA CALIDAD DEL AGUA EN PUERTO RICO UTILIZANDO SISTEMAS DE INFORMACI�N maduros son beneficiosos para la calidad del agua en Puerto Rico. Este resultado se obtuvo de agua de los ríos; (2) mapas de cobertura y uso de terreno; (3) valores de precipitación; y (4

Gilbes, Fernando

2

Anlisis de cambios en la calidad del agua en Puerto Rico utilizando Sistemas de  

E-print Network

An�lisis de cambios en la calidad del agua en Puerto Rico utilizando Sistemas de Informaci�n Geogr � Calidad del agua (Puerto Rico) � Maria Uriarte de Columbia University � Charles B. Yackulic , Yili Lim � Calidad del agua (Cuenca Guavate) � Keyla Torres, Elizabeth Pab�n y Fredmarie Oyola, Alexandra Rivera

Gilbes, Fernando

3

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

4

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

5

TURISMO FLUVIAL: ACTIVIDAD LÚDICA Y ECONÓMICA  

Microsoft Academic Search

RESUMEN El turismo activo está posicionándose como una actividad económica de gran interés, especialmente en zonas rurales de gran valor paisajístico y ambiental puesto que el desarrollo que genera se puede calificar de sostenible en vista de que el impacto en el medio ambiente no es significativo. Dentro de este contexto las actividades ligadas al turismo fluvial tanto en aguas

Daniel MATEOS FUERTES

6

Conoces tu Agua Arizona?  

E-print Network

¿Conoces tu Agua Arizona? Una Guía para el Consumidor sobre las Fuentes de Agua, la Calidad del Agua, las Reglamentaciones y las Opciones de Tratamiento del Agua en los Hogares. #12;Mapa de Arizona. Fuente: Cartel del mapa de las fuentes de agua en Arizona, 2002, Centro de Investigatciones de los

Fay, Noah

7

Fluvial Landforms on Maps  

NSDL National Science Digital Library

This is an in-class exercise on fluvial landforms and topographic map reading. Students work in groups on a series of "classic" geomorphic maps and answer a suite of questions. The questions are designed to cover basic identification up to queries on chronology, process, role of climate and substrate, etc. After going through the classic maps, we pull out local topographic maps and find many of the same features and discuss how they relate to the local geology and glacial history. Designed for a geomorphology course Has minimal/no quantitative component

8

Quaternary fluvial archives: achievements of the Fluvial Archives Group  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

9

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

10

Tuesday, March 13, 2007 MARS FLUVIAL GEOMORPHOLOGY  

E-print Network

and Hydrothermal Features [#2300] Fluvial and hydrothermal features are a key target for the HiRISE camera. Here we summarize some of the highlights of the early HiRISE imaging of fluvial features, paying special attention

Rathbun, Julie A.

11

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

12

Conoces tu Agua Arizona? Introduccin ....................................................................................... 6  

E-print Network

¿Conoces tu Agua Arizona? Introducción ....................................................................................... 6 I. Historia y Fuentes de Agua 1.1 Historia del Uso del Agua en Arizona .......................................... 9 1.2 Fuentes de Agua ....................................................................... 16 1

Cushing, Jim. M.

13

Sedimentation in fluvial and lacustrine environments  

Microsoft Academic Search

Sedimentation in rivers is dominated by a complex set of physical processes, associated with the unidirectional flow of water.\\u000a Variations in these processes give rise to different fluvial channel types, whose character can commonly be recognised in\\u000a the ancient record. Chemical and biological processes are comparatively unimportant in fluvial sedimentation.\\u000a \\u000a In contrast, physical, chemical or biological processes can each dominate

Brian R. Rust

1982-01-01

14

Muestreo de aguas subterrneas a varias profundidades  

E-print Network

Muestreo de aguas subterráneas a varias profundidades en pozos con rejilla continua Metodología y: bomba de muestreo Produce una mezclaProduce una mezcla de aguas dede aguas de diferentesdiferentes divisoria de aguas: "Separation Pumping Technique", Nilsson et al., 1995 divisoria de aguas bomba superior

Politècnica de Catalunya, Universitat

15

Morphology of fluvial networks on Titan: Evidence for structural control  

E-print Network

Although Titan’s surface shows clear evidence of erosional modification, such as fluvial incision, evidence for tectonism has been less apparent. On Earth, fluvial networks with strongly preferred orientations are often ...

Burr, Devon M.

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

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

18

Especial2012Agua Produccin de soja  

E-print Network

89 Especial2012Agua Producci�n de soja y uso de agua fre�tica en ambientes medanosos El objetivo de CONICET. Palabras Claves: agua, napa fre�tica, aporte h�drico, salinidad, ambiente medanoso, soja, rendimiento. #12;90 Especial2012Agua RESUMEN Durante los �ltimos 15 a�os el cultivo de soja se ha expandido

Nacional de San Luis, Universidad

19

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

20

Martian fluvial conglomerates at Gale Crater  

USGS Publications Warehouse

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.

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

2013-01-01

21

Fluvial Erosion of Craters on Titan  

NASA Astrophysics Data System (ADS)

There are few identifiable impact craters on Titan, especially near the polar regions. One explanation for this observation is that the craters are being destroyed through hydrological processes, such as weathering, fluvial incision and deposition. In this work, we use a landscape evolution model to determine whether or not this is a viable mechanism for crater destruction on Titan. We find that fluvial degradation can modify craters to the point where they would be unrecognizable by an orbiting spacecraft such as Cassini, given enough time and a large enough weathering rate. It can also remove central peaks and fill in central pits, possibly explaining their absence in Titan craters. If fluvial degradation is the dominant mechanism destroying craters on Titan, then the 80 km diameter crater Soi is on average twice as old as the similarly sized crater Sinlap, and the 40 km diameter crater on Shikoku Facula is on average five times as old as the similarly sized crater Momoy. There has likely been some infilling by sand in these craters, so these age differences represent upper limits. Nonetheless, since all of these craters are located in Titan’s extensive sand seas, the difference in depths suggests there is a range of crater ages on the surface of Titan.

Neish, Catherine; Molaro, Jamie L.; Lora, Juan; Howard, Alan D.; Kirk, Randolph L.; Schenk, Paul; Bray, Veronica J.

2014-11-01

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

Fluvial landscapes of the Harappan civilization.  

PubMed

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

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

2012-06-26

24

Reconstructing Fluvial Morphology from Set Thickness Statistics  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

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

Changing our View of Aggradational Fluvial Systems - The Distributary Fluvial System (DFS) Paradigm  

Microsoft Academic Search

Many numerical methods exist for modeling fluvial stratigraphy, however all require development of sound conceptual models of processes and facies distributions that are formed in aggradational settings before they can reasonably capture and represent facies geometries and distributions. A review of approximately 700 modern continental sedimentary basins around the world showed that rivers in these basins are not tributary in

G. S. Weissmann; A. J. Hartley; G. Nichols; L. A. Scuderi; M. Olson; H. Buehler; R. Banteah

2008-01-01

27

Uso Eficiente del Agua en Ingenios Azucareros  

Microsoft Academic Search

El impacto que produce el alto consumo de agua en regiones donde este recurso es limitado, alienta al desarrollo de nuevas técnicas que permitan analizar la administración eficiente del agua en las industrias y que comúnmente se concreta realizando balances detallados para diferentes configuraciones propuestas de uso de agua. En este trabajo se presenta una metodología alternativa, mediante el cálculo

Alejandra Ingaramo; Humberto Heluane; Mauricio Colombo; Tomás Argüello; Mario Cesca

28

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

NASA Astrophysics Data System (ADS)

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

Gilvear, David J.

1999-12-01

29

JORNADA AGUA Y ENERGA Organiza: Instituto Universitario del Agua y de las Ciencias Ambientales (IUACA)  

E-print Network

JORNADA AGUA Y ENERGÍA Organiza: Instituto Universitario del Agua y de las Ciencias Ambientales el ciclo integral del agua Daniel Prats Rico Catedrático de Ingeniería Química 13:00-14:00 Agua Domingo Zarzo Martínez Director de I+D+i de Valoriza Agua 19:00-21:00. Marco jurídico de la explotación

Escolano, Francisco

30

Early HiRISE Observations of Fluvial and Hydrothermal Features  

Microsoft Academic Search

Fluvial and hydrothermal features are a key target for the HiRISE camera. Here we summarize some of the highlights of the early HiRISE imaging of fluvial features, paying special attention to the many spectacular images of gullies already obtained by the

V. C. Gulick; A. S. McEwen

2007-01-01

31

Introduction Fluvial Processes in Small Southeastern Watersheds L. Allan James  

E-print Network

Introduction Fluvial Processes in Small Southeastern Watersheds L. Allan James Scott A. Lecce Lisa in Small Southeastern Watersheds L. ALLAN JAMES, SCOTT A. LECCE, LISA DAVIS The seven papers into three sections concerned with fluvial processes and fea- tures in small watersheds. Part One con- tains

James, L. Allan

32

Legitimizing Fluvial Ecosystems as Users of Water: An Overview1  

Microsoft Academic Search

We suggest that fluvial ecosystems are legiti- mate users of water and that there are basic ecological principles guiding the maintenance of long-term ecological vitality. This article articulates some fundamental relation- ships between physical and ecological processes, presents basic principles for maintaining the vitality of fluvial ecosys- tems, identifies several major scientific challenges and op- portunities for effective implementation of

ROBERT J. NAIMAN; STUART E. BUNN; CHRISTER NILSSON; GEOFF E. PETTS; GILLES PINAY

2002-01-01

33

Effective timescales of coupling within fluvial systems  

NASA Astrophysics Data System (ADS)

This paper presents a review of the coupling concept in fluvial geomorphology, based mainly on previously published work. Coupling mechanisms link the components of the fluvial system, controlling sediment transport down the system and the propagation of the effects of base-level change up the system. They can be viewed at several scales: at the local scale involving within-hillslope coupling, hillslope-to-channel coupling, and within-channels, tributary junction and reach-to-reach coupling. At larger scales, coupling can be considered as zonal coupling, between major zones of the system or as regional coupling, relating to complete drainage basins. These trends are illustrated particularly by the examples of hillslope-to-channel coupling in the Howgill Fells, northwest England, badland systems in southeast Spain, alluvial fans in Spain, USA and UAE, and base-level-induced dissection of Neogene sedimentary basins in southeast Spain. As the spatial scales increase, so do the timescales involved. Effective temporal scales relate to magnitude and frequency characteristics, recovery time and propagation time, the relative importance changing with the spatial scale. For downsystem coupling at the local scale, the first two are important, with propagation time increasing in importance in larger systems, especially in those involving upsystem coupling related to base-level change. The effective timescales range from the individual event, with a return period of decades, through decadal to century timescales for downsystem coupling, to tens to hundreds of thousands of years for the basinwide response to base-level change. The effective timescales influence the relative importance of factors controlling landform development.

Harvey, Adrian M.

2002-05-01

34

Titan's Impact Craters and Associated Fluvial Features  

NASA Astrophysics Data System (ADS)

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

Gilliam, A.; Jurdy, D. M.

2012-12-01

35

Cyclicity in sediment signals from combined aeolian and fluvial systems  

NASA Astrophysics Data System (ADS)

Limited research has been carried out on the interaction between aeolian and fluvial systems - mainly focusing on the landforms and characteristic landscapes left by their interaction. How these two geomorphic systems interact dynamically is largely unknown - and difficult to assess from field evidence due to the long time scales these systems may operate over. This paper describes a numerical modelling study combining a fluvial geomorpic model (CAESAR-Lisflood) and an aeolian dune slab model (DECAL). When both process are combined it leads to a cyclity in sediment output from both fluvial and aeolian systems. Cycles in sediment delivery coincide with episodes of river avulsion and landscape re-adjustment around dune fields. This research may have important implications for our understanding of the timing of changes in these systems as well as the build up of sedimentary architectures in aeolian/fluvial systems.

Coulthard, Tom; Liu, Baoli

2014-05-01

36

Titan's fluvial valleys: Morphology, distribution, and spectral properties  

NASA Astrophysics Data System (ADS)

Titan's fluvial channels have been investigated based on data obtained by the Synthetic Aperture Radar (SAR) instrument and the Visible and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft. In this paper, a database of fluvial features is created based on radar-SAR data aiming to unveil the distribution and the morphologic and spectral characteristics of valleys on Titan on a global scale. It will also study the spatial relations between fluvial valleys and Titan's geologic units and spectral surface units which have become accessible thanks to Cassini-VIMS data. Several distinct morphologic types of fluvial valleys can be discerned by SAR-images. Dendritic valley networks appear to have much in common with terrestrial dendritic systems owing to a hierarchical and tree-shaped arrangement of the tributaries which is indicative of an origin from precipitation. Dry valleys constitute another class of valleys resembling terrestrial wadis, an indication of episodic and strong flow events. Other valley types, such as putative canyons, cannot be correlated with rainfall based on their morphology alone, since it cannot be ruled out that they may have originated from volcanic/tectonic action or groundwater sapping. Highly developed and complex fluvial networks with channel lengths of up to 1200 km and widths of up to 10 km are concentrated only at a few locations whereas single valleys are scattered over all latitudes. Fluvial valleys are frequently found in mountainous areas. Some terrains, such as equatorial dune fields and undifferentiated plains at mid-latitudes, are almost entirely free of valleys. Spectrally, fluvial terrains are often characterized by a high reflectance in each of Titan's atmospheric windows, as most of them are located on Titan's bright ‘continents’. Nevertheless, valleys are spatially associated with a surface unit appearing blue due to its higher reflection at 1.3 ?m in a VIMS false color RGB composite with R: 1.59/1.27 ?m, G: 2.03/1.27 ?m, and B: 1.27/1.08 ?m; the channels either dissect pure bluish surface units or they are carved into terrain with a mixed spectral signature between bright and bluish surface materials. The global picture of fluvial flows clearly indicates a high diversity of parameters controlling fluvial erosion, such as climatic processes, as well as surface and bedrock types. Recent fluvial activity is very likely in the north polar region in contrast to more arid conditions at lower latitudes and at the south pole of Titan. This divergence is probably an indication of seasonal climatic asymmetries between the hemispheres. However, traces of previous fluvial activity are scattered over all latitudes of Titan, which is indicative of previous climatic conditions with at least episodic rainfall.

Langhans, M. H.; Jaumann, R.; Stephan, K.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Baines, K. H.; Nicholson, P. D.; Lorenz, R. D.; Soderblom, L. A.; Soderblom, J. M.; Sotin, C.; Barnes, J. W.; Nelson, R.

2012-01-01

37

Timescales of fluvial activity and intermittency in Milna Crater, Mars  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

38

Legitimizing Fluvial Ecosystems as Users of Water: An Overview  

Microsoft Academic Search

We suggest that fluvial ecosystems are legitimate users of water and that there are basic ecological principles guiding the\\u000a maintenance of long-term ecological vitality. This article articulates some fundamental relationships between physical and\\u000a ecological processes, presents basic principles for maintaining the vitality of fluvial ecosystems, identifies several major\\u000a scientific challenges and opportunities for effective implementation of the basic ecological principles,

ROBERT J. NAIMAN; STUART E. BUNN; CHRISTER NILSSON; GEOFF E. PETTS; GILLES PINAY; LISA C. THOMPSON

2002-01-01

39

Erosion of biofilm-bound fluvial sediments  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

40

Fluvial erosion on Mars: Implications for paleoclimatic change  

NASA Technical Reports Server (NTRS)

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

Gulick, Virginia C.; Baker, Victor R.

1993-01-01

41

Bar morphodynamics in the fluvial-tidal zone  

NASA Astrophysics Data System (ADS)

The hydrodynamics and deposits of the Tidally-Influenced Fluvial Zone (TIFZ) are complex because it experiences competing fluvial and tidal flows, sometimes moderated by waves, and spatially and temporally variable rates of sediment transport and deposition. This paper presents a new integrated field dataset from the Columbia River Estuary, USA, that quantifies the response of the flow structure, bed morphology and bar stratigraphy to fluvial-tidal flows. A new 3-year, field and modelling program that started in 2011, has been monitoring the dynamics and deposits of a 40 km-reach of the Columbia River Estuary. Data obtained so far throughout the TIFZ include: bathymetry using MBES, flow using ADCP, subsurface sedimentology using GPR and shallow coring to 5 m. First results suggest there is a complex spatial and temporal lag in the response of the bed morphology and deposits to the fluvial-tidal flows. Zones of strong ebb and flood flow do not necessarily produce channel beds dominated by bi-directional bedforms. Many mid-channel bars are stable over decadal time periods. This paper will illustrate the variety in bar morphologies and channel change throughout the fluvial-tidal zone and contrast these bar dynamics with examples from purely fluvial environments.

Ashworth, P. J.; Best, J. L.; Nicholas, A.; Parsons, D. R.; Prokocki, E.; Sambrook Smith, G.; Simpson, C.

2012-12-01

42

Artculo publicado en "Lanjarn: paisajes del agua". Ed. Balneario de Lanjarn, S.A. 35-64. AGUAS DE SIERRA NEVADA; AGUAS DE LANJARON  

E-print Network

Artículo publicado en "Lanjarón: paisajes del agua". Ed. Balneario de Lanjarón, S.A. 35-64. 1999 AGUAS DE SIERRA NEVADA; AGUAS DE LANJARON A. Castillo Martín*, J.J. Cruz Sanjulián** y J. Benavente Herrera** * CSIC e Instituto del Agua de la Universidad de Granada ** Instituto del Agua de la Universidad

Castillo, Antonio

43

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

44

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

45

Emergency Factsheet for Tratando Agua Almacenada con Cloro  

E-print Network

Emergency Factsheet for Tratando Agua Almacenada con Cloro Monty C. Dozier, Profesor Asistente y Fertilidad de Suelos El Sistema Universitario Texas A&M Al tratamiento del agua potable para mejorar su contaminaciónbacteriológica del agua. Este método tambiénpuede ser usado por los propietarios de pozos de agua particulares

46

Fluvial-deltaic sedimentation and stratigraphy of the ferron sandstone  

USGS Publications Warehouse

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

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

1997-01-01

47

Estimates of fluvial erosion on Titan from sinuosity of lake shorelines  

E-print Network

Titan has few impact craters, suggesting that its surface is geologically young. Titan's surface also has abundant landforms interpreted to be fluvial networks. Here we evaluate whether fluvial erosion has caused significant ...

Tewelde, Yodit

48

Propagac ~ao acustica em aguas profundas na presenca de massas d'aguas de mesoescala na costa sudoeste de Portugal  

E-print Network

Propagac¸ ~ao ac´ustica em ´aguas profundas na presenc¸a de massas d'´aguas de mesoescala na costa trabalho baseia-se no estudo da propagac¸ ~ao sonora em ´aguas oce^anicas profundas na costa Portuguesa massa d'´agua de mesosescala. Mostraremos que tal massa d'´agua d´a origem `a um acoplamento entre dois

Jesus, Sérgio M.

49

Paru dans : CD ROM del Congreso Ibrico sobre Gestin y Planificacin de Aguas, El Agua a Debate desde la universidade, Simposio Gestin de aguas, participacin  

E-print Network

1 1 Paru dans : CD ROM del Congreso Ibérico sobre Gestión y Planificación de Aguas, El Agua a Debate desde la universidade, Simposio Gestión de aguas, participación ciudadana y conflictos sociales y de Aguas », Zaragoza, Espagne : France (1998)" #12;2 2 Tous ces conflits se jouent dans le canton de

Paris-Sud XI, Université de

50

Fluvial-deltaic heavy oil reservoir, San Joaquin basin  

Microsoft Academic Search

Unconsolidated arkosic sands deposited in a fluvial-deltaic geologic setting comprise the heavy oil (13\\/degree\\/ API gravity) reservoir at South Belridge field. The field is located along the western side of the San Joaquin basin in Kern County, California. More than 6000 closely spaced and shallow wells are the key to producing the estimated 1 billion bbl of ultimate recoverable oil

D. D. Miller; J. G. McPherson; T. E. Covington

1989-01-01

51

Crosshole Radar Tomography in a Fluvial Aquifer near Boise, Idaho  

Microsoft Academic Search

To determine the distribution of heterogeneities in the saturated zone of an unconfined aquifer in Boise, ID, we compute tomograms for three adjacent well pairs. The fluvial deposits consist of unconsolidated cobbles and sands. We used a curved-ray, finite-difference approximation to the eikonal equation to generate the forward model. The inversion uses a linearized, iterative scheme to determine the slowness

William P. Clement; Warren Barrash

2006-01-01

52

Modeling fluvial erosion on regional to continental scales  

Microsoft Academic Search

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

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

1994-01-01

53

Heavy mineral analyses as a powerful tool in fluvial geomorphology  

NASA Astrophysics Data System (ADS)

The Marneuli depression is a tectonic sub-basin of the Transcaucasian depression in eastern Georgia, filled with several decametres of fluvial, lacustrine and aeolian Quaternary sediments. In order to reconstruct past landscape evolution of the region we studied Late Quaternary fluvial sediments found along several rivers that flow through that depression. Whereas Holocene river sediments could generally easily be assigned to corresponding rivers, this was not always the case for older fluvial sediments. For this reason, we studied the heavy mineral contents of five recent rivers and of four sedimentary deposits of potential precursors. A total of 4088 analysed heavy mineral grains enabled us to set up the characteristic heavy mineral distribution pattern for each sample. Using these data, we were able to reconstruct the most likely source areas of the Late Pleistocene fluvial sediments and to link them with the catchment areas of recent rivers. This allowed us to identify and to substantiate significant Late Quaternary river diversions that could at least partly be assigned to ongoing tectonic processes.

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

2014-05-01

54

Z .Geomorphology 27 1999 4160 Dating fluvial terraces with 10  

E-print Network

. We employ a Z .cosmogenic radionuclide CRN profile technique that addresses a major problem of CRN with the model of terrace­glacial relationship. CRN inheritance is significant and highly variable, requiringMy for the source rocks. Alternatively, assuming the CRNs are inherited during clast transport, the time of fluvial

55

Architectural studies of Jurassic-Cretaceous fluvial units, Colorado Plateau  

SciTech Connect

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

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

1989-03-01

56

Vision for a worldwide fluvial-sediment information network  

USGS Publications Warehouse

The nations of the world suffer both from the deleterious effects of some natural and human-altered fluxes of fluvial sediment and a lack of consistent and reliable information on the temporal and spatial occurrence of fluvial sediments. Decades ago, this difficulty was unavoidable due to a lack of understanding of the magnitude and scope of environmental influences exerted by fluvial sediment coupled with a dearth of tools for monitoring and studying the data. Such is no longer the case. Fluvial sediment has a broad influence on the environment and humanity. Data needs that were once limited primarily to reservoir and channel maintenance now include issues associated with public water supply; contaminated sediment management; productivity of agricultural lands; stream restoration and watershed health; in-stream biotic stability; post-wildfire channel morphology; dam decommissioning, rehabilitation, or removal; and legal requirements for sediment management (Gray and Glysson, 2005). The adverse effects of poorly managed or unmanaged sediment movement related to these and other issues are well-known qualitatively, and in some cases quantitatively. For example, physical, chemical, and biological damages attributable to fluvial sediment in North America alone are now estimated to range between $20 billion and $50 billion annually (Pimental and others, 1995; Osterkamp and others, 1998; 2004). Capabilities for monitoring, analyzing, storing, and sharing fluvial-sediment data have been developed and, in many cases, are sufficiently mature for consideration for global utilization. Hence, there is not only a strong and expanding need for a global effort to gauge and understand fluvial-sediment characteristics and processes better, but the knowledge and tools to achieve these ends are largely available and ready for their applicability to be evaluated. Given the increasing importance of erosion and sediment processes for water-resources management, an International Sedimentation Initiative (ISI, 2007a), under the United Nations Educational, Scientific, and Cultural Organization’s International Hydrologic Programme (IHP, 2007) was adopted in 2004. The ISI, the focus of which is on sustainable water-resources management on the global scale, features six major activities and projects, which are listed as part of the section entitled, “Relation of the WoFSIN concept to the thrusts of the International Sedimentation Initiative,” that precedes the “Conclusions” section of this paper. Based on the need for more, and more consistent and reliable fluvial-sediment information and on the existence of the ISI and other international and national sediment programs, we envision the need for a Worldwide Fluvial Sediment-Information Network (WoFSIN) with a focus on data acquisition, storage, and dissemination globally. Envisioned components of a WoFSIN, administered largely via the Internet and relying mostly on the benefits derived from existing resources and programs, follow that summary. The goal of the WoFSIN is to maximize the availability and usefulness of the world’s historical and current fluvial-sediment and ancillary data through collaboration with existing programs so as to require few additional resources in the long-term. Thus, the WoFSIN concept was developed recognizing that informed resource management is predicated on the availability of adequate and reliable information. The WoFSIN is described in the ensuing sections in stand-alone fashion, followed by a section that describes the complementary aspects of the WoFSIN and the International Sediment Initiative. Thus, our first objective is to describe the fundamental components of a WoFSIN. Our second objective is to identify overlap or gaps between the WoFSIN and ISI concepts that might be useful in refining the ISI’s ability to meet its global mission to develop decision support for sediment management at the global scale more fully, cost-effectively, and (or) with enhanced quality.

Gray, J.R.; Osterkamp, W.R.

2007-01-01

57

The Pliocene and Quaternary fluvial archives of the Rhine system  

NASA Astrophysics Data System (ADS)

The River Rhine is one of the few major fluvial systems that connect the areas of the Alpine glaciers and Scandinavian ice sheet and so provides a key for correlating the two glacial areas in northern and middle Europe. The fluvial sequences of the Rhine Valley include at least 11 Pleistocene terraces in the Lower Rhine area, 2 Pliocene and 12 Pleistocene terraces in the Middle Rhine area resulting in 15 different Pliocene and Pleistocene terraces based on the correlation between Lower and Middle Rhine. The formation of fluvial terraces is significantly influenced by climatic and tectonic processes. The terrace staircases are a result of uplift in the Middle Rhine area and the southern part of the Lower Rhine area, whereas subsidence in the northern part of the Lower Rhine area resulted in buried stacked sequences. Magnetostratigraphic data provide chronological constraints for the terrace deposits in the Lower Rhine embayment and Middle Rhine region. The Matuyama/Brunhes boundary is a reliable marker horizon for the Upper Terrace fluvial deposits exposed in the Kärlich clay pit in the Middle Rhine area. The first appearance of volcanic heavy mineral grains in the terrace sediments, in loess and soils can be correlated from the Middle Rhine area through the Lower Rhine embayment to the Netherlands. The first occurrence of Nordic components in terrace sediments of the Lower Rhine area is known from gravel on top of the Kempen-Krefeld beds and so are younger than the Holsteinian but older than the penultimate glaciation. In the lower Middle Rhine area, 40Ar/ 39Ar dating of tephra layers intercalated in the aeolian and fluvial sediments provide age constraints. The Upper Pleistocene aeolian sediments overlying the terrace deposits have been dated by luminescence methods, and the tephra from the Laacher See eruption (12,860 BP) is present in the Younger Lower Terrace deposits.

Boenigk, Wolfgang; Frechen, Manfred

2006-03-01

58

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

59

Marine to fluvial transition: Proterozoic Upper Rewa Sandstone, Maihar, India  

NASA Astrophysics Data System (ADS)

The Proterozoic Upper Rewa Sandstone in central India, is generally interpreted as entirely marine. A detailed study in Maihar, Madhya Pradesh, however, reveals upward transition from marine to fluvial through a mixed facies association also bearing eolian imprints. Facies associations differ in stratal geometry and arrangement, palaeocurrent direction and pattern as well as in grain size and sorting. The fine-grained marine association is dominated by tidal sheet deposits with characteristic rhythmic changes in thickness and style of cross-stratification and their packages, as well as local evidence of current reversals. Subordinate beach deposits are also present. The major palaeocurrent direction is highly consistent and westward. The coarse-grained, often granule-rich, sandstones of the fluvial association are embodied by four facies correlatable with flow stages and relative bed shear. These braided stream deposits are preserved in vertical stacks of tabular sandbodies in response mainly to basin subsidence. The palaeocurrent pattern is unimodal and northwestward, but its dispersion covers 180°. The rocks are poorly sorted and at places incorporate sand clasts, although they are virtually mud-free and mineralogically mature as in two other associations. The medium- to fine-grained sandstones at the intermediate interval between the marine and fluvial associations are of distinct lensoid geometry. They incorporate representatives from the previous two associations as well as translatent strata, interdune erg deposits and possibly aeolian cross-strata. Consequently the palaeocurrent pattern is polymodal with a spread over 270°. An overall coarsening-up trend in the fluvial part and thinning-up trend in the tidal part imply progradation in spite of evidence of basin subsidence. A high rate of sediment discharge from a perennial river system in a humid climate is suggested.

Bose, Pradip K.; Chakraborty, Partha Pratim

1994-03-01

60

CIENCIA, TECNOLOGA, POLTICA Y PLANIFICACIN DEL AGUA Y DE  

E-print Network

segunda circular enero 2011 CIENCIA, TECNOLOGÍA, POLÍTICA Y PLANIFICACI�N DEL AGUA Y DE LA ENERGÍA EN LOS REGADÍOS. ASPECTOS SOCIOEC�NOMICOS Y AMBIENTALES. AGRICULTURA, AGUA Y ENERGÍA colaboran MADRID varias cuestiones gene- rales que orientan la realización de este Congreso titulado AGRICULTURA, AGUA Y

Escolano, Francisco

61

Una marca de agua inteligente aplicada al dinero electrnico  

E-print Network

Una marca de agua inteligente aplicada al dinero electrónico Patricia Jaimes1*, Gabriel Hermosillo2.hermosillo}@inria.fr Resumen El uso de las marcas de agua se ha incrementado, principal- mente por la necesidad de proteger los manera segura para expandir las aplicaciones actuales de las marcas de agua, dán- doles exibilidad

Boyer, Edmond

62

CONSERVE SU SALUD DURANTE UN DESASTRE Alimentos y agua  

E-print Network

CONSERVE SU SALUD DURANTE UN DESASTRE Alimentos y agua Las situaciones de emergencia pueden afectar para tres días de 1 galon de agua por persona y por día para beber, higiene y cocinar. Mantengase hidratado bebiendo ocho vasos de 8 onzas de agua por día. #12;Los programas educativos de Texas A&M Agri

63

Prehistoric Population and Climate Variation, the Agua Fria Watershed, Arizona  

E-print Network

Prehistoric Population and Climate Variation, the Agua Fria Watershed, Arizona Cara S. Kiggins conditions contribute to the settlement pattern shifts within the Agua Fria watershed in the late AD 1200s Combined Upper Agua Fria · A positive combination is 100 years before the population increase and therefore

Hall, Sharon J.

64

I CONGRESO INTERNACIONAL DEL AGUA .... por la vida  

E-print Network

I CONGRESO INTERNACIONAL DEL AGUA .... por la vida Jueves 09 y viernes 10 de junio de 2005/Ciudad. Temática: Riesgos y agua. Hacia una redefinición del riesgo para una mejor gestión social. Julien Rebotier (IHEAL), Paris 3 ­ Sorbonne Nouvelle. Los riesgos socionaturales y el agua, un enfoque renovado para una

Paris-Sud XI, Université de

65

Does deposition depth control the OSL bleaching of fluvial sediment?  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

66

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

67

How Intensive was Fluvial Erosion during the Martian Noachian?  

NASA Astrophysics Data System (ADS)

The most important process forming the Noachian landscape was impact cratering, but this landscape has been strongly modified by fluvial, igneous, tectonic, and eolian processes. Most of the valley networks on the highlands date to the late Noachian and early Hesperian; many of these, however, appear to have resulted from late-stage incision into earlier, more extensive Noachian basin fills and alluvial fans. The morphology of most degraded highland impact craters less than 200 km in diameter is consistent with infilling by 0.5 to 1 km of fluvial deposits eroded from interior crater walls, presumably by runoff erosion. Evidence for large Noachian lakes on the highlands supports widespread precipitation. These degraded craters are superimposed upon a broader landscape of basins and ridges typically 200+ km in size (e.g., Frey et al., GRL 29(10), 2002). This broadly rolling landscape is best interpreted as being an earliest Noachian cratered landscape smoothed by ejecta deposition from basin scale impacts (e.g., Hellas, Argyre, and Isidis) and possibly pyroclasic airfall deposits. The mantled basins, presumably ancient impact craters, often consist of multiple coalesced impact basins, but they generally lack rims between the constituent impact basins. This pattern suggests that extensive fluvial erosion leading to basin integration occurred even during the earliest Noachian and prior to the basin mantling events.

Howard, A. D.

2002-12-01

68

Problemtica de las aguas cidas en la FPI y monitorizacin del flujo de agua y calor a  

E-print Network

Problem�tica de las aguas �cidas en la FPI y monitorizaci�n del flujo de agua y calor a trav�s de�geno y el agua. � Los residuos de la actividad minera aceleran los procesos de oxidaci�n de sulfuros #12;� Cuando no se dispone de suficientes minerales alcalinos en el medio el agua superficial disminuye su p

Politècnica de Catalunya, Universitat

69

Publicaciones del IGME: serie Hidrogeologa y aguas subterrneas, n 14. VI Simposio del Agua en Andaluca. I: 669-678  

E-print Network

Publicaciones del IGME: serie Hidrogeología y aguas subterráneas, nº 14. VI Simposio del Agua en Andalucía. I: 669-678 Problemática de la calidad de las aguas de la Vega de Granada para el riego del tabaco Castillo Martín, Antonio* y Sánchez Díaz, Luis** * CSIC e Instituto del Agua de la Universidad de Granada

Castillo, Antonio

70

Sensitivity of Weichselian fluvial systems to climate change (Nochten mine, eastern Germany)  

NASA Astrophysics Data System (ADS)

This paper aims to contribute to the understanding of fluvial system response to climate change during the last glacial-interglacial cycle. Fluvial and aeolian successions have been studied in the opencast brown-coal mine Nochten in eastern Germany. An absolute chronology was established by luminescence and 14C-dating, enabling to demonstrate the relations between depositional units and changes in sedimentary environment over time with regional climatic and vegetational changes. It is concluded that the major climatic periods, coinciding with the oxygen isotope stages, are generally reflected in the fluvial sequence by distinct fluvial environments. Major climatic changes (oxygen isotope stage boundaries) have been preserved in the fluvial record as erosional bounding surfaces and by changes in fluvial style. Rapid climate changes like the Middle Pleniglacial Dansgaard-Oeschger cycles are in general not reflected in the fluvial succession. These cycles were too short or with too low amplitude to cause a strong vegetational response and related changes in water and sediment supply. It is emphasized that also the preservation potential of short-lived climatic warming events in 'high-energy' fluvial systems is low. Warming events may, however, have been preserved in lacustrine successions in former thermokarst lakes. A strong cooling event at ca 40 ka, leading to continuous permafrost conditions and changes in the water and sediment budget, was reflected in the fluvial archive by a change from sandy anabranching to braided river conditions.

Kasse, C.; Vandenberghe, J.; Van Huissteden, J.; Bohncke, S. J. P.; Bos, J. A. A.

2003-10-01

71

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

72

Introduction to the special issue on discontinuity of fluvial systems  

NASA Astrophysics Data System (ADS)

Fluvial systems include natural and human-created barriers that modify local base level; as such, these discontinuities alter the longitudinal flux of water and sediment by storing, releasing, or changing the flow path of those materials. Even in the absence of distinct barriers, fluvial systems are typically discontinuous and patchy. The size of fluvial discontinuities ranges across scales from 100 m, such as riffles, to 104 m, such as lava dams or major landslides. The frequency of occurrence appears to be inversely related to size, with creation and failure of the small features, such as beaver dams, occurring on a time scale of 100 to 101 years and a frequency of occurrence at scales as low as 101 m. In contrast, larger scale discontinuities, such as lava dams, can last for time scales up to 105 years and have a frequency of occurrence of approximately 104 m. The heterogeneity generated by features is an essential part of river networks and should be considered as part of river management. Therefore, we suggest that "natural" dams are a useful analog for human dams when evaluating options for river restoration. This collection of papers on the studies of natural dams includes bedrock barriers, log jams and beaver dams. The collection also addresses the discontinuity generated by a floodplain — in the absence of an obvious barrier in the channel — and tools for evaluation of riverbed heterogeneity. It is completed with a study of impact of human dams on floodplain sedimentation. These papers will help geomorphologists and river managers understand the factors that control river heterogeneity across scales and around the world.

Burchsted, Denise; Daniels, Melinda; Wohl, Ellen E.

2014-01-01

73

Listeria monocytogenes aguA1, but Not aguA2, Encodes a Functional Agmatine Deiminase  

PubMed Central

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

2013-01-01

74

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

75

New Mesoscale Fluvial Landscapes - Seismic Geomorphology and Exploration  

NASA Technical Reports Server (NTRS)

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

Wilkinson, M. J.

2013-01-01

76

Behavior and fate of chloronitrobenzenes in a fluvial environment  

SciTech Connect

Studies about the environmental persistence of dangerous chemicals are often very important to evaluate both their toxic actions and bioaccumulation. Several works have been carried out on the occurrence in surface waters of widespread pollutants such as PCBs, PAHs, some herbicides and insecticides. On the other hand, not much attention has been given to many industrial contaminants released into the environment from specific industrial processes. The purpose of this study was to determine concentrations and evolution of chloronitrobenzenes (starting materials for the production of chloroanilines, nitroanilines and nitrophenols) in a fluvial environment; the work was carried out on the Bormida River.

Trova, C.; Cossa, G.; Gandolfo, G. (Lab. di Sanita Pubblica, Alessandria (Italy))

1991-10-01

77

Legitimizing fluvial ecosystems as users of water: an overview.  

PubMed

We suggest that fluvial ecosystems are legitimate users of water and that there are basic ecological principles guiding the maintenance of long-term ecological vitality. This article articulates some fundamental relationships between physical and ecological processes, presents basic principles for maintaining the vitality of fluvial ecosystems, identifies several major scientific challenges and opportunities for effective implementation of the basic ecological principles, and acts as an introduction to three specific articles to follow on biodiversity, biogeochemistry, and riparian communities. All the objectives, by necessity, link climate, land, and fresh water. The basic principles proposed are: (1) the natural flow regime shapes the evolution of aquatic biota and ecological processes, (2) every river has a characteristic flow regime and an associated biotic community, and (3) aquatic ecosystems are topographically unique in occupying the lowest position in the landscape, thereby integrating catchment-scale processes. Scientific challenges for the immediate future relate to quantifying cumulative effects, linking multidisciplinary knowledge and models, and formulating effective monitoring and assessment procedures. Additionally, forecasting the ecological consequences of changing water regimes is a fundamental challenge for science, especially as environmental issues related to fresh waters escalate in the next two to three decades. PMID:12481913

Naiman, Robert J; Bunn, Stuart E; Nilsson, Christer; Petts, Geoff E; Pinay, Gilles; Thompson, Lisa C

2002-10-01

78

Inversion of fluvial channels for paleorock uplift rates in Taiwan  

NASA Astrophysics Data System (ADS)

The transient response of erosion to changes in rock uplift rate leads to the preservation of rock uplift history in the long profiles of rivers. However, extracting this information is nontrivial as changes in channel steepness are the result of both spatial and temporal changes in rock uplift rate, as well as other factors such as climate and rock type. We exploit an analytical linear solution for river channel profile evolution in response to erosion and tectonic uplift to investigate the rock uplift history of Taiwan. The analytical approach allows us to solve the linear inverse problem, efficiently extracting rock uplift as a function of space and time, from digital elevation data. We assess the potential of fluvial topography to resolve rock uplift rates using three approaches: (1) a synthetic resolution test, (2) analysis of the forward model to demonstrate where in space and time the fluvial topography constrains rock uplift rate, and (3) interpretation of the model resolution matrix. Furthermore, the potential to analyze large data sets reduces the influence of stochastic processes such as landslides, small-scale river network reorganization, and also local lithological variability. In Taiwan, our analysis suggests that current rock uplift rates exceed erosion rates across much of the island and that there has been an increase in rock uplift rates since 0.5 Ma across the Central Range.

Fox, Matthew; Goren, Liran; May, Dave A.; Willett, Sean D.

2014-09-01

79

Fluvial erosion of impact craters: Earth and Mars  

NASA Technical Reports Server (NTRS)

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

Baker, V. R.

1984-01-01

80

Fluvial channels on Titan: Initial Cassini RADAR observations  

USGS Publications Warehouse

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

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

2008-01-01

81

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

82

Fluvial ecosystem resilience and stability: the role of riparian vegetation  

NASA Astrophysics Data System (ADS)

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

Corenblit, Dov; Steiger, Johannes

2014-05-01

83

River incision rates and fluvial landform development in the French Western Alps  

Microsoft Academic Search

The processes of fluvial erosion and transport constitute the main controls on continental morphology and sediment flux. A quantification of these processes is therefore essential for our understanding of the interaction between tectonics and long-term landscape development. Studying the development of fluvial form over time may lead to significant progress in our understanding of the dynamics of, and controls on,

G. Brocard; P. van der Beek; D. Bourlès; L. Siame

2003-01-01

84

Notes: Retention of Adaptive Rheotactic Behavior by F1 Fluvial Arctic Grayling  

Microsoft Academic Search

Downstream movements of age-0 Arctic grayling Thymallus arcticus from an indigenous fluvial population (Big Hole River) and two inlet-spawning, lacustrine populations (Upper Red Rock Lake and Ennis Reservoir) were compared in a natural stream. All fish were incubated and reared together in a hatchery and acclimated together in the stream before being released in the stream. All fluvial test fish

Calvin M. Kaya; Eric D. Jeanes

1995-01-01

85

Fluvial features on Titan: Insights from morphology and modeling Devon M. Burr1,  

E-print Network

Fluvial features on Titan: Insights from morphology and modeling Devon M. Burr1, , J. Taylor Perron, Tucson, Arizona 85721-0011, USA ABSTRACT Fluvial features on Titan have been iden- tified in synthetic aperture radar (SAR) data taken during spacecraft flybys by the Cassini Titan Radar Mapper (RADAR

Wang, Xiaorui "Ray"

86

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

87

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

Microsoft Academic Search

Humans have profoundly altered hydrological pathways and fluvial systems through their near-extirpation of native populations of animal species that strongly influenced hydrology and removal of surface sediment, and through the introduction of now-feral populations of animals that bring to bear a suite of different geomorphic effects on the fluvial system. In the category of effects of extirpation, examples are offered

David R. Butler

2006-01-01

88

LOS VERTIDOS DE AGUAS RESIDUALES URBANAS EN ANDALUCIA  

E-print Network

LOS VERTIDOS DE AGUAS RESIDUALES URBANAS EN ANDALUCIA CASTILLO, A.; INCERTI, C. y PICAZO, J. (1991). "Los vertidos de aguas residuales urbanas en Andalucía (1988-89)". Ed. Consejería de Salud (Junta de;CONTENIDO I. Presentación II. Cuadro-síntesis de la situación de vertidos de aguas residuales urbanas en

Castillo, Antonio

89

Tratamiento pasivo de aguas de mina con altas  

E-print Network

Tratamiento pasivo de aguas de mina con altas concentraciones de metales Resultados de ensayos en · Metodología · Resultados · Trabajos pendientes #12;Introducción Problemática de las aguas ácidas de mina 2.5 H2O Faja Pirítica Ibérica: · Mayor reserva de pirita del mundo · Aguas ácidas de mina con

Politècnica de Catalunya, Universitat

90

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

91

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

E-print Network

Click Here for Full Article Inverted fluvial features in the Aeolis/Zephyria Plana region, Mars/Zephyria Plana (AZP) region of Mars has been previously hypothesized to be inverted fluvial features, although infill on Mars, but these criteria are not satisfied by the majority of the AZP fluvial SRs. Armoring

Perfect, Ed

92

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

93

Fluvial sensitivity to Late Quaternary climate changes in NW Romania  

NASA Astrophysics Data System (ADS)

Fluvial archives became increasingly important for the reconstruction of past environments, as they record a sum of climate, vegetation, hydrologic and anthropic changes. This is especially important for the Late Quaternary, when climate and human activities had recorded large spatial and temporal variations. Here we present a tale of fluvial behavior during the last ca. 24.000 years in NW Romania, based on 1) absolute ages and fluvial architecture of sediments exposed in 8 openings located along the Some?u Mic River, and 2) depth-age models, grain size, LOI and gastropods assemblage analysis on 2 cores located upstream from ?tiucilor Lake, a natural lake along a small tributary of the Some?u Mic River, formed by salt disolution on top of a narrow diapiric anticline. During the Late Glacial (LG), ?tiucilor Lake was more extended then is today, with a high input of coarse materials (sands) from the slopes; and dramatically reducing its size in the Early Holocene, a transition marked by the abrupt occurrence of Holocene gyttja on top of LG sands, 1 km upstream from the present lake. Further upstream, at ca. 4 km from the present day edge of the lake, clays and sandy clays were deposited during the Bolling - Allerod (BA), followed by fine - medium sands of Younger Dryas (YD) age. On top of these sands, clays, sandy clays and gyttja occur, suggesting a returning to a less energetic sedimentary environment in the Holocene. In both cores, the sediments become lacustrine, with clays and fine sands, attesting the expansion of the lake's surface, followed by large fluctuations during the Holocene. The river fed by this stream - Some?u Mic, was a coarse gravel, shallow braided river before the Last Glacial Maximum and until the YD. The channel metamorphosis into a narrow, incised, meandering one, occurred ca. 1500 years after the beginning of the Holocene. However, sedimentological evidences suggest that this transition from braided to meandering channel was not a straightforward one, with a phase of few hundred years during the Early Holocene when the river became a slightly incised braided/wandering channel, with finer in-channel materials. The conservative response of Some?u Mic river to the climatic amelioration, without channel type change during the BA and delayed reaction during the Early Holocene, is probably the consequence of the higher general slope of the valley which maintain an increased solid discharge. This threshold is surpassed only in the Holocene, when deciduous forest arrived in the area and imposed a compact belt at mid altitudes, causing a drastic reduction of solid discharge. Contrary, the small tributary seems to be highly responsive to all important climatic changes during the LG and the Holocene. The two cases confirm the variable sensitivity (depending on geologic and hydrologic factors) of fluvial systems to climate changes and highlight the complexity of their temporal and spatial response to these changes.

Per?oiu, Ioana; R?doane, Maria; Robu, Delia; Tan??u, Ioan

2013-04-01

94

Modeling fluvial erosion on regional to continental scales  

NASA Technical Reports Server (NTRS)

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.

1994-01-01

95

Dynamic Flocculation of Muds in Fluvial to Marine Transitions  

NASA Astrophysics Data System (ADS)

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

Keyvani, A.; Strom, K. B.

2012-12-01

96

Fluvial Transport of Gravel in Debris Flow Cut Channels  

NASA Astrophysics Data System (ADS)

In mountainous regions, steep tributary channels are periodically swept by debris flows, which upon arriving at downstream low gradient junctions deposit boulder-rich fans. Little is known about the possible role of fluvial sediment transport between debris flow events in flushing sediment from these tributaries and reworking the fan deposits. In order to test some recent advances in sediment transport theory that may be applicable to such channels, we established five study reaches in tributaries of Elder Creek (South Fork Eel River in Northern California) in channels where field evidence reveals past debris flow activity. The channels have distinct boulder-lined beds with local patches of cobble and gravel. Our goals were to document flows and sediment mobility by size class and location on the bed. We chose five reaches consisting of drainage areas ranging from 0.048 km2 to 2.0 km2 and slopes ranging from 3.5% to 35%. Within each study reach, we painted patches of gravel of varying grain sizes and morphologies, as well as individual boulders of varying sizes and friction angles, and installed water level recorders. Although only modest flows occurred in the winter of 2007-2008, we unexpectedly observed significant bed mobility. Gravel and cobble patches experienced selective transport yet the patch morphology and grain size remained largely unchanged, with mobile painted rocks being replaced with grains of similar or smaller sizes. Sediment as coarse as 250mm moved and some (smaller) sediment traveled as far as 69m downstream. This relatively high mobility of sediment suggests that during the extended periods between debris flows (likely 100's to 1000's of years), much of the arriving sediment in these steep tributary channels is transmitted to the mainstem Elder Creek by fluvial processes. Boulder transport, however, was not observed and seems unlikely, except by local undermining due to progressive upslope migration of sediment steps in more mobile sediment.

Winchell, E.; Scheingross, J.; Dietrich, W. E.; Lamb, M. P.

2008-12-01

97

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

USGS Publications Warehouse

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

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

1985-01-01

98

Fluvial entrainment of low density peat blocks (block carbon)  

NASA Astrophysics Data System (ADS)

In many fluvial environments low density materials are transported in significant quantities and these form an important part of the stream load and /or have a distinct impact on sedimentation in these environments. However, there are significant gaps in understanding of how these materials are entrained and transported by streams and rivers. Eroding upland peatland environments in particular, frequently have fluvial systems in which large eroded peat blocks, often exceeding 1 m in length; form an important component of the stream material flux. Transport of this material is significant in determining rates of erosion but also has important impacts in terms of damage to infrastructure and carbon loss. This paper describes a field experiment designed to establish for the first time the conditions under which large peat blocks (c. > 0.1 m b axis) are initially entrained from a rough gravel bed. The field site is Trout Beck, in the North Pennines, Northern England which is an upland wandering river channel with occasional lateral and mid channel bars. Mean low flow stage is typically 0.2 m but during flood can rapidly rise, in one to two hours, to over 1.5 m. To study peat block entrainment a bespoke data acquisition system consisting of two pressure transducers, four release triggers and time lapse camera was set up. The pressure transducers provided a record of local depth and the release triggers were embedded in peat blocks to record initial motion and arranged on the rough stream bed. The time lapse camera provided verification of timing of block entrainment (during daylight hours) and also provided information on the mechanism of initial movement. Peat blocks were cut from a local source and were equidimensional, ranging in size from 0.1 to 0.7 m. The derived entrainment function is related to a critical depth of entrainment. Results demonstrate that peat blocks are entrained when the local depth approximates the height of the peat block. Blocks frequently shift position prior to entrainment but once entrained are rapidly transported downstream. Because of the rough stream bed local depth, measured on the four sides of the block varies markedly and needs to be considered in developing an appropriate entrainment function and; is useful in explaining initial movement prior to entrainment. In some experiments a small accelerometer (HOBO Pendant G data logger) was used to investigate transport dynamics following entrainment. Further work will seek to improve the entrainment function by extending the size range of tests, developing a shear stress related function and investigating the importance of block shape (rounding) on entrainment.

Warburton, Jeff

2014-05-01

99

Analysis of Ancient Fluvial Patterns on the Surface of Mars  

NASA Technical Reports Server (NTRS)

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

Jethani, Henna; Williams, M. E.

2010-01-01

100

Constraining the average fill densities of Mars' lowlands and fluvial erosion of Titan's polar regions.  

E-print Network

Other than Earth, Mars and Titan are the only bodies in our Solar System where we have observed widespread fluvial activity. In this thesis I present two approaches for constraining the extent of multiple resurfacing ...

Tewelde, Yodit

2013-01-01

101

Numerical modeling of Martian gully sediment transport: Testing the fluvial hypothesis  

E-print Network

the fluvial hypothesis R. A. Parsons1 and F. Nimmo1 Received 29 September 2009; revised 3 December 2009). Citation: Parsons, R. A., and F. Nimmo (2010), Numerical modeling of Martian gully sediment transport

Nimmo, Francis

102

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

E-print Network

spatial extent of beavers, bison, prairie dogs, and grizzly bears. Beavers entrapped hundreds of billions of animals that bring to bear a suite of different geomorphic effects on the fluvial system. In the category

103

Lacustrine and Fluvial Terraces Correlation: A Good Picklock to Disclose the Secrets of Complex Alluvial Systems  

NASA Astrophysics Data System (ADS)

This work presents an example of lacustrine and fluvial terraces correlation, a useful approach for the understanding and reconstruct past changes in landscape evolution not only on Earth but also on Mars.

Rossato, S.; Pajola, M.; Mangili, C.; Baratti, E.; Coradini, M.

2014-07-01

104

Acquisition, 3-D display and interpretation of GPR data in fluvial sedimentology.  

E-print Network

??Alluvial architecture has an inherently three-dimensional character; however, standard methods used within fluvial sedimentology, including ground penetrating radar (GPR) surveys, generally provide only 1-D or… (more)

Zuk, Tomasz

2011-01-01

105

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

NASA Astrophysics Data System (ADS)

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

Burnham, Brian; Hodgetts, David; Redfern, Jonathan

2014-05-01

106

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

Microsoft Academic Search

This study reports the nature and timing of Quaternary fluvial activity in the Fitzroy River basin, which drains a diverse 143,000 km2 area in northeastern Queensland, before discharging into the Great Barrier Reef Marine Park. The catchment consists of an extensive array of channel and floodplain types that we show have undergone large-scale fluvial adjustment in-channel planform, geometry and sinuosity. Optically

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

2011-01-01

107

Equations and their physical interpretation in numerical modeling of heavy metals in fluvial rivers  

Microsoft Academic Search

Based on the previous work on the transport-transformation of heavy metal pollutants in fluvial rivers, this paper presented\\u000a the formulation of a two-dimensional model to describe heavy metal transport-transformation in fluvial rivers by considering\\u000a basic principles of environmental chemistry, hydraulics, mechanics of sediment transport and recent developments along with\\u000a three very simplified test cases. The model consists of water flow

SuiLiang Huang

2010-01-01

108

Contenido del programa de estudios Conceptos generales. Biomolculas. Agua, sus propiedades e interacciones.  

E-print Network

Contenido del programa de estudios Bioquímica Conceptos generales. Biomoléculas. Agua, sus propiedades e interacciones. Hidrofobicidad. Polaridad. Capacidad disolvente del agua. Agua y PH. Constante de disociación del agua y PH. Sistema bicarbonato-ácidocarbónico. Proteínas. Aminoácidos. Características

109

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

SciTech Connect

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

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

1985-01-01

110

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

111

Characteristics and historical development of fluvial sediments in the UAE  

NASA Astrophysics Data System (ADS)

Fluvial deposits in the United Arab Emirates include a wide range of different lithologies and textures ranging from wadi and alluvial fan gravels, sands, silts and clay of different morphology, structures and cementation degree. These deposits represent vital economic, cultural and environmental resources in the UAE. In addition to their direct utilization in the industry as construction materials, agricultural ground and more, they are significant groundwater reservoirs (aquifers) and provide space for landfills and waste disposal. Here we present, field data coupled with geomorphologic observations and Be-10 and C-14 analyses of alluvium wadi deposits and related terraces located in the north and north-eastern parts of the UAE. The study area is strongly affected by the obduction of Oman ophiolite and subsequent tectonic activities during the late Cenozoic times. Deep incised valleys cut through the mountain ranges and deposit a mixture of gravel to clayey sediments that commonly reach a thickness of up to 30 m, but thicker sections were also encountered in scattered places. Alluvial-related terraces are developed inland and along the sea shore where deposition seems to have been interrupted by either riverine or marine peneplaination. In addition to carbonate and ophiolite dominated lithologies in the alluviums, some clay minerals and cementation by gypsum and anhydrites is found. Results of Be-10 and C-14 measurements of the clay-silt matrix and selected carbonates will be presented in relation to dating and paleoclimatic events.

El Saiy, A.

2012-04-01

112

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

113

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

114

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

115

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

NASA Astrophysics Data System (ADS)

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

Johnson, Matthew; Rice, Stephen; Reid, Ian

2010-05-01

116

Sedimentology: general introduction and definitions : fluvial sediment and channel morphology  

USGS Publications Warehouse

Sedimentology, the study of sedimentary rocks and the processes by which they are formed, includes and is related to a large number of phenomena. Sedimentology includes the five fundamental processes defined by the term sediaentation --weathering, erosion, transportation, deposition and diagenesis. Sedimentology shares with geomorphology the study of the surface features of the earth. Sedimentology also shares with hydrology the study of river.--channels. River channels are formed in part or in total as a result of flowing water and sediment transport, commonly called the "work of the rivers." This survey of published literature was made to aid in arriving at definitions which would be acceptable to, and representative of, a majority of professional personnel actively engaged in laboratory and field investigations related to the "work of the river." The definitions in this list are intended to explain the terms used in studies of fluvial sediment and channel morphology. No set of definitions can expect universal acceptance, however, i t is hoped that this compilation will be considered a summary and synthesis of present and past usage and that it will serve as a starting point for future usage. Multiple references are cited from textbooks, glossaries and dictionaries, scientific journals and u.s. Government publications. To obtain a mutual understanding and enhance precision, many of the proposed definitions are a composite of those selected from papers or reports covering research studies and field investigations. A draft of this glossary has been reviewed by a group of interested personnel. The results of this review have been carefully considered and the originally-suggested definitions have been revised accordingly, resulting in the present compilation. R. G. Wolff, with the help of Mrs. v. Blatcher, carried out the literature search and compilation of terms and the review results. Paul c. Benedict approved or composed the definitions as presented in this report.

Wolff, Roger G.; Benedict, Paul C.

1964-01-01

117

Marine intervals in Neogene fluvial deposits of western Amazonia  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

118

Publicaciones del IGME: serie Hidrogeologa y aguas subterrneas, n 14. VI Simposio del Agua en Andaluca. I: 619-628. 2005  

E-print Network

Publicaciones del IGME: serie Hidrogeología y aguas subterráneas, nº 14. VI Simposio del Agua en) , Benavente Herrera, José(2) e Hidalgo Estévez, Mª del Carmen(3) (1) CSIC e Instituto del Agua (Univ. Granada). C/ Ramón y Cajal, 4. 18071Granada. Correo electrónico: acastill@ugr.es (2) Instituto del Agua (Univ

Castillo, Antonio

119

Publicaciones del IGME: serie Hidrogeologa y aguas subterrneas, n 14. VI Simposio del Agua en Andaluca. II: 1.237-1.245  

E-print Network

Publicaciones del IGME: serie Hidrogeología y aguas subterráneas, nº 14. VI Simposio del Agua en Andalucía. II: 1.237-1.245 Calidad general de las aguas de la Vega de Granada. Análisis comparativo de las aguas superficiales, subterráneas y residuales Sánchez Díaz, Luis* y Castillo Martín, Antonio

Castillo, Antonio

120

Publicaciones del IGME: serie Hidrogeologa y aguas subterrneas, n 14. VI Simposio del Agua en Andaluca. II: 1.229-1.236. 2005  

E-print Network

Publicaciones del IGME: serie Hidrogeología y aguas subterráneas, nº 14. VI Simposio del Agua en Andalucía. II: 1.229-1.236. 2005 Sobre la calidad físico-química de las aguas superficiales del área metropolitana de Granada Sánchez Díaz, Luis* y Castillo Martín, Antonio** * Instituto del Agua. Universidad de

Castillo, Antonio

121

Economas de escala en agua y saneamiento: examen de la literatura 1 Economas de escala en agua y saneamiento: examen de la literatura1  

E-print Network

Economías de escala en agua y saneamiento: examen de la literatura 1 Economías de escala en agua y relevar la literatura internacional sobre economías de escala en el sector de agua y saneamiento aprovechar economías de escala al dimensionar la prestación de agua potable y alcantarillado. La discusión

Boyer, Edmond

122

Las aguas de Sierra Nevada. A. Castillo (1993) 1 Captulo de libro publicado en: "Aguas de Sierra Nevada". E. Ed. EMASAGRA. ISBN: 84-604-  

E-print Network

Las aguas de Sierra Nevada. A. Castillo (1993) 1 Capítulo de libro publicado en: "Aguas de Sierra Nevada". E. Ed. EMASAGRA. ISBN: 84-604- 8103-4, 185-252. 1993 LAS AGUAS DE SIERRA NEVADA por el Dr. Antonio Castillo Martín Hidrogeólogo del Instituto Andaluz de Geología (CSIC-Univ. Granada) #12;Las aguas

Castillo, Antonio

123

Sequence stratigraphic architecture of a differentially subsiding bay to fluvial basin: the Eocene Ishikari Group, Ishikari Coal Field, Hokkaido, Japan  

Microsoft Academic Search

The Eocene Ishikari Group, deposited in a bay to fluvial basin in central Hokkaido, Japan, provides important information on fluvial sequence stratigraphy in a differentially subsiding ocean-connected setting. The Ishikari Group consists of four million-year-order depositional sequences (Isk-1, Isk-2, Isk-3 and Isk-4), composed mainly of meandering\\/braided fluvial systems. Each depositional sequence contains marine or lacustrine incursion beds, which show lake

Osamu Takano; Amane Waseda

2003-01-01

124

AguaClara: Preparing for Multidimensional Scale-up The AguaClara program is using a novel approach to develop and disseminate sustainable  

E-print Network

approach to develop and disseminate sustainable water treatment technologies. The approach incorporates,000 people with drinking water. · The AguaClara program is much more than engineering. Agua program. Cornell designed AguaClara municipal water treatment plants in Honduras are providing over 13

Angenent, Lars T.

125

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

126

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

SciTech Connect

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

Foster, G.D.; Lippa, K.A. [George Mason Univ., Fairfax, VA (United States). Dept. of Chemistry

1994-12-31

127

Climate-induced fluvial dynamics in tropical Africa around the last glacial maximum?  

NASA Astrophysics Data System (ADS)

The alluvia of the Ntem, Nyong and Sanaga fluvial systems in southern Cameroon recorded repeated fluvial activity fluctuations during the Late Pleistocene, including the last glacial maximum (LGM), the beginning of the African Humid Period and the northern hemispheric Bølling-Allerød. We applied a multi-proxy approach on alluvial stratigraphies dated between 22.4 and 13.0 cal ka BP, including remote sensing, sedimentological and morphogenetic methods, phytoliths, sponge spicules, 14C and ? 13C data. A distinct NE-SW gradient of landscape and fluvial dynamics around the LGM can be drawn, with evidence for the persistence of extended fluvial rainforest refuges only in the Ntem catchment. The Sanaga and Nyong catchment areas were characterized by frequent channel migrations, floodplain reorganization and unstable vegetation subject to fire, including grasslands, woodlands, and gallery forests with bamboo thickets. In spite of increasing rainfall after 16.4 cal ka BP, persisting landscape instability played the major role for fluvial system dynamics, floodplain transformations and vegetation development until 13.0 cal ka BP, before a general landscape stabilization and rainforest expansion set in at the beginning of the Holocene.

Sangen, Mark; Neumann, Katharina; Eisenberg, Joachim

2011-11-01

128

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

USGS Publications Warehouse

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

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

2011-01-01

129

Climate and the erosional efficiency of fluvial systems  

NASA Astrophysics Data System (ADS)

Climate is a key driver of surface processes on Earth. Nevertheless, quantifying the climatic control on erosion rates over mountain building timescales has proven to be a difficult problem to untangle. In fact, some recent attempts to address this problem using cosmogenic radionuclide-derived erosion rates suggest very little climatic control on erosion. If this result is robust, it would have serious implications on proposed feedbacks among climate and tectonics. Here, we address two factors that may be confounding detection of climatic controls on erosion rates: (1) difficulty isolating climate from other variables in natural settings (i.e. topography, rock strength); (2) choosing appropriate climate metrics for comparison (e.g. temperature, precipitation, runoff, variability). A recent study in the San Gabriel Mountains, CA (SGM) provides a template to account for the first-order, topographic control on erosion by measuring millennial-scale erosion rates (10Be in river sands) across a gradient in relief. Building off of this work, we report new data for two other landscapes, Sierra San Pedro Mártir, MX (SSPM) and Sierra Nombre de Dios, HN (SNdD), that show similar gradients of relief and similar lithologies (granitoids), but that lie in dramatically different climate regimes (desert to rainforest). By comparing the functional relationship between relief and erosion, we are able to quantify differences in erosional efficiency due to climate. By re-casting the question in terms of how climate controls erosional efficiency, we can also better evaluate our choice of appropriate climate metrics for comparison among landscapes. For instance, theory suggests that discharge variability may rival the importance of annual climate normals (e.g. mean annual precipitation, mean annual temperature) in setting erosional efficiency by affecting the distribution of extreme events. This requires the use of more sophisticated stream erosion models that account for at least the stochastic distribution of discharge events and thresholds of erosion. Stream gauges with long instrumental records provide the best observations to calibrate these models. However, not all parts of the Earth are sufficiently gauged for this approach. Instead, other atmospheric data products, like the North American Regional Analysis (NARR), can be used to provide more uniform spatial and temporal coverage and generate outputs comparable to fluvial discharge. Specifically, we evaluate the utility of NARR for assessing discharge variability in: the semi-arid SGM; the arid SSPM; the very wet SNdD. Since hydrological and meteorological data are more widely available for SGM, we use that site to calibrate our NARR interpretations for the other locations. The results of this analysis are used to refine stream erosion model predictions of erosional efficiency for all three sites that are then compared to field observations.

Rossi, M. W.; Whipple, K. X.; Dibiase, R. A.; Heimsath, A. M.

2010-12-01

130

Neotectonics and fluvial geomorphology of the Northern Sinai Peninsula  

NASA Astrophysics Data System (ADS)

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

Kusky, T.; El-Baz, F.

2000-08-01

131

Biomarkers in Transit Reveal the Nature of Fluvial Integration  

NASA Astrophysics Data System (ADS)

The carbon and hydrogen isotopic composition of vascular plant leaf waxes are common proxies for hydrologic and vegetation change. Sedimentary archives off major river systems are prime targets for continental paleoclimate studies under the assumption that rivers integrate changes in terrestrial organic carbon (OC) composition over their drainage basin. However, the proportional contribution of sources within the basin (e.g. head waters vs. floodplain) and the transit times of OC through the fluvial system remain largely unknown. This lack of quantifiable information about the proportions and timescales of integration within large catchments poses a challenge for paleoclimate reconstructions. To examine the sources of terrestrial OC eroded and supplied to a river system and the spatial distribution of these sources, we use compound specific isotope analysis (i.e. ?13C, ?14C, and ?D) on plant-derived leaf waxes, filtered from large volumes of river water (20-200L) along a major river system. We selected the Kosñipata River that drains the western flank of the Andes in Peru, joins the Madre de Dios River across the Amazonian floodplain, and ultimately contributes to the Amazon River. Our study encompassed an elevation gradient of >4 km, in an almost entirely forested catchment. Precipitation ?D values vary by >50‰ due to the isotopic effect of elevation, a feature we exploit to identify the sources of plant wax n-alkanoic acids transported by the river. We used the ?D plant wax values from tributary rivers as source constrains and the main stem values as the integrated signal. In addition, compound specific radiocarbon on individual chain length n-alkanoic acids provide unprecedented detail on the integrated age of these compounds. Preliminary results have established that 1) most of the OC transport occurs in the wet season; 2) total carbon transport in the Madre de Dios is dominated by lowland sources because of the large floodplain area, but initial data suggest that OC from high elevations may be proportionally overrepresented relative to areal extent, with possibly important implications for biomarker isotope composition; 3) timescales of different biomarkers vary considerably; 4) the composition of OC varies downstream and with depth stratification within large rivers. We filtered >1000L of river water in this remote location during the wet season, and are presently replicating that study during the dry season, providing a seasonal comparison of OC transport in this major river system.

Ponton, C.; West, A.; Feakins, S. J.; Galy, V.

2013-12-01

132

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

NASA Astrophysics Data System (ADS)

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

Breinl, Korbinian

2014-05-01

133

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

134

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

135

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

136

Testing fluvial erosion models using the transient response of bedrock rivers to tectonic forcing in the Apennines, Italy  

E-print Network

Testing fluvial erosion models using the transient response of bedrock rivers to tectonic forcing fluvial erosion models. However, some recent studies of bedrock erosion conclude that transient river long profiles can be approximately characterized by a transportlimited erosion model, while other authors

Cowie, Patience

137

K-AR DATING OF AUTHIGENIC ILLITES: INTEGRATING THE DIAGENETIC HISTORY OF THE FLUVIAL WILLIAMS FORK FORMATION, MESAVERDE  

E-print Network

K-AR DATING OF AUTHIGENIC ILLITES: INTEGRATING THE DIAGENETIC HISTORY OF THE FLUVIAL WILLIAMS FORK alteration and illitization in the fluvial section of the Williams Fork Formation (Upper Mesaverde), Piceance). Illite from the extracted clays provide K-Ar ages for fifteen samples, revealing a linear increase in age

138

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

Microsoft Academic Search

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

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

2006-01-01

139

Factors controlling the fluvial export of large woody debris, and its contribution to organic carbon budgets at watershed scales  

Microsoft Academic Search

The fluvial export of large woody debris (LWD) was monitored in 131 reservoirs throughout Japan. Published data on the fluvial export of dissolved and particulate organic carbon were used to estimate the contributions of LWD in carbon budgets. Of all variables tested, watershed area was most important in explaining LWD carbon (LWDC) export, followed by annual precipitation. LWDC export per

Jung Il Seo; Futoshi Nakamura; Daisuke Nakano; Hidetaka Ichiyanagi; Kun Woo Chun

2008-01-01

140

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

NASA Astrophysics Data System (ADS)

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

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

2007-09-01

141

-1 -jorgemercau@gmail.com gea.unsl.edu.ar Integrando al agua en las decisiones  

E-print Network

- 1 -jorgemercau@gmail.com gea.unsl.edu.ar Integrando al agua en las decisiones Producción y D E F M A M mm/mes Pp Etp ... ¿Cuándo siembro? Rendimiento potencial Oferta vs Demanda ¿Cuanta agua ? ... como me afecta la estación? ... como cambia la demanda de agua? ... como cambia oferta y acceso al agua

Nacional de San Luis, Universidad

142

La economa del agua de riego Jos A. Gmez-Limn  

E-print Network

#12;La economía del agua de riego en España José A. Gómez-Limón Javier Calatrava Alberto Garrido Caja Rural, Sociedad Cooperatica de Crédito. La economía del agua de riego en España Todos los derechos Directiva Marco de Agua: ¿Un modelo alternativo del uso del agua? Llorenç Avellà, José Carles y Carles

Oñate, Juan J.

143

Al tratamiento del agua potable para mejo-rar su sanidad o calidad bacteriolgica se  

E-print Network

Al tratamiento del agua potable para mejo- rar su sanidad o calidad bacteriológica se le refiere desinfección usado por los proveedores locales para disminuir la contami- nación bacteriológica del agua. Este método tam- bién puede ser usado por los propietarios de pozos de agua particulares. Pozos de agua Los

144

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

SciTech Connect

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

Zhao Hanqing; Fu Zhiguo; Lu Xiaoguang [Institute of Petroleum Exploration and Development, Daqing (China)

1997-08-01

145

Stratal Architecture of an Early Eocene Fluvial-Lacustrine Depositional System, Little Muddy Creek Area,  

E-print Network

Stratal Architecture of an Early Eocene Fluvial-Lacustrine Depositional System, Little Muddy Creek Area, Southwestern Green River Basin, Wyoming JOHN-PAUL ZONNEVELD1,WILLIAM S. BARTELS2 , AND WILLIAM C.clyde@unh.edu 253 ABSTRACT The Paleogene sedimentary record of the Green River Basin, Wyoming was largely controlled

Licciardi, Joseph M.

146

Effects of Zinc and Lead Mining on the Benthic Macroinvertebrates of a Fluvial Ecosystem  

Microsoft Academic Search

We studied the environmental effects of the mining activity of Troya Mine on the fluvial ecosystem, in the Basque Country, Spain, from 1993 to 1995. The multivariate analysis of the physicochemical conditions shows that the main abiotic factors of variation are: (i) in the water column, a significant increase in the content of heavy metals and conductivity, and (ii) an

M. J. Marqués; E. Martínez-Conde; J. V. Rovira

2003-01-01

147

Fluvial Geomorphology of the Upper Yellowstone River Drainage Basin: Using Google Earth to Analyze Rivers  

NSDL National Science Digital Library

Students load a topographic overlay into Google Earth. Rather than working with paper maps they will learn to make observations and collect data directly from digital maps, in this case while learning about fluvial systems. The lab is designed to introduce student to the power and usefulness of freely available software and data found on the internet. Designed for a geomorphology course

Hanson, Lindley

148

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

149

A mass-balance framework for quantifying downstream changes in fluvial architecture  

E-print Network

A mass-balance framework for quantifying downstream changes in fluvial architecture NIKKI STRONG measured sections into this `mass balance' coordinate system removes much, although not all, of the observed variability in channel stacking density and grain size. Furthermore, removal of the dominant mass

Paola, Chris

150

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

Microsoft Academic Search

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

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

2008-01-01

151

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

Microsoft Academic Search

Geomorphological and palaeoenvironmental research on Holocene sedimentation in the Mue valley provides evidence for fluvial system changes related to climate and human activities in Normandy, a poorly studied area of the Paris basin. The 24-km long valley bottom has been investigated through a systematic survey. It shows an original longitudinal sedimentary pattern in relation with valley morphology and local geological

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

2008-01-01

152

Sheetflow fluvial processes in a rapidly subsiding basin, Altiplano plateau, Bolivia  

E-print Network

Sheetflow fluvial processes in a rapidly subsiding basin, Altiplano plateau, Bolivia BRIAN A. HAMPTON* and BRIAN K. HORTON *Department of Geological Sciences, Michigan State University, East Lansing, MI 48824­1115, USA1 Department of Geological Sciences and Institute for Geophysics, Jackson School

Horton, Brian K.

153

Fluvial incision and tectonic uplift across the Himalayas of central Nepal  

Microsoft Academic Search

The pattern of fluvial incision across the Himalayas of central Nepal is estimated from the distribution of Holocene and Pleistocene terraces and from the geometry of modern channels along major rivers draining across the range. The terraces provide good constraints on incision rates across the Himalayan frontal folds (Sub-Himalaya or Siwaliks Hills) where rivers are forced to cut down into

J. Lavband; J. P. Avouac

2001-01-01

154

Active folding of fluvial terraces across the Siwaliks Hills, Himalayas of central Nepal  

Microsoft Academic Search

We analyze geomorphic evidence of recent crustal deformation in the sub-Himalaya of central Nepal, south of the Kathmandu Basin. The Main Frontal Thrust fault (MFT), which marks the southern edge of the sub-Himalayan fold belt, is the only active structure in that area. Active fault bend folding at the MFT is quantified from structural geology and fluvial terraces along the

J. Lavé; J. P. Avouac

2000-01-01

155

Active folding of fluvial terraces across the Siwaliks Hills, Himalayas of central Nepal  

E-print Network

Active folding of fluvial terraces across the Siwaliks Hills, Himalayas of central Nepal J. Lave´1 of central Nepal, south of the Kathmandu Basin. The Main Frontal Thrust fault (MFT), which marks the southern analysis, complemented by geological investiga- tions in central Nepal. Active deformation in the Himalaya

Avouac, Jean-Philippe

156

Fluvial response a decade after wildfire in the northern Yellowstone ecosystem: a spatially explicit analysis  

E-print Network

, Bozeman, MT 59717-3490, USA c Department of Geography, Southwest Texas State University, San Marcos, TX between fire and fluvial processes. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Fire matter D 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0169-555X(02)00332-X

Lawrence, Rick L.

157

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

NASA Technical Reports Server (NTRS)

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

Blaney, D. L.

2002-01-01

158

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

159

Simulación multicriterio de mercados de agua de regadío: el caso de la cuenca del Duero (*)  

Microsoft Academic Search

1. OBJETIVOS Buena parte de España se encuentra ya en una situación de «econo- mía madura del agua» (Randall, 1981), caracterizada por una deman- da alta y creciente de agua, una oferta inelástica del recurso a largo plazo, un elevado gasto presupuestario para el mantenimiento de las infraestructuras hidráulicas, una intensa competencia por el agua entre los distintos usos, un

YOLANDA MARTÍNEZ MARTÍNEZ; JOSÉ A. GÓMEZ-LIMÓN RODRÍGUEZ

2004-01-01

160

Legacies on the Landscape: Integrating Ecology and Archaeology on the Agua Fria National Monument, Arizona.  

E-print Network

Legacies on the Landscape: Integrating Ecology and Archaeology on the Agua Fria National Monument Distribution: Influences on Plant Communities Prehistoric Population Dynamics Study Area The Agua Fria National human land use in the desert grassland environment of the Agua Fria National Monument, north of Phoenix

Hall, Sharon J.

161

Mster en Ingeniera de los Materiales, Agua y Terreno Objetivos Generales  

E-print Network

Máster en Ingeniería de los Materiales, Agua y Terreno Objetivos Generales Este Máster tiene como los Materiales, Agua y Terreno también se puede cursar a tiempo parcial La matrícula a tiempo parcial Ingeniería de los Materiales, Agua y Terreno #12;

Escolano, Francisco

162

Quercus 201 Noviembre 2002 / 39 agua como las copas de los  

E-print Network

S Quercus 201 Noviembre 2002 / 39 agua como las copas de los bosques tropicales, caso de algunos géneros de driópi- dos. Otras han ocupado las aguas freáticas o intersticia- les y muestran todas las mediterránea, y otros ambientes, como las aguas continentales, también pueden ser extraordinariamente ricos (1

Murcia, Universidad de

163

FUNDAMENTACIN La natacin es la habilidad que permite al ser humano desplazarse en el agua,  

E-print Network

agua, gracias a la acción propulsora realizada por los movimientos rítmicos, repetitivos y coordinados vencer la resistencia que ofrece el agua para desplazarse en ella. Debido a que los seres humanos animales terrestres que se dan impulso en el agua, en lo que constituye en esencia una forma de caminar, el

Escolano, Francisco

164

Senderos Geo-Arqueolgicos, 7 (2010) Geologa, aguas, romanos y romnico  

E-print Network

Senderos Geo-Arqueológicos, 7 (2010) Geología, aguas, romanos y románico de Tierra de Campos Roca #12;Senderos Geo-Arqueológicos, 7 (2010) Geología, aguas, romanos y románico en Tierra de Campos agua caudalosos que provenientes de la Cordillera Cantábrica, con sus importantes precipitaciones

Fitze, Patrick

165

Environmental changes in the central Po Plain (northern Italy) due to fluvial modifications and anthropogenic activities  

NASA Astrophysics Data System (ADS)

The fluvial environment of the central Po Plain, the largest plain in Italy, is discussed in this paper. Bounded by the mountain chains of the Alps and the Apennines, this plain is a link between the Mediterranean environment and the cultural and continental influences of both western and eastern Europe. In the past decades, economic development has been responsible for many changes in the fluvial environment of the area. This paper discusses the changes in fluvial dynamics that started from Late Pleistocene and Early Holocene due to distinct climatic changes. The discussion is based on geomorphological, pedological, and archaeological evidences and radiocarbon dating. In the northern foothills, Late Pleistocene palaeochannels indicate several cases of underfit streams among the northern tributaries of the River Po. On the other hand, on the southern side of the Po Plain, no geomorphological evidence of similar discharge reduction has been found. Here, stratigraphic sections, together with archaeological remains buried under the fluvial deposits, show a reduction in the size of fluvial sediments after the 10th millennium BC. During the Holocene, fluvial sedimentation became finer, and was characterised by minor fluctuations in the rate of deposition, probably related to short and less intense climatic fluctuations. Given the high rate of population growth and the development of human activities since the Neolithic Age, human influence on fluvial dynamics, especially since the Roman Age, prevailed over other factors (i.e., climate, tectonics, vegetation, etc.). During the Holocene, the most important changes in the Po Plain were not modifications in water discharge but in sediment. From the 1st to 3rd Century AD, land grants to war veterans caused almost complete deforestation, generalised soil erosion, and maximum progradation of the River Po delta. At present, land abandonment in the mountainous region has led to reafforestation. Artificial channel control in the mountain sector of the basins and in-channel gravel extraction (now illegal but very intense in the 1960s and 1970s) are causing erosion along the rivers and along large sectors of the Adriatic coast. These changes are comparable with those occurring in basins of other Mediterranean rivers.

Marchetti, Mauro

2002-05-01

166

Evolution of fluvial style in the Siwalik Group in the foothills of the Nepal Himalaya  

NASA Astrophysics Data System (ADS)

Middle Miocene to Pleistocene fluvial sediments of the Siwalik (Churia) Group are widely distributed in the southern frontal area of the Himalaya. The succession is about 6 km thick, and was derived from denudation of the Himalayan orogen. The Siwalik Group in Nepal is well exposed in the Surai Khola area (western Nepal), and the Hetauda-Bakiya Khola area (central Nepal). The group is separated into northern and southern belts by the Central Churia Thrust (CCT). Eight facies associations (FA1 to FA8) are recognized in the Siwalik Group in these areas. They are interpreted as the deposits of fine-grained meandering, flood-flow-dominated fine-grained meandering, sandy meandering, deep sandy braided, comparatively shallow sandy braided, anastomosed, gravelly braided, and debris-flow-dominated braided systems, respectively. FA6, FA7 and FA8 occur only in the southern belt. In each area, the sedimentary succession generally coarsens upwards. The accumulation of these facies associations, related to the paleomagnetic time frame, indicates that flooding increased dramatically from about 10.5 to 9.5 Ma, and fluvial style changed from meandering to braided between 9.0 and 6.5 Ma. A gravelly fluvial system prevailed after 3.0 to 2.5 Ma. The evolution of these fluvial styles is intimately related to the uplift of the Himalaya and associated thrust movements, and consequent effects on atmospheric circulation and precipitation. By comparison with the characteristics of the submarine Bengal Fan deposits, it is apparent that an increase in flood flow is strongly influenced by increased precipitation due to onset and intensification of monsoon climate. The sandy braided system was mainly induced by regional tectonic uplift, and the gravelly fluvial system may have been formed due to regional thrust movements along the Himalaya frontal area.

Nakayama, Katsuhiro; Ulak, Prakash D.

1999-05-01

167

Sequence stratigraphy of the Koonap and Middleton fluvial formations in the Karoo foredeep South Africa  

NASA Astrophysics Data System (ADS)

The Koonap and Middleton formations build a fully fluvial succession of late Permian age which accumulated in the foredeep of the Karoo Basin during the overfilled phase of the foreland system. Fluvial aggradation took place after the final retreat of the Ecca seaway from the limits of the Karoo foredeep, which is why this paper provides a case study for accommodation and sequence development controlled by tectonic mechanisms. The Koonap-Middleton stratigraphy consists of a succession of eight third-order fluvial sequences separated by subaerial unconformities. They formed in isolation from eustatic influences, with a timing controlled by orogenic cycles of loading and unloading. Sediment accumulation took place during stages of flexural subsidence, whereas the bounding surfaces are related to stages of isostatic uplift. The vertical profile of all sequences displays an overall fining-upward trend related to the gradual decrease in topographic slope during orogenic loading. At the same time, an upward change in fluvial styles can be observed within each sequence, from initial higher to final lower-energy systems. The actual fluvial styles in each location depend on paleoslope gradients and the position of the stratigraphic section relative to the orogenic front. Proximal sequences show transitions from braided to meandering systems, whereas more distal sequences show changes from sand-bed to fine-grained meandering systems. The average duration of the stratigraphic cycles is 0.6 My, i.e., eight cycles during 5 My. No climatic fluctuations are recorded during this time, with the long-term climatic background represented by temperate to humid conditions.

Catuneanu, Octavian; Bowker, Duncan

2001-08-01

168

Desarrollo y AplicaciDesarrollo y Aplicacin de unn de un ndice de Calidad de Agua parandice de Calidad de Agua para  

E-print Network

Desarrollo y AplicaciDesarrollo y Aplicacióón de unn de un ÍÍndice de Calidad de Agua parandice de Calidad de Agua para RRííos en Puerto Ricoos en Puerto Rico Jorge Rivera Santos,Jorge Rivera Santos, Ph.DPh.D.,., P.EP.E.. DirectorDirector Instituto de Investigaciones Sobre Recursos de Agua y elInstituto de

Gilbes, Fernando

169

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

NASA Astrophysics Data System (ADS)

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

Beylich, A.; Laute, K.

2013-12-01

170

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

171

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

172

Uso del Los SIG en ModelosUso del Los SIG en ModelosUso del Los SIG en Modelos Hidrolgicos y de Calida de Agua  

E-print Network

Calida de Agua Uso del Los SIG en Modelos Hidrol�gicos y de Calida de Agua (Caso de Uso Cuenca del Ri Luis R. P�rez-Alegr�a PhD P.E.Luis R. P�rez-Alegr�a PhD P.E. #12;Usos del AguaUsos del AguaUsos del AguaUsos del Agua Navegaci�n Consumo Humano HigieneHigiene PescaRecreaci�n #12;Calidad del Agua

Gilbes, Fernando

173

Controls on large-scale patterns of fluvial sandbody distribution in alluvial to coastal plain strata: Upper Cretaceous Blackhawk  

E-print Network

Blackhawk Formation. Laterally extensive coal zones formed on the coastal plain during shallow- marine strata: Upper Cretaceous Blackhawk Formation, Wasatch Plateau, Central Utah, USA GARY J. HAMPSON*, M belt (Upper Cretaceous Blackhawk Formation, central Utah, USA). Many channelized fluvial sandbodies

Kulp, Mark

174

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

175

Summary of U.S. Geological Survey on-line instantaneous fluvial sediment and ancillary data  

USGS Publications Warehouse

Instantaneous fluvial sediment data, in addition to other instantaneous water-quality and ancillary data collected by the U.S. Geological Survey (USGS), are available on-line through the National Water Information System World Wide Web (NWISWeb) water-quality data base at http://waterdata.usgs.gov/nwis/qwdata. The NWISWeb water-quality data base was populated and is periodically refreshed from electronic files maintained by individual USGS District offices across the United States and Puerto Rico. It represents the single largest repository of USGS electronic instantaneous-value suspended-sediment, bedload, and bed-material data. These Web pages provide a summary of fluvial-sediment data by State, and by USGS station number retrieved from the then-under-construction NWISWeb data base on January 13, 2000. The meta data can be accessed by following the links at the bottom of this Web page.

Turcios, Lisa M.; Gray, John R.; Ledford, Annette L.

2000-01-01

176

Evolution of fluvial drainage networks evolving in response to an emerging Cenozoic Panama Cordillera  

NASA Astrophysics Data System (ADS)

We use correlations of Early Miocene to Pliocene fluvial stratigraphic, paleocurrent, and provenance data from across Panama to reconstruct the evolution of fluvial drainage networks evolving in response to the emerging Cenozoic Panama Cordillera. Late Miocene Panama is generally thought to have been comprised of a volcanic arc archipelago that by the end of the Miocene had merged into a single land mass. Yet the timing of, the exact location, and manner in which the Isthmus of Panama emerged and eventually closed is poorly constrained. We use this paleodrainage network data set coupled with preliminary constraints on the extent and timing of magmatic events and structural deformation to better constrain the paleogeographic evolution of the Isthmus of Panama within a Caribbean tectonic framework.

Strong, N.; Farris, D.; Cardona, A.; Monte, C.; O'Dea, A.; Jaramillo, C.

2008-12-01

177

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

PubMed

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

Chen, A S; Djordjevi?, S; Leandro, J; Savi?, D A

2010-01-01

178

Extraction of fluvial networks in lidar data using marked point processes  

NASA Astrophysics Data System (ADS)

We propose a method for the automatic extraction of fluvial networks in lidar data with the aim to obtain a connected network represented by the fluvial channels' skeleton. For that purpose we develop a two-step approach. First, we fit rectangles to the data using a stochastic optimization based on a Reversible Jump Markov Chain Monte Carlo (RJMCMC) sampler and simulated annealing. High gradients on the rectangles' border and non-overlapping areas of the objects are introduced as model in the optimization process. In a second step, we determine the principal axes of the rectangles and their intersection points. Based on this a network graph is constructed in which nodes represent junction points or end points, respectively, and edges in-between straight line segments. We evaluate our method on lidar data with a tidal channel network and show some preliminary results.

Schmidt, A.; Rottensteiner, F.; Soergel, U.; Heipke, C.

2014-08-01

179

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

NASA Astrophysics Data System (ADS)

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

Langhammer, Jakub; Mi?ijovský, Jakub; Hartvich, Filip; Kaiglová, Jana

2014-05-01

180

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

NASA Technical Reports Server (NTRS)

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

Rosenshein, E. B.

2003-01-01

181

Case study of a stimulation experiment in a fluvial, tight-sandstone gas reservoir  

SciTech Connect

This paper reports that a successful stimulation experiment was conducted in a fluvial sandstone of the Mesaverde formation at the U.S. DOE's Multiwell Experiment (MWX) Site in the Piceance basin of Colorado. The stimulation experiment consisted of stress tests, a three-well prefracture interference test, step-rate/flowback tests, a minifracture, a full stimulation treatment borehole geophone diagnostics during fracturing, and a postfracture interference test.

Warpinski, N.R.; Sattler, R.; Thorne, B.J.; Lorenz, J.C. (Sandia National Labs., Albuquerque, NM (USA)); Branagan, P.T.; Cipolla, C.L. (CER Corp., Las Vegas, NV (USA))

1990-11-01

182

The resazurin-resorufin tracer for quantifying respiration and surface water - groundwater interactions in fluvial ecosystems  

NASA Astrophysics Data System (ADS)

Resazurin is a metabolically active compound that undergoes an irreversible reaction to resorufin in the presence of aerobic respiration. The amount of the reaction is linearly proportional to respiration. Consequently, the compound is useful as an tracer of respiration and groundwater - surface water interactions in fluvial ecosystems. We provide a summary of the development and use of resazurin in these contexts, and illustrate with several field examples.

Haggerty, R.; Gonzalez-Pinzon, R.; Marti, E.; Argerich, A.; Myrold, D.; Argerich, A.

2012-12-01

183

fluvial dynamics on landscape vegetation patterns on the Tanana River floodplain, interior Alaska  

Microsoft Academic Search

Aim We examined the interactive effects of mammalian herbivory and fluvial dynamics on vegetation dynamics and composition along the Tanana River in interior Alaska. Location Model parameters were obtained from field studies along the Tanana River, Alaska between Fairbanks (64? 50.50¢ N, 147? 43.30¢ W) and Manley Hot Springs (65? 0.0¢ N, 150? 36.0¢ W). Methods We used a spatially

Lem G. Butler; Knut Kielland; T. Scott Rupp; Thomas A. Hanley

184

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

Microsoft Academic Search

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

Ronald E. Pöppl; Thomas Glade; Margreth Keiler

2010-01-01

185

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

Microsoft Academic Search

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,

John Dearing; Thomas Hoffmann

2010-01-01

186

Tectonic control on fluvial styles: the Balfour Formation of the Karoo Basin, South Africa  

NASA Astrophysics Data System (ADS)

The Balfour Formation represents a fully fluvial succession of late Late Permian-earliest Triassic age which accumulated in the foredeep of the Karoo Basin during the overfilled phase of the foreland system. The lack of a coeval marine environment within the limits of the preserved Karoo Basin provides an opportunity to study the stratigraphic cyclicity developed during a time when accommodation was solely controlled by tectonics. The Balfour stratigraphy is composed of a succession of six third-order fluvial depositional sequences separated by subaerial unconformities. They formed in isolation from eustatic influences, with a timing controlled by orogenic cycles of loading and unloading. Sediment accumulation took place during stages of flexural subsidence, whereas the bounding surfaces are related to stages of isostatic uplift. The vertical profile of all sequences displays an overall fining-upward trend related to the gradual decrease in topographic slope during orogenic loading. At the same time, an upward change in fluvial styles can be observed within each sequence, from initial higher to final lower energy systems. The actual fluvial styles in each location depend on paleoslope gradients and the position of the stratigraphic section relative to the orogenic front. Proximal sequences show transitions from braided to meandering systems, whereas more distal sequences show changes from sand-bed to fine-grained meandering systems. The average duration of the Balfour stratigraphic cycles was 0.66 My, i.e. six cycles during 4 My. No climatic fluctuations are recorded during this time, with the long-term climatic background represented by temperate to humid conditions.

Catuneanu, Octavian; Elango, Henry N.

2001-04-01

187

The use of sediments to detect human impact on the fluvial system  

Microsoft Academic Search

Sediments have been used to detect sources of contamination in a catchment of the Port Jackson (Sydney Harbour) estuary and\\u000a to evaluate the effects of different land-use practices on the fluvial environment. Mean enrichment (mean concentrations over\\u000a pre-anthropogenic background) of size-normalized (<62.5??m) aquatic sediment is 10 × for Cu, 20× for Pb and 90× for Zn adjacent\\u000a to industrialized areas

G. F. Birch; E. Robertson; S. E. Taylor; D. M. McConchie

2000-01-01

188

Fluvial Trace Fossils in the Middle Siwalik (Sarmatian-Pontian) of Darjeeling Himalayas, India  

E-print Network

the Middle Siwalik Successions (Mallet 1875; Gansser 1964; Raju 1969; Chaudhri 1972; Banerjee and Banerjee 1982). Essentially continental, fluvial Siwalik deposits (Kumar et al. 2004) are overrid- den in the north by Precambrian metamorphites (Dahling Group...) across a thrust. A thin slice of coal-bearing Gondwana deposits is exposed as a tectonic window in between Precambrian rocks and the Siwaliks, which is traceable from Kalijhora in the west and Bagrakot in the east. One road-cut section at sevoke road...

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

2013-08-01

189

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

Microsoft Academic Search

The varved sediments that accumulate in the Cariaco Basin provide a detailed archive of the region’s climatic history, including a record of the quantity of fluvial and wind-transported material. In this study, we examine the sedimentological characteristics (clay mineralogy and grain size) of both surface sediments and sinking lithogenic material collected from sediment trap samples over a three-year period from

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

2009-01-01

190

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

191

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

192

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

USGS Publications Warehouse

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

Reheis, M.C.

1992-01-01

193

Catalase in fluvial biofilms: a comparison between different extraction methods and example of application in a metal-polluted river  

Microsoft Academic Search

Antioxidant enzymes are involved in important processes of cell detoxification during oxidative stress and have, therefore,\\u000a been used as biomarkers in algae. Nevertheless, their limited use in fluvial biofilms may be due to the complexity of such\\u000a communities. Here, a comparison between different extraction methods was performed to obtain a reliable method for catalase\\u000a extraction from fluvial biofilms. Homogenization followed

Chloé Bonnineau; Berta Bonet; Natàlia Corcoll; Helena Guasch

2011-01-01

194

Tectonic control on the evolution of the fluvial systems of the Vinchina Formation (Miocene), northwestern Argentina  

NASA Astrophysics Data System (ADS)

The Miocene Vinchina Formation accumulated in a large foreland basin is related to the uplift of the Andes Mountains. This 5100 m thick unit was mostly deposited in fluvial environments, but short episodes of eolian and lacustrine sedimentation also occurred. Low-angle intraformational unconformities and dramatic facies changes define three depositional sequences. Sequence S1 is composed of sandstones and mudstones deposited in anastomosing river systems during a period of tectonic quiescence. Sequence S2, formed by conglomerates and sandstones with scarce intercalations of mudstones, rests on a low-angle erosional surface and represents deposition in fluvial braided systems. S2 probably resulted from progradation of clastic wedges after an episode of uplift of the fold-thrust belt. Sequence S3, dominated by sandstones, mudstones, and sparse intraformational conglomerates, was deposited in ephemeral braided and meandering rivers governed by a complex balance between subsidence and supply. Fluvial styles in the Vinchina Formation allowed the recognition of three major stages in the foreland basin evolution. During the underfilled stage (S1), high subsidence rates favored the development of axial anastomosing rivers with well-preserved floodplain sediments. Early post-tectonic sedimentation marks initial overfilled conditions (S2), characterized by high sediment supply and progradation of clastic wedges as braided rivers deposits. Finally, more advanced overfilled conditions (S3) were reached when sediment supply matched subsidence, giving birth to ephemeral braided and meandering systems.

Limarino, C.; Tripaldi, A.; Marenssi, S.; Net, L.; Re, G.; Caselli, A.

2001-12-01

195

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

NASA Astrophysics Data System (ADS)

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

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

2008-06-01

196

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

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

197

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

USGS Publications Warehouse

Most precipitation falling on subwatershed No. 5 does not flow through the reservoir. During this study approximately three-fourths (47,000 acre-feet) of the precipitation was lost by evaporation and transpiration; a small amount is lost by deep subsurface percolation. Fifty-nine percent of the total sediment load was discharged from the reservoir during four major outflow periods representing 34 percent of the outflow days. The highest percentage of runoff and sediment yield occurs from March through June. Fifty-three percent of the water discharged and 63 percent of the sediment yield occurred during this 4-month period. The average annual yield of fluvial sediment from watershed No. 5 was 607 tons per square mile, or 0.95 ton per acre. A total of 21,370 tons of fluvial sediment was transported into reservoir No. 5 and a total of 19,930 tons was deposited. Seventy-eight percent of the total fluvial sediment was deposited during the first 9.2 years, or 63 percent of time of reservoir operation. The computed trap efficiency of reservoir No. 5 was 93 percent.

Bednar, Gene A.; Waldrep, T.E.

1973-01-01

198

Fluvial dynamics of the lower Guadalete River in W-Andalucía (Spain) and decisive driving forces  

NASA Astrophysics Data System (ADS)

This study aims to work out a solid stratigraphy for the Guadalete River in W-Andalucía with focus on late Pleistocene and Holocene fluvial dynamics. We studied 14 profile exposures and 13 percussion drillings by using geomorphologic, sedimentologic and pedogenetic approaches. Supported by ample physical and chemical soil analyses and dating of 34 radiocarbon samples, we were able to reconstruct floodplain development over the last 14 ka. The valley of the lower Guadalete River shows a fluvial architecture that is complex and inconsistent along specific river sections. According to stratigraphic findings, the lower reach of the Guadalete River can be divided into two sedimentary areas. These are characterized by a highly dynamic alternation of sedimentation and erosion, with Holocene terrace formation in the upper downstream section and more calm conditions with sediment preservation and the built-up of continuous sequences in the lower one. Stratigraphic records in combination with a disturbed longitudinal profile revealed that fluvial dynamics responded to various driving forces in late Pleistocene and Holocene times. Sea-level changes have been a determining factor on river dynamics, notably during the late Pleistocene and until the early Holocene, when phases of sea-level fall resulted in strong river incision and clearing-out of floodplain sediments. In the course of a rapid sea-level rise until the early to mid-Holocene, other parameters started to play a determining role, as fluvial dynamics became more and more the expression of environmental conditions in terms of stability and instability of the landscape. As the study area has to be characterized as tectonically very active, the magnitude of fluvial processes, such as river incision was furthermore influenced by small-scale tectonic uplift or subsidence. Periods of floodplain sedimentation (before 9.2, after 8.0, at 4.6 to 4.3, at 2.0, 0.9 and 0.4 ka cal BP) are reflective for unstable landscape conditions, often related to aridification. For a comprehensive consideration of triggers of floodplain sedimentation, we have likewise to take human behavior into account. It is not possible, however, to clearly differentiate between the impact of climate and humans on geomorphologic activity, but it seems reasonable that anthropogenic exploitation and cultivation activities contributed to raise the environmental pressure exerted by increased aridity.

Wolf, Daniel; Faust, Dominik

2013-04-01

199

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

200

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

201

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

202

Proceso de cloracin La cantidad de cloro necesaria es determinada por la cantidad de agua estancada en el pozo. Contacte a la compaa  

E-print Network

Proceso de cloración La cantidad de cloro necesaria es determinada por la cantidad de agua el nivel de agua estática. La profundidad del agua estancada en el pozo será la profundidad del pozo menos el nivel del agua estática. Por ejemplo, un pozo de agua de 110 pies de profundidad con un nivel

203

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

204

Late-Stage Fluvial Erosion in a Changing Climate on Early Mars  

NASA Astrophysics Data System (ADS)

The decline of heavy bombardment in the solar system coincided with incision of many branching fluvial valleys in the martian highlands. However, these valley networks are underdeveloped relative to typical terrestrial networks, suggesting that valley incision was geologically brief or slow on Mars. Most previous studies have attributed the end of martian fluvial erosion to a monotonic decline of the atmosphere and climate around the Noachian/Hesperian transition. Identification of fluvial valleys on some younger surfaces, including Hesperian volcanoes, and the occurrence of morphologically pristine and degraded reaches in the same valley networks challenged the simplicity of this model. More recently, fluvial valleys and deposits have been recognized on a variety of Hesperian surfaces, including the plateau around Valles Marineris, certain impact craters, and the crustal dichotomy boundary scarp. The extent to which this late-stage erosion represents localized event floods or more widely distributed precipitation and runoff remains to be determined. To evaluate whether Hesperian resurfacing processes were concurrent with (and may have caused) late-stage fluvial erosion, we are identifying any geologically rare or long-lived events that occurred between significant resurfacing events and fluvial erosion of those surfaces. In a variety of locations, we have identified small primary craters that formed between local resurfacing and fluvial dissection of those surfaces, suggesting a gap in time between resurfacing and dissection. These small, otherwise fresh craters have rims or ejecta that were incised by late-stage flows. In other cases, thick stratified deposits accumulated on Hesperian surfaces, and those deposits were later dissected by running water. We also found that highland intercrater plains generally have Early to mid-Hesperian crater populations at diameters less than about 4 km. All smaller primary and secondary craters from the Noachian Period were eradicated. These observations suggest the following geomorphic history. 1) Crater degradation and intercrater resurfacing extended into the Early Hesperian Epoch, but perhaps at a declining rate relative to the Noachian Period. 2) Most of the relict valleys formed as crater degradation declined and intercrater geomorphic surfaces began to stabilize, late in the Noachian or early in the Hesperian Period. 3) Impact cratering, volcanism, tectonism, and wind continued to modify the martian surface during the Hesperian Period. Older valley networks experienced some wall retreat and infilling, forming the classic flat-floored morphology. 4) In one or more intervals during the Late Hesperian or Early Amazonian Epochs, many older valleys reactivated, and some new ones formed on Hesperian surfaces. Late-stage erosion was most effective on steep, high-relief slopes, including Late Noachian and Hesperian crater walls, as well as tectonic scarps. In ongoing work, identifying clear stratigraphic relationships between older valleys, interposed geologic features, and younger valleys is key to determining the number and relative ages of erosional events in the martian highlands.

Irwin, R. P.; Matsubara, Y.

2013-12-01

205

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

USGS Publications Warehouse

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

Peterson, F.

1984-01-01

206

PETRLEO EN EL MAR ABIERTO La presencia de petrleo en el agua del mar puede  

E-print Network

PETR�LEO EN EL MAR ABIERTO La presencia de petróleo en el agua del mar puede afectar la salud de, los corales y otras comunidades de las aguas profundas también podrían ser afectados. PETR�LEO Y USO disfrutamos y dependemos de las aguas del Golfo y de la costa, ya sea para la pesca, los deportes acuáticos

207

Determinacin de Criterios Numricos de Nutrimentos para Lagos y Reservas de Agua en Puerto Rico*  

E-print Network

Determinación de Criterios Numéricos de Nutrimentos para Lagos y Reservas de Agua en Puerto Rico inventario Nacional de Calidad de Agua de los Estados Unidos identifica los nutrimentos como la principal causa de contaminación de las aguas. Más de 3.4 millones de acre de lagos y 84,000 millas de ríos están

Gilbes, Fernando

208

POSGRADO EN GESTIN Y OPERACIN DE PLANTAS DE TRATAMIENTO DE AGUAS  

E-print Network

EEES 2012/13 POSGRADO EN GESTI�N Y OPERACI�N DE PLANTAS DE TRATAMIENTO DE AGUAS #12;Joaquim Olivé agua con más de 140 años de experiencia. Agbar es un referente a nivel nacional e internacional con expertise de Agbar, ofreciendo a las empresas del agua y del medio ambiente soluciones y tecnologías basadas

Politècnica de Catalunya, Universitat

209

En el ao 1991se creaba el Insti-tuto Universitario del Agua y las  

E-print Network

En el año 1991se creaba el Insti- tuto Universitario del Agua y las Ciencias otra denominación, se imparte el máster Gestión Sostenible y Tec- nología del Agua, adaptado al Es participan 38 profesores de universidad y 12 profesionales del sector agua. «El que se haya mantenido todo

Escolano, Francisco

210

LA CONSTRUCCIN Y CONSOLIDACIN DE UNA PERCEPCIN SOCIAL EN LOS CONFLICTOS DEL AGUA EN ESPAA  

E-print Network

1 LA CONSTRUCCI�N Y CONSOLIDACI�N DE UNA PERCEPCI�N SOCIAL EN LOS CONFLICTOS DEL AGUA EN ESPA�A EL consolidando ideas, en este caso la de que las obras hidráulicas son la solución a los problemas del agua de comunicación, agua, percepción social, conflictos Introducción El presente estudio está basado en nuestro

Paris-Sud XI, Université de

211

Aplicaciones de Arc GISAplicaciones de Arc GIS en Recursos de Aguaen Recursos de Agua  

E-print Network

Aplicaciones de Arc GISAplicaciones de Arc GIS en Recursos de Aguaen Recursos de Agua Alejandra 14: 440 personas/km2 vrs India y Jap�n 338vrs India y Jap�n 338 perper/km2./km2. El uso del agua se ha incrementado un 1.6% de 1970 aEl uso del agua se ha incrementado un 1.6% de 1970 a 1995 con 2

Gilbes, Fernando

212

Tratamiento pasivo de aguas cidas de mina con caliza y MgO  

E-print Network

Tratamiento pasivo de aguas ácidas de mina con caliza y MgO: Resultados de los ensayos de campo en de lodos piríticos 200m Pozo de desagüe #12;Lugar de estudio (III): Calidad del agua de mina · pH: 2 debajo de la balsa de lodos Toma de agua Decantador de salida del bidón B Decantador de salida del bidón

Politècnica de Catalunya, Universitat

213

Congreso Internacional 1810-2010: 200 aos de Iberoamrica -1817 EL AGUA Y ALGUNOS PROBLEMAS  

E-print Network

Congreso Internacional 1810-2010: 200 años de Iberoamérica - 1817 EL AGUA Y ALGUNOS PROBLEMAS hídricos, sus implicaciones jurídicas y como compatibilizar uso y protección del agua con el aumento de la populación del planeta. Las reservas mundiales de agua dulce están restringidas a una parcela mínima de

Paris-Sud XI, Université de

214

Agua en la Luna? El hidrgeno es el elemento ms comn  

E-print Network

¿cómoves? 30 ¿Agua en la Luna? El hidrógeno es el elemento más común en el Universo y el oxígeno es átomos se unen para formar agua. La Luna es el primer cuerpo celeste que viene a la mente, ya que saber si tiene o no agua es de crucial importancia para la futura exploración y colonización de nuestro

Rodriguez, Luis F.

215

El tratamiento con cloro es un mtodo para desinfectar un pozo de agua. Se recomien-  

E-print Network

El tratamiento con cloro es un método para desinfectar un pozo de agua. Se recomien- da cuando un sistema de agua está contam- inado con bacterias. La contaminación puede ocurrir en la instalación del exceso de lluvia entran en el pozo. Si el agua subterránea constituye en sí la fuente de bacterias, el

216

Desarrollo y Aplicacin de un ndice de Calidad de Agua para ros en Puerto Rico  

E-print Network

Desarrollo y Aplicación de un Índice de Calidad de Agua para ríos en Puerto Rico por Francisco J trabajo presenta la elaboración de un Índice de Calidad de Agua (ICA) para los ríos en Puerto Rico. Dicho índice pretende clasificar en una escala de 0 a 100 la calidad representativa del agua, según los

Gilbes, Fernando

217

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

PubMed

In order to identify a more efficient biosorbent for (137)Cs, we have investigated the biosorption behavior and mechanism of (137)Cs on Rhodosporidium fluviale (R. fluviale) strain UA2, one of the dominant species of a fungal group isolated from a stable cesium solution. We observed that the biosorption of (137)Cs on R. fluviale strain UA2 was a fast and pH-dependent process in the solution composed of R. fluviale strain UA2 (5 g/L) and cesium (1 mg/L). While a Langmuir isotherm equation indicated that the biosorption of (137)Cs was a monolayer adsorption, the biosorption behavior implied that R. fluviale strain UA2 adsorbed cesium ions by electrostatic attraction. The TEM analysis revealed that cesium ions were absorbed into the cytoplasm of R. fluviale strain UA2 across the cell membrane, not merely fixed on the cell surface, which implied that a mechanism of metal uptake contributed largely to the cesium biosorption process. Moreover, PIXE and EPBS analyses showed that ion-exchange was another biosorption mechanism for the cell biosorption of (137)Cs, in which the decreased potassium ions were replaced by cesium ions. All the above results implied that the biosorption of (137)Cs on R. fluviale strain UA2 involved a two-step process. The first step is passive biosorption that cesium ions are adsorbed to cells surface by electrostatic attraction; after that, the second step is active biosorption that cesium ions penetrate the cell membrane and accumulate in the cytoplasm. PMID:24631916

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

2014-08-01

218

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

SciTech Connect

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

Zhoa Han-Qing [Daqing Research Institute, Helongjiang (China)

1997-08-01

219

Channel arrangements and depositional styles in the São Lourenço fluvial megafan, Brazilian Pantanal wetland  

NASA Astrophysics Data System (ADS)

The Brazilian Pantanal is an extensive lowland tropical basin characterized by the presence of fluvial megafans and seasonally-inundated savanna floodplain wetlands. With an area of about 16,000 km2, the São Lourenço is the second largest megafan in the Pantanal. Three distinct fluvial channel styles that formed at different times during the late Quaternary are found here. A geomorphological and sedimentary assessment of these depositional patterns provides valuable insight on the environmental context of their evolution. New optically stimulated luminescence data indicate that the upper five meters of sediment in the São Lourenço megafan has been accumulating since the late Pleistocene. Ancient fan lobes, located in upper and intermediate fan settings, consist of medium- and coarse-grained fluvial sands and exhibit well-preserved distributary braided paleochannels on their surfaces. As the megafan evolved through time, Pleistocene lobes were incised by a prominent valley filled with Holocene-aged meander belt deposits, which consist of silts interbedded with very fine sands and clays. Currently, the incised valley is a zone of sediment bypass. Modern deposition occurs along the distal toe of the megafan system, where lobes characterized by distributary channel-levee ridges are widespread. These features formed by progradation of avulsion belts into a broad swampy floodbasin, which caused the lower portion of the meander belt to be abandoned. The significant differences observed in intra-fan morphology appear to be linked to the variability in effective precipitation. Fan lobes deposited with braided distributary channels occurred under relatively dry conditions in the late Pleistocene. By contrast, aggradational meander belt deposits and lobes with distributary channel-levee ridges formed during fluctuating precipitation conditions of the Holocene, when the Pantanal emerged from deglacial aridity. Modern lobes form under heavy seasonal flooding and deposition occurs in response to very rapid and common avulsion events. These results have implications for interpreting the complexity of megafan facies in similar continental basins.

Assine, Mario Luis; Corradini, Fabrício Anibal; Pupim, Fabiano do Nascimento; McGlue, Michael Matthew

2014-03-01

220

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

221

Fluvial Erosion and Transportation of an Impact Regolith Layer: Implications for Titan  

NASA Astrophysics Data System (ADS)

Large regions of Titan appear to be eroded cratered terrain. If this is correct, then Titan’s surface could have been characterized by a regolith hundreds of meters thick with abundant unconsolidated debris in the size range that could be fluvially transported and serving as tools for bedrock incision. We utilized a variant on our Landform Evolution Model, originally developed to understand fluvial erosion on Mars, to study this issue. We see two end-member results. Slopes covered with coarse grained material develop a drainage network that essentially becomes stabilized after a sufficient time. They become paved with gravel that can only be eroded very slowly, if at all, after some degree of erosion. Simulations with finer sediment (for example with the maximum grain size only 16 mm) the flow can transport a good bit of sediment throughout the simulation, and drainage basins are initially created, but the topography evolves into a gentle slope of parallel drainage. For gravel channel systems under high sediment transport situations, there is no downstream concavity - the channels are essentially uniform in slope so that no drainage basins form. However, for coarser sediment we are near the threshold of motion near the end of the simulation, and channel gradients decrease downstream, implying a well-developed drainage network will form. However, if boulders are intermixed with the fines (which is reasonable), upland surfaces could eventually become mantled with a pavement of coarse debris after differential removal of transportable sediment, thus limiting net erosion unless a weathering (rock-disintegrating) process occurs on Titan. Titan’s fluvial networks could have been quickly established, then become somewhat impervious to further landscape evolution even if the precipitation rates and intensities persisted for long times.

Moore, Jeffrey M.; Howard, Alan D.; Breton, Sylvain

2014-11-01

222

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

223

External controls on Quaternary fluvial incision and terrace formation at the Segre River, Southern Pyrenees  

NASA Astrophysics Data System (ADS)

Focusing on climatic- and structural (tectonic) controls, we aim to determine their relative importance for the (Pliocene to Quaternary) fluvial landscape evolution in the Southern Pyrenees foreland. We investigate the Segre River, which is one of the major streams of the Southern Pyrenees that drains the elevated chain towards the Ebro foreland basin. Along its course, the Segre River has a flight of fluvial cut-and-fill (and strath-type) terraces preserved that have been mapped based on DEM's and geomorphological fieldwork. This paper presents the first results of our study and reports on the Segre terrace staircase, which is characterized by seven major Quaternary terrace levels with elevations up to more than 110 m above the modern floodplain. At the upper and middle reaches, the semi-parallel terraces of the Segre River occasionally show anomalies featuring extensive gravel thickness and deformation caused by faulting, folding and local subsidence. The longitudinal correlations of terrace levels reveal increased vertical terrace spacing in the foreland, which could originate from enhanced fluvial erosion after the Mid-Pleistocene climate transition in combination with base level lowering controlled by the progressive downcutting of the Catalan Coastal Range. Since the Ebro Basin opening (Late Miocene), the Catalan Coastal Range, which borders the Ebro foreland basin to the Mediterranean Sea, was progressively cut down and the exorheic drainage system gradually adjusted to sea level. The Segre longitudinal terrace profiles and the Ebro gorge morphology at the Catalan Coastal Range indicate a base-level of about 200 m.s.l. at the beginning of (Pleistocene) terrace formation, which implies that the Catalan Coastal Range might have functioned as a local base-level upstream of the sea outlet, presumably until the Late Pleistocene. Alternatively, a yet unknown tectonic process might have caused base level lowering and the preservation of terrace staircases at the Ebro drainage system.

Stange, Kurt Martin; van Balen, Ronald; Vandenberghe, Jef; Peña, Jose Luis; Sancho, Carlos

2013-08-01

224

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

225

River incision rates and fluvial landform development in the French Western Alps  

NASA Astrophysics Data System (ADS)

The processes of fluvial erosion and transport constitute the main controls on continental morphology and sediment flux. A quantification of these processes is therefore essential for our understanding of the interaction between tectonics and long-term landscape development. Studying the development of fluvial form over time may lead to significant progress in our understanding of the dynamics of, and controls on, bedrock river behavior but a precise control on initial conditions and timing is crucial in such studies. We present a case-study from the French Western Alps where river long-profile and floodplain development were studied on different temporal scales (10^3--10^6 y), on rivers that experienced varying amounts of climatic disturbance. Paleo-river profiles were reconstructed using abundant terrace remnants dated using in situ-produced cosmogenic 10Be. The Drac River long-profile evolution is controlled by rapid km-scale base-level fluctuations due to glacial damming of its lower valley and subsequent ice-dam disappearance. Its long profile has developed by rapid knickpoint retreat and exceedingly high incision rates to reach postglacial equilibrium into ˜20 ky. The contiguous Buëch river experienced limited glacial influences. Its short-term (10^3) incision rates are sensitive to climatic forcing whereas its long-term (10^5 y) incision rates are consistent with regional denudation rates, suggesting long-term equilibrium between uplift and incision. A comparison of fluvial long-profiles, valley widths, drainage area and incision rates shows that rivers similar to the Buëch river with low incision rates are characterized by lithological knickpoints for drainage areas <˜35 km^2. Downstream of this threshold, lithological and discharge variations are expressed as a variation in valley width without changes in channel slope. The rapidly incising Drac River profile shows knickpoints on resistant lithologies all along its profile and do not exhibits any significant valley flat. These differences can be explained by fluvial incision models in which river behavior changes from detachment-limited to transport-limited downstream, but where detachment-limited behavior is favored by high incision rates and resistant bedrock.

Brocard, G.; van der Beek, P.; Bourlès, D.; Siame, L.

2003-04-01

226

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

227

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

228

An ancient example of fluvial cave sediment derived from dust (eolian silt) infiltration  

NASA Astrophysics Data System (ADS)

Silt-rich grain size distributions are geologically rare and typically eolian. Such sediments (and lithified equivalents) are called dust/dustites in a general case, or loess/loessite in the special case of eolian silts derived from glacial deposits. In both cases, silt-rich deposits require a source area of silt-sized materials, transport mechanisms (prevailing winds of sufficient energy) and one or more depositional mechanisms (such as trapping in the lee of topographic obstacles or adhesion to surfaces with moisture or vegetation). This study evaluates a third type of silt-rich geological deposit, paleo-cave sediments derived from mixtures of dust (eolian silt) and karst breccias. Cave sediments can be autochthonous (speleothems), parautochthonous (karst breccias), and allochthonous (such as fluvial cave sediments). The provenance of fluvial cave sediments is the landscape overlying the cave-karst system, and they are introduced to the cave-karst system by flood events. The Mississippian Leadville Limestone (SW Colorado) was subject to karst processes following Late Mississippian eustatic sea-level fall. These processes included formation of phreatic tubes, tower karst (kegelkarst), solution valleys (poljes), sinkholes (dolines), solution-enhanced joints (grikes), surficial flutes (rillenkarren), solution pans (kamenitzas), and breakout domes containing mosaic and crackle breccias. Flowstone, dripstone, and cave pearls are interbedded with karst breccias and fluvial cave sediments in the Leadville Limestone. The overlying Pennsylvanian Molas Formation is an eolian siltstone (dustite) with sediment sources from the peri-Gondwanan and Grenville rocks of eastern North America. Evidence that the fluvial cave sediments in the Leadville Limestone are derived from this dustite include compositional and textural matches, especially grain size distribution trends vertically downward from the former landscape surface. These grain size trends indicate infiltration of the dustite into the underlying cave-karst system. There is a significant amount of evidence that the resedimentation process was episodic. Some individual phreatic tubes have complex infill history of up to eight events (successive debrites or inundites interbedded with speleothems). Some individual vertical grikes have complex infill histories of as many as six laminated or massive jointites with weakly developed paleosols superimposed on these individual deposits. Late Cenozoic cave sediments are increasingly utilized as archives of geologic change. The role of dust (eolian silt), including its inherited compositional and textural properties from a distant source area, land-atmosphere transfer processes, and resedimentation processes on the land surface overlying the cave-karst system, remain promising areas for research.

Evans, J. E.

2011-12-01

229

Computer programs for computing particle-size statistics of fluvial sediments  

USGS Publications Warehouse

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

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

1986-01-01

230

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

231

Stream capture and piracy recorded by provenance in fluvial fan strata  

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

232

Revista "Computacion y Sistemas", Vol. 8, No. 4, June 2005 Segmentacion de imagenes en color utilizando  

E-print Network

en los histogramas bi-variables, fundado en la transformaci´on de la l´inea divisoria de aguas. Despu´atica, transformaci´on l´inea divisoria de aguas, segmentaci´on color, clasificaci´on morfol´ogica Abstract The choice

Angulo,Jesús

233

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

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 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...

2011-04-01

234

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

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 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...

2013-04-01

235

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

Code of Federal Regulations, 2012 CFR

...2012-04-01 2011-04-01 true 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...

2012-04-01

236

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

...2014-04-01 2014-04-01 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...

2014-04-01

237

Campus de Excelencia Internacional Sensores y robtica para aplicaciones avanzadas Ingeniera del agua  

E-print Network

agua · Communications for smart environments · Nanoingeniería · Ciencias · Tecnología de polímeros mejora · Ingeniería de las TIC · Urbanismo y ordenación del territorio · Tratamiento de aguas y gestión

Politècnica de Catalunya, Universitat

238

Seminario sobre temas estratégicos del agua en América Latina y el Caribe agenda para la acción  

Microsoft Academic Search

En el corto plazo, con apoyo del Banco, América Latina y el Caribe se preparan para elaborar un informe regional sobre financiamiento del agua a ser presentado a las agencias de financiamiento durante el Tercer Foro Mundial del Agua, a llevarse a cabo en 2003 en Kyoto. Para contribuir en este proceso, el Banco organizó el presente seminario e invitó

Jerson Kelman; Benedito Braga; Humberto Peña; César Herrera Toledo; Víctor Pochat; Max Campos; Margaret Catley-Carson; Peter Rogers; Raymundo José Garrido; Adrián Baltanás García; Arnold Sánchez; Herman Rosa; Michel Camdessus; Enrique V. Iglesias; Hyperides Pereira de Macedo; Jamal Saghir; Aser Cortines Peixoto Filho; Sergio Heumann; Linda Kemeny; Fuensanta Díaz Cobacho; Carlos M. Jarque

2002-01-01

239

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

240

Clausura de curso del Mster en Gestin Sostenible y Tecnologas del Agua de la Universidad de Alicante  

E-print Network

Clausura de curso del Máster en Gestión Sostenible y Tecnologías del Agua de la Universidad de el Tratamiento del Agua (ATTA) pronunciará la ponencia de clausura Finaliza el curso de los estudios oficiales del Máster en Gestión Sostenible y Tecnologías del Agua de la UA que imparte el Instituto del Agua

Escolano, Francisco

241

Characterization and 3D reservoir modelling of fluvial sandstones of the Williams Fork Formation, Rulison Field, Piceance Basin, Colorado, USA  

NASA Astrophysics Data System (ADS)

This study describes the stratigraphic characteristics and distribution of fluvial deposits of the Upper Cretaceous Williams Fork Formation in a portion of Rulison Field and addresses 3D geologic modelling of reservoir sand bodies and their associated connectivity. Fluvial deposits include isolated and stacked point-bar deposits, crevasse splays and overbank (floodplain) mudrock. Within the Williams Fork Formation, the distribution and connectivity of fluvial sandstones significantly impact reservoir productivity and ultimate recovery. The reservoir sandstones are primarily fluvial point-bar deposits interbedded with shales and coals. Because of the lenticular geometry and limited lateral extent of the reservoir sandstones (common apparent widths of ~500-1000 ft; ~150-300 m), relatively high well densities (e.g. 10 acre (660 ft; 200 m) spacing) are often required to deplete the reservoir. Heterogeneity of these fluvial deposits includes larger scale stratigraphic variability associated with vertical stacking patterns and structural heterogeneities associated with faults that exhibit lateral and reverse offsets. The discontinuous character of the fluvial sandstones and lack of distinct marker beds in the middle and upper parts of the Williams Fork Formation make correlation between wells tenuous, even at a 10 acre well spacing. Some intervals of thicker and amalgamated sandstones within the middle and upper Williams Fork Formation can be correlated across greater distances. To aid correlation and for 3D reservoir modelling, vertical lithology proportion curves were used to estimate stratigraphic trends and define the stratigraphic zonation within the reservoir interval. Object-based and indicator-based modelling methods have been applied to the same data and results from the models were compared. Results from the 3D modelling indicate that sandstone connectivity increases with net-to-gross ratio and, at lower net-to-gross ratios (<30%), differences exist in the cumulative volume of connected sandstone bodies between the indicator- and object-based lithology models. Therefore, the types of lithology-modelling methods used for lower net-to-gross ratio reservoir intervals are important.

Pranter, Matthew J.; Vargas, Marielis F.; Davis, Thomas L.

2008-06-01

242

Magmatic intrusions and a hydrothermal origin for fluvial valleys on Mars  

NASA Astrophysics Data System (ADS)

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

Gulick, Virginia C.

1998-08-01

243

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

244

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

PubMed

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

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

2011-04-01

245

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

USGS Publications Warehouse

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

Porterfield, George

1972-01-01

246

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

247

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

248

Case study of climatic changes in Martian fluvial systems at Xanthe Terra  

NASA Astrophysics Data System (ADS)

An unnamed valley system was analyzed in Xanthe Terra south of Havel Vallis on Mars where three separate episodes of fluvial activity could be identified with different morphology, water source and erosional processes, inferring formation under different climatic conditions. The oldest scattered valleys (1. group) form interconnecting network and suggest areally distributed water source. Later two valley types formed from confined water source partly supported by possible subsurface water. The smaller upper reaches (2. group) with three separate segments and also a similar aged but areal washed terrain suggest contribution from shallow subsurface inflow. These valleys fed the main channel (3. group), which morphology (wide, theater shaped source, few tributaries, steep walls) is the most compatible with the subsurface sapping origin. While the first valley group formed in the Noachian, the other two, more confined groups are younger. Their crater density based age value is uncertain, and could be only 1200 million years. After these three fluvial episodes etch pitted, heavily eroded terrain formed possibly by ice sublimation driven collapse. More recently (60-200 million years ago) dunes covered the bottom of the valleys, and finally the youngest event took place when mass movements produced debris covered the valleys' slopes with sediments along their wall around 5-15 million years ago, suggesting wind activity finished earlier than the mass movements in the region. This small area represents the sequence of events probably appeared on global scale: the general cooling and drying environment of Mars. Comparing the longitudinal profiles here to other valleys in Xanthe Terra, convex shaped valley profiles are usually connected to steep terrains. The location of erosional base might play an important role in their formation that can be produced convex shapes where the erosional base descended topographically (by deep impact crater or deep outflow channel formation) as time passed by. The analysis of such nearby systems that probably witnessed similar climatic forces in the past, provides ideal possibility to identify reasons and geomorphological context of longitudinal profile shape formation for fluvial valleys in general. Three different groups of valleys were identified at a system in Xanthe Terra. The oldest scattered valleys formed by areal water source. Younger upper reaches might form by linear and areal flow, lower reaches by sapping. Crater density based ages are uncertain, but point to activity 600-1200 million years ago. Dunes are 60-200, talus slopes are 5-15 million years old in the valleys.

Kereszturi, Akos

2014-06-01

249

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

250

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

251

Fluvial terrace formation along Wyoming's Laramie Range as a response to increased late Pleistocene flood magnitudes  

NASA Astrophysics Data System (ADS)

This study evaluates the potential climatic mechanisms involved in fluvial terrace genesis along Wyoming's Laramie Range. We used optical dating methods to determine depositional ages for fluvial fills, and to calculate incision rates for terrace suites along two of the region's larger rivers. Optical ages were determined for the five lowest terrace levels (T5-T1) which were deposited at ˜ 59.6, 39.2, 26.3, 22.7, and 18.5 ka, and incision rates calculated for the two rivers were ˜ 0.29-0.34 m/kyr over the last ˜ 60 kyr. The formation of fluvial terraces in the central Rocky Mountains is commonly attributed to climatically induced changes in sediment input. According to most studies, relatively low incision rates existed during the colder periods of the Pleistocene due to high stream sediment loads, but terraces were formed during warmer interglacial periods when reduced sediment availability facilitated higher incision rates. However, this conceptual model cannot explain the incision records presented here, which show that the streams incised 9-10 m in two to three events during Oxygen Isotope Stage 2, but only 1-2 m during the warmer climates of the last ˜ 18.5 ka. The stream power model we adapted to this setting suggests that late Quaternary streams operated under two basic states. During the colder conditions of the Pleistocene, higher flood magnitudes resulted in higher lateral erosion and incision rates. However, the lower stream discharge common to the warmer interglacial periods resulted in relatively inactive streams when both lateral erosion and incision rates were lowered. This model can explain the high incision rates during the cold conditions of Oxygen Isotope Stage 2, the occurrence of terrace fill ages near cold to warm transitions, and the apparent acceleration in incision rates toward the end of the last glacial cycle. Finally, this study suggests that terrace fill ages and incision rates are similar for the distally glaciated Laramie River, nonglaciated Sybille Creek, and the proximally glaciated streams that drain the Wind River Range. This implies that rivers responded synchronously to late Quaternary climate changes regardless of their influence by alpine glaciation.

Hanson, Paul R.; Mason, Joseph A.; Goble, Ronald J.

2006-06-01

252

Late-Quaternary Fluvial Aggradation and Incision in the Yuchi Basin, Central Taiwan  

NASA Astrophysics Data System (ADS)

The origin of a series of N-S trending basins in central Taiwan, surrounded by 1000-2000m-high mountains, has long been an unsolved issue. We studied one of these basins, the Yuchi Basin. The basin is floored by a N-inclining (< 1›X) surface of fluvial origin (the main surface), which has been deeply incised by four river systems by as much as 80 m. These rivers (combined basin area: 72 km2) join to each other and flow out of the basin to the north through a gorge. We found that the basin started to accumulate fluvial-lacustrine sediments no later than 200 ka (OIS 8, based on pollen stratigraphy). Parts of these Pleistocene deposits has been tilted (<10›X), as observed near the northern edge of the basin, and been incised by at least 55 m (the top of this sequence exposed there is dated >50,000 yr BP). Based on radiocarbon dates, fluvial aggradation in the western part of the basin appears to have stopped around 25 ka (24550+360/-350, 5 m below the main surface). The aggradation, however, probably proceeded in the eastern part of the basin until about 6 ka (10997-11312 cal. BP, 12 m below the main surface; 6174-6279/6408-6495 cal. BP, 4 m below the surface). As the main surface extends continuously, we believe that although the formation of the main surface appears to be diachronous, the channel incision that abandoned the surface is likely to have started somehow synchronously, or no earlier than 6 ka. The reason for this catastrophic incision is unknown. It is clear that this incision into the Pleistocene strata exposed near the northern edge of the basin is at least 9 mm/yr. Also, the incision only has removed a total of 550000000 m3 material from the deposits underlying the main surface, which amounts to a sediment yield of at least 92000 m3/yr, or an apparent denudation rate of > 1.3 mm/yr over the entire river basins. Note that in this calculation, most parts of the river basins remain intact. Our results therefore show how rapid channel incision can significantly bias the calculated denudation rate over the time scale of Holocene.

Chen, B.; Hsieh, M.; Liew, P.; Chen, Y.

2002-12-01

253

Temporal correlation of fluvial and alluvial sequences in the Makran Range, SE-Iran  

NASA Astrophysics Data System (ADS)

The Makran region of southeastern Iran is an active accretionary wedge with a partially subaerial component. New investigations have revealed a rather complex geodynamic evolution of the Makran active accretionary wedge that is not yet fully understood in its entity. Ongoing convergence between the Arabian and Eurasian plates and tectonic activity since the late Mesozoic has extended all trough the Quaternary. We focus here on fluvial and alluvial sequences in tectonically separated basins that have been deposited probably in the Pliocene/Quaternary, based on stratigraphic classification in official geological maps, in order to understand the climatic and tectonic forces occurring during the ongoing accretionary wegde formation. Specifically, we investigate the influence of Quaternary climate variations (Pleistocene cold period, monsoonal variations) on erosional and depositional processes in the (semi)arid Makran as well as local and regional tectonic forces in the Coastal and Central Makran Range region. Necessary for such an analysis is a temporal calibration of alluvial and fluvial terrace sequences that will allow an inter-basin correlation. We utilize the exposure age dating method using terrestrial cosmogenic nuclides (TCN) due to the lack of otherwise datatable material in the arid Makran region. Limited radiocarbon data are only available for marine terraces (wave-cut platforms). Our preliminary 21Ne and 10Be TCN-ages of amalgamated clast samples from (un)deformed terrace and alluvial sequences range from ~250 ky to present day (modern wash). These ages agree in relative terms with sequences previously assigned by other investigations through correlation of Quaternary sequences from Central and Western Iran regions. However, our minimum ages suggest that all age sequences are of middle to late Pleistocene age, compared to Pliocene age estimates previously assigned for the oldest units. Although often suggested, a genetical relation and connection of those fluvial sequences to coastal terraces and wave-cut platforms is problematic due to ambiguous ages and obscured stratigraphic linkage. Our data suggest that events of terrace formation are roughly coeval between basins, but do not indicate a distinct climate forcing, though there is some tendency that terraces were formed during interglacial periods. Preliminary incision rates derived from strath terraces are on the order of 0.1-3 mm/yr with non-steady intervals. This in turn is well in the range of uplift rates deduced from coastal terraces. Further investigations are on the way, especially resolving complex exposure histories based on combining cosmogenic radionuclides and 21Ne.

Kober, F.; Zeilinger, G.; Ivy-Ochs, S.; Dolati, A.; Smit, J.; Burg, J.-P.; Bahroudi, A.; Kubik, P. W.; Baur, H.; Wieler, R.; Haghipour, N.

2009-04-01

254

Tectonic controls of fluvial incision in Cenozoic Duero Basin (N Iberia)  

NASA Astrophysics Data System (ADS)

The Duero basin, located in the north-west of Iberia, covers approximately 50.000 Km2 and is the largest of the tree main intraplate cenozoic Iberian Basins. This basin shows a complex evolution from end Cretaceous-early Cenozoic times as result of faulting and upbuilding of mountain belts associated to the internal deformation affecting Iberian microplate during Alpine orogenic events. The mountain ranges work as active borders supplying sediments to infill the basin and constraining the basin geometry while, western border of the Duero cenozoic basin is a relatively flat but elevated zone (mean high of 800 m a.s.l) where the variscan basement crops out. This area played an important role in the current configuration of Iberia; acting as a passive border for the Duero Basin during its endorreic evolution. Afterwards, it controls the exoreic evolution of the basin acting as a local base level for the Cenozoic Basin. In this area the Duero river and main tributaries form deep gorges, deeply incised mainly in granitic bedrock. Changes in equilibrium conditions are reflected as changes in main trunk direction and variation in the concavity and steepness of longitudinal profiles, resulting in the presence of numerous knickpoints in the fluvial network. Previous work, in the western border of Duero Cenozoic basin, comparing fluvial incision and fracture pattern, showed a strong structural control either in the orientation of drainage network, either in the incision rates distribution. Analysis of river longitudinal profiles in the whole Basin evidence great differences in profiles shapes; whereas in the Cenozoic Basin profiles are close to equilibrium, in the western Variscan basamen extensive bedrock segments along the active channel include knickzones of steep rapids and short steps, and V-shaped valleys are characteristics of the area. In the present work we quantify incision from the closed Basin base level by comparison of theoretical and real longitudinal profiles. Geomorphic analyses of the longitudinal profiles of major river systems developed along the Basin, distribution of nickpoints and incision from the closed Basin base level is interpreted together with well constrained geological and tectonic pattern, to analyze the role of tectonics in the evolution of drainage in the area. Further studies in fluvial network evolution and its interplay with tectonics in the Duero Basin are currently under study though tectonic, geomorphology, surfaces dating and modeling approaches.

Antón, Loreto; de Vicente, Gerardo; Muñoz Martín, Alfonso

2010-05-01

255

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

256

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

257

Eocene fluvial drainage patterns and their implications for uranium and hydrocarbon exploration in the Wind River Basin, Wyoming  

Microsoft Academic Search

Paleocurrent maps of the fluvial lower Eocene Wind River Formation in the Wind River Basin of central Wyoming define promising uranium- and hydrocarbon-exploration target areas. The Wind River Formation is thought to have the greatest potential for uranium mineralization in areas where it includes arkosic channel sandstones derived from the granitic core of the Granite Mountains, as in the channel-sandstone

Seeland

1978-01-01

258

PUBLISHED ONLINE: 4 AUGUST 2013 | DOI: 10.1038/NGEO1891 Erosion of biofilm-bound fluvial sediments  

E-print Network

LETTERS PUBLISHED ONLINE: 4 AUGUST 2013 | DOI: 10.1038/NGEO1891 Erosion of biofilm-bound fluvial biofilms, which com- prise diverse consortia of species housed in sticky extracellular polysaccharides not hold for biofilm-bound sediments. Instead, biostabilized sediment behaves more like an elastic membrane

Luo, Xiaoyu

259

Movements of Fluvial Bonneville Cutthroat Trout in the Thomas Fork of the Bear River, Idaho–Wyoming  

Microsoft Academic Search

The majority of interior subspecies of cutthroat trout Oncorhynchus clarkii have been extirpated from large rivers by anthropogenic activities that have fragmented habitats and introduced nonnative competitors. Selective pressures against migratory behaviors and main-stem river occupation, coupled with conservation strategies that isolate genetically pure populations above barriers, have restricted gene flow and prevented expression of the fluvial life history in

Warren T. Colyer; Jeffrey L. Kershner; Robert H. Hilderbrand

2005-01-01

260

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

261

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

262

Temporal Reproductive Separation of Fluvial Yellowstone Cutthroat Trout from Rainbow Trout and Hybrids in the Yellowstone River  

Microsoft Academic Search

Yellowstone cutthroat trout Oncorhynchus clarkii bouvierii are genomically extinct throughout much of their historic range because of displacement by and introgression with introduced rainbow trout O. mykiss. However, fluvial Yellowstone cutthroat trout still retain their genetic integrity while coexisting with rainbow trout in the Yellowstone River. We assessed whether spatial or temporal reproductive isolation, or both, occurs between these taxa.

James N. DeRito; Alexander V. Zale; Bradley B. Shepard

2010-01-01

263

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

264

Uso de imagem Quickbird para o mapeamento do uso e ocupação do solo da ilha fluvial denominada Ilha Solteira  

Microsoft Academic Search

The present paper has the objective of showing the adopted methodology in mapping soil usage and occupation in the fluvial area situated between Ilha Solteira (SP) and Selvíria (MS) using techniques such as remote sensing and geographic information systems (GIS). The employed images presented blue, red and green bands and were taken by the Quickbird satellite on October 4, 2006.

Saulo Garé Ginak; André Luiz Altimare

265

Artculo publicado en "II Conferencia de La Alpujarra". Ed. Rosa y Ctedra UNESCO. 151-164. AGUA Y ACEQUIAS EN LA ALPUJARRA (SIERRA NEVADA)  

E-print Network

AGUA Y ACEQUIAS EN LA ALPUJARRA (SIERRA NEVADA) Antonio Castillo Martín Consejo Superior de Investigaciones Científicas e Instituto del Agua de la Universidad de Granada RESUMEN El agua en Sierra Nevada adecuada conservación ambiental, en la que el agua es pieza clave en la conformación del paisaje y en el

Castillo, Antonio

266

Lower Vistula fluvial lakes as possible places of deep groundwaters effluence (Grudzi?dz Basin, North Central Poland)  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

267

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

NASA Astrophysics Data System (ADS)

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

Brown, A. G.

2008-10-01

268

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

USGS Publications Warehouse

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

Hindall, S.M.

1991-01-01

269

Mollusca from Last Interglacial fluvial deposits of the River Thames at Trafalgar Square, London  

NASA Astrophysics Data System (ADS)

An account is given of the molluscan assemblages recovered from fluvial deposits beneath the Upper Floodplain terrace of the River Thames in the vicinity of Trafalgar Square, central London. A total of 37 aquatic and 28 terrestrial taxa have been recorded, a diversity indicative of full interglacial conditions. Palaeobotanical and vertebrate evidence suggests that these fossiliferous sediments belong to the Last (Ipswichian) Interglacial, a conclusion strongly supported by molluscan evidence. The combination of the presence of certain species, such as Belgrandia marginata, Potomida littoralis and Margaritifera auricularia, together with the absence of other taxa that no longer live in Britain, such as Pisidium clessini, Corbicula fluminalis and Unio crassus, imparts a distinctive character to the fauna. These temperate molluscs were not only present in the Trafalgar Square Sands and Silts, but also in the underlying Spring Gardens Gravel, showing the latter to be an interglacial aggradation that did not accumulate during the late Wolstonian, contrary to previous interpretations.

Preece, R. C.

1999-02-01

270

Hydrodynamics of the transition zone from fluvial to tidal regime in the Santee River, SC, USA  

NASA Astrophysics Data System (ADS)

We report the results of field measurements conducted from 2008 through 2012 in the freshwater reach of the Santee River approximately 55±5 km from the mouth, a transition zone from a fluvial to an estuarine tidal regime. The dataset comprises bathymetric surveys, time series of current profiles and bottom pressure at several locations, and the river discharge from the USGS stream gauge station 02171700. Our data indicate that the transition zone is characterized by strong tidal dissipation and distinctive channel geometry. Tidal dissipation is evident in the rapid decrease of the M2 amplitude to the mean along-channel velocity ratio from 2.1 to 0.9 over ~6 km distance. Tides in the study area are predominantly semi-diurnal, highly nonlinear and flood-dominant. Channel cross-sectional area in the transition zone converges at higher rate than both upstream and downstream, while channel depth reveals threefold variations in the form of adjacent shoals and deeps. Our dataset allowed us to resolve the along-channel momentum balance, which includes inertia, momentum advection, pressure gradient, and bottom friction terms. Pressure gradient and inertia dominate the momentum balance during the flood and subsequent current reversal from flood to ebb. However, during the ebb the pressure gradient is nearly balanced by bottom friction. Although tides are flood-dominant, most of the dissipation occurs during the ebb due to a superposition of comparable river and tidal currents subject to quadratic bottom friction. We infer that the enhanced tidal dissipation in the transition zone occurs due to the interaction of fluvial and tidal currents as well as due to the enhanced channel convergence and bathymetric gradients.

Yankovsky, A. E.; Torres-garcia, L. M.; Torres, R.

2012-12-01

271

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

272

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

273

Tectonics from fluvial topography using formal linear inversion: Theory and applications to the Inyo Mountains, California  

NASA Astrophysics Data System (ADS)

Tectonic activity generates topography, and the variability of tectonic forcing is responsible for topographic patterns and variability of relief in fluvial landscapes. Despite this basic relation, the inverse problem, by which features of the topography are used for inferring tectonic uplift rates, has proven challenging. Here we develop formal linear inversion schemes to infer a record of the rate of relative uplift as a function of space and time from the long profiles of rivers. The relative uplift rate is the difference between the rates of rock uplift and of the base level change. The inversion schemes are based on a closed-form analytic solution to the transient linear stream power model, and to increase model resolution they make use of the multiplicity of information made available by multiple rivers and their tributaries. The distribution of the fluvial response time to tectonic perturbations is a key component of the inversion scheme, as this determines which tectonic events are preserved in the topography. We develop two inversion parameterizations that differ in their assumptions about the tectonic forcing: space-invariant and time-space variability with an assumed spatial distribution. The inversion schemes are applied to the Inyo Mountains, an uplifted block along the western boundary of the Basin and Range Province in California. Inversion results indicate that the range has been experiencing an acceleration of the relative uplift in the past ˜2-3 Ma. We use the inversion results to constrain the paleotopography and paleo-erosion rate along the range and to recover the throw rate history along the fault that bounds the Inyo range.

Goren, L.; Fox, Matthew; Willett, Sean D.

2014-08-01

274

The Rivers of Xanadu and beyond : Cassini RADAR Observations of Titan Fluvial Geomorphology  

NASA Astrophysics Data System (ADS)

Cassini RADAR has observed several different styles of fluvial channel on the surface of Titan. These show that hydrological activity modifies Titan's surface both at larger scales than, and in many places beyond, the small-scale channels observed by the Huygens probe. In some cases (T3) the channels have no incision detectable with the (modest 300m) resolution of the radar and have a braided and anabranching appearance, characteristic of washes in the desert southwest USA generated by violent downpours - calculations of the appropriate transport thresholds and network characteristic show that the liquid methane flowrates implied in the rivers are consistent with models of rainstorms on Titan, in turn suggesting remarkable storms with several tens of cm of rainfall, perhaps a century's worth, in only a couple of hours. Elsewhere (T7) radarclinometry shows appreciable incision, suggesting rain is recurrent in some midlatitude areas. The longest channel network observed (T13) so far is that at the Western part of Xanadu, paradoxically at a latitude where large areas (the Belet Sand Sea among others) exist where no other large channel is visible. This suggests that Xanadu's rugged topography (also evident in the radar images) may influence precipitation patterns, for which latitude is already an established factor. These observations highlight Titan as a laboratory for hydrological and meteorological processes like those on Earth. Radar mapping is proving key to elucidate a picture of how Titan works as an active planet - the geological record of precipitation patterns records the integral of fluvial modification, which may in turn be too sporadic to reliably record. The results underscore the need to maximize return from the Cassini Extended Mission, and for future in-situ survey of Titan by a balloon or similar mission.

Lorenz, R. D.

2006-12-01

275

Effects of estuarine and fluvial processes on sediment transport over deltaic tidal flats  

NASA Astrophysics Data System (ADS)

Tidal flats at a river mouth feature estuarine and fluvial processes that distinguish them from tidal flats without river discharge. We combine field observations and a numerical model to investigate hydrodynamics and sediment transport on deltaic tidal flats at the mouth of the Skagit River, in Puget Sound, WA, during the spring freshet. River discharge over tidal flats supplies a mean volume flux, freshwater buoyancy, and suspended sediment. Despite the shallow water depths, strong horizontal density fronts and stratification develop, resulting in a baroclinic pressure gradient and tidal variability in stratification that favor flood-directed bottom stresses. In addition to these estuarine processes, the river discharge during periods of low tide drains through a network of distributary channels on the exposed tidal flats, with strongly ebb-directed stresses. The net sediment transport depends on the balance between estuarine and fluvial processes, and is modulated on a spring-neap time scale by the tides of Puget Sound. We find that the baroclinic pressure gradient and periodic stratification enhance trapping of sediment delivered by the river on the tidal flats, particularly during neap tides, and that sediment trapping also depends on settling and scour lags, particularly for finer particles. The primary means of moving sediment off of the tidal flats are the high velocities and stresses in the distributary channels during late stages of ebbs and around low tides, with sediment export predominantly occurring during spring low tides that expose a greater portion of the flats. The 3-d finite volume numerical model was evaluated against observations and had good skill overall, particularly for velocity and salinity. The model performed poorly at simulating the shallow flows around low tides as the flats drained and river discharge was confined to distributary channels, due in part to limitations in grid resolution, seabed sediment and bathymetric data, and the wetting-and-drying scheme. Consequently, the model predicted greater sediment retention on the flats than was observed.

Ralston, David K.; Geyer, W. Rockwell; Traykovski, Peter A.; Nidzieko, Nicholas J.

276

Effects of estuarine and fluvial processes on sediment transport over deltaic tidal flats  

NASA Astrophysics Data System (ADS)

Tidal flats at a river mouth feature estuarine and fluvial processes that distinguish them from tidal flats without river discharge. We combine field observations and a numerical model to investigate hydrodynamics and sediment transport on deltaic tidal flats at the mouth of the Skagit River, in Puget Sound, WA, during the spring freshet. River discharge over tidal flats supplies a mean volume flux, freshwater buoyancy, and suspended sediment. Despite the shallow water depths, strong horizontal density fronts and stratification develop, resulting in a baroclinic pressure gradient and tidal variability in stratification that favor flood-directed bottom stresses. In addition to these estuarine processes, the river discharge during periods of low tide drains through a network of distributary channels on the exposed tidal flats, with strongly ebb-directed stresses. The net sediment transport depends on the balance between estuarine and fluvial processes, and is modulated on a spring-neap time scale by the tides of Puget Sound. We find that the baroclinic pressure gradient and periodic stratification enhance trapping of sediment delivered by the river on the tidal flats, particularly during neap tides, and that sediment trapping also depends on settling and scour lags, particularly for finer particles. The primary means of moving sediment off of the tidal flats are the high velocities and stresses in the distributary channels during late stages of ebbs and around low tides, with sediment export predominantly occurring during spring low tides that expose a greater portion of the flats. The 3-d finite volume numerical model was evaluated against observations and had good skill overall, particularly for velocity and salinity. The model performed poorly at simulating the shallow flows around low tides as the flats drained and river discharge was confined to distributary channels, due in part to limitations in grid resolution, seabed sediment and bathymetric data, and the wetting-and-drying scheme. Consequently, the model predicted greater sediment retention on the flats than was observed.

Ralston, David K.; Geyer, W. Rockwell; Traykovski, Peter A.; Nidzieko, Nicholas J.

2013-06-01

277

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

278

Fluvial connectivity and climate: A comparison of channel pattern and process in two climatically contrasting fluvial sedimentary systems in South Africa  

NASA Astrophysics Data System (ADS)

The aim of this research was to investigate the dynamics of valley formation, sediment delivery and channel pattern in two climatically contrasting fluvial sedimentary systems in South Africa. Each system comprised a network of headwater valley fills and floodplains underlain by sedimentary Karoo Supergroup rocks that are intersected by resistant dolerite dykes and sills. The Seekoei River Floodplain and Gordonville valley fill site in the Great Karoo, however, experience less than half the annual precipitation of the Nsonge River Floodplain and Hlatikhulu valley fill in the KwaZulu-Natal Drakensberg Foothills. Furthermore, rainfall is more variable in the Karoo. Despite climatic differences, headwater valley fills were geomorphically similar. In contrast, floodplains in the two regions were vastly different, even when the same downstream control (a resistant dolerite intrusion crossing the drainage line) was considered. Upstream of a dolerite dyke, the Nsonge River is highly sinuous and located in a wide floodplain that has been carved by lateral planation of the underlying bedrock. In comparison, the Seekoei River, located upstream of a dolerite sill, is discontinuous and characterized by floodouts and avulsing distributaries that undergo periods of bedrock incision, followed by infilling.It is likely that this disparity is caused by the inability of infrequent, unsustained flows to develop meanders and, thus, adjust the channel planform to changes in discharge, sediment load and valley slope. Flow variability, thus, exercises a strong control on channel pattern and causes floodouts in headwater settings and the semi-arid Karoo floodplain. As a result, sediment transport in the Seekoei River is likely to be episodic, and net retention of sediment in the semi-arid floodplain is greater than in the sub-humid Nsonge River Floodplain, where sediment depth is limited.

Grenfell, S. E.; Grenfell, M. C.; Rowntree, K. M.; Ellery, W. N.

2014-01-01

279

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

280

Spatio-temporal variability and rates of fluvial bedload transport in steep mountain catchments in western Norway  

NASA Astrophysics Data System (ADS)

The timing and rate of fluvial bedload transport are of central importance within sediment budget studies and in many applications in river science and engineering. Bedload transport rates are very difficult to measure and, in many sites, only suspended load and solute data are included in sediment budget studies. During four years (2010 - 2013) detailed field measurements with portable impact sensors as a non-invasive technique for indirectly determining fluvial bedload transport intensity were conducted at several selected channel stretches within two instrumented and supply-limited drainage basin systems (Erdalen and Bødalen) in the steep fjord landscape in western Norway. The selected stream test stretches where impact sensor field measurements were conducted were located (i) downstream of steep channels in headwater areas of the two drainage basin systems Erdalen and Bødalen, (ii) downstream of selected stream channel segments with temporary in-channel storage of bedload material in Erdalen and Bødalen and (iii) at the outlets of the two drainage basin systems Erdalen and Bødalen. The collected impact sensor field data were calibrated with laboratory flume experiments and were combined with field data from continuous discharge monitoring, repeated surveys of channel morphometry and sediment texture, particle tracer measurements, Helley-Smith samplings, underwater videofilming and biofilm analyses. The combination of methods and techniques applied provides detailed insights into the spatio-temporal variability and rates of fluvial bedload transport within Erdalen and Bødalen. Fluvial bedload transport in steep headwater streams is strongly related to sediment delivery from slopes, especially through fluvial transfers in small creeks draining the slope systems and through snow avalanches in spring and debris flows in fall. Channel reaches with temporary in-channel storage of bedload material in the middle parts of the Erdalen and Bødalen drainage basin systems can modify this temporal pattern of fluvial bedload transport. The measured bedload yield in Bødalen is five times higher than the bedload yield in Erdalen which reflects a valley-morphometric determined higher level of slope-channel coupling in Bødalen than in the Erdalen drainage basin system.

Beylich, Achim A.; Laute, Katja

2014-05-01

281

Ground Penetrating Radar Field Studies of Planetary Analog Geologic Settings: Impact Ejecta, Volcanics, and Fluvial Terrains  

NASA Astrophysics Data System (ADS)

Ground-Penetrating Radar (GPR) data from terrestrial analog environments can help constrain models for evolution of the lunar and martian surfaces, aid in interpretation of orbital SAR data, and help predict what might be encountered in the subsurface during future landed scientific or engineering operations. Results and interpretations presented here from impact ejecta (Barringer Meteorite Crater), volcanic deposits (Northern Arizona cinders overlying lavas, columnar-jointed Columbia River flood basalts, Hawaii lava flows), and terrains influenced by fluvial-related activity (channeled scablands megaflood bar, Mauna Kea glacio-fluvial deposits) focus on defining the radar "fingerprint" of geologic materials and settings that may be analogous to those found on the Moon and Mars. The challenge in using GPR in geologic investigations is the degree to which different geologic features and processes can be uniquely identified and distinguished in the data. Our approach to constraining this is to qualitatively and quantitatively characterize GPR signatures of different geological environments and to compare them with "ground-truth" observations of subsurface exposures immediately adjacent or subjacent to our GPR transects. Several sites were chosen in each field area based on accessibility, visual access to the subsurface, and presence of particular geologic features of interest. The interpreted distribution of blocks in impact ejecta at Meteor Crater, using a 400 MHz antenna (wavelength of 75 cm) is 1.5-3 blocks per m^3 in the upper 1 m (and 0.5-1 blocks per m^3 in the upper two meters), which is close to the in situ measured block distribution of 2-3 blocks larger than 0.25-0.30 m per m^3. This is roughly the detection limit to be expected from the ?/3 resolution approximation of radar wavelength and indicates that the 400 MHz GPR is characterizing the block population in ejecta. While megaflood bar deposits are also reflector-rich, individual reflectors are in general more easily distinguished. At multiple sites, cinders appear smoothly, regularly layered, and allow for excellent GPR penetration. Consequently, the often rough relief of underlying lava flows is discernable, allowing thickness and volume estimates to be made, as well as giving some idea of structure within/on the buried flow. Alternations of massive and clinkery horizons within a'a' flows are detected, as are features representing the interface of overlapping pahoehoe flows (likely due to relatively high relief and fracturing associated with squeeze-ups, etc). Accumulations of gravel, pebbles, and fines derived from lavas and cinders and emplaced by alluvial and mass-wasting processes (along the margins of Apollo Valley, Mauna Kea) appear similar to the pure cinders, as it is likely the same porosity and grain-size characteristics that cause layered GPR reflections. In any case, such layers allow interpretation of how successive events filled in surface relief of the underlying (lava) substrate. GPR data of the interior fill of western Apollo Valley reveals relatively flat reflectors in the along-valley direction and inter-fingering, pinching-out, and dome- and trough-shaped reflectors in the cross-valley direction, indicating accumulation by multiple overlapping lobes coming down the valley, possibly due to multiple fluvial events over time.

Russell, P. S.; Grant, J. A.; Carter, L. M.; Garry, W.; Williams, K. K.; Morgan, G. A.; Daubar, I.; Bussey, B.

2012-12-01

282

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

NASA Astrophysics Data System (ADS)

In deeply incised, high-elevation orogens, such as the Himalaya, it is challenging to quantify the contribution of glaciers to long-term erosion and exhumation due to vigorous fluvial erosion and mass wasting. This is especially true for the humid sectors of the orogen. In the Himalaya, the majority of studies has been conducted in internal arid sectors of the orogen, where present-day ice coverage is low and glacial landforms and deposits are well preserved. The Chandra Valley of the greater Lahul area (NW-Himalaya), situated between the southern front of the range (bulk precipitation during summer) and the more arid Trans-Himalaya to the north (most precipitation during winter) is sensitive to fluctuations of the Indian Summer Monsoon and the Westerlies. In this region we intend to determine spatial and temporal variations in valley incision through fluvial and glacial erosion on different timescales by combining information obtained from cosmogenic radionuclide (CRN) dating of glacially-carved and striated surfaces, low-temperature thermochronometers, field mapping and morphometric analysis. A prominent feature in the upper Chandra Valley, also the headwater region of the Chenab River, is a large knickpoint in the present-day channel profile of the Chandra/Chenab River at an elevation of ~3900 m asl. This knickpoint spatially coincides with (1) a pronounced change in AFT ages along the course of the valley; (2) the joining of a tributary where one of the largest glaciers in the entire area is found; (3) a significant lithological break; and (4) a steep climatic gradient that accompanies the northward turn of the valley. Further knickpoints were found in tributary valleys of the Chandra Valley at approximately the same elevation of ~3900 m asl. Our field observations and preliminary CRN data suggest extensive glacial coverage of the upper Chandra Valley. Based on field evidence the minimum ice thicknesses for the main trunk glacier in the Chandra Valley must have been at least 700 m above the present-day valley bottom until ~15 ka. Our data confirm previous glacial chronological work in this area that also proposed that deglaciation of the Chandra Valley must have been rapid and accomplished within 15 ka, but additionally shows that the late glacial ice cover in the upper Chandra was more extensive than previously thought and also reached the Spiti Valley. Combining all preliminary results and observations, we hypothesize that glacial carving has been the first-order erosional agent during the Quaternary of all regions in Lahul above an elevation of 4100 m asl. Apatite fission-track ages suggest slower erosional exhumation in the more arid upper Chandra Valley. In this context a former blocking of the valley by the Bara Shigri glacier is possible and glacial processes may have outpaced fluvial erosion in the upper part of the Chandra Valley.

Eugster, P.; Scherler, D.; Thiede, R. C.; Codilean, A.; Strecker, M. R.

2013-12-01

283

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

284

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 (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: 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.

Rice, J., Jr.; Christensen, P.; Malin, M.; McEwen, A.; Ruff, S.

2003-04-01

285

Creating High Quality DEMs of Large Scale Fluvial Environments Using Structure-from-Motion  

NASA Astrophysics Data System (ADS)

During the past decade, advances in survey and sensor technology have generated new opportunities to investigate the structure and dynamics of fluvial systems. Key geomatic technologies include the Global Positioning System (GPS), digital photogrammetry, LiDAR, and terrestrial laser scanning (TLS). The application of such has resulted in a profound increase in the dimensionality of topographic surveys - from cross-sections to distributed 3d point clouds and digital elevation models (DEMs). Each of these technologies have been used successfully to derive high quality DEMs of fluvial environments; however, they often require specialized and expensive equipment, such as a TLS or large format camera, bespoke platforms such as survey aircraft, and consequently make data acquisition prohibitively expensive or highly labour intensive, thus restricting the extent and frequency of surveys. Recently, advances in computer vision and image analysis have led to development of a novel photogrammetric approach that is fully automated and suitable for use with simple compact (non-metric) cameras. In this paper, we evaluate a new photogrammetric method, Structure-from-Motion (SfM), and demonstrate how this can be used to generate DEMs of comparable quality to airborne LiDAR, using consumer grade cameras at low costs. Using the SfM software PhotoScan (version 0.8.5), high quality DEMs were produced for a 1.6 km reach and a 3.3 km reach of the braided Ahuriri River, New Zealand. Photographs used for DEM creation were acquired from a helicopter flying at 600 m and 800 m above ground level using a consumer grade 10.1mega-pixel, non-metric digital camera, resulting in object space resolution imagery of 0.12 m and 0.16 m respectively. Point clouds for the two study reaches were generated using 147 and 224 photographs respectively, and were extracted automatically in an arbitrary coordinate system; RTK-GPS located ground control points (GCPs) were used to define a 3d non-linear transformation to convert the point clouds to the absolute NZTM coordinate system, with average errors of 0.06 m in the horizontal and 0.11 m in the vertical dimensions. The final point clouds extracted had typical point spacings of 0.25 m, well above the metric resolution of airborne LiDAR. To improve data handling, the final point cloud was decimated to point spacings of 0.5 m using a recently developed gridding procedure (Rychkov, Brasington, & Vericat, 2012), and finally converted into a DEM using a Delaunay constrained TIN in ArcGIS. Results reveal SfM's ability to produce high quality terrain products of large scale fluvial environments that can outperform LiDAR, and can potentially compare with TLS. PhotoScan offers a straightforward method to generate, transform, and export DEMs that requires little user knowledge of photogrammetric processes. Further, the affordability and reduced field work offer low budget researchers the ability to produce repeat surveys for in-depth temporal studies. Funding supported by the New Zealand Department of Conservation.

Javernick, L. A.; Brasington, J.; Caruso, B. S.; Hicks, M.; Davies, T. R.

2012-12-01

286

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

287

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

288

Exploring controls on valley spacing in higher order fluvial channels with the CHILD Model  

NASA Astrophysics Data System (ADS)

Across a wide range of landscapes the ratio between the width of a mountain and the distance separating trunk channels exiting the mountain front (generally termed the valley spacing ratio) has been observed to be fairly constant, but the reasons for its uniformity are not well understood. Recent work also suggests that the ratio between the spacing of valleys and the characteristic length, or distance from the divide to where hillslopes transition to fluvial channels, (here termed the characteristic length ratio) is relatively constant in first order channels. We propose that the characteristic length ratio of higher order channels is a primary control on the valley spacing ratio. We explore how these ratios are linked together and the variables that may affect both of these ratios using the CHILD numerical landscape evolution model. Previous studies observed a linear relationship between valley spacing and characteristic length in first order channels, and we find that the relationship remains linear in higher order channels, demonstrating that the competition between hillslope and fluvial processes influences landscape morphology at all scales. Moreover, we also find that the characteristic length ratio for a given order channel is fairly robust and does not appear to be impacted by model initial conditions (such as initial topography) and precipitation patterns (such as orographic precipitation). For a fixed domain in our model, although the characteristic length may vary, the valley spacing ratio remains in the range observed in real landscapes. The ratio of mountain width to valley spacing remains relatively constant because the order of trunk channels varies with the characteristic length. In other words, for a given domain size (or mountain range width), a larger characteristic length can produce lower order trunk channels but with the same spacing value as higher order trunk channels with a smaller characteristic length. This competition between channel order and characteristic length may be one of the reasons why the valley spacing ratio is relatively constant across diverse natural settings. However, our model results also show that initial and boundary conditions may affect the maximum stream order in a domain, even though they do not affect valley spacing. As a result, the valley spacing ratio is more variable than the characteristic length ratio. For example, we find that more pronounced orographic precipitation patterns, or much steeper initial surfaces, can lead to more linear streams, less tributary branching and lower order trunk channels. In this case, the ratio between valley spacing and characteristic length remains the same, whereas the ratio between mountain width and valley spacing increases, but still remains within the observed range in natural landscapes. Finally, DEM analysis of three study areas supports our numerical results.

Han, J.; Gasparini, N. M.; Johnson, J. P.

2013-12-01

289

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

290

A Pleistocene coastal alluvial fan complex produced by Middle Pleistocene glacio-fluvial processes  

NASA Astrophysics Data System (ADS)

A coarse-grained alluvial fan sequence at Lipci, Kotor Bay, in western Montenegro, provides a sedimentary record of meltwater streams draining from the Orjen Massif (1,894 m a.s.l.) to the coastal zone. At Lipci sedimentary evidence and U-series ages have been used alongside offshore bathymetric imagery and seismic profiles to establish the size of the fan and constrain the nature and timing of its formation. Establishing the depositional history of such coastal fans is important for our understanding of cold stage sediment flux from glaciated uplands to the offshore zone, and for exploring the impact of sea level change on fan reworking. There is evidence of at least four phases of Pleistocene glaciation on the Orjen massif, which have been U-series dated and correlated to MIS 12, MIS 6, MIS 5d-2 and the Younger Dryas. A series of meltwater channels delivered large volumes of coarse- and fine-grained limestone sediment from the glaciated uplands into the Bay of Kotor. At the southern margin of the Orjen massif, a series of large (>700 m long) alluvial fans has developed. Some of these extend offshore for up to 600 m. Lipci fan lies downstream of end moraines in the valley immediately above, which were formed by an extensive outlet glacier of the Orjen ice cap during MIS 12. The terrestrial deposits are part of the fan apex (50 m a.s.l.) that lies at the foot of a steep bedrock channel, but the majority of the fan is now more than 25 m below sea level. The terrestrial fan sediments are strongly cemented by multiple generations of calcite precipitates: the oldest U-series ages are infinite indicating that the fan is >350 ka in age. These ages are in agreement with alluvial sedimentary evidence and U-series ages from other fluvial units on Mount Orjen. The terrestrial portion of the Lipci fan surface contains several channels. These are well preserved due to cementation with calcium carbonate. Submarine imagery indicates that the now submerged portion of the fan also contains deeply incised (up to 10 m) channels which are similar in morphology to those exposed onshore. It is likely that strong cementation of the fan sediments, and associated channel forms, has protected them from coastal erosion during several regression-transgression cycles. These records provide important opportunities to correlate the Pleistocene terrestrial glacial and fluvial records with the marine archive.

Adamson, Kathryn; Woodward, Jamie; Hughes, Philip; Giglio, Federico; Del Bianco, Fabrizio

2014-05-01

291

El Instituto de Ciencias del Mar y Limnologa, organiza el "Da Mundial del Agua 2012", un evento de Puertas Abiertas para celebrar "El Agua y la seguridad alimentara" tema  

E-print Network

El Instituto de Ciencias del Mar y Limnología, organiza el "Día Mundial del Agua 2012", un evento de Puertas Abiertas para celebrar "El Agua y la seguridad alimentaría" tema orientado para llamar la atención internacional sobre la alimentación y su relación con el agua. El lema con el que la ONU ha

Islas, León

292

In Situ U-Th-Pb Geochronology of Detrital Shocked Monazite in Pleistocene Fluvial Deposits Along the Vaal River, South Africa  

NASA Astrophysics Data System (ADS)

Here we report microstructural and in situ U-Th-Pb age data for detrital shocked monazite grains found in a Pleistocene (ca. 1.6 Ma) fluvial deposit near Windsorton South Africa, 500 km downstream from the Vredefort Dome.

Cintrón, N. O.; Cavosie, A. J.; Gibbon, R. J.; Radovan, H. A.; Moser, D. E.; Wooden, J.

2011-03-01

293

Using the landscape morphometric context to resolve spatial patterns of submerged macrophyte communities in a fluvial lake  

Microsoft Academic Search

This study investigates the spatial heterogeneity of macrophyte communities in a fluvio-lacustrine landscape. We analysed\\u000a the importance of the geomorphological point\\/bay pattern in structuring aquatic plant assemblages inside a 20-km-long littoral\\u000a segment of a large fluvial lake. The abundance of 21 macrophyte species was surveyed in 232 quadrats along 24 transects perpendicular\\u000a to the lakeshore. Two contrasting plant communities were

Rosalie Léonard; Pierre Legendre; Martin Jean; André Bouchard

2008-01-01

294

Toward the Validation of Depth-Averaged Three Dimensional, Rans Steady-State Simulations of Fluvial Flows at Natural Scale  

Microsoft Academic Search

Simulations of fluvial flows are strongly influenced by geometric complexity and overall uncertainty on measured flow variables, including those assumed to be well known boundary conditions. Often, 2D steady-state models are used for computational simulations of flows at the scale of natural rivers. Such models have been successfully incorporated in iRIC (formerly MD_SWMS), one of the widely used quasi-3D CFD

P. A. Mateo Villanueva; M. Hradisky

2010-01-01

295

High-Temperature Tolerances of Fluvial Arctic Grayling and Comparisons with Summer River Temperatures of the Big Hole River, Montana  

Microsoft Academic Search

Critical thermal maximum (CTM) and resistance time to high temperature were determined for juvenile Arctic grayling Thymallus arcticus from the fluvial population of the Big Hole River, Montana. Grayling were tested after acclimation to 8.4, 16.0, and 20.0°C. Thermal tolerances increased with acclimation temperatures; mean CTM was 26.4°C for the 8.4°C acclimation group, 28.5°C for the 16.0°C group, and 29.3°C

S. C. Lohr; P A. Byorth; C. M. Kaya; W. P. Dwyer

1996-01-01

296

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

297

Fluvial incision into bedrock: Insights from morphometric analysis and numerical modeling of gorges incising glacial hanging valleys (Western Alps, France)  

NASA Astrophysics Data System (ADS)

Bedrock gorges incising glacial hanging valleys potentially allow measurements of fluvial bedrock incision in mountainous relief. Using digital elevation models, topographic maps, and field reconnaissance, we identified and characterized 30 tributary hanging valleys incised by gorges near their confluence with trunk streams in the Romanche watershed, French Western Alps. Longitudinal profiles of these tributaries are all convex and have abrupt knickpoints at the upper limit of oversteepened gorge reaches. We reconstructed initial glacial profiles from glacially polished bedrock knobs surrounding the gorges in order to quantify the amount of fluvial incision and knickpoint retreat. From morphometric analyses, we find that mean channel gradients and widths, as well as knickpoint retreat rates, display a drainage area dependence modulated by bedrock lithology. However, there appears to be no relation between horizontal retreat and vertical downwearing of knickpoints. Assuming a postglacial origin of these gorges, our results imply high postglacial fluvial incision (0.5-15 mm yr-1) and knickpoint retreat (1-200 mm yr-1) rates that are, however, consistent with previous estimates. Numerical modeling was used to test the capacity of different fluvial incision models to predict the inferred evolution of the gorges. Results from simple end-member models suggest transport-limited behavior of the bedrock gorges. A more sophisticated model including dynamic width adjustment and sediment-dependent incision rates predicts present-day channel geometry only if a significant supply of sediment from the gorge sidewalls (˜10 mm yr-1) is triggered by gorge deepening, combined with pronounced inhibition of bedrock incision by sediment transport and deposition.

Valla, Pierre G.; van der Beek, Peter A.; Lague, Dimitri

2010-06-01

298

Depositional mechanisms controlling formation of coarse fluvial conglomerates in the lower triassic continental red beds of middle europe  

Microsoft Academic Search

Coarse fluvial conglomerates containing numerous cobbles and boulders occur in various formations within the Lower Triassic continental red beds of Middle Europe. The rudites mainly originate as longitudinal gravel bars in highly-braided river systems with narrowly-spaced and straight to slightly sinuous channels. The high-energy stream sedimentation and the frequent and rapid lateral shifting of the watercourses control origin, distribution and

Detlef Mader

299

Depositional mechanisms controlling formation of coarse fluvial conglomerates in the lower triassic continental red beds of middle europe  

Microsoft Academic Search

Coarse fluvial conglomerates containing numerous cobbles and boulders occur in various formations within the Lower Triassic continental red beds of Middle Europe. The rudites mainly originate as longitudinal gravel bars in highly-braided river systems with narrowly-spaced and straight to slightly sinuous channels. The high-energy stream sedimentation and the frequent and rapid lateral shifting of the watercourses control origin, distribution and

Detlef Mader

1985-01-01

300

Fluvial diffluence episodes reflected in the Pleistocene tufa deposits of the River Piedra (Iberian Range, NE Spain)  

NASA Astrophysics Data System (ADS)

The Pleistocene deposits of the valley of the River Piedra (NE Spain) are represented by thick tufas with small amounts of detrital material; the development of these deposits correlates with marine isotopic stages 9, 7, 6, and 5. The sedimentary scenario in which they formed mostly corresponded to stepped fluvial systems with barrage-cascade and associated dammed areas separated by low gradient fluvial stretches. Mapping and determining the sedimentology and chronology of these deposits distinguished two main episodes of fluvial diffluence that originated as a result of the temporary blockage of the river — a consequence of the vertical growth of tufa barrages in the main channel. In both episodes, water spilt out toward a secondary course from areas upstream of barrages where the water level surpassed the height of the divide between the main and secondary course. As a consequence, extensive and distinct tufa deposits with very varied facies formed over a gently inclined area toward and, indeed, within the secondary course. The hydrology of this secondary course was episodic, fed only by surface water. The two diffluence episodes detected occurred during MIS 7 and 7-6 and were interrupted by incision events, reflected by detrital deposits at the base of each tufa sedimentation stage in the main channel. Incision, which caused the breakage of the barrages, allowed water to again flow through the main channel. No evidence of diffluence was seen in any younger (MIS 5 to present-day) tufa deposits. The proposed diffluence model might help explain other carbonate fluvial systems in which (1) tufas appear in areas with no permanent water supply, and (2) tufas are absent over extensive areas despite conditions favourable to their formation.

Vázquez-Urbez, M.; Pardo, G.; Arenas, C.; Sancho, C.

2011-01-01

301

Fluvial transport and surface enrichment of arsenic in semi-arid mining regions: examples from the Mojave Desert, California.  

PubMed

As a result of extensive gold and silver mining in the Mojave Desert, southern California, mine wastes and tailings containing highly elevated arsenic (As) concentrations remain exposed at a number of former mining sites. Decades of weathering and erosion have contributed to the mobilization of As-enriched tailings, which now contaminate surrounding communities. Fluvial transport plays an intermittent yet important and relatively undocumented role in the migration and dispersal of As-contaminated mine wastes in semi-arid climates. Assessing the contribution of fluvial systems to tailings mobilization is critical in order to assess the distribution and long-term exposure potential of tailings in a mining-impacted environment. Extensive sampling, chemical analysis, and geospatial mapping of dry streambed (wash) sediments, tailings piles, alluvial fans, and rainwater runoff at multiple mine sites have aided the development of a conceptual model to explain the fluvial migration of mine wastes in semi-arid climates. Intense and episodic precipitation events mobilize mine wastes downstream and downslope as a series of discrete pulses, causing dispersion both down and lateral to washes with exponential decay behavior as distance from the source increases. Accordingly a quantitative model of arsenic concentrations in wash sediments, represented as a series of overlapping exponential power-law decay curves, results in the acceptable reproducibility of observed arsenic concentration patterns. Such a model can be transferable to other abandoned mine lands as a predictive tool for monitoring the fate and transport of arsenic and related contaminants in similar settings. Effective remediation of contaminated mine wastes in a semi-arid environment requires addressing concurrent changes in the amounts of potential tailings released through fluvial processes and the transport capacity of a wash. PMID:22718027

Kim, Christopher S; Stack, David H; Rytuba, James J

2012-07-01

302

Two-dimensional coupled mathematical modeling of fluvial processes with intense sediment transport and rapid bed evolution  

Microsoft Academic Search

Alluvial rivers may experience intense sediment transport and rapid bed evolution under a high flow regime, for which traditional\\u000a decoupled mathematical river models based on simplified conservation equations are not applicable. A two-dimensional coupled\\u000a mathematical model is presented, which is generally applicable to the fluvial processes with either intense or weak sediment\\u000a transport. The governing equations of the model comprise

Zhiyuan Yue; Zhixian Cao; Xin Li; Tao Che

2008-01-01

303

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

304

Artculo publicado en "Patrimonio Geolgico de Andaluca". Eds. Durn y Nuche. 147-149. 1999 AGUAS DE LANJARN  

E-print Network

Artículo publicado en "Patrimonio Geológico de Andalucía". Eds. Durán y Nuche. 147-149. 1999 AGUAS DE LANJAR�N José Benavente Herrera y Antonio Castillo Martín Instituto del Agua de la Universidad de Granada Lanjarón y Agua. Estas dos palabras suelen ir inevitablemente asociadas en nuestros pensamientos

Castillo, Antonio

305

Proteja su almuerzo de los grmenes Lvese las manos con agua caliente y jabn antes de preparar el almuerzo.  

E-print Network

Proteja su almuerzo de los gérmenes · Lávese las manos con agua caliente y jabón antes de preparar botella térmica de boca ancha. Vierta agua hirviendo en la botella para calentar el interior. Luego caliente el alimento a 1650 F. Vacíe el agua caliente de la bo- tella y vierta en su interior el alimento

306

UTILIZACIN DE SIG PARA LA ELABORACIN DE UN PLAN DE MANEJO DE AGUAS DE ESCORRENTAS (MS4S)  

E-print Network

UTILIZACI�N DE SIG PARA LA ELABORACI�N DE UN PLAN DE MANEJO DE AGUAS DE ESCORRENTÍAS (MS4S) Roy Ruiz Vélez Research Assistant II Instituto de Investigaciones Sobre Recursos de Agua y el actualmente se encuentra en la elaboración del Plan de Manejo de Aguas de Escorrentías para el Municipio de

Gilbes, Fernando

307

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

308

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

309

Implications of sedimentological studies for environmental pollution assessment and management: Examples from fluvial systems in North Queensland and Western Australia  

NASA Astrophysics Data System (ADS)

Sedimentology is of increasing importance in environmental research, particularly environmental pollution studies, where past trends in environmental processes need to be combined with data on present conditions to predict likely future changes—the past and present as a key to the future. Two examples are used to illustrate the role of sedimentology in assessing the influence of major processes on the transport, accumulation, deposition and modification of contaminants in fluvial/estuarine systems and in developing environmental management plans. Example 1 shows that when assessing nutrient behaviour in fluvial/estuarine depositional settings, it is important to examine the partitioning of phosphorus between grain size fractions to evaluate the sedimentological processes which control the dispersion and trapping of these contaminants. Example 2 shows that in studies of anthropogenic metal inputs to modern depositional settings, lateral and stratigraphic trends in sediment texture and mineralogy should be examined, in addition to trends in metal loads and evaluation of the prevailing physical, chemical and biological processes that may influence metal mobility and dispersion. Clearly, basic sedimentological data should form part of any assessment of potentially contaminated sites and part of investigations into the dispersion and trapping of contaminants in fluvial systems. These data are also required for rational environmental management to ensure that planning decisions are compatible with natural environmental constraints.

Eyre, Bradley; McConchie, David

1993-05-01

310

Fluvial transport potential of shed and root-bearing dinosaur teeth from the late Jurassic Morrison Formation  

PubMed Central

Shed dinosaur teeth are commonly collected microvertebrate remains that have been used for interpretations of dinosaur feeding behaviors, paleoecology, and population studies. However, such interpretations may be biased by taphonomic processes such as fluvial sorting influenced by tooth shape: shed teeth, removed from the skull during life, and teeth possessing roots, removed from the skull after death. As such, teeth may behave differently in fluvial systems due to their differences in shape. In order to determine the influence of fluvial processes on the preservation and distribution of shed and root-bearing dinosaur teeth, the hydrodynamic behaviors of high-density urethane resin casts of shed and root-bearing Allosaurus and Camarasaurus teeth were experimentally tested for relative transport distances at increasing flow velocities in an artificial fluviatile environment. Results show that tooth cast specimens exhibited comparable patterns of transport at lower velocities, though the shed Camarasaurus teeth transported considerably farther in medium to higher flow velocities. Two-Way ANOVA tests indicate significant differences in the mean transport distances of tooth casts oriented perpendicular to flow (p < 0.05) with varying tooth morphologies and flow velocities. The differences exhibited in the transportability of shed and root-bearing teeth has important implications for taphonomic reconstructions, as well as future studies on dinosaur population dynamics, paleoecology, and feeding behaviors. PMID:24765581

Coenen, Jason J.; Noto, Christopher R.

2014-01-01

311

Fluvial transport potential of shed and root-bearing dinosaur teeth from the late Jurassic Morrison Formation.  

PubMed

Shed dinosaur teeth are commonly collected microvertebrate remains that have been used for interpretations of dinosaur feeding behaviors, paleoecology, and population studies. However, such interpretations may be biased by taphonomic processes such as fluvial sorting influenced by tooth shape: shed teeth, removed from the skull during life, and teeth possessing roots, removed from the skull after death. As such, teeth may behave differently in fluvial systems due to their differences in shape. In order to determine the influence of fluvial processes on the preservation and distribution of shed and root-bearing dinosaur teeth, the hydrodynamic behaviors of high-density urethane resin casts of shed and root-bearing Allosaurus and Camarasaurus teeth were experimentally tested for relative transport distances at increasing flow velocities in an artificial fluviatile environment. Results show that tooth cast specimens exhibited comparable patterns of transport at lower velocities, though the shed Camarasaurus teeth transported considerably farther in medium to higher flow velocities. Two-Way ANOVA tests indicate significant differences in the mean transport distances of tooth casts oriented perpendicular to flow (p < 0.05) with varying tooth morphologies and flow velocities. The differences exhibited in the transportability of shed and root-bearing teeth has important implications for taphonomic reconstructions, as well as future studies on dinosaur population dynamics, paleoecology, and feeding behaviors. PMID:24765581

Peterson, Joseph E; Coenen, Jason J; Noto, Christopher R

2014-01-01

312

Mechanisms and timescales of fluvial activity at Mojave and other young Martian craters  

NASA Astrophysics Data System (ADS)

Crater, and five other relatively young Late Hesperian to Amazonian-age Martian craters exhibit channelized alluvial fans that are sourced from bedrock-eroded catchments. These catchments emerge from the crests of sloping surfaces, suggesting a formation mechanism that involved precipitation. The evidence for fluvial activity at all six craters is restricted to their interiors and the immediate surrounding regions. Detailed mapping at Mojave reveals the highest density of channels, catchments and fans interior to the crater. Similar landforms are identified outside of the crater, but not beyond ~200 km from the rim. Irregular pits on the floor of Mojave, interpreted as degassing structures from hot impact melt, directly superpose several fan surfaces, and partly destroy the fan toes. This suggests that sediment was mobilized immediately after crater formation, while the crater was still hot. Based on the patterns and timing of channel-fan development at all six craters we favor several hypotheses for the precipitation mechanism: (1) snowfall and melt on young, hot impact craters, (2) impact plume precipitation, and (3) degassing of volatiles from impact melt terrain. Scenario (1) suggests a different global or regional climate relative to modern conditions, requiring equatorial and midlatitude snowfall accumulation. Scenarios (2) and (3) do not necessarily require unique climate conditions, as water may have been mobilized from the target or the impactor.

Goddard, Kate; Warner, Nicholas H.; Gupta, Sanjeev; Kim, Jung-Rack

2014-03-01

313

Mechanisms and Timescales of Fluvial Activity at Mojave and other Young Martian Craters  

NASA Astrophysics Data System (ADS)

Mojave crater, and five other relatively young Late Hesperian to Amazonian-age martian craters exhibit channelized alluvial fans that are sourced from bedrock-eroded catchments. These catchments emerge from the crests of sloping surfaces, suggesting a formation mechanism that involved precipitation. The evidence for fluvial activity at all six craters is restricted to their interiors and the immediate surrounding regions. Detailed mapping at Mojave reveals the highest density of channels, catchments and fans interior to the crater. Similar landforms are identified outside of the crater, but not beyond ~200 km from the rim. Irregular pits on the floor of Mojave, interpreted as degassing structures from hot impact melt, directly superpose several fan surfaces, and partly destroy the fan toes. This suggests that sediment was mobilized immediately after crater formation, while the crater was still hot. Based on the patterns and timing of channel-fan development at all six craters we favor several hypotheses for the precipitation mechanism: (1) snowfall and melt on young, hot impact craters, (2) impact plume precipitation, and (3) degassing of volatiles from impact melt terrain. Scenario (1) suggests a different global or regional climate relative to modern conditions, requiring equatorial and mid-latitude snowfall accumulation. Scenarios (2) and (3) do not necessarily require unique climate conditions, as water may have been mobilized from the target or the impactor.

Goddard, Kate; Warner, Nicholas; Gupta, Sanjeev; Kim, Jung-Rack

2014-05-01

314

Water and nutrient transport on a heavy clay soil in a fluvial plain in the Netherlands.  

PubMed

In flat areas, transport of dissolved nutrients by water through the soil matrix to groundwater and drains is assumed to be the dominant pathway for nutrient losses to ground- and surface waters. However, long-term data on the losses of nutrients to surface water and the contribution of various pathways is limited. We studied nutrient losses and pathways on a heavy clay soil in a fluvial plain in The Netherlands during a 5-yr period. Average annual nitrogen (N) and phosphorus (P) losses to surface water were 15.1 and 3.0 kg ha(-1) yr(-1), respectively. Losses were dominated by particulate N (50%) and P (70%) forms. Rapid discharge through trenches was the dominant pathway (60-90%) for water and nutrient transport. The contribution of pipe drains to the total discharge of water and nutrients was strongly related to the length of the dry period in the preceding summer. This relationship can be explained by the very low conductivity of the soil matrix and the formation of shrinkage cracks during summer. Losses of dissolved reactive P through pipe drains appear to be dominated by preferential flow based on the low dissolved reactive P concentration in the soil matrix at this depth. Rainfall occurring after manure application played an important role with respect to the annual losses of N and P in spring when heavy rainfall occurred within 2 wk after manure application. PMID:22218191

van der Salm, Caroline; van den Toorn, Antonie; Chardon, Wim J; Koopmans, Gerwin F

2012-01-01

315

New microbioassays based on biomarkers are more sensitive to fluvial water micropollution than standard testing methods.  

PubMed

Recent investigations suggest that, despite lack of lethality in validated bioassays, micropollutants in surface waters could induce sublethal toxicity in sensitive taxa, jeopardizing their biological performance and eventually leading to populations' extinction. A broader array of testing species, the miniaturization of bioassays and the development of reliable biomarkers of damage are sought in order to improve ecological relevance and cost efficiency of environmental monitoring. Our aim is to assess the different sensitivity of validated bioassays and new approaches using biomarkers as sensitive endpoints of toxicity in spores of Polystichum setiferum and Danio rerio embryos. Six water samples were collected in Tagus basin in summer and winter. Samples tested induce no acute toxicity in validated methods (algae growth inhibition and daphnia mobility inhibition). Summer water samples induced acute membrane damage (lipid peroxidation) in Danio rerio embryos and hormetic increases in fern spore mitochondrial activity. One of the samples dramatically reduced mitochondrial activity indicating severe acute sublethal phytotoxicity. All the winter samples induced significant decreases in fern spore mitochondrial activity and membrane damage increases in Danio rerio embryo. Furthermore, three samples induced lethal phytotoxicity in fern spores. We conclude that the new microbioassays show a better sensitivity to fluvial water micropollution and confirm the necessity to test critical life stages such as development and provide cost-efficient methods for environmental monitoring. PMID:23618774

Esteban, S; Fernández Rodríguez, J; Díaz López, G; Nuñez, M; Valcárcel, Y; Catalá, M

2013-07-01

316

Fluvial suspended sediment dynamics: Implications for particulate organic carbon transport modeling  

NASA Astrophysics Data System (ADS)

The effect of fluvial suspended sediment aggregation on the hydrodynamic transport properties of particulate organic carbon (POC) was investigated using a combination of field measurement and numerical modeling. Field-based settling tube experiments were conducted to obtain particle settling velocity frequency distributions of a 4-km-long section of a lake outlet river at two distinct discharge levels (6.8 and 29.7 m3 s-1). Results of field studies conducted in April 2001 and April 2002 showed that the lacustrine settling velocity frequency distributions of suspended particulate matter (SPM) and POC were altered owing to the formation of riverine aggregates having comparatively higher settling velocities. Data suggest that aggregation promoted deposition fluxes of POC; these fluxes were in turn closely tied to the processes that controlled deposition of SPM. Data interpretation was aided by the employment of a hydrodynamic sediment transport model. The approach used to integrate aggregation in the sediment transport simulations represents the interaction of multiple settling velocity mass fractions. Both field data and modeling demonstrated the effect of aggregation on the increase in deposition fluxes of POC.

Bungartz, Heinz; Krüger, Angela; Engelhardt, Christof

2006-10-01

317

Characterizing fluvial systems at basin scale by fuzzy signatures of hydromorphological drivers in data scarce environments  

NASA Astrophysics Data System (ADS)

Despite the relevance of river hydromorphology (HYMO) for integrated water resource management, consistent geomorphic information at the scale of whole river basin is still scarce, especially in emerging economies. In this paper, we propose a new, scalable and globally applicable framework to analyze and classify fluvial systems in data-scarce environments. The framework is based on a data-driven analysis of a multivariate data set of 6 key hydro-morphologic drivers derived using freely available remote-sensing information and several in situ hydrological time series. Core of the framework is a fuzzy classifier that assigns a characteristic signature of HYMO drivers to individual river reaches. We demonstrate the framework on the Red River Basin, a large, trans-boundary river basin in Vietnam and China, where human-induced morphological change, concretely endangering local livelihoods, is contrasted by very limited HYMO information. The derived HYMO information covers spatial scales from the entire basin to individual reaches. It conveys relevant information on subbasin hydro-morphologic characteristic as well as on local geomorphologic forms and processes. The fuzzy classifier successfully distinguishes abrupt from continuous downstream change and spatially dissects the river system in segments with homogeneous hydro-morphologic forcings. Successful numerical modelling of morphologic forms and process rates based on the HYMO signatures indicates that the multivariate, basin-scale classification captures relevant morphological drivers, outperforms an analysis based on local drivers only, and can support river management from diverse, morphology related perspectives over a wide range of scales.

Schmitt, R.; Bizzi, S.; Castelletti, A.

2014-06-01

318

Fluvial backwater zones as filters on source to sink sediment transport (Invited)  

NASA Astrophysics Data System (ADS)

Sediment flux from rivers to oceans is the fundamental driver of fluvio-delatic morphodynamics and continental-margin sedimentation, yet sediment transport across the river to marine boundary remains poorly understood. Rivers near their mouths typically are affected by backwater, a zone of spatial decelerating flow and concave water-surface profile that is transitional between normal flow upstream and static water beyond the shoreline. Deceleration in the backwater zone, as well as spreading of the offshore plume should render rivers highly depositional near their mouths. Field observations have shown, however, that the riverbed within the backwater zones of some rivers (e.g., Mississippi River) show flutes and potholes along the riverbed indicating scour into the underlying substrate. We hypothesize that zones of backwater can transition to zones of drawdown and erosion at high flows. Numerical modeling results show that such a scenario is possible where river plumes spread laterally beyond the shoreline. Model results compare favorably with measurements of river water-surface elevation and velocity over a range of discharges for the lower Mississippi River. Our results suggest that that fluvial sediment export to marine environments can be pulse like, where backwater zones retard sediment export at low flows and enhance sediment export at high flows.

Lamb, M. P.; Nittrouer, J. A.; Mohrig, D. C.; Shaw, J. B.

2010-12-01

319

Evolving fluvial—transitional—marine deposition through the Cambrian sequence of Jordan  

NASA Astrophysics Data System (ADS)

The Cambrian sequence in Jordan crops out in a belt-like pattern extending over more than 300 km from the Arabian-Nubian Shield source rock in the south, located on a stable shelf platform, to the invading southern (Baltic) side of the Tethys seaway. The analysis of the lithofacies association, ichnofossil content, together with the architecture of fluvial and paralic sandstone bodies reveals the development of the depositional environments of the Cambrian deposits of Jordan. The depositional environment evolved from proximal alluvial fans into major sand flats of braided rivers or directly into distal braidplains dominated by 3-D megaripples. In the following depositional phase, various marine environments prevailed including platform carbonates, clastic-, carbonate- and mixed-tidal flats and supratidal sabkhas, and less common lagoons. All these marine, or marine-influenced environments changed back into distal braidplains or sand flats of braided streams. The latter persisted through the remaining period of the Cambrian. The study has revealed that shales containing Cruziana interbedded within the fluviatile sandstone sequence are time markers that can be used for correlation, and could be deposited in a braidplain, if the detrital influx was very low. It is the latter that enabled the Cruziana-producing trilobites to migrate from the sea through river mouths to reach distal braidplains and lagoons.

Amireh, Belal S.; Schneider, Werner; Abed, Abdulkader M.

1994-02-01

320

Fluvial bedrock erosion by sediment in suspension couples hillslope processes and channel evolution  

NASA Astrophysics Data System (ADS)

Computational landscape evolution models that simulate long-term denudation of mountain ranges are often based on the stream-power model for detachment-limited fluvial erosion. When integrated with models for long-term hillslope erosion and sediment transport, the stream-power model predicts realistic landscapes with concave steady-state river profiles. However, the rate of stream-power erosion depends solely on the amount of surface runoff (precipitation) and the channel bed slope. This does not agree well with global estimates of erosion rates based on in-situ produced cosmogenic nuclides, which link high erosion rates to tectonic activity rather than high precipitation rates and topographic relief (von Blankenburg, 2005). As an alternative to the stream-power model, Sklar & Dietrich (2004) have proposed a saltation-abrasion model for river incision by saltating bed load. In the saltation-abrasion model, the sediments in suspension erode the riverbed when grains collide with the bedrock. In this presentation, we show with three-dimensional landscape evolution models that river incision by saltating bed load depends critically on sediment delivery from the un-channelized hillslopes. Such sediment delivery is achieved through landslides in tectonically active regions. The saltation-abrasion model therefore pinpoints the critical processes that potentially explain the observed pattern of global erosion rates that highlight the importance of tectonic activity.

Egholm, D. L.; Knudsen, M. F.

2012-04-01

321

Monitoring of fluvial transport in small upland catchments - methods and preliminary results  

NASA Astrophysics Data System (ADS)

In April 2011 a study was initiated, financed from resources of the Polish National Science Centre, entitled: ‘Rainstorm prediction and mathematic modelling of their environmental and social-economical effects’ (No. NN/306571640). The study, implemented by a Polish-American team, covers meteorological research, including: (1) monitoring of single cell storms developing in various synoptic situations, (2) detection of their movement courses, and (3) estimation of parameters of their rain field. Empirical studies, including hydrological and geomorphological measurements, are conducted in objects researched thoroughly in physiographic terms (experimental catchments) in the Lublin region (SE Poland), distinguished by high frequency of occurrence of the events described. For comparative purposes, studies are also carried out on selected model areas in the lower course of the Mississippi River valley (USA), in a region with high frequency of summer rainstorms. For detailed studies on sediment transport processes during rainstorm events, catchments of low hydrological rank and their sub-catchments in a cascade system were selected. For the basic, relatively uniform geomorpho logical units distinguished this way, erosion and deposition balance of material transported was determined. The aim of work was to determine influence of weather condition on fluvial transport rate in small catchment with low hydrological order

Janicki, Grzegorz; Rodzik, Jan; Chabudzi?ski, ?ukasz; Franczak, ?ukasz; Si?uch, Marcin; St?pniewski, Krzysztof; Dyer, Jamie L.; Ko?odziej, Grzegorz; Maciejewska, Ewa

2014-06-01

322

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

323

Earth, Wind, & Water: studying the dynamic interplay of fluvial and wind channelization processes in the Altiplano-Puna  

NASA Astrophysics Data System (ADS)

Here we describe a novel landscape where wind and fluvial erosion appear to have approximately equal efficiency. The Altiplano-Puna Volcanic Complex (APVC) in South America contains a vast array of ignimbrite sheets, spanning ~1-10 Ma, that exhibit not only fluvial bedrock channels, but also prominently straight and subparallel erosional channels oriented with the dominant wind direction. In certain cases these wind channels are exploited by river channels, and vice versa, suggesting a dynamic interplay of processes that control the topographic evolution of this landscape. Though researchers have observed the presence of wind-eroded channels in the APVC and elsewhere, little is understood about the mechanisms that drive their formation and evolution. Before we can gain a clear mechanistic understanding of how wind channels evolve, however, we seek to better understand and objectively quantify the topographic fabric of these geomorphic features. Towards this end, here we explore whether wind channels can be quantitatively identified from river channels based on topographic data. Apart from helping us to eventually test end-member hypotheses for the formation of wind channels (e.g., longitudinal flow structures controlled by the atmospheric boundary layer vs. an emergent phenomenon akin to the process responsible for longitudinal dune formation), being able to determine wind vs. fluvial channels can help toward interpreting topographic and photographic data from Mars and other planets that have both aeolian and fluvial erosional features. Spectral analysis provides an objective way to identify periodic signals in topographic data. As the aeolian fabric in channelized ignimbrite sheets appears to have a regular spacing, topographic wavelength may provide a metric for discriminating wind from fluvial channels. Here we can start to discern whether wind channels truly exhibit a periodicity, and if so, whether this periodicity is similar between ignimbrites. Using a 30 m ASTER DEM with 2DSpecTools (Perron et al., 2008), a free spectral analysis toolkit for Matlab, we analyze the periodic structure of two stratigraphically comparable ignimbrites, the 3.96 Ma Atana and 4.09 Ma Puripicar, that both show wind lineations but have varying amounts of fluvial erosion. Comparing wavelength histograms of the Atana and Puripicar ignimbrites reveals two distinct populations. The Atana ignimbrite, with strong lineations and a poorly developed fluvial network, has a tightly clustered distribution of wavelengths with a dominant periodicity of ~310 m. The Puripicar, whose river channels are largely parallel to its wind channels, has a broader distribution, with a mean wavelength of ~ 370 m. A two-sample T-test yields a t value of 3.754, which corresponds to a >99% probability that these distributions are separate. This signal tentatively suggests that, as rivers exploit the aeolian channels throughout the erosion history of the Puripicar, they prefer a wider spacing than that created through aeolian processes. This finding highlights a potential link between dominant erosion process, wind or water, and preferred wavelength on the surface of ignimbrites in the Altiplano Puna Volcanic Complex.

Perkins, J. P.; Finnegan, N. J.

2011-12-01

324

Fluvial and climate controls on the surface energy balance in a large lowland river  

NASA Astrophysics Data System (ADS)

Partitioning of radiant and turbulent energy into evaporation and absorption in a river channel is controlled by climate and streamflow characteristics, and controls the water and energy balance. Atmosphere-surface interactions, coupled with advective processes, drive the heterogeneity of heat storage and exchange over longitudinal profiles whose hydraulic and thermal patterns are crucial for survival of migratory and resident fishes and subject to alteration by humans. Over 100 large-scale flow experiments have been conducted globally to measure abiotic and biotic responses to streamflow, yet none has been utilized to elucidate large-scale physical controls on the surface energy balance of a river. In this paper, we describe a synoptic method by which net solar radiation and turbulent heat fluxes were calculated over the length of a river from time series of hydroclimatological and fluvial conditions measured during a long-term large-scale flow experiment. We examine what are the dominant physical controls to the surface energy balance in a lowland river when surface water stage varies with flow releases in a 240-km reach of the San Joaquin River, California, USA. We developed an energy balance model integrated with advective exchange of heat utilizing spatially-distributed predictions of water surface elevation, inundated surface area, and velocity from an existing hydraulic model that accounts for losses and gains over the length of the river. Absorption of radiation along the river is determined by the wavelength-dependent index of refraction, expressed by the angle of refraction and the optical depth as a function of physical depth and the absorption coefficient. Results show that over the solar spectrum, the absorption coefficient varies by seven orders of magnitude, while flow depth varies by two orders of magnitude over time and distance. Observations and modeling show that (1) discharge is controlled mainly by flow releases, diversions, and exchanges with adjacent groundwater bodies and varies irregularly along the reach, (2) stream temperature converges upon air temperature where flow losses are greatest coinciding with the gravel-to-sand transition, and (3) sediment grain size decreases with distance downstream and is inversely related to streambed albedo. Longitudinal variations in meteorological conditions are relatively small, but variations in hydrologic conditions and stream temperature, which are accounted for dynamically in the model, have a significant influence to the variations observed in the surface heat fluxes. On the basis of measured climate and fluvial conditions, the net absorption is shown to vary spatially by up to 500 W m-2 at a given hour, and can vary by up to 45% with downstream variation in sediment characteristics. By explicitly accounting for the spectral shortwave absorption in concert with advective processes, it is possible to elucidate the mechanisms controlling the surface energy balance and thermal regime at large scales in rivers.

Bray, E. N.; Dunne, T.; Dozier, J.

2013-12-01

325

Variable responses of fluvial systems to late Quaternary climate changes in NW Romania  

NASA Astrophysics Data System (ADS)

In this paper, we discuss the similarities and differences in timing and style of fluvial processes (incision, terrace detachment, changes in the sedimentation styles) manifestation for different reference moments during the Late Quaternary history of two neighboring, medium size rivers from the NW part of Transylvanian Depression (Some?ul Mic River, 175 km long, drainage surface of 3773 kmp, and Arie? River, 167 km long, drainage surface of 2970 kmp). In the case of Somesul Mic River, a shallow, coarse gravel, braided channel was active at the level of the first terrace (T1, 5-8 m relative altitude), at least as early as MIS 3. After incision and formation of the present valley bottom, a low energetic river was active (,meandering or anabranching), which was later replaced by a shallow, coarse gravel braided channel (similar with the one on TI), active before LGM and maintained untill the Younger Dryas (or the early Holocene). During the early Holocene, the braided channel was replaced by a transitional one, slightly incised in the previous phase's alluvial materials, further abandoned for an incised, narrow meandering channel. The last channel type change is probably related to the large scale arrival and development of deciduous trees species in the area (~10.x kyrs BP), implying a few hundred years delay of the final fluvial adjustment to the new temperate conditions associated to the YD/Holocene transition. Along Aries River, a comparative shallow, coarse gravel, braided river was active at the level of TI, during MIS 3. However, erosional features on the top of the gravel sheet and some palaeomeanders are visible on the terrace surface, and suggest the existence of a transitional / meandering channel before this surface was completely abandoned. In the floodplain perimeter, an absolute age of the upper part of the coarse gravel sediments suggests this river style was functional at least during LGM, possibly earlier. This age, and the morphological and sedimentological evidences for generations of palaeomeanders imposed erosivelly on the upper part of the sedimentary sequence, suggest a meandering pattern probably starting with the Bolling - Allerod Interstadial. The results show that two very similar rivers, in terms of their location and present-day morphometric characteristics, do have similar large reactions to Late Quaternary climate changes, however, significant differences can be found in details of reaction time and the involved processes. The existing data suggest that Aries River is a more sensitive one than Somesul Mic River. The more conservatory behavior in the last case (e.g., no channel change during the Bolling - Allerod Interstadial, delayed reaction in the early Holocene) is probably explained by the slightly higher slope of this particular river, related to the presence of a large scale knickpoint in the medium part of the longitudinal profile (ca. 380 m), imposed by local geological conditions.

Per?oiu, Ioana; Per?oiu, Aurel

2014-05-01

326

Monitoring Fluvial Topography at Hyperspatial Resolutions with UAS imagery and Structure from Motion  

NASA Astrophysics Data System (ADS)

Monitoring is a fundamental task in remote sensing. As measurement technology progresses, there is a growing interest in hyperspatial (<10 cm) resolution topographic data which could allow more detailed investigations into the small scale processes which are the building blocks of large scale geomorphic change. Many geomorphologists are approaching this problem of high resolution topographic monitoring with well-proven technology such as ground-based or airborne LiDAR. However, there is also a growing interest in Structure from Motion (SfM) approaches which use images in order to reconstruct dense topographic point clouds. SfM relies on a new generation of image matching algorithms to deliver digital topographic point clouds with an extremely high level of automation and a very low requirement for specialist photogrammetry knowledge. The result is a low-cost, virtually unsupervised process that could foreshadow a new era of widespread hyperspatial topographic data. However, a widespread usage of SfM in fluvial geomorphology will require a rigorous assessment of the associated errors and limitations, a process which has only just begun. Here we present the findings of an experiment aimed at exploring the fundamental limitations of SfM in a fluvial geomorphology context. Our specific aims are to test the suitability of SfM as a hyperspatial topography production method and to explore the relationships between the number of raw images, the resolution of the raw images and the final quality of the resulting point clouds. We compare topographic point clouds generated from SfM and with LiDAR at two scales. First, a simple experiment was conducted on the Science Site of Durham University where an outdoor building was scanned with terrestrial LiDAR and photographed with a small format camera. Second, a field experiment was conducted on a water-worked pro-glacial braiding plain on the arctic island of Svalbard where imagery was acquired with a small Unmanned Aerial System (UAS) and airborne LiDAR data was acquired through the European Facility for Airborne Reseeaarch (EUFAR) and the NERC Airborne Remote Sensing Facility (ARSF). SfM was used to produce point clouds from the imagery which were directly compared to the LiDAR point clouds without being rasterised. Increasing the number of images does not lead to better quality point clouds. Increasing the image resolution, even in complex terrain, does not increase the quality of the topographic data. However, in certain conditions, the data quality of the SfM point clouds matches that of the LiDAR data. For the ground experiment, SfM delivered an optimal standard deviation of error of 1.8 mm. In the case of the Svalbard experiment, SfM yielded an optimal standard deviation of error of 4.5 cm. In both cases, this error is ?1/3000 of the image acquisition distance (i.e. the flying height) and is below the expected errors of the LiDAR data. These findings show that SfM can produce high quality topographic data but with the caveat that maximum data quality does not occur at maximum data resolution. Therefore, these findings indicate that the standard unsupervised SfM workflow is not yet capable of producing high quality hyperspatial topographic data.

Carbonneau, P.; James, T. D.; Black, M.

2012-12-01

327

[Influence of three types of riparian vegetation on fluvial erosion control in Pantanos de Centla, Mexico].  

PubMed

Wetlands constitute very important ecological areas. The aim of this study was to quantify the soil losses due to fluvial erosion from 2006 to 2008 in two riverbanks under three types of vegetal coverage dominated by Haematoxylum campechianum, Dalbergia brownei and Brachiaria mutica, in the Pantanos de Centla Biosphere Reserve, SE Mexico. The relationship between the texture, organic matter and pH of soils and soil losses was evaluated. We used erosion sticks to estimate soil losses in 18 plots (three plots per type, three vegetation types, two riverbanks). Soil loss decreased in this order: H. campechianum>B. mutica>D. brownei indicating that D. brownei scrubland has the most potential to retain soil. The higher erosive impact within H. campechianum sites can be related with the low density of these trees in the study areas, as well as the lack of association with other types of vegetation that could reinforce the rooting of the soil profile. Furthermore, soil losses in H. campechianum sites were dependent on soil texture. The soils under this type of vegetal coverage were mainly sandy, which are more vulnerable to the erosive action in comparison with fine textured soils or soils with higher clay content, like the ones found in D. brownei and B. mutica sites. Soil losses of 100 % in the second year (B. mutica plots) can be attributed to the distribution of roots in the upper soil layer and also to livestock management along riverbanks. This study recognizes the importance of D. brownei scrublands in riverbank soil retention. Nevertheless it is necessary to consider the role of an entire vegetal community in future research. PMID:20073341

Sepúlveda-Lozada, Alejandra; Geissen, Violette; Ochoa-Gaona, Susana; Jarquín-Sánchez, Aarón; de la Cruz, Simón Hernández; Capetillo, Edward; Zamora-Cornelio, Luis Felipe

2009-12-01

328

The balance between uplift and fluvial erosion over a single seismic cycle - an example from Taiwan  

NASA Astrophysics Data System (ADS)

The relationship between tectonic and geomorphic processes is important for understanding how topography evolves, and how the landscape reflects tectonic and climatic signatures. We present a case study of the relationship between uplift and erosion on the scale of a single seismic cycle, in which we can observe the creation of substantial coseismic topography and its subsequent removal by fluvial erosion. In Sept. 1999, the Mw 7.6 Chi-Chi earthquake struck western Taiwan. At the northern end of the rupture zone, in the Daan River valley, the earthquake activated the Dongshi Anticline, resulting in up to 13 of uplift due to coseismic folding. Where the Daan River crosses the anticline, the river responded to the coseismic uplift by very rapidly cutting into the uplifted topography, and by 2009 the river had carved a narrow bedrock gorge extending the width of the anticline. In the current stage of erosion, the river has ceased cutting down, and is now eroding laterally. Although widening within the gorge is relatively slow, the river is cutting back the upstream boundary of the anticline at a rate of ~15 m/yr. At this rate, the river will remove the uplifted topography and returned to its pre-uplift morphology in ~50 years. The post-1999 erosion rates in the Daan River are several orders of magnitude faster than background rates, and represent a transient phase of erosion in response to the disequilibrium created by coseismic uplift. In this case, the river is able to respond to the coseismic uplift of the Dongshi anticline solely through this transient response, and without long term changes in the river's morphology. This example highlights the potential importance of short-lived signals of uplift and erosion in the relationship between tectonics and landscape morphology.

Cook, Kristen; Graveleau, Fabien; Turowski, Jens; Hovius, Niels; Suppe, John

2014-05-01

329

Ecotoxicity of fluvial sediments downstream of the Ajka red mud spill, Hungary.  

PubMed

An integrated assessment of biological activity and ecotoxicity of fluvial sediments in the Marcal river catchment (3078 km(2)), western Hungary, is presented following the accidental spill of bauxite processing residue (red mud) in Ajka. Red mud contaminated sediments are characterised by elevated pH, elevated trace element concentrations (e.g. As, Co, Cr, V), high exchangeable Na, and induce an adverse effect on test species across a range of trophic levels. While background contamination of the river system is highlighted by adverse effects on some test species at sites unaffected by red mud, the most pronounced toxic effects apparent in Vibrio fischeri bioluminescence inhibition, Lemna minor bioassay and Sinapis alba root and shoot growth occur at red mud depositional hotspots in the lower Torna Creek and upper Marcal. Heterocypris incongruens bioassays show no clear patterns, although the most red mud-rich sites do exert an adverse effect. Red mud does however appear to induce an increase in the density of aerobic and facultative anaerobic bacterial communities when compared with unaffected sediments and reference sites. Given the volume of material released in the spill, it is encouraging that the signal of the red mud on aquatic biota is visible at a relatively small number of sites. Gypsum-affected samples appear to induce an adverse effect in some bioassays (Sinapis alba and Heterocypris incongruens), which may be a feature of fine grain size, limited nutrient supply and greater availability of trace contaminants in the channel reaches that are subject to intense gypsum dosing. Implications for monitoring and management of the spill are discussed. PMID:22772744

Klebercz, Orsolya; Mayes, William M; Ánton, Aron Dániel; Feigl, Viktória; Jarvis, Adam P; Gruiz, Katalin

2012-08-01

330

Spatial Variations in Carbon Storage along Headwater Fluvial Networks with Differing Valley Geometry  

NASA Astrophysics Data System (ADS)

We distinguish multiple valley types along headwater fluvial networks in the Colorado Front Range based on valley geometry (downstream gradient and valley-bottom width relative to active channel width) and the presence of biotic drivers (beaver dams or channel-spanning logjams associated with old-growth forest) capable of creating a multi-thread channel pattern. Valley type influences storage of fine sediment, organic matter, and carbon. Deep, narrow valleys have limited storage potential, whereas wide, shallow valleys with multi-thread channels have substantial storage potential. Multi-thread channels only occur in the presence of a biotic driver. Given the importance of headwater streams in the global carbon cycle, it becomes important to understand the spatial distribution and magnitude of carbon storage along these streams, as well as the processes governing patterns of storage. We compare carbon stored in three reservoirs: riparian vegetation (live, dead, and litter), instream and floodplain large wood, and floodplain soils for 100-m-long valley segments in seven different valley types. The valley types are (i) laterally confined valleys in old-growth forest, (ii) partly confined valleys in old-growth forest, (iii) laterally unconfined valleys with multi-thread channels in old-growth forest, (iv) laterally unconfined valleys with single-thread channels in old-growth forest, (v) laterally confined valleys in younger forest, (vi) recently abandoned beaver-meadow complexes with multi-thread channels and willow thickets, and (vii) longer abandoned beaver-meadow complexes with single-thread channels and very limited woody vegetation. Preliminary results suggest that, although multi-thread channel segments driven by beavers or logjams cover less than 25 percent of the total length of headwater river networks in the study area, they account for more than three-quarters of the carbon stored along the river network. Historical loss of beavers and old-growth forest has thus likely resulted in continuing loss of carbon storage in these headwater river networks.

Wohl, E. E.; Dwire, K. A.; Polvi, L. E.; Sutfin, N. A.; Bazan, R. A.

2011-12-01

331

Modeling the effects of bed topography on fluvial bedrock erosion by saltating bed load  

NASA Astrophysics Data System (ADS)

Abrasion by saltation is an important mechanism of fluvial incision into bedrock. Sklar and Dietrich (2004) introduced an abrasion model in which the erosion rate of an "approximately planar" bed is linearly dependent on the kinetic energy transferred by the vertical velocity of saltating grains. However, most bedrock-floored channels exhibit topographic variations that yield deviations from a planar surface, referred to as "bed topography." Observations show that bed topography affects erosion. Here the saltation-abrasion model is extended for a nonplanar bed. A several-centimeter high bump, transverse to the flow, is repeated every 50 cm. The kinetic energy of grain impacts is calculated in two ways: (1) impact velocity normal to bed topography and (2) vertical impact velocity. By comparing the latter case with the planar model, it is possible to isolate the effects of topography on the interception of saltation trajectories. Incorporating bed topography changes erosion in three ways. First, erosion is 10 to 1000 times faster, depending upon transport stage and grain size. Enhanced erosion results from both the interception of grains by topography and the increased kinetic energy transfer associated with high-angle impacts on the stoss side of bumps. Second, erosion increases monotonically with transport stage, whereas maximum erosion occurs at low to intermediate transport stage with a planar bed. Third, erosion decreases monotonically with grain size, whereas maximum erosion occurs with intermediate-sized grains with a planar bed. Although the model is highly simplified, results show that bed topography should be considered when simulating erosion of bedrock.

Huda, Shahen A.; Small, Eric E.

2014-06-01

332

Impacts of Columbia River discharge on salmonid habitat: 1. A nonstationary fluvial tide model  

NASA Astrophysics Data System (ADS)

This is the first part of a two-part investigation that applies nonstationary time series analysis methods and the St. Venant equations to the problem of understanding juvenile salmonid access to favorable shallow-water habitat in a tidal river. Habitat access is a function of river stage, tidal range, and the distribution of bed elevation. Part 1 models nonstationary tidal properties: species amplitudes and phases and tidal range. Part 2 models low-frequency river stage in the Lower Columbia River and reconstructs historical water levels, using the tidal model from part 1. To incorporate the nonstationary frictional effects of variable river discharge into the tidal model, we decompose the tidal wave into tidal species and calculate daily tidal range. Our one-dimensional tidal model is based on analytic wave solutions to the linearized St. Venant equation and uses six coefficients per tidal species to represent the upstream evolution of the frictionally damped tidal wave. The form of the coefficients is derived from the St. Venant equations, but their values are determined objectively from the data. About 50 station-years of surface elevation data collected (1981-2000) below Bonneville Dam (235 km from the ocean) were processed with a wavelet filter bank to retrieve time series of tidal species properties. A min-max filter was used to estimate daily tidal range. Tidal range, diurnal, and semidiurnal amplitudes were predicted with mean root mean square errors <30 mm, which is significantly more accurate than predictions obtained from harmonic analysis. Thus despite the compact form of our solution, we model nonstationary fluvial tidal properties with a high level of accuracy.

Kukulka, Tobias; Jay, David A.

2003-09-01

333

Mean and turbulent flow structure during the amalgamation process in fluvial bed forms  

NASA Astrophysics Data System (ADS)

Fluvial channels present bed forms such as dunes and ripples that alter instantaneous hydrodynamics parameters such as flow velocities, water surface profiles, bed shear stresses, and Reynolds stresses and create turbulent coherent structures that are significantly different from those presented in flat bed conditions. It is known that LES-based models are more suitable than RANS models to reproduce the complex hydrodynamics around bed forms. Herein, a LES model is applied to describe the mean and turbulent flow structure under superimposed bed forms. Three cases were simulated: RUN I (train of ripples), RUN II (superimposed bed forms), and RUN III (amalgamated bed forms). The LES modeling was performed using a free surface condition to allow the model to develop undulations and boils on the water surface caused by effect of the bed forms. Some important conclusions from this study are: the division of high and low shear stresses on the stoss side of the dune, the progression of the flow field topology from RUN I and RUN III, and the type of turbulent coherent structures found in each stage. The region of high shear stresses was related to turbulence production, in which the streamwise velocity fluctuations (where strips structures are related to streaks) were associated to the modification of the bed morphology. The turbulence Horseshoes Vortices (THV) were more frequent in RUN I than in the other two cases (where streamwise rolls were more frequent). Finally, the frequency of the bursting events increased from RUN I to RUN II and decreased from RUN II to RUN III. Implications of detailed hydrodynamics into bed forms processes are also presented and discussed.

Frias, Christian E.; Abad, Jorge D.

2013-10-01

334

Transport mechanism for Pb-210, Cs-137 and Pu fallout radionuclides through fluvial-marine systems  

NASA Astrophysics Data System (ADS)

Pb-210, Cs-137 and Pu-239,240 sediment-depth profiles in an anoxic, unbioturbated, estuarine depositional regime at the head of the Saguenay Fjord, Que. exhibit a seasonally-modulated component caused by pulsed inputs of silts and sands during high energy, spring river discharge events superimposed on an ambient depositional pattern of finer grained clays and organic matter. A precise sediment timestratigraphy has been determined by the inverse correlation of the Pb-210 activity with the rate of river discharge during the period, 1963-1976. The historical record of Cs-137 and Pu-239,240 sediment fluxes has been reconstructed through the normalization of fallout radionuclide activities to the excess Pb-210 activity profile. Radionuclide flux geochronologies have been interpreted on the basis of a fluvial-marine transport model which distinguishes between inputs due to direct adsorption of radionuclides onto particles in the water column and inputs resulting from the erosion of particle-associated radionuclides from the drainage basin. Rate constants corresponding to residence times of one year for Cs-137 and Pu-239,240 in the water column and 1500 years for each radionuclide in the drainage basin provide reasonable agreement between the model and experimental results, although there is some evidence for a slightly longer drainage basin residence time for plutonium. Both the threshold for the initial appearance of Pu-238, derived from the atmospheric burnup of a SNAP-9A satellite reactor in 1964, and the magnitude of its isotopic dilution by drainage basin inputs of Pu-239,240 are also in agreement with model predictions.

Smith, J. N.; Ellis, K. M.

1982-06-01

335

Characterization of soil thermal, hydrological, and mechanical properties at Musashino fluvial terrace in Fuchu, Japan  

NASA Astrophysics Data System (ADS)

The ground source heat pump (GSHP) system, based on heat exchange with the deep subsoil environment, generally operates with higher efficiency than the conventional air-source heat pump system. The GSHP system has received great interest in countries in North America and Western Europe because it can potentially reduce energy consumption and greenhouse gas emission. The GSHP releases heat energy to the subsoil during summer for cooling, while it pumps heat energy from the subsoil during winter for heating. To optimally design and operate GSHP systems, not only heat transport in the subsoil but also the influences of temperature changes on water flow, groundwater quality, and ground deformations need to be accurately simulated. The main objective of this study was to characterize soil thermal, hydrological, and mechanical properties of soils by monitoring subsoil temperature, groundwater level, and ground deformation at one of the potential GSHP installation sites in the Musashino fluvial terrace located in Fuchu-city, Japan. Monitoring instruments including resistance-temperature detectors and displacement transducers were installed inside a 50-m borehole excavated at the study site. Temperature observed at 5 m intervals in the borehole showed (i) that the soil temperature gradually decreased with depth, with the exception of temperature at the 5-m depth, and (ii) average temperatures increased as the average air temperature increased. Readings of the displacement transducers were found to be strongly affected by air temperature changes. Data observed at the borehole will be further evaluated and linked to soil physical properties measured from disturbed and undisturbed soil samples collected at the borehole.

Saito, H.; Moritani, S.; Kohgo, Y.; Hamamoto, S.; Takemura, T.; Ohnishi, J.; Komatsu, T.; Crest Komatsu Team

2011-12-01

336

The morphodynamic impact of vegetation and large wood on fluvial systems  

NASA Astrophysics Data System (ADS)

We present preliminary results from a set of recent experiments conducted in the Total Environment Simulator flume at the University of Hull in the framework of the Hydralab IV EU project. The aim of these experiments is to identify and assess the effects of riparian vegetation and large wood on the morphodynamics of braided river channels. The type and size of riparian vegetation is known to play a crucial role in shaping rivers, acting as a proper riparian engineer. Riparian vegetation influences bank stability, increases mean channel depth and can affect planform pattern by reducing the number of active branches. However, the geomorphic effect of plants can continue well after their erosion from banks. As dead or living pieces of large wood are transported through the fluvial network, they can exert a tremendous influence on river erosion and sedimentation processes, channel morphology, channel hydraulics, and ecological diversity of river channels. Our experiments consisted of different scenarios of presence / absence of riparian vegetation (simulated using alfalfa sprouts) and large wood density (simulated using wooden dowels). The experiments were designed to assess both the individual effects of woody debris and bank vegetation, as well as their combined effects. Each experiment has been characterised in terms of planform configuration (the number of active branches per cross-section) and bed topography (surveyed by a terrestrial laser scanner). Detailed DEM differencing was used to investigate sediment transport patterns and dynamics for the different vegetation-wood scenarios. The results of this work will help improve the ability to predict the response of river systems to different disturbances and management strategies.

Mao, L.; Bertoldi, W.; Comiti, F.; Gurnell, A. M.; McLelland, S. J.; Osei, N.; Ravazzolo, D.; Tal, M.; Welber, M.; Zanella, S.

2012-04-01

337

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

NASA Astrophysics Data System (ADS)

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 River Delta, Saskatchewan, Canada. The numerical experiments start with a generic, preformed, bifurcation that is symmetrical about the channel centerline, has fixed walls, and constant bathymetry in each bifurcate. Upstream boundary conditions include a constant incoming water and sediment discharge with equilibrium sediment concentrations and both steady and equal water surface elevations downstream. Computations proceed until the discharge ratio between bifurcate channels ( Qr) does not change for one morphological time unit (defined as cross-sectional area divided by sediment transport rate per unit width), at which time the system is defined as stable. Similar to the stability diagram for coarse-grained distributive networks (Bolla Pittaluga et al., 2003; Miori et al., 2006), stable, equilibrium, fine-grained bifurcation configurations are asymmetrical in their Qr. However, unlike coarse-grained systems, Qr becomes more asymmetrical with increasing Shields theta|n When the eight natural bifurcations are plotted on the stability diagram, three plot in ¡§unstable¡¨ space. Even though these ¡§unstable¡¨ bifurcations have been active for 40 years, analyses of their evolution from serial maps of the Mossy Delta shows that there is significant bar growth and change in channel area compared to the five ¡§stable¡¨ bifurcations. The implications of these findings for our understanding of channel bifurcation dynamics, evolution and avulsion will be discussed.

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

2007-12-01

338

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

339

Use of Archival Sources to Improve Water-Related Hazard Assessments at Volcán de Agua, Guatemala  

NASA Astrophysics Data System (ADS)

This interdisciplinary study focuses on the use of archival sources from the 18th Century Spanish Empire to develop a greater understanding of mudflow trigger mechanisms at Volcán de Agua in Guatemala. Currently, hazard assessments of debris flows at Volcán de Agua are largely based on studies of analogous events, such as the mudflow at Casita Volcano in 1998 caused by excessive rainfall generated by Hurricane Mitch. A preliminary investigation of Spanish archival sources, however, indicates that a damaging mudflow from the volcano in 1717 may have been triggered by activity at the neighbouring Volcán de Fuego. A VEI 4 eruption of Fuego in late August 1717 was followed by 33 days of localized 'retumbos' and then a major local earthquake with accompanying mudflows from several 'bocas' on the southwest flank of Agua. Of particular importance for this study is an archival source from Archivos Generales de Centro América (AGCA) that consists of a series of letters, petitions and witness statements that were written and gathered following the catastrophic events of 1717. Their purpose was to argue for royal permission to relocate the capital city, which at the time was located on the lower flanks of Volcán de Agua. Within these documents there are accounts of steaming 'avenidas' of water with sulphurous smells, and quantitative descriptions that suggest fissure formation related to volcanic activity at Volcán de Fuego. Clear evidence for volcano-tectonic activity at the time, combined with the fact there is no mention of rainfall in the documents, suggest that outbursts of mud from Agua's south flank may have been caused by a volcanic perturbation of a hydrothermal system. This single example suggests that further analysis of archival documents will provide a more accurate and robust assessment of water related hazards at Volcán de Agua than currently exists.

Hutchison, A. A.; Cashman, K. V.; Rust, A.; Williams, C. A.

2013-12-01

340

Llamado a cubrir Beca de investigacin. Uso del agua en Sistemas de Produccin Agrcola del Chaco Semirido.  

E-print Network

Llamado a cubrir Beca de investigación. Uso del agua en Sistemas de Producción Agrícola del Chaco agua en sistemas de producción agrícola en el Chaco Semiárido mediante modelos funcionales de cultivo

Nacional de San Luis, Universidad

341

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

342

Seismic cycle and rheological effects on estimation of present-day slip rates for the Agua Blanca and San Miguel-Vallecitos faults, northern  

E-print Network

Seismic cycle and rheological effects on estimation of present-day slip rates for the Agua Blanca mantle rheology. We examine the sensitivity of fault slip rate estimates to assumed rheology for the Agua­North America plate boundary zone. The Agua Blanca fault is seismically quiet, but offset alluvial fans indicate

Lee, Jeff

343

LA INDUSTRIALIZACIN DE PUEBLA Y EL CONTROL DEL AGUA A MEDIADOS DEL SIGLO XIX. CONFLICTOS Y REDES DE LOS NUEVOS EMPRESARIOS.  

E-print Network

153 LA INDUSTRIALIZACI�N DE PUEBLA Y EL CONTROL DEL AGUA A MEDIADOS DEL SIGLO XIX. CONFLICTOS Y REDES DE LOS NUEVOS EMPRESARIOS. Evelyne Sanchez FRAMESPA-CNRS La competencia por el agua en México: un agua como una riqueza que mereciera su atención. Hasta el más observador de ellos, Alejandro de

Paris-Sud XI, Université de

344

PLANTACIONES DE PINO Y AGUA EN CRDOBAAgosto de 2013 Recibido: 17 de enero de 2013; Fin de arbitraje: 8 de marzo;  

E-print Network

PLANTACIONES DE PINO Y AGUA EN C�RDOBAAgosto de 2013 Recibido: 17 de enero de 2013; Fin de relevancia especial en áreas montañosas de regiones secas dado su papel importante en la provisión de agua invierno. En la actualidad, los impactos de las plantaciones serranas sobre la provisión de agua pueden

Nacional de San Luis, Universidad

345

Predicting interwell heterogeneity in fluvial-deltaic reservoirs: Outcrop observations and applications of progressive facies variation through a depositional cycle  

SciTech Connect

Nearly 11 billion barrels of mobile oil remain in known domestic fluvial-deltaic reservoirs despite their mature status. A large percentage of this strategic resource is in danger of permanent loss through premature abandonment. Detailed reservoir characterization studies that integrate advanced technologies in geology, geophysics, and engineering are needed to identify remaining resources that can be targeted by near-term recovery methods, resulting in increased production and the postponement of abandonment. The first and most critical step of advanced characterization studies is the identification of reservoir architecture. However, existing subsurface information, primarily well logs, provides insufficient lateral resolution to identify low-permeability boundaries that exist between wells and compartmentalize the reservoir. Methods to predict lateral variability in fluvial-deltaic reservoirs have been developed on the basis of outcrop studies and incorporate identification of depositional setting and position within a depositional cycle. The position of a reservoir within the framework of a depositional cycle is critical. Outcrop studies of the Cretaceous Ferron Sandstone of Utah have demonstrated that the architecture and internal heterogeneity of sandstones deposited within a given depositional setting (for example, delta front) vary greatly depending upon whether they were deposited in the early, progradational part of a cycle or the late, retrogradational part of a cycle. The application of techniques similar to those used by this study in other fluvial-deltaic reservoirs will help to estimate the amount and style of remaining potential in mature reservoirs through a quicklook evaluation, allowing operators to focus characterization efforts on reservoirs that have the greatest potential to yield additional resources.

Knox, P.R.; Barton, M.D. [Univ. of Texas, Austin, TX (United States)

1997-08-01

346

Miocene fluvial-tidal sedimentation in a residual forearc basin of the Northeastern Pacific Rim: Cook Inlet, Alaska case study  

SciTech Connect

Cook Inlet in southern Alaska represents a Cenozoic residual forearc basin in a convergent continental margin, where the Pacific Plate is being subducted beneath the North American Plate. This basin accumulated the >6,700-m-thick, mainly nonmarine, Eocene-Pliocene Kenai Group. These rocks contain biogenic coal-bed methane estimated to be as high as 245 TCF. Lignites to subbituminous coals with subsurface R{sub o} ranging from 0.38 to 0.73 percent and the stage of clay-mineral diagenesis and expandibility indicate a thermally {open_quotes}cool{close_quotes} basin. Miocene Tyonek and Beluga Formations compose 65 percent (>4,300 m thick) of the Kenai Group. The Tyonek includes conglomeratic sandstones, siltstones, mudstones, coals, and carbonaceous shales, interpreted as braided- stream deposits. These fluvial deposits are interbecided with burrowed, lenticular, and flaser-bedded sandstones, siltstones, and mudstones, interpreted as tidal deposits. Tyonek framework conglomerates formed in wet alluvial fans incised on paleovalleys of the Chugach terrane. Coal-forming mires are well developed on abandoned braided-stream deposits. Tyonek drainages formed in high-gradient alluvial plains inundated by tides similar to environments in the modern upper Cook Inlet. The upper Miocene Beluga consists of sandstones, siltstones, mudstones, carbonaceous shales, and coals deposited in meandering (low sinuosity) and anastomosed fluvial systems. These fluvial deposits alternated vertically with deposits of coal-forming mires. The Beluga drainages formed in low-gradient alluvial plains. The high-gradient Tyonek alluvial plain was probably controlled by provenance uplift and eustatic change, whereas the low-gradient Beluga alluvial plain was influenced by subdued provenance uplift and rapid basin subsidence. Rapid sedimentation on both these low- and high-gradient alluvial plains, which kept up with subsidence, produced a thermally {open_quotes}cool{close_quotes} basin.

Stricker, G.D.; Flores, R.M. [Geological Survey, Denver, CO (United States)

1996-12-31

347

The fluvial flux of particulate organic matter from the UK: Quantifying in-stream losses and carbon sinks  

NASA Astrophysics Data System (ADS)

This study considers records of fluvial suspended sediment concentration and its organic matter content from across the United Kingdom from 1974 to 2010. Suspended sediment, mineral concentration and river flow data were used to estimate the particulate organic matter (POM) concentration and flux. Median annual POM flux from the UK was 1596 ktonnes/yr. The POM concentration significantly declined after the European Commission's Urban Wastewater Directive was adopted in 1991 although the POM flux after 1992 was significantly higher. Estimates of POM flux were compared to a range of catchment properties to estimate the flux of particulate organic carbon (POC) and particulate organic nitrogen (PON) as they entered rivers and thus estimate the net catchment losses. The total fluvial flux of N from the soil source to rivers was 2209 ktonnes N/yr with 814 ktonnes N lost at the tidal limit, and so leaving 1395 ktonnes N/yr loss to atmosphere from across UK catchments - equivalent to an N2O flux from UK rivers of between 33 and 154 ktonnes (N2O)/yr. The total fluvial flux of carbon from the soil source to rivers for the UK was 5020 ktonnes C/yr; the flux at the tidal limit was 1508 ktonnes C/yr, equivalent to 6.5 tonnes C/km2/yr. Assuming that all the net catchment loss goes into the atmosphere, then the impact of rivers on the atmosphere is 3512 ktonnes C/yr, equivalent to 15.2 tonnes C/km2/yr. The loss of POM from the UK suggests that soil erosion in the UK prevents soil being a net sink of CO2 and is instead a small net source to the atmosphere.

Worrall, Fred; Burt, Tim P.; Howden, Nicholas J. K.

2014-11-01

348

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

USGS Publications Warehouse

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

Draut, Amy; Ritchie, Andrew C.

2013-01-01

349

An Intense Terminal Epoch of Widespread Fluvial Activity on Early Mars: 2. Increased Runoff and Paleolake Development  

NASA Technical Reports Server (NTRS)

To explain the much higher denudation rates and valley network development on early Mars (more than approximately 3.6 Gyr ago), most investigators have invoked either steady state warm/wet (Earthlike) or cold/dry (modern Mars) end-member paleoclimates. Here we discuss evidence that highland gradation was prolonged, but generally slow and possibly ephemeral during the Noachian Period, and that the immature valley networks entrenched during a brief terminal epoch of more erosive fluvial activity in the late Noachian to early Hesperian. Observational support for this interpretation includes (1) late-stage breaching of some enclosed basins that had previously been extensively modified, but only by internal erosion and deposition; (2) deposition of pristine deltas and fans during a late stage of contributing valley entrenchment; (3) a brief, erosive response to base level decline (which was imparted as fretted terrain developed by a suite of processes unrelated to surface runoff) in fluvial valleys that crosscut the highland-lowland boundary scarp; and (4) width/contributing area relationships of interior channels within valley networks, which record significant late-stage runoff production with no evidence of recovery to lower-flow conditions. This erosion appears to have ended abruptly, as depositional landforms generally were not entrenched with declining base level in crater lakes. A possible planetwide synchronicity and common cause to the late-stage fluvial activity are possible but remain uncertain. This increased activity of valley networks is offered as a possible explanation for diverse features of highland drainage basins, which were previously cited to support competing warm, wet and cold, dry paleoclimate scenarios.

Rossman III, Irwin P.; Howard, Alan D.; Craddock, Robert A.; Moore, Jeffrey M.

2005-01-01

350

The linkage between hillslope vegetation changes and late-Quaternary fluvial-system aggradation in the Mojave Desert revisited  

NASA Astrophysics Data System (ADS)

Valley-floor-channel and alluvial-fan deposits and terraces in the southwestern US record multiple episodes of late Quaternary fluvial aggradation and incision. Perhaps the most well constrained of these episodes took place from the latest Pleistocene to the present in the Mojave Desert. One hypothesis for this episode, i.e. the paleo-vegetation change hypothesis (PVCH), posits that a reduction in hillslope vegetation cover associated with the transition from Pleistocene woodlands to Holocene desert scrub generated a pulse of sediment that triggered a primary phase of aggradation downstream, followed by channel incision, terrace abandonment, and initiation of a secondary phase of aggradation further downstream. A second hypothesis, i.e. the extreme-storm hypothesis, attributes episodes of aggradation and incision to changes in the frequency and/or intensity of extreme storms. In the past decade a growing number of studies has advocated the extreme-storm hypothesis and challenged the PVCH on the basis of inconsistencies in both timing and process. Here I show that in eight out of nine sites where the timing of fluvial-system aggradation in the Mojave Desert is reasonably well constrained, measured ages of primary aggradation and/or incision are consistent with the predictions of the PVCH if the time-transgressive nature of paleo-vegetation changes with elevation is fully taken into account. I also present an alternative process model for PVCH that is more consistent with available data and produces sediment pulses primarily via an increase in drainage density (i.e. a transformation of hillslopes into low-order channels) rather than solely via an increase in sediment yield from hillslopes. This paper further documents the likely important role of changes in upland vegetation cover and drainage density in driving fluvial-system response during semiarid-to-arid climatic changes.

Pelletier, J. D.

2014-03-01

351

Late cenozoic fluvial stratigraphy of the New Jersey piedmont: A record of glacioeustasy, planation, and incision on a low-relief passive margin  

USGS Publications Warehouse

Late Cenozoic fluvial deposits and erosional landforms in the New Jersey Piedmont record two episodes of valley incision, one in the Late Miocene and one in the Early Pleistocene, separated by periods of planation and fluvial deposition. The upland erosion surface and a fluvial gravel are the remnants of a low-relief Late Miocene landscape. Late Miocene incision was followed by deposition of a fluvial plain and cutting of straths in the Pliocene. Early Pleistocene incision produced the present valleys, which contain Middle to Late Pleistocene fluvial deposits. The two incisions correspond to permanent glacioeustatic lowering during expansion of the Antarctic ice sheet in the Middle to Late Miocene and development of Northern Hemisphere ice sheets in the Late Pliocene. Bordering Coastal Plain marine deposits indicate that the upland erosion surface was formed during a rising sea-level trend between the Late Oligocene and Middle Miocene. The Pliocene plain and straths formed during a period of rising sea level in the Early Pliocene. The stratigraphic record indicates that the oldest preserved landforms are no older than Late Miocene, that landscape planation in coastal regions of low-relief passive margins can be achieved in <20 m.yr., and that these surfaces can be incised and dissected in <5 m.yr.

Stanford, S.D.; Ashley, G.M.; Brenner, G.J.

2001-01-01

352

Depositional environment of Hosston sandstones (lower cretaceous), Bogalusa Field, Washington Parish, Louisiana (identification of deltaic and fluvial sequences in logs)  

E-print Network

. The sandstones occur in 7 ft (2 m) to 33 ft (10 m) sections consisting of 1 ft (. 3 m) to 12. 5 ft (4 m) bedsets. Most of the sandstones are fluvial and generally fine-grained (mean grain size: 0. 16 mm to 0. 21 mm). Monocrystalline quartz content is moderate... (70%), rock fragment percentages are high (17'4), matrix content is mod- erate (6%), and shale clasts and woody fragments are common. Cement bulk volume percentages are hiqh (26%) with silica in the form of quartz overgrowths being the dominant...

Strong, Catherine Cox

2012-06-07

353

Pacing Early Mars fluvial activity at Aeolis Dorsa: Implications for Mars Science Laboratory observations at Gale Crater and Aeolis Mons  

E-print Network

The impactor flux early in Mars history was much higher than today, so sedimentary sequences include many buried craters. In combination with models for the impactor flux, observations of the number of buried craters can constrain sedimentation rates. Using the frequency of crater-river interactions, we find net sedimentation rate \\lesssim 20-300 {\\mu}m/yr at Aeolis Dorsa. This sets a lower bound of 1-15 Myr on the total interval spanned by fluvial activity around the Noachian-Hesperian transition. We predict that Gale Crater's mound (Aeolis Mons) took at least 10-100 Myr to accumulate, which is testable by the Mars Science Laboratory.

Kite, Edwin S; Fassett, Caleb I

2012-01-01

354

Cross-stratified Wood: Enigmatic Woody Debris Deposits in Warm-Polar Fluvial Sediments (Pliocene Beaufort Formation, Nunavut)  

NASA Astrophysics Data System (ADS)

Woody debris has been an important sediment component and a significant geomorphic agent in pristine fluvial systems since the Devonian. In recent years a large volume of research has focussed on various aspects of the importance of woody debris within the fluvial realm; from the evolutionary significance of fossil wood accumulations in the rock record to studies of the biogeomorphological and ecological importance of woody debris in modern rivers. In this presentation we describe cross-stratified woody debris deposits comprising organic detritus from a boreal-type treeline forest that included species of pine, birch, poplar, alder, spruce, eastern cedar, and larch, in both shrub and tree form. The cross-stratified wood is an enigmatic subset of fine woody debris which, to our knowledge, has never before been described from either the global stratigraphic record or modern fluvial environments. The deposits we describe are located within the Pliocene Beaufort Formation on Meighen Island, Nunavut, Canada, at a latitude of 80°N, and are compared with other cross-stratified woody debris deposits that have been noted elsewhere in the Pliocene of the Canadian Arctic. We make the robust observation that these deposits appear to be geographically and stratigraphically restricted to polar latitudes from a period of warm climatic conditions during the Pliocene (15-20 °C warmer mean annual temperature than the present day). In this regard it is possible to speculate that the transport of large amounts of woody debris as bedload is potentially a unique feature of forested high latitude rivers. Such bedload deposition requires a large amount of woody debris with a greater density than the fluid transporting it. The softwood composition of the debris suggests that this was most likely attained by saturation and subsequent entrainment of extensive accumulations of deadwood, promoted by unusually high rates of tree mortality and low rates of bacterial decomposition arising from the high latitude and extreme seasonal variations in light and temperature regimes. This observation requires further investigation because, if cross-stratified woody debris is confirmed as a common yet unique feature of warm-polar climates, it may have significant implications for predictive studies of fluvial processes, woody debris accumulation, and carbon burial in a warming Arctic. Recognition of cross-stratified woody debris in pre-Cenozoic records may also provide an independent proxy for this particular environment.

Davies, N. S.; Gosse, J. C.; Rybczynski, N.

2012-04-01

355

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

356

Physical and chemical weathering in modern and Permian proximal fluvial systems  

NASA Astrophysics Data System (ADS)

Chapter 1 Inferring paleoclimate from ancient fluvial strata can be challenging, and conflicting interpretations for a given system are common in the literature. This research uses a combination of physical and chemical weathering signals in an attempt to better define the paleoclimatic interpretations for the proximal Cutler Formation near Gateway, Colorado (Chapter 3) and the Post Oak Conglomerate in the Wichita Mountains, Oklahoma (Chapter 4), both Permian units. Chapter 4 includes a comparison of weathering signals from modern sediments in the Wichita Mountains. A methodology for pretreatment techniques used for grain-size analysis was evaluated during the course of the research and is the topic of Chapter 2. This dissertation is organized as three stand-alone manuscripts and a brief summary of each is presented below. Chapter 2 Pretreatment drying of mud-sized sediment (<63 im) resulted in clayrich (>39%) samples exhibiting more sensitivity to drying techniques than clay-poor (<39%) samples. This demonstrates an influence of the drying technique on the granulometric results. Employing freeze drying for sample drying yielded the most consistent results. However, for samples with <39% clay-sized material, all drying techniques are equally effective, and no apparent need exists for the extra effort (and expense) that accompanies freeze drying. Chapter 3 Scanning Electron Microscopy is a useful tool in the study of quartz grain microtextures. Microtextures on quartz grains from the proximal Cutler Formation near Gateway, CO were documented for the presence/absence of 18 distinct microtextures. Averaging of presence/absence data for the samples provided a means to use more quantitative techniques than previously employed for SEM microtextural analysis. These continuous quantitative variables were utilized for non-metric multidimensional scaling, a purely quantitative technique that does not rely on initial assumptions of what environments produce specific microtextures. Chapter 4 The Post Oak Conglomerate was deposited in a climate much wetter than the modern climate of the Wichita Mountains today. Significant amounts of clay, high percentages of Al2O3 in the mud fraction, spheroidal weathering, thick weathering rinds, and hyperconcentrated flood flow deposits are prominent in the Post Oak conglomerate and lacking in the modern Blue Beaver Creek sediment. When compared to other modern climates, the Post Oak Conglomerate fits best with a tropical climate. The climate of the region for the Early Permian is commonly interpreted to be arid. However; these results suggest a brief time period of wet conditions in the Wichita Mountains prior to the onset of the aridity documented in younger Permian units of the area.

Keiser, Leslie Jo

357

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

358

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

359

Connectivity mapping for flow and transport models in heterogeneous fluvial deposits using lidar and optical imaging  

NASA Astrophysics Data System (ADS)

Connectivity of heterogeneities within fluvial aquifers has a strong influence on groundwater flow and solute transport. Addressing the effects of heterogeneities, popular modeling tools use geostatistical methods that produce multiple realizations faithful to a chosen statistical framework, but usually with minimal correlation or resemblance to real geologic formations. These typically include pixel-based approaches and object-based approaches. More recently applied to this problem, multiple-point approaches have become popular for addressing the heterogeneities and connectivity of the geometries of aquifer facies. This is due to their greater ability to handle the complexities and three-dimensionality of these systems; yet still rely on training images statistically derived from abstract geometries. Taking a step closer to models based on true geological structures, we are developing a measurement approach using ground-based lidar and optical imaging data obtained from extended, rugose outcrops. The varying spatial orientations of these extended outcrops allow the reconstruction of more complete 3D descriptions of the facies. These outcrops provide multiple cross-sections of facies (or realizations) that are continuous through a single geological unit. We use these data to measure the minimum possible extension in 3D space of the high and low transmissivity facies, which characterize the key components of the heterogeneities and their connectivity. That is, for a given facies, using the outcrop data, we are able to identify the lengths of the facies in multiple directions within the extent of the available outcrops; effectively providing a minimum length of the facies in each direction. This yields minimum limits, and in cases where facies terminate, maximum limits on the characteristic lengths of the facies. Where possible, their orientation with respect to the direction of the paleocurrent is also recorded. Because the facies of this particular geological unit may be classified as bimodal, it is reasonable to represent them as either high or low K material. This allows us to develop the model as high K heterogeneities as connected groups of facies that are separated by measurable distances between them through low K material. We are looking at these distances or lengths in multiple orientations, allowing us to construct a model of connectivity that may be related to gradients in any direction. These measurements will be used to provide a real-world geological basis for modeling flow and transport in aquifers.

Soller, M. S.; Weissmann, G. S.; Carritt, J.; Frechette, J. D.

2013-12-01

360

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

361

Dating Fluvial Terraces by 230Th/U on Pedogenic Carbonate, Wind River Basin, Wyoming  

NASA Astrophysics Data System (ADS)

Reliable and precise ages of Quaternary pedogenic carbonate can be obtained with 230Th/U dating by TIMS applied to large suites of carefully selected small samples. Datable carbonate can form within a few thousand years of surface stabilization allowing ages of Quaternary deposits and surfaces to be closely estimated. We have dated pedogenic carbonate from glacio-fluvial terraces of the Wind River Basin to better constrain the age of the penultimate glaciation in the central Rocky Mountains. Dense pedogenic carbonate clast-rinds from gravels of middle to late Quaternary terraces in the Wind River Basin contain 5-35 ppm U and 0.01-0.3 ppm 232Th, with (230Th/232Th)=5-7500, making them extremely suitable for 230Th/U dating. Complexities in the textures of the Wind River clast-rinds emphasized the importance of sampling horizons as thin as 0.5 mm from polished slabs to avoid averaging long (104-105 yr) and potentially discontinuous depositional histories. Samples meeting straightforward textural criteria with finite 230Th/U ages preserve within-rind stratigraphic order in all cases. Cosmogenic nuclide (10Be, 26Al, 36Cl) dating of Wind River terraces by others yields most-probable ages that are systematically younger than those inferred from clast-rind 230Th/U ages though the differences are not resolvable outside of the analytical and systematic uncertainties of the two techniques. Ages from 230Th/U rind dating for terraces WR4 (163+/-8 ka) and WR2 (55+/-7 ka), in conjunction with constraints from WR1 and the modern floodplain, indicate incision of the Wind River is slower than previously inferred and relatively uniform from terrace to terrace over the past glacial cycle. An age of 151+/-9 ka is interpolated for terrace WR3 that may be traced to moraines of the final advance of the Bull Lake glaciation at the type locality. The new age indicates that the Bull Lake glaciation climaxed near the end of marine isotope stage 6 rather than in early stage 5 and coincided with a global ice volume maximum. Thus, the Bull Lake glaciation is not an example of asynchrony between advances of mountain glaciers and continental ice sheets.

Sharp, W. D.; Ludwig, K. R.; Chadwick, O. A.; Amundson, R.; Glaser, L. L.

2001-12-01

362

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

363

Fluvial response to sub-orbital scale environmental changes in southern French Alps  

NASA Astrophysics Data System (ADS)

Linkage between landscape processes and deep sea deposits is assumed by rivers transfer. Despite all the efforts of the Source-to-Sink community during the last decade, very few studies permit to link marine sedimentary records with phenomena occurring onland. The Var sedimentary system is a spatial restricted sediment routing system with a very narrow continental shelf and steep slope. This particularity makes the Var an ideal target for studying sediment transfers under glacial climate. Late Quaternary sea level changes didn't modified the size of drainage area and during both highstand and lowstand, the deep submarine fan (Var Sedimentary Ridge) was continuously feed by a single channel directly connected to Var river mouth. Located at the border between Mediterranean and alpine domains, the Var River watershed is characterized by steep slope and rare sediment dams. Several studies during the last 20 years had shown that for centennial to daily scale, turbidity flows are related to Var river floods. Based on the analysis of stable oxygen isotopes and radiocarbon dates we established the first high resolution stratigraphy of 20 meters long turbidite deposits on the Var Sedimentary Ridge. This record covers the last 75 ka of the Var turbiditic activity which directly reflects the hydrological and sediment discharge of the onshore fluvial system. The turbidite frequencies show a multiscale variability : (1) the higher frequency corresponds to Dansgaard-Oeschger oscillations and Heinrich events, and (2) the lower frequency characterizes the amplitude of suborbital-scale variability which seems to be modulated by long term orbital parameters variations. The same pattern is reported for vegetation history of European Mediterranean border. This is consistent with our results which suggest that soil stabilization by vegetation cover plays an important role in the modulation of sediment transfers. Under stadials and Heinrich cold and dry climate, the scarce vegetation cover was favorable to intense sediment discharge of the Var River. The opposite trend is observed during interstadials when milder condition permit the spreading of tree cover, the turbidite activity at that time was as low as during Holocene. The highest frequency of turbidite deposition is observed during LGM and rapidly decreases during Heinrich stadial 1, this period could correspond to glacier retreat towards upper valleys. In order to test this hypothesis, future studies will focus on the nature and origin of sediment sources.

Bonneau, Lucile; Jorry, Stephan; Toucanne, Samuel; Emmanuel, Laurent

2013-04-01

364

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

365

New Teleostei from the Agua Nueva Formation (Turonian), Vallecillo (NE Mexico)  

Microsoft Academic Search

A new genus and new species of an ichthyodectiform fish, a new species of the pachyrizodontid Goulmimichthys, as well as specimens of Araripichthys sp. are described from the Agua Nueva Formation (Turonian) of Vallecillo, State of Nuevo León, NE Mexico. The ichthyodectiform fish shows a combination of characters from different families, warranting the creation of a new genus and questioning

Alberto Blanco; Lionel Cavin

2003-01-01

366

Use of renewable sources of energy in Mexico case: San Antonio Agua Bendita  

Microsoft Academic Search

This paper presents a project undertaken in Mexico to electrify the remote village of San Antonio Agua Bendita (SAAB) using a custom designed hybrid power system. The hybrid power system will provide grid quality electricity to this community which would otherwise not have been electrified via traditional distribution lines. The hybrid power system was designed to electrify the entire community,

J. Gutierrez-Vera

1994-01-01

367

Modern fluvial sediment provenance and pollutant tracing: a case study from the D?evnice River Basin (eastern Moravia, Czech Republic)  

NASA Astrophysics Data System (ADS)

Modern fluvial deposits of a small fluvial system were studied in the area of eastern Moravia (Czech Republic) with the aim of determining the provenance of the deposits and weathering processes. Identification of the source rocks and their alongstream variations were used for the evaluation of the natural or anthropogenic source of the heavy metals. Paleogene flysch sandstones, flysch mudstones and Quaternary loesses represent source rocks and reflect both the role of recycling and local sources. Provenance from sandstones dominate upstream whereas mudstones represent dominant source rock in the downstream part of the fluvial system. The contents of Pb and Zn are highly enhanced when compared with the natural background in the entire study area. Their anthropogenic source is connected with the rubber/shoe manufacturing industry and traffic. The contents of Cr, Co, Cu, Ni and V are usually lower in modern deposits than in the identified source rocks.

Nehyba, Slavomír; Adamová, Marie; Faimon, Ji?í; Kuchovský, Tomáš; Holoubek, Ivan; Zeman, Josef

2010-04-01

368

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

369

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

370

Early Holocene fluvial activity from the sedimentology and palaeohydrology of gravel terrace in the semi arid Mahi River Basin, India  

NASA Astrophysics Data System (ADS)

Palaeocompetence analysis and palaeodischarge estimation techniques are applied to a late Pleistocene-early Holocene gravel terrace in the Mahi River Basin, western India. Terrace sedimentology, comprising gravels overlain by sand lithofacies suggests a gradual change in palaeohydrological conditions marking a switch from braided to meandering fluvial styles. The discharge values for the gravel bedforms based on the clast size and the cross bed set thickness are estimated between ˜150-180 m3 s-1 comparable with the present day observed values albeit with a much higher competence. Results indicate that fluvial aggradation occurred under low discharge conditions with intermittent high discharge events depositing longitudinal gravel bars. The incision of these gravel bars and the formation of terraces can be attributed to the higher discharge regime post 9.2 ka. The study further indicates that whereas the aggradation of the gravel terrace during the early Holocene was controlled by the large sediment influx, the incision that followed was in response to the increase in the discharge and competence of the river flow.

Sridhar, Alpa; Chamyal, L. S.; Bhattacharjee, Falguni; Singhvi, A. K.

2013-04-01

371

Using fluvial channel morphology to obtain the neotectonic characteristics of the Liuchia fault, an important active structure in southwestern Taiwan  

NASA Astrophysics Data System (ADS)

The Liuchia fault in southwestern Taiwan has been considered as one of the major active faults in the active Taiwan orogen. It is identified by its clear geomorphic features, and forms a major geologic boundary of Taiwan's Western Foothills. No unanimous historical evidence for seismic activity of the Liuchia fault exists, thus the fault poses large earthquake hazard potentials for the populous southwestern Taiwan. Here we attempted to analyze the characteristics of the fault from fluvial channel morphology of the Kueichung River that flows across the fault. We also calculated actual river incision rates from the age of river terraces along the river to obtain the rock uplift rates of the hanging-wall block of the fault. We have obtained a detailed river long profile of the Kueichung River from surveys using RTK-GPS, and a channel width profile from actual field measurements using a Laser Rangefinder. The fluvial channel morphology of the Kueichung River appears to have been affected by active folding in the hanging-wall block of the Liuchia fault. Such active deformation pattern is also evident from river incision rate patterns. Combining these different datasets, we constructed a realistic model of the subsurface geometry of the Liuchia fault in southwestern Taiwan, and calculated the long-term slip rates of this important active structure in southwestern Taiwan.

Shyu, J. H.; Du, K.

2013-12-01

372

Monitoring water quality in estuarine environments: lessons from the MAGEST monitoring programme in the Gironde fluvial-estuarine system  

NASA Astrophysics Data System (ADS)

The Gironde estuary, one of the largest European ones, presents temporary low dissolved oxygen content in its fluvial section close to the Bordeaux urban area. In a context of population growth and of long-term environmental changes, the development of a high-frequency monitoring programme of the fluvial-estuarine system of the Gironde, called MAGEST (MArel Gironde ESTuary), had appeared essential to address current and future water-quality issues/evaluations. The objectives of the MAGEST survey programme are to establish a reference database to improve the knowledge of the Gironde estuary functioning, encompassing the aspects of hydrology, sediment dynamics and biogeochemistry. Through examples of results from intratidal to seasonal time scales, we demonstrate how such a time-series is of valuable interest to extract the main trends of its functioning and of the water quality in relation to external forcings (climatology, urban wastes, land use, ...) and to predict the future evolution of the Gironde estuary with global and environmental changes.

Etcheber, H.; Schmidt, S.; Sottolichio, A.; Maneux, E.; Chabaux, G.; Escalier, J.-M.; Wennekes, H.; Derriennic, H.; Schmeltz, M.; Quéméner, L.; Repecaud, M.; Woerther, P.; Castaing, P.

2010-12-01

373

Monitoring water quality in estuarine environments: lessons from the MAGEST monitoring program in the Gironde fluvial-estuarine system  

NASA Astrophysics Data System (ADS)

The Gironde Estuary, one of the largest European ones, presents temporary low dissolved oxygen content in its fluvial section close to the Bordeaux urban area. In a context of population growth and of long-term environmental changes, the development of a high-frequency monitoring programme of the fluvial-estuarine system of the Gironde, called MAGEST (MArel Gironde ESTuary), had appeared essential to address current and future water-quality issues/evaluations. The objectives of the MAGEST survey program are to establish a reference database to improve the knowledge of the Gironde Estuary functioning, encompassing the aspects of hydrology, sediment dynamics and biogeochemistry. Through examples of results from intratidal to seasonal time scales, we demonstrate how such a long-term, high-frequency monitoring of a fluvio-estuarine system is of valuable interest to extract the main trends of its functioning and of the water quality in relation to external forcings (climatology, urban wastes, land use, ...) and to predict the future evolution of an estuary with global and environmental changes.

Etcheber, H.; Schmidt, S.; Sottolichio, A.; Maneux, E.; Chabaux, G.; Escalier, J.-M.; Wennekes, H.; Derriennic, H.; Schmeltz, M.; Quéméner, L.; Repecaud, M.; Woerther, P.; Castaing, P.

2011-03-01

374

LES of atmospheric boundary layer flow over fluvial-like anisotropic topography with a dynamic surface drag model  

NASA Astrophysics Data System (ADS)

A dynamic surface drag model (A. & M. 2011, JFM 679, 288 - 314) is applied in LES of atmospheric boundary layer (ABL) flow over fractal-like topography where the height field exhibits power-law energy spectrum. Initially, the dynamic drag model was applied in LES of ABL flow over isotropic synthetic fractal-like roughness. Here we consider fluvial-like anisotropic landscapes. Two main cases are considered. The first is a fluvial-like topography built through numerical solution of the Kardar-Parisi-Zhang equation.ootnotetextThanks also to Profs. P. Passalacqua and F. Porte-Agel for providing KPZ solution fields. The second is a rescaled topography (Texas) map from the U.S. National Elevation Dataset. These landscapes are dominated by anisotropic modes that have emerged through geomorphological erosion processes. The dynamic model yields stable solutions even in these highly anisotropic cases: performance is strongest for cases where the LES grid- and test-filter width are within the landscape ``self-similar'' range. Weaknesses are reported for cases where spectral exponent changes with wavenumber, motivating the development of a scale-dependent version of the dynamic approach using two test-filters.

Anderson, William; Meneveau, Charles

2011-11-01

375

Does Model Development Ahead of Data Collection Have Merit? A Case for Advancing Non-Local Fluvial Transport Theories  

NASA Astrophysics Data System (ADS)

The purpose of this work is to suggest how experiments might be constructed to provide data to test recently proposed phenomenological non-local model of depositional transport; formulated on the basis of morphological arguments but with limited data. A sound methodology for developing models of geological systems is to first collect significant data and then carefully identify an appropriate model form and parameters. An alternative approach is to construct what might be referred to as a phenomenological model, where limited observation of the system is used to suggest an appropriate mathematical form that matches the critical nature of the physical system behavior. By their nature, phenomenological models are often developed within a fairly narrow range of observations. In this way, interesting findings can occur when the models are modified and exercised across wider physical domains, in particular in domains where there is an absence of hard data to corroborate or invalidate the model predictions. Although this approach might be frown on my some, it is important to recognize the stellar and proven track record of phenomenological models, which despite the original scarcity of data, often pave the way to new perspectives and important findings. The poster child example is the Higgs boson. In the early 60's manipulation of the quantum field equations revealed a critical inconsistency related to the masses of fundamental particles that could only be mathematically resolved by assuming that they operated within a field that would exert drag; this conjecture took almost fifty years and the vast experimental operation of the Large Hadron Collider to physically confirm. In this work we examine a current phenomenological model used to describe non-local transport in fluvial sediment domains. This model has its genesis in attempting to describe the shapes of hill slope profiles, while acknowledging the fact that two points of the landscape with the same local slope are not always associated with the same sediment flux. The key innovation then is to model the sediment flux at a point in terms of an upstream weighted sum of fluvial slopes or other geomorphological attributes of the system. In the hill-slope context, the downstream flow of information in this non-local formalism is well supported by fundamental observations of the distribution of downstream particle transport distances. However, when the same model is applied in the context of depositional systems it appears to be inconsistent with profiles of depositional surfaces. In particular, the model predicts fluvial profiles with curvature signs opposite to those observed in nature. When a simple mathematical manipulation is made, where the flux at a point is expressed as a downstream weighting of fluvial slopes, however, predictions with the correct form are recovered. At this time, no specific mechanism or clear corroborating data have been identified that would explain this downstream control. Does this mean we should ignore this result or would it be better to use it as a motivation to seek out hypotheses tests that would confirm or invalidate the current suggested models of downstream non-local transport? A series of innovative experiments that address the collection of experimental evidence for downstream control in fluvial transport are described.

Voller, V. R.; Falcini, F.; Foufoula-Georgiou, E.; Ganti, V.; Paola, C.; Hill, K. M.; Swenson, J. B.; Longjas, A.

2013-12-01

376

Combining impact sensor field and laboratory flume measurements with other techniques for studying fluvial bedload transport in steep mountain streams  

NASA Astrophysics Data System (ADS)

The timing and rate of fluvial bedload transport are of central importance within sediment budget studies and in many applications in river science and engineering. During the years 2010, 2011 and 2012 detailed field measurements with portable impact sensors as a non-invasive technique for indirectly determining fluvial bedload transport intensity were conducted in two instrumented and supply-limited drainage basin systems (Erdalen and Bødalen) in the fjord landscape in western Norway. Additional field measurements with portable impact sensors were carried out in 2010 and 2011 in selected transport-limited fluvial systems in the Coast Mountains of western Canada. The collected impact sensor field data were calibrated with laboratory flume experiments. The data from the impact sensor field measurements in western Norway and the flume experiments were combined with field data from continuous discharge monitoring, repeated surveys of channel morphometry and sediment texture, particle tracer measurements, Helley-Smith samplings, underwater video filming and biofilm analyses. The combination of methods and techniques applied provides insights into the temporal variability and intensity of fluvial bedload transport in the selected mountain streams: (i) in the transport-limited systems with generally high bedload transport rates during high discharge and with bedload material moving in clusters over the impact sensor plates, impact sensor data (based on a 1 s measuring interval) provide the opportunity to detect the start and end of bedload transport, thus to identify discharge thresholds for sediment entrainment, and to roughly estimate the intensity and relative intensity of change of bedload transport during the measuring period; (ii) in the supply-limited systems with low bedload transport rates and bedload components moving separately (as single particles) over the impact sensor plates, impact sensor data (with a 1 s measuring interval) allow the detection of the start and end of transport of bedload components > 11.3 mm, thus the identification of discharge thresholds for possible entrainment of particles, the quantification of the number of particles > 11.3 mm moving over the impact sensor plates during the measuring period, the rough estimation of grain sizes of the particles moving separately over the impact sensor plates, and the calculation of the total mass of the bedload material > 11.3 mm moving over the impact sensor plates during the measuring period; (iii) when combined with other methods and techniques (Helley-Smith sampling, particle tracer measurements, biofilm analyses, underwater video filming) which provide information on the active bedload transport channel width, on discharge thresholds for possible entrainment of particles of different grain sizes, and on transport rates of bedload material < 11.3 mm, total rates of fluvial bedload transport, covering all given grain sizes of the bedload material, can be calculated for the supply-limited mountain streams with generally low bedload transport. The higher measured annual bedload yield in Bødalen (13.6 t km- 2 yr- 1) compared to Erdalen (2.6 t km- 2 yr- 1) reflects a higher level of slope-channel coupling in Bødalen than in Erdalen.

Beylich, Achim A.; Laute, Katja

2014-08-01

377

Revitalizing a mature oil play: Strategies for finding and producing unrecovered oil in frio fluvial-deltaic sandstone reservoirs at South Texas. Annual report, October 1994--October 1995  

SciTech Connect

The Frio Fluvial-Deltaic Sandstone oil play of South Texas has produced nearly 1 billion barrels of oil, yet it still contains about 1.6 billion barrels of unrecovered mobile oil and nearly the same amount of residual oil resources. Interwell-scale geologic facise models of Frio Fluvial-deltaic reservoirs are being combined with engineering assessments and geophysical evaluations in order to determine the controls that these characteristics exert on the location and volume or unrecovered mobile and residual oil. Progress in the third year centered on technology transfer. An overview of project tasks is presented.

Holtz, M.; Knox, P.; McRae, L. [and others

1996-02-01

378

The distribution and fluvial redistribution of soil organic carbon in semiarid rangelands  

NASA Astrophysics Data System (ADS)

Compared to other terrestrial biomes, the carbon dynamics of drylands have attracted relatively little attention, perhaps due to their characteristically low primary productivity, low soil organic carbon (OC) contents and slow OC turnover rates. However, covering approximately 40% of the land surface, drylands represent a significant component of the global terrestrial carbon sink. Our study examines the distribution and fluvial redistribution of particulate-associated OC over a dynamic grass to shrub ecotone in semiarid central New Mexico, USA. Surface soil (0-0.05 m) samples from beneath different vegetation covers across the ecotone were collected and physically fractionated by density (>1 g ml) and particle size (one phi intervals from <0.0625 to >4 mm, with no deliberate dispersion of aggregates). There were significant (P<0.05) differences in OC concentration between different particle-size fractions, with peaks in the silt-clay (<0.0625 mm) fraction, and, unexpectedly, in the three coarse-medium sand (2-1, 1-0.5, and 0.5-0.25 mm) fractions. As soil erosion by runoff is particle size-selective, this suggests estimating erosional carbon fluxes as a function of total sediment flux may be overly simplistic. Given that many soil erosion models already explicitly consider the transport of several particle size classes, we believe that the results presented here justify the particle-size variant parameterisation of OC concentration, which we are currently working to implement. Importantly, both of the coarsest (>4 and 4-2 mm) fractions had OC concentrations comparable to the <2 mm average, attributed to the aggradation of finer primary particles which suggests that, in dryland soils at least, the current practice of ignoring the >2 mm fraction may underestimate the magnitude of the soil OC sink. In addition to topsoil characterisation, we monitored natural erosion events from four 300 m2 runoff plots over four monsoon seasons, capturing all eroded sediment which was fractionated as detailed above. Substantial variability in bulk sediment OC enrichment between rainstorm events and between monsoon seasons demonstrates the need for multi-year studies to understand these ecohydrological systems. Intriguingly, average OC enrichment increases substantially as shrub domination increases. Historically, many studies have attributed whole-sediment OC enrichment to changes in particle-size distribution, on the basis of strong correlations between particle-size distributions and whole-sediment OC concentration enrichment. However, our results demonstrate substantial OC enrichment within all particle-size fractions, particularly in fine sand fractions, suggesting that this perceptual model is incomplete. We argue that advancing our understanding of OC redistribution by erosion requires detailed mechanistic examination of transport processes, in conjunction with numerical simulations to address the challenges of upscaling such process understanding.

Cunliffe, Andrew; Puttock, Alan; Anderson, Karen; Brazier, Richard

2014-05-01

379

Human impact on fluvial sediments: distinguishing regional and local sources of heavy metals contamination  

NASA Astrophysics Data System (ADS)

Industrial pollution can provide a useful tool to study spatiotemporal distribution of modern floodplain sediments, trace their provenance, and allow their dating. Regional contamination of southern Moravia (the south-eastern part of the Czech Republic) by heavy metals during the 20th century was determined in fluvial sediments of the Morava River by means of enrichment factors. The influence of local sources and sampling sites heterogeneity were studied in overbank fines with different lithology and facies. For this purpose, samples were obtained from hand-drilled cores from regulated channel banks, with well-defined local sources of contamination (factories in Zlín and Otrokovice) and also from near naturally inundated floodplains in two nature protected areas (at 30 km distance). The analyses were performed by X-ray fluorescence spectroscopy (ED XRF), ICP MS (EDXRF samples calibration, 206Pb/207Pb ratio), magnetic susceptibility, cation exchange capacity (CEC), and 137Cs and 210Pb activities. Enrichment factors (EF) of heavy metals (Pb, Zn, Cu and Cr) and magnetic susceptibility of overbank fines in near-naturally (near annually) inundated areas allowed us to reconstruct historical contamination by heavy metals in the entire study area independently on lithofacies. Measured lithological background values were then used for calculation of EFs in the channel sediments and in floodplain sediments deposited within narrow part of a former floodplain which is now reduced to about one quarter of its original width by flood defences. Sediments from regulated channel banks were found stratigraphically and lithologically "erratic", unreliable for quantification of regional contamination due to a high variability of sedimentary environment. On the other hand, these sediments are very sensitive to the nearby local sources of heavy metals. For a practical work one must first choose whether large scale, i.e. a really averaged regional contamination should be reconstructed, or whether more or less qualitative information on local point sources is searched for. The profiles from regulated river reaches are highly prone to local sources and due to the stratigraphic chaos and post-depositional mobilization of heavy metals, which we revealed using 206Pb/207Pb ratio; such profiles were further excluded from an evaluation of regional contamination. Overbank fines in the study area (middle and lower reach of the Morava) are only weakly but whole-regionally contaminated (maximal EFs are 1.3-2 for Pb and Zn, 1.2-1.7 for Cu, 1.1-1.2 for Cr and 2-4 for magnetic susceptibility). Regulated river channel sediments, which reflect the actual contamination from local sources, produced apparent EFs ranging from 0.3 to 15 for heavy metals and 0.4-21 for MS, with the highest values obtained downstream from the most relevant point source in the study area, shoe-making and related chemical industry in Zlín and Otrokovice.

Novakova, T.; Matys Grygar, T.; Bábek, O.; Fam?ra, M.; Mihaljevi?, M.; Strnad, L.

2012-04-01