These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
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 INFORMACIÓN maduros son beneficiosos para la calidad del agua en Puerto Rico. Este resultado se obtuvo integrando, mediante modelos, la información de distintas capas geográficas de Puerto Rico:(1) calidad

Gilbes, Fernando

2

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

SciTech Connect

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

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

1993-09-01

3

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

NASA Astrophysics Data System (ADS)

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

El-Mowafy, Hamed Zeidan

4

OPTIMIZACIÓN DE REDES DE DISTRIBUCIÓN DE AGUA UTILIZANDO UN ALGORITMO GENÉTICO  

Microsoft Academic Search

RESUMEN: Un algoritmo genético (AG), es un procedimiento de búsqueda del óptimo de una función basado en la mecánica natural darwiniana de supervivencia de los individuos mejor adaptados. En el presente trabajo se ha desarrollado un algoritmo genético que permite determinar la red de distribución de agua de coste mínimo para una topología y una condición de carga dadas. El

Ma P. Montesinos; A. García-Guzmán; J. L. Ayuso

1997-01-01

5

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

Microsoft Academic Search

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

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

1994-01-01

6

Hydrology & Fluvial Geomorphology  

E-print Network

Hydrology & Fluvial Geomorphology Alan Jones E:mail: Alan.Jones@ed.ac.uk Course Plan Day 1 of field-data: Flow and particle analysis Day 3: Analysis and modelling of results · Hydraulic calculations, long duration storms will result in the greatest amount of geomorphological change #12;Important

7

Simulations of Fluvial Landscapes  

NASA Astrophysics Data System (ADS)

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

Cattan, D.; Birnir, B.

2013-12-01

8

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

9

Extraterrestrial Fluvial Channel Patterns  

NASA Astrophysics Data System (ADS)

Fluvial (i.e., riverine or river-like) channel patterns are prominently displayed on the subaerial surfaces of the terrestrial planets Venus, Earth and Mars. They also occur in submarine settings, as well as on the surfaces of the Moon and on Saturn's moon Titan. Some of these channel patterns seem clearly to derive from morphodynamical processes, i.e., processes involving the interaction and adjustment of the channel morphology to the entrainment, transport, and deposition of sediment. Other patterns, many with considerable resemblance to known morphodynamical ones, seem best explained by purely erosional processes or by construction that does not involve sedimentation (I.e., lava channels). While water is the best understood fluid in regard to causal association with many of these channels, other fluids with water-like properties are also involved. The latter include various lava compositions, particularly basaltic, and liquid methane (for Titan), both of which are capable to generating river-like channels. Indeed, for many extraterrestrial cases the formative fluid cannot be uniquely identified on the basis of the channel morphology alone. Instead, one must employ a search for consistency, coherence, and consilience among associated geological features in order to narrow the limits of possibility. The similarities in channel forms produced by these diverse fluid compositions and associated processes suggest that any general theory of fluvial channel patterns will have to encompass a much broader range of reality than what can be most commonly observed on Earth.

Baker, V. R.

2012-12-01

10

Progress in Understanding Fluvial Processes.  

ERIC Educational Resources Information Center

Discusses two of the major research trends that are broadening the understanding of fluvial processes and changing the approach to investigations of stream behavior. These trends include research on rivers that do not flow in alluvial channels and detailed field studies on the mechanics of fluvial processes. (JN)

Prestegaard, Karen L.

1984-01-01

11

Fluvial sediment concepts  

USGS Publications Warehouse

This report is the first of a series concerned with the measurement of and recording of information about fluvial sediment and with related environmental data needed to maintain and improve basic sediment knowledge. Concepts presented in this report involve (1) the physical characteristics of sediment which include aspects relative 'to weathering, soils, resistance to erosion, and particle size, (2) sediment erosion, transport, and deposition characteristics, which include aspects relative to fine sediment and overland flow, coarse sediment and streamflow, variations in stream sediment concentration, deposition, and denudation, (3) geomorphic considerations, which include aspects relative to the drainage basin, mass wasting, and channel properties, (4) economic aspects, and (5) data needs and program objectives to be attained through the use of several kinds of sediment records.

Guy, Harold P.

1970-01-01

12

¡Truco Con Agua!  

NSDL National Science Digital Library

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

Lawrence Hall of Science

2009-01-01

13

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

14

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

15

Tinto Vallis Fluvial Channel  

NASA Technical Reports Server (NTRS)

<

[figure removed for brevity, see original site]

This night time IR image shows a small fluvial channel located near Tinto Vallis. These channels are northeast of Tyrrhena Patera and its related lava flows. Tyrrhena Patera is one of the larger volcanic complexs in the southern hemisphere of Mars. Small channels are easy to see in nighttime IR, with the cold channel floor (dark) contrasting from the warmer (bright) surroundings.

NOTE: in nighttime images North is to the bottom of the image.

Image information: IR instrument. Latitude -24.6, Longitude 349.7 East (10.3 West). 100 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

2004-01-01

16

Fluvial valleys on Martian volcanoes  

NASA Technical Reports Server (NTRS)

Channels and valleys were known on the Martian volcanoes since their discovery by the Mariner 9 mission. Their analysis has generally centered on interpretation of possible origins by fluvial, lava, or viscous flows. The possible fluvial dissection of Martian volcanoes has received scant attention in comparison to that afforded outflow, runoff, and fretted channels. Photointerpretative, mapping, and morphometric studies of three Martian volcanoes were initiated: Ceraunius Tholus, Hecate Tholus, and Alba Patera. Preliminary morphometric results indicate that, for these three volcanoes, valley junction angles increase with decreasing slope. Drainage densities are quite variable, apparently reflecting complex interactions in the landscape-forming factors described. Ages of the Martian volcanoes were recently reinterpreted. This refined dating provides a time sequence in which to evaluate the degradational forms. An anomaly has appeared from the initial study: fluvial valleys seem to be present on some Martian volcanoes, but not on others of the same age. Volcanic surfaces characterized only by high permeability lava flows may have persisted without fluvial dissection.

Baker, Victor R.; Gulick, Virginia C.

1987-01-01

17

Fluvial valleys and Martian palaeoclimates  

NASA Technical Reports Server (NTRS)

Theoretical models of early Martian atmospheric evolution describe the maintenance of a dense CO2 atmosphere and a warm, wet climate until the end of the heavy-bombardment phase of impacting. However, the presence of very young, earthlike fluvial valleys on the northern flank of Alba Patera conflicts with this scenario. Whereas the widespread ancient Martian valleys generally have morphologies indicative of sapping erosion by the slow outflow of subsurface water, the local Alba valleys were probably formed by surface-runoff processes. Because subsurface water flow might be maintained by hydrothermal energy inputs and because surface-runoff valleys developed late in Martian history, it is not necessary to invoke drastically different planet-wide climatic conditions to explain valley development on Mars. The Alba fluvial valleys can be explained by hydrothermal activity or outflow-channel discharges that locally modified the atmosphere, including precipitation and local overland flow on low-permeability volcanic ash.

Gulick, Virginia C.; Baker, Victor R.

1989-01-01

18

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

19

Depuración de las aguas residuales procedentes de la tintura con transportadores  

Microsoft Academic Search

En este trabajo, se describe la técnica de extracción-cromatografía de gases utilizada para la valoración cuantitativa de los carriers (transportadores de tintura) en las aguas residuales.\\u000aA continuación se determinan las cinéticas de biodegradación de seis transportadores de tintura. Utilizando dos de estos carriers se han preparado unos efluentes sintéticos, estudiándose su depuración en una planta piloto de fangos activados

Martí Crespi Rosell; José Cegarra Sánchez

1970-01-01

20

Agua Caliente and Their Music.  

ERIC Educational Resources Information Center

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

Ryterband, Roman

1979-01-01

21

Fluvial mudstone breccias and their petroleum significance  

SciTech Connect

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

Putnam, P.E.

1987-05-01

22

The fluvial record of climate change.  

PubMed

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

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

2012-05-13

23

AGUA TIBIA PRIMITIVE AREA, CALIFORNIA.  

USGS Publications Warehouse

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

Irwin, William P.; Thurber, Horace K.

1984-01-01

24

Exploring hypsometry in glacial and fluvial environments  

NSDL National Science Digital Library

This laboratory exercise explores the topographic signature of fluvial and glacial landscapes in different tectonic environments. Students develop a list of mountain ranges around the world to explore, then extract topographic data from 90-meter SRTM DEMs, and develop a series of hypsometric curves for each range. Each student works on a single range, but as a class we build up a database of 10-15 ranges around the world. The hypsometric curves are compared with each other and with published curves to look for signals of fluvial incision vs. glacial erosion in the landscapes.

Karen Gran

25

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.

26

Geography 547: Fluvial Geomorphology Lecture Schedule, Fall, 2009  

E-print Network

Geography 547: Fluvial Geomorphology Lecture Schedule, Fall, 2009 Instructor: Dr. Allan James Email, and web materials. [Week] Date Topic Pages [1] Aug.20 Course Mechanics & Introduction: "Geomorphology, Fluvial Geomorphology, River Management & Flood Hydrology" ---------- Types of River Channels [2] 25

James, L. Allan

27

The Modification of Mars Fluvial Surfaces  

NASA Technical Reports Server (NTRS)

The identification of fluvial deposits on Mars is impaired by modifying geological processes. An analysis of surface patterns of superimposed dunes and channels in paleoflood environments in Washington State and Australia can yield information on buried surfaces. Additional information is contained in the original extended abstract.

Bourke, M. C.; Zimbelman, J. R.; Finnegan, D.; Banerdt, B.

2001-01-01

28

A fluvial mercury budget for Lake Ontario.  

PubMed

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

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

2014-06-01

29

Geography 547: Fluvial Geomorphology Tentative Lecture Schedule  

E-print Network

Geography 547: Fluvial Geomorphology Tentative Lecture Schedule Fall, 2014 Instructor: Dr. Allan Branch -------- [5] Flood Frequency Analysis Hogan, Ch.1; James, 15-1 to 15-10 16 Recurrence intervals, Bohman [7] Spatial Analysis James, Anal. Sidebar 6-8 & DEM exercise 30 Mapping channel networks

James, L. Allan

30

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

31

Applied fluvial geomorphology. Report No. 31  

SciTech Connect

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

MacBroom, J.G.

1981-03-01

32

Applied fluvial geomorphology. Report No. 31  

SciTech Connect

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

MacBroom, J.G.

1981-03-01

33

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

34

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

35

Martian Fluvial Conglomerates at Gale Crater  

NASA Astrophysics Data System (ADS)

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, R. M. E.; Grotzinger, J. P.; Dietrich, W. E.; Gupta, S.; Sumner, D. Y.; Wiens, R. C.; Mangold, N.; Malin, M. C.; Edgett, K. S.; Maurice, S.; Forni, O.; Gasnault, O.; Ollila, A.; Newsom, H. E.; Dromart, G.; Palucis, M. C.; Yingst, R. A.; Anderson, R. B.; Herkenhoff, K. E.; Le Mouélic, S.; Goetz, W.; Madsen, M. B.; Koefoed, A.; Jensen, J. K.; Bridges, J. C.; Schwenzer, S. P.; Lewis, K. W.; Stack, K. M.; Rubin, D.; Kah, L. C.; Bell, J. F.; Farmer, J. D.; Sullivan, R.; Van Beek, T.; Blaney, D. L.; Pariser, O.; Deen, R. G.; Kemppinen, Osku; Bridges, Nathan; Johnson, Jeffrey R.; Minitti, Michelle; Cremers, David; Edgar, Lauren; Godber, Austin; Wadhwa, Meenakshi; Wellington, Danika; McEwan, Ian; Newman, Claire; Richardson, Mark; Charpentier, Antoine; Peret, Laurent; King, Penelope; Blank, Jennifer; Weigle, Gerald; Schmidt, Mariek; Li, Shuai; Milliken, Ralph; Robertson, Kevin; Sun, Vivian; Baker, Michael; Edwards, Christopher; Ehlmann, Bethany; Farley, Kenneth; Griffes, Jennifer; Miller, Hayden; Newcombe, Megan; Pilorget, Cedric; Rice, Melissa; Siebach, Kirsten; Stolper, Edward; Brunet, Claude; Hipkin, Victoria; Léveillé, Richard; Marchand, Geneviève; Sobrón Sánchez, Pablo; Favot, Laurent; Cody, George; Steele, Andrew; Flückiger, Lorenzo; Lees, David; Nefian, Ara; Martin, Mildred; Gailhanou, Marc; Westall, Frances; Israël, Guy; Agard, Christophe; Baroukh, Julien; Donny, Christophe; Gaboriaud, Alain; Guillemot, Philippe; Lafaille, Vivian; Lorigny, Eric; Paillet, Alexis; Pérez, René; Saccoccio, Muriel; Yana, Charles; Aparicio, Carlos Armiens; Caride Rodríguez, Javier; Carrasco Blázquez, Isaías; Gómez Gómez, Felipe; Elvira, Javier Gómez; Hettrich, Sebastian; Lepinette Malvitte, Alain; Marín Jiménez, Mercedes; Frías, Jesús Martínez; Soler, Javier Martín; Torres, F. Javier Martín; Molina Jurado, Antonio; Sotomayor, Luis Mora; Muñoz Caro, Guillermo; Navarro López, Sara; González, Verónica Peinado; García, Jorge Pla; Rodriguez Manfredi, José Antonio; Planelló, Julio José Romeral; Alejandra Sans Fuentes, Sara; Sebastian Martinez, Eduardo; Torres Redondo, Josefina; O'Callaghan, Roser Urqui; Zorzano Mier, María-Paz; Chipera, Steve; Lacour, Jean-Luc; Mauchien, Patrick; Sirven, Jean-Baptiste; Manning, Heidi; Fairén, Alberto; Hayes, Alexander; Joseph, Jonathan; Squyres, Steven; Thomas, Peter; Dupont, Audrey; Lundberg, Angela; Melikechi, Noureddine; Mezzacappa, Alissa; DeMarines, Julia; Grinspoon, David; Reitz, Günther; Prats, Benito; Atlaskin, Evgeny; Genzer, Maria; Harri, Ari-Matti; Haukka, Harri; Kahanpää, Henrik; Kauhanen, Janne; Paton, Mark; Polkko, Jouni; Schmidt, Walter; Siili, Tero; Fabre, Cécile; Wray, James; Wilhelm, Mary Beth; Poitrasson, Franck; Patel, Kiran; Gorevan, Stephen; Indyk, Stephen; Paulsen, Gale; Bish, David; Schieber, Juergen; Gondet, Brigitte; Langevin, Yves; Geffroy, Claude; Baratoux, David; Berger, Gilles; Cros, Alain; Uston, Claude d.; Lasue, Jérémie; Lee, Qiu-Mei; Meslin, Pierre-Yves; Pallier, Etienne; Parot, Yann; Pinet, Patrick; Schröder, Susanne; Toplis, Mike; Lewin, Éric; Brunner, Will; Heydari, Ezat; Achilles, Cherie; Oehler, Dorothy; Sutter, Brad; Cabane, Michel; Coscia, David; Szopa, Cyril; Robert, François; Sautter, Violaine; Nachon, Marion; Buch, Arnaud; Stalport, Fabien; Coll, Patrice; François, Pascaline; Raulin, François; Teinturier, Samuel; Cameron, James; Clegg, Sam; Cousin, Agnès; DeLapp, Dorothea; Dingler, Robert; Jackson, Ryan Steele; Johnstone, Stephen; Lanza, Nina; Little, Cynthia; Nelson, Tony; Williams, Richard B.; Jones, Andrea; Kirkland, Laurel; Treiman, Allan; Baker, Burt; Cantor, Bruce; Caplinger, Michael; Davis, Scott; Duston, Brian; Fay, Donald; Hardgrove, Craig; Harker, David; Herrera, Paul; Jensen, Elsa; Kennedy, Megan R.; Krezoski, Gillian; Krysak, Daniel; Lipkaman, Leslie; McCartney, Elaina; McNair, Sean; Nixon, Brian; Posiolova, Liliya; Ravine, Michael; Salamon, Andrew; Saper, Lee; Stoiber, Kevin; Supulver, Kimberley; Van Beek, Jason; Zimdar, Robert; French, Katherine Louise; Iagnemma, Karl; Miller, Kristen; Summons, Roger; Goesmann, Fred; Hviid, Stubbe; Johnson, Micah; Lefavor, Matthew; Lyness, Eric; Breves, Elly; Dyar, M. Darby; Fassett, Caleb; Blake, David F.; Bristow, Thomas; DesMarais, David; Edwards, Laurence; Haberle, Robert; Hoehler, Tori; Hollingsworth, Jeff; Kahre, Melinda; Keely, Leslie; McKay, Christopher; Bleacher, Lora; Brinckerhoff, William; Choi, David; Conrad, Pamela; Dworkin, Jason P.; Eigenbrode, Jennifer; Floyd, Melissa; Freissinet, Caroline; Garvin, James; Glavin, Daniel; Harpold, Daniel; Mahaffy, Paul; Martin, David K.

2013-05-01

36

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

37

Field methods for measurement of fluvial sediment  

USGS Publications Warehouse

The complexity of hydrologic and physical environments and man's ever-increasing data needs make it essential for those who collect sediment data to be aware of basic concepts involved in the processes of erosion, transport, and deposition of sediment, and of the equipment and procedures necessary to representatively sample sediment and measure its concentration. This report describes equipment and procedures for the collection and measurement of fluvial sediment.

Edwards, Thomas K.; Glysson, G. Douglas

1998-01-01

38

Riparian vegetation and fluvial geomorphic processes  

Microsoft Academic Search

Riparian vegetation and fluvial-geomorphic processes and landforms are intimately connected parts of the bottomland landscape. Relations among vegetation, processes, and landforms are described here for representative streams of four areas of the United States: high-gradient streams of the humid east, coastal-plain streams, Great Plains streams, and stream channels of the southwestern United States. Vegetation patterns suggest that species distributions in

Cliff R. Hupp; W. R. Osterkamp

1996-01-01

39

Geomorphic elements on modern distributive fluvial systems  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

40

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

41

Time and the rivers flowing: Fluvial geomorphology since 1960  

NASA Astrophysics Data System (ADS)

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

Wohl, Ellen

2014-07-01

42

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

43

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

44

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

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

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

45

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

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

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

46

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

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

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

47

Fluvial processes on Mars: Erosion and sedimentation  

NASA Technical Reports Server (NTRS)

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

Squyres, Steven W.

1988-01-01

48

Ancient fluvial response to uplift and aggradation  

SciTech Connect

The Cloverly Formation of the western Powder River Basin represents nonmarine sedimentation during eastward migration of the Western Interior foreland basin coeval with orogenic activity in the Cordilleran fold-thrust belt. It provides an opportunity to evaluate aggradational responses to tectonic uplift. The Cloverly Formation overlies the Morrison Formation (Jurassic) with a sharp basal contact marked by a cross-bedded, pebble conglomerate consisting of black chert clasts; conglomerates are overlain by a thick, dominantly trough cross-bedded, medium to fine grained quartzarenite. Fining upward sequences are rare. Sedimentary structures suggest these sandstones to be deposited in fluvial channels with a highly sinuous northerly paleoflow. In outcrop, discontinuous sandstones represent distinct channel systems, with some channel sands being laterally adjacent to levee, overbank, and swamp facies of bioturbated, carbonaceous siltstones, mudstones, and thin coals. In subsurface, the Cloverly Formation thins and thickens over short horizontal distances, suggesting channel erosion into the upper Morrison Formation. Cloverly channel sands show width-depth ratios which are consistent with Holocene meandering systems. The Cloverly Formation was part of a rapidly aggrading alluvial plain with swamps and meandering fluvial systems. This aggradation limited development of fining upward sequences. Rapid aggradation was correlated also to either a large clastic influx from the Sevier orogenic belt, or a rise in sea level causing aggradation within stream valleys, or both.

Phillips, B.E.

1985-01-01

49

9.23 Fluvial Terraces Frank J. Pazzaglia  

E-print Network

University Bethlehem, PA 18015 610.758-3667; 3677 FAX fjp3@lehigh.edu Synopsis Fluvial terraces are landforms. Introduction Fluvial terraces are common, globally-distributed landforms underlain by alluvial deposits, mining, and natural science literature referred to flat landforms in river valleys in the general terms

Pazzaglia, Frank J.

50

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

Microsoft Academic Search

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

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

51

Instituto Universitario del Agua y de las Ciencias Ambientales  

E-print Network

Sánchez Sánchez http://iuaca.ua.es Organiza: Patrocina: AGUA, ARQUITECTURA Y PAISAJE EN EUROPA 21 nov ua idraulico Sara Maldina (Universidad de Ferrara) 12:30 Arquitectura, agua y paisaje en algunas ciudades en Europa" 18:00 Exposición de la oferta docente y de investigación en arquitectura, agua y paisaje

Escolano, Francisco

52

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 de Sierra Nevada. A. Castillo (1993) 2 LAS AGUAS DE SIERRA NEVADA Capítulo I.- EL AGUA EN SIERRA

Castillo, Antonio

53

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

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

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

54

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

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

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

55

Identificacin de Humedales en Puerto Rico utilizando Imgenes Multiespectrales Lola Xiomara Bautista Rozo  

E-print Network

salada. 3) Ciénagas de agua salada. 4) Pantanos de agua salada o manglares. 5) Acuático de agua dulce. 6) Ciénagas de agua dulce. 7) Pantano de agua dulce. Poseer información sobre la existencia y características

Gilbes, Fernando

56

Fluvial Processes Project - Analysis of Redwood Creek Field Data  

NSDL National Science Digital Library

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

Leonard Sklar

57

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

58

THEMIS Observations of Fluvial Landforms on Mars  

NASA Astrophysics Data System (ADS)

The THEMIS (Thermal Emission Imaging System) instrument onboard Mars Odyssey 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. All of the major outflow channels, valley networks and fossae related channel systems have been imaged thus far in the mission. Outflow Channels: the source regions contain large blocks of 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). A similar relationship is also seen on the large mesas and buttes near the mouths of several outflow channels (Kasei and Ma'Adim Valles). Channel floor regions located near the mouths of some outflow channels (Ares, Maja, and Kasei Valles) appear to be very rocky. This is most likely the result of deep erosion and stripping of the bedrock by plucking and scouring from high velocity flows. However, Tiu Vallis doesn't show this type of stripping. This may be due to waning stage deposition of fines, and or lower flow velocities and shallower channel incision, which failed to reach the bedrock material. Some streamlined islands (Ares, Athabasca and Mangala Valles) have coarse (rocky) prows, flanks and tails. These may be deposits of coarse bedload (boulders) or erosion and exposure of the rocky material which makes up the islands. Preliminary observations of some islands suggest that these are depositional rather than erosional bedforms. Valley Networks: layers are commonly seen in the upper regions of the walls of these systems. Narrow, incised, discontinuous inner channels with finer grained materials are also seen on the floors of some valley networks (Bahram and Nanedi Valles). Maumee Vallis appears to have pendant shaped features (bars?) near the mouth. Samara Vallis and an unnamed channel have terminal deposits located at their mouths (fans?). Valley network dissection also appears much more prevalent in some regions (Libya Montes) than has ever been seen before. Fossae related channel systems, such as Athabasca, Granicus, Hebrus, and Hrad Valles; and Olympica and Hephaestus Fossae, located near the Tharsis and Elysium volcanic provinces have also been studied. These channels systems are most likely the result of volcano ground ice/water interactions. This makes these systems high priority geologic and astrobiologic targets for future landed missions. Preliminary observations and geologic interpretations of martian fluvial landforms will be presented; early results indicate that Mars has had a very rich and complex fluvial history.

Rice, J. W.; Christensen, P. R.; Malin, M. C.; McEwen, A. S.

2002-12-01

59

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

60

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

61

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

62

Field methods for measurement of fluvial sediment  

USGS Publications Warehouse

This chapter describes equipment and procedures for collection and measurement of fluvial sediment. The complexity of the hydrologic and physical environments and man's ever-increasing data needs make it essential for those responsible for the collection of sediment data to be aware of basic concepts involved in processes of erosion, transport, deposition of sediment, and equipment and procedures necessary to representatively collect sediment data. In addition to an introduction, the chapter has two major sections. The 'Sediment-Sampling Equipment' section encompasses discussions of characteristics and limitations of various models of depth- and point-integrating samplers, single-stage samplers, bed-material samplers, bedload samplers, automatic pumping samplers, and support equipment. The 'Sediment-Sampling Techniques'` section includes discussions of representative sampling criteria, characteristics of sampling sites, equipment selection relative to the sampling conditions and needs, depth and point-integration techniques, surface and dip sampling, determination of transit rates, sampling programs and related data, cold-weather sampling, bed-material and bedload sampling, measuring total sediment discharge, and measuring reservoir sedimentation rates.

Edwards, Thomas K.; Glysson, G. Douglas

1999-01-01

63

Holocene fluvial processes in Troy plain  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

64

EL PLURIVERSO DEL AGUA. DISCURSOS, IMAGINARIOS Y CONTRATOS EN EL CONFLICTO DEL AGUA  

Microsoft Academic Search

Un buen modo de abordar el conflicto del agua consiste en prestar atención al nivel de los discursos. De este modo se puede poner de manifiesto los modos tan distintos de experimentar e interpretar la realidad que tienen los actores que en tal conflicto inter- vienen. Ahora bien, como algunos discursos enunciados no tienen el suficiente poder retórico y político

J. Ángel B ERGUA

65

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

66

EL ACCESO AL AGUA EN MÉXICO ¿UN DERECHO HUMANO?  

Microsoft Academic Search

El acceso al agua es un pilar fundamental para el desarrollo de la humanidad y, por lo tanto, de los derechos humanos, los cuales son intrínsecos a las personas, pues se trata de los valores y garantías necesarias para la existencia, bienestar y progreso del individuo. En el régimen jurídico constitucional mexicano el acceso al agua es un derecho fundamental,

Daniel Jacobo Marín

2010-01-01

67

Plan estratégico sectorial de agua potable y saneamiento de Paraguay  

Microsoft Academic Search

Esta nota técnica contiene la exposición del Plan Estratégico Sectorial de Agua Potable y Saneamiento de Paraguay elaborado para la Unidad de los Servicios de Agua Potable y Alcantarillado Sanitario (USAPAS) del Ministerio de Obras Públicas y Comunicaciones (MOPC) del gobierno paraguayo. El documento presenta en primer lugar datos sobre la situación administrativa y el contexto socioeconómico del país, así

Diego Fernández; Carlos Arturo Aguilera; Juan Bóbeda; Julio Giménez

2010-01-01

68

Fluvial network organization imprints on microbial co-occurrence networks.  

PubMed

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

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

2014-09-01

69

Fluvial network organization imprints on microbial co-occurrence networks  

PubMed Central

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

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

2014-01-01

70

Fluvial to Lacustrine Facies Transitions in Gale Crater, Mars  

NASA Technical Reports Server (NTRS)

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

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

2015-01-01

71

River Self-Restoration: Interactions between Plants and Fluvial Processes  

NASA Astrophysics Data System (ADS)

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

Gurnell, Angela

2014-05-01

72

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

NASA Astrophysics Data System (ADS)

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

Mangold, N.

2009-12-01

73

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

74

Fluvial landforms on fresh impact ejecta on Mars  

NASA Astrophysics Data System (ADS)

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

Mangold, N.

2012-03-01

75

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

76

May 2004 / Vol. 54 No. 5 BioScience 413 Principles of fluvial geomorphology have guided  

E-print Network

May 2004 / Vol. 54 No. 5 · BioScience 413 Articles Principles of fluvial geomorphology have guided river continuum concept (RCC;Vannote et al.1980).Based on early principles of fluvial geomorphology (e

77

Simulating the development of martian highland landscapes through the interaction of impact cratering, fluvial erosion,  

E-print Network

cratering, fluvial erosion, and variable hydrologic forcing Alan D. Howard Department of Environmental in the planet's history precipitation-driven fluvial erosion competed with ongoing impact cratering craters, erosion by fluvial and slope processes, deposition in basins, and flow routing through

Howard, Alan D.

78

The Australian Paleoflood Model for Unconfined Fluvial Deposition on Mars  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

79

Fluvial geomorphic features of the Lower Mississippi alluvial valley  

Microsoft Academic Search

The Lower Mississippi Valley (LMV) has been one of the most intensively studied alluvial valleys in the world in terms of it's geological and geomorphic framework and history. A brief outline of the history of the major geological and geomorphological investigations of the LMV is provided. The results of these investigations are discussed in terms of the fluvial geomorphic framework

Lawson M. Smith

1996-01-01

80

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

81

Fluvial network imprints on microbial diversity and community network topology  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

82

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

83

Geography 547: Fluvial Geomorphology Initial Reading List, Fall, 2014  

E-print Network

.), Introduction to Fluvial Processes. NY: Methuen & Co., Ltd. (grads only) Week 5. Flood Frequency Analysis 1 watersheds: U.S. Geological Survey. 44-46. (Grads scan) Week 7. Spatial Analysis James, L.A. nd. Watersheds. Types and classes of channels 1. Schumm, S.A. 2005. River Variability and Complexity, Cambridge Univ

James, L. Allan

84

Microbiological and geochemical characterization of fluvially deposited sulfidic mine tailings  

Microsoft Academic Search

The fluvial deposition of mine tailings generated from historic mining operations near Butte, Montana, has resulted in substantial surface and shallow groundwater contamination along Silver Bow Creek. Biogeochemical processes in the sediment and underlying hyporheic zone were studied in an attempt to characterize interactions consequential to heavy-metal contamination of shallow groundwater. Sediment cores were extracted and fractionated based on sediment

BRUCE WIELINGA; JULIETTE K. LUCY; JOHNNIE N. MOORE; OCTOBER F. SEASTONE; JAMES E. GANNON

1999-01-01

85

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

86

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

87

Assessing the relative efficiency of fluvial and glacial erosion through simulation of fluvial landscapes  

NASA Astrophysics Data System (ADS)

The relative rates of erosion by rivers and glaciers, and the topographic effects of these two different styles of erosion, remain outstanding problems in geomorphology. We use a quantitative description of local fluvial landscapes to estimate how glaciated landscapes might look now had glaciers not developed. This indicates the landscape modification attributable to glacial erosion. We present examples from the Sierra Nevada, California and the Sangre de Cristo Range, Colorado. In smaller drainage basins, glacial modification is focussed above the mean Quaternary equilibrium line altitude (ELA), where both ridgelines and valley floors have been lowered as a consequence of glaciation. At lower elevations, small glaciers have apparently widened valleys without incising the valley floor beyond what a river would have. This may reflect the short residence time of the glaciers at their full extent, or differences in the subglacial drainage network between the glacier margins and the thalweg. In larger drainage basins, the pattern of glacial erosion is dramatically different. Here, the glaciers have modified longitudinal profiles, as well as valley cross sections, far below the mean Quaternary ELA. Possible causes of this difference in the larger basins include the larger accumulation area, greater shading of the valley floor, longer residence times for ice at its full extent, and the influence of the shallower valley slope prior to glaciation on the subsequent glacier and subglacial drainage conditions.

Brocklehurst, Simon H.; Whipple, Kelin X.

2006-05-01

88

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 dientes ni las toallas. Al toser o estornudar, cubrase la boca con la parte superior del brazo o el codo

89

Hillslope to fluvial process domain transitions in headwater catchments  

NASA Astrophysics Data System (ADS)

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

Williams, Karen Mary

90

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

E-print Network

program. Cornell designed AguaClara municipal water treatment plants in Honduras are providing over 13 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

Angenent, Lars T.

91

Role of threshold response in incremental forcing of fluvial stratigraphy  

NASA Astrophysics Data System (ADS)

A preliminary compilation of alluvial architecture studies suggests that channel stacking densities in ancient fluvial successions tend to be mudstone dominated (<50% sand) or strongly sandstone dominated (>80% sand) with relatively few examples in between. Such disparity in stacking is commonly attributed to abrupt, allogenic forcing such as the onset of thrusting or climate change. In contrast, we suggest that this gap in stacking density could arise from threshold responses during fluvial basin filling. We consider two models that can generate relatively dramatic stacking pattern changes when a critical threshold is surpassed, even under steadily and/or gradually varying boundary conditions. In the first model bank erosion rates are controlled by previously deposited substrate. Floodplain deposits retard bank erosion rates, whereas channel sands exposed in cut banks, promote channel migration and meandering. As overall aggradation rates decline in a basin, channels become increasingly likely to intersect older channel deposits during avulsion, at which point lateral sweeping becomes more prominent. Stratigraphically this results in a rapid transition from isolated channel belt deposits to more sheet-like channel bodies, and an overall increase in stacking density. The second approach considers the role of floodplains in confining channels and limiting channel width. Small, gradual changes in climate or sediment supply could deteriorate the floodplain to a point of catastrophic unraveling. The resultant reduction in bank strength leads to wholesale change in river meandering rate and possibly river pattern, which abruptly changes the stratigraphic character of fluvial deposits. Both models produce sudden changes in channel stacking patterns from incremental changes in allogenic forcing. Consequently threshold responses in fluvial basin filling may, at times, overemphasize the role of extrinsic boundary conditions in the stratigraphic record.

Heller, P.; Hajek, E. A.; Paola, C.

2009-12-01

92

Estimates of fluvial erosion on Titan from sinuosity of lake shorelines  

NASA Astrophysics Data System (ADS)

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 resurfacing by estimating the cumulative erosion around the margins of polar lakes. A scarcity of detailed topographic data makes it difficult to measure fluvial incision on Titan, but images of drowned fluvial features around the lake margins, where elevated levels of hydrocarbon liquids appear to have partly flooded fluvial valleys, offer a constraint on the topography. We mapped the shorelines of several lakes to obtain topographic contours that trace the fluvially dissected topography. We then used a numerical landscape evolution model to calibrate a relationship between contour sinuosity, which reflects the extent of fluvial valley incision, and cumulative erosion. We confirmed this relationship by analyzing a partially dissected surface adjacent to the Minnesota River, USA. Comparison of the mapped Titan contours with the sinuosity-erosion relationship suggests that cumulative fluvial erosion around the margins of Titan's polar lakes, including Ligeia Mare, Kraken Mare, and Punga Mare in the north and Ontario Lacus in the south, ranges from 4% to 31% of the initial relief. Additional model simulations show that this amount of fluvial erosion does not render craters invisible at the resolution of currently available imagery, suggesting that fluvial erosion is not the only major resurfacing mechanism operating in Titan's polar regions.

Tewelde, Yodit; Perron, J. Taylor; Ford, Peter; Miller, Scott; Black, Benjamin

2013-10-01

93

A Search for Unconfined Fluvial Outflow Deposits on Mars  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

94

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

95

Headwaters are critical reservoirs of microbial diversity for fluvial networks  

PubMed Central

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

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

2013-01-01

96

A Search for Unconfined Fluvial Outflow Deposits on Mars  

NASA Astrophysics Data System (ADS)

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

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

2000-08-01

97

Marine vsFluvial Suspended Matter in the Scheldt Estuary  

NASA Astrophysics Data System (ADS)

The ratio of marine to fluvial suspended matter in the Scheldt Estuary was calculated by applying factor analysis to a data set of elemental concentrations. The data set consisted of 98 samples collected under various river discharge conditions. Each sample was analysed for the concentration of Cr, Pb, Fe, Mn, Ni, Co, Ba, Zn, Cu, Cd, S, Ca, Sr, Ag, Sn and Na. Five linearly independent processes were found to describe the variability of the elemental concentrations: (1) the supply of fluvial material to the mixing zone; (2) manganese oxidation in the transition area between the anoxic upper estuary and the oxic lower estuary; (3) the supply of marine material to the mixing zone; (4) a phytoplankton bloom in the lower estuary; and (5) the formation of insoluble metal sulphides in the anoxic high-turbidity zone. Scores of the first and third factor were used to calculate the ratio of marine to fluvial suspended matter in the mixing zone. Information on the origin of both the inorganic and organic fraction of suspended matter was obtained in this way.

Verlaan, P. A. J.; Donze, M.; Kuik, P.

1998-06-01

98

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

99

Listeria monocytogenes aguA1, but not aguA2, encodes a functional agmatine deiminase: biochemical characterization of its catalytic properties and roles in acid tolerance.  

PubMed

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

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

2013-09-13

100

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

101

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

USGS Publications Warehouse

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

Simon, A.

1992-01-01

102

Los servicios de agua potable en Chile: Condicionantes, institucionalidad y aspectos de economía política  

Microsoft Academic Search

El sector sanitario en Chile ha tenido un importante desarrollo en los últimos 30 años, alcanzando en 1995 una cobertura urbana del 98% en agua potable y del 89% en evacuación de aguas servidas (alcantarillado). Entre la década del 70 y la actualidad, aumentó significativamente la cobertura de agua potable y alcantarillado, se aplicó un esquema tarifario que permite el

Felipe G. Morandé; Juan E. Doña

1997-01-01

103

Modelling complex geomorphic systems: the example of fluvial obstacle marks  

NASA Astrophysics Data System (ADS)

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

Euler, Thomas

2010-05-01

104

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

105

Ancient fluvial processes in the equatorial highlands of Mars  

NASA Technical Reports Server (NTRS)

Martian highland craters typically lack ejecta deposits, have no noticeable rim, and are flat floored. In addition, crater size frequency distribution curves show that highland craters have depleted populations less than 20 km in diameter. A variety of processes have been suggested to explain these observations including deposition of aeolian or volcanic materials up to the crater rim crests, thermal creep, terrain softening, and mass wasting. However, none of these processes adequately explains both the crater morphology and population distribution. In order to explain both the Martian highland crater morphology and population distribution, a fluvial process is proposed which is capable of removing the loose crater rim material. The resulting effect is to decrease the crater diameter, thereby causing the population curves to bendover. The eroded material is redistributed, burying or partially burying smaller diameter craters before complete erosion. This material may also be deposited into local topographic lows, creating the depositional basins observed. A fluvial process explains both sets of observations: crater morphology and crater population distribution curves.

Craddock, Robert A.; Maxwell, Ted A.

1991-01-01

106

Fluvial sediment fingerprinting: literature review and annotated bibliography  

USGS Publications Warehouse

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

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

2014-01-01

107

Optimality approaches to describe characteristic fluvial patterns on landscapes  

PubMed Central

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

Paik, Kyungrock; Kumar, Praveen

2010-01-01

108

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

109

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

110

Climatic control on quaternary fluvial sedimentation in the kleszczów graben, central Poland  

Microsoft Academic Search

The Pleistocene sequence of the Kleszczów Graben, central Poland, comprises seven fluvial series, ranging in age from Pre-Tiglian to Holocene. These sequences are investigated in terms of graben tectonics that existed up to the Middle Pleistocene and climate change ranging from periglacial to cool temperate. Warm temperate (interglacial) fluvial deposits are virtually absent. There is no evidence for tectonic control

Dariusz Krzyszkowski

1996-01-01

111

Riparian shrub metal concentrations and growth in amended fluvial mine tailings  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

112

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. Interpreta- tions using terrestrial analogs and process mechanics extend our perspective on fluvial geomorphology to another world and offer insight into their formative processes. At the landscape scale

Wang, Xiaorui "Ray"

113

12.5 Riparian Vegetation and the Fluvial Environment: A Biogeographic Perspective  

E-print Network

12.5 Riparian Vegetation and the Fluvial Environment: A Biogeographic Perspective J Bendix 12.5.2 Early History: Pattern and Process in Riparian Zones 54 12.5.3 Influence of Hydrogeomorphology the historical arc of research on biogeomorphic interactions between fluvial geomorphology and riparian

Stella, John C.

114

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

115

Oceanographic Processes in the Region of Fluvial Influence of the Itajaí-Açu River  

Microsoft Academic Search

The oceanographic processes in the region of fluvial influence (ROFI) of the Itajaí-Açu river were assessed through fourteen monthly surveys from November 2002 until December 2003. The main objective of this study was to investigate the effects of the fluvial riverine in the physical, biogeochemical and biological processes in the ROFI. Twenty eight sampling stations were positioned in five transects

C. A. Schettini; E. C. Truccolo; J. Pereira; L. R. Rörig; C. Resgalla

2005-01-01

116

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

E-print Network

channels over geolog- ical timescales, sediment supply and discharge variations resulting from extreme and fluvial response in the Tachia River, central Taiwan, documents highly episodic sediment supply over (2001, 2004, and 2005) quantify the sediment supply from these events. Fluvial response was investigated

Montgomery, David R.

117

Z .Geomorphology 31 1999 265290 Time and the persistence of alluvium: River engineering, fluvial  

E-print Network

Z .Geomorphology 31 1999 265­290 Time and the persistence of alluvium: River engineering, fluvial geomorphology, and mining sediment in California Allan James UniÕersity of South Carolina, USA Received 28 interpretations and is essential to a full understanding of the behavior of fluvial systems. Geomorphology

James, L. Allan

118

Regional paleoclimatic and stratigraphic implications of paleosols and fluvial/overbank architecture in the Morrison Formation  

E-print Network

Regional paleoclimatic and stratigraphic implications of paleosols and fluvial/overbank (Upper Jurassic) from the Western Interior and Colorado Plateau regions occur in fluvial/overbank times of relatively slow or no accumulation of sediment. During these times, the land surface and near

Nicoll, Kathleen

119

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

120

Salida de operadores privados internacionales de agua en América Latina  

Microsoft Academic Search

Hacia fines de los años noventa un número significativo de países de América Latina contaba con la presencia de importantes operadores internacionales en el sector de servicios de agua potable y alcantarillado. Se esperaba que este proceso se siguiera expandiendo y profundizando. Sin embargo, a mediados de la primera década del nuevo siglo se observa que la mayoría de los

Jorge Ducci

2007-01-01

121

Definition of mass-balance frameworks for interacting fluvial systems with application to Bangladesh  

NASA Astrophysics Data System (ADS)

Sediment extraction is a powerful concept for analyzing proximal-to-distal geomorphic and stratal trends within fluvial systems. A useful starting point for understanding this process in fluvial systems is the mass-balance framework, a conversion from length scales to sediment-extraction scales within a depositional basin. We attempt to isolate the mass-balance frameworks of fluvial systems which are near enough to one another to potentially interact as tributary systems. To do so, we must define the boundaries between the depositional provinces of each individual fluvial system. The depositional province is the domain within a larger basin within which only a single fluvial system may deposit sediments, as determined by the subsidence pattern within the basin and the sediment discharges of the fluvial system and its neighboring fluvial systems. Numerical modeling is applied to track the local sediment discharge of point-sourced fluvial systems within a subsiding model basin. The point-sourced fluvial systems create radial fans within the basin which are analogous to the cumulative floodplain extent of an avulsing river. The extent of these fans is determined by the balance between the amount of sediment available to each system and the amount of space created by subsidence near the point sources. The boundary between depositional provinces of adjacent fluvial systems is initially determined by the point on the line between point sources at which the local sediment discharges of each system are equal. A new radiating fluvial fan is then developed from the sediment available at this point, and the positions of equal sediment discharge between this new fan and the original fans are calculated. In this way, depositional provinces are created for each adjacent point-sourced fluvial system, as well as a domain between the provinces within which the systems become tributary. Mass-balance frameworks can then be constrained for each fluvial system, and depositional signals can be isolated for individual rivers. The Ganges-Jamuna-Meghna river system in Bangladesh provides an example of three interacting fluvial systems which are currently tributary, but which may have not had confluence at times during the Holocene. This modeling effort is in support of core-transect drilling in Bangladesh aimed at understanding how these rivers have responded to tectonic forcing in the Holocene. Definition of depositional provinces for each river could aid in the recognition and distinction of stratal patterns caused by tributary input from those caused by tectonism.

Petter, A. L.; Paola, C.; Goodbred, S. L.; Pickering, J.; Williams, L.

2012-12-01

122

Estimates of Fluvial Erosion on Titan from Sinuosity of Lake Shorelines  

NASA Astrophysics Data System (ADS)

Synthetic Aperture Radar (SAR) images of Titan's surface from the Cassini spacecraft have revealed extensive fluvial networks, many of which drain into polar lakes. Titan has fewer impact craters than other icy moons, suggesting a relatively young surface. Plausible resurfacing mechanisms on Titan include cryovolcanism, tectonic deformation, deposition of organic aerosols, deposition of wind-borne sediment, and fluvial erosion. Determining which of these processes are significant is essential to understanding Titan's geologic history. We present estimates of fluvial erosion based on SAR images of drowned fluvial features on the margins of Titan's polar lakes. Elevated levels of hydrocarbon liquids appear to have partly filled fluvial valleys in some of the north polar lakes. Assuming that each lake level is a surface of constant gravitational potential, we mapped the shoreline of each lake to obtain an estimate of a topographic contour that traces the fluvially dissected topography. We then used a numerical landscape evolution model to calibrate a relationship between contour sinuosity and cumulative erosion (as a fraction of the initial topographic relief). Comparisons of the mapped Titan contours with the model-calibrated sinuosity-erosion relationship suggests that cumulative fluvial erosion around the margins of Titan's polar lakes ranges from 4% to 31% of the initial relief. This includes contours from Ligeia Mare, Kraken Mare, and Punga Mare in the north polar region and Ontario Lacus near the south polar region. This range is somewhat larger than a previous estimate for the average fluvial erosion over a larger area in the north polar region, which was based on the relationship between network geometries and cumulative erosion. This suggests that initial fluvial dissection around the north polar lakes has been more extensive near the lake margins than in areas further from the lakes. This trend is consistent with the interpretation that drainage networks have propagated upstream from the lake margins as fluvial erosion has acted on a rough initial surface.

Tewelde, Y.; Perron, J.; Ford, P. G.; Black, B. A.; Miller, S. R.

2012-12-01

123

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

124

Active tectonics coupled to fluvial erosion in the NW Himalaya  

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

125

From Fundamental Physical Fluvial Processes To River Patterns  

NASA Astrophysics Data System (ADS)

Rivers are ubiquitous on planetary surfaces and their patterns show great variation. The fundamental fluvial processes of flow and sediment transport are relatively well understood, solvable in linearized form and implemented in sophisticated nonlinear numerical models. We successfully modeled formation and evolution of large-scale and long-term patterns that look like braided and meandering river. But what characterizes and discriminates the patterns, and how do the modeled patterns quantitatively compare to natural patterns? Here we focus on characteristics of fluvial bars as building blocks of river patterns. Bars are much larger than grid cells and emerge at length scales predictable by analytical solutions. We used the morphodynamic numerical model Delft3D, which solves the 3D flow and computes sediment transport and bed level change, incorporating the effect of transverse bed slope. We identify bars as connected sand bodies above the average bed level and characterize their shape quantitatively. To reduce computational time and allow high resolution long-term calculations, bed level changes are multiplied by a morphological factor O(100) for each flow time step. This assumes that no significant morphodynamics occur at the time scale in which significant flow takes place. At the moment, desktop computers allow high-resolution century-scale calculations for the largest rivers on Earth. The results show that both meandering and braiding rivers can be modeled by solving the flow and sediment dynamics, and can be characterized by bars. In meandering rivers streamline curvature and bank erosion leads to formation of scroll bars. In braided rivers, large compound bars are formed by merging of unit bars, forming scroll-bars, and smaller compound bars. The results show that nonlinear numerical solution of small-scale flow and sediment transport results in realistic large scale river patterns depending on boundary conditions. As attested by verification in many engineering applications of this model, a second-order (nonlinear) numerical scheme and the transverse bed slope effect are essential for accurate bar dimensions which have not been reproduced in cellular automata. We conclude that a reductionist approach at realistic fluvial landscape modeling is feasible given growing computing power, and successful when evaluated on quantitative characteristics of emergent landforms that compose the landscape.

Schuurman, F.; Kleinhans, M. G.; Geurts, A. H.

2012-12-01

126

Water soluble cations and the fluvial history of Mars  

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

127

Modeling post-wildfire fluvial incision and terrace formation  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

128

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

129

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

130

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

131

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

132

Episodes of fluvial and volcanic activity in Mangala Valles, Mars  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

133

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

SciTech Connect

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

Whicker, Jeffrey J [Los Alamos National Laboratory; Field, Jason P [UNIV OF ARIZONA; Breshears, David D [UNIV OF ARIZONA

2008-01-01

134

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

135

Segmentação, Indexação e Recuperação de Vídeo Utilizando OpenCV  

Microsoft Academic Search

Resumo: Os constantes avanços em poder de processamento, capacidade de armazenamento, e largura de banda tornaram possível ao usuário de com- putadores o acesso, manipulação e edição de imagens e vídeos digitais. Nesse tutorial, vamos descrever alguns algoritmos de visão computacional para a seg- mentação, indexação e recuperação de vídeo utilizando o OpenCV para que, ao final do tutorial, você

Thiago Teixeira Santos; Carlos Hitoshi Morimoto

136

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

137

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

138

What can we learn from fluvial incision in high mountains?  

NASA Astrophysics Data System (ADS)

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

Fuchs, Margret; Gloaguen, Richard; Krbetschek, Matthias

2013-04-01

139

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

140

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

SciTech Connect

The authors found Warpinski et al.'s paper (Case Study of a Stimulation Experiment in Fluvial, Tight-Sandstone Gas Reservoir. Nov. 1990 SPE Production Engineering, Pages 403-10) to be very thorough and informative. That paper considered geological, logging, completion, and pressure-transient data to produce a comprehensive formation evaluation of a fluvial, tight-sandstone gas reservoir. The purpose of this paper is to present the author's view on the peculiar pressure-transient responses shown.

Azari, M.; Wooden, W. (Halliburton Reservoir Services (GB))

1991-08-01

141

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

Microsoft Academic Search

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

W. R. Osterkamp; W. Anklam

1998-01-01

142

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

143

Geomorphic evolution of the Martian highlands through ancient fluvial processes  

NASA Technical Reports Server (NTRS)

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

Craddock, Robert A.; Maxwell, Ted A.

1993-01-01

144

Evidence for late stage fluvial activity in Kasei Valles, Mars  

NASA Astrophysics Data System (ADS)

Two inner channels in the southern branch of Kasei Valles are among the best preserved examples of fluvial erosion on Mars. Attributes of the channels include arcuate alcoves, perched boulders, and a concave-up longitudinal profile, all of which are consistent with the interpretation that these channels were carved by a Newtonian fluid. The sharp concavity of the longitudinal profile is comparable to a terrestrial alluvial system with a minimum work profile. The shape of the profile suggests that the system was in a quasi-equilibrium state but was not active long enough to achieve grade. Associated with these channels is a ``platy'' meter-scale texture, identified in high-resolution Mars Orbiter Camera images. Although a lava flow could explain many of the material properties of the platy surface texture, we speculate that this texture in the immediate proximity to the southern Kasei Valles inner channels may be related to waning floodwaters moving through the inner channels and is a mudflow deposit.

Williams, Rebecca M. E.; Malin, Michael C.

2004-06-01

145

Fluvial Placement of Radioactive Contaminants a Weldon Spring Case Study  

SciTech Connect

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

Meier, J.

2002-02-26

146

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

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

147

Fluvial drainage basins and valley networks: Eastern Margaritifer Sinus, Mars  

NASA Astrophysics Data System (ADS)

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

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

1985-04-01

148

Rivers under ice: fluvial erosion beneath decaying ice sheets  

NASA Astrophysics Data System (ADS)

The century-long debate over the origins of inner gorges cut within larger valleys that were repeatedly covered by Quaternary glaciers hinges upon whether the gorges are fluvial forms eroded by subaerial rivers, or subglacial forms cut beneath ice. We apply cosmogenic nuclide exposure dating to seven inner gorges along ~500 km of the former Fennoscandia ice sheet margin in combination with a new deglaciation isochron map. We show that the timing of bedrock exposure matches the advent of ice-free conditions, strongly suggesting that inner gorges were cut by channelised subglacial meltwater while simultaneously being shielded from cosmic rays by overlying ice. Given the exceptional hydraulic efficiency required for subglacial meltwater channels to erode bedrock and evacuate debris, we deduce that inner gorges are the product of ice sheets undergoing intense surface melting akin to that currently occurring on the Greenland ice sheet. The lack of postglacial river erosion in our seven inner gorges leads us to propose that channelised subglacial meltwater-boosted possibly by abrupt supraglacial lake drainage-may be a key driver of valley deepening on the Baltic Shield over multiple glacial cycles.

Jansen, John D.; Codilean, Alexandru T.; Stroeven, Arjen P.; Fabel, Derek; Hättestrand, Clas; Kleman, Johan; Harbor, Jon M.; Heyman, Jakob; Kubik, Peter W.; Xu, Sheng

2014-05-01

149

Fluvial Morphodynamics: advancing understanding using Multibeam Echo Sounders (MBES)  

NASA Astrophysics Data System (ADS)

Accurately and reliably determining riverbed morphology is key to understanding linkages between flow fields, sediment transport and bed roughness in a range of aquatic environments, including large fluvial channels. Modern shallow-water multibeam echo sounder (MBES) systems are now allowing us to acquire bathymetric data at unprecedented resolutions that are millimetric in precision and centimetric in accuracy. Such systems, and the morphological resolution they can supply, are capable of revealing the complex three-dimensional patterns in riverbed morphology that are facilitating a holistic examination of system morphodynamics, at the field scale, that was unimaginable just a few years ago. This paper presents a range of MBES acquired examples to demonstrate how the methodological developments in this technology are leading to advances in our substantive understanding of large river systems. This includes examples that show linkages across scales, and in particular the morphodynamics of superimposed bedforms and bars revealed by such high-resolution data, which have broad implications for a range of applications, including flood prediction, engineering design and reconstructing ancient sedimentary environments.

Parsons, D. R.; Best, J. L.

2012-12-01

150

Microbiological and geochemical characterization of fluvially deposited sulfidic mine tailings  

SciTech Connect

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

Wielinga, B.; Lucy, J.K.; Moore, J.N.; Seastone, O.F.; Gannon, J.E. [Univ. of Montana, Missoula, MT (United States)

1999-04-01

151

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

152

Hydrodynamic perspectives of soil scour in fluvial environment  

NASA Astrophysics Data System (ADS)

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

Salim, Sarik; Jayaratne, Ravindra

2013-09-01

153

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

154

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

Federal Register 2010, 2011, 2012, 2013, 2014

...Energy Regulatory Commission [Docket No. ER12-21-000] Agua Caliente Solar, LLC; Supplemental Notice That Initial Market-Based...a supplemental notice in the above-referenced proceeding of Agua Caliente Solar, LLC's application for market-based...

2011-10-13

155

Clasificacion de trafico en Internet utilizando metodos estadisticos  

E-print Network

Clasificaci´on de tr´afico en Internet utilizando m´etodos estad´isticos Gabriel G´omez Sena otros tiempos, que me han brindado apoyo y aliento para realizar este trabajo. A Mart´in, Guillermo . . . . . . . . . . . . . . . . . . . 7 2.2. M´etodos de clasificaci´on de tr´afico . . . . . . . . . . . . . . . . 8 2.2.1. An´alisis de

156

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

E-print Network

populación del planeta. Las reservas mundiales de agua dulce están restringidas a una parcela mínima de de agua dulce están restringidas a una parcela mínima de países o en pocos continentes (tabla 1 e 2

Paris-Sud XI, Université de

157

Agua limpia a punta de algas Jueves, 20 de Noviembre de 2014 15:34  

E-print Network

Agua limpia a punta de algas Jueves, 20 de Noviembre de 2014 15:34 Experimento de estudiante de patente. Con un bioreactor capaz de tratar 27 mil litros, el experimento estuvo durante un año en una base petrolera de Campo Rubiales descontaminando el agua, eliminando los desechos tóxicos que le quedan tras el

Amézquita, Adolfo

158

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

Code of Federal Regulations, 2010 CFR

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

2010-04-01

159

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

160

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 en INGENIERÍA CIVIL UNIVERSIDAD DE PUERTO RICO RECINTO UNIVERSITARIO DE MAYAGÜEZ 2009 Aprobado por trabajo presenta la elaboración de un Índice de Calidad de Agua (ICA) para los ríos en Puerto Rico. Dicho

Gilbes, Fernando

161

La contaminación de las aguas subterráneas. : una responsabilidad moral, política y ambiental  

Microsoft Academic Search

RESUMEN.- La utilización de aguas subterráneas para abastecimiento urbano y riego está aumentando en todo el mundo. Así está aumentando el interés por los recursos subterráneos de agua y por su protección de la contaminación. Sin embargo es corriente que los estudios sobre la contaminación de los acuíferos y su protección sean inadecuados o no existan en absoluto. Las agencias

Andrés Sahuquillo Herráiz

162

Participación del sector privado en los sistemas de agua potable y saneamiento: Ventajas, riesgos y obstáculos  

Microsoft Academic Search

El objetivo de este trabajo es analizar la incorporación del sector privado a los servicios de agua y saneamiento desde una doble perspectiva. De un lado, se discute en qué medida la incorporación del sector privado permite romper el círculo de ineficiencia en la que están atrapados la mayoría de los servicios de agua y alcantarillado en la región y

Paulina Beato

1997-01-01

163

EL VALOR DE LA PRODUCTIVIDAD MARGINAL DEL AGUA EN LA INDUSTRIA MANUFACTURERA COLOMBIANA  

Microsoft Academic Search

Este estudio considera el valor de la productividad marginal del agua en la industria manufacturera colombiana. Su estimación se realiza con información proveniente de aquellos establecimientos industriales que reportaron algún consumo de agua como materia prima, agregados a cuatro dígitos CIIU, en la Encuesta Anual Manufacturera (EAM), durante el periodo 1992 - 1999. A través de la estimación de una

Martha Patricia Cruz; Eduardo Uribe; Harold Coronado

2003-01-01

164

Un modelo econométrico sobre el consumo de agua en el estado de Guanajuato  

Microsoft Academic Search

El problema del agua se agudiza debido a cuestiones de baja eficiencia en el uso del recurso. Por lo general, los volúmenes de agua que se aplican a los cultivos exceden a sus requerimientos. Entre los cultivos de más baja eficiencia se encuentra la alfalfa, uno de los insumos importantes para la producción pecuaria del Estado. De acuerdo a investigaciones

Eugenio Guzman Soria

2006-01-01

165

EFICIENCIA DEL USO DEL AGUA EN LA PRODUCCIÓN AGRICOLA EN GUATEMALA  

Microsoft Academic Search

Los estudios de ciclo de vida, hasta hoy en día, han tenido en cuenta principalmente, los flujos de energía y materiales, no existiendo acuerdo en como tratar el recurso agua, siendo éste uno de los factores que deberían considerarse, especialmente en los sistemas de producción agrícolas. El manejo del agua en agricultura, asociado a su escasez, es uno de los

Willian E. de León; Asunción Antón

166

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

167

Fluvial erosion and post-erosional processes on Titan  

USGS Publications Warehouse

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

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

2008-01-01

168

Methodological sensitivity of morphometric estimates of coarse fluvial sediment transport  

NASA Astrophysics Data System (ADS)

The estimation of fluvial sediment transport rate from measurements of morphological change has received growing recent interest. The revival of the 'morphological method' reflects continuing concern over traditional methods of rate determination but also the availability of new survey methods capable of high-precision, high-resolution topographic monitoring. Remote sensing of river channels through aerial digital photogrammetry is a potentially attractive alternative to labour intensive ground surveys. However, while photogrammetry presents the opportunity to acquire survey data over large areas, data precision and accuracy, particularly in the vertical dimension are lower than in traditional ground survey methods. This paper presents results of recent research in which digital elevation models (DEMs) have been developed for a reach of a large braided gravel-bed river in Scotland using both digital photogrammetry and high-resolution RTK GPS ground surveys. A statistical level of change detection is assessed by comparing surfaces with independent check points. The methodological sensitivity of the annual channel sediment budget (1999-2000) to the threshold is presented. Results suggest that while the remote survey methods employed here can be used to develop qualitatively convincing, moderate precision DEMs of channel topography (RMSE=±0.21 m), the remaining errors imply significant limits on reliable change detection which lead to important information losses. Tests at a 95% confidence interval for change detection show that over 60% of channel deposition and 40% of erosion may be obscured by the lower level of precision associated with photogrammetric monitoring when compared to ground survey measurements. This bias reflects the difficulty of detecting the topographic signature of widespread, but shallow deposition on bar tops.

Brasington, James; Langham, Joe; Rumsby, Barbara

2003-07-01

169

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

170

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

171

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

172

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

173

Cauvery River: Late Quaternary Fluvial Process and landforms  

NASA Astrophysics Data System (ADS)

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

Stalin, Manjula; Achyuthan, Hema

2014-05-01

174

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

175

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

NASA Technical Reports Server (NTRS)

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

Wilkinson, M. Justin; Herridge, A.

2013-01-01

176

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

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

177

Longitudinal fluvial drainage patterns within a foreland basin-fill: Permo-Triassic Sydney Basin, Australia  

NASA Astrophysics Data System (ADS)

The north-south trending Permo-Triassic Sydney Basin (southern sector of the Sydney-Bowen Basin) is unique compared to many documented retro-arc foreland basins, in that considerable basin-fill was derived from a cratonic source as well as a coeval fold belt source. Quantitative analysis of up-sequence changes in sandstone petrography and palaeoflow directions, together with time-rock stratigraphy of the fluvial basin-fill, indicate two spatially and temporally separated depositional episodes of longitudinal fluvial dispersal systems. A longitudinal drainage-net similar in geometry to the modern Ganga River system (reduced to 60% original size) explains many of the palaeoflow patterns and cross-basinal petrofacies variation recorded in the basin-fill. The Late Permian to Early Triassic rocks reveal a basin-wide southerly directed fluvial drainage system, contemporaneous with east-west shortening recorded in the New England Fold Belt. In contrast, the Middle Triassic strata reveal a change to an easterly directed fluvial system, correlated to a shift in orogenic load to a NW-SE orientation in the fold belt northeast of the basin. The detailed petrofacies variation in the deposits of the second longitudinal fluvial dispersal system reveals vertical jumps in petrofacies compositions, with uniform compositions between jumps. The petrological jumps are interpreted as the result of minor fault adjustments in the fold belt, resulting in changing rates of sediment supply to the foreland basin. Uninterrupted erosion of the same terrain most likely caused the compositional uniformity between jumps. The identification of similar longitudinal fluvial systems, with transverse variation in detrital composition, is likely to help resolve the tectonic history of foreland fold belts elsewhere.

Cowan, E. Jun

1993-05-01

178

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

179

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

180

La Transpiración - Movimiento del Agua a Través de las Plantas  

NSDL National Science Digital Library

La transpiración es la pérdida de agua en forma de vapor por las plantas. El agua es absorbida del suelo por las raíces y transportada en forma líquida por el xilema hacia las hojas. En las hojas, unos pequeños poros permiten que el agua (H2O) escape a la atmósfera en forma de vapor, al tiempo que se permite la entrada de bióxido de carbono (CO2) para la fotosíntesis. De toda el agua absorbida por las plantas, menos del 5% es retenida y utilizada para crecimiento y almacenamiento. En esta lección se explicará porque las plantas pierden tanta agua, la ruta que ésta sigue dentro de la planta, como pudieran las plantas controlar la pérdida excesiva de agua y como las condiciones ambientales influyen en la pérdida de agua por las plantas.

181

Fluvial-sediment discharge to the oceans from the conterminous United States  

USGS Publications Warehouse

This report is a contribution to the UNESCO-sponsored project of the International Hydrological Decade called the World Water Balance. Annual fluvial-sediment discharge from the conterminous United States averages 491,449,600 short tons, of which 14,204,000 is discharged to the Atlantic Ocean, 378,179,000 to the Gulf of Mexico, and 99,066,600 to the Pacific Ocean. Data from 27 drainage areas were used to estimate the average annual discharge, yield, and concentration of fluvial sediment. The data may be used to extrapolate part of the total world sediment yield to the marine environment.

Curtis, Westley Farnsworth; Culbertson, James J.; Chase, Edith B.

1973-01-01

182

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

NASA Astrophysics Data System (ADS)

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

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

2007-04-01

183

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

Microsoft Academic Search

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

L. S. Land; L. E. Mack

1987-01-01

184

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

NASA Technical Reports Server (NTRS)

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

Bourke, M. C.

2003-01-01

185

GEOTOOLS: A TOOLKIT FOR FLUVIAL SYSTEM ANALYSIS1 Brian P. Bledsoe, Michael C. Brown, and, David A. Raff 2  

E-print Network

GEOTOOLS: A TOOLKIT FOR FLUVIAL SYSTEM ANALYSIS1 Brian P. Bledsoe, Michael C. Brown, and, David A.) Bledsoe, Brian P., Michael C. Brown, and David A. Raff, 2007. GeoTools: A Toolkit for Fluvial System lack of rig- orous quantitative analysis in assessment and design (Bernhardt et al., 2005; Palmer et al

Bledsoe, Brian

186

Fluvial network analysis on Titan: Evidence for subsurface structures and west-to-east wind flow, southwestern Xanadu  

E-print Network

Fluvial network analysis on Titan: Evidence for subsurface structures and west-to-east wind flow; published 25 November 2009. [1] Data of Titan's surface from the Cassini-Huygens mission show inferred, indicating that a variety of factors control fluvial drainage on Titan. Drainage network patterns

Perfect, Ed

187

Late Cenozoic sedimentary sequences in Acre state, southwestern Amazonia: Fluvial or tidal? Deductions from the IGCP 449 fieldtrip  

Microsoft Academic Search

The IGCP 449 fieldtrip in June 2003 drew attention to the Late Cenozoic fluvial sequences of western Amazonia. In Acre state in western Brazil, underlain by relatively mobile crust, rivers have incised up to 70minto the stacked latest Miocene (?)\\/Early Pliocene (?) sediments of the Solimões Group, creating staircases of fluvial terraces and indicating regional uplift on this time scale.

Rob Westaway

2006-01-01

188

Dispersion of channel-sediment contaminants in distributary fluvial systems: Application to fluvial tephra and radionuclide redistribution following a potential volcanic eruption at Yucca Mountain  

Microsoft Academic Search

Predicting the fluvial transport and mixing of channel-sediment contaminants is necessary for assessing and mitigating heavy-metal and nuclear-waste contamination in rivers. The dilution–mixing model is widely used for this purpose in tributary channel systems that transport contaminants as bed-material load without significant overbank sedimentation. Here a more general, three-dimensional (3D) contaminant transport numerical model is developed and tested based on

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

2008-01-01

189

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

NASA Astrophysics Data System (ADS)

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

Wang, H.; Jia, X.

2015-02-01

190

Significance of Quaternary and Experimental Fluvial Systems to Interpretation of the Stratigraphic Record  

NASA Astrophysics Data System (ADS)

Studies of Quaternary and experimental fluvial systems provide significant insight for interpretation of fluvial deposits in the stratigraphic record, ranging from measurement of processes and relevant scales of key architectural elements, to process-based understanding of fluvial systems in sequence stratigraphic models. One key advantage for Quaternary and experimental systems is they commonly provide the ability to test, in a classical verification or falsification sense, interpretations, models and their alternatives that were developed from the stratigraphic record alone. First, scaling relationships developed from Quaternary fluvial deposits can be utilized to constrain interpretations of ancient strata, as well as predict the scale of channel fills, channel-belt sand bodies, and incised valleys. Scaling relationships are defined by power laws, with absolute dimensions that scale to drainage area, water flux, and sediment flux. Width-to-thickness ratios for channel fills range from 10-20:1, whereas channel-belt sand bodies upstream from backwater effects commonly range from 70-300:1, and 20-40:1within the backwater zone, where channel migration is limited. Quaternary incised valleys range from 25-150 m in thickness, and ~5-100 km in width, with width-to-thickness ratios of ~500-800. Scales of Quaternary channel fills and channel-belt sand bodies overlap are consistent with compilations from the ancient record. However, even the smallest Quaternary incised valleys reside in the uppermost part of the domain of published ancient valleys, with ancient examples overlapping significantly with modern channel fills and channel belts. We suggest that many ancient examples have been overinterpreted because of a lack of objective criteria for differentiating channel fills, channel belts, and incised valleys. Second, incised valleys have long played a key role in sequence-stratigraphic interpretations. For incised valleys in the stratigraphic record, either in outcrop or subsurface data, the sequence boundary is most commonly defined by the base of fluvial incision, which demarcates a significant basinward shift of facies, and is assumed to be an unconformity that everywhere separates younger strata above from older strata below. This classical interpretation is derived from a model for fluvial incision and sediment bypass during relative sea-level fall: fluvial deposits that rest on the sequence boundary are commonly assumed to represent filling of an empty container during late lowstand or early transgression. However, the model of fluvial incision and sediment bypass during relative sea-level fall has never been verified and does not stand up to scrutiny in Quaternary systems or experiments. Moreover, sediment bypass and deposition within incised valleys are not mutually exclusive: a large proportion of fluvial sediment is in transit over the duration of a base-level cycle, even though erosion and channel-belt deposition continuously redefines the valley shape, and at any one point the basal valley-fill surface is the same age as fluvial deposits that rest on top of it. Last, extension of valleys across a newly emergent shelf is accompanied by linked channel-belt deposition and delta progradation, such that the base of fluvial incision does not qualify as an unconformity or meet traditional criteria for a sequence boundary.

Blum, M. D.; Martin, J. M.

2012-12-01

191

Distribution of diagenetic alterations within depositional facies and sequence stratigraphic framework of fluvial sandstones: Evidence from the Petrohan Terrigenous Group, Lower Triassic, NW Bulgaria  

Microsoft Academic Search

Sequence stratigraphy of fluvial deposits is a controversial topic because changes in relative sea level will eventually have indirect impact on the spatial and temporal distribution of depositional facies. Changes in the relative sea level may influence the accommodation space in fluvial plains, and hence have impact on types of fluvial system, frequency of avulsion, and style of vertical and

Mohamed Ali Kalefa El-Ghali; Sadoon Morad; Howri Mansurbeg; Miguel Angel Caja; George Ajdanlijsky; Neil Ogle; Ihsan Al-Aasm; Manhal Sirat

2009-01-01

192

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

NASA Technical Reports Server (NTRS)

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

Wilkinson, Justin; Kreslavsky, Misha

2009-01-01

193

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

194

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

E-print Network

of cubic meters of sediment in North American stream systems prior to European contact. Individual bison and fluvial systems through their near-extirpation of native populations of animal species that strongly an increasing appreciation has de- veloped for the role of native and introduced animals as geomorphic agents

195

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

196

COMPREHENSIVE ASSESSMENT OF CONTAMINATED FLUVIAL SEDIMENTS EROSION RISK AND ECOLOGICAL HAZARD  

E-print Network

COMPREHENSIVE ASSESSMENT OF CONTAMINATED FLUVIAL SEDIMENTS ­ EROSION RISK AND ECOLOGICAL HAZARD assessment of contaminated aquatic sediments has to consider both sediment hydraulics and ecology. Since layers of contaminated sediments are often buried under less polluted deposits, the risk of erosion

Cirpka, Olaf Arie

197

Quaternary fluvial-volcanic stratigraphy and geochronology of the Capitoline Hill in Rome  

Microsoft Academic Search

In and around Rome, coastal and fluvial sediments influenced by Quaternary sea-level changes interfinger with accurately datable, highly potassic pyroclastic volcanic units. We describe the complex internal geology of the Capitoline Hill, for centuries a place of leading importance in ancient Rome and more recently a focus of archaeological research. Outcrops and many new drill cores reveal at least four

Walter Alvarez; Albert J. Ammerman; Paul R. Renne; Daniel B. Karner; Nicola Terrenato; Alessandro Montanari

1996-01-01

198

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

Microsoft Academic Search

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

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

2008-01-01

199

Fluvial bedrock incision in the active mountain belt of Taiwan fromin situ-produced cosmogenic nuclides  

Microsoft Academic Search

The concentration of cosmogenic nuclides in rocks exposed at the Earth's surface is propor- tional to the total duration of their exposure. This is the basis for bedrock surface exposure dating and has been used to constrain valley lowering rates in the Taroko gorge, eastern Central Range, Taiwan. Taroko gorge contains a uniquely complete geomorphic record of fluvial valley lowering:

M. Schaller; N. Hovius; S. D. Willett; S. Ivy-Ochs; H.-A. Synal; M.-C. Chen

2005-01-01

200

Generalized hydraulic geometry: Insights based on fluvial instability analysis and a physical model  

E-print Network

Generalized hydraulic geometry: Insights based on fluvial instability analysis and a physical model asymmetry over reaches of increasing scale. To test this hypothesis, we employ both a direct analysis multiscaling model. INDEX TERMS: 1824 Hydrology: Geomorphology (1625); 1860 Hydrology: Runoff and streamflow

Foufoula-Georgiou, Efi

201

Friday, March 17, 2006 MARS: FLUVIAL GEOMORPHOLOGY: RIVERS, OUTFLOWS, AND GULLIES  

E-print Network

Friday, March 17, 2006 MARS: FLUVIAL GEOMORPHOLOGY: RIVERS, OUTFLOWS, AND GULLIES 8:30 a.m. Crystal.m. Luo W. * Howard A. D. Quantitative Morphometric Analysis of Simulated Martian Landforms at Watershed channel. The sedimentological analysis of this deposit allowed to infer the hydrological evolution

Rathbun, Julie A.

202

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

203

Fluvial history of the Rio Ilave valley, Peru, and its relationship to climate and human history  

Microsoft Academic Search

Fluvial strata and landforms in the Rio Ilave valley (Peru) document a history of Holocene aggradation and downcutting that is correlative with regional climatic events and provides an environmental context for human occupation of the river valley. Periods of aggradation correspond to periods of high (or rising) level in Lake Titicaca and elsewhere on the Altiplano, and increased sediment accumulation

Catherine A. Rigsby; Paul A. Baker; Mark S. Aldenderfer

2003-01-01

204

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

Lindley Hanson

205

Scoyenia Escape Burrows in Fluvial Pebbly Sand: Upper Triassic Sugarloaf Arkose, Deerfield Rift Basin, Massachusetts, USA  

Microsoft Academic Search

Late Triassic larvae of an insect, probably a beetle, moved diagonally upwards though fluvial pebbly sand along a thin mud layer, constructing Scoyenia burrows in the Sugarloaf Arkose, Deerfield rift basin, Massachusetts. They may have been escaping a temporary rise of the water table in the monsoonal dry season.

John F. Hubert; James A. Dutcher

2010-01-01

206

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

Microsoft Academic Search

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

Michael C. Pante; Robert J. Blumenschine

2010-01-01

207

Detecting changes in seasonal precipitation extremes using regional climate model projections: Implications for managing fluvial flood  

E-print Network

further demonstrates that existing precautionary allowances for climate change used for flood managementClick Here for Full Article Detecting changes in seasonal precipitation extremes using regional climate model projections: Implications for managing fluvial flood risk H. J. Fowler1 and R. L. Wilby2

Fowler, Hayley

208

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

Microsoft Academic Search

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.

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

2005-01-01

209

Fluvial Transport of Suspended Solids P Y Julien, Colorado State University, Fort Collins, CO, USA  

E-print Network

sedimen- tation problems resulting in aggradation, river naviga- tion problems, and changes in riverFluvial Transport of Suspended Solids P Y Julien, Colorado State University, Fort Collins, CO, USA undermine the stability of bridges and river protection structures. Equilibrium Transport of Sediment

Julien, Pierre Y.

210

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

211

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

PubMed

The search for once-habitable locations on Mars is increasingly focused on environments dominated by fluvial and lacustrine processes, such as those investigated by the Mars Science Laboratory Curiosity rover. The availability of liquid water coupled with the potential longevity of such systems renders these localities prime targets for the future exploration of Martian biosignatures. Fluvial-lacustrine environments associated with basaltic volcanism are highly relevant to Mars, but their terrestrial counterparts have been largely overlooked as a field analogue. Such environments are common in Iceland, where basaltic volcanism interacts with glacial ice and surface snow to produce large volumes of meltwater within an otherwise cold and dry environment. This meltwater can be stored to create subglacial, englacial, and proglacial lakes, or be released as catastrophic floods and proglacial fluvial systems. Sedimentary deposits produced by the resulting fluvial-lacustrine activity are extensive, with lithologies dominated by basaltic minerals, low-temperature alteration assemblages (e.g., smectite clays, calcite), and amorphous, poorly crystalline phases (basaltic glass, palagonite, nanophase iron oxides). This paper reviews examples of these environments, including their sedimentary deposits and microbiology, within the context of utilising these localities for future Mars analogue studies and instrument testing. PMID:25692905

Cousins, Claire

2015-01-01

212

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

E-print Network

for river restoration is develop- ing in the Puget Sound region driven by concerns over salmon recovery3. Fluvial Processes in Puget Sound Rivers and the Pacific Northwest John M. Buffington*, Richard D and response potential in the Puget Sound region. We also review the influence of different channel types

213

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

214

LANDSCAPE PERCEPTION IN FLUVIAL ECOLOGICAL RESTORATION PROJECTS: CONTRIBUTIONS AND PERSPECTIVES FOR THE  

E-print Network

1 LANDSCAPE PERCEPTION IN FLUVIAL ECOLOGICAL RESTORATION PROJECTS: CONTRIBUTIONS AND PERSPECTIVES FOR THE IMPLEMENTATION OF THE LANDSCAPE EUROPEAN CONVENTION Cottet Marylise*, Rivière-Honegger Anne, Piégay Hervé.cottet@univ-lyon3.fr Introduction The European Landscape Convention instituted, at the beginning of the 2000s, a new

Paris-Sud XI, Université de

215

Fluvial reservoir characterization and identification: A case study from Laohekou Oilfield  

NASA Astrophysics Data System (ADS)

Finding channel sandbodies is an important task in oil and gas exploration due to the importance of fluvial reservoirs. It is difficult to describe fluvial reservoirs in detail owing to their frequent changes and serious intersections, as well as limitations of S/N ratio and seismic data resolution. Based on the Laohekou 3D data in Shengli Oilfield, we analyze the general characteristics of fluvial reservoirs in this area, from which we find that they are characterized by strong amplitudes on seismic profiles, high continuity on time slices, and low frequency in the frequency domain. In addition, a cluster of strong string-beadlike reflections was found after color processing and detailed interpretation. To understand this observation, we conduct forward modeling to explain the mechanism. This provides a new way to identify ancient channels in similar areas. By using the multi-attribute fusion and RGB display techniques, channel incision is more obvious and the characteristics of the channel structures are manifested much better. Finally, we introduce and apply multi-wavelet detection technology to identify weaker fluvial reservoir signals.

Zhang, Jun-Hua; Liu, Zhen; Zhu, Bo-Hua; Feng, De-Yong; Zhang, Ming-Zhen; Zhang, Xue-Fang

2011-09-01

216

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

217

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

E-print Network

produce the water discharge rates necessary for fluvial sediment transport unless longterm (kyr) storageClick Here for Full Article Numerical modeling of Martian gully sediment transport: Testing of the interior channel region (above the depositional apron) are 20°. We test the hypothesis that sediment

Nimmo, Francis

218

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

219

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

220

Morphologic and Morphometric Analyses of Fluvial Systems in the Southern Highlands of Mars  

NASA Technical Reports Server (NTRS)

Morphologic and Morphometric Analyses of Fluvial Systems in the Southern Highlands of Mars [#1844] Geologic and geomorphic mapping, image analysis, and hydrologic modeling are being used to characterize the morphology and morphometry of circum-Hellas and circum-Isidis valley networks in order to determine the process(es) of network formation.

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

2004-01-01

221

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

222

Wildfire thermochronology and the fate and transport of apatite in hillslope and fluvial environments  

E-print Network

Wildfire thermochronology and the fate and transport of apatite in hillslope and fluvial January 2007; revised 25 May 2007; accepted 11 July 2007; published 12 October 2007. [1] Wildfire heating of fission track annealing and He diffusion in apatite lead to a kinetic crossover whereby wildfire heating

Roering, Joshua J.

223

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

USGS Publications Warehouse

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

Gray, Harrison J.; Mahan, Shannon A.

2015-01-01

224

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

E-print Network

. HAMPTON* and BRIAN K. HORTON *Department of Geological Sciences, Michigan State University, East Lansing. Fluvial sandstone and mudstone units were deposited over an extensive region (>10 000 km2 gypsum, gypsiferous mudstone and sandstone. (ii) Floodplain deposits occur throughout the succession

Horton, Brian K.

225

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

226

Automated grain size measurements from airborne remote sensing for long profile measurements of fluvial grain sizes  

Microsoft Academic Search

Recent research has demonstrated that image processing can be applied to derive surficial median grain size data automatically from high-resolution airborne digital imagery in fluvial environments. However, at the present time, automated grain size measurement is limited to the dry exposed bed areas of the channel. This paper shows that the application area of automated grain size mapping can be

Patrice E. Carbonneau; Normand Bergeron

2005-01-01

227

Fluvial fan deltas: Linking channel processes with large-scale morphodynamics  

E-print Network

Fluvial fan deltas: Linking channel processes with large-scale morphodynamics Tao Sun,1 Chris Paola September 2001; accepted 16 January 2002; published 23 August 2002. [1] Alluvial fan deltas are built is combined with a condition for channel avulsion to describe evolution of the fan surface. The model combines

Paola, Chris

228

ALLUVIAL FANS FORMED BY CHANNELIZED FLUVIAL AND SHEET FLOW. I: THEORY  

E-print Network

ALLUVIAL FANS FORMED BY CHANNELIZED FLUVIAL AND SHEET FLOW. I: THEORY By Gary Parker/ Member, ASCE, Chris Paola,:1 Kelin X. Whipple/ and David Mohrig4 ABSTRACT: Alluvial fans and fan-deltas are of three many avulsions) bed slope and elevation in an axially symmetric fan. An example of a fan formed

229

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

230

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

SciTech Connect

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

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

1993-07-01

231

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

232

Fluvial sediment of the Mississippi River at St. Louis, Missouri  

USGS Publications Warehouse

An investigation of the fluvial sediment of the Mississippi River at St. Louis, Mo., was begun in 1948. Most data have been obtained only to determine the daily suspended-sediment discharge and the particle-size distribution of suspended sediment and bed material, but a few data have been obtained to study the flow resistance, the vertical distribution of sediment and velocity, and the bed-material discharge. The flow of the Mississippi River at St. Louis is made up of the flows from the Missouri River, which had an average flow of 79,860 cubic feet per second for 1897-1958 at Hermann, Mo., and from the upper Mississippi River, which had an average flow of 91,890 cubic feet per second for 1928-58 at Alton, Il. The Missouri River is partly controlled by reservoirs that had a total capacity of 90,300,000 acre-feet in 1956, and the upper Mississippi River is partly controlled by lakes and reservoirs that had a total capacity of 4,890,000 acre-feet in 1956. The flows of the Missouri and upper Mississippi Rivers have not become mixed at St. Louis; so the river has a lateral gradient of suspended-sediment concentration. The concentration near the west bank has been as much as 2,400 parts per million greater than the concentration near the east bank. Suspended-sediment discharges from April 1948 to September 1958 ranged from 4,250 to 7,010,000 tons per day and averaged 496,000 tons per day. Mean concentrations for water years decreased steadily from 1,690 parts per million in 1949 to 403 parts per million in 1956, but they increased to 756 parts per million in 1958. Effects of new reservoirs in the Missouri River basin on the concentration have been obscured by the close relation of concentration to streamflow. Measured suspended-sediment discharge through September 1958 averaged 47 percent clay, 38 percent silt, and 15 percent sand. Variations of particle size were due mainly to differences in the source areas of the sediment. Most of the bed material in the main flow was between 0.125 and 1.000 millimeter in diameter. The average of median diameters was related to the discharge for periods of 1 year and longer. Geometric quartile deviations of the bed material ranged from 1.1 to 2.5 and averaged 1.5. The mean elevation of the bed had a range of almost 10 feet and was related to the median diameter of bed material by the regression equation hb=363.0 - 7.8 d50 for which the standard error of estimate was 0.91 foot. The resistance to flow as measured by Manning's n ranged from 0.024 to 0.041 and was related to the discharge and mean velocity but not to the shear velocity. Normal dune height is 2-8 feet, and average dune length is about 250 feet. When the resistance to flow was low, much of the bed was fairly fiat; a few dunes were present, but they were much longer than the average. For a given discharge during individual rises in stage, the gage height was lower for increasing discharge than for decreasing discharge even though the bed elevation was higher. The changes in gage height were not caused by changes in energy gradient due to changing discharge, by channel storage between the gage and the measuring section, nor by return of overbank flow; but they were probably caused by a combination of changes in roughness due to changing bed configuration and of changes in turbulence constant due to changing sediment concentration. Turbulence constants (Von Karman's k) computed from velocity measurements at 5-10 points in the vertical and from routine velocity measurements at 2 points in the vertical averaged 0.35 and 0.33, respectively. The exponent z1 of the vertical distribution of concentration for different size ranges varied with about the 0.77 power of the fall velocity. Except for the difference between the theoretical variation and the actual variation of z1 with changing fall velocity, the theoretical equation for the vertical distribution of sediment concentration seems to apply reasonably well for the Miss

Jordan, Paul Robert

1965-01-01

233

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

234

ANÁLISE DE INVESTIMENTOS EM GERAÇÃO HIDRÁULICA UTILIZANDO A TEORIA DE OPÇÕES REAIS  

Microsoft Academic Search

1. RESUMO Este trabalho apresenta uma metodologia de análise de investimentos em geração de energia elétrica utilizando Teoria de Opções Reais. Particularmente, é avaliada a oportunidade de investimento em geração hidráulica a ser comercializada no leilão de energia nova utilizando-se da alternativa de financiamento do Programa de Financiamento de Geração de Energia Elétrica (Energia Nova) do BNDES. Como os empreendimentos

J. C. CAMINHA NORONHA; J. W. MARANGON LIMA; T. G. LEITE FERREIRA

235

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

236

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

USGS Publications Warehouse

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

Bown, T.M.

1982-01-01

237

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

USGS Publications Warehouse

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

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

1984-01-01

238

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

239

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

Microsoft Academic Search

The Frio fluvial\\/deltaic sandstone along the Vicksburg fault zone play of south Texas has produced nearly 1 billion bbl of oil from fluvial\\/deltaic sandstones since field development began in the 1940s. More than half of the reservoirs in this depositionally complex play have been abandoned, even though large volumes of oil remain. Current efforts integrating geological and engineering reservoir characterization

L. E. McRae; M. H. Holtz

1994-01-01

240

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

SciTech Connect

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

Bou-Mikael, Sami

2002-02-05

241

Holocene beaver damming, fluvial geomorphology, and climate in Yellowstone National Park, Wyoming  

Microsoft Academic Search

We use beaver-pond deposits and geomorphic characteristics of small streams to assess long-term effects of beavers and climate change on Holocene fluvial activity in northern Yellowstone National Park. Although beaver damming has been considered a viable mechanism for major aggradation of mountain stream valleys, this has not been previously tested with stratigraphic and geochronologic data. Thirty-nine radiocarbon ages on beaver-pond

Lyman Persico; Grant Meyer

2009-01-01

242

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

243

Geomorphic study of fluvial landforms on the northern Valles Marineris plateau, Mars  

NASA Astrophysics Data System (ADS)

Fluvial landforms are observed on the plateau near Echus Chasma and other locations on the Valles Marineris plateau using high resolution (10 to 50 m/pixel) Mars Express images and topography. Branching valleys have a 20- to 100-m deep V-shape profile typical of fluvial processes. Their incision occurred in a thin (<150 m) and weak, dark unit that overlies the plateau basement. The valleys are distributed close to watershed boundaries as expected for overland flows, and different from pure glacial or hydrothermal processes. The 2D geometry of valley networks show drainage densities reaching 1.3 km-1 that indicate a strong 2D extension stage that usually requires a minimum of thousands of years, as established from terrestrial examples. However, the 3D valley geometry shows a limited incision, and a lack of concavity, suggesting a limited development in time (millions of years of evolution are unlikely). Many outlets connect to the heads of canyons of Echus Chasma that might involve sapping processes. These canyons might have formed coevally with shallow valleys: their difference in geometry is a consequence of the difference in lithology which induced a difference in the erosion capacity, and an enhanced infiltration conducing to sapping. Valleys are submitted to modification by aeolian processes, sometimes leading to the formation of inverted channels as observed more broadly through the region. These landforms formed late in the Early Mars history and might be considered as examples of episodic fluvial events due to short-term climate changes and/or regional fluvial activity after the Noachian.

Mangold, N.; Ansan, V.; Masson, Ph.; Quantin, C.; Neukum, G.

2008-08-01

244

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

Microsoft Academic Search

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

Takaharu Natsumeda

2007-01-01

245

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

246

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

247

Fluvial obstacle marks as complex geomorphic systems: a comparison between physically modelled and natural forms  

NASA Astrophysics Data System (ADS)

Fluvial obstacle marks are bedforms that develop if flow is separated by an immobile obstacle at the stream bed. Due to local acceleration and deceleration of the flow, areas of potential erosion and deposition arise in the obstacle surrounding. This results in forms that commonly consist of a scour hole reaching from the upstream part to the sides of an obstacle and an adjacent depositional ridge. Natural fluvial obstacle marks develop around pebbles, boulders, woody debris and plants. Individual forms of obstacle marks result from specific current patterns in the obstacle surrounding, which in turn are dependent on a variety of independent parameters like obstacle shape, -inclination, -alignment, -geometry, -porosity, -surface roughness and -flexibility as well as on sediment grading, bed-resistance, flow velocity, flow depth and steadiness of flow. Reciprocal interactions of these parameters make natural obstacle marks noteworthy examples of complex geomorphic systems. In contrast, experimentally simulated obstacle marks in laboratory flumes can be regarded as complexity-reduced geomorphic systems and are characterised by diverging morphological features compared to natural obstacle marks. In spite of these emergent divergences flume experiments are still inevitable to identify principle formative processes. Also experimental simulations are necessary to develop physically-based explanatory approaches that can predict significant morphometric features (like maximum depth of scour, eroded/deposited material) of fluvial obstacle marks. Within the scope of this work examples of natural fluvial obstacle marks are compared with obstacle marks simulated experimentally in a laboratory flume. In spite of morphological differences it can be deduced that a horseshoe-vortex system is the main agent that drives formative processes in the obstacle surrounding. The input of kinetic energy into this vortex system can be well described by determining the obstacle Reynolds number.

Euler, T.

2009-04-01

248

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

249

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

USGS Publications Warehouse

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

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

2010-01-01

250

Complex fluvial response to Lateglacial and Holocene allogenic forcing in the Lower Rhine Valley (Germany)  

Microsoft Academic Search

The Rhine catchment experienced strong changes in upstream allogenic forcing during the last 20,000 years. Climatic changes of the glacial–interglacial transition and steadily growing human impact during the second half of the Holocene forced the Rhine to adapt, resulting in changes in the fluvial morphology. The lower Rhine left two late Weichselian terraces and many Holocene palaeo-meanders in the Lower

G. Erkens; T. Hoffmann; R. Gerlach; J. E. M. Klostermann

2011-01-01

251

Aspects of cratonal sedimentation: facies distribution of fluvial and shallow marine sequences in NW Sudan / SW Egypt since Silurian time  

NASA Astrophysics Data System (ADS)

The predominantly fluvial sediments, which characterize Silurian to Upper Cretaceous strata of NW-Sudan and SW-Egypt, were repeatedly interrupted by marine transgressions, which rapidly progressed toward the south since Ordovician time. Most of the thin, shallow marine deposits of different ages can be traced for more than 1000 km within the studied area of the southern Dakhla Basin, Misaha Trough and the Abyad Basin. From Silurian time onward, sheet-like sandstone units of large lateral extent within the shallow basins have been built up by vertical and lateral stacking of fluvial sandstone bodies, as well as bythe amalgamation of fluvial sequences from mainly braided to low-sinuosity river sand sandy nearshore deposits. Since sedimentological processes are closely connected with the structural history of the region and with paleogeographic and paleoclimatic conditions, a classification of distinct sequence developments can be given, due to the respective structural situation: a) Fluvial/shallow marine and predominantly fluvial cratonic sheet sandstones are attributed to a mild crustal warping structural type, partly affected by reactivated fault systems (Silurian to Lower Carboniferous, Lower Cretaceous and Upper Cretaceous strata). b) Alluvial clastic wedges, attributed to vertical block movement, have been formed by fluvial sediments in intracratonal grabens and display various facies within the alluvial paleoenvironments (predominantly Upper Carboniferous to Lower Jurassic and Upper Jurassic strata). Increasing soil-forming processes have been affecting the depositional style of the alluvial deposits from Carboniferous time onward, and became especially dominant at the Upper Cretaceous.

Wycisk, P.

252

Agua Caliente Wind/Solar Project at Whitewater Ranch  

SciTech Connect

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

Hooks, Todd; Stewart, Royce

2014-12-16

253

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

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

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

2015-01-01

254

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

255

Exploration and development of the fluvial deposits in the Potrerillos Formation, Cuyana Basin, Mendoza, Argentina  

SciTech Connect

In the Barrancas area are located the oil fields related to structures developed in the Oriental axis of the Cuyana Basin. The anticlinal axis of the Barraticas oil field has a NNW-SSE strike and dips toward North. The Oriental flank is abruptly bounded by faulting whilst the Occidental one is gently dipping. The Barrancas oil field was developed between the 1940s and 1960s, having both Early Jurassic conglomerates of the Barrancas Formation and Triassic fluvial braided deposits from Las Cabras Formation as the main targets. The review of new plays within the Triassic fluvial cycles belonging to the Potrerillos Formation was encouraged by the success obtained in the recovery of important volumes of oil from the overlying Formations. The application of a sequence stratigraphy approach to the fluvial settings combined with petrophysics data from outcrop studies and a 3D seismic interpretation allowed a new play concept to be conceived. This new play concept will have application in zones far away from the study area, where Potrerillos Formation has exploration interest. A team integrate by geologists, geophysicists, and engineers has produced new opportunities on mature oil fields with up to 300 drilled wells.

Fernandez, C.; Agraz, P. [YPF, S.A., Av. San Martin, Mendoza (Argentina)

1996-08-01

256

Changes in the ciliate assemblage along a fluvial system related to physical, chemical and geomorphological characteristics.  

PubMed

Samples were collected monthly from the water-sediment interface at six stations along the Mincio River (northern Italy) during a 1-year study of the ciliated protozoan communities. Four stations were located upstream of the Mantua lakes in the hyporhithron fluvial zone and two stations were located in the potamon fluvial zone between the Mantua lakes and the confluence with the Po River. A total of 133 species of active trophic ciliates belonging to 76 genera were found. Community structures revealed in this data were analysed using some statistical methods (similarity index, and categorical principal component analysis (CATPCA)) and this allowed the determination of differences between stations and between ciliate communities characteristic of stations. Species typical of the ecotypes located in both rhithron and potamon fluvial zones were defined. The saprobic index and valency analysis methods were used to quantify organic input and to follow changes in saprobicity along the river. A change in the ciliate communities was observed between stations located upstream and stations located downstream of the town of Mantua. The former were composed mainly of beta-mesosaprobic species, typical of the hill zone of running waters, while in the latter increased numbers of alpha-mesosaprobic species are associated with the higher anthropogenic pressures. Our results reiterate the high sensitivity shown by ciliated protozoa as indicators of organic load in watercourses. PMID:17222541

Madoni, Paolo; Braghiroli, Sonia

2007-06-01

257

The influence of crustal strength fields on the patterns and rates of fluvial incision  

NASA Astrophysics Data System (ADS)

Gradients in the bedrock strength field are increasingly recognized as integral to the rates and patterns of landscape evolution. To explore this influence, we incorporate data from fault strength profiles into a landscape evolution model, under the assumption that erodibility of rock is proportional to the inverse square root of cohesion for bedrock rivers incised by bedload abrasion. Our model calculations illustrate how patterns in the crustal strength field can play a dominant role in local fluvial erosion rates and consequently the development of fluvial network patterns. Fluvial incision within weak zones can be orders of magnitude faster than that for resistant bedrock. The large difference in erosion rate leads to the formation of a straight, high-order channel with short, orthogonal tributaries of low order. In comparison, channels incising into homogeneous strength fields produce dendritic drainage patterns with no directional dependence associated with erodibility gradients. Channels that cross the strength gradient experience local variations in knickpoint migration rate and the development of stationary knickpoints. Structurally confined channels can shift laterally if they incise into weak zones with a shallow dip angle, and this effect is strongly dependent on the magnitude of the strength difference, the dip angle, and the symmetry and thickness of the weak zone. The influence of the strength field on drainage network patterns becomes less apparent for erodibility gradients that approach homogeneity. There are multiple natural examples with drainage network patterns similar to those seen in our numerical experiments.

Roy, S. G.; Koons, P. O.; Upton, P.; Tucker, G. E.

2015-02-01

258

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

259

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

NASA Astrophysics Data System (ADS)

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.

1984-04-01

260

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

NASA Astrophysics Data System (ADS)

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

Butler, David R.

2006-09-01

261

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

262

Relationships of bankfull channel width and discharge parameters for modern fluvial systems in the Japanese Islands  

NASA Astrophysics Data System (ADS)

The relationships between the bankfull channel width and the mean, bankfull, and maximum discharges of Japanese rivers were examined using the hydrological and geomorphological data from 368 sites. The relationships between the bankfull channel width and the mean and bankfull discharges do not show any distinct regional variations. In contrast, the relationship between the maximum discharge and the bankfull channel width shows regional variations, and the lower and higher maximum discharges relative to bankfull channel widths are documented in the fluvial systems in Hokkaido and Southwest Japan, respectively. These variations are interpreted to reflect regional variations in precipitation intensity during the rainy season, and the magnitude and frequency of typhoon-related flooding. The relationship between the bankfull channel width and the bankfull discharge can be described by an empirical equation similar to that described from modern fluvial systems on the European and American continents. Consequently, this empirical equation may have wider applicability for the estimation of hydrological features of modern and ancient fluvial systems, not only in active margin settings influenced by mid-latitude temperate climates, but also in passive continental margins and continental interior basins.

Shibata, Kenichiro; Ito, Makoto

2014-06-01

263

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

SciTech Connect

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

Ashley, G.M. (Rutgers Univ., New Brunswick, NJ (United States). Dept. of Geological Sciences); Hamilton, T.D. (U.S. Geological Survey, Anchorage, AK (United States))

1993-09-01

264

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

USGS Publications Warehouse

Surface-subsurface flow interactions are critical to a wide range of geochemical and ecological processes and to the fate of contaminants in freshwater environments. Fractal scaling relationships have been found in distributions of both land surface topography and solute efflux from watersheds, but the linkage between those observations has not been realized. We show that the fractal nature of the land surface in fluvial and glacial systems produces fractal distributions of recharge, discharge, and associated subsurface flow patterns. Interfacial flux tends to be dominated by small-scale features while the flux through deeper subsurface flow paths tends to be controlled by larger-scale features. This scaling behavior holds at all scales, from small fluvial bedforms (tens of centimeters) to the continental landscape (hundreds of kilometers). The fractal nature of surface-subsurface water fluxes yields a single scale-independent distribution of subsurface water residence times for both near-surface fluvial systems and deeper hydrogeological flows. Copyright 2007 by the American Geophysical Union.

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

2007-01-01

265

Fluvial Response to Hydrologic Variability in the Pelly River, Yukon Territory, Canada  

NASA Astrophysics Data System (ADS)

The potential impacts of climate changes on fluvial systems in northern latitudes are difficult to predict due to the complex interactions expected among climate change, hydrology, and fluvial processes. Thus, cataloging the response of fluvial processes to modern hydrologic variability is needed to assess current and future impacts of hydrologic change on northern watersheds. In this study, dendrochronology, gauge data, and pedology are being used to study floodplain reworking in a section of the Pelly River basin, Yukon Territory, Canada. The hydrology of the Pelly River system is snow-melt dominated, with little to no glacial contribution. The Pelly River has been gauged at 4 sites for periods of 9 years to 55 years since 1951; of these sites, the gages at Pelly Crossing (09BC001) and below Vangorda Creek (09BC004) are still active. The gauges measure discharge for drainage areas ranging from 5,020 km2 below Fortin Creek (09BA002), to 49,000 km2 on the Pelly River at Pelly Crossing. Mean bed elevation changes calculated from gauge data vary from less than 0.2 m below Fortin Creek to 2.1m below Vangorda Creek (drainage area 22,100km2). These mean bed elevation changes show a variable relation to peak discharge. Within the section of the Pelly River between Ross River and Faro, dendrochronology of studied bars indicates that active gravel bar surfaces are less than 30 years old. Adjacent surfaces which slope continuously to the current active flood plain, however, support spruce forests at least 100 years old. Near Ross River, an ash interpreted to be the White River ash (deposited approximately 1200 years ago) crops out at the surface of a terrace several meters above the current active bar surface and approximately half a meter below the surface of a lower terrace. Soil development and surface morphology support the hypothesis that the lower terrace surface is younger than the higher terrace and was buried by fluvial aggradation after ash deposition. Reconnaissance found limited outcrops of ash, suggesting most of the valley bottom in the studied section has been reworked in the last 1200 years. Soil development on the flood plain surface supports the hypothesis that this surface is distinctly younger than the two terraces. Preliminary results suggest current fluvial processes in the Pelly River flood plain are characterized by fluctuating bed levels coupled with moderate lateral reworking and avulsion; rates of these processes appear to be related to discharge patterns in a complex manner.

McKenney, R.; Peterson, K.; Ramage, J. M.; Thorson, B.; Hanna, W.; Kortlever, B.; Apgar, J. D.

2006-12-01

266

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

267

Tributary, distributary and other fluvial patterns: What really represents the norm in the continental rock record?  

NASA Astrophysics Data System (ADS)

This paper evaluates the recent claim made by Weissmann et al. (2010) that deposits of "Distributive Fluvial Systems" (DFS) may form the bulk of the continental fluvial record. Weissmann et al. (2010) define DFS as "a pattern of channel and floodplain deposits that radiate outward from an apex that is located where the river enters the sedimentary basin". As such, DFS are fan-like systems on which multiple channels coexist and distribute water and sediment across the fan. Published criteria for the recognition of DFS (Weissmann et al., 2010) are 1) a radial pattern of channels from the DFS apex; 2) downslope decreases in channel size; 3) down-DFS grain-size decreases; and 4) a lack of lateral channel confinement. However, in Weissmann et al. (2010) and subsequent papers, only the first of these criteria is applied rigorously, thus allowing a variety of types of fluvial system (including avulsive, incised, anabranching, and coastal plain distributary systems) to potentially be classified uncritically as DFS. An ancient succession formed by DFS should preserve mostly small channel bodies, with a limited range of dimensions and no outsized channel bodies. Channel bodies in DFS-dominated successions should also decrease in size in a down-palaeoslope direction and show palaeocurrent relationships indicative of radial dispersal. In order for the term DFS to be applied, these characteristics should also be established within stratigraphic bodies that formed coevally. However, very few examples have yet been published that satisfy these criteria. If the claim that DFS dominate the alluvial stratigraphic record is valid, then few, if any, sedimentary bodies formed by large channels should be preserved. A review of published research demonstrates, however, that the alluvial stratigraphic record contains a broad diversity of fluvial network styles, including abundant representatives of tributary, avulsive, anabranching, and incised, in addition to distributary types. It is also clear that the deposits of large, main stem rivers that are comparable to the big rivers of the modern world are abundantly preserved in the stratigraphic record. An analysis of the planimetric area of modern tributary and distributary fluvial systems is presented, demonstrating that tributary systems are also likely to represent a far larger proportion of the ancient sedimentary record than DFS. The body of evidence presented herein from modern and ancient alluvial systems thus suggests that the hypothesis of Weissmann et al. (2010) should be wholly rejected. DFS do not dominate the continental stratigraphic record.

Fielding, Christopher R.; Ashworth, Philip J.; Best, James L.; Prokocki, Eric W.; Smith, Gregory H. Sambrook

2012-06-01

268

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

NASA Astrophysics Data System (ADS)

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

Fielding, C. R.

2010-12-01

269

Método de Prueba GAED: Tiempo Óptimo para el Reemplazo de CAG en Plantas de Tratamiento de Agua Potable  

Microsoft Academic Search

l carbón activado granular (CAG) no dura para siempre en una planta de tratamiento de agua (PTA), su rendimiento no necesita ser monitoreado periódicamente, y deberá ser reemplazado con CAG fresco, no usado o reactivado. El CAG usado, que se remueve, puede ser reactivado en plantas dedicadas a carbones de agua potable para ser retornado a la planta. Los reactivadores

Por Henry Nowicki; H. George Nowicki; Wayne Schuliger; Barbara Sherman

270

La participación del sector privado en los servicios de agua y saneamiento en San Pedro Sula, Honduras  

Microsoft Academic Search

Este estudio analiza el proceso de reforma de los sistemas de agua y alcantarillado del término municipal de San Pedro Sula iniciado en el año 1998. San Pedro Sula ilustra un caso en que la concesión de los servicios atrajo la atención de los inversores, el primer caso de participación del sector privado en los servicios de agua y saneamiento

Javier Díaz

2003-01-01

271

Herramienta de evaluación para implementar buenas prácticas en el área de gestión comercial de operadores de agua y saneamiento  

Microsoft Academic Search

El presente documento informa sobre una herramienta desarrollada por la División de Agua y Saneamiento del BID para evaluar las prácticas utilizadas en la gestión de los clientes de las empresas de agua y alcantarillado. Con el fin de facilitar el uso de esta herramienta, todos los aspectos que se refieren a la gestión de clientes se han agrupado en

Jean-Loup Jourdain

2011-01-01

272

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

273

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

274

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

275

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

276

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

277

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

278

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

279

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

280

Coarse sediment dynamics in a proglacial fluvial system (Fagge River, Tyrol)  

NASA Astrophysics Data System (ADS)

Alpine regions are strongly affected by the global climate change. Alpine glaciers have had a negative net balance since the end of the Little Ice Age (LIA). Proglacial areas with freshly exposed subglacial sediments are expanding due to the retreat of glaciers. These sediments (moraines, tills, glaciofluvial deposits, etc.) are unconsolidated, nearly unvegetated and therefore unstable and highly vulnerable to surface changes triggered by geomorphological processes. Particularly during heavy rainfall events, glacial and glaciofluvial deposits are remobilized and transported within the fluvial system. This study is focused on rapidly changing surfaces in the proglacial fluvial system of the Fagge River, which drains the Gepatschferner, one of the biggest glaciers in Austria, and is located in the Kaunertal/Austria. The field site covers an area from the snout of the glacier (2206 m a.s.l.) to the outlet of the Fagge River into the Gepatsch Reservoir at (1750 m a.s.l.). The main goal of this study is to measure surface changes and quantify mass balances of important sediment sources (alluvial plains, bars) in the proglacial area, which are directly connected to the fluvial system. For this purpose, multiple terrestrial laser scans are performed with an Optech ILRIS-36D laser scanner. During the field season in 2011 and 2012, several sediment sources were scanned at least twice. Significant surface changes occurred during the investigation period, mainly caused by an extreme flood event after heavy rain on August 26, 2012. Large amounts of sediment (> 70,000 m3) were remobilized, especially in the upper parts of the proglacial area, and were accumulated further downstream during this event.

Baewert, Henning; Morche, David

2014-08-01

281

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

282

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

283

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

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

284

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

NASA Astrophysics Data System (ADS)

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

Harden, Carol P.

2006-09-01

285

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

286

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

NASA Astrophysics Data System (ADS)

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

Dodov, Boyko; Foufoula-Georgiou, Efi

2005-05-01

287

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

288

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

USGS Publications Warehouse

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

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

2010-01-01

289

DESARROLLO TECNOLÓGICO Y PARTICIPACIÓN COMUNITARIA: FORTALEZAS ANTE LA PREVISTA CRISIS DEL AGUA  

Microsoft Academic Search

El sistema condominial de agua potable y alcantarillado sanitario es una tecnología sanitaria apropiada para la expansión y la renovación de las instalaciones sanitarias urbanas. Se está introduciendo en Lima, Perú luego de haberse desarrollado en Brasil y aplicado en Bolivia, pero con mucho mayor incidencia en la participación comunitaria. La participación tiene en esta ciudad, como antecedentes, el haberse

Carlos Barrios Napurí

2007-01-01

290

ANÁLISIS DE LA PROBLEMÁTICA DE AGUAS RESIDUALES EN LA REGIÓN DE TEXCOCO, ESTADO DE MÉXICO  

Microsoft Academic Search

En la región de Texcoco el uso del agua presenta procesos intensos de sobreexplotación que amenaza su sustentabilidad, debido a que actualmente el acuífero representa el 42% del distrito de riego 38 y que abastece a una población de 204,800 habitantes, se encuentra en una condición clasificada como extremadamente sobreexplotado. La presión demográfica del municipio de Texcoco, y de los

Alma Alicia Gómez Gómez; Díaz Carreón Blanca Cayetana

2011-01-01

291

Economías de escala en agua y saneamiento: examen de la literatura  

Microsoft Academic Search

Este estudio se ocupa de relevar la literatura internacional sobre economías de escala en el sector de agua y saneamiento, reseñarla y extraer hilos conductores. En todo el mundo está en discusión cómo lograr un acceso más equitativo y una prestación más eficiente. Un tema vinculado con la eficiencia es la posibilidad de aprovechar economías de escala al dimensionar la

Gustavo Ferro; Emilio J. Lentini; Augusto C. Mercadier

2010-01-01

292

La participación del sector privado en los servicios de agua y saneamiento en Guayaquil, Ecuador  

Microsoft Academic Search

El Banco está preparando unas guías para la aplicación de las Política de Servicios Públicos Domiciliarios (OP-708) al sector de agua y saneamiento. Esta política establece un marco para compatibilizar los objetivos de aumento de cobertura y calidad con el resto de los objetivos de desarrollo y eficiencia de cada país. Para facilitar el diseño de las operaciones, el Banco

Javier Díaz

2003-01-01

293

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

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

294

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

295

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

USGS Publications Warehouse

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

Colman, Steven M.

1983-01-01

296

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

NASA Astrophysics Data System (ADS)

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

Meybeck, Michel; Vörösmarty, Charles

2005-02-01

297

Arsenic mobility in fluvial environment of the Ganga Plain, northern India  

Microsoft Academic Search

In the northern part of the Indian sub-continent, the Gomati River (a tributary of the Ganga River) was selected to study\\u000a the dynamics of Arsenic (As) mobilization in fluvial environment of the Ganga Plain. It is a 900-km-long, groundwater-fed,\\u000a low-gradient, alluvial river characterized by monsoon-controlled peaked discharge. Thirty-six water samples were collected\\u000a from the river and its tributaries at low

Munendra Singh; Amit Kumar Singh; Swati; Nupur Srivastava; Sandeep Singh; A. K. Chowdhary

2010-01-01

298

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

299

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

E-print Network

Himalayas; Sedim. Geol. 8 77–82. http://resolver.scholarsportal.info/resolve/doi/10.1016/ 0037-0738(72)90042-5. Counts J W and Hasiotis S T 2009 Neoichnological exper- iments documenting burrowing behaviors and traces of the masked chafer beetle (Coleoptera... (Section-I; N26 54?2.49??/E088 28?15.07??) and two river sec- tions along Leesh river (Section-II; N26 55?16.3??/ E088 32?34.8??) and Gheesh river (Section-III; N26 54?19.6??/E088 36?46.5??) in the study area have Keywords. Trace fossils; Cenozoic; fluvial...

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

2013-08-01

300

Landscape analysis of the Huang He headwaters, NE Tibetan Plateau — Patterns of glacial and fluvial erosion  

NASA Astrophysics Data System (ADS)

The large-scale geomorphology of the Huang He (Yellow River) headwaters, centered around the Bayan Har Shan (5267 m asl) in the northeastern part of the Tibetan Plateau, is dominated by an uplifted remnant of a low-relief relict plateau with several mountain ranges. We have performed geomorphological mapping using SRTM topographic data and Landsat 7 ETM+ satellite imagery to evaluate landscape characteristics and patterns, and to investigate the relative importance of different erosional processes in the dissection of this plateau remnant. The distribution of valley morphologies indicates that the eastern and southern margins of the plateau remnant have been extensively dissected by the Huang He and Chang Jiang (Yangtze) rivers and associated tributaries, while the mountain ranges have valley morphologies with U-shaped cross-sections that indicate large impacts from glacial erosion during Quaternary glaciations. An east-west decrease in the abundance of glacial valleys in mountains above 4800 m asl suggests that the diminishing size of the mountain blocks, coupled with increased continentality, resulted in more restricted glaciations to the west. Glacial valleys in mountain blocks on the plateau remnant are wider and deeper than adjacent fluvial valleys. This indicates that, integrated over time, the glacial system has been more effective in eroding the mountains of the relict upland surface than the fluvial system. This erosion relationship is reversed, however, on the plateau margin where dramatic fluvial rejuvenation in valleys that are part of the Huang He and Chang Jiang watersheds has consumed whatever glacial morphology existed. A remarkable correspondence exists between the outline of the relict plateau remnant and the outline that has been proposed for the Huang He Ice Sheet. This coincidence could mean that the Huang He Ice Sheet was larger than originally proposed, but that evidence for this has been consumed by fluvial incision at the plateau margin. Alternatively, this coincidence could indicate that what has been described as an ice sheet border is merely the outline of a relict plateau landscape. In apparent support of the latter, the absence of large-scale glacial geomorphological evidence on the plains of the relict plateau surface is not consistent with the hypothesis of a Huang He Ice Sheet.

Stroeven, A. P.; Hättestrand, C.; Heyman, J.; Harbor, J.; Li, Y. K.; Zhou, L. P.; Caffee, M. W.; Alexanderson, H.; Kleman, J.; Ma, H. Z.; Liu, G. N.

2009-01-01

301

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

302

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

303

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

NASA Astrophysics Data System (ADS)

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

Miyamoto, Hitoshi; Toshimori, Nobuhiko; Kimura, Ryo

2013-04-01

304

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

NASA Astrophysics Data System (ADS)

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

Irwin, R. P.

2011-12-01

305

A factor analysis of elemental associations in the surface microlayer of Lake Michigan and its fluvial inputs  

NASA Astrophysics Data System (ADS)

Elemental concentrations in surface microlayer and subsurface water samples from Lake Michigan and from its major fluvial sources were subjected to separate R mode factor analyses to define the geochemical phases and mechanisms which influence the composition of the surface microlayer. The associations revealed by these analyses indicate that the composition of fluvial microlayers is controlled by localized factors related to the geology of individual drainage basins, while open lake microlayers are influenced by broad scale physiochemical interactions. Depletions of both dissolved and particulate phase constituents in fluvial microlayers are attributed to upward diffusion of ions in sediment pore fluids and resuspension of bottom sediments. Enrichments of these constituents in open lake microlayers are due to organic complexation, biological uptake, and bubble flotation of fine-grained mineral particles.

Mackin, James E.; Owen, Robert M.; Meyers, Philip A.

1980-03-01

306

Magmatic Intrusions and a Hydrothermal Origin for Fluvial Valleys on Mars  

NASA Technical Reports Server (NTRS)

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

1998-01-01

307

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

308

Structural control of fluvial drainage in the western domain of the Cape Fold Belt, South Africa  

NASA Astrophysics Data System (ADS)

The purpose of the study was to examine the extent to which drainage morphology has been influenced by faulting, folding and bedrock lithology in the Cape Fold Belt (CFB) of South Africa. This region was formed during Paleozoic-Mesozoic convergence along the south-western margin of Gondwana. An extensive structural geology database, terrain characteristics and stream network data were analysed using Geographical Information Systems (GIS) to examine the possible linkages between structure and fluvial drainage. Results indicated that the contemporary geomorphology of the area reflects the influence of folding and faulting as well as differential erosion. The following drainage anomalies suggestive of strong structural control were identified: orientation of flow direction of major streams corresponding to structural lineaments, abrupt changes in stream direction influenced by anticline fold axes, faults and joints, and fault-aligned streams. Drainage development in the study area responded noticeably to the underlying structure. The study raises questions with regard to the implications of one major or multiple dominant structural controls on drainage morphology and pattern. The findings have relevance with regard to the understanding fluvial drainage development and landform evolution in tectonically deformed regions.

Manjoro, Munyaradzi

2015-01-01

309

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

310

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

311

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

312

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

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

313

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

SciTech Connect

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

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

1993-09-01

314

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

315

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

NASA Astrophysics Data System (ADS)

Continental depositional systems influenced by salt movement are characterized by rapid lateral and vertical facies changes that are difficult to predict at reservoir scale. The Triassic Skagerrak Formation of the Central North Sea, UK is an excellent example of how the onset of Permian Zechstein salt movement strongly influenced the thickness, stratigraphy and facies distributions of this large fluvial system. However, the Zechstein salts and intercalated evaporites of the Skagerrak Formation also influenced the reservoir quality of the Skagerrak Formation by controlling many diagenetic reactions. Fluvial channel sandstones of the Skagerrak Formation possess anomalously high porosities for their present-day depth of burial and sedimentary depositional setting. The reservoirs with high overpressures often have high porosities, contain less macroquartz cement, and have some component of secondary porosity. Pores pressures within the Skagerrak Formation can exceed 70 MPa at depths of 4000 mbsf where temperatures are above 120° C. A retained primary porosity up to 35% can be found in many of the fluvial channel sandstones. Here we report the results of investigations into the interaction of evaporite dissolution, saline brines and pore fluid pressure in controlling diagenesis in the complex fluvial HPHT reservoirs of the Skagerrak Formation. Our studies on petrographic (thin sections, SEM, EDS), formation water chemistry and pore pressure evolution have shown that the Skagerrak fluvial sandstones have undergone a complex diagenetic and pore pressure history that has helped to preserve the high porosities. There have been four phases of overpressure build-up during periods of rapid burial since deposition of the Skagerrak, in the Late Triassic, in the Late Cretaceous, from the Eocene into the Oligocene, and from the mid-Pliocene to the present. Overpressure development combined with dissolution of Permian and Triassic evaporites was key to the maintenance of high primary porosities in the Skagerrak reservoirs. In the channel and sheet flood sandstones, only a small amount of porosity has been lost due to cementation, in the range from 2% to 10%. The typical pore water chemistry varies from brackish Cl-Na to hypersaline Cl-Na-Ca water types, with an unusually low concentration of SO42+ and very high concentrations of Ca2+ and K+. Pore fluid with high salinity also accelerated the dissolution of calcite cement and the development of secondary porosity. Deposition of macroquartz and clay mineral cements has been inhibited by a combination of factors: the presence of early grain-coating cements, early development of overpressure, high pore fluid salinities, flushing with super-saline solutions, and possibly hydrocarbon migration. Quartz overgrowth and partial grain dissolution reduce from 6% and 8% of the total volume, respectively, in areas where overpressure is about 22 MPa to 2% and 3%, respectively, in areas where overpressure is about 40 MPa.

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

2010-05-01

316

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

Federal Register 2010, 2011, 2012, 2013, 2014

...Reclamation, the Prescott National Forest, the Tonto National Forest, the Luke Air Force Base...historic times. The Agua Fria National Monument includes 70,900 acres...200 acres of mineral estate in Coconino County in northern...

2010-04-22

317

Influence of fluvial processes on the quaternary geologic framework of the continental shelf, North Carolina, USA  

USGS Publications Warehouse

Digital, single-channel, high-resolution seismic reflection profiles were acquired from the insular continental shelf of North Carolina, USA along a data grid extending from Oregon Inlet northward 48 km to Duck, North Carolina and from the nearshore zone seaward approximately 28 km (total surveyed area= 1334 km2). These data were processed and interpreted to delineate principal reflecting horizons and develop a three-dimensional seismic stratigraphic framework for the continental shelf that was compared to stratigraphic data from the shoreward back-barrier (estuarine) and barrier island system. Six principal reflecting horizons (designated R0 through R5) were present within the upper 60 m of the shelf stratigraphic succession. Three-dimensional mapping of reflector R1 demonstrated its origin from fluvial incision of the continental shelf during an episode (or episodes) of lowered sea-level. Fluvial processes during development of reflector R1 were responsible for extensive reworking and re-deposition of sediment throughout most of the northern half of the study area. Five seismic stratigraphic units (designated S1 through S5) were tentatively correlated with depositional sequences previously identified from the North Carolina back-barrier (estuarine) and barrier island system. These five stratigraphic units span the Quaternary Period (S1 = early Holocene; S2 = 51-78 ka; S3 = 330-530 ka; S4 = 1.1-1.8 Ma; S5 = earliest Pleistocene). Unit S1 is composed of fine-grained fluvial/estuarine sediment that back-filled incised streams during early Holocene sea-level rise. The four other stratigraphic units (S2-S5) display tabular depositional geometries, low total relief, and thicken toward the east-southeast as their basal reflectors dip gently between 0.41 m km-1 (0.02??) and 0.54 m km-1 (0.03??). Knowledge of the three-dimensional subsurface stratigraphic architecture of the continental shelf enhances understanding of the development of shelf depositional successions and provides a framework for development of better Quaternary sea-level data, especially offshore North Carolina where such data are sparse. ?? 2002 Elsevier Science B.V. All rights reserved.

Boss, S.K.; Hoffman, C.W.; Cooper, B.

2002-01-01

318

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

319

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

320

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

321

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

322

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

323

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

NASA Astrophysics Data System (ADS)

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

Wynn, T.; Hopkinson, L. C.

2009-12-01

324

Late Pleistocene differential uplift inferred from the analysis of fluvial terraces (southern Apennines, Italy)  

NASA Astrophysics Data System (ADS)

The stratigraphic architecture and morphological assemblage of the Pleistocene fluvial terraces contained in two contiguous fluvial valleys are used to understand the spatial distribution and the timing of the differential uplift that affected two different geological and geomorphological settings of an active orogen. The study areas, both placed in the eastern sector of the southern Apennines of Italy, are the Sant'Arcangelo sedimentary basin and the Valsinni Ridge anticline. Pleistocene uplift rate of 0.7-0.9 mm y- 1 and historical earthquakes affecting those areas suggest active tectonics. Based on the synthem units used to classify the fluvial deposits in the field, several strath, fill, and fill-cut terraces have been mapped in the middle valleys of the Agri and Sinni rivers. Four Middle Pleistocene high terraces (Qes) are found in the Sant'Arcangelo Basin and cut its infill, and three Late Pleistocene low terraces (Qt) are found at both the Agri and Sinni valley flanks. The Agri and Sinni rivers cross-cut the NW-SE-oriented fold-and-thrust belt of the southern Apennines from W to E, producing a transverse drainage. As a result, ten- to hundred-metre deep gorges and wide floodplains were created in the middle reach of the river valleys. Computation of the bedrock incision rates from the Qes1, Qes4, and SQt1 terraces, corresponding to 1.2 ± 0.2 mm y- 1 at 400-240 ka and 0.8 ± 0.2 mm y- 1 in the last 240 ka, together with the terrace profile arrangements in the Agri and Sinni valleys, allow for the documentation of i) the differential uplift of the study area and ii) the age of terrace abandonment corresponding to the beginning age of the vertical incision in the valley floor sediments to form the Qt terraces. The differential uplift is subsequently discussed in a space and time-sequence evolution of the Late Pleistocene to assess the complex morphotectonic development that occurred in the eastern threshold of the basin. The differential uplift of both the Sant'Arcangelo Basin and Valsinni Ridge would appear to indicate that buried fold-and-thrust structures that affect the Mesozoic-Cenozoic sedimentary nappes are still active, and they also controlled the slab retreat processes in the Mediterranean region during the Late Pleistocene.

Giano, Salvatore Ivo; Giannandrea, Paolo

2014-07-01

325

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

Microsoft Academic Search

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

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

2010-01-01

326

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

327

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

328

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

329

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

330

Crater degradation in the Martian highlands: Morphometric analysis of the Sinus Sabaeus region and simulation modeling suggest fluvial  

E-print Network

Crater degradation in the Martian highlands: Morphometric analysis of the Sinus Sabaeus region] Results from simulation modeling of crater degradation by fluvial and eolian processes are compared with size-frequency and depth of infilling statistics for the heavily cratered Sinus Sabaeus quadrangle

Howard, Alan D.

331

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

USGS Publications Warehouse

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

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

2008-01-01

332

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

E-print Network

Controls on large-scale patterns of fluvial sandbody distribution in alluvial to coastal plain Orleans, 2000 Lakeshore Drive, New Orleans, Louisiana 70148, USA àUni CIPR, University of Bergen, P.O. Box 94583- 0719, USA Associate Editor ­ Andrea Moscariello ABSTRACT Current models of alluvial to coastal

Kulp, Mark

333

Restoration of riparian vegetation in the south-western United States: importance of flow regimes and fluvial dynamism  

Microsoft Academic Search

Riparian ecosystems in the south-western United States have undergone extensive physical and biological changes, due, in part, to alteration of natural flow regimes and suppression of fluvial processes. Many riparian ecosystem restoration projects are achieving success because they recognize the importance of restoring the hydrologic regime. In other words, these projects are restoring flows of water and sediment in sufficient

Juliet C. Stromberg

2001-01-01

334

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

335

Differences in abiotic water conditions between fluvial reaches and crayfish fauna in some northern rivers of the Iberian Peninsula  

Microsoft Academic Search

We studied the distribution patterns of the native European white-clawed crayfish (Austropotamobius pallipes) and the introduced signal crayfish (Pacifastacus leniusculus), and looked at the water chemistry in several streams in the north of the Iberian Peninsula (Cantabrian watershed). Fifty fluvial reaches which were currently or previously inhabited by crayfish and had physical attributes similar to the known habitat requirements of

Ana Rallo; Loreto García-Arberas

2002-01-01

336

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

337

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

Microsoft Academic Search

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

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

2007-01-01

338

Sediment Transfer through the Fluvial System (Proceedings of a symposium held in Moscow, August 2004). IAHS Publ. 288, 2004  

E-print Network

-term sediment records they examined. Interpretations of extensive sediment-discharge records requireSediment Transfer through the Fluvial System (Proceedings of a symposium held in Moscow, August 2004). IAHS Publ. 288, 2004 235 Decreasing sediment yields in northern California: vestiges

James, L. Allan

339

Fluvial sequences as evidence for landscape and climatic evolution in the Late Cenozoic: A synthesis of data from IGCP 518  

NASA Astrophysics Data System (ADS)

This editorial synthesis introduces a collection of papers derived from International Geoscience Programme (IGCP) Project 518, entitled 'Fluvial Sequences as Evidence for Landscape and Climatic Evolution in the Late Cenozoic'. Building on information collected during an earlier project (IGCP 449: 'Global Correlation of Late Cenozoic Fluvial Deposits'), this has examined the data accumulated on fluvial records, particularly river terrace sequences, for patterns that contribute to the interpretation of Late Cenozoic landscape and climatic evolution. This introductory paper reviews the baseline evidence, noting that there are patterns (from terrace sequences in different regions) of differing amounts of fluvial incision, indicating differing uplift rates, that appear to be related to crustal province. There seems to be no general role for plate tectonics; instead the patterns are of regional uplift, probably an isostatic response to erosion, enhanced by positive feedback effects, arguably due to lower-crustal flow. As well as depocentres, which are subsiding due to loading by accumulating sediment, cratonic areas are also exceptions to the rule of widespread uplift; these show minimal Late Cenozoic uplift, presumably because they lack mobile lower crust. The ten papers that follow are reviewed briefly in this context, these being contributions concerning Turkey, the Black Sea margin of Ukraine, Morocco (×2), the Czech Republic, Britain (×2), the Netherlands, New Zealand, and China.

Westaway, Rob; Bridgland, David R.; Sinha, Rajiv; Demir, Tuncer

2009-09-01

340

Fluvial dynamics of an anabranching river system in Himalayan foreland basin, Baghmati river, north Bihar plains, India  

Microsoft Academic Search

Anabranching river systems are now regarded as a separate class in river classifications owing to their distinctive morphological\\/hydrological characteristics and fluvial processes. A better understanding of anabranching rivers still needs detailed data from different environmental and geographical settings. This paper presents a detailed account of an anabranching river system from the Himalayan foreland basin. The Baghmati river system from north

Vikrant Jain; R. Sinha

2004-01-01

341

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

342

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

Microsoft Academic Search

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

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

1997-01-01

343

An intense terminal epoch of widespread fluvial activity on early Mars: 1. Valley network incision and associated deposits  

Microsoft Academic Search

We present evidence that a final epoch of widespread fluvial erosion and deposition in the cratered highlands during the latest Noachian or early to mid-Hesperian was characterized by integration of flow within drainage networks as long as 4000 km and trunk valley incision of 50 to 350 m into earlier Noachian depositional basins. Locally deltaic sediments were deposited where incised

Alan D. Howard; Jeffrey M. Moore; Rossman P. Irwin

2005-01-01

344

Agua Caliente Solar Feasibility and Pre-Development Study Final Report  

SciTech Connect

Evaluation of facility- and commercial-scale solar energy projects on the Agua Caliente Band of Cahuilla Indians Reservation in Palm Springs, CA. The Agua Caliente Band of Cahuilla Indians (ACBCI) conducted a feasibility and pre-development study of potential solar projects on its lands in southern California. As described below, this study as a logical and necessary next step for ACBCI. Support for solar project development in California, provided through the statewide California Solar Initiative (CSI), its Renewable Portfolio Standard and Feed-in Tariff Program, and recently announced Reverse Auction Mechanism, provide unprecedented support and incentives that can be utilized by customers of California's investor-owned utilities. Department of Energy (DOE) Tribal Energy Program funding allowed ACBCI to complete its next logical step to implement its Strategic Energy Plan, consistent with its energy and sustainability goals.

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

2011-04-26

345

SEISMIC STUDY OF THE AGUA DE PAU GEOTHERMAL PROSPECT, SAO MIGUEL, AZORES.  

USGS Publications Warehouse

A 16 station array was operated over the 200 km**2 central portion of Sao Miguel utilizing 8 permanent Instituto Nacional de Meterologia e Geofisica stations and 8 USGS portable stations. Forty four local events with well constrained solutions and 15 regional events were located. In addition, hundreds of unlocatable seismic events were recorded. The most interesting seismic activity occurred in a swarm on September 6 and 7, 1983 when over 200 events were recorded in a 16 hour period. The seismic activity around Agua de Pau was centered on the east and northeast slopes of the volcano. The data suggest a boiling hydrothermal system beneath the Agua de Pau volcano, consistent with a variety of other data.

Dawson, Phillip B.; Rodrigues da Silva, Antonio; Iyer, H.M.; Evans, John R.

1985-01-01

346

Lower and lower Middle Pennsylvanian fluvial to estuarine deposition, central Appalachian basin: Effects of eustasy, tectonics, and climate  

USGS Publications Warehouse

Interpretations of Pennsylvanian sedimentation and peat accumulation commonly use examples from the Appalachian basin because of the excellent outcrops and large reserve of coal (>100 billion metric tons) in the region. Particularly controversial is the origin of Lower and lower Middle Pennsylvanian quartzose sandstones; beach-barrier, marine-bar, tidalstrait, and fluvial models all have been applied to a series of sand bodies along the western outcrop margin of the basin. Inter-pretations of these sandstones and their inferred lateral relationships are critical for understanding the relative degree of eustatic, tectonic, and climatic controls on Early Pennsylvanian sedimentation. Cross sections utilizing >1000 subsurface records and detailed sedimentological analysis of the Livingston Conglomerate, Rockcastle Sandstone, Corbin Sandstone, and Pine Creek sandstone (an informal member) of the Breathitt Group were used to show that each of the principal quartzose sandstones on the margin of the central Appalachian basin contains both fluvial and marginal marine facies. The four sandstones are fluvially dominated and are inferred to represent successive bed-load trunk systems of the Appalachian foreland. Base-level rise and an associated decrease in extra-basinal sediment at the end of each fluvial episode led to the development of local estuaries and marine reworking of the tops of the sand belts. Each of the sand belts is capped locally by a coal, regardless of whether the upper surfaces of the sand belts are of fluvial or estuarine origin, suggesting allocyclic controls on deposition. Peats were controlled by a tropical ever-wet climate, which also influenced sandstone composition through weathering of stored sands in slowly aggrading braidplains. Recurrent stacking of thick, coarse-grained, fluvial deposits with extra-basinal quartz pebbles; dominance of bed-load fluvial-lowstand deposits over mixed-load, estuarine-transgressive deposits; thinning of sand belts around tectonic highs and along faults; cratonward shift and amalgamation of successive sand belts on the margin of the basin; and truncation of successive sand belts toward the fault-bound margin of the basin are interpreted as regional responses to Alleghenian tectonism, inferred to have been the dominant control on accommodation space and sediment flux in the Early Pennsylvanian basin.

Greb, S.F.; Chesnut, D.R., Jr.

1996-01-01

347

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

348

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

Microsoft Academic Search

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

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

1970-01-01

349

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

350

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

NASA Astrophysics Data System (ADS)

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

Schultz, Colin

2012-04-01

351

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

PubMed

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

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

2014-07-01

352

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

353

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

354

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

SciTech Connect

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

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

1999-04-28

355

Rock magnetic study of fluvial Holocene soil from Buenos Aires province (Argentina)  

NASA Astrophysics Data System (ADS)

The magnetic characteristics of soils are widely used in environmental and paleoclimatic investigations for studying the several factors involved in the soil formation process. We propose here a new analytical tool that takes into account the variations in magnetic properties correlated with grain sizes and concentrations of ferrimagnetic minerals. This analytical tool is based on a mathematical model of well-established magnetic properties in samples of known grain sizes and was used in this study to determine changes in the grain size and concentration of ferrimagnetic minerals along a terminal Pleistocene/Holocene fluvial section located in the northeast of Buenos Aires province. These variations may reflect a humid period prevailing in the area and may be associated with climate changes that occurred in the Chaco-Pampean region during the Middle Holocene.

Vasquez, Carlos A.; Nami, Hugo G.

2006-10-01

356

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

357

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

358

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

NASA Astrophysics Data System (ADS)

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

Uribelarrea, David; Benito, Gerardo

2008-08-01

359

Oceanographic Processes in the Region of Fluvial Influence of the Itajaí-Açu River  

NASA Astrophysics Data System (ADS)

The oceanographic processes in the region of fluvial influence (ROFI) of the Itajaí-Açu river were assessed through fourteen monthly surveys from November 2002 until December 2003. The main objective of this study was to investigate the effects of the fluvial riverine in the physical, biogeochemical and biological processes in the ROFI. Twenty eight sampling stations were positioned in five transects oriented in a radial shape from the estuarine mouth, with further two stations in the estuary. The transects length was about of 5-km each, reaching the isobath of 25 m. CTD, turbidity and dissolved oxygen profiles were acquired in all stations. Chlorophyll-a were sampled at surface in all stations. Water samples for determination of suspended particulate matter, dissolved inorganic nutrients, chlorophyll-a, phytoplankton and bacterioplankton were sampled in ten stations at surface and near bottom levels. The water samples stations were taken in selected stations to cover all studied area, where was also sampled zooplankton with a ring net. Current speed and direction were acquired with an ADCP moored about 1.5 km off the estuarine mouth at 10 m deep, from November 2002 until March 2003. The river discharge was below the average during most of the sampling period. Although, low salinity water was a permanent feature in the vicinity of the estuarine mouth. The estuarine plume dispersion was allways to north-northeast, what was observed by surface low salinity and higher concentrations of dissolved inorganic nutrients and chlorophyll-a. Below the surface layer, in all ROFI, the water column was dominated by salinity about of 33, named as Coastal Waters. Oceanic waters (salinity higher than 35) were observed only during the summer, with presence of Tropical Water and South Atlantic Central Water. Currents off the estuarine mouth presented strong low frequency signal, with dominance of longshore orientation. Despite of the limitation of the near surface ADCP data, it was possible to observe the plume effects, inducing offshore currents.

Schettini, C. A.; Truccolo, E. C.; Pereira, J.; Rörig, L. R.; Resgalla, C.

2005-05-01

360

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

361

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

362

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

363

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

PubMed

Climate strongly affects the production of sediment from mountain catchments as well as its transport and deposition within adjacent sedimentary basins. However, identifying climatic influences on basin stratigraphy is complicated by nonlinearities, feedback loops, lag times, buffering and convergence among processes within the sediment routeing system. The Palaeocene/Eocene thermal maximum (PETM) arguably represents the most abrupt and dramatic instance of global warming in the Cenozoic era and has been proposed to be a geologic analogue for anthropogenic climate change. Here we evaluate the fluvial response in western Colorado to the PETM. Concomitant with the carbon isotope excursion marking the PETM we document a basin-wide shift to thick, multistoried, sheets of sandstone characterized by variable channel dimensions, dominance of upper flow regime sedimentary structures, and prevalent crevasse splay deposits. This progradation of coarse-grained lithofacies matches model predictions for rapid increases in sediment flux and discharge, instigated by regional vegetation overturn and enhanced monsoon precipitation. Yet the change in fluvial deposition persisted long after the approximately 200,000-year-long PETM with its increased carbon dioxide levels in the atmosphere, emphasizing the strong role the protracted transmission of catchment responses to distant depositional systems has in constructing large-scale basin stratigraphy. Our results, combined with evidence for increased dissolved loads and terrestrial clay export to world oceans, indicate that the transient hyper-greenhouse climate of the PETM may represent a major geomorphic 'system-clearing event', involving a global mobilization of dissolved and solid sediment loads on Earth's surface. PMID:23128230

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

2012-11-01

364

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

365

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

NASA Astrophysics Data System (ADS)

SummaryConventional techniques for quantifying and then managing flood risks are invalid under 'non-stationary' climate conditions. Trend detection and attribution are problematic given that the outcome depends on the start and end date of the record, choice of index and test statistic, assumed behaviour of the system, and many non-climatic confounding factors. Analyses are further hampered by short and non-homogeneous flow records. In this paper, we use an objective weather classification scheme to reconstruct the atmospheric drivers of fluvial flood occurrence and magnitude in England, Scotland and Wales since the 1870s. We demonstrate the index using long (>50 year) annual maximum (AMAX) and peak over threshold (POT) flood records for 114 stations. Synoptic indices show modest skill at hindcasting multi-decadal variations in flood frequency at national, regional and catchment scales, but not for flood magnitudes. Flood rich episodes are identified in the periods 1908-1934, 1977-1988 and from 1998 onwards. We find that five weather types account for 68% of flood occurrence, and just three types were linked to the most widespread winter floods. These flood-generating systems generally show no sustained changes in frequency, persistence, relative contribution, or rain-bearing properties since the 1930s. However, there are emergent patterns in the day-to-day persistence (declining) and mean precipitation yield (rising) of anticyclonic weather types that merit further investigation. Based on our evaluation, we recommend use of objective weather indices derived from observed atmospheric pressure patterns when interpreting fluvial flood risk linked to climate drivers.

Wilby, Robert L.; Quinn, Nevil W.

2013-04-01

366

Geochemical investigations on fluvial sediments contaminated by tin-mine tailings, Cornwall, England  

NASA Astrophysics Data System (ADS)

Tin-mine tailings containing high concentrations of Sn, Cu, Zn, Fe, Mn, As, and W are discharged into the Red River of cornwall, England and are then transported into St. Ives Bay under normal flow conditions. Most of the tin-bearing particles in the fluvial sediments are smaller than 170 ?m, but tin-bearing composite grains or mineral grains with tin interspersed in the crystal lattices also occur in coarser size fractions. Tin distribution in the sediments is controlledby: (1) the distance from the source of the tailings, and (2) the concentration processes operating on the river bed. Suspended sediment and sediment transported by saltation filtered from river water samples also showed high concentrations of metals although, in contrast to the bottom sediments, they vary within a narrow range. Distributions of Cu, Zn, Fe, As, and Pb in the filtered sediments probably are related to the physical and chemical behavior of their sulphide minerals during fluvial transportation. A regional stream-sediment geochemical reconnaissance survey for tin did not show the highest concentration in the Red River; this indicated that in other rivers and streams tin reconcentration by selective removal of light minerals had taken place in the bottom sediments after mining operations had ceased. These rivers and streams also can transport large quantitiies of land-derived sediment including tin-mine tailings discharged into them when mines were operating. The minimum distance of tin transported by the Red River is at least 10 km; however, most of the tin was derived from mine tailings and is considered to be unnatural.

Yim, W. W.-S.

1981-09-01

367

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

368

ESTIMACIN DE PARMETROS ESTRUCTURALES EN RISERS MARINOS UTILIZANDO FILTROS DE KALMAN  

E-print Network

ESTIMACI�N DE PARÁMETROS ESTRUCTURALES EN RISERS MARINOS UTILIZANDO FILTROS DE KALMAN EXTENDIDOS STRUCTURAL PARAMETER ESTIMATION IN MARINE RISERS USING EXTENDED KALMAN FILTERS LIZETH TORRES ORTIZ Instituto. Torres, C. Verde, O. Vázquez, "Parameter identification of marine risers using an extended Kalman filter

Boyer, Edmond

369

Middle Pleistocene to Holocene fluvial terrace development and uplift-driven valley incision in the SE Carpathians, Romania  

NASA Astrophysics Data System (ADS)

This study reveals that in the SE Carpathians terrace development and fluvial incision during the Middle Pleistocene-Holocene are predominantly controlled by tectonic uplift as shown by terrace distributions and uplift amounts and rates. The work focuses on a transect from the internal nappes and Bra?ov intramontane basin (western domain) to the external nappes and Foc?ani foredeep basin (eastern domain). New infrared stimulated luminescence ages were obtained and minimum terrace formation ages were determined to derive fluvial incision rates, and thereby, to constrain tectonic uplift. In the eastern domain, non-uniform terrace distributions in adjacent sub-parallel more active Punta and less active ?u?i?a rivers and an eastward migrated fluvial incision from the orogen to the foredeep basin indicate tectonic uplift as dominant control on terrace development. Strath-terraces in the western and eastern domains indicate repeated events of vertical fluvial incision and lateral erosion during the early Middle Pleistocene and late Middle Pleistocene-Holocene, respectively. These events imply successive recurrent disturbances of equilibrium conditions due to pulses of increased tectonic uplift. Fill-terraces in the western domain show that initial aggradation periods were followed by uplift-driven vertical incision during the late Middle-Late Pleistocene. As fill-terraces show a wide-spread development, climatic change and complex response cannot be excluded as contributing factors. Synchronous to terrace development, loess deposition periods during the late Middle-Late Pleistocene and Latest Pleistocene and intercalated episodes of palaeosol formation during the Late Pleistocene imply comparable climatic conditions across the SE Carpathians. Dominant strath-terraces of the eastern domain indicate stronger fluvial incision (~ 240 m) since the late Middle Pleistocene, whereas older strath- and younger dominant fill-terraces of the western domain designate a lower amount (~ 90 m) since the early Middle Pleistocene. Middle Pleistocene-Holocene fluvial incision rates document higher tectonic uplift in the external nappes and lower towards the western intramontane and eastern foredeep basins.

Necea, D.; Fielitz, W.; Kadereit, A.; Andriessen, P. A. M.; Dinu, C.

2013-08-01

370

Dispersion of channel-sediment contaminants in distributary fluvial systems: Application to fluvial tephra and radionuclide redistribution following a potential volcanic eruption at Yucca Mountain  

NASA Astrophysics Data System (ADS)

Predicting the fluvial transport and mixing of channel-sediment contaminants is necessary for assessing and mitigating heavy-metal and nuclear-waste contamination in rivers. The dilution-mixing model is widely used for this purpose in tributary channel systems that transport contaminants as bed-material load without significant overbank sedimentation. Here a more general, three-dimensional (3D) contaminant transport numerical model is developed and tested based on bed scour, turbulent mixing of contaminant material with uncontaminated channel-bed sediments, and re-deposition of the mixture by the cumulative effect of many flood events. First, the model is applied to a synthetic alluvial-fan environment downstream from a localized contaminant source in order to illustrate the model behavior. Second, the model is validated against measured tephra concentrations in channels downstream from the Lathrop Wells scoria cone volcano, a localized source of basaltic tephra to downstream channels otherwise comprised of non-basaltic sediments. Third, the model is applied to the problem of predicting the concentration of radionuclide-bound tephra in channels downstream from the proposed nuclear-waste repository at Yucca Mountain, Nevada, in the event of a volcanic eruption through the repository. Contaminated tephra is mobilized from the landscape in this model using threshold criteria for hillslope gradient and channel stream power. Mobilized contaminated tephra is mixed with uncontaminated channel-bed sediments using the contaminant transport model and deposited in channels of the Fortymile Wash alluvial fan where the residents nearest to the proposed repository live. The results of twenty Monte Carlo simulations of eruption fallout and post-eruption redistribution corresponding to a range of wind conditions and eruption magnitudes provide information on the mean and variability of contaminated tephra concentrations to be expected in channels of the Fortymile Wash alluvial fan in the event of an eruption. Mean tephra concentrations are approximately 1% but vary from nearly zero to as high as 26%, reflecting the combined effects of wind direction, eruption magnitude, and dilution of tephra with uncontaminated channel-bed sediments during transport.

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

2008-02-01

371

Fluvial sediments a summary of source, transportation, deposition, and measurement of sediment discharge  

USGS Publications Warehouse

This paper presents a broad but undetailed picture of fluvial sediments in streams, reservoirs, and lakes and includes a discussion of the processes involved in the movement of sediment by flowing water. Sediment is fragmental material that originates from the chemical or physical disintegration of rocks. The disintegration products may have many different shapes and may range in size from large boulders to colloidal particles. In general, they retain about the same mineral composition as the parent rocks. Rock fragments become fluvial sediment when they are entrained in a stream of water. The entrainment may occur as sheet erosion from land surfaces, particularly for the fine particles, or as channel erosion after the surface runoff has accumulated in streams. Fluvial sediments move in streams as bedload (particles moving within a few particle diameters of the streambed) or as suspended sediment in the turbulent flow. The discharge of bedload varies with several factors, which may include particle size and a type of effective shear on the surface of the streambed. The discharge of suspended sediment depends partly on concentration of moving sediment near the streambed and hence on discharge of bedload. However, the concentration of fine sediment near the streambed varies widely, even for equal flows, and, therefore, the discharge of fine sediment normally cannot be computed theoretically. The discharge of suspended sediment also depends on velocity, turbulence, depth of flow, and fall velocity of the particles. In general, the coarse sediment transported by a stream moves intermittently and is discharged at a rate that depends on properties of the flow and of the sediment. If an ample supply of coarse sediment is available at the surface of the streambed, the discharge of the coarse sediment, such as sand, can be roughly computed from properties of the available sediment and of the flow. On the other hand, much of the fine sediment in a stream usually moves nearly continuously at about the velocity of the flow, and even low flows can transport large amounts of fine sediment. Hence, the discharge of fine sediments, being largely dependent on the availability of fine sediment upstream rather than on the properties of the sediment and of the flow at a cross section, can seldom be computed from properties, other than concentrations based directly on samples, that can be observed at the cross section. Sediment particles continually change their positions in the flow; some fall to the streambed, and others are removed from the bed. Sediment deposits form locally or over large areas if the volume rate at which particles settle to the bed exceeds the volume rate at which particles are removed from the bed. In general, large particles are deposited more readily than small particles, whether the point of deposition is behind a rock, on a flood plain, within a stream channel, or at the entrance to a reservoir, a lake, or the ocean. Most samplers used for sediment observations collect a water-sediment mixture from the water surface to within a few tenths of a foot of the streambed. They thus sample most of the suspended sediment, especially if the flow is deep or if the sediment is mostly fine; but they exclude the bedload and some of the suspended sediment in a layer near the streambed where the suspended-sediment concentrations are highest. Measured sediment discharges are usually based on concentrations that are averages of several individual sediment samples for a cross section. If enough average concentrations for a cross section have been determined, the measured sediment discharge can be computed by interpolating sediment concentrations between sampling times. If only occasional samples were collected, an average relation between sediment discharge and flow can be used with a flow-duration curve to compute roughly the average or the total sediment discharges for any periods of time for which the flow-duration c

Colby, B.R.

1963-01-01

372

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

373

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

NASA Astrophysics Data System (ADS)

Dryland environments are estimated to cover around 40% of the global land surface (Okin et al, 2009) and are home to approximately 2.5 billion people (Reynolds et al. 2007). Many of these areas have recently experienced extensive land degradation. One such area and the focus of this project is the semi-arid US Southwest, where degradation over the past 150 years has been characterized by the invasion of woody vegetation into grasslands. Transition from grass to woody vegetation results in a change in ecosystem structure and function (Turnbull et al, 2008). Structural change is typically characterised by an increased heterogeneity of soil and vegetation resources, associated with reduced vegetation coverage and an increased vulnerability to soil erosion and the potential loss of key nutrients to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is sequestered by these environments and the amount of carbon that is lost as the land becomes more degraded. Therefore, understanding these vegetation transitions is significant for sustainable land use and global biogeochemical cycling. This project uses an ecohydrological approach, monitoring natural rainfall-runoff events over six bounded plots with different vegetation coverage. The experiment takes advantage of a natural abundance stable 13C isotope shift from C3 piñon-juniper (Pinus edulis-Juniperus monosperma) mixed stand through a C4 pure-grass (Bouteloua eriopoda) to C3 shrub (Larrea tridentate). Data collected quantify fluvial fluxes of sediment and associated soil organic matter and carbon that is lost from across the grass-to-shrub and grass-to-woodland transition (where change in space is taken to indicate a similar change through time). Results collected during the 2010 and 2011 monsoon seasons will be presented, illustrating that soil and carbon losses are greater as the ecosystem becomes more dominated by woody plants. Additionally this project utilises novel biogeochemical techniques, using stable 13C isotope and lipid biomarker analyses, to trace and partition fluvial soil organic matter and carbon fluxes during these events. Results show that biomarkers specific to individual plant species can be used to define the provenance of carbon, quantifying whether more piñon or juniper-derived carbon is mobilised from the upland plots, or whether more Larrea tridentate carbon is lost when compared to bouteloa eripoda losses in the lowlands. The combined approach of monitoring carbon fluxes and tracing types of carbon shows great promise for improved understanding of carbon dynamics in areas subject to rapid vegetation change. References Okin, G. S., A. J. Parsons, J. Wainwright, J. E. Herrick, B. Bestelmeyer, T., D. C. Peters, and E. L. Fredrickson. 2009. Do Changes in Connectivity Explain Desertification? Bioscience 59:237-244. Reynolds JF, et al. 2007. Global desertification: Building a science for dryland development. Science 316: 847-851. Turnbull, L., J. Wainright, and R. E. Brazier. 2008. A conceptual framework for understanding semi-arid land degradation: ecohydrological interactions across multiple-space and time scales. Ecohydrology 1:23-34.

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

2011-12-01

374

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

375

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

376

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

377

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

378

A consistent magnetic polarity stratigraphy of Plio-Pleistocene fluvial sediments from the Heidelberg Basin (Germany)  

NASA Astrophysics Data System (ADS)

Deep drillings in the Heidelberg Basins provide access to one of the thickest and most complete successions of Quaternary and Upper Pliocene continental sediments in Central-Europe [1]. In absence of any comprehensive chronostratigraphic model, these sediments are so far classified by lithological and hydrogeological criteria. Therefore the age of this sequence is still controversially discussed ([1], [2]). In spite of the fact that fluvial sediments are a fundamental challenge for the application of magnetic polarity stratigraphy we performed a thorough study on four drilling cores (from Heidelberg, Ludwigshafen and nearby Viernheim). Here, we present the results from the analyses of these cores, which yield to a consistent chronostratigraphic framework. The components of natural remanent magnetisation (NRM) were separated by alternating field and thermal demagnetisation techniques and the characteristic remanent magnetisations (ChRM) were isolated by principle component analysis [3]. Due to the coring technique solely inclination data of the ChRM is used for the determination of the magnetic polarity stratigraphy. Rock magnetic proxies were applied to identify the carriers of the remanent magnetisation. The investigations prove the NRM as a stable, largely primary magnetisation acquired shortly after deposition (PDRM). The Matuyama-Gauss boundary is clearly defined by a polarity change in each core, as suggested in previous work [4]. These findings are in good agreement with the biostratigraphic definition of the base of the Quaternary ([5], [6], [7]). The Brunhes-Matuyama boundary could be identified in core Heidelberg UniNord 1 and 2 only. Consequently, the position of the Jaramillo and Olduvai subchron can be inferred from the lithostratigraphy and the development of fluvial facies architecture in the Rhine system. The continuation of the magnetic polarity stratigraphy into the Gilbert chron (Upper Pliocene) allows alternative correlation schemes for the cores Viernheim and Heidelberg. All things considered, the application of magnetic polarity stratigraphy on Pliocene and Pleistocene fluvial sediments from the Heidelberg Basin provides a consistent and independent chronology and opens the perspective for global correlations where other approaches hardly come to results. [1] GABRIEL, G., ELLWANGER, D., HOSELMANN, C. & WEIDENFELLER, M. 2008. Preface: The HeidelbergBasin Drilling Project. E & G (Quaternary Science Journal), 57, 253-260. [2] ELLWANGER, D. & WIELAND-SCHUSTER, U. 2012. Fotodokumentation und Schichtenverzeichnis der Forschungsbohrungen Heidelberg UniNord I und II. LGRB-Informationen, 26, 25-86. [3] KIRSCHVINK, J. L. 1980. The least-squares line and plane and the analysis of palaeomagnetic data. Geophysical Journal, Royal Astronomical Society, 62, 699-718. [4] ROLF, C., HAMBACH, U. & WEIDENFELLER, M. 2008. Rock and palaeomagnetic evidence for the Plio-/Pleistocene palaeoclimatic change recorded in Upper Rhine Graben sediments (Core Ludwigshafen-Parkinsel), Neth. J. Geosci., 87 (1), 41-50. [5] KNIPPING, M. 2008. Early and Middle Pleistocene pollen assemblages of deep core drillings in the northern Upper Rhine Graben, Germany, Neth. J. Geosci., 87(1), 51-65. [6] HEUMANN, G., pers. Comm. [7] HAHNE, J., pers. Comm.

Scheidt, Stephanie; Hambach, Ulrich; Rolf, Christian

2014-05-01

379

Dynamic Processes of Large Wood and Their Effects on Fluvial Export at the Watershed Scale  

NASA Astrophysics Data System (ADS)

The presence of large wood (LW) has a pronounced impact on the geomorphic and ecological character of river corridors, yet relatively little is known about the patterns and processes at the watershed scale. To understand these patterns we monitored the volumetric input of LW into 131 reservoirs and a suite of watershed characteristics. Of all geomorphic and hydrologic variables tested, watershed area was most important in explaining LW export. LW export per unit watershed area was relatively high in small watersheds, peaked in intermediate-sized watersheds and decreased in large watersheds. To explain these variations, we surveyed the amount of LW with respect to channel morphology in 78 segments (26 segments in each size class) in the Nukabira River, northern Japan, and examined the differences in LW dynamics, including its recruitment, transport, storage, and fragmentation and decay along the spectrum of watershed sizes. We found in small watersheds a larger proportion of LW produced by forest dynamics and hillslope processes was retained due to narrower valley floors and lower stream power. The retained LW pieces may eventually be exported during debris flows. In intermediate-sized watersheds the volume of LW pieces derived from hillslopes decreased substantially with reductions of proportion of channel length bordered by hillslope margins, which potentially deliver large quantities of LW. Because these channels have lower wood piece length to channel width ratios and higher stream power, LW pieces can be transported downstream. During transport, LW pieces are further fragmented and can be more easily transported; and therefore, the fluvial export of LW is maximized in intermediate-sized watersheds. Rivers in large watersheds, where the recruitment of LW is limited by the decreasing hillslope margins, cannot transport LW pieces because of their low stream power and thus LW pieces accumulate at various storage sites. Although these stored LW pieces can be re-floated and transported by subsequent flood events, they may be also combed by obstacles such as log jams and standing trees on floodplains and in secondary channels. Redistribution on these surfaces can be up to decades with eventual decay into fine organic particles resulting in the reduction of fluvial export of LW in larger watersheds. Our findings provide important information for a role of LW pieces in regulating the dynamic character of geomorphic processes and aquatic habitats, and the transfer and residence time of energy for stream-dwelling organisms at the watershed scale.

Seo, J.; Nakamura, F.; Chun, K.

2008-12-01

380

A Survey of Sinuous Ridges and Inferred Fluvial Discharge Rates in Northwest Hellas, Mars  

NASA Astrophysics Data System (ADS)

Sinuous ridges are a widespread class of geomorphic feature on Mars, and in many cases are interpreted to be inverted fluvial channels. Although negative-relief valley networks thought to be related to fluvial activity have been mapped in detail over the entire planet (e.g. Carr, 1995; Hynek et al., 2010), few regional- to global-scale surveys of sinuous ridges have been conducted (e.g. Williams, 2007; Jacobsen and Burr, 2012). With the availability of Context Camera (CTX ) images from the Mars Reconnaissance Orbiter (MRO) covering a significant fraction of the martian surface at 6 meters per pixel, such studies are now feasible. In addition, Williams et al. (2009) have demonstrated that paleodischarge can be calculated based on the width, meander wavelength, and meander radius of sinuous ridges interpreted to be inverted channels. This method has been used successfully on the sinuous ridges in the Aeolis/Zephyria plana region (Burr et al., 2010). We have begun a survey of sinuous ridges in the northwest Hellas region (-15 N to -45 N, 30 E to 75 E) using 1156 radiometrically calibrated and map projected CTX images. This region includes the northwestern portion of the Hellas basin floor and rim, as well as a significant expanse of the cratered highlands to the north and west of the basin. This region was chosen because it includes terrain of varying age (primarily Noachian to Hesperian; Leonard and Tanaka, 2001) and includes "raised curvilinear features" identified by Williams (2007) on the western basin floor, northern rim, and in the highlands northwest of Hellas . By mapping the distribution of sinuous ridges in terrain of varying age and estimating their paleodischarge rates, we will be able to determine how the discharge rate varied over martian history. Carr, M. H. (1995), J. Geophys. Res., 100, 7479-7507, doi:10.1029/95JE00260. Hynek, B. M., M. Beach, and M. R. T. Hoke (2010), J. Geophys. Res., 115, E09008, doi:10.1029/2009JE003548. Williams, R.M.E. (2007), LPSC XXXVIII, Abstract #1821 Jacobsen, R.E. and Burr, D.M., (2012), LPSC XLIII, Abstract #2398 Williams, R.M.E., Irwin III, R.P., Zimbelman, J.R. (2009), Geomorphology 107, p.300-315. Burr, D. M., et al. (2010), J. Geophys. Res., 115, E07011, doi:10.1029/2009JE003496. Leonard, G.J. and Tanaka, K.L. (2001) USGS Geologic Investigations Series I-2694.

Anderson, R. B.; Herkenhoff, K. E.

2012-12-01

381

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

382

Interpreting ancient fluvial and deltaic environments on Mars: what can Earth analogs tell us?  

NASA Astrophysics Data System (ADS)

Reconstructing ancient sedimentary environments on Earth is not a trivial task. Sedimentologists typically use detailed analysis of sedimentary features in rocks together with geometrical stratigraphic relationships and couple this with models of modern systems to reconstruct palaeo-river and deltaic landform features and environments. However, the fidelity of these reconstructions is dependent on good outcrop control and an understanding of how geomorphic elements become frozen in the stratigraphic record. On Mars reconstruction of ancient fluvial and deltaic is on the one hand easier because in numerous examples the planform morphology of such systems preserved in the present-day landscape as relic palaeolandscape features. Such features are very rarely preserved on Earth's landsurface. However, care must be taken in such interpretations. Whilst we can observe point-sourced sedimentary bodies within craters typically emanating from channels that enter the crater, interpreting these as deltaic and determining the type of delta is hazardous. Prior studies have largely focused on establishing geomorphic relations from the large-scale planform bedrock morphology, however, this is dependent on the preservation state. On Earth, we reconstruct ancient deltas by careful analysis of sedimentary bedding patterns as observed in vertical sections. By lateral tracing of bedding we constrain the morphostratigraphy of depositional elements and the surfaces that bound them. The stratigraphy preserved however is not a static state of the river or delta, but instead is a complex of surfaces and sediment bodies that records lateral migration and vertical accumulation of landscape elements. The integration of HiRISE imagery with HiRISE digital terrain models enables Mars sedimentologists and stratigraphers to explore bedding patterns exposed in martian canyons. Whilst we cannot get a handle on the internal sedimentology of these deposits, the analysis of architectural elements and their geometrical disposition enables us to reconstruct the large-scale architecture of inferred martian fluvial and deltaic systems. Understanding this architecture is crucial to informed interpretation of such sedimentary deposits. Here, we analyse the morphology of fluvio-deltaic systems in Eberswalde crater, Mars, using a variety of Earth analogs to aid our analysis. We will examine large scale bedding geometries of the sort visible in spacecraft imagery, and consider how best one can make interpretations.

Gupta, S.; Goddard, K.; Rice, M. S.; Warner, N. H.; Kim, J.; Muller, J.

2011-12-01

383

Inputs and Fluvial Transport of Pharmaceutical Chemicals in An Urban Watershed  

NASA Astrophysics Data System (ADS)

Pharmaceuticals and personal care products (PPCPs) are classes of emerging chemical contaminants thought to enter the aquatic environment primarily through wastewater treatment plant (WTP) discharges. As the use of drugs is expected to rise with the aging demographics of the human population and with more river water being diverted to meet potable water demands, the presence of PPCPs in surface water is becoming an issue of public concern. The intent of our study was to quantify potential WTP inputs of PPCPs to rivers in the Wasington, DC (USA) region, and to investigate the fluvial transport of PPCPs in the Anacostia River (AR), the mainstem of a highly contaminated urban watershed in Washington, DC. The approach was to sample WTP water at various stages of treatment, and to measure seasonal concentrations of PPCPs in fluvial transport in the AR. Surface water from the AR was collected through the use of automated samplers during normal flow and storm flow regimes near the head of tide of the AR, just upstream from the confluence of the Northeast (NE) and Northwest (NW) Branches, the two prominent drainages in the watershed. The water samples were filtered to separate river particles from water, and the filtered water was extracted using solid phase extraction (SPE) cartridges. The filters were extracted by sonication in methanol. The SPE and filter extracts were analyzed for a group of widely distributed PPCPs as trimethylsilyl derivatives by using gas chromatography/mass spectrometry. The most frequently detected PPCPs at WTPs included ibuprofen, caffeine, naproxen and triclosan, which ranged from 45 ?g/L (caffeine) to 5 ?g/L (triclosan) in WTP influent and from 0.08 ?g/L (triclosan) to 0.02 ?g/L (ibuprofen) in effluent water. Similar PPCPs were detected in both the NE and NW Branches of the AR, but higher concentrations on average were observed in the NE Branch, which receives WTP effluent upstream from the sampling point. The incidence of PPCPs correlated with WTP discharge, but other sources appear to exist based on the occurrence of PPCPs in the NW Branch, which does not receive WTP discharge. Surface water concentrations of the PPCPs were only weakly dependent on the flow regime of the Anacosita River, ranging from 10 to 250 ng/L in AR water. PPCPs are transported in surface waters at parts per trillion concentrations throughout the year, but sources to the AR are not confined to WTPs.

Foster, G. D.; Shala, L.

2006-05-01

384

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

385

Late Cenozoic sedimentary sequences in Acre state, southwestern Amazonia: Fluvial or tidal? Deductions from the IGCP 449 fieldtrip  

NASA Astrophysics Data System (ADS)

The IGCP 449 fieldtrip in June 2003 drew attention to the Late Cenozoic fluvial sequences of western Amazonia. In Acre state in western Brazil, underlain by relatively mobile crust, rivers have incised up to 70 minto the stacked latest Miocene (?)/Early Pliocene (?) sediments of the Solimões Group, creating staircases of fluvial terraces and indicating regional uplift on this time scale. In contrast, in western Rondonia state, the Madeira River flows through the Early Proterozoic western part of the Amazon Craton, where Late Cenozoic vertical crustal motions seem minimal. The evidence in Acre suggests that the Solimões Group was deposited by an ancestral river system associated with the incipient development of the modern eastward Amazon drainage.

Westaway, Rob

2006-03-01

386

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

387

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

388

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

389

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

390

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

391

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

NASA Astrophysics Data System (ADS)

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

von Suchodoletz, Hans; Faust, Dominik

2013-04-01

392

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

393

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

394

Pre-vegetation fluvial floodplains and channel-belts in the Late Neoproterozoic-Cambrian Santa Bárbara group (Southern Brazil)  

NASA Astrophysics Data System (ADS)

One key element to the understanding of the dynamics of pre-vegetation fluvial systems is the reconstruction of processes operating on their floodplains given that, in modern systems, channel banks and floodplains are the environments most affected by plant colonization. Notwithstanding, few pre-vegetation floodplains have been described, and major questions regarding their most basic characteristics are still unresolved. In order to address these questions, detailed analysis of coeval channel-belt, fluvial floodplain and alluvial-fan deposits from the Santa Bárbara Group (Late Neoproterozoic to Early Cambrian, southern Brazil) was performed. While floodplain facies resemble ephemeral stream deposits, being coarser-grained than modern floodplains and marked by the stacking of flood event cycles, channel-belt deposits show composite bars, which do not present conclusive evidence for high water discharge variation. The floodplain deposits show particular features common to other pre-vegetation fluvial systems, such as better preserved small-scale structures, lack of bioturbation, and abundance of cross-laminated sandstones, while other features differ from previous depositional models, namely abundant mudcracks and evidence of soil formation. The lateral variation of depositional systems recorded in the Santa Bárbara Group shows contrasting signatures of water discharge variation in sand-dominated coeval environments, and offers an example of the relation between different alluvial environments before the evolution of land plants.

Marconato, André; de Almeida, Renato Paes; Turra, Bruno Boito; Fragoso-Cesar, Antônio Romalino dos Santos

2014-03-01

395

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

396

Holocene beaver damming, fluvial geomorphology, and climate in Yellowstone National Park, Wyoming  

NASA Astrophysics Data System (ADS)

We use beaver-pond deposits and geomorphic characteristics of small streams to assess long-term effects of beavers and climate change on Holocene fluvial activity in northern Yellowstone National Park. Although beaver damming has been considered a viable mechanism for major aggradation of mountain stream valleys, this has not been previously tested with stratigraphic and geochronologic data. Thirty-nine radiocarbon ages on beaver-pond deposits fall primarily within the last 4000 yr, but gaps in dated beaver occupation from ~ 2200-1800 and 950-750 cal yr BP correspond with severe droughts that likely caused low to ephemeral discharges in smaller streams, as in modern severe drought. Maximum channel gradient for reaches with Holocene beaver-pond deposits decreases with increasing basin area, implying that stream power limits beaver damming and pond sediment preservation. In northern Yellowstone, the patchy distribution and cumulative thickness of mostly < 2 m of beaver-pond deposits indicate that net aggradation forced by beaver damming is small, but beaver-enhanced aggradation in some glacial scour depressions is greater. Although 20th-century beaver loss and dam abandonment caused significant local channel incision, most downcutting along alluvial reaches of the study streams is unrelated to beaver dam abandonm