Environmental Science › Ecology

Hydrology and Sediment Transport Processes

Works Count: 70194

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Description

This cluster of papers explores the ecological dynamics and human impacts on riverine landscapes, focusing on topics such as river restoration, riparian vegetation, fluvial processes, sediment transport, channel morphology, hydrological impacts, vegetation dynamics, geomorphological effects, and floodplain connectivity.

Keywords

River Restoration; Riparian Vegetation; Fluvial Processes; Sediment Transport; Channel Morphology; Hydrological Impacts; Vegetation Dynamics; Geomorphological Effects; Floodplain Connectivity; Human Influence

Erosion and Deposition of Cohesive Soils

1965-01-01

Emmanuel Partheniades

The effects of shear stress, suspended sediment concentration, and shear strength of bed on the erosion rates of a cohesive bed in an open channel with salt water have been … The effects of shear stress, suspended sediment concentration, and shear strength of bed on the erosion rates of a cohesive bed in an open channel with salt water have been investigated. The deposition rates of suspended cohesive sediment and the patterns of bed erosion have been studied to a lesser extent. For the experimental range the erosion rates were found to be independent of the shear strength of the bed and the concentration of suspended sediment. They depend strongly on the bed shear stress. The minimum shear stresses for initiation of erosion were also found to be independent of the shear strength of bed. There seems to exist a critical velocity for the clay part of suspended sediment, above which all such sediment remains in suspension, whereas even for velocities slightly below this critical limit, the suspended clay deposits rapidly. Scouring occurred predominantly within a well defined narrow and relatively straight zone near the center of the flume.

Fluvial Forms and Processes

2014-04-08

David Knighton

David Knighton's best-selling book looks at the wide range of forms developed by natural rivers and the processes responsible for that development. The book combines empirical and theoretical approaches, and … David Knighton's best-selling book looks at the wide range of forms developed by natural rivers and the processes responsible for that development. The book combines empirical and theoretical approaches, and provides a critical assessment of the many schools of thought which have emerged for dealing with adjustment in the fluvial system. It is fully illustrated throughout by a superb range of figures, photographs and tables.Starting with the network scale, the book examines the interaction of hillslopes, drainage networks and channels, and goes on to considerations of catchment hydrology and catchment denudation. Fluvial processes are analysed in detail, from the mechanics of flow to sediment transport and deposition. Detailing the major components of river channels, the book examines the nature of river adjustment, particularly with respect to equilibrium concepts, and concludes with a look at channel changes through time, affected by flood discharges, climatic change and human activities.

River channel patterns: Braided, meandering, and straight

1957-01-01

Luna B. Leopold , M. Gordon Wolman

Channel pattern is used to describe the plan view of a reach of river as seen from an airplane, and includes meandering, braiding, or relatively straight channels.Natural channels characteristically exhibit … Channel pattern is used to describe the plan view of a reach of river as seen from an airplane, and includes meandering, braiding, or relatively straight channels.Natural channels characteristically exhibit alternating pools or deep reaches and riffles or shallow reaches, regardless of the type of pattern. The length of the pool or distance between riffles in a straight channel equals the straight line distance between successive points of inflection in the wave pattern of a meandering river of the same width. The points of inflection are also shallow points and correspond to riffles in the straight channel. This distance, which is half the wavelength of the meander, varies approximately as a linear function of channel width. In the data we analysed the meander wavelength, or twice the distance between successive riffles, is from 7 to 12 times the channel width. It is concluded that the mechanics which may lead to meandering operate in straight channels.River braiding is characterized by channel division around alluvial islands. The growth of an island begins as the deposition of a central bar which results from sorting and deposition of the coarser fractions of the load which locally cannot be transported. The bar grows downstream and in height by continued deposition on its surface, forcing the water into the flanking channels, which, to carry the flow, deepen and cut laterally into the original banks. Such deepening locally lowers the water surface and the central bar emerges as an island which becomes stabilized by vegetation. Braiding was observed in a small river in a laboratory. Measurements of the adjustments of velocity, depth, width, and slope associated with island development lead to the conclusion that braiding is one of the many patterns which can maintain quasi-equilibrium among discharge, load, and transporting ability. Braiding does not necessarily indicate an excess of total load.Channel cross section and pattern are ultimately controlled by the discharge and load provided by the drainage basin. It is important, therefore, to develop a picture of how the several variables involved in channel shape interact to result in observed channel characteristics. Such a rationale is summarized as follows:Channel width appears to be primarily a function of near-bankfull discharge, in conjunction with the inherent resistance of bed and bank to scour. Excessive width increases the shear on the bed at the expense of that on the bank and the reverse is true for very narrow widths. Because at high stages width adjustment can take place rapidly and with the evacuation or deposition of relatively small volumes of debris, achievement of a ,relatively stable width at high flow is a primary adjustment to which the further interadjustments between depth, velocity, slope, and roughness tend to accommodate.Channel roughness, to the extent that it is determined by particle size, is an independent factor related to the drainage basin rather than to the channel. Roughness in streams carrying fine material, however, is also a function of the dunes or other characteristics of bed configuration. Where roughness is independently determined as well as discharge and load, these studies indicate that a particular slope is associated with the roughness. At the width determined by the discharge, velocity and depth must be adjusted to satisfy quasi-equilibrium in accord with the particular slope. But if roughness also is variable, depending on the transitory configuration of the bed, then a number of combinations of velocity, depth, and slope will satisfy equilibrium.An increase in load at constant discharge, width, and caliber of load tends to be associated with an increasing slope if the roughness (dune or bed configuration) changes with the load. In the laboratory river an increase of load at constant discharge, width, and caliber resulted in progressive aggradation of long reaches of channel at constant slope.The adjustments of several variables tending toward the establishment of quasi-equilibrium in river channels lead to the different channel patterns observed in nature. For example, the data indicate that at a given discharge, meanders occur at smaller values of slope than do' braids. Further, at the same slope braided channels are associated with higher bankfull discharges than are meanders. An additional example is provided by the division of discharge around islands in braided rivers which produces numerous small channels. The changes in slope, roughness, and channel shape which accompany this division are in accord with quasi-equilibrium adjustments observed in the comparison of large and small rivers.

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Studies of longitudinal stream profiles in Virginia and Maryland

1957-01-01

John T. Hack

47 Mathematical expression of the longitudinal profile and Description of areas studied L 49 its relation to particle size of material on the bedL Middle River basinL 50 Mathematical expression … 47 Mathematical expression of the longitudinal profile and Description of areas studied L 49 its relation to particle size of material on the bedL Middle River basinL 50 Mathematical expression in previous work on longitudinal North River basinL 50 profiles L Alluvial terrace areasL 50 Origin and composition of stream-bed materialL Calfpasture River basinL 50 Franks Mill reach of the Middle River L Tye River basin L 52 Eidson CreekL Gillis Falls L 52 East Dry Branch L Coastal Plain streamsL 53 North RiverL Factors determining the slope of the stream channelL 53 Calfpasture ValleyL Discharge and drainage areaL 54 Gillis FallsL Size of material on the stream bedL 54 Ephemeral streams in areas of residuumL Channel cross sectionL 61 Some factors controlling variations in size: conclusions_ _ _ Summary of factors controlling channel slopeL 61 The longitudinal profile and the cycle of erosionL Factors determining the position of the channel in space: the References cited L shape of the long profileL 63 IndexL Relation of stream length to drainage area L 63 ILLUSTRATIONS

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Downstream effects of dams on alluvial rivers

1984-01-01

Garnett P. Williams , M. Gordon Wolman

This study describes changes in mean channel-bed elevation, channel width, bed-material sizes, vegetation, water discharges, and sediment loads downstream from 21 dams constructed on alluvial rivers.Most of the studied channels … This study describes changes in mean channel-bed elevation, channel width, bed-material sizes, vegetation, water discharges, and sediment loads downstream from 21 dams constructed on alluvial rivers.Most of the studied channels are in the semiarid western United States.Flood peaks generally were decreased by the dams, but in other respects the post-dam water-discharge characteristics varied from river to river.Sediment concentrations and suspended loads were decreased markedly for hundreds of kilometers downstream from dams; post-dam annual sediment loads on some rivers did not equal pre-dam loads anywhere downstream from a dam.Bed degradation varied from negligible to about 7.5 meters in the 287 cross sections studied.In general, most degradation occurred during the first decade or two after dam closure.Bed material initially coarsened as degradation proceeded, but this pattern may change during later years.Channel width can increase, decrease, or remain constant in the reach downstream from a dam.Despite major variation, changes at a cross section in streambed elevation and in channel width with time often can be described by simple hyperbolic equations.Equation coefficients need to be determined empirically.Riparian vegetation commonly increased in the reach downstream from the dams, probably because of the decrease in peak flows.

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An approach to the sediment transport problem from general physics

1966-01-01

R. A. Bagnold

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The hydraulic geometry of stream channels and some physiographic implications

1953-01-01

Luna B. Leopold , Thomas Maddock

Some hydraulic characteristics of stream channels - depth, width, velocity, and suspended load - are measured quantitatively and vary with discharge as simple power functions at a given river cross … Some hydraulic characteristics of stream channels - depth, width, velocity, and suspended load - are measured quantitatively and vary with discharge as simple power functions at a given river cross section. Similar variations in relation to discharge exist among the cross sections along the length of a river under the condition that discharge at all points is equal in frequency of occurrence. The functions derived for a given cross section and among various cross sections along the river differ only in numerical values of coefficients and exponents.

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Magnitude and Frequency of Forces in Geomorphic Processes

1960-01-01

M. Gordon Wolman , John P. Miller

The relative importance in geomorphic processes of extreme or catastrophic events and more frequent events of smaller magnitude can be measured in terms of (1) the relative amounts of "work" … The relative importance in geomorphic processes of extreme or catastrophic events and more frequent events of smaller magnitude can be measured in terms of (1) the relative amounts of "work" done on the landscape and (2) in terms of the formation of specific features of the landscape. For many processes, above the level of competence, the rate of movement of material can be expressed as a power function of some stress, as for example, shear stress. Because the frequency distributions of the magnitudes of many natural events, such as floods, rainfall, and wind speeds, approximate log-normal distributions, the product of frequency and rate, a measure of the work performed by events having different frequencies and magnitudes will attain a maximum. The frequency at which this maximum occurs provides a measure of the level at which the largest portion of the total work is accomplished. Analysis of records of sediment transported by rivers indicates that the largest portion of the total load is carried by flows which occur on the average once or twice each year. As the variability of the flow increases and hence as the size of the drainage basin decreases, a larger percentage of the total load is carried by less frequent flows. In many basins 90 per cent of the sediment is removed by storm discharges which recur at least once every five years. Transport of sand and dust by wind in general follows the same laws. The extreme velocities associated with infrequent events are compensated for by their rarity, and it is found that the greatest bulk of sediment is transported by more moderate events. Many rivers are competent to erode both bed and banks during moderate flows. Observations of natural channels suggest that the channel shape as well as the dimensions of meandering rivers appear to be associated with flows at or near the bankfull stage. The fact that the bankfull stage recurs on the average once every year or two years indicates that these features of many alluvial rivers are controlled by these more frequent flows rather than by the rarer events of catastrophic magnitude. Because the equilibrium form of wind-blown dunes and of wave-formed beaches is quite unstable, the frequency of the events responsible for their form is less clearly definable. However, dune form and orientation are determined by both wind velocity and frequency. Similarly, a hypothetical example suggests that beach slope oscillates about a mean value related in part to wave characteristics generated by winds of moderate speed. Where stresses generated by frequent events are incompetent to transport available materials, less frequent ones of greater magnitude are obviously required. Closer observation of many geomorphic processes is required before the relative importance of different processes and of events of differing magnitude and frequency in the formation of given features of the landscape can be adequately evaluated.

Riverine landscape diversity

2002-04-01

J. V. Ward , Klement Tockner , David B. Arscott +1 more

1. This review is presented as a broad synthesis of riverine landscape diversity, beginning with an account of the variety of landscape elements contained within river corridors. Landscape dynamics within … 1. This review is presented as a broad synthesis of riverine landscape diversity, beginning with an account of the variety of landscape elements contained within river corridors. Landscape dynamics within river corridors are then examined in the context of landscape evolution, ecological succession and turnover rates of landscape elements. This is followed by an overview of the role of connectivity and ends with a riverine landscape perspective of biodiversity. 2. River corridors in the natural state are characterised by a diverse array of landscape elements, including surface waters (a gradient of lotic and lentic waterbodies), the fluvial stygoscape (alluvial aquifers), riparian systems (alluvial forests, marshes, meadows) and geomorphic features (bars and islands, ridges and swales, levees and terraces, fans and deltas, fringing floodplains, wood debris deposits and channel networks). 3. Fluvial action (erosion, transport, deposition) is the predominant agent of landscape evolution and also constitutes the natural disturbance regime primarily responsible for sustaining a high level of landscape diversity in river corridors. Although individual landscape features may exhibit high turnover, largely as a function of the interactions between fluvial dynamics and successional phenomena, their relative abundance in the river corridor tends to remain constant over ecological time. 4. Hydrological connectivity, the exchange of matter, energy and biota via the aqueous medium, plays a major though poorly understood role in sustaining riverine landscape diversity. Rigorous investigations of connectivity in diverse river systems should provide considerable insight into landscape‐level functional processes. 5. The species pool in riverine landscapes is derived from terrestrial and aquatic communities inhabiting diverse lotic, lentic, riparian and groundwater habitats arrayed across spatio‐temporal gradients. Natural disturbance regimes are responsible for both expanding the resource gradient in riverine landscapes as well as for constraining competitive exclusion. 6. Riverine landscapes provide an ideal setting for investigating how complex interactions between disturbance and productivity structure species diversity patterns.

Threshold of sediment motion under unidirectional currents

1977-08-01

Martin C. Miller , I Nick McCave , Paul D. Komar

ABSTRACT Carefully selected data for the threshold of sediment movement under unidirectional flow conditions have been utilized to re‐examine the various empirical curves that are commonly employed to predict this … ABSTRACT Carefully selected data for the threshold of sediment movement under unidirectional flow conditions have been utilized to re‐examine the various empirical curves that are commonly employed to predict this threshold. After a review of the existing data, we employed only that data obtained from open channel flumes with parallel sidewalls where flows were uniform and steady over flattened beds of unigranular, rounded sediments. Without these restrictions, an unmanageable amount of scatter is introduced. This selected data is used to develop a modified Shields‐type threshold diagram that extends the limits of the original diagram by three orders of magnitude in the grain‐Reynolds number. The equally general but more easily employed Yalin diagram for sediment threshold is also examined. Although the Shields and Yalin diagrams are general in that they apply to a wide range of different liquids, in both cases somewhat different curves are obtained for threshold under air than for the liquids. The often used empirical curves of the friction velocity u * , the velocity 100 cm above the bed u 100 , the bottom stress θ t , and Shields’ relative stress θ t , all versus the grain diameter D , are limited in their ranges of application to certain combinations of grain density, fluid density, fluid viscosity and gravity. These conditions must be selected before the curves are generated from either the more general Shields or Yalin curves. For example, on the basis of the data selected for use in this paper, empirical threshold relationships for quartz density material in water are image where the velocity u 100 measured 100 cm above the sediment bed is given in cm/sec and the grain diameter D is in cm. The limitations on any of the threshold relationships are severe. These limitations should be properly understood so that the empirical curves and relationships are not improperly employed.

Brahmaputra river: Channel processes and sedimentation

1969-08-01

James M. Coleman

Dynamics of the stream‐power river incision model: Implications for height limits of mountain ranges, landscape response timescales, and research needs

1999-08-10

K. X. Whipple , Gregory E. Tucker

The longitudinal profiles of bedrock channels are a major component of the relief structure of mountainous drainage basins and therefore limit the elevation of peaks and ridges. Further, bedrock channels … The longitudinal profiles of bedrock channels are a major component of the relief structure of mountainous drainage basins and therefore limit the elevation of peaks and ridges. Further, bedrock channels communicate tectonic and climatic signals across the landscape, thus dictating, to first order, the dynamic response of mountainous landscapes to external forcings. We review and explore the stream‐power erosion model in an effort to (1) elucidate its consequences in terms of large‐scale topographic (fluvial) relief and its sensitivity to tectonic and climatic forcing, (2) derive a relationship for system response time to tectonic perturbations, (3) determine the sensitivity of model behavior to various model parameters, and (4) integrate the above to suggest useful guidelines for further study of bedrock channel systems and for future refinement of the streampower erosion law. Dimensional analysis reveals that the dynamic behavior of the stream‐power erosion model is governed by a single nondimensional group that we term the uplift‐erosion number, greatly reducing the number of variables that need to be considered in the sensitivity analysis. The degree of nonlinearity in the relationship between stream incision rate and channel gradient (slope exponent n ) emerges as a fundamental unknown. The physics of the active erosion processes directly influence this nonlinearity, which is shown to dictate the relationship between the uplift‐erosion number, the equilibrium stream channel gradient, and the total fluvial relief of mountain ranges. Similarly, the predicted response time to changes in rock uplift rate is shown to depend on climate, rock strength, and the magnitude of tectonic perturbation, with the slope exponent n controlling the degree of dependence on these various factors. For typical drainage basin geometries the response time is relatively insensitive to the size of the system. Work on the physics of bedrock erosion processes, their sensitivity to extreme floods, their transient responses to sudden changes in climate or uplift rate, and the scaling of local rock erosion studies to reach‐scale modeling studies are most sorely needed.

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A genetic classification of floodplains

1992-04-01

Gerald C. Nanson , Jacky Croke

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Fragmentation and Flow Regulation of the World's Large River Systems

2005-04-14

Christer Nilsson , Catherine Ann Reidy , Mats Dynesius +1 more

A global overview of dam-based impacts on large river systems shows that over half (172 out of 292) are affected by dams, including the eight most biogeographically diverse. Dam-impacted catchments … A global overview of dam-based impacts on large river systems shows that over half (172 out of 292) are affected by dams, including the eight most biogeographically diverse. Dam-impacted catchments experience higher irrigation pressure and about 25 times more economic activity per unit of water than do unaffected catchments. In view of projected changes in climate and water resource use, these findings can be used to identify ecological risks associated with further impacts on large river systems.

The Role of Riparian Corridors in Maintaining Regional Biodiversity

1993-05-01

Robert J. Naiman , Henri Décamps , Michael M. Pollock

Riparian corridors possess an unusually diverse array of species and environmental processes. This "ecological" diversity is related to variable flood regimes, geomorphic channel processes, altitudinal climate shifts, and upland influences … Riparian corridors possess an unusually diverse array of species and environmental processes. This "ecological" diversity is related to variable flood regimes, geomorphic channel processes, altitudinal climate shifts, and upland influences on the fluvial corridor. This dynamic environment results in a variety of life history strategies, and a diversity of biogeochemical cycles and rates, as organisms adapt to disturbance regimes over broad spatio-temporal scales. These facts suggest that effective riparian management could ameliorate many ecological issues related to land use and environmental quality. We contend that riparian corridors should play an essential role in water and landscape planning, in the restoration of aquatic systems, and in catalyzing institutional and societal cooperation for these efforts.

A hierarchical framework for stream habitat classification: Viewing streams in a watershed context

1986-03-01

Christopher A. Frissell , William J. Liss , Charles E. Warren +1 more

Streams in Mediterranean Climate Regions: Abiotic Influences and Biotic Responses to Predictable Seasonal Events

1999-11-01

Avital Gasith , Vincent H. Resh

▪ Abstract Streams in mediterranean-climate regions (areas surrounding the Mediterranean Sea, parts of western North America, parts of west and south Australia, southwestern South Africa and parts of central Chile) … ▪ Abstract Streams in mediterranean-climate regions (areas surrounding the Mediterranean Sea, parts of western North America, parts of west and south Australia, southwestern South Africa and parts of central Chile) are physically, chemically, and biologically shaped by sequential, predictable, seasonal events of flooding and drying over an annual cycle. Correspondingly, aquatic communities undergo a yearly cycle whereby abiotic (environmental) controls that dominate during floods are reduced when the discharge declines, which is also a time when biotic controls (e.g. predation, competition) can become important. As the dry season progresses, habitat conditions become harsher; environmental pressures may again become the more important regulators of stream populations and community structure. In contrast to the synchronous input of autumn litterfall in forested temperate streams, riparian input to mediterranean-type streams is more protracted, with fall and possibly spring peaks occurring in streams in the Northern Hemisphere and a summer peak existing in their Southern Hemisphere counterparts. We present 25 testable hypotheses that relate to the influence of the stream hydrograph on faunal richness, abundance, and diversity; species coexistence; seasonal changes in the relative importance of abiotic and biotic controls on the biotic structure; riparian inputs and the relative importance of heterotrophy compared to autotrophy; and the impact of human activities on these seasonally water-stressed streams. Population increases in mediterranean-climate regions (particularly in fertile regions) result in an intensification of the competition for water among different users; consequently, water abstraction, flow regulation, increased salinity, and pollution severely limit the ability of the streams to survive as sustainable, self-regulated systems.

Biodiversity of floodplain river ecosystems: ecotones and connectivity1

1999-01-01

J. V. Ward , Klement Tockner , F. Schiemer

A high level of spatio-temporal heterogeneity makes riverine floodplains among the most species-rich environments known. Fluvial dynamics from flooding play a major role in maintaining a diversity of lentic, lotic … A high level of spatio-temporal heterogeneity makes riverine floodplains among the most species-rich environments known. Fluvial dynamics from flooding play a major role in maintaining a diversity of lentic, lotic and semi-aquatic habitat types, each represented by a diversity of successional stages. Ecotones (transition zones between adjacent patches) and connectivity (the strength of interactions across ecotones) are structural and functional elements that result from and contribute to the spatio-temporal dynamics of riverine ecosystems. In floodplain rivers, ecotones and their adjoining patches are arrayed in hierarchical series across a range of scales. At a coarse scale of resolution, fringing floodplains are themselves complex ecotones between river channels and uplands. At finer scales, patches of various types and sizes form habitat and microhabitat diversity patterns. A broad spatio-temporal perspective, including patterns and processes across scales, is needed in order to gain insight into riverine biodiversity. We propose a hierarchical framework for examining diversity patterns in floodplain rivers. Various river management schemes disrupt the interactions that structure ecotones and alter the connectivity across transition zones. Such disruptions occur both within and between hierarchical levels, invariably leading to reductions in biodiversity. Species richness data from the connected and disconnected floodplains of the Austrian Danube illustrate this clearly. In much of the world, species-rich riverine/floodplain environments exist only as isolated fragments across the landscape. In many large rivers, these islands of biodiversity are endangered ecosystems. The fluvial dynamics that formed them have been severely altered. Without ecologically sound restoration of disturbance regimes and connectivity, these remnants of biodiversity will proceed on unidirectional trajectories toward senescence, without rejuvenation. Principles of ecosystem management are necessary to sustain biodiversity in fragmented riverine floodplains. Copyright © 1999 John Wiley & Sons, Ltd.

Drag, turbulence, and diffusion in flow through emergent vegetation

1999-02-01

Heidi Nepf

Aquatic plants convert mean kinetic energy into turbulent kinetic energy at the scale of the plant stems and branches. This energy transfer, linked to wake generation, affects vegetative drag and … Aquatic plants convert mean kinetic energy into turbulent kinetic energy at the scale of the plant stems and branches. This energy transfer, linked to wake generation, affects vegetative drag and turbulence intensity. Drawing on this physical link, a model is developed to describe the drag, turbulence and diffusion for flow through emergent vegetation which for the first time captures the relevant underlying physics, and covers the natural range of vegetation density and stem Reynolds' numbers. The model is supported by laboratory and field observations. In addition, this work extends the cylinder‐based model for vegetative resistance by including the dependence of the drag coefficient, C D , on the stem population density, and introduces the importance of mechanical diffusion in vegetated flows.

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Sediment Transport, Part I: Bed Load Transport

1984-10-01

Leo C. van Rijn

A method is presented which enables the computation of the bedload transport as the product of the saltation height, the particle velocity and the bed‐load concentration. The equations of motions … A method is presented which enables the computation of the bedload transport as the product of the saltation height, the particle velocity and the bed‐load concentration. The equations of motions for a solitary particle are solved numerically to determine the saltation height and particle velocity. Experiments with gravel particles (transported as bed load) are selected to calibrate the mathematical model using the lift coefficient as a free parameter. The model is used to compute the saltation heights and lengths for a range of flow conditions. The computational results are used to determine simple relationships for the saltation characteristics. Measured transport rates of the bed load are used to compute the sediment concentration in the bed‐load layer. A simple expression specifying the bed‐load concentration as a function of the flow and sediment conditions is proposed. A verification analysis using about 600 (alternative) data shows that about 77% of the predicted bed load‐transport rates are within 0.5 and 2 times the observed values.

Development and validation of a three-dimensional morphological model

2004-08-26

Giles Lesser , Dano Roelvink , J.A.T.M. van Kester +1 more

Disturbance, patchiness, and diversity in streams

2000-12-01

P. S. Lake

Perturbations in ecosystems consist of a sequence of 2 events: the disturbance, marked by the application of the disturbing forces, and the response shown by the biota to the damage … Perturbations in ecosystems consist of a sequence of 2 events: the disturbance, marked by the application of the disturbing forces, and the response shown by the biota to the damage inflicted by the disturbance. The disturbance must be effectively characterized, without confounding it with the response, for progress to be made in the study of the disturbance ecology of streams. A disturbance may take the form of a pulse, a press, or a ramp, and the consequent trajectory of the response may be a pulse, a press, or a ramp.Floods and droughts are the major forms of natural disturbance in flowing waters and, although the effects of floods have been relatively well studied, those of droughts have been largely neglected. Floods accentuate downstream and lateral transport links, often with damaging consequences, whereas droughts fragment the continuity of streams. Both floods and droughts destroy and generate habitat patchiness and patchiness of the biota. During recovery, there are changes in the biotic composition and spatial configuration in patches. Resistance and resilience of the biota to disturbance may be facilitated by the use of refugia. The characterization of flood refugia is much more advanced than that of drought refugia.Recovery from floods is marked by the rapid attainment of relatively constant levels of diversity at the local scale of individual patches. At the regional scale of streams and their catchments, several studies have reported negative correlations between diversity and levels of flood disturbance, whereas other studies have reported unimodal diversity–disturbance curves consistent with patterns expected of the intermediate disturbance hypothesis. Such a unimodal relationship may be generated in several ways that await testing. In flowing waters at the regional scale, disturbance may play a central role in regulating species diversity. A predicted increase in the severity and frequency of disturbances with global climate change requires a comprehensive understanding of the disturbance ecology of running waters.

Guide for selecting Manning's roughness coefficients for natural channels and flood plains

1989-01-01

George J. Arcement , Verne R. Schneider

Although much research has been done on Manning's roughness coefficient, n, for stream channels, very little has been done concerning the roughness values for densely vegetated flood plains. The n … Although much research has been done on Manning's roughness coefficient, n, for stream channels, very little has been done concerning the roughness values for densely vegetated flood plains. The n value is determined from the values of the factors that affect the roughness of channels and flood plains. In densely vegetated flood plains, the major roughness is caused by trees, vines, and brush. The n value for this type of flood plain can be determined by measuring the vegetation density of the flood plain. Photographs of flood-plain segments where n values have been verified can be used as a comparison standard to aid in assigning n values to similar flood plains.

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The Four-Dimensional Nature of Lotic Ecosystems

1989-03-01

J. V. Ward

The dynamic and hierarchical nature of lotic ecosystems may be conceptualized in a four-dimensional framework. Upstream-downstream interactions constitute the longitudinal dimension. The lateral dimension includes interactions between the channel and … The dynamic and hierarchical nature of lotic ecosystems may be conceptualized in a four-dimensional framework. Upstream-downstream interactions constitute the longitudinal dimension. The lateral dimension includes interactions between the channel and riparian/floodplain systems. Significant interactions also occur between the channel and contiguous groundwater, the vertical dimension. The fourth dimension, time, provides the temporal scale. Lotic ecosystems have developed in response to dynamic patterns and processes occurring along these four dimensions. An holistic approach that employs a spatio-temporal framework, and that perceives disturbances as forces disrupting major interactive pathways, should lead to a more complete understanding of the dynamic and hierarchical structure of natural and altered lotic ecosystems.

Biological Effects of Fine Sediment in the Lotic Environment

1997-03-01

Paul J. Wood

Sediment Transport, Part II: Suspended Load Transport

1984-11-01

Leo C. van Rijn

A method is presented which enables the computation of the suspended load as the depth‐integration of the product of the local concentration and flow velocity. The method is based on … A method is presented which enables the computation of the suspended load as the depth‐integration of the product of the local concentration and flow velocity. The method is based on the computation of the reference concentration from the bed‐load transport. Measured concentration profiles have been used for calibration. New relationships are proposed to represent the sizegradation of the bed material and the damping of the turbulence by the sediment particles. A verification analysis using about 800 data shows that about 76% of the predicted values are within 0.5 and 2 times the measured values.

The Ecology of Interfaces: Riparian Zones

1997-11-01

Robert J. Naiman , Henri Décamps

Riparian zones possess an unusually diverse array of species and environmental processes. The ecological diversity is related to variable flood regimes, geographically unique channel processes, altitudinal climate shifts, and upland … Riparian zones possess an unusually diverse array of species and environmental processes. The ecological diversity is related to variable flood regimes, geographically unique channel processes, altitudinal climate shifts, and upland influences on the fluvial corridor. The resulting dynamic environment supports a variety of life-history strategies, biogeochemical cycles and rates, and organisms adapted to disturbance regimes over broad spatial and temporal scales. Innovations in riparian zone management have been effective in ameliorating many ecological issues related to land use and environmental quality. Riparian zones play essential roles in water and landscape planning, in restoration of aquatic systems, and in catalyzing institutional and societal cooperation for these efforts.

BEDROCK RIVERS AND THE GEOMORPHOLOGY OF ACTIVE OROGENS

2004-04-21

K. X. Whipple

▪ Abstract Bedrock rivers set much of the relief structure of active orogens and dictate rates and patterns of denudation. Quantitative understanding of the role of climate-driven denudation in the … ▪ Abstract Bedrock rivers set much of the relief structure of active orogens and dictate rates and patterns of denudation. Quantitative understanding of the role of climate-driven denudation in the evolution of unglaciated orogens depends first and foremost on knowledge of fluvial erosion processes and the factors that control incision rate. The results of intense research in the past decade are reviewed here, with the aim of highlighting remaining unknowns and suggesting fruitful avenues for further research. This review considers in turn (a) the occurrence and morphology of bedrock channels and their relation to tectonic setting; (b) the physical processes of fluvial incision into rock; and (c) models of river incision, their implications, and the field and laboratory data needed to test, refine, and extend them.

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The River Continuum Concept

1980-01-01

Robin L. Vannote , G. Wayne Minshall , Kenneth W. Cummins +2 more

From headwaters to mouth, the physical variables within a river system present a continuous gradient of physical conditions. This gradient should elicit a series of responses within the constituent populations … From headwaters to mouth, the physical variables within a river system present a continuous gradient of physical conditions. This gradient should elicit a series of responses within the constituent populations resulting in a continuum of biotic adjustments and consistent patterns of loading, transport, utilization, and storage of organic matter along the length of a river. Based on the energy equilibrium theory of fluvial geomorphologists, we hypothesize that the structural and functional characteristics of stream communities are adapted to conform to the most probable position or mean state of the physical system. We reason that producer and consumer communities characteristic of a given river reach become established in harmony with the dynamic physical conditions of the channel. In natural stream systems, biological communities can be characterized as forming a temporal continuum of synchronized species replacements. This continuous replacement functions to distribute the utilization of energy inputs over time. Thus, the biological system moves towards a balance between a tendency for efficient use of energy inputs through resource partitioning (food, substrate, etc.) and an opposing tendency for a uniform rate of energy processing throughout the year. We theorize that biological communities developed in natural streams assume processing strategies involving minimum energy loss. Downstream communities are fashioned to capitalize on upstream processing inefficiencies. Both the upstream inefficiency (leakage) and the downstream adjustments seem predictable. We propose that this River Continuum Concept provides a framework for integrating predictable and observable biological features of lotic systems. Implications of the concept in the areas of structure, function, and stability of riverine ecosystems are discussed.Key words: river continuum; stream ecosystems; ecosystem structure, function; resource partitioning; ecosystem stability; community succession; river zonation; stream geomorphology

A classification of natural rivers

1994-06-01

David L. Rosgen

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Ecological responses to altered flow regimes: a literature review to inform the science and management of environmental flows

2009-09-23

N. LeRoy Poff , Julie K. H. Zimmerman

Summary 1. In an effort to develop quantitative relationships between various kinds of flow alteration and ecological responses, we reviewed 165 papers published over the last four decades, with a … Summary 1. In an effort to develop quantitative relationships between various kinds of flow alteration and ecological responses, we reviewed 165 papers published over the last four decades, with a focus on more recent papers. Our aim was to determine if general relationships could be drawn from disparate case studies in the literature that might inform environmental flows science and management. 2. For all 165 papers we characterised flow alteration in terms of magnitude, frequency, duration, timing and rate of change as reported by the individual studies. Ecological responses were characterised according to taxonomic identity (macroinvertebrates, fish, riparian vegetation) and type of response (abundance, diversity, demographic parameters). A ‘qualitative’ or narrative summary of the reported results strongly corroborated previous, less comprehensive, reviews by documenting strong and variable ecological responses to all types of flow alteration. Of the 165 papers, 152 (92%) reported decreased values for recorded ecological metrics in response to a variety of types of flow alteration, whereas 21 papers (13%) reported increased values. 3. Fifty‐five papers had information suitable for quantitative analysis of ecological response to flow alteration. Seventy per cent of these papers reported on alteration in flow magnitude, yielding a total of 65 data points suitable for analysis. The quantitative analysis provided some insight into the relative sensitivities of different ecological groups to alteration in flow magnitudes, but robust statistical relationships were not supported. Macroinvertebrates showed mixed responses to changes in flow magnitude, with abundance and diversity both increasing and decreasing in response to elevated flows and to reduced flows. Fish abundance, diversity and demographic rates consistently declined in response to both elevated and reduced flow magnitude. Riparian vegetation metrics both increased and decreased in response to reduced peak flows, with increases reflecting mostly enhanced non‐woody vegetative cover or encroachment into the stream channel. 4. Our analyses do not support the use of the existing global literature to develop general, transferable quantitative relationships between flow alteration and ecological response; however, they do support the inference that flow alteration is associated with ecological change and that the risk of ecological change increases with increasing magnitude of flow alteration. 5. New sampling programs and analyses that target sites across well‐defined gradients of flow alteration are needed to quantify ecological response and develop robust and general flow alteration–ecological response relationships. Similarly, the collection of pre‐ and post‐alteration data for new water development programs would significantly add to our basic understanding of ecological responses to flow alteration.

Mechanics of sediment transport

2000-04-01

M. Selim Yalin

PROFILE: Hungry Water: Effects of Dams and Gravel Mining on River Channels

1997-07-01

G. Mathias Kondolf

A method of sampling coarse river‐bed material

1954-12-01

M. Gordon Wolman

This determination of the size of material on the bed of a stream is based upon an analysis of the relative area covered by particles of given sizes. The method … This determination of the size of material on the bed of a stream is based upon an analysis of the relative area covered by particles of given sizes. The method is applicable to those rivers which flow on coarse material and may be waded during periods of low water. Sampling consists of measuring the intermediate axis of 100 pebbles picked from the bed of the channel on the basis of a grid system. From this sample a frequency distribution is drawn from which the desired size parameters are read. The advantages of the areal sampling procedure over bulk sampling are (1) that it is applicable to very coarse materials, and (2) that it provides a more representative sample of an entire reach of a stream.

Fluvial processes in geomorphology

1965-11-01

Luna B. Leopold , M. Gordon Wolman , J. Philip Miller

Homogenization of regional river dynamics by dams and global biodiversity implications

2007-03-13

N. LeRoy Poff , Julian D. Olden , David M. Merritt +1 more

Global biodiversity in river and riparian ecosystems is generated and maintained by geographic variation in stream processes and fluvial disturbance regimes, which largely reflect regional differences in climate and geology. … Global biodiversity in river and riparian ecosystems is generated and maintained by geographic variation in stream processes and fluvial disturbance regimes, which largely reflect regional differences in climate and geology. Extensive construction of dams by humans has greatly dampened the seasonal and interannual streamflow variability of rivers, thereby altering natural dynamics in ecologically important flows on continental to global scales. The cumulative effects of modification to regional-scale environmental templates caused by dams is largely unexplored but of critical conservation importance. Here, we use 186 long-term streamflow records on intermediate-sized rivers across the continental United States to show that dams have homogenized the flow regimes on third- through seventh-order rivers in 16 historically distinctive hydrologic regions over the course of the 20th century. This regional homogenization occurs chiefly through modification of the magnitude and timing of ecologically critical high and low flows. For 317 undammed reference rivers, no evidence for homogenization was found, despite documented changes in regional precipitation over this period. With an estimated average density of one dam every 48 km of third- through seventh-order river channel in the United States, dams arguably have a continental scale effect of homogenizing regionally distinct environmental templates, thereby creating conditions that favor the spread of cosmopolitan, nonindigenous species at the expense of locally adapted native biota. Quantitative analyses such as ours provide the basis for conservation and management actions aimed at restoring and maintaining native biodiversity and ecosystem function and resilience for regionally distinct ecosystems at continental to global scales.

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Standards for ecologically successful river restoration

2005-03-14

Margaret A. Palmer , Emily S. Bernhardt , J. David Allan +7 more

Summary Increasingly, river managers are turning from hard engineering solutions to ecologically based restoration activities in order to improve degraded waterways. River restoration projects aim to maintain or increase ecosystem … Summary Increasingly, river managers are turning from hard engineering solutions to ecologically based restoration activities in order to improve degraded waterways. River restoration projects aim to maintain or increase ecosystem goods and services while protecting downstream and coastal ecosystems. There is growing interest in applying river restoration techniques to solve environmental problems, yet little agreement exists on what constitutes a successful river restoration effort. We propose five criteria for measuring success, with emphasis on an ecological perspective. First, the design of an ecological river restoration project should be based on a specified guiding image of a more dynamic, healthy river that could exist at the site. Secondly, the river's ecological condition must be measurably improved. Thirdly, the river system must be more self‐sustaining and resilient to external perturbations so that only minimal follow‐up maintenance is needed. Fourthly, during the construction phase, no lasting harm should be inflicted on the ecosystem. Fifthly, both pre‐ and post‐assessment must be completed and data made publicly available. Determining if these five criteria have been met for a particular project requires development of an assessment protocol. We suggest standards of evaluation for each of the five criteria and provide examples of suitable indicators. Synthesis and applications . Billions of dollars are currently spent restoring streams and rivers, yet to date there are no agreed upon standards for what constitutes ecologically beneficial stream and river restoration. We propose five criteria that must be met for a river restoration project to be considered ecologically successful. It is critical that the broad restoration community, including funding agencies, practitioners and citizen restoration groups, adopt criteria for defining and assessing ecological success in restoration. Standards are needed because progress in the science and practice of river restoration has been hampered by the lack of agreed upon criteria for judging ecological success. Without well‐accepted criteria that are ultimately supported by funding and implementing agencies, there is little incentive for practitioners to assess and report restoration outcomes. Improving methods and weighing the ecological benefits of various restoration approaches require organized national‐level reporting systems.

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URBANIZATION OF AQUATIC SYSTEMS: DEGRADATION THRESHOLDS, STORMWATER DETECTION, AND THE LIMITS OF MITIGATION1

1997-10-01

Derek B. Booth , C. Rhett Jackson

ABSTRACT: Urbanization of a watershed degrades both the form and the function of the downstream aquatic system, causing changes that can occur rapidly and are very difficult to avoid or … ABSTRACT: Urbanization of a watershed degrades both the form and the function of the downstream aquatic system, causing changes that can occur rapidly and are very difficult to avoid or correct. A variety of physical data from lowland streams in western Washington displays the onset of readily observable aquatic‐system degradation at a remarkably consistent level of development, typically about ten percent effective impervious area in a watershed. Even lower levels of urban development cause significant degradation in sensitive water bodies and a reduced, but less well quantified, level of function throughout the system as a whole. Unfortunately, established methods of mitigating the downstream impacts of urban development may have only limited effectiveness. Using continuous hydrologic modeling we have evaluated detention ponds designed by conventional event methodologies, and our findings demonstrate serious deficiencies in actual pond performance when compared to their design goals. Even with best efforts at mitigation, the sheer magnitude of development activities falling below a level of regulatory concern suggests that increased resource loss will invariably accompany development of a watershed. Without a better understanding of the critical processes that lead to degradation, some downstream aquatic‐system damage is probably inevitable without limiting the extent of watershed development itself.

Floods, channel change, and the hyporheic zone

1999-02-01

Steven M. Wondzell , Frederick J. Swanson

We investigated the influence of flood‐induced channel changes on the hyporheic zone of 4th‐ and 5th‐order reaches of a mountain stream network. Preflood versus postflood comparisons were made in three … We investigated the influence of flood‐induced channel changes on the hyporheic zone of 4th‐ and 5th‐order reaches of a mountain stream network. Preflood versus postflood comparisons were made in three study reaches from well networks established before and reestablished after a major flood. Flood effects were scale dependent and varied with channel constraint and the dominant channel forming process. Large changes were observed in unconstrained stream reaches where channel incision drove large changes in subsurface flow paths and the extent of the hyporheic zone. However, subreach scale differences were apparent. In the lower portion of the studied reach, channel incision lowered the water table, leading to abandonment of secondary channels, and decreased the extent of the hyporheic zone that previously extended more than 30 m into the floodplain. In contrast, the extent of the hyporheic zone increased at the head of the studied reach where channel incision steepened head gradients through a meander bend. In another unconstrained reach, lateral channel jumps dramatically altered exchange flow paths. However, the extensive hyporheic zone was maintained throughout the reach. Less change was observed in the constrained stream reach where both the depth and area of sediment available to be reworked by the flood were limited by bedrock constraining the width of the valley floor. This flood dramatically changed the hyporheic zone at the three study sites and these physical changes are expected to be biologically important, considering the role of the hyporheic zone in stream ecosystem processes.

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An extension of the flood pulse concept

2000-01-01

Klement Tockner , Florian Malard , J. V. Ward

The flood pulse concept of Junk, Bayley and Sparks is a major contribution to our understanding of river–floodplain interactions and has become an important paradigm in lotic ecology. The concept … The flood pulse concept of Junk, Bayley and Sparks is a major contribution to our understanding of river–floodplain interactions and has become an important paradigm in lotic ecology. The concept is based mainly on large tropical lowland rivers. Floodplains may, however, develop in all geographical areas and at different locations along a river corridor. We extend this concept to temperate areas by including information derived from near-natural proglacial, headwater and lowland floodplains. Specific attention is directed to the role of temperature as a major determinant of floodplain ecology. Further attention is directed to the importance of expansion–contraction cycles occurring well below bankfull ('flow pulse' versus 'flood pulse'). Selected examples are presented that highlight the complexity of expansion–contraction events and their consequences on habitat heterogeneity and functional processes. Habitat heterogeneity is mainly a product of shifting water sources, different flow paths and the relative importance of autogenic processes. In different floodplain systems, expansion may enhance habitat heterogeneity (e.g. glacial floodplain) or create homogeneity (e.g. Danubian floodplain). Further, the ecological consequences of episodic flow and flood pulses are discussed. Finally, a landscape approach is suggested in order to document expansion and contraction processes and to elucidate how these processes influence landscape heterogeneity and biodiversity patterns. Such a landscape-based ecosystem model can be applied to rigorously assess the ecological integrity of river–floodplain systems. Copyright © 2000 John Wiley & Sons, Ltd.

Channel-reach morphology in mountain drainage basins

1997-05-01

David R. Montgomery , John M. Buffington

Research Article| May 01, 1997 Channel-reach morphology in mountain drainage basins David R. Montgomery; David R. Montgomery 1Department of Geological Sciences, University of Washington, Seattle, Washington 98195 Search for other … Research Article| May 01, 1997 Channel-reach morphology in mountain drainage basins David R. Montgomery; David R. Montgomery 1Department of Geological Sciences, University of Washington, Seattle, Washington 98195 Search for other works by this author on: GSW Google Scholar John M. Buffington John M. Buffington 1Department of Geological Sciences, University of Washington, Seattle, Washington 98195 Search for other works by this author on: GSW Google Scholar Author and Article Information David R. Montgomery 1Department of Geological Sciences, University of Washington, Seattle, Washington 98195 John M. Buffington 1Department of Geological Sciences, University of Washington, Seattle, Washington 98195 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1997) 109 (5): 596–611. https://doi.org/10.1130/0016-7606(1997)109<0596:CRMIMD>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation David R. Montgomery, John M. Buffington; Channel-reach morphology in mountain drainage basins. GSA Bulletin 1997;; 109 (5): 596–611. doi: https://doi.org/10.1130/0016-7606(1997)109<0596:CRMIMD>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract A classification of channel-reach morphology in mountain drainage basins synthesizes stream morphologies into seven distinct reach types: colluvial, bedrock, and five alluvial channel types (cascade, step pool, plane bed, pool riffle, and dune ripple). Coupling reach-level channel processes with the spatial arrangement of reach morphologies, their links to hillslope processes, and external forcing by confinement, riparian vegetation, and woody debris defines a process-based framework within which to assess channel condition and response potential in mountain drainage basins. Field investigations demonstrate characteristic slope, grain size, shear stress, and roughness ranges for different reach types, observations consistent with our hypothesis that alluvial channel morphologies reflect specific roughness configurations adjusted to the relative magnitudes of sediment supply and transport capacity. Steep alluvial channels (cascade and step pool) have high ratios of transport capacity to sediment supply and are resilient to changes in discharge and sediment supply, whereas low-gradient alluvial channels (pool riffle and dune ripple) have lower transport capacity to supply ratios and thus exhibit significant and prolonged response to changes in sediment supply and discharge. General differences in the ratio of transport capacity to supply between channel types allow aggregation of reaches into source, transport, and response segments, the spatial distribution of which provides a watershed-level conceptual model linking reach morphology and channel processes. These two scales of channel network classification define a framework within which to investigate spatial and temporal patterns of channel response in mountain drainage basins. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Tectonics from topography: Procedures, promise, and pitfalls

2006-01-01

Cameron Wobus , K. X. Whipple , Eric Kirby +5 more

Empirical observations from fluvial systems across the globe reveal a consistent power-law scaling between channel slope and contributing drainage area. Theoretical arguments for both detachment- and transport-limited erosion regimes suggest … Empirical observations from fluvial systems across the globe reveal a consistent power-law scaling between channel slope and contributing drainage area. Theoretical arguments for both detachment- and transport-limited erosion regimes suggest that rock uplift rate should exert first-order control on this scaling. Here we describe in detail a method for exploiting this relationship, in which topographic indices of longitudinal profile shape and character are derived from digital topographic data. The stream profile data can then be used to delineate breaks in scaling that may be associated with tectonic boundaries. The description of the method is followed by three case studies from...

Open channel hydraulics

1960-07-01

William C. Yager

Rivers and floodplains: forms, processes, and sedimentary record

2003-11-01

1. Introduction. 2. Overview of River Systems. 3. Fundamentals of Water Flow. 4. Fundamentals of Sediment Transport. 5. Bed forms and Sedimentary Structures. 6. Alluvial Channels and Bars. 7. Floodplains. … 1. Introduction. 2. Overview of River Systems. 3. Fundamentals of Water Flow. 4. Fundamentals of Sediment Transport. 5. Bed forms and Sedimentary Structures. 6. Alluvial Channels and Bars. 7. Floodplains. 8. Along--valley Variations in Channels and Floodplains. 9. Channel--belt movements across floodplains. 10. Long--term, Large--scale Evolution of Fluvial Systems. 11. Fossils in Fluvial Deposits. Appendix 1. Methods of Measuring Bed Topography, Water flow, Sediment Transport, Erosion and Deposition in Rivers. Appendix 2. Methods of Describing and Interpreting Sedimentary Strata. References

Riparia: ecology, conservation, and management of streamside communities

2006-06-01

Robert J. Naiman , Henri Décamps , Michael E. McClain

Foreword Preface 1. Introduction 2. Catchments and the Physical Template 3. Riparian Typology 4. Structural Patterns 5. Biotic Functions of Riparia 6. Biophysical Connectivity and Riparian Functions 7. Disturbance and … Foreword Preface 1. Introduction 2. Catchments and the Physical Template 3. Riparian Typology 4. Structural Patterns 5. Biotic Functions of Riparia 6. Biophysical Connectivity and Riparian Functions 7. Disturbance and Agents of Change 8. Management 9. Conservation 10. Restoration 11. Synthesis Bibliography Index

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An Ecosystem Perspective of Riparian Zones

1991-09-01

Stanley V. Gregory , Frederick J. Swanson , W. Arthur McKee +1 more

Journal Article An Ecosystem Perspective of Riparian Zones: Focus on links between land and water Get access Stanley V. Gregory, Stanley V. Gregory Search for other works by this author … Journal Article An Ecosystem Perspective of Riparian Zones: Focus on links between land and water Get access Stanley V. Gregory, Stanley V. Gregory Search for other works by this author on: Oxford Academic Google Scholar Frederick J. Swanson, Frederick J. Swanson Search for other works by this author on: Oxford Academic Google Scholar W. Arthur McKee, W. Arthur McKee Search for other works by this author on: Oxford Academic Google Scholar Kenneth W. Cummins Kenneth W. Cummins Search for other works by this author on: Oxford Academic Google Scholar BioScience, Volume 41, Issue 8, September 1991, Pages 540–551, https://doi.org/10.2307/1311607 Published: 01 September 1991

Can changes in geomorphic responses to urbanisation be predicted from stormwater outfalls?

2025-06-25

Lukman A. Soboyejo , Kathryn Russell , Tim D. Fletcher | Earth Surface Processes and Landforms

Abstract Stormwater drainage is a primary pathway through which urbanisation degrades physical channel form and ecologically relevant in‐stream attributes, such as the presence of large wood. However, there is a … Abstract Stormwater drainage is a primary pathway through which urbanisation degrades physical channel form and ecologically relevant in‐stream attributes, such as the presence of large wood. However, there is a gap in the literature regarding methods or study designs that effectively isolate the specific effect of stormwater from those of catchment context, geology and other geomorphic controls. This study examines how stream geomorphology, characterised through variables such as bankfull cross‐sectional area, pool‐to‐riffle spacing and large wood, relates to stormwater drainage inputs from urban areas. To achieve this, we employed historical data reviews, GIS techniques and field observations to assess morphological changes along a stream channel (Toomuc Creek, Melbourne, Australia), focusing on the differences between upstream and downstream of stormwater inputs. We hypothesised that: (i) stream bankfull cross‐sectional area increases with catchment urbanisation and (ii) significant differences in geomorphic response variables exist between upstream and downstream of stormwater outfalls. However, contrary to our expectations, stream bankfull cross‐sectional area did not follow a systematic downstream increase with catchment urbanisation, largely due to historical land‐use practices (e.g. vegetation clearing) and channel stabilisation interventions (e.g. grade control structures, rock lining). Nonetheless, some outfall locations did show clear evidence of disturbance, confirming that widening, deepening and a combination of both occur locally and in a spatially discontinuous manner. These findings highlight two key directions for future research. Firstly, to properly isolate urban influences on stream geomorphic adjustments, controlled study designs should prioritise sites with minimal historical disturbance and no hardpoint interventions. Secondly, and perhaps more importantly, the influence of past channel corridor management and channel evolution on contemporary geomorphic responses needs to be specifically studied in urban settings. Understanding the complex interplay between urbanisation, channel geomorphology, historical land‐use and in‐stream features is vital for developing more accurate predictive models to mitigate urban stormwater impacts.

Deciphering bed-load characteristics of the fluvially dynamic Balason River in Darjeeling of the Sub-Himalayan foreland, India

2025-06-24

Mantu Das , Kunal Chakraborty , S. Abdul Rahaman +2 more | Journal of Sedimentary Environments

Ice Ice Maybe: Stream Hydrology and Hydraulic Processes During a Mild Winter in a Semi-Alluvial Channel

2025-06-24

Christopher Giovino , Jaclyn Cockburn , Paul V. Villard | Water

Warm conditions during typically cold winters impact runoff and resulting hydraulic processes in channels where ice-cover would typically dominate. This field study on a short, low-slope reach in Southern Ontario, … Warm conditions during typically cold winters impact runoff and resulting hydraulic processes in channels where ice-cover would typically dominate. This field study on a short, low-slope reach in Southern Ontario, Canada, examined hydrologic and hydraulic processes with a focus on winter runoff events and subsequent bed shear stress variability. Through winter 2024, six cross-sections over a ~100 m reach were monitored near-weekly to measure hydraulic geometry and velocity profiles. These data characterized channel processes and estimated bed shear stress with law of the wall. In this channel, velocity increased more rapidly than width or depth with rising discharge and influenced bed shear stress distribution. Bed shear stress magnitudes were highest (means ranged ~2–6 N/m2) and most variable over gravel beds compared to the exposed bedrock (means ranged ~0.05–2 N/m2). Through a rain-on-snow (ROS) event in late January, bed shear stress estimates decreased dramatically over the rougher gravel bed, despite minimal changes in water depth and velocity. Pebble counts before, during, and after the event, showed that the proportion of finer-sized particles (i.e., <5 cm) increased while median grain size did not vary. These observations align with findings from both flume and field studies and suggest that milder winters reduce gravel-bed roughness through finer-sized sediment deposition, altering sediment transport dynamics and affecting gravel habitat suitability. Additionally, limited ice-cover leads to lower bed shear stresses and thus finer-sized materials are deposited, further impacting gravel habitat suitability. Results highlight the importance of winter hydrologic variability in shaping channel processes and inform potential stream responses under future climate scenarios.

Potential and constraints of uncrewed aerial vehicle orthoimagery for rivers: A direct comparison with field measurements for mapping boulders

2025-06-23

Christopher Wård , R. Mason , Ricardo Carrillo +1 more | Earth Surface Processes and Landforms

Abstract Technological advances continue to improve our ability to detect landforms and landscape changes. Remote sensing can provide geomorphological information at larger scales than previously possible but interpreting this information … Abstract Technological advances continue to improve our ability to detect landforms and landscape changes. Remote sensing can provide geomorphological information at larger scales than previously possible but interpreting this information can be more challenging than for field data. Measuring and mapping roughness elements, such as boulders and large wood, is essential for understanding geomorphic processes and restoration in many landscapes where these are abundant. Mapping roughness elements from aerial orthoimagery is common but could produce different results than field measurements due to the 2D nature of the imagery and the variable ability to detect boulders through water and vegetation. We compared measurements of river boulders from aerial imagery collected by uncrewed aerial vehicles (UAVs) to direct measurements in the field. We surveyed boulder size, density and spatial distributions using both approaches at eight river reaches in northern Sweden. We found that the density, coverage and size of boulders mapped from UAVs were strongly correlated with those from field measurements, giving confidence in UAV methods. However, the UAV approach consistently resulted in fewer boulders (30% lower density), lower boulder coverage and smaller boulders (7% smaller mean b‐axis) compared to field measurements. The difference between field and UAV measurements was strongly associated with river bankfull depth. Therefore, we conclude that UAV measurements should be restricted to sites with low depth or high visibility through the water column and where bias in boulder detection with depth is not likely to influence study conclusions. In reaches with many boulders, overlap of boulders also likely reduces the suitability of aerial imagery. We conclude that aerial imagery has high potential for mapping landforms in rivers but is not directly equivalent to field studies and the implications of hiding by water, sediment and vegetation need to be considered.

Catchment‐Scale Eucalyptus Plantation Effects on Tropical Streams

2025-06-23

Alessandra Peil , Guilherme Sena , Raiane S. Rabelo +4 more | International Review of Hydrobiology

ABSTRACT Forestry plantations occur across the globe, and they are important in many tropical countries for timber supply. Plantations of non‐native species, such as those of Eucalyptus species, may greatly … ABSTRACT Forestry plantations occur across the globe, and they are important in many tropical countries for timber supply. Plantations of non‐native species, such as those of Eucalyptus species, may greatly affect the functioning of detritus‐based ecosystems. However, despite eucalyptus plantations covering about 20 million hectares in tropical and subtropical regions (from a total of about 25 million hectares globally), there is scarce information about their effects on forest stream functioning. Our aim was to assess the effects of catchment‐scale eucalyptus plantations (with native riparian buffers) on the functioning of tropical streams in the Cerrado biome. For that, three streams in catchments with eucalyptus plantations (eucalyptus streams) and three streams in catchments with native vegetation (native streams) were compared regarding water characteristics, litter inputs (vertical and lateral), decomposition of leaf litter (from a common native species, an eucalyptus species used in plantations, and a palatable exotic species) and litter‐associated aquatic communities. We hypothesized that catchment‐scale Eucalyptus plantations negatively affect stream characteristics (reduced water flow, heightened water acidity), litter inputs, aquatic communities, and litter decomposition in streams because dense, even‐aged monocultures of eucalyptus trees have higher water consumption rates and produce recalcitrant litter. We also hypothesized that the effects of plantations would be stronger on shredders, as they are directly influenced by changes in litter input compared to other functional feeding groups. Finally, we hypothesized that plantation impacts on leaf litter decomposition would be stronger for palatable leaf litter, where invertebrate shredders play a major role, than for more recalcitrant and less palatable leaf litter. We found lower dissolved oxygen concentrations, lateral litter inputs, and litter decomposition in eucalyptus streams than in native streams. Conversely, fungal biomass on decomposing litter did not differ between eucalyptus streams and native streams. Eucalyptus plantations reduced overall invertebrate densities but did not affect shredder densities. Our study shows that catchment‐scale eucalyptus plantations can change water characteristics and litter inputs to streams, thus slowing down litter decomposition in tropical streams, even when a native buffer is present. Increasing the width of the native buffer vegetation may contribute to increasing its protective role.

Hillslope grain size variation across evolving landscapes linked to climate, tectonics and lithology

2025-06-22

Tingan Li , L. S. Sklar , N. M. Gasparini | Earth Surface Processes and Landforms

Abstract The grain size of bedload sediment regulates rates of river incision into bedrock and thus influences topographic response to temporal and spatial variations in climate, tectonics and lithology. Grain … Abstract The grain size of bedload sediment regulates rates of river incision into bedrock and thus influences topographic response to temporal and spatial variations in climate, tectonics and lithology. Grain size in river networks, in turn, depends on the size distributions of rock particles produced by weathering on hillslopes, which vary with local climate, erosion rate and rock properties. Hence, understanding the evolution of erosional landscapes requires consideration of the role of grain size as both a driver and a response to topographic change. However, conventional landscape evolution models do not explicitly account for the role of grain size, in part because algorithms for predicting hillslope grain size have been lacking. Here, we couple a recently proposed model for grain size production on hillslopes with a conventional landscape evolution model, to explore the controls on grain size at the landscape scale. We conducted a series of numerical experiments, varying rock uplift rate, temperature, precipitation and rock properties, to evolve a suite of steady‐state and transient landscapes. Model simulations suggest that rock uplift rate, through its effect on erosion rate and hillslope residence time, is more influential than climate in controlling the variation in hillslope grain size distributions in tectonically active landscapes. Overall, coarser size distributions result from faster rates of uplift, as well as from colder and drier conditions, and lithologies with lower erodibility and weathering susceptibility. These results are broadly consistent with patterns of hillslope grain size variation reported in field studies but likely underpredict the potential magnitude of variation because of the limitations of the model linking grain size and hillslope weathering. This work is a first step toward incorporating grain‐sized explicit algorithms for bedrock incision into landscape evolution models to capture the potential for feedback among grain size, climate, tectonics and lithology in evolving landscapes.

Experimental Investigation of the Effects of Backwater on the Velocity Distribution Characteristics in a 90-Degree Curved Channel

2025-06-22

Qihang Zhou , Zhijing Li , Zhongwu Jin +4 more | Water

The impacts of backwater due to large dam construction on flow may lead to navigation or flood control problems in curved rivers. This study conducted flume experiments to investigate the … The impacts of backwater due to large dam construction on flow may lead to navigation or flood control problems in curved rivers. This study conducted flume experiments to investigate the effects of backwater on the velocity distribution characteristics of a 90-degree bend. The experimental results show that the backwater degree (η, defined as the ratio of flow depth under backwater to that under non-backwater conditions) has significant impacts on the three-dimensional velocity distribution in the bend. The depth-averaged velocities decrease with increasing backwater degree, and the deflection degrees of depth-averaged velocities are found to be highly related to the backwater degree and cross-sectional position. In this experimental setup, the mean cross-sectional velocity decreases by 67.2% as η increases from 1.00 to 3.64 for Q = 35 L/s; 63.7% as η increases from 1.00 to 3.26 for Q = 52 L/s; and 60.1% as η increases from 1.00 to 2.80 for Q = 52 L/s. The maximum values of transversal and vertical velocities near the riverbed gradually shift to the inner bank as the backwater degree increases at the 45° cross section. The center of the high transversal velocity area shifts about 0.1 m toward the inner bank as the backwater degree increases from 1.00 to 3.26 for Q = 52 L/s, which can reduce the erosion of the riverbed near the outer bank. In the current study, we also demonstrate that the growth and decay processes of secondary flow cells under backwater conditions are similar to those under non-backwater conditions. However, the scales and positions of the secondary flow cells change continuously with different backwater degrees. From the entrance to the exit of the bend, the secondary flow intensity first increases, and then decreases, with its maximum values occurring at the 45° cross section. The findings detailed in this manuscript provide insights for navigation channel design in reservoir backwater zones.

Modifying of turbulent kinetic energy constants: a comparison among shear stress methods in compound meandering channels

2025-06-21

Vahideh Mortazavi Amiri , Kazem Esmaili | Environmental Earth Sciences

Effects of vortex flows induced by four obstacles on swimming behaviors of juvenile Onychostoma sima

2025-06-20

Xinjie Zheng , Weiwei Yu , Chenyang Cao +7 more | Journal of Ecohydraulics

Remote Sensing and GIS-Based Assessment of Riverbank Erosion, Deposition, and Channel Migration: A Case Study in Tarim River’s Xinqiman–Kelelik Mainstem

2025-06-20

Ze Li , Lin Li , Jing Liu | Applied Sciences

To investigate the erosion and deposition evolution characteristics of the Xinqiman–Kelelik reach along the main stem of the Tarim River, this study analyzed river channel dynamics and planform morphological changes … To investigate the erosion and deposition evolution characteristics of the Xinqiman–Kelelik reach along the main stem of the Tarim River, this study analyzed river channel dynamics and planform morphological changes using Landsat satellite imagery (1993–2024) and hydrological data (water discharge and sediment load) from gauge stations. The results show that the thalweg line swings indefinitely in the river. The thalweg length increased by 29 km, while the mean channel width decreased by 0.28 km. The sinuosity index rose from 1.95 to 2.34, indicating a gradual intensification of channel curvature. The north bank is in a state of siltation, while the south bank is in a state of erosion. The riverbank exhibited an overall southward migration. The farmland area in the study area increased from 1510 hectares in 1993 to 5140 hectares in 2024. During this period, the thalweg near the water-diversion sluice continuously shifted toward the sluice side. To ensure flood protection safety for farmlands and villages on both banks, as well as ecological water diversion, river channel regulation and channel pattern control should be implemented.

Beyond historical records: Palaeoflood insights for improved flood hazard assessment in the lower Mahi River Basin, western India

2025-06-20

Alpa Sridhar , D. M. Maurya , L. S. Chamyal | Research Square (Research Square)

<title>Abstract</title> Understanding long-term flood variability is crucial for effective flood disaster management, yet systematic gauge data are often limited. Palaeoflood hydrology offers valuable insights using geological and geomorphological archives contributing … <title>Abstract</title> Understanding long-term flood variability is crucial for effective flood disaster management, yet systematic gauge data are often limited. Palaeoflood hydrology offers valuable insights using geological and geomorphological archives contributing to better flood risk analysis and infrastructure design. While bedrock reaches have been the focus of many palaeoflood studies, this paper synthesizes the late Holocene palaeoflood record from five sites within the alluvial lower Mahi River Basin in western India, highlighting the role of distinct geomorphic settings in slackwater deposit (SWD) accumulation and preservation. Our synthesis of optically stimulated luminescence and radiocarbon dated SWDs from ravine incisions, tributary confluences, and pediment benches reveals evidence of significant palaeoflood events occurring at approximately 4.6, 1.7, 1.25, 0.73, 0.51, and 0.28 ka. Notably, deeply incised ravines at meander bends in the lower reaches provided ideal backflooding conditions, leading to the accumulation and better preservation of thicker and chronologically longer SWD sequences compared to the more proximal flood benches in the upper reaches. Palaeoflood discharge estimations at select sites indicate past flood magnitudes significantly exceeding historical records. This study underscores the potential of specific alluvial geomorphic settings in monsoon-fed rivers for reconstructing late Holocene palaeoflood histories in regions with limited long-term hydrological data, offering crucial insights for improved flood risk assessment and understanding flood-climate relationships in western India.

Inviscid Flows

2025-06-19

| Cambridge University Press eBooks

Grazing control and revegetation increases bird biodiversity at farm dams

2025-06-19

David Smith , Maldwyn J. Evans , Ben C. Scheele +7 more | Biological Conservation

Case Studies on the Use of LIDAR Data for Hydraulic Modeling of Upstream Fish Passage

2025-06-19

Mark Gard , W. R. Cowan , Lucy M. Richardson +2 more | River Research and Applications

ABSTRACT The evaluation of fish passage in shallow‐braided rivers is difficult due to flashy flows and changing bed topography. In such systems, timing of data collection at specific flows suitable … ABSTRACT The evaluation of fish passage in shallow‐braided rivers is difficult due to flashy flows and changing bed topography. In such systems, timing of data collection at specific flows suitable for migration are not feasible due to safety and/or logistics of not being able to sample a sufficient number of potentially critical riffles and changes to the channel between sampling events. Hydraulic modeling using high resolution LIDAR data is a robust way to address these challenges. LIDAR data, supplemented by survey‐grade real time kinematic global positioning system and total station data, was used as the basis for the topography for a two‐dimensional HEC‐RAS model of upstream passage of adult steelhead ( Oncorhynchus mykiss ) on the Ventura River, Ventura County, California, USA. For the Santa Clara River, Ventura County, California, USA, LIDAR data was the sole basis for the topography for 3 two‐dimensional HEC‐RAS models of upstream passage of adult steelhead, since the entire channel was dry when the LIDAR data was collected. The results of the HEC‐RAS models were used to identify flow levels that met the minimum depth and width thresholds needed for adult steelhead to migrate upstream through the study reach on each stream. A minimum passage depth criterion of 0.21 m was used for adult steelhead. The results of the predictive modeling will be used by the California Department of Fish and Wildlife to identify flow criteria that protect migrating upstream steelhead.

Incorporating blockage effect of flexible woody vegetation patches in flow resistance analyses

2025-06-19

Hafiza Aisha Khalid , Kaisa Västilä , Juha Järvelä | Acta Geophysica

Local Scour Around Marine Structures: A Comprehensive Review of Influencing Factors, Prediction Methods, and Future Directions

2025-06-19

Bingchuan Duan , Duoyin Wang , Chenxi Qin +1 more | Buildings

Local scour is a phenomenon of sediment erosion and transport caused by the dynamic interaction between water flow and seabed sediment, posing a serious threat to the safety of marine … Local scour is a phenomenon of sediment erosion and transport caused by the dynamic interaction between water flow and seabed sediment, posing a serious threat to the safety of marine engineering structures such as cross-sea bridges and offshore wind turbines. To improve scour prediction and prevention capabilities, this review systematically analyzes the influence mechanisms of factors such as hydrodynamic conditions, sediment characteristics, and structural geometry, and discusses scour protection measures. Based on this, a comprehensive evaluation of the applicability of different prediction methods, including traditional empirical formulas, numerical simulations, probabilistic prediction models, and machine learning (ML) methods, was conducted. The study focuses on analyzing the limitations of existing methods: empirical formulas lack adaptability under complex field conditions, numerical simulation still faces challenges in validating real marine environments, and data-driven models suffer from “black box” issues and insufficient generalization capabilities. Based on the current research progress, this review presents prospects for future development, emphasizing the need to deepen the study of scouring mechanisms in complex real marine environments, develop efficient numerical models for engineering applications, and explore intelligent prediction methods that integrate data-driven approaches with physical mechanisms. This aims to provide more reliable theoretical support for the safe design, risk prevention, and scouring mitigation measures in marine engineering.

3-D numerical study on the influence of orifice arrangement on sediment transport upstream of a dam

2025-06-19

Zhuo Cheng , Xinhua Lu , Rui Wang | Journal of Hydrodynamics

Investigation of aquatic vegetation evolution in rivers based on a two-dimensional hydrodynamic model

2025-06-18

Jianyu Zhang , X. Y. Zhang , Wen Wang +6 more | Journal of Environmental Management

Influence of Aquatic Vegetation on Velocity Distribution, Water Surface Profile, and Energy Loss: An Experimental Study in an Open Channel

2025-06-17

Mohamed Galal Elbagoury , Roland Weiß , Eva Panulinová +2 more | Water

Aquatic vegetation can influence hydraulic performance in channels, rivers, and floodplains. Most previous studies used cylindrical stems to simulate vegetation, while few studies used shrub-like or sedge structures that exhibited … Aquatic vegetation can influence hydraulic performance in channels, rivers, and floodplains. Most previous studies used cylindrical stems to simulate vegetation, while few studies used shrub-like or sedge structures that exhibited a maximum width near the top of the vegetation. In contrast, this research focuses on shrub-like structures that show a maximum width near the bottom of the vegetation. To understand the effects of aquatic vegetation on velocity distribution, water surface profile, and energy loss, experiments have been conducted in an open channel with a rectangular cross-section. The results indicated that the streamwise velocity within the lower layer remains nearly constant with depth where z/y is less than 0.20. However, once z/y exceeds 0.20, the streamwise velocity increases rapidly as the depth increases toward the water surface. Additionally, the shape of the vegetation influences the position of the inflection point. Moreover, the water level rises upstream of the vegetated area, decreases within it, and gradually returns to the normal depth downstream. The bed slope has little effect on relative energy loss, with maximum values reaching 6.61%, while the presence of vegetation leads to a significant increase, reaching up to 22.51%. The relative energy loss increases with a higher submerged ratio. A new empirical equation is proposed to estimate the relative energy loss in vegetated channels.

Experimental investigation on local scour around a cubic artificial reef in bidirectional tidal currents

2025-06-17

Linlin Wang , Mingda Yang , Muk Chen Ong +3 more | Ocean Engineering

Enhancing bed load prediction accuracy through advanced multi-parameter analysis: a new temperature-sensitive approach validated across 783 river measurements

2025-06-17

Jafar Chabokpour | Stochastic Environmental Research and Risk Assessment

Stability Diagrams of Bed Evolution for Vertically Averaged and Moment (VAM) Models

2025-06-17

Mohamed Elgamal , Mohd Aamir Mumtaz | Mathematics

This study presents, for the first time, a detailed linear stability analysis (LSA) of bedform evolution under low-flow conditions using a one-dimensional vertically averaged and moment (1D-VAM) approach. The analysis … This study presents, for the first time, a detailed linear stability analysis (LSA) of bedform evolution under low-flow conditions using a one-dimensional vertically averaged and moment (1D-VAM) approach. The analysis focuses exclusively on bedload transport. The classical Saint-Venant shallow water equations are extended to incorporate non-hydrostatic pressure terms and a modified moment-based Chézy resistance formulation is adopted that links bed shear stress to both the depth-averaged velocity and its first moment (near-bed velocity). Applying a small-amplitude perturbation analysis to an initially flat bed, while neglecting suspended load and bed slope effects, reveals two distinct modes of morphological instability under low-Froude-number conditions. The first mode, associated with ripple formation, features short wavelengths independent of flow depth, following the relation F2 = 1/(kh), and varies systematically with both the Froude and Shields numbers. The second mode corresponds to dune formation, emerging within a dimensionless wavenumber range of 0.17 to 0.9 as roughness increases and the dimensionless Chézy coefficient C∗ decreases from 20 to 10. The resulting predictions of the dominant wavenumbers agree well with recent experimental observations. Critically, the model naturally produces a phase lag between sediment transport and bedform geometry without empirical lag terms. The 1D-VAM framework with Exner equation offers a physically consistent and computationally efficient tool for predicting bedform instabilities in erodible channels. This study advances the capability of conventional depth-averaged models to simulate complex bedform evolution processes.

Where should we revegetate? Insights from comparing the impacts of natural and artificial vegetation on hydrological processes in the Yellow River Basin

2025-06-16

Jinkai Luan , Ning Ma , Jiefeng Wu +1 more | Environmental Research Letters

Abstract It is widely acknowledged that vegetation change can exert considerable influences on the hydrological processes. Vegetation change can be either natural or artificial. However, the specific effects of natural … Abstract It is widely acknowledged that vegetation change can exert considerable influences on the hydrological processes. Vegetation change can be either natural or artificial. However, the specific effects of natural growth (NG) and artificial restoration (AR) of vegetation on surface hydrology remain unclear. Using a recently developed ecohydrological model, we demonstrate that NG and AR have contrasting spatial impacts on hydrological components across China’s Yellow River Basin, a hotspot with intensive human-driven revegetation over the recent decades. Our analysis identifies a critical annual precipitation threshold of 300 mm, below which both NG and AR have marginal hydrological impact. In regions where precipitation exceeds this threshold, NG significantly reduces evapotranspiration and increases runoff, while AR has the opposite effects. These results suggest that NG is a more sustainable strategy in areas receiving less than 300 mm of annual precipitation, while AR may be appropriate for regions with precipitation higher than this threshold. Our findings offer valuable guidance for policymakers in designing sustainable revegetation strategies tailored to local environmental conditions.

Calibration of a 2D Hydraulic Model for Flow Discharge Prediction in Multi-Stage Compound Channels

2025-06-16

Ali Jamali , Babak Aminnejad , Abdolreza Zahiri | Iranian Journal of Science and Technology Transactions of Civil Engineering

Local scour and hydrodynamics around river crossing pipelines under ice-covered flow conditions

2025-06-15

Guowei Li , Jueyi Sui , Maurício Dziedzic | Ocean Engineering

Morphological and Sediment Supply Controls on Lateral Bedrock Channel Erosion

2025-06-14

Takuya INOUE , Yuki Hiramatsu , J. P. Johnson | Geophysical Research Letters

Abstract In bedrock rivers, bedload transport causes abrasion not only vertically but also laterally. Bank erosion causes sinuosity changes and lateral migration that influence terrace formation, hillslope base level and … Abstract In bedrock rivers, bedload transport causes abrasion not only vertically but also laterally. Bank erosion causes sinuosity changes and lateral migration that influence terrace formation, hillslope base level and drainage divide evolution. We conducted laboratory experiments and developed equations to predict lateral bedrock abrasion rates, which are poorly understood compared to vertical incision rates. We systematically varied channel curvature, lateral (cross‐stream) bed slope, and the supply rate of bedload. Surprisingly, bank abrasion decreases with increasing channel curvature due to secondary circulation. Bank erosion increases with lateral bed slope because it increases sidewall sediment concentration. However, at higher sediment supply rates lateral erosion is ≈constant due to particle interactions and dynamic cover effects. We propose equations which capture the sensitivity of bank erosion rate to the experimental variables. Our model will be useful for predicting future lateral erosion and for constraining bedload transport rates from bedrock channel morphology.

A critical review of bridge scour monitoring methods

2025-06-14

Yu Tang , Zhenling Wu , Lesley H. Sneed | Journal of Civil Structural Health Monitoring

Numerical Simulation of Discontinuously Vegetated Open Channel Flow to Estimate Effects of Vegetation Condition on Flood Mitigation

2025-06-13

Nadim Ahmed , Zavid Iqbal Bangalee | Journal of Hydraulic Engineering

Experimental investigation of deltoid structures for improved sediment deposition

2025-06-13

Rahul Barman , Bipul Kumar Talukdar | ISH Journal of Hydraulic Engineering

RiverBedDynamics v1.0: a Landlab component for computing two-dimensional sediment transport and river bed evolution

2025-06-13

Angel Monsalve , Samuel Anderson , N. M. Gasparini +1 more | Geoscientific model development

Abstract. Computational landscape evolution models (LEMs) typically comprise at least two interacting components: a flow hydraulic solver that routes water across a landscape and a fluvial geomorphological model that modifies … Abstract. Computational landscape evolution models (LEMs) typically comprise at least two interacting components: a flow hydraulic solver that routes water across a landscape and a fluvial geomorphological model that modifies terrain properties, primarily bed surface elevation. LEMs used in long-term simulations over large watersheds, including some available in the Landlab library, often assume that only erosive processes occur in rivers and that terrain elevation increases solely due to tectonic uplift. Consequently, these models cannot capture the dynamics of gravel-bedded rivers, lacking the capacity to include sediment mixtures, simulate sediment deposition, and track textural changes in substrate stratigraphy that result from varying flow characteristics. To address this limitation, we developed, implemented, and tested RiverBedDynamics, a new Landlab component that simulates the evolution of bed surface elevation and grain size distribution in 2D grids based on the Exner equation for sediment mass balance. By dynamically coupling RiverBedDynamics with Landlab's hydrodynamic flow solver, OverlandFlow, we created a new LEM capable of simulating the dynamics of local shear stresses, bed load transport rates, and grain size distributions. Comparisons of our LEM results with analytical and previously reported solutions demonstrate its ability to accurately predict time-varying local changes in bed surface elevation, including erosion and deposition, as well as grain size distribution. Furthermore, application of our LEM to a synthetic watershed illustrates how spatially variable rainfall intensity leads to varying discharge patterns, which in turn drive changes in bed elevation and grain size distribution across the domain. This approach provides a more comprehensive representation of the complex interactions between flow dynamics and sediment transport in gravel-bedded rivers at timescales ranging from individual flood events to yearly morphological changes, enhancing our ability to model landscape evolution across diverse geomorphic settings.

Bed Load Transport in Channels with Vegetated Banks

2025-06-12

Farhad Jalilian , Esmaeil Dodangeh , Hossein Afzalimehr +2 more | Water

Estimating bed load in rivers is a critical aspect of river engineering. Numerous methods have been developed to quantify bed load transport, often yielding varying results depending on the bed … Estimating bed load in rivers is a critical aspect of river engineering. Numerous methods have been developed to quantify bed load transport, often yielding varying results depending on the bed surface texture and grain size. This study aims to investigate how vegetation on channel banks and bed material particle size influence bed load transport, bed shear stress, velocity distribution, and the Shields parameter. It also examines the impact of geometric changes in the channel cross-section on bed load transport capacity. To address these objectives, a novel simulation method was developed to analyze the effects of vegetated banks, bed material size, and channel geometry. Field investigations were carried out in two reaches of the Taleghan River in Iran—one with vegetated banks and one without. Complementary flume experiments were conducted at two scales, incorporating vegetation on the sidewalls. Results showed that Shields parameter distribution corresponded with bed load distribution across cross-sections. Increase in flow rate and the Shields parameter led to higher bedload transport rates. Near vegetated banks, flow velocity, shear stress, and bedload transport were significantly reduced, with velocity profiles showing distinct variations compared to non-vegetated sections.

The geomorphological and sedimentological legacy of the historical Lake Lorsch within the Weschnitz floodplain (northeastern Upper Rhine Graben, Germany)

2025-06-12

Felix Henselowsky , Peter Fischer , Elena Appel +7 more | EarthArXiv (California Digital Library)

The artificial historical Lake Lorsch (1474/79 to 1718/20 CE) in the northeastern Upper Rhine Graben (Germany) is known from various historical sources, e.g. for fish farming, as a significant anthropogenic … The artificial historical Lake Lorsch (1474/79 to 1718/20 CE) in the northeastern Upper Rhine Graben (Germany) is known from various historical sources, e.g. for fish farming, as a significant anthropogenic imprint of the Weschnitz floodplain. Nevertheless, there have been no geomorphological and sedimentological investigations about the (quasi-)natural context for the creation of the lake, its importance as a potential sediment archive and the subsequent use of the lake area until modern times. No relics of the lake can be observed in today's landscape. We investigated the geomorphological setting of the area using a high-resolution digital elevation model, groundwater level data, geophysical prospection, as well as sedimentological information from four sediment cores. This allows us to determine that the location of the lake is geomorphometrically deeper in relation to its receiving waters of the Old Weschnitz and was strongly fed by groundwater. Sedimentary analysis (core LOR 21A, unit 2) exhibits lake deposit, with characteristics indicative for a limnic environment and a high groundwater table. At the same time, adjacent stratigraphy shows drainage channel deposits (core LOR 20A, unit 3), which reflects anthropogenic controlled inflow via a channel (Renngraben). Our results based on a relative elevation model fit well with the historical records, that inflow for the anthropogenic channel was via the Old Weschnitz (topographically higher than the lake area) and that the artificial Landgraben-canal (topographical lower than the lake area) was overflowed with a bridge. It is a good example of how humans started as fluvial and water related agents at least for 500 years in the Weschnitz floodplain.

Restoring Lakeshore Vegetation in the Face of Hysteresis: A Water-Level and Sediment-Based Strategy for Shallow Lakes

2025-06-12

Yasufumi Fujimoto , Yusuke Takahashi , Hiroki Hayami +4 more | Water

Long-term sedimentation patterns influence the ecological succession of shallow lakes. However, human-induced impacts can disrupt these processes, leading to prolonged hysteresis. Using historical sedimentation data, we simulated the future terrestrialization … Long-term sedimentation patterns influence the ecological succession of shallow lakes. However, human-induced impacts can disrupt these processes, leading to prolonged hysteresis. Using historical sedimentation data, we simulated the future terrestrialization of Lake Izunuma-Uchinuma, a Ramsar-listed wetland in Japan. The results indicated that ecotone recovery would take over 150 years, highlighting the strong legacy effects of shoreline vegetation loss. To accelerate restoration, we implemented an integrated approach that combined water-level management with sediment stabilization structures, including fences and coconut mat rolls. Over three years, these interventions successfully restored shoreline sediment accumulation, facilitated the re-establishment of Zizania latifolia (from 328 m2 to 1537 m2 in Ecotone 1), and improved water quality and waterbird use. Waterbird abundance significantly increased (p < 0.05) in the treated zones, and sediment exposure led to a reduction in COD release, indicating improved substrate conditions. Our results suggest that proactive ecotone restoration strategies, including hydrological regulation and sediment management, are essential in lakes where natural recovery is hindered by long-term sedimentation deficits and water-level changes. This study highlights the importance of integrating these measures to mitigate hysteresis and enhance ecosystem resilience in degraded shallow lakes.

On the effect of channel slope on seepage-driven bank collapse in tidal channels

2025-06-12

Kaili Zhang , Zheng Gong , Giovanni Coco +2 more | Applied Ocean Research

Experimental Assessment of Scour Around Side-by-Side Double Piers in an S-Shaped Channel with Ice-Jammed Flow

2025-06-12

Zhonglin Li , Zhenhua Zhang , Jueyi Sui +1 more | Water

Through laboratory experiments in an S-shaped channel, this study analyzes how the flow Froude number, the ratio of ice-to-flow rate, pier spacing-diameter ratio, and bed material median grain size influence … Through laboratory experiments in an S-shaped channel, this study analyzes how the flow Froude number, the ratio of ice-to-flow rate, pier spacing-diameter ratio, and bed material median grain size influence scour depth around side-by-side double piers under ice-jammed flow conditions. Unlike the development of a scour hole around a bridge pier in a straight channel, where the scour depth increases with the flow Froude number under ice-covered conditions, this study reveals that in an S-shaped channel, scour depth increases with the flow Froude number near the convex bank pier and decreases near the concave bank counterpart. Irrespective of ice conditions, a higher ratio of pier spacing-diameter correlates with augmented scour depth at the convex bank and diminished scour at the concave bank. As the ice-to-flow rate ratio increases, the ice jam thickness in the S-shaped channel also increases, leading to a significant decrease in the flow area and resulting in deeper scour holes around the piers. Equations have been developed to calculate the maximum scour depth around side-by-side double piers positioned in an S-shaped channel with ice-jammed flow.

ML-based prediction of scour depth around a cylindrical bridge pier: A comparative analysis of ANN, SVM, and Ensemble Trees

2025-06-09

Geeta Devi , Vijay Kaushik | Ocean Engineering