Channel Sediment Transport Research Articles

Estimating sediment transport in a braided gravel channel — The Kawerong River, Bougainville, Papua New Guinea

It is difficult to estimate sediment transport in braided rivers because of the complex hydraulics of rapidly changing multi-channel systems. This paper describes an algorithm for generating sets of braided-river hydraulic parameters for use with sediment transport equations. The algorithm uses random number-based simulation techniques and empirically determined probability distributions of individual hydraulic variables from the White River (U.S.A.) and the Kawerong River. A test of the suitability of the algorithm for the estimation of sediment transport was carried out over a period of two years using the Meyer-Peter and Muller equation on eight reaches of the Kawerong River in which sediment transport is known. The test produced a mean absolute error of 16.3% suggesting that the algorithm may have some potential in braided-river modelling.

Deep-Sea Deposition in Density-Stratified Cratonic Basin, Bell Canyon Formation (Permian), Delaware Basin, Texas-New Mexico: ABSTRACT

Sand and silt of the Bell Canyon Formation were deposited in a euxinic, deep-water, density-stratified basin. Laminated silt formed by suspension deposition from density interflows which moved along thermohaline interfaces; silty sand was deposited by bottom-hugging density underflows in submarine channels. The geometry of sandstone bodies is controlled by the configuration of nearly parallel, erosional channels oriented at high angles to the basin margin which range from less than 0.5 km to more than 8 km in width, 1 m to greater than 35 m in depth, and extend more than 70 km basinward. Channel erosion and sediment transport are interpreted to have resulted from long-lived density underflows which had many irregular fluctuations in flow strength. The flows may have origi ated as saline water was flushed from evaporitic shelf lagoons during storm ebb flow. The channels differ from modern and ancient submarine-fan channels attributed to turbidity-current processes in several ways, including: (1) the lack of radial or branching distributary-channel pattern; (2) few proximal to distal changes in grain size, bed thickness, and sedimentary structures; (3) the presence of abundant large-scale cross-stratification; (4) the lack of graded beds and Bouma sequences; and (5) the absence of clay-size detritus, levee, or overbank deposits. More than 100 oil and gas fields produce from the Bell Canyon Formation in west Texas and southeast New Mexico. Most reservoirs in the northern Delaware basin are stratigraphic-hydrodynamic traps which occur where deep sandstone-filled channels are incised into less permeable interchannel siltstone. Similar types of elongate, basinal, sandstone bodies confined to linear channels might be expected in other cratonic basins where there is a high potential for density stratification of basin waters and the generation of saline density currents. End_of_Article - Last_Page 553------------

NUMERICAL MODEL INVESTIGATION OF SELECTED TIDAL INLET-BAY SYSTEM CHARACTERISTICS

A spatially integrated one-dimensional numerical model of inlet bay hydraulics has been combined with a simple sediment transport model to investigate selected tidal inlet-bay system characteristics. A parametric study has been performed using the models to determine the effect of various factors on the net direction and order of magnitude of inlet channel flow and sediment transport. Factors considered include astronomical tide type, storm surge height and duration, variation in bay surface area, time-dependent channel friction factor, and the addition of a second inlet connecting the bay and sea.

A Sediment Transport Model for Straight Alluvial Channels

The paper presents a simple mathematical model for sediment transport in straight alluvial channels. The model, which is based on physical ideas related to those introduced by Bagnold (1954), was originally developed in two steps, the first describing the bed load transport (Engelund 1975) and the second accounting for the suspended load (Fredsøe and Engelund 1976). The model is assumed to have two advantages as compared with empirical models, first it is based on a description of physical processes, secondly it gives some information about the quantity and size of the sand particles in suspension and the bed particles.

Equations for resistance to flow and sediment transport in alluvial channels

The commonly accepted parameters for sediment transport and resistance to flow of alluvial channels are evaluated and found to be inadequate. A resistance equation B2= [V/(gDS) ½]{[(s−1)12;/(DS)½}·[(s − 1)gd¼/ω²]and a sediment transport equation C = {103[VS/ϕ(d)]− [(k)s−1)g½d)/ϕ)d)D½] [(s−1)gd¼/ω2] channels, where B is a factor that describes the constraints that limit the response of dependent variables to changes in independent variables, V is the mean velocity, D is the mean depth, S is the energy gradient, g is the acceleration of gravity, s is the specific weight of the sediment, d is the median diameter of the sediment discharge, ω is the fall velocity of a characteristic particle size, ϕ(d) has the dimensions and characteristics of a fall velocity with values found by experiment, and k is a dimensionless velocity distribution parameter. Factor C is the concentration by weight in parts per million of the transported sediment. There is no differentiation between forms of transport. Presently used equations are shown to be approximations of combinations of these two equations. The two equations describe channel behavior and sediment transport better than other equations, and they are shown to be particularly effective in describing the effects of changes of temperature on water discharge.

A Role of Sediment Transport in Alluvial Channels

Once a critical amount of sediment is being moved in an alluvial channel, velocity can be expressed as a function of slope and of size and composition of the moving sediment load. Depth is a redundant parameter. At sediment transport rates below critical, depth is an effective parameter. Methods of determining the size and composition of the moving sediment load are analyzed as is the problem of determining when depth becomes redundant. The phenomena of fill and scour at alluvial channel sections is also considered.

Management of Ephemeral Stream Channels

Most runoff from small arid land watersheds in the Southwest is abstracted by ephemeral channels before reaching perennial streams. Some of the abstracted water reaches ground-water storage, but most is lost to evaporation and transpiration. Records from the USDA–ARS Walnut Gulch Experimental Watershed in Southeastern Arizona are used to estimate channels abstractions and to provide estimates of potential added usable water for increased downstream urban water demands. Estimates of salvageable water based on Walnut Gulch data are extrapolated to suggest the potential of ephemeral channel management in a river basin, and questions of management effects on channel equilibrium, sediment transport, and flood frequency and magnitude are considered.

Sedimentary dynamics under tidal influences, Big Grass Island, Taylor County, Florida

Tidal currents augmented by a general rise in sea level of about 0.5 ft. since 1910 have reworked and redistributed relict Pleistocene and Holocene sediments in the low-wave energy environment around Big Grass Island, Florida. Alterations in the textural parameters of sediments from the storm berm, and tidal channels, deltas and flats are a result of local hydraulic energy regimes. The position of inflection points on cumulative grain-size distributions from all of the environments represents winnowing at specific levels of wave and/or current power. Forced tidal flow concentrated by water head accumulation of the flooding tide against a barrier has initiated channel erosion, sediment transport and tidal delta deposition. Better channels facilitate more effective current concentrations, and enhance erosion. An accelerated rate of erosion and deposition results from the process-response mechanism of the tidal-current channel-system. Flood-current velocities are controlled by tidal range, amount of tidal-flat exposure during the previous low tide and equalization of head differential. Highest flood velocities occur at the beginning of the cycle. Tidal range and depth of minimum low water control the velocities of the tidal ebb currents. Highest ebb velocities occur in the latter part of each cycle. Tidal erosion is greatest when mean seasonal sea level is lowest.

Analysis of Channel Geometry and Sediment Transport in Palung and Chitlang Watersheds Using GIS

Channel geometry and sediment transport have been analyzed using Geographic Information System and statistical methods in Palung and Chitlang sub-watershed of Kulekhani watershed located in the Central Hills of Nepal, which covers 87.9 sq. km of land surface.The study demonstrates that the channel geometry and sediment transport changes abnormally in downstream distance for both rivers, though there are some controlling factors i.e. lithology, land use, climate, vegetation cover etc.Key words: Channel geometry; discharge; GIS; landscape; River morphologyDOI: http://dx.doi.org/10.3126/jhm.v6i1.5490Journal of Hydrology and Meteorology, Vol. 6, No. 1 66-75

Use of the cottonwood in an investigation of the recent history of a flood plain

A ring count of cottonwood trees along the Little Missouri River in western North Dakota has permitted contouring of the age of floodplain forests. The germination and growth of the cottonwood is closely related to the discharge of the river, movement of the channel, and development of the floodplain. The trees, in bands, show an orderly increase in age upvalley and away from the channel. Each band is the result of the rise of a thicket on a riverside sandbar and, thus, a record of recent migrations of the channel. A model of channel migration and sediment transport has been constructed. Evidence indicates that the channel has been within a few feet of its present elevation for the past 150 years.

Study of Channel Erosion and Sediment Transport

Observations of channel erosion, flow, and sediment transport for the Rio Puerco, in New Mexico, indicate that the characteristics of the channel and of the channel material change rapidly because of deposition and erosion, and that the ephemeral flows carry extremely high concentrations of suspended sediment that influence flow and transport characteristics.

Forms of Bed Roughness in Alluvial Channels

Laboratory experiments in a large recirculating flume, in addition to field studies, have established that resistance to flow and sediment transport in alluvial channels are related to the form of ...

SIMILARITY AND DESIGN METHODS OF RIVER MODELS WITH MOVABLE BED

In this paper, the similarity, various similarity ratios and design methods of distorted rivermodels with movable bed in consideration ofnew developments in many researches for flowing water and sediment transport in open channels are investigated. The results obtained would contribute much to the designs and experiments of distorted or un-distorted river models with movable bed.

Forms of Bed Roughness in Alluvial Channels

Field studies and laboratory experiments in large recirculating flume have established that resistance to flow and sediment transport in alluvial channels are related to form of bed roughness; forms of roughness can be divided into lower and upper regimes of flow on basis of their shape, resistance to flow, and sediment transport; possible relationship that may prove useful in predicting configuration of bed is introduced.

ON THE EQUILIBRIUM BED SLOPE IN RIVERS WITH SEDIMENT TRANSPORT

In this paper, the authors theoretically analyzed the equilibrium bed slope in rivers with sediment transport with gradually varied width and same width of rectangular cross sections, in consideration of the new developments in the many researches of flowing water and sediment transport in open channels. Combining the equations of motion and continuity for non-uniform steady flow with the equations of motion (formula for sediment transportation) and continuity for sediment transport and the equations of the resistance law for flowing water with sediment transport, the authors introduced the fundamental equation of the equilibrium bed slope in rivers with sediment transport by solving the equation of motion for non-uniform steady flow. Furthermore, the authors introduced the formulas of the equilibrium bed slope in rivers with sediment transport with gradually varied width and same width of rectangular cross sections from above fundamental equation.Last of all, a numerical example was added to demonstrate the method of application to a river with sediment transport.