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Title: SEDIMENT TRANSPORT CAPACITY OF SHALLOW FLOWS IN UPLAND AREAS

Author
item PRASAD, S. N. - UNIV. OF MISSISSIPPI
item RAO, S. M. - UNIV. OF MISSISSIPPI
item Romkens, Mathias

Submitted to: International Soil Conservation Organization (ISCO)
Publication Type: Proceedings
Publication Acceptance Date: 7/1/2004
Publication Date: 7/31/2004
Citation: Prasad, S., Rao, S., Romkens, M.J. 2004. Sediment transport capacity of shallow flows in upland areas. Paper 659. International Soil Conservation Organization Conference Proceedings. July, 2004. Brisbane, Queensland, Australia. CD-ROM.

Interpretive Summary: Soil erosion on upland areas is a highly complex phenomenon involving many component processes. One of these is the transport of detached soil particles by excess rainwater in overland flow. The ability of surface flow to transport soil particles is determined by a host of factors such as the flow rate, flow velocity, particle size and quantity, surface roughness conditions, etc. It has routinely been assumed that each flow regime has a maximum capacity of carrying sediment and that sediment movement is fairly uniform and determined by the hydrodynamics of the flow regime. This study shows that sediment transport mechanics is far more complex that so far has been assumed. The results of this experimental study indicate that sedimentary fluid mechanics, that is, the interactions between sediment particles through loss and gain of kinetic energy in collisions and flow, determine the mode of sediment movement in shallow flow. This mode consists of sediment waves, or ripples, which transition into a meandering structure under an otherwise constant flow and sediment addition regime. These results may have important ramifications relative to the sediment transport capacity in overland flow and stream systems.

Technical Abstract: In this paper, the sediment transport in flow on steep, shallow channel is discussed. The fundamental mode of flow organization of a solid-fluid mixture is described both qualitatively and quantitatively, and their interactive organizational relevance in overland transport processes is discussed. Laboratory channel flow experiments were conducted on a variable sloe flume with vibratory hopper arrangements to feed dry sediments under controlled conditions. Traditional hydraulic and sediment measurements were made to determine the basic parameters, but new photonic measurements are introduced to reveal information of the sediment dynamics. Specifically, particle velocity and solid fraction measurements were made under various flow conditions. Measurements of the sediment transport rates indicate that the highest values were obtained at the limit of the sediment saltation mode. There exist critical values of the solid fraction when patterns begin to form on the bed at which point dramatic decreases in the sediment transport rates were noted. This paper summarizes results of these findings.