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Title: EFFECT OF NEGATIVE SOIL WATER PRESSURES ON SEDIMENT CONCENTRATION IN RUNOFF

Author
item Romkens, Mathias
item PRASAD, S - UNIV OF MISSISSIPPI
item HELMING, K - ZALF

Submitted to: Management of Landscapes Disturbed by Channel Incision Stabilization Rehabi
Publication Type: Proceedings
Publication Acceptance Date: 3/7/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Soil erosion on upland areas is considered to be the combined effect of detachment and transport by raindrop impact and overland flow. The role of the soil medium is usually considred to be part of the soil erodibility factor. Many studies have attempted to relate soil erodibility to an array of properties, mainly physical and chemical, with occasional mineralogical constituents included. Yet, the role of soil water, more specifically soi water pressures, have rarely been considered. While soil properties in their collective and interactive arrangement of the matrix affect detachability, differences in soil water pressures may modify the ease by which soil particles are detached and lifted from the soil matrix. This article presents information about the role of negative soil water pressures on soil detachment and transport. It examines this role for two surface conditions with different degrees of rilling.

Technical Abstract: Soil erosion on upland areas is thought of as the combined effect of detachment and transport by rainfall and surface flow. Soil erosion is usually considered to be an exclusively surface induced phenomenon, in which little regard is given to the role of subsurface hydrologic factors. In this study, the effect of negative pore pressure on sediment concentration is examined in a laboratory flume study involving a series of experiments of simulated rainfall and overland flow. A 20 cm thick soil bed of 8% slope steepness was subjected to a series of stepwise changes in the applied suction at the base of the soil bed. Results indicate that changes in the subsurface soil water pressure only marginally affected water runoff rates but substantially affected sediment concentration. A linear relationship was obtained between the applied suction and the sediment concentration. The effect of suction on sediment concentration was largest for the soil bed with the severest rilling.