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Title: SEDIMENT CONCENTRATION IN RELATION TO SURFACE AND SUBSURFACE HYDROLOGIC SOIL CONDITIONS

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

Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/10/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Soil erosion is a very complex phenomenon involving many processes. One of the most vexing problems is rilling and headcut development by surface flow. Little is known about soil properties, soil conditions, the hydrologic and hydraulic conditions which are conducive to rilling and headcut development. In this article results are presented from selected studies which were designed to improve our understanding of soil erosion by the above processes. Four aspects are highlighted: the stabilization of surface soil or seal development during rainfall; the stability of surface seal when subjected to surface flow; seal breakdown by surface flow; and the effect of subsurface pressures on sediment production. The results indicate that subsurface pressures substantially affects sediment production. It is also postulated that headcut development and rilling might appreciably be affected by subsurface or soil matrix water pressures

Technical Abstract: Soil detachment in headcut development and rilling is an important mode of soil erosion. Yet, little is known about soil and hydraulic conditions that are conducive to this process. Studies in progress attempt to determine soil hydraulic and hydrologic conditions that affect headcut and rill development. In this study, results of selected experiments with different soils are reported concerning the effect of seal development, seal stability, and seal breakdown ( the precursor to headcuts) on sediment concentration during rainstorms and surface flow. The soils are a glauconitic sediment, the Ap horizon material of a Neshoba soil, and the Ap horizon material of a Grenada soil. Also, the effect of soil water pressures on sediment concentrations and surface flow rates is determined. The results of this study indicate that seal development and subsurface soil water pressure appreciably affect sediment concentrations. The results also indicate that subsurface pressure may be a critical factor in rill development