SOIL DETACHMENT RATES FOR SEDIMENT LOADED FLOW IN RILLS

Abstract

Rill erosion accounts for approximately 70% of the erosion on upland areas. Net soil detachment from rill bedsdecreases with an increase in sediment concentration in the flow. The objective of this study was to quantify the effect ofsediment concentration in water flow on soil detachment. The effects of slope (5, 10, 15, 20, and 25), flow rate (2, 4,and 8 L/min), and rill length (0.5, 1, 2, 3, 4, 5, 6, 7, and 8 m) on soil detachment were studied. A flume of 1 m 8 m wassubdivided into strips of 0.1 m 8 m to imitate rills. A typical silty loess soil from the Loess Plateau of China was packedinto the flume to a depth of 20 cm. Soil was saturated from above with tap water and allowed to set for a day prior to eachexperimental run in order to facilitate consistent prewetted conditions. Flowrateregulated tap water was introduced intothe rills from the upper end of each segment of rill at the different lengths. The change in sediment concentration with rilllength was determined, and a method was suggested to compute soil detachment rate from the experimental data. The resultsindicate that detachment rate decreased linearly with sediment concentration and exponentially with rill length. The resultssupport the validity of the detachment function used in the Water Erosion Prediction Project model.