Estimation of Soil Erosion and Sediment Yield During Individual Rainstorms at Catchment Scale

Lushi basin, named after the Lushi County, is one of the sub-basins of the Yellow River basin in China. The basin is suffering from severe soil erosion problems, especially during the "wet" season. In order to identify the proper soil management approaches for the basin, an erosion model is designed to estimate the soil erosion and sediment yield during single events. The hydrological model used for the estimations in the study is the BTOPMC model, which is developed based on the TOPMODEL. Under the model structure of BTOPMC, a modified form of the Universal Soil Loss Equation (USLE) was incorporated as a core module of the erosion component. In the modification, the runoff ratio, an important determinant of soil erosion, was brought into the USLE equation and consequent modifications were made to the soil erodibility and slope length factors. A concept of total sediment transport capacity for single events is applied in the model to route the surface erosion from each discrete cell to the basin outlet. The BTOPMC model was used in simulating the river discharges and sediment yields for 29 events in the Lushi basin. Its acceptable performance validates the model's predictive ability in simulating the basin-scale erosions during individual rainstorms.