Estimating the Best Exponent of the Modified Universal Soil Loss Equation and Regionalizing the Modified Universal Soil Loss Equation under Hydro-Climatic Condition of Ethiopia

Abstract

Soil erosion and sediment transport are quite complex processes as they depend on physical, biological, mechanical, and chemical processes within a particular catchment. Therefore, it is highly essential to better explain engaged physical processes and means of accounting for site-specific conditions, for soil loss and sediment yield estimation. This paper mainly focuses on physical explanations behind erosion and common erosion models like Universal or Revised Universal Soil Loss Equation(USLE/RUSLE) and Modified Universal Soil Loss Equation(MUSLE). Based on the physical explanations and overall limitations, the MUSLE is selected for the application of sediment yield estimation. To regionalize the MUSLE, the main parameters of the MUSLE which directly affect the erosion process such as cover, conservation practice, soil erodibility, and topographic factors are estimated based on the past experiences from literature and comparative approaches, whereas the other parameters which do not directly affect the erosion process or which do not have physical meaning (i.e coefficient a and exponent b ) are estimated through calibration. The best exponent (b) of the Modified Universal Soil Loss Equation is 1, which results in Nash-Sutcliffe efficiency of approximately 1. The regionalized MUSLE shows good performance for all four watersheds under our consideration and we expect the same for other watersheds of Ethiopia.