Calibrating SHE Soil‐Erosion Model for Different Land Covers

Calibration of the rainfall and overland flow erodibility coefficients of a physically based erosion and sediment yield component for the Système Hydrologique Européen (SHE) modeling system is demonstrated using data from $32.54‐m^2$‐field rainfall‐simulator plots with tilled, tilled‐twice, clipped, grazed, and ungrazed land treatments. Good sensitivity to the major classes of treatment is exhibited, but the fine detail of variation for a given land cover is less well represented. This is a result of a lack of quantitative understanding of relevant processes that can be remedied only through detailed process studies. Good simulations of overland flow response were achieved for successive rain applications on wetted soil. Difficulties experienced in simulating overland flow response for dry soil probably resulted from poor definition of the soil hydraulic properties for dry conditions. Tests using other soil erosion data show that laboratory calibration of the erodibility coefficients is unreliable, while sensitivity of the simulated sediment yield to the input flow data indicates the need for accurate flow calibrations.