WEPP: Soil erodibility experiments for rangeland and cropland soils

THE Water Erosion Prediction Project (WEPP) combines knowledge of soil erosion processes with other important processes in a simulation model to predict soil erosion by water ( 6, 9 ). WEPP models soil erosion as a process of rill and interrill detachment and transport ( 8 ). This is much different than the universal soil loss equation (USLE), in which the factors understood to affect soil erosion were quantified in an empirical technology ( 19 ). Because WEPP deals with soil erosion prediction in a different manner than the USLE, new soil erodibility parameters are required. This was identified early in the project as a critical component for the successful development of the WEPP technology ( 7 ). Soil erodibility in WEPP The susceptibility or resistance of a soil to detachment and transport usually is recognized as a major determinant of soil erosion for a particular site. Generally, soil erosion models, including the USLE, incorporate a soil's susceptibility to erosion as a single parameter, termed soil erodibility, in the portion of the model dealing with soil detachment and transport. Even such models as CREAMS ( 17 ), which are process-based, use the USLE soil erodibility values to compute needed erodibilities. Interrill erosion is the detachment and transport of soil particles by raindrops and …