Development of the Alternative Soil Erodibility Estimation Formulae for WEPP Model Based on the Consistency Index

Abstract

One of the inputs to the WEPP model for simulating soil erosion is the soil erodibility coefficients, which indicate the soil-specific susceptibility to erosion. Rill erodibility and critical shear stress are generally calculated using equations that use soil texture and organic matter content as variables, but these equations may not be applicable to Japanese soils. In this study, laboratory rill erosion tests, liquid plasticity limit tests, and particle size tests were conducted on 15 Japanese soils to propose alternative equations for the rill erodibility and critical shear stress. The results showed that the possible range of the soil erodibility coefficients depends on whether the soils are plastic or not, and that the non-plastic soils were more erodible than the plastic soils. For plastic soils, the rill erodibility was formulated using the plasticity index or sand content as variables, and the critical shear stress was generally positively correlated with clay content. On the other hand, for the non-plastic soils, there was a positive linear relationship between the rill erodibility and sand content, and the critical shear stress was generally constant.