The IXEA Index as an Alternative to the El30 Erosivity Index

The EI30 index used for the rainfall-runoff factor (R) in the Universal Soil Loss Equation (USLE) modeling environment was originally developed from the empirical observation that soil loss increases with rainfall amount and the intensity of the rainfall event. Modern understanding of rainfall erosion processes provides for more process-based indices. In an analysis of erosion data from nonvegetated plots at Holly Springs, Mississippi, the IxEA index, an index that is based on the product of the excess rainfall rate (Ix) and the rate of expenditure of rain kinetic energy (EA), is shown to be superior to the EI30 index. Apart from accounting for the processes of detachment and transport better than the EI30 index, the index provides an opportunity to consider the effects of hydrology more directly within the USLE environment than is currently possible. However, including more direct consideration of hydrology within R is likely to affect a number of other USLE factors. These effects have yet to be evaluated.