A Single, Continuous Function for Slope Steepness Influence on Soil Loss

Abstract Recently proposed relationships for the effect of slope steepness on soil loss by water are linear functions of the sine of the slope angle. The Revised Universal Soil Loss Equation (RUSLE) uses two such functions: one for slopes <9% and another for slopes >9%. Recent research indicates that yet a different linear function is necessary for slopes greater than approximately 22%. The objective of this study was to develop a single slope steepness function that is representative of the data for all slopes. The resultant equation takes the form of a logistic function. It closely follows the RUSLE relationships for the slope steepness factor for slopes up to 22%, and also fits existing data for slopes greater than those from which the RUSLE relationships were derived.