Effect of slope steepness on soil loss for steep slopes

Slope steepness factor has always been a controversial issue in erosion research. Many researchers in the past have proposed slope factor relationships best describe their experiment conditions and viewpoints. The general conclusion is that the slope factor in USLE overestimates soil loss for steep slope conditions. Hence, the objective of this study is to examine the effect of slope steepness on soil loss for steep slopes. Indoor erosion study was carried out in a 15-m tall rainfall simulator building, Results of the study showed that the soil loss ratio fell within the envelope of S-factor equations proposed by McCool et al. (1987). However, the inclination of soil loss with respect to slope steepness decreased as slope fell between steepness of 30- and 45%. The leveling of soil loss in the spectrum of slope steepness may not seem practicable in USLE structure; on the other hand, occurrence of leveling phenomenon may need further attention in the future erosion research.