Length-Steepness Factor of RUSLE on the Soil Loss Rate Estimation: A Sensitivity Evaluation

Abstract

The Revised Universal Soil Loss Equation (RUSLE) is commonly applied in research studies and industries, especially in erosion and sediment control measures.  In RUSLE, six primary factors contribute to the estimation of soil loss rate.  This study focuses on the sensitivity evaluation of Slope Length Factor (L-Factor) and Slope Steepness Factor (S-Factor) of RUSLE.  A study site in Sarawak (1° 43’ 4.27” N, 110° 19’ 53.09” E) was identified for this study, whereby the actual site conditions were used as input values into RUSLE.  For sensitivity evaluation, the L-Factor ranges from 100 m to 500 m with 20 m slope length increment and S-Factor from 1.0% to 40% with 1.0% slope steepness increment.  Sensitivity evaluation was carried out for both L-Factor and S-Factor for determination of the degree of sensitivity with respect to soil loss.  It was found that the sensitiveness of L-Factor ranges from -33.33% to 49.07% with soil loss rates ranging from 1,352 ton/ha/yr to 3,024 ton/ha/yr.  It was also determined that the L-Factor has a positive linear relationship with other factors in RUSLE, i.e., erosion loss increases linearly with L-Factor.  For S-Factor, significant incremental values were noticed on soil loss (8,421 ton/ha/yr) and the degree of sensitivity (315.14%) beyond slope steepness of 12% (6.84°).  Detailed studies on the coefficient of L-Factor value (m) of S-Factor would require a more refined classification and annotation for different slope steepness.