Comparing Sediment Trap Data with the USLE-Forest, RUSLE2, and WEPP-Road Erosion Models for Evaluation of Bladed Skid Trail BMPs

Abstract

Three erosion models, the Universal Soil Loss Equation for Forestry (USLE-Forest), the Revised Universal Soil Loss Equation Version 2 (RUSLE2), and the Water Erosion Prediction Project for Forest Roads (WEPP-Road), were compared to sediment trap data for bladed skid trail best management practices (BMPs). The bladed skid trail BMPs evaluated were: (1) water bar only (control treatment); (2) water bar + lime, fertilizer, and grass seed (seed treatment); (3) seed + straw mulch (mulch treatment); (4) control + piled hardwood slash (hardwood slash treatment); and (5) control + piled pine slash (pine slash treatment). This study used three erosion models to evaluate the BMPs while also using linear regression, model efficiency (NSE), and percent bias (PBIAS) to compare the prediction accuracy and applicability of the models to monthly erosion collected in sediment traps from six replications of the five treatments. Results showed significant treatment differences due to the BMPs, with the control treatment being the most erosive, followed generally by the seed, hardwood slash, pine slash, and mulch treatments. Model predictions indicated that all models were suitable for ranking erosion rates for the skid trail closure treatments for simple hazard or BMP ratings. However, the older and simpler USLE-Forest and RUSLE2 models had satisfactory NSE and PBIAS values, whereas WEPP-Road did not. Results indicate that WEPP-Road needs additional enhancement with regard to skid trail parameters before it can be effectively used for erosion prediction on bladed skid trails.