Modeling erosion from forest roads with WEPP
Forest roads can be major sources of soil erosion from forest watersheds. Sediments from forest roads are a concern due to their potential delivery to stream systems resulting in degradation of water quality. The Water Erosion Prediction Project (WEPP) was used to predict erosion from forest road components under different management practices. WEPP estimates are compared to measured erosion rates in the southern Appalachians from 24 road sideslope erosion plots on the Talladega National Forest and three road sections on the Chattahoochee National Forest. The first study was conducted to investigate four road sideslope management practices which included RECP (rolled erosion control product) treatment, two vegetation mixtures, and an untreated condition. Sediment yield from treatments was compared to untreated (bare soil) southern Appalachian road sideslopes over the 8-year period. The rate of soil loss was greatest during the first 6 months and decreased thereafter for treated cut- and fillslopes. Mean sediment yield from treated slopes was less than 0.01 t/ha/mm of precipitation. Erosion rates and runoff observed from erosion plots for each management condition over an eight year period were compared to WEPP predictions. Relationships were also developed for soil loss over the study period for treated slopes and the control. These relationships revealed that sediment yield during the first year accounted for 60 to 90 percent of cumulative total sediment yield over the eight year period for the treatments. In the second study, soil erosion from three road sections was compared to WEPP predictions for eight storms of varying size. WEPP predictions were in agreement with measured erosion rates for the forest road components in the investigations. The applicability of WEPP to model these southern Appalachian forest roads was evaluated with a model efficiency statistic using the observed field experiment data.