Application of WEPP to a Southern Appalachian Forest road
Forest roads can be major sources of sediment and soil erosion from southern Appalachian Mountain watersheds. Sediments from forest roads are a concern due to their potential delivery to stream systems resulting in degradation of water quality. Prediction of sediment yields from forest road components can provide valuable information in planning, locating, and maintaining road systems to reduce erosion potential. This paper reports an application of the WEPP (Water Erosion Prediction Project) model to cut- and fillslopes during the post-construction and establishment period for an access road constructed in 1995. The WEPP predictions of sediment yield from cut- and fillslopes with two vegetation treatments and an untreated (bare soil) condition were compared to yields observed from replicated erosion control plots over an 8-year period. The rate of soil loss was greatest during the first year and decreased thereafier for treated cut- and fillslopes. Average annual sediment yield was overpredicted for the untreated cutslope which resulted in a somewhat lower model efficiency (ME=0.51) than for the treated cutslope (ME=0.92). The overprediction of the untreated cutslope sediment yields is attributed to accelerated losses observed in the field experiment during the first three years which removed most of the soil available for transport. In contrast, predicted average annual sediment yield was in close agreement with the observed values for the vegetation treatments for both slope types. Model efficiencies ranged from 0.51 to 0.92 for the cutslope and 0.53 to 0.99 for the fillslope. These relatively high model efficiencies indicate that the model adequately describe sediment yields observed in the field experiment.