Evaluation of WEPP model in estimating amount of sediment from forest road (Case study: Kohmiyan- Azadshahr forest)

Forest roads have a significant role in sediment delivery to rivers and causes water quality reduction. This study was performed in Kohmian forest in Golestan province to estimate the amount of sediment production from forest roads using WEPP model and field measurement. The inputs of the model were precipitation, temperature, road template, soil and vegetation. To calibrate the model amount of sediment production of cut slope and roadbed were measured by sediment fences that were installed in culvert outlet. Then amount of sediment production of fill slope was measurement by rainfall simulation with plot area of 1 m2. The amount of sediment production in cut slope, fill slope and roadbed for a 546 m2 segment was 37.63 kg. The estimation of WEPP model for the segment was 35.14 kg. The results showed that the amount of sediment in model was 93% of amount of sediment from field study. Therefore, WEPP model may have high capability in estimation of sediment from forest roads in the study area. WEPP model can be used as a good tool for forest manager for risk assessment if the next studies also show the suitability of the model for Iran.