Estimating the amount of sediment production and delivery of forest roads using SEDMODL

Forest roads have long been identified as a dominant source of stream pollutants in many forests. Sediment delivered from a road segment to streams causes serious damages on water resources and aquatic life. Therefore، prediction of sediment yield from road network is one of the main issues in evaluation of road construction. Many approaches have been used in the prediction of sediment yield in forest roads in which different factor are considered for sediment prediction. In this study، an effort to predict annual sediment yield from a road network to streams in a forest watershed was conducted using a GIS-based sediment prediction model، the SEDMODL. The preliminary result showed that road traffic، road gradient، and cut slope height were the main factors in estimation of sediment yield from a road network. Therefore، the effects of these factors were assessed Road network، stream، geology and average annual precipitation layers were used. The results of this study indicated that total sediment delivered from forest roads were 18. 8 ton per year. Comparisons among road segment lengths showed that segment 2 produced higher amount of sediment (11. 18 ton/year)، largely due to higher average road gradient (12 %). Also، critical road segments with high sedimentation potential were identified and suitable conservation practices were proposed. The results indicated that the SEDMODL model integrated with GIS techniques can assist road managers to estimate total sediment yield and sediment control.