Sensitivity analysis of CULSED model to provide strategies for forest roads sediment control

Forest roads are the most important factor to access the watershed; nevertheless they are the main sources of sediment production. The delivered sediment by forest roads cause environmental problems and pollution of water resources and are dangerous for aquatic life. Many factors play roles in the amount of sedimentation produced by forest roads with different levels. In this study four factors including road width, road slope, vegetation cover and road age were investigated in sediment production by CULSED model and ArcGIS. Sensitivity analysis was used for identifying the sensitivity of the produced sediment to the mentioned factors and for studying the kind of relativity and its value using Spearman rank correlation test and scenario analysis. Results showed that maximum sensitivity belongs to road width, road gradient, vegetation cover and road age, respectively. The Spearman rank correlation has a direct relativity with road width and its slope, vegetation cover and age have a negative relation with sediment production. These results help the forest roads designers to note the most important factors during the initial stages of the designing process and at the other hand when the road is constructed, they could use the suitable management to control and reduce erosion and sediment yield causing negative effects of roads on the water resource pollution.