Determining of the most appropriate method for calculation of LS factor of RUSLE3D model in a typical semi-arid mountainous watershed

Assessing of topographic effects for erosion modelling and model calibration can differ in terms of complexity, considered processes and data availability. The topographic factor is the most sensitive parameter of RUSLE3D model for predicting of the soil loss, where a higher relative effect of the steepness factor is observed in a simple analysis of sensitivity. Due to wide spread application of USLE family models, finding the most accurate method for calculating of LS factor is a key point in each environmental condition. Therefore, This research was conducted to find the accurate method and suitable geodata to calculate the LS factor based on using of DEM with two resolutions 10 & 30 meter, three methods for calculation specific catchment area and calibration of m parameter to create a distributed model different erosion features (facies). Results indicates that the m & n exponents of runoff and slope terms in LS’s equation reflect soil detachment and sediment transport capacity concerned to the relationship between hydraulic characteristics of overland flow More spatial data analysis revealed that the validation analysis showed that calculation of LS factor based on the contribution area per unit contour length through 30*30m DEM is more closer to estimated erosion in the study area. However, for better calibration of RUSLE3D model in the study watershed the new value for m parameter m was estimated. Due to nature of LS equation the results of erosion rate is more sensitive to m and the new values of m for different erosion facies were estimate to estimate more accurate soil erosion under semi-arid condition.