| چکیده انگلیسی مقاله |
Catchment hillslopes in nature have different plans and profile curvatures. They are divided into convergent, parallel and divergent in terms of the plan form and concave, straight and convex in terms of profile curvature. The universal soil loss equation (USLE) was offered and completed by Wischmeier and Smith (1978). This model estimates the soil loss of slopes based on information such as rainfall, type of soil, vegetation and topography. In the present study, the erosion rates of the nine complex hillslopes were investigated using the universal soil loss equation (USLE). The most important objectives of this study are Development of the USLE model in a way that allows the geometry of complex hillslopes to be considered and comparison of erosion rates over the nine type of complex hillslopes. The topography factor (including slope length and slope steepness) in the USLE (LS function) was developed as a function of plan shape and profile curvature. The hillslopes studied were divided into sets of complex pixels and the erosion over the pixels was calculated. Total erosion was regarded as the sum of erosion of all pixels. Furthermore, to calculate the sediment delivery ratio of each pixel, a new travel time equation for complex hillslopes was employed. Our results also revealed that a hillslope’s degree of convexity is more effective than the hillslope’s convergency in the soil erosion process. This means that the highest erosion belonged to convex divergent slopes and the least erosion were related to concave divergent slopes. The laboratory results intended for validation of the numerical model also show that in hillslopes with fixed plan, the erosion rate in the convex hillslopes exceeds that of concave and straight hillslopes. According to the model results, the erosion rate of convex hillslopes was greater than that of straight and concave hillslopes. On average, the erosion rate of convex the hillslope was 1.43 times that of the concave hillslope and 1.19 times that of the straight hillslope. Furthermore, the highest amount of erosion was related to the convex-divergent hillslope and the lowest was related to the concave-divergent hillslope. |
