| چکیده انگلیسی مقاله |
As hillslopes are the basic landscape elements of many catchments, but their shape are not simple. Most of hillslopes are complex (different length profile and plan curvature. To investigate the real shape of complex hillslopes, we considered the curvature in flow direction (concave, straight or convex) and curvature in perpendicular to flow (convergent or divergent plan), means that there are nine complex hillslopes in the nature. All hydrological process (rainfall, surface runoff, subsurface flow, sheet erosion, sediment particles) have been investigated using the physically based models in complex hillslopes. The presented models are composed of three parts of a three-dimensional (3D) hillslope geometry, a nonlinear storage (kinematic wave) model for hillslope hydrological response, an unsteady physically based surface erosion model and statistical analysis of collected data in lab using rainfall simulator and erosion plots. According of our research model inputs, on hillslopes with concave profile (1, 2 and 3), in portion of length detachment and in on another portion deposition is occurred. In hillslopes with straight or convex profile shape, soil detachment is occurred on whole hill length. From hydrologic viewpoint, the convergent hillslopes saturate more quickly compared to the parallel and divergent ones. Also, the travel time of the divergent hillslopes is, on the average, twice that for convergent case. The concave hillslopes saturate sooner in comparison with the straight and convex ones, with shorter travel time. According to the results, the subsurface flows travel time of the divergent hillslopes is less than that of parallel and divergent ones. The convex, straight, and parallel hillslopes showed almost the same travel time. From erosion viewpoint, based on the obtained results, in hillslopes with convex and straight profile curvatures, sediment detachment only occurred in the whole length of the hillslope. However, in concave ones, sediment detachment and deposition only occurred together in hillslope. The hillslopes with straight profiles and convergent plans have the highest rate of detachment. Also, results show that most detachment rates occur in convex profile curvatures. The presented models also were performed in laboratory conditions using a rainfall simulator. Then, the divergent convex hillslope in the plot was designed and filled with soil. Finally, the amount of total sediment and runoff in each event was measured under a rainfall intensity of 30 mm.hr-1. The results showed that the amount of total sediment and runoff decreased in conservation treatment compared to the control plot respectively of 17.07 and 59.38%. |
