Shallow Landslide Modeling in Complex Hillslope by Using TOPMODEL and SINMAP Models

Every year many watershed hillslopes are displaced by landslides resulting from deforestation or rainfall-induced saturation. Parameters such as rainfall, saturation rate, soil type, shape and geometry of hillslope affect the landslide of the hillslopes, accordingly, extensive research has been done on the effects of these parameters. Examining the effect of topography and the shape of the slopes on the landslide is one of the issues that requires more research. Hillslopes in nature have 9 different shapes in terms of plan shape (convergence, parallel, and divergence) as well as the curvature of the earth’s surface (concave, convex, and straight). One of the innovations of this study is the investigation of the geometry and topography of the hillslopes upon the landslide based on the suggested SINMAP-TOPMODEL model. The main goal of this research is the investigation of the effect of two features of geometry, the plan shape and profile curvature on the stability of complex hillslopes. TOPMODEL is a hydrological subsurface flow model which is able to predict the magnitude of saturation and soil moisture deficit at any point of a watershed. In this research, TOPMODEL equations were developed so that the geometry of hillslopes could be considered. The saturation index in TOPMODEL was linked to SINMAP slope stability model to estimate the stability of different points of complex hillslope. Based on SINMAP-TOPMODEL model results, it is concluded that convex hillslopes are more stable than concave ones. Moreover, divergent hillslopes showed less sensitivity to land sliding compared to convergent ones.