The Effect of Topography on Surface Sliding of the COMPLEX HILLSLOPES of Watersheds Using SINMAP and TOPMODEL Models

The slopes of watersheds in nature have three converging, divergent and parallel shapes in terms of plan shape and three convex, concave and flat shapes in terms of floor curvature. In general, there are 9 shapes and geometries for hillslopes, which are called complex hillslopes. Past researches have shown that the topography and geometry of the complex hillslopes have an effect on many hydrological characteristics of the domains, such as the degree of saturation. The degree of saturation of the domain points depends on the concentration of subsurface flow at each point, which is influenced by the shape of the design and topography of the domain.The purpose of this research is the effect of topography on the surface sliding of the complex hillslopes of the watersheds using SINMAP and TOPMODEL models.

In this research, the TOPMODEL model was used to check the degree of saturation of the complex hillslopes, and the equations of this model were modified so that it could consider the topography of the domains, and the results of the saturation in the TOPMODEL model were transferred to a sliding model called SINMAP. And the effect of domain topography on the stability of complex domains was investigated and compared with MATLAB coding and drawing shapes. It should be noted that the aforementioned models are used based on hydrological and topographical data. The methods used in this research are generally applicable to all geographical and climatic regions. 

Considering that in this research, the saturation index was calculated from TOPMODEL, which indicates the degree of concentration of subsurface flow at any point of the domain and determines the saturation of different points of the domain and has a significant effect on the stability of compex hillslopes and based on the average the stability coefficient of the slopes, on average, convex slopes have more stability than flat and concave slopes, and divergent slopes have more stability than convergent slopes, and the higher the saturation layer thickness and soil hydraulic transfer coefficient, the more stable the slope is. and as the amount of effective rainfall increases and as a result the soil moisture increases, the stability of the slopes decreases.

Based on the results obtained in this research, in the downstream parts, the concave slopes are more stable than the upstream part of the slope, while it is the opposite in the convex slopes. Compared to the saturation index, the local slope of the domain points is a much more important factor in determining the stability of the domains. Based on the average saturation index, convex domains are more stable than concave and divergent domains are more stable than convergent domains. It should be noted that in flat slopes with different plan shapes, the slope value is constant, but the degree of saturation of flat-convergent slopes is more than that of smooth-divergent slopes, and it has made some points of the flat-convergent slope more unstable, and the stability value is from top to side. The bottom becomes less and the end parts of the smooth-convergent domain are in an unstable state, but the entire smooth-parallel and smooth-divergent domains are in a stable state.