An Investigation on capability of the physically-based hydrological model for studying the shallow landslides in natural hillslopes (Case study: Ilam Dam Watershed)

Slope instability in steep mountainous areas is the basic problem for land managers around the world. Although، many physically-based models have been presented for hillslope stability in recent years، but none of them consider the effects of plan shape and profile curvature together. The purpose of this research is presenting a physically-based hydrological model to investigate the shallow landslides (1-2 m) in forested areas. In this study، 10 hillslopes were selected using the satellite images of Google Earth. Then، by computing the necessary parameters for the physically-based model obtained from field studies، experimental data and topographic analysis، the factor of safety was calculated for each hillslope and with different rainfall return periods. Finally، the map of landslide zonation was provided for all hillslopes in the research area. The results show that the presented model is able to analysis the slope stability in hillslopes with landslide under natural conditions because the hillslopes with landslide have FS less than 1. Therefore، it can be concluded that combination of topographic and hydrologic models with hillslope stability models which consider the effect of root zone can be used as a physically-based model for investigating the hillslope stability in natural hillslopes.