Determination of the best landslide susceptibility mapping method in the Ilam dam basin

In the last years, have been accelerated increased the damages of landslides by Natural and anthropogenic factors. One of the main solutions to decrease landslide hazards is avoid from prone areas. For this purpose, it is necessary to prepare the landslide susceptibility map. In this research, after field studies in the Ilam dam basin, nine factors including slope gradient, aspect, elevation, precipitation, distance from road, distance from fault, distance from drainage, land use and lithology have been identified as effective factors in landslides occurrence of the studied area. After preparing the information of these nine factors in GIS environment using Arc View software, every layer has been crossed with the landslide layer to find the role of corresponding layer in the formation of landslide. Then susceptibility mapping was performed with five methods including information value, valuing area accumulation, Analytical Hierarchy Process (AHP), Kopta-Joshi proposed method and frequency ration. Finally, in order to evaluate the verification of the susceptibility mapping, the obtained weights from the Ilam dam basin using the above five methods were used for the adjacent basin (PakalGarab basin), which has similar characteristics to the Ilam dam basin. Results showed that the information value and AHP models give better results for landslide susceptibility mapping of the area.