Landslide Hazards Zonation Using the Overlap Index and AHP Method (Case Study: Sattarkhan Dam Watershed)

Abstract

Sattarkhan Dam is constructed on Aharchai Stream in 15 km west of Ahar in East Azerbaijan province. Considering the susceptibility of the dam to landslide hazard, it is critical to determine factors effective on such natural phenomena in this area. Different methods are applied to identify places with high landslide susceptibility in order to prevent and reduce causalities of such natural phenomena. In this investigation, two methods including Overlap Index and Analytic Hierarchy Process (AHP) are implanted for landslide hazard zonation. In this regard, first, the map of landslide occurred in the area was prepared using the available landslide occurrence maps, images, and field studies. Next, the thematic maps and then the associated susceptibility maps were prepared in GIS using eight effective factors including lithology, slope angle, slope direction, land use, average monthly rainfall, distance from faults, distance from streams, and elevation. The role of these factors was divided into several classes and the weight of each class was assigned to the corresponding raster layer and classes of each layer. Based on the obtained results, the study area was divided into four zones with different landslide occurrence hazards by overlapping different layers in GIS environment and preparing landslide occurrence hazard. The data evaluation and processing show that around 38% and 4% of the area is located in zones with high and very high landslide occurrence hazard, respectively. The result also reveals the susceptibility of the study area to such natural phenomenon, which must be considered in the dam lifetime for preventing damages and causalities.