The zonation and assessment of slope instability hazard in Masjed Soleyman city using analytical hierarchy process and frequency ratio methods

Landslide is a destructively geohazard in hilly regions that is responsible for remarkable devastations. Due to geological and geomorphological features as well as land-uses, Masjed Soleyman area is prone to landslide disaster so that 70 landslides record in the region. For this reason, producing the landslide susceptibility map and studying landslides triggering factors are essential for mitigating damages. For this purpose, nine landslide causal factors were considered, including altitude, slope, aspect, stratigraphy, faults and lineaments, rain, land use, proximity to roads and drainages. Then, landslide susceptibility maps were developed by coupling the analytic hierarchy process (AHP) and the frequency ratio (FR) methods in a GIS environment. The resulting maps were categorized into five classes, namely, very high, high, moderate, low, and very low. Results demonstrate that about 69.45% (AHP) and 56.94% (FR) of the study area belongs to the very high and high classes, respectively. Furthermore, prepared maps were validated using 21% of all mapped landslides considered for testing the model. The percentage of validating landslides locations in moderate, high and very high classes in each map was computed (AHP=66.67% and FR=73.33%). Although both models produced reasonable accuracy, the FR model is more accurate than the ones. Therefore, the FR map is trustworthy for planning future developmental activities and environmental protection throughout the study area.