Landslide Risk Zoning using Frequency Ratio Model (Case Study: Fathabad Rectangular Map Area, Lorestan Province)

Abstract

Landslide is a natural disaster causing huge human and financial losses in different countries every year. Identifying and classifying slide-prone areas and zoning their hazards is an important step to assess environmental hazards. This research has been conducted with the aim of zoning the relative risk of slope instability in Fathabad Rectangular Map Area in Lorestan Province. To study the stability of slopes in this area, slide-prone points were first identified using satellite images and field visits, and then a landslide distribution map was drawn. By combining the map of factors affecting slide with a landslide distribution map, the impact of each of these factors including steepness and its direction, altitude, lithology, distance from the fault, land use, distance from the waterway, and road was measured in an ArcGIS software environment. Afterward, the Frequency Ratio Model was used for landslide risk zoning. The results of this method show that 18.55, 30.67, 26.51, 18.15, and 6.12% of the area is in the risk class of very low, low, medium, high, and very high, respectively. To evaluate and classify the output results of the model, the sum of the utility index has been used. The findings showed that the frequency ratio model has high accuracy in landslide risk zoning.