Landslide Susceptibility Mapping for Subalpine Grassland Using Frequency Ratio and Landslide Index Model (Case Study: Masoleh Watershed, Iran)

Subalpine ecosystems are highly fragile as compared to biological andenvironmental factors. Landslide is one of the ruinous upshots of this ecosystem. One of theimpressionable areas in the cause of natural factor is Masoleh watershed in western AlborzMt, (Iran). In order to landslide hazard zonation, landslide index and frequency ratio methodbased on twelve causative factors such as slope, slope aspect, land use, lithology, distancefrom faults, distance from road, distance from stream, rainfall, range condition, StreamPower Index (SPI), Component Topographic Index (CTI) and elevation Receiver OperatorCharacteristic (ROC) curve analysis method was also used to evaluate the model. Theresults showed that geological, physiographical and grassland conditions have an importantrole in landslide area. Overgrazing, grazing in forth of season, early grazing, late termegression, and excess livestock are considered as direct affecting factors on vegetation, sothat they have simultaneous role to make the landslide risk. The verification results via ROCcurve showed that the landslide index model (85%) performed slightly better than thefrequency ratio model (82%). It was concluded that managers and protectors of thisecosystem can inhibit and conserve the landslide by decreasing the amount of livestock, andshort-term exclosure on critical area, and biomechanical dams in landslide-occurred area.