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

Document Type: Research and Full Length Article

Authors

1 Islamic Azad University, Nour Branch, Nour, Mazandaran

2 Faculty of natural Resources, University of Tehran.

3 Rangeland Management, Gorgran University of Agricultural and Natural Resources Sciences.

4 Rangeland Management, Islamic Azad University, Nour Branch

5 Rangeland Management, Islamic Azad University, Nour Branch.

Abstract

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

Keywords