A Comparison of Landslide Susceptibility Zonation of Poonjar Sub-watershed, Kerala by Certainty Factor and Physically Based Methods

Landslides are one of the most devastating natural disasters which may lead to loss of life and property. Western Ghats region of Southern India is identified to be one of the main landslide susceptible area？ by many researchers in the past. After identifying the slope angle, soil thickness, and the geotechnical properties cohesion, friction, density and permeability？ as the major causative factors, this study presents the popular physically？ based tool namely Stability Index and Mapping (SINMAP) and a bi-variate statistical method namely Certainty Factor (CF) for the Landslide Susceptibility Zonation (LSZ) of Poonjar sub-watershed in Western Ghats. Single calibration mode is invoked in SINMAP by considering land use type as the theme in the present study to prepare the LSZ map. The thematic layers of different causative factors are prepared and subsequently the landslide inventory map is overlaid upon them to get the landslide density of the whole area and that of each layer and the associated classes.？ Then the weights for each class are calculated by CF method and addition of weighted layers is made in ArcGIS platform to get the final landslide susceptibility map for the study area. Finally the map is reclassified and divided to get the LSZ map of the study area. A comparison of zonation maps shows that both the methods are successful in capturing the landslide information in moderately susceptible areas of Poonjar sub-watershed.