Landslide susceptibility zonation of the Western Ghats region in Thiruvananthapuram district (Kerala) using geospatial tools: A comparison of the AHP and Fuzzy-AHP methods

Landslides are one of the most common geohazards occurring in the Western Ghats region of Kerala, causing substantial loss of life and property. The present study aims to demarcate the landslide susceptible zones in the Western Ghats region of Thiruvananthapuram district using GIS techniques. The analytical hierarchy process (AHP) and fuzzy-analytical hierarchy process (F-AHP) methods are used to derive the weights. Eleven causative factors, viz. slope angle, elevation, aspect, road buffer, land use/land cover types, sediment transport index, stream power index, drainage buffer, lithology, soil texture, and lineament buffer have been considered for the mapping process. The area of the susceptibility maps was categorized into five zones: very low, low, moderate, high, and very high. This study confirmed that the majority of landslides occurred due to anthropogenic reasons (road cuttings). Finally, the receiver operating characteristic (ROC) curve method was used to validate the landslide susceptibility maps. The area under the ROC curve (AUC) value was above 0.70 for both the AHP (0.71) and F-AHP (0.76) methods. Hence, it is confirmed that the F-AHP model is more effective in demarcating landslide susceptible zones. As per the landslide susceptibility map created using the F-AHP model, 10.97% of the study area is categorized as very high susceptible. The result of the study will help policy makers and planners to implement effective mitigation measures to prevent landslides along the road cuttings in other areas with similar geomorphological characteristics.