Hydrometeorological Landslides on the Windward Side of Western Ghats – A Case Study of Kootickal, Kerala, India

On the windward side of Western Ghats, the frequency of landslides has significantly increased in recent years. Kerala had catastrophic landslides and floods in 2018, 2019, 2020, and 2021, resulting in loss of lives and property. On October 2021, a cloudburst occurred in middle Kerala, causing multiple devastating landslides in districts of Kottayam and Idukki. The study focused on how the topographic, physical, geological, and anthropogenic factors in the windward slope of the Western Ghats influence the occurrence of landslides. The landslide susceptibility was analyzed using the frequency ratio method on the basis of recently occurred landslide locations in the Manimala river basin, with special reference to Kootikal. The impact of each factor was analyzed against the GPS coordinates of landslide locations to estimate the frequency ratio value. The findings revealed that the torrential rainfall experienced in Kerala and the anthropogenic activities, especially the watershed management work performed in the area, significantly increased landslide susceptibility of the basin. About 5% of Manimala river basin is highly susceptible to landslides, and this area comes under the Kootikal sub-basin. The study recommends a rigorous geophysical assessment on the influence of watershed management operations on a landslide and an EIA of roads in the Kootickal region.