Preliminary analysis of a catastrophic landslide event on 6 August 2020 at Pettimudi, Kerala State, India

Abstract

The Western Ghats, the most prominent orographic feature of peninsular India, occupying about 47% of Kerala state, is vulnerable to various types of landslides. The occurrence of cataclysmic landslides along the windward slope of Western Ghats during torrential rainfall is attributed to the unique physiography and climate. A disastrous landslide occurred in the Pettimudi village of Idukki district, Kerala State at 2245 h (UTC+5.30) on 6 August 2020 due to heavy downpour. A preliminary analysis was carried out to understand the characteristics of the event and to investigate the slope failure mechanisms. The landslide was initiated on the steep slopes of Shola forest and was slid through the tea plantations. The dimensions of the landslide scar were measured as 1200m in length, 30-120m width, 3-7m depth and 125m height. An approximate area of 70125 m2 was estimated to be affected by the landslide. The heavy downpour which is thought to trigger the Pettimudi landslide was measured as 61.6 cm/day, the highest ever recorded in the area.The disaster caused 66 fatalities of residents, among which four are still missing, making it the most catastrophic landslide event reported in the state.