Landslides are a prominent natural disaster that have caused widespread damage in several regions of the world, including India. The country has experienced significant landslides over the years due to geographical and climatic factors, particularly heavy rainfall and unstable soil conditions. In response to this, the National Remote Sensing Centre (NRSC) under the Indian Space Research Organisation (ISRO) has recently released a comprehensive Landslide Atlas of India. This document identifies the most susceptible areas to landslides in the country, providing key insights into India’s vulnerability to such natural disasters.
The Creation of the Landslide Atlas of India
The Landslide Atlas of India is the result of an extensive risk assessment conducted by scientists based on data from 80,000 recorded landslides between 1998 and 2022 across 147 districts in 17 states and two Union Territories. For the first time, this atlas uses satellite data from ISRO in its creation. It maps all seasonal and event-based landslides, including noteworthy incidents like the Kedarnath disaster in 2013 and the landslides triggered by the Sikkim earthquake in 2011. The atlas classifies landslides into three categories: seasonal, event-based, and route-based.
Key Findings from the Atlas
According to the atlas, the states with the highest number of landslides between 1998 and 2022 include Uttarakhand, Kerala, Jammu and Kashmir, Mizoram, Tripura, Nagaland, and Arunachal Pradesh. Mizoram reported 12,385 landslide events in the last 25 years, followed by Uttarakhand with 11,219 incidents and then Kerala. Districts with the maximum landslide exposure are found in Arunachal Pradesh, Kerala, Uttarakhand, Jammu and Kashmir, Himachal Pradesh, Assam, Maharashtra, Mizoram, and Nagaland. Of these, the Rudraprayag and Tehri Garhwal districts of Uttarakhand have the highest landslide density and risk exposure in India.
India’s Vulnerability to Landslides
India is counted among the top five countries globally that are most prone to landslides. In fact, reports suggest at least one death per 100 square kilometers a year due to landslide events. Rainfall variability is the biggest cause for landslides, making areas like the Himalayas and the Western Ghats particularly susceptible. Around 12.6% of India’s geographical land area, excluding snow-covered regions, is prone to landslides. Out of all landslide incidents, 66.5% are reported from the North-western Himalayas, 18.8% from the North-eastern Himalayas, and 14.7% from the Western Ghats.
Understanding Landslides: Causes and Prevalence
Landslides typically occur in mountainous terrains where conditions of soil, rock, geology, and slope are favorable. They are characterized by sudden movements of rock, earth, boulders, or debris down a slope. Apart from natural factors such as heavy rains, earthquakes, snow melting, and flooding, landslides can also be triggered by human activities like excavation, cutting of hills and trees, excessive infrastructure development, and overgrazing by cattle. Other factors influencing landslides include lithology, geological structures, hill slopes, drainage, geomorphology, and the weathering of rocks, all of which are taken into account when outlining a landslide susceptibility zone for planning and prediction purposes.