India witnessed one of the worst landslides in Wayanad district of Kerala this week claiming more than 200 lives.
According to ‘Landslide Atlas of India’ by the National Remote Sensing Centre (NRSC) of Indian Space Research Organisation (ISRO), landslides mainly occur along slope of hills due to natural triggering factors such as heavy rainfall and earthquake or due to anthropogenic activities such as construction of roads, buildings and mining.
Geospatial landslide inventory database mapped by NRSC has reported nearly 80,000 landslides in India during 1998-2022. Most landslides occur between June and September.
In India, more than 0.42 million sq km (12.6 per cent) of land area, excluding snow-covered area, is prone to landslide hazards. Of this, 0.18 million sq km area is in North East Himalaya. This includes Darjeeling and Sikkim. Another 0.14 million sq km falls in North West Himalaya, including Uttarakhand, Himachal Pradesh and Jammu and Kashmir.
Nearly 0.09 million sq km of land area in Western Ghats and Konkan hills is prone to landslides. Tamil Nadu, Kerala, Karnataka, Goa and Maharashtra are part of this land area. Around 0.01 million sq km in Eastern Ghats of Aruku area in Andhra Pradesh are also prone to landslides.
This database covers landslide-vulnerable regions in 17 states and two Union Territories in the Himalayas and Western Ghats. Rudraprayag district in Uttarakhand is at the top of this ranking having the highest landslide density in India. The region is also having highest exposure to total population, working population, literacy and number of houses.
In terms of number of districts, Arunachal Pradesh has a maximum of 16 districts in this ranking, followed by Kerala and Jammu and Kashmir at 14 each. Uttarakhand has 13 districts ranked as vulnerable to landslides.
Why Himalayas, Western Ghats vulnerable?
States such as Uttarakhand and Himachal Pradesh, and UT of Jammu and Kashmir, are the worst affected by the landslides disasters as the majority of the vulnerable territory falls within the Himalayas.
The Atlas notes that many districts of these states have high population densities, and major pilgrimage routes or major tourism spots are exposed and affected by landslides.
Although the North Eastern states have many landslides every year, they are not particularly vulnerable to them in terms of socioeconomic factors due to their lower population density and wide unoccupied mountain areas.
Vulnerability of the inhabitants and households is more significant in the Western Ghats due to the very high population and household density, especially in Kerala, even though landslides occur here, when compared to Himalayan regions.
The Kerala Story
Replying to a question on landslides in Kerala in Lok Sabha in 2020, the Government had said that geo-environmentally 13 out of 14 districts in Kerala are variably landslide prone. Each year during monsoon, many landslide trigger within the fragile hill slopes of Kerala. Sometimes, these are impacted as wide-spread and major landslide hazards due to exceedingly high amount of precipitation acting as vital trigger to wide spread land sliding.
The Government also informed Lok Sabha in 2020 that the Geological Survey of India (GSI) carried out post-disaster landslide inventory mapping in two phases during the 2018 Kerala deluge and collected geoscientific details of 2002 landslide incidences. The number of houses affected due to landslide events and the number of houses to be relocated were also identified and reported to the Kerala government along with a detailed list of the landslide inventory.
During 2019, GSI carried out post-disaster studies of 196 landslide incidences and also submitted the report to the State government.
The government’s answer mentioned that GSI’s National Landslide Susceptibility Mapping (NLSM) programme completed landslide susceptibility mapping on 1:50,000 scale of the entire landslide-prone Western Ghat terrains (91,755 sq km) between 2014 and 2020. This included Kerala (19,326 sq km), Tamil Nadu (10,081 sq km), Karnataka and Goa (34,156 sq km), and Maharashtra (28,192 sq km). A total of 3885 landslide incidences were recorded in the Western Ghat terrain during the period.