2 Uttarakhand districts and four in Kerala among top 10 landslide risk districts in the country, ISRO study

“Rudraprayag district in Uttarakhand state, which has highest landslide density in India, is also having highest exposure to total population, working population, literacy and no. of houses (to landslides),” the study based on ISRO satellite maps said.

Rudraprayag and Tehri Garwhal districts of Uttarakhand have the highest landslide density in the country, a satellite based study of the 147 most vulnerable districts by the National Remote Sensing Centre (NRSC) has found, reiterating that the western Himalayan region is most vulnerable to landslides.

Rudraprayag and Tehri Garwhal districts of Uttarakhand have the highest landslide density in the country (PTI)

“Rudraprayag district in Uttarakhand state, which has highest landslide density in India, is also having highest exposure to total population, working population, literacy and no. of houses (to landslides),” the study based on ISRO satellite maps said.

Among the 10 most landslide prone districts, four are in flood prone areas of Kerala, two in Jammu and Kashmir and two in Sikkim. In fact, after the Himalayas, the Western Ghats, which has seen large-scale development in the past few years, has high landslide density.

For the first time, NRSC scientists did risk assessment on the basis of 80,933 landslides recorded between 1988 and 2022 in 147 districts in 17 states and two union territories to build a Landslide Atlas of India.

The risk analysis was based on human and livestock population density, which indicates the impact these landslides have on people, and shows the most landslide vulnerable spots in the country. The atlas used satellite data of ISRO to map all seasonal and event-based landslides like the Kedarnath disaster in 2013 and landslides triggered due to Sikkim earthquake in 2011.

The landslide risk has intensified over the years due to environmental degradation and extreme weather events such as high intensity rainfall, which have increased due to climate change, the scientists said.

“In recent years, we have seen unplanned development in the hills of Himalaya and in Western Ghats, with scant regard for environment and forests. The impact of it, coupled with extreme rainfall, is visible through the rising number of major landslides and land subsidence incidents being reported from Joshimath to Doda to Darjeeling,” said Ravi Chopra, former head of the Supreme Court appointed panel on Char Dham highway project in Uttarakhand.

The new study recorded 80,933 landslide hot spots between 2000 and 2022, with the maximum of 12,385 in Mizoram, followed by 11,219 in Uttarakhand, 7,280 in Jammu and Kashmir and 1,561 in Himachal Pradesh. Among the southern states, the most number of landslide hot spots have been recorded in Kerala (6,039).

Using satellite data, the National Remote Sensing Authority had also recorded total landslides in states between 2010 and 20222, with Uttarakhand recording the maximum landslides in this period. Within the state, Rudraprayag and Tehri districts recorded the highest number of landslides, the study said.

“The main reason for landslides in Rudraprayag and Tehri district is the use of dynamite for blowing up rocks, as it creates fissures in the mountains,” said Vipin Kumar, an environmentalist from Mussoorie. Many slopes in these two districts are already laden with old landslide material and they are unstable and vulnerable to fresh landslides, he added.

“One of the main causes of landslides in Rudraprayag district is the irresponsible approach of cut and dump for road cutting, which are making many slopes unstable,” said Hemant Dhyani, who was member of the Supreme Court committee constituted in 2014 to study the effect of hydropower projects on the Himalayas.

In Tehri, he said, reservoir-induced instability, especially around the Tehri hydropower project, is also causing slope instability, leading to landslides.

The Dehradun-based Wadia Institute of Himalayan Geology has prepared a spatial distribution of landslide susceptible zones of Uttarakhand Himalayas, according to which 51% of the state is located in high and very high landslide susceptible zones, 22–23% in the moderate and 26–27% in the low and very low landslide susceptible zones.

Eight other districts among the top 10 worst affected districts were Thrissur in Kerala, Rajouri in Jammu & Kashmir, Palakkad in Kerala, Poonch in Jammu and Kashmir, Malappuram in Kerala, south and eastern districts of Sikkim and Kozhikode in Kerala. As many as 64 districts of the northeast figured in the list of 147 districts.

The study said a major part of the Himalayan region is susceptible to landslides. It is the high population density, major pilgrimage routes and tourism spots that have worsened the impact of disasters in Jammu and Kashmir, Himachal Pradesh and Uttarakhand. Uttarakhand alone reported over 7,750 extreme rainfall events and cloud bursts since 2015, most being in the past three years, killing over 230 people, it said.

India is the third most landslide prone countries in the world, where every year the loss of lives per 100 sq km due to landslides is more than one, the study said. The other countries are Colombia, Tajikistan and Nepal.

In the west coasts of North and South America, Central America, Alpine regions of Italy, France, Switzerland and Austria in Europe, Himalayan regions of India, Nepal in Asia and parts Central Asia, the effects of landslides are more pronounced, mainly due to the spurred developmental activities to meet the growing demands of people, the report said.

Approximately 0.42 million sq km, or 12.6% of India’s land area, excluding snow covered area, is prone to landslide hazard, according to the study. Of this, out 0.18 million sq km falls is in North East Himalaya, including Darjeeling and Sikkim Himalaya; 0.14 million sq km in North West Himalaya (Uttarakhand, Himachal Pradesh and Jammu & Kashmir); 0.09 million sqkm in Western Ghats and Konkan hills (Tamil Nadu, Kerala, Karnataka, Goa and Maharashtra) and 0.01 million sqkm in Eastern Ghats of Aruku area in Andhra Pradesh.

“In India, landslides mostly occur in the monsoon season. Himalayas and Western Ghats are highly susceptible to mass movements due to hilly topography and heavy rainfall,” the study said.

In India, such disasters mostly occur in the monsoon season, due to heavy rainfall that causes sliding of the slopes that could have been impacted due to use of heavy machinery in developmental projects. However, the NRSC said in the future it would be able to map the slow-moving mountain slopes, which has higher risk of landslides.

(With inputs from Neeraj Santoshi in Dehradun)