Context: 

The Indian Space Research Organisation (ISRO) recently released the Landslide Atlas of India, a detailed guide identifying landslide hotspots in the country.

Image Source: The Indian Express

About Landslides:

• Landslides are natural disasters that occur mainly in mountainous terrains where there are conducive conditions of soil, rock, geology, and slope.
• Causes: 
  • Natural causes that trigger landslides include heavy rainfall, earthquakes, snow melting, and undercutting of slopes due to flooding.
  • Anthropogenic activities such as excavation, cutting of hills and trees, excessive infrastructure development, and overgrazing by cattle can also cause landslides.
• Factors:
  • Lithology, geological structures like faults, hill slopes, drainage, geomorphology, land use and land cover, soil texture and depth, and weathering of rocks.
• In India, rainfall-induced landslide events are more common.

How are landslides classified and mapped?

• Landslides are classified based on the type of materials involved, type of movement, type of flow, and lateral spread.
• ISRO’s National Remote Sensing Centre has created a database of landslide-prone regions in India based on events from 1998 to 2022 in the Himalayas and Western Ghats.
• Aerial and high-resolution satellite images captured using Indian Remote Sensing (IRS-1D) PAN + LISS-III, satellites ResourceSat-1 and 2, etc., were used to study landslides over the past 25 years.
• Landslides are classified into seasonal (2014, 2017 monsoon seasons), event-based, and route-based (2000 – 2017) in the pan-India landslide database.

How prone is India to landslides?

• India’s susceptibility to landslides: India is one of the top five landslide-prone countries globally, with high vulnerability in the Himalayas and Western Ghats.
• Major cause of landslides in India: Rainfall variability is the biggest cause of landslides in India.
• Percentage of India’s land area prone to landslides: 12.6% of India’s geographical land area (0.42 million sq km) is prone to landslides excluding snow-covered areas.
• Distribution of landslides in India: 66.5% of landslides occur in the North-western Himalayas, 18.8% in the North-eastern Himalayas, and 14.7% in the Western Ghats.

Landslide Atlas Findings:

• States with highest number of landslides: Uttarakhand, Kerala, Jammu and Kashmir, Mizoram, Tripura, Nagaland and Arunachal Pradesh.
• State-wise trends:
  • Mizoram reported the highest number of landslide events (12,385) in the past 25 years, with 8,926 in 2017 alone.
  • Uttarakhand experienced the second highest number of landslides (11,219) since 1998, with events occurring post-2000.
  • Kerala has been consistently reporting massive landslides since 2018 floods, with 5,191 events in 2018 and 29 in 2021.

• District-wise trends:
  • Arunachal Pradesh has the maximum number of districts (16) with high landslide exposure.
  • Rudraprayag in Uttarakhand is the top vulnerable district with the highest landslide density, total population and number of houses exposed to landslides.

News Source: The Indian Express