14 March 2023

Table of Contents

ISRO releases the Landslide Atlas of India: Which states, regions are most vulnerable

GS-3: Disaster and disaster management.

The India Meteorological Department's (IMD) Statement of Climate of India 2022 reported that the country experienced 835 fatalities due to heavy rain, floods, and landslides.

The increasing frequency of severe weather events, particularly those involving heavy rainfall which can result in landslides and floods, prompted the Indian Space Research Organisation (ISRO) to release the Landslide Atlas of India. This comprehensive resource identifies regions prone to landslides in the country.

Landslides

• Landslides occur naturally in mountainous areas where conditions of soil, rock, geology, and slope are favorable.
• A sudden downward movement of rock, boulders, earth, or debris is considered a landslide.
• Natural Causes: Heavy rainfall, earthquakes, snowmelting, and undercutting of slopes due to flooding are that natural causes can trigger landslides.
• Anthropogenic Causes: Anthropogenic activities such as excavation, hill cutting, excessive infrastructure development, overgrazing by cattle, and deforestation can also cause landslides.
• Landslides are one of the most frequent natural disasters, and they pose a severe threat to human and animal lives.
• They can damage property, roads, and bridges, disrupt communication lines, and snap power lines.
• Factors affecting landslide: Several factors influence landslides, including lithology, geological structures, hill slopes, drainage, geomorphology, land use, land cover, soil texture and depth, and weathering of rocks.

• When designating a landslide susceptibility zone, all of these factors are considered for planning and prediction purposes.
• In India, rainfall-induced landslide events are more common.

The classification and mapping process of landslides

• Landslides are categorized based on the materials involved, the type of movement of the material, and the type of flow of the material.
• Another category includes landslides that spread laterally.
• The ISRO atlas mainly maps event-based and season-based landslides.
• The National Remote Sensing Centre (NRSC) of ISRO in Hyderabad has established a database of landslide-prone regions in India from 1998 to 2022, primarily along the Himalayas and the Western Ghats.
• The landslide analysis is based on aerial and high-resolution satellite images captured by the Indian Remote Sensing (IRS-1D) PAN + LISS-III cameras, ResourceSat-1 and 2 satellites over the past 25 years.
• The pan-India landslide database categorizes landslides into seasonal (2014 and 2017 monsoon seasons), event-based, and route-based (2000-2017).

India's susceptibility to landslides

• India is among the top five countries worldwide that are prone to landslides, with at least one death per 100 sq km reported annually due to landslide events.
• The country's susceptibility to landslides is primarily due to the variability of rainfall patterns, and the Himalayas and the Western Ghats are particularly vulnerable.
• Excluding snow-covered areas, around 12.6 percent of India's geographical land area (0.42 million sq km) is prone to landslides.

• Of these landslides, 66.5 percent are reported from the North-western Himalayas, 18.8 percent from the North-eastern Himalayas, and 14.7 percent from the Western Ghats.

• Nearly half (0.18 sq km) of the landslide-prone areas are located in the states of Assam, Arunachal Pradesh, Sikkim, Meghalaya, Mizoram, Manipur, Tripura, and Nagaland.
• In the Western Ghats, although there are fewer landslide events, inhabitants are significantly vulnerable to fatalities, particularly in Kerala.

The implications of the Landslide Atlas

• Uttarakhand, Kerala, Jammu and Kashmir, Mizoram, Tripura, Nagaland, and Arunachal Pradesh have reported the highest number of landslides during 1998-2022.
• Mizoram has recorded the highest number of landslide events, with 12,385 events in the past 25 years, of which 8,926 were in 2017 alone.
• The situation in Uttarakhand and Kerala is particularly alarming.

• Uttarakhand has experienced the second-highest number (11,219) of landslides since 1998, with all events occurring after 2000.
• Kerala has consistently reported massive landslides since suffering the century's worst floods in 2018, with 5,191 events in 2018, 756 in 2019, 9 in 2020, and 29 in 2021.

• Arunachal Pradesh has the highest number of districts (16) with the maximum landslide exposure, followed by Kerala, Uttarakhand, and Jammu and Kashmir (13 each), Himachal Pradesh, Assam, and Maharashtra (11 each), Mizoram (8), and Nagaland (7).
• Based on the events and images obtained, the NRSC ranked Rudraprayag in Uttarakhand as the most vulnerable district, with the highest landslide density, exposure to the total population, and number of houses in the country.

[Ref- IE]  

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