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Sunday, 4 August 2024

At least 361 people dead following series of landslides in Kerala State, India.

At least 361 people have lost their lives, with another 206 still missing and more than 273 having suffered injuries, following a series of landslides in the Wayanad District of Kerala State on 30 July 2024. The landslides occurred when heavy rains associated with the onset of the onset of the annual monsoon. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall. The landslides have affected the villages of Punjri Matom, Mundakkai, Chooralmala, Attamala, Meppadi and Kunhome.

Rescue workers searching for survivors following a landslide in Wayanad District, Kerala, on 30 July 2024. Times of India.

Monsoons are tropical sea breezes triggered by heating of the land during the warmer part of the year (summer). Both the land and sea are warmed by the Sun, but the land has a lower ability to absorb heat, radiating it back so that the air above landmasses becomes significantly warmer than that over the sea, causing the air above the land to rise and drawing in water from over the sea; since this has also been warmed it carries a high evaporated water content, and brings with it heavy rainfall. In the tropical dry season, the situation is reversed, as the air over the land cools more rapidly with the seasons, leading to warmer air over the sea, and thus breezes moving from the shore to the sea (where air is rising more rapidly) and a drying of the climate.

Diagrammatic representation of wind and rainfall patterns in a tropical monsoon climate. Geosciences/University of Arizona.

Wayanad District is thought likely to have become more vulnerable to landslides due to the extensive deforestation it has suffered in recent years. Tree roots can help to hold soft sediments together on slopes, and deforestation is often associated with landslides. According to a 2022 study led by Kakoli Saha of the School of Planning and Architecture, Bhopal, between 1950 and 2018 Wayanad District lost around 62% of its forest cover, mostly being replaced with tea plantations, which have much shallower root systems, failing to stabilise steep slopes.

Land use land cover change of Wayanad District from 1950 to 2012; (A) land use land cover till 1950; (B) land use land cover till 1982; and (C) land use land cover till 2012. Saha et al. (2022).

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