Sixteen people have been confirmed dead and dozens more are feared to be buried beneath debris following a landslide in Maharashtra State, India, on Thursday 20 July 2023. The landslide hit the village of Irshalwadi in Raigad District, about 15 km to the east of Pune, burying seventeen of about fifty houses, in as much as nine metres of debris. The incident happened after 400 mm of rain fell within 24 hours in the area. 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.
Landslides, flooding and other rainfall-related events are common during the annual monsoon, which starts around the beginning of June, but this year the rains have been particularly severe, particularly in the northern part of the country, with over a hundred people having lost their lives since the onset of the season.
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. This situation is particularly intense in South Asia, due to the presence of the Himalayas. High mountain ranges tend to force winds hitting them upwards, which amplifies the South Asian Summer Monsoon, with higher winds leading to more upward air movement, thus drawing in further air from the sea.
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