At least 227 people have died, and another 38 are still reported missing, in a series of landslides, building collapses, and other rainfall-related events in Himanchal Pradesh State, India, so far this monsoon season on 24 June 2023. At least 1200 houses, and numerous businesses and civic buildings, have been destroyed or severely damaged by the rains. More than one hundred people were killed in July, with and at least fifty on 14-15 August. One of the worst incidents happened on Monday 14 August, when the Shiv Bawadi Hindu Temple in the Summer Hill area of Shimla was hit by a landslide, killing at least twelve people, including seven members of the same family. Another five people were killed in a separate landslide in the Phagli district of Shimla on the same day. The following day another two landslides destroyed four houses and an abattoir in the Lalpani area of Shimla.
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 years rains have been unusually heavy across South and Southeast Asia, despite there being an El Niño system over the South Pacific, which would usually bring drier conditions. This is probably linked to the rising global temperature, with the record for the Earth's highest average temperature over a 24 hour period being broken three times in July, which has led to higher rates of evaporation from all oceans, leading to unusually high rainfall in many parts of the world.
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. Himachal Pradesh has been hit particularly hard this year, with record levels of rains recorded in many areas, as well as glaciers melting at faster rates due to global warming, with the effect that many rivers were swollen even before the monsoon rains began to fall.
However, high rainfall is not the only cause of the situation in Shimla, which lies in the Naina Devi foothills of the Shivalik Mountains (which lie along the border between India and Nepal, and are separated from the main Himalaya Mountains by the central Khatmandu Valley of Nepal), and much of it is built on slopes of between 45° and 75°, with more than half of the city on slopes of more than 60°. In the early twentieth century Shimla had a population of about 25 000, but this has now grown to about 300 000, with a major construction boom in the area to support the expanded population. Much of this new construction has been without any attention to the underlying geology, resulting in many four and five story buildings siting on steep slopes of poorly consolidated sediments, making the city and its population exceptionally vulnerable to landslide.
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