At least 30 people have died and at least sixteen more are still missing following a series of landslides which struck the Darjeeling District of West Bengal State, India, in the first few days of July 2015. At least 25 separate landslides have occurred, several hitting homes in towns and villages and others blocking roads and railways, thereby hampering rescue efforts. The highest death toll occurred in the resort town of Mirik, where seventeen people have now been confirmed dead and over 200 are currently living in temporary accommodation due to damage to or destruction of their homes. Deaths have also been confirmed in Kalimpong, Lava, Sukhia and Gorubathan.
The body of a landslide victim recovered in Darjeeling on Wednesday 1 July 2015. Mikma Lepcha/The Indian Express.
The landslides occurred following a period of 48 hours of continuous heavy rainfall. 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. Such events are common during the monsoon season in Darjeeling, which lasts from June to September, but had not been a problem previously this year, with the area receiving cool weather and moderate rainfall that attracted many visitors to the district's resorts.
Rescue workers searching a building following a landslide in Darjeeling. National Disaster Response Force.
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.
Diagrammatic representation of wind and rainfall patterns in a tropical monsoon climate. Geosciences/University of Arizona.
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