Friday, 17 July 2015

Landslide hits Nepal school, killing at least one.

One pupil has been confirmed dead and at least 13 more students and teachers have sustained injuries after a landslide struck a secondary school in the Chhorepatan area of Pokhara on Thursday 16 July 2015. The Ex-Army Public Secondary School was struck at about midday following sustained rains associated with the summer 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 deceased pupil has been identified as Sanjay Gayak, 14.

Rescue work at the Ex-Army Public Secondary School in Chhorepatan on Thursday 16 July 2015. Santosh Pokhrel/Republica.

Landslides are common during the monsoon season in Nepal, which lasts from May to September, with  the highest rainfall occurring in July, when the Pokhara area typically receives around 940 mm of rain in the month.

The approximate location of the 16 July 2015 Ex-Army Public Secondary School landslide. Google Maps.

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.

See also...

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Eight people are known to have died and at least three more are missing after two landslides in Nepal on Monday 25 August 2014. The first incident happened at Baramchi in Sindhupalchowk District, where...

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