Sciency Thoughts: Landslide kills three in Jajarkot District, Nepal.

Three people have died following a landslide in the Jajarkot District of Nepal on Sunday 1 September 2019. The incident happened happened at about 1.45 am, hitting the house in which Parbati Wali, 32, and her daughters Motikala, 9, and Dhansara, 3, were sleeping. All three people in the house were killed, with Parbati's husband, Dal Bahadur Wali, surviving with leg injuries as he was sleeping outside.

The scene of a landslide in Jajarkot District, Nepal, on 1 September 2019, that killed three people. Dinesh Kumar Shrestha/Himalayan Times.

The incident has been blamed on torrential rainfall that has fallen across the area in the last few days. Landslides are common during the monsoon season in Nepal, which lasts from May to September, with the highest rainfall occurring in July. 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.

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.