Three people have been confirmed dead after a landslide hit a bus traveling from Palpa to Butwal on the Siddhartha Highway near Siddhababa on the afternoon of Saturday 8 August 2015, sweeping it into the Tinau River. Twenty six people were on the bus at the time of the incident, and it was initially feared that all had died, but around fifteen passengers have now been pulled from the wreckage alive, though there is little hope of finding any more survivors as the bus is now completely submerged in the river. The incident happened following 24 hours of heavy rain in the area, which reportedly weakened the hillslope above the road. 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.
Rescue workers recover the body of a victim following the 8 August 2015 Siddhababa landslide. DC Nepal.
Landslides are common during the monsoon season in Nepal, which lasts from May to September, with the highest rainfall occurring in July, when the Palpa District typically receives around 230 mm of rain in the month. August is the second wettest month, typically receiving around 130 mm of rain.
The approximate location of the 8 August 2015 Siddhababa 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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