The moment the glacier collapsed, triggering flash floods in Nepal

Chinese state news agency Xinhua On August 29, it released a video shot two days earlier, showing a snowy mountain scene in Cat Long district of the Tibet Autonomous Region, before a cloud of dust billowed out.

“A tourist accidentally recorded a glacier collapsing in Nepal, leading to landslides and flash floods hitting Cat Long district,” the Chinese news agency said.

Kang Shichang, director of the Institute of Mountain Disasters and Environment of the Chinese Academy of Sciences, said that the location of the dust cloud in the video matched the area identified as the place where the disaster occurred on August 26.

At 8:37 a.m. on August 26, seismic stations recorded a strong tremor of 5.2 degrees in the border area between Nepal and China’s Tibet region. This tremor was not actually caused by an earthquake, but from a giant block of ice with an area of ​​about 20 hectares, equivalent to 28 football fields, separating and falling from the peak of Langtang Lirung in the Himalayas to the valley below.

Satellite images show that a block of ice with a length of about 930 m, separated from a glacier on the slopes of about 5,200 m high mountain of Langtang Lirung, the 99th highest mountain in the world, immediately triggering a chain of disasters with fierce destruction.

“Basically, the lower part of the tongue of the glacier separated due to the collapse of the rock below. So, the glacier had nothing to lean on. That block of ice and rock freely fell 1,200 meters, forming a dam blocking the river. When the dam broke, the accumulated water overflowed, creating a flash flood,” said Jakob Steiner, a geologist at the University of Graz in Austria.

The flood flow rushed down the steep valley at a speed of more than 160 km/h, carrying gravel, rocks and large tree trunks, creating flood waves up to 21 m high. The speed of movement and destructive power of the flood was extremely fast. Just 13 minutes after the ice block incident, the water level monitoring station in Syabrubesi, Rasuwa was destroyed and stopped transmitting data.

At 9:05 a.m. the same day, authorities received information about a major flood on the Bhotekoshi River originating from Tibet. In just 30 minutes, the river water level rose to 9 m, the mixture of mud, rocks and ice swept away everything in its path.

Flash floods have flattened many towns in the border area, washed away bridges and roads and damaged large hydroelectric plants.

Nepali officials on August 29 announced that the number of deaths in the country after the flash flood was 669, along with 2,426 missing cases. China also recorded 7 deaths and 554 people missing in the disaster.