빙하가 강물 막았다 터지면서 대재앙...수위 30분 만에 9m 상승

A massive glacial landslide triggered by the collapse of a giant ice and rock mass from 7200-meter-high Langtang Lirung mountain in the Nepal-Tibet border region caused catastrophic flooding on June 26. The initial flood could have been triggered by the damming of water by the ice and rocks, causing a dam break and a "compound disaster" as floodwaters and debris flowed downstream.

This early analysis was based on satellite imagery from Planet Labs. According to experts, the glacier's terminus disintegrated from an altitude of about 5200 meters, causing a massive "glacier-avalanche" that swept away surrounding rocks and soil. The landslide began at the northern slope of Langtang Lirung, roughly 45km north of Kathmandu in the Reamdo River.

It is estimated that this landslide blocked the Leden River, temporarily blocking the waterway. Experts said that the water flowed over the natural dam created by the ice, rocks, and soil, and then burst when the dam broke, releasing a massive amount of water, soil, and rocks. The water then flowed downstream along the Tamur River and Trisuli River.

The International Center for Integrated Mountain Development (ICIMOD), based in Kathmandu, reported that the speed and scale of the flood were unprecedented based on hydrological observations. The Trisuli River downstream experienced a water level rise of up to 9 meters within 30 minutes. Authorities and experts warned that the presence of ice and soil on the upstream side could lead to secondary flooding, and they evacuated residents.

The US Geological Survey (USGS) initially reported a magnitude 4.4 earthquake at the site of the disaster but later revised it to a 5.2 magnitude seismic event caused by the landslide. The explosive glacial and rock collapse appeared to generate seismic signals, according to experts. The cause of the initial glacial collapse is still unclear.

Daniel Shugar, a professor at the University of Calgary, noted that the snow covering the glacier was largely melted during the 24-hour period before the event, as confirmed by satellite imagery. The overlying permafrost was thawed, and the ice sheet's transport of rocks and soil had become loose, increasing the risk of collapse due to heavy snowfall and melting permafrost.

The United Nations reported in 2023 that Nepal lost about one-third of its glaciers over the past 30 years. Greenland's glaciers have been melting at a rate 65% faster than the previous decade. However, the International Center for Integrated Mountain Development stated that it is still too early to determine the impact of climate change on this glacial collapse.

Langtang Lirung experienced a 7.8 magnitude earthquake in 2015, causing a glacial landslide in the south that submerged the Langtang village and killed around 300 people, as well as flash floods in July caused by melting glacier surfaces and combined ice flows. This latest disaster has left at least 165 dead and over 1300 missing in Nepal and Tibet Autonomous Region.

At least 19 bridges and 40 kilometers of roads were destroyed, with at least 6 power stations and 6 major hydroelectric facilities damaged or severely affected.