Glacial Collapse Triggers Massive Flood in Nepal, Killing at Least 160

A catastrophic flood surged through Nepal and the Tibet border region on August 26, following a massive glacial and rock collapse on Langtang Lirung mountain. The disaster, initially analyzed as a complex event involving a glacial-rock avalanche, has claimed at least 160 lives and left hundreds missing across both Nepal and Tibet.

Satellite imagery suggests a portion of the glacier at an altitude of approximately 5,200 meters broke off and plunged into the valley below. This event, occurring on the northern slope of Langtang Lirung, is believed to have triggered an avalanche of ice, rock, and debris that temporarily dammed the Lende Khola river, a tributary of the Bhote Koshi river. The subsequent failure of this natural dam released a torrent of water and sediment, which flowed down the Bhote Koshi and Trishuli rivers.

In the "Gyalchi" area downstream on the Trishuli river, water levels rose dramatically, surging by up to 9 meters in just 30 minutes. The US Geological Survey initially reported a magnitude 4.4 earthquake at the time of the incident but later revised it, suggesting the seismic signal was likely caused by the massive landslide. Investigations are ongoing into the exact cause of the initial glacial collapse, with some experts pointing to significant snowmelt in the hours preceding the event and the potential destabilization of moraine deposits due to glacial retreat.

The United Nations has noted that Nepalese glaciers have lost about a third of their ice in the last 30 years, with the melting rate accelerating. Langtang Lirung itself was the site of a devastating avalanche in 2015 following a major earthquake, which buried the village of Langtang and killed around 300 people. Last year, a glacial lake outburst flood on the Lende Khola river resulted in 18 fatalities. The current disaster has led to the destruction of at least 19 bridges and approximately 40 kilometers of road, along with significant damage to at least six hydropower plants and transmission facilities.

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The hydrological observation confirmed the unusual speed and scale of this flood wave.