Glacier break or earthquake? What triggered the Nepal floods? | Explained

A catastrophic flash flood originating from the Bhote Koshi-Trishuli river system has claimed the lives of at least 389 individuals in Nepal and three in Tibet, leaving over 1,400 people missing. The disaster has displaced hundreds of people, forcing them to flee from affected regions including Rasuwa, Nuwakot, Dhading, Gorkha, and Chitwan.

In India, no fatalities have been reported, but 288 Indian nationals remain untraceable, with 84 successfully rescued. Authorities in Bihar and Uttar Pradesh are closely monitoring potential downstream flood risks.

Initial assessments suggest that the trigger for the disaster was not heavy rainfall, but rather the sudden and massive collapse of ice and rock high in the Himalayas near Langtang Lirung. This massive chunk of glacial ice, rock, and debris, which fell from an elevation of approximately 5,200 meters, plummeted about 1,200 meters down the Lhende Khola system, gathering additional rock, sediment, ice, and water along the way. This gathering force transformed the falling mass into a fast-moving debris flow.

The debris flow initially obstructed the river, subsequently releasing a surge that swiftly traveled downstream through the Bhote Koshi and Trishuli systems. This destructive force reached communities located nearly 100 kilometers away, causing widespread destruction to roads, bridges, homes, and hydropower infrastructure. Rescue, search, and relief operations are currently underway, as authorities try to contain the aftermath of this natural catastrophe.