Scientists Probe Ice-Rock Avalanche Link to Nepal Flash Flood

Scientists are investigating whether a high-altitude ice-rock avalanche set off the catastrophic flash flood and mudslide that struck Nepal's Rasuwa district on Wednesday, near the Tibet border. The International Centre for Integrated Mountain Development (ICIMOD), alongside partner institutions in Nepal and China, is leading the inquiry.

Preliminary assessments, based on video footage and field reports, suggest a large volume of ice and rock debris may have plunged into the Lende Khola, a tributary of the Bhote Koshi river. This event could have generated a sudden surge that carried water, sediment, and massive boulders downstream, overwhelming the Bhote Koshi and Trishuli rivers.

Seismic records from the disaster period show unusual signals, though no direct causal link between seismic activity and the flood has been established. The event's exceptional speed and magnitude have drawn particular concern, with water levels reportedly rising by up to nine metres at Galchhi and seven metres at Malekhu within 30 minutes. Both locations are in Dhading district, roughly 80 kilometres from Kathmandu.

ICIMOD officials warn that a blockage remains lodged upstream on the Nepal-China border. This has prompted evacuation orders for the Jilong port area, as authorities fear a second flood could be imminent. Experts are also assessing whether debris temporarily dammed the river at a narrow section, creating a landslide dam that could release impounded water suddenly, posing a secondary hazard.

Qianggong Zhang, Head of Climate and Environmental Risks at ICIMOD, noted that the same site devastated by last year's Rasuwa flood is under threat again. While an ice avalanche in the Lhende Khola is the suspected trigger, the cause remains unconfirmed. An ice avalanche involves the sudden collapse and downhill movement of a large ice mass from a hanging glacier or ice-covered mountain.