Ice-rock avalanche may have triggered Nepal flash flood, say scientists

Scientists from the International Centre for Integrated Mountain Development (ICIMOD), in collaboration with partners in Nepal and China, are examining whether an ice-rock avalanche on the Nepal-Tibet border could have triggered a devastating flash flood and mudslide. On Wednesday morning, the floods swept through Nepal's Rasuwa district, originating downstream of Tibet.

The surge was reportedly fueled by a significant volume of ice and rock debris entering the Lende Khola, a tributary of the Bhote Koshi river, according to preliminary assessments based on video footage and reports from affected areas.

Rescuers, using earthmoving equipment, struggled to reach submerged homes in the affected areas. ICIMOD reported that early analysis of seismic records revealed unusual signals during the disaster, though no direct causal link has been established between seismic activity and the floods. Qianggong Zhang, Head of Climate and Environmental Risks at ICIMOD, highlighted that the same site impacted by last year's Rasuwa flood is now under threat once again.

Authorities warned of the possibility of another flood imminent due to a blockage on the Nepal-China border, leading to the evacuation of residents near Jilong port.

An ice avalanche refers to the sudden collapse and downhill movement of a substantial mass of ice from either a glacier or an ice-covered mountain. ICIMOD emphasized the 'exceptional speed and magnitude' of the recent flood, noting that water levels rose as much as 9 meters in Trishuli river at Galchhi and by seven meters at Malekhu within 30 minutes.

These locations are approximately 80 kilometers from Kathmandu. Experts are currently investigating whether debris temporarily blocked the river, creating a landslide dam that could release a secondary hazard if the impounded water is suddenly released.