Nepal's Deadly Floods Traced to a Glacial Collapse, Not an Earthquake

Flash floods and a landslide along the Nepal-Tibet border have killed at least 165 people and swept away entire villages. Experts say the exact cause is not yet certain, but the risks are compounded by extreme topography and are rising because of climate change.

Nepal's Foreign Minister Shishir Khanal initially said an earthquake triggered a landslide that blocked a river, sending water gushing downstream once the blockage breached. But the US Geological Survey (USGS) later said that while the event was first reported as a magnitude 4.4 earthquake, further analysis of long-period seismic waves showed the seismic energy was instead generated by a glacial collapse and debris flow.

One hazard experts point to is a glacial lake outburst flood, or GLOF: the sudden, catastrophic release of water from a melting glacier-fed lake. Dorothy Heinrich, a researcher at the UK's University of Reading, said such floods are among the hazards of a warming planet in the region, with high confidence of more heat waves, glacial retreat and permafrost loss in the Himalayas driving landslides and GLOFs. A previous GLOF in July 2025 originated in China's Gyirong County and surged into Nepal's Rasuwa District.

A preliminary assessment by the Kathmandu-based International Centre for Integrated Mountain Development (ICIMOD) found no anomalies on the Chinese side of the border. Sarthak Shrestha, a remote sensing analyst with ICIMOD, said the team believes a rock-ice avalanche in Nepal blocked the Lhende River, causing the cascading flood.

Hatim Sharif, a hydrologist at the University of Texas San Antonio, said the lack of rainfall beforehand defeated nearly every flood warning system in the world, since running or driving away would not help once the fast-moving mud and water arrived. He said climbing at least 20 feet (6 meters) up a hill was the only solution, and that river-level gauges could eventually give residents 20 to 30 minutes of warning. Qianggong Zhang of ICIMOD warned of the potential for a second flood because of an ongoing blockage upstream.