Catastrophic flash floods near the Nepal–Tibet border have caused widespread destruction, with more than 330 people reported dead and over 1,500 missing. The missing and deceased reportedly include 65 people from the United States, according to Nepali authorities and Chinese state media. The disaster followed a suspected glacier collapse early Wednesday, August 26.
Existing river gauge data indicates that the Trishuli River rose by about 30 feet (9 meters) in only 30 minutes. The rapid rise occurred near Gharchi, approximately 20 miles (33 kilometers) west of Nepal’s capital, Kathmandu, the International Centre for Integrated Mountain Development said.
Videos shared on social media show residents escaping a fast-moving wall of mud and water as it destroyed buildings and swept away a bridge. Authorities have warned people to stay away from the banks of the Bhotekoshi, Narayani—also known as the Gandaki or Gandak—and Trishuli rivers because of the continuing risk of flooding and debris flows.
Latest videos fromlive science
“Although this occurred during the peak of the monsoon season, it does not appear to have been triggered by heavy rainfall,” John Tunnicliffe, a river science researcher at the University of Auckland in New Zealand, said in a statement to the Science Media Centre. “Preliminary investigations instead point to a large-scale collapse of glacier ice and rock above the Rende Kola River.”
The collapse and resulting debris flow were powerful enough to initially be mistaken for an earthquake by the United States Geological Survey. The event registered as magnitude 5.2, but a USGS analysis of the resulting seismic waves indicated that the signal was caused by a glacier collapse and debris flow rather than tectonic activity.
Satellite imagery suggests that ice and rock from the collapse entered the Lende Kola River valley, which lies at approximately 17,060 feet (5,200 meters) above sea level, Tunnicliffe said. Scientists are investigating whether the debris temporarily blocked the river before unleashing a powerful surge downstream.
“This chain of events is what geomorphologists call a hazard cascade,” Tunnicliffe explained. “Instability on high-altitude, glaciated slopes can trigger ice-and-rock avalanches that dam rivers, collect water and sediment, and eventually become destructive floods and debris flows that travel tens of kilometers downstream.”
Get the world’s most fascinating discoveries delivered straight to your inbox.
Although these processes are well understood individually, their connection can turn a localized slope failure into a major disaster for communities far downstream. Tunnicliffe cautioned, however, that it is too early to attribute this specific glacier collapse entirely to climate change.
Rescuers use an excavator to transport survivors after flash floods and landslides in Devghat, Nuwakot district, Nepal, on August 26, 2026.
(Image credit: PRAKASH MATHEMA, via Getty Images)
“There is an important climate change context, but we have to be careful about attribution,” Tunnicliffe said. “We still don’t know why this particular glacier collapsed.”
“What we do know is that conditions across the Hindu Kush Himalayas are changing rapidly,” he added. “Glaciers are retreating, permafrost is deteriorating, new lakes are forming, and steep slopes are becoming more exposed and unstable. Climate change can increase existing hazards by changing the thresholds at which one process triggers another.”
The danger may continue after the initial flood surge. Sediment deposited by a debris flow can raise riverbeds, redirect waterways and create temporary dams, creating additional hazards in the days, weeks or even years after the original disaster.
Basanta Raj Adhikari, director of Nepal’s Disaster Research Center at Tribhuvan University, agreed that communities could face a “second or third wave” in the coming days, according to BBC News.
“We don’t know yet,” Adhikari warned. “It hasn’t been raining that much, but there may be landslides.” He said he was discussing the ongoing risks with Chinese colleagues monitoring conditions in the region.
Looking ahead, Tunnicliffe said the broader lesson is the need to manage connected hazards rather than treating each risk separately.
He said satellite monitoring of glaciers, lakes and mountain slopes should be combined with seismic sensors, river gauges and early-warning systems capable of detecting when a hazard cascade begins. Infrastructure, evacuation plans and land-use policies should also account for future flood and landslide risks.
For now, Tunnicliffe said, “Our thoughts are with the families of those killed and still missing, and with the agencies and communities in Nepal and China conducting the search.”
