On August 26, devastating flash floods tore through communities near the border between Nepal and China-governed Tibet, washing away buildings, bridges and roads. The Nepal Tibet floods have killed more than 900 people and left nearly 5,000 missing as of August 31, according to authorities.
“It was a huge gush of mud coming straight towards us,” said 68-year-old survivor Keshav Prasad Baral to reporters. “My wife is still somewhere beneath the mud. She’s gone.”
Researchers are working to determine what set off the disaster and whether similar events are likely in the future. Here is what scientists have established so far.
Nepal Tibet floods: what caused the flooding?
The U.S. Geological Survey reported on August 27 that an event inside Nepal’s Lāṅṭāṇ National Park in the Himalayas triggered the deluge. The agency said either a landslide incorporating a glacier or a failure in which part of a glacier broke away produced energy equivalent to a magnitude 5.2 earthquake, sending debris downslope and unleashing the floods.
Many natural hazards specialists favor the landslide explanation. Researchers who reviewed the physics of a pure glacier collapse said the mechanism did not add up, and satellite imagery captured on the evening of August 26 showed a denuded mountainside consistent with a massive slide, according to scientists analyzing the event. As one seismologist put it, the glacier likely “came along for the ride.”
Where the immense volume of water originated remains uncertain. Early speculation focused on a glacial lake outburst, but satellite and weather data did not indicate the formation of any large lakes in the area, experts said.
Several researchers now suggest the cascading ice and sediment picked up river water as it raced downhill. The USGS said the glacial debris entrained rock and water, creating a debris flow and flood that traveled roughly 62 miles.
One geologist described it as an almost unbelievable amount of water, noting that pinpointing its exact source is one of the hardest aspects of the investigation.
Did climate change play a role?
No formal attribution study has been completed, but scientists note that human-driven warming is destabilizing Himalayan glaciers on some of the world’s steepest terrain. Several researchers said climate change has made such hazards more likely.
Glaciers across the region are losing ice at unprecedented rates, and the permafrost beneath them is thawing. As that frozen mix of soil, rock and organic matter warms, slopes and overlying ice become less stable. Experts say this can produce large landslides that set off cascading processes leading to destructive floods downstream.
Recent research indicates that even if global warming is limited to about 2.7 degrees Fahrenheit above pre-industrial levels, Earth could still lose roughly half of its 200,000 glaciers by 2100. Scientists warn that events like the Nepal Tibet floods are likely to become more frequent as the planet heats up.
Nepal’s foreign minister has urged a global effort to protect the Himalayan ecosystem, noting the country contributes little to greenhouse gas emissions yet faces severe impacts. Researchers also called for measures to reduce risk and bolster resilience for mountain communities that are increasingly exposed to such disasters.
What comes next?
Rescue operations continue, and authorities say it could take weeks to recover victims. Responders are struggling to reach survivors stranded on rooftops, and hundreds of workers remain trapped in hydropower tunnels.
A cleanup expected to last months will follow. Some families may never recover the remains of loved ones, which may have been carried as far as India, according to officials.
Nepali authorities estimate reconstruction will cost between 4 billion and 5 billion dollars, roughly a tenth of the nation’s economy. Similar large-scale recovery challenges have followed other major disasters, including high-profile incidents such as the Vienna museum diamond theft, which also carried multimillion-dollar consequences.