What Triggered the Devastating Floods in Nepal and Tibet, and Are We Due for More in the Future? Here's What Scientists Know So Far

On August 26, devastating flash floods washed away buildings, bridges and other infrastructure near the border between Nepal and China-governed Tibet. The natural disaster has killed more than 900 people and left nearly 5,000 missing as of August 31, according to authorities. She’s gone.” But what caused the catastrophic event, and could more like it happen in the future?

Scientists are still putting the pieces together. Here’s what they know so far. Geological Survey’s August 27 update, an event in Nepal’s Lāṅṭāṇ National Park in the Himalayas triggered the flooding.

The agency says that either a landslide carrying a glacier or a glacier collapse, in which part of it snaps off, may have generated the energy equivalent to a magnitude-5.2 earthquake. Then, debris tumbled downward and triggered the floods. Many scientists are heavily leaning toward the landslide explanation.

The physics of the glacier collapse hypothesis didn’t hold up, according to some natural hazards researchers in a Slack group analyzing the event, reports Science’s Hannah Richter. What’s more, satellite images obtained the evening of August 26 show a bald mountain, hinting at a giant landslide. However, experts still aren’t sure where all the water came from.

At first, scientists thought that a glacial lake had collapsed, but satellite imagery and weather data didn’t suggest any big ones were forming in the region, Ekström tells Mohana Basu at Nature. It’s more likely that the rush of ice and sediments from the landslide accumulated river water as it barreled downstream, Kristen Cook, a geomorphologist at Grenoble Alpes University in France, tells Science. The USGS says the glacial debris picked up rocky material and water as it sped downhill, generating a debris flow and flood that traveled around 62 miles.

It’s “just a gobsmackingly unbelievable amount of water,” says Daniel Shugar, a geologist at the University of Calgary in Canada, to Laura Paddison, Angela Fritz and Ivana Kottasová at CNN. Not only are thousands of glaciers losing ice at unprecedented rates; the permafrost they sit atop is also thawing. As that frozen blend of soil, rocks and organic material warms, the mountains and surrounding ice become less stable.