Hundreds of people have been killed or remain missing following a powerful flash flood on the Nepal-Tibet border that destroyed homes, swamped roads, and swept away bridges. Nepali officials reported that emergency services have recovered the bodies of at least 332 people, with over 800 still unaccounted for. In China-controlled Tibet, 558 people are reported missing and three have died.
The disaster was triggered by a large chunk of glacier that collapsed from an estimated height of 5,200 meters (about 17,600 feet) into a valley, according to Simon Cox, principal scientist at New Zealand's GNS Science. This collapse transformed into a "raging mass of debris" that picked up rocks, sediment, and trees as it moved down the canyon, creating a wall of water that first hit a border post and then traveled downstream into Nepal.
The glacial collapse was powerful enough to register as a seismic event, initially mistaken for an earthquake. The U.S. Geological Survey later determined the seismic activity was a glacial collapse and debris flow. The event registered as a 5.2-magnitude seismic event at 8:37 a.m. local time on August 26, 2026.
Astonishing footage captured by survivors shows the devastating impact of the flood. One video from a town situated in a valley shows a massive boulder, described as bus-sized, slowly rolling through deep, muddy water. Horrified onlookers filmed the boulder as it passed their homes, alongside footage documenting the destruction.
Other clips depict workers near a river fleeing for their lives from the approaching surge. Men in high-visibility jackets and hard hats can be seen scrambling to higher ground as the water violently crashes and a plume of water flies into the air.
In riverside villages, residents watched in horror as a tsunami-like wave thundered towards their homes. The river quickly burst its banks, carrying debris and flooding nearby farms with thick sludge.
In more populated towns, water rose rapidly, surging over bridges. Panicked drivers were heard blaring horns as they attempted to escape, but within seconds, bridges were swept away by the sheer force of the water. Houses were left partially submerged and deluged in mud.
Experts are working to reconstruct the disaster using satellite imagery and ground measurements, as the affected area is largely inaccessible. The volume of the collapsed glacier could range from half a million to tens of millions of cubic meters, according to Cox. Lauren Vargo, a glaciologist at New Zealand's Victoria University of Wellington, explained that comparing satellite imagery from before and after the event helps determine the scale of the collapse.
Soon after the seismic activity, a nearby water monitoring station stopped transmitting, followed by others downstream. Water levels reached up to 12.3 meters in Kalikhola, near the Tibet border, by 2:14 p.m. on August 26.
Initial speculation suggested a glacial lake outburst flood (GLOF), a risk exacerbated by melting glaciers due to climate change. A GLOF occurs when a debris wall holding back a glacial lake collapses. While some experts suggested this possibility, others noted the absence of known glacial lakes near the collapse site, theorizing that water collected beneath the glacier may have cascaded down with the falling ice. The falling ice could have also briefly dammed the river, leading to a subsequent release of water. Factors like summer glacier melt and monsoon rains had already raised river levels, and the debris flow further swelled the water volume.
Nepali authorities issued warnings around 9:00 a.m. local time, alerting areas along the Bhote Khoshi river to stay on high alert. However, it remains unclear how many received the warning or had sufficient time to respond.
Experts emphasize that the risk of such events is increasing as glaciers retreat globally. While individual glacial events are difficult to directly attribute to climate change, a warming planet is considered a background stressor on glaciers. Reducing greenhouse gas emissions is seen as the primary way to mitigate these risks, according to Vargo. Hydrologist Hatim Sharif noted that in the face of such a high-speed mud and water flow, fleeing by running or vehicle is largely ineffective, with climbing to higher ground being the only viable option for survival.