A team of international scientists is investigating the cause of a flash flood that occurred Wednesday along the Nepal-China border, destroying infrastructure and causing multiple deaths. The investigation currently focuses on a large glacier collapse and landslide north of Kathmandu as the primary trigger for the disaster. While the exact causes are still being established, researchers have used satellite imagery to identify where a significant portion of a glacier detached from a mountainside.
The event began at 8:37 a.m. local time on Wednesday. The U.S. Geological Survey (USGS) initially recorded the shaking as an earthquake. The agency later clarified that the vibrations were caused by a glacier collapse and debris flow equivalent to a magnitude 5.2 earthquake. Satellite analysis shows a section of glacier roughly 2,000 feet wide sheared off and fell approximately 7,000 feet to the river below.
Geologists believe the falling ice may have coincided with a landslide, creating a cascade of rock and ice that entered the Lhende Khola River. Jeffrey Kargel, a senior scientist at the Planetary Science Institute, reported that the flood wave traveled the first 13.7 miles at an average speed of 120 mph, covering that distance in less than seven minutes. Daniel Shugar, a geologist at the University of Calgary, noted that the force of the collapse likely melted the ice and picked up waterlogged sediment, contributing to the volume of the flood.
The scale of the event involves a debris flow that moved at 120 mph, leaving little time for evacuation once the collapse occurred. Scientists such as Wouter Buytaert of Imperial College London stated that global warming shrinks glaciers, making it more likely for them to break apart, noting that ice loss rates in this region have doubled since 2000. For the local population, this translates to a risk of "hazard chains" where a landslide or glacier shear can transform into a catastrophic flood wave.
As of late August, scientists are continuing to analyze satellite data to reconcile the volumes of water observed in the flood with the estimated size of the glacier chunk. The immediate focus for authorities is the impact on the Rasuwa municipality, located approximately 13 miles downstream from the start of the landslide. Future policy and safety measures in the region may be informed by these findings, though specific dates for the completion of the full scientific report were not provided.