More than 165 people have been confirmed dead, with thousands reported missing, in floods triggered by a significant glacial collapse near the Nepal-China border. Over 1,500 individuals are missing across Nepal and Tibet, including more than 800 foreign tourists, after flash glacial-lake outburst floods submerged towns and communities under mud and water. The death toll is expected to rise as rescue teams reach areas cut off by the floods, which have also devastated several key bridges and highways.
Initially, officials believed a magnitude 4.4 earthquake might have triggered the floods; however, experts and the United States Geological Survey confirmed that the seismic event was a result of a glacial collapse and debris flow that caused subsequent catastrophic impacts downstream.
A glacial collapse refers to the detachment of a large mass of glacier ice from its bed, which can involve millions of cubic meters of ice, rock, and water, transforming into a highly mobile ice-rich avalanche or debris flow. Although not a formally defined scientific term, it is widely used to describe such events.
An initial study using Planet Labs satellite imagery indicated that a landslide of ice and rock unleashed a flood in the Lhende River in Tibet, approximately 20 kilometers northeast of the Nepal-China border crossing in Rasuwagadhi, according to Nepal’s disaster management officials. Images from television showed collapsed homes, floating cars, and a metal bridge being washed away, with witnesses reporting that entire villages were engulfed.
The disaster affected the mountainous Nepal-Tibet border region, particularly in Nepal’s Rasuwa district, just south of the Chinese border. The initial surge entered the Lhende Khola, which feeds into the Bhote Koshi and then the Trishuli River, raising water levels in the Trishuli by as much as 9 meters (27 feet) in just 30 minutes.
Nepal’s National Disaster Risk Reduction and Management Authority stated that the “glacier-inclusive flood” occurred in the Lhende River due to an ice-rock avalanche on the Nepali side, according to geologist Prakash Pokharel. Vikram Gupta, an engineering geology specialist at Sikkim University in India, confirmed that a substantial portion of the glacier snout collapsed, likely including rock and sediment.
Earth scientist Dan Shugar from the University of Calgary noted that imagery suggested a significant amount of snow melted in the 24 hours before the disaster, with the lower part of a glacier breaking off at about 5,200 meters and crashing onto the valley floor approximately 1,200 meters below.
This incident occurs amid rapid warming and glacial loss across the Himalayas. Glaciers in the Hindu Kush Himalaya mountain range lost ice 65 percent faster between 2011 and 2020 than in the previous decade. According to the United Nations, Nepal’s glaciers have lost nearly one-third of their ice volume in about three decades due to global warming.
Survivor Keshav Prasad Baral, 68, described the disaster as a massive surge of mud approaching him. He attempted to save his wife, but she was swept away. Experts indicate it is too early to determine conclusively if global warming was the cause of the floods. Glacial lake outburst floods (GLOFs) are among the dangers associated with such events in the region’s extreme topography.
Dorothy Heinrich, a researcher at the University of Reading, emphasized that GLOFs are hazards posed by a warming planet in the region. Hatim Sharif, a hydrologist at the University of Texas San Antonio, noted the lack of rainfall before the floods, which undermines flood warning systems.
There have been several instances of glacial collapse in the last decade, which scientists consider unusual and rare. Tibet has been identified as a hotspot for significant glacier collapses, although their causes are site-specific. Notable past incidents include a 2016 glacier collapse in Tibet’s Aru Range that killed nine herders and hundreds of animals, and a 2018 event in India’s Uttarakhand state that resulted in over 200 fatalities.
In November 2022, about 40 million cubic meters of glacier ice detached from the Bukadaban Feng glacier in the Kunlun Mountains, creating a 13-meter (42-foot) high wave. In Switzerland, a 2022 collapse linked to climate change buried much of the village of Blatten.