On Wednesday, part of a glacier collapsed high in the Himalayas, triggering catastrophic flooding along the Nepal-Tibet border. At least 160 people have been confirmed dead, while nearly 1,500 people are missing across Nepal and China’s Tibet. In Nepal, 826 people are missing, including almost 600 foreign tourists, according to police and tourism officials.
Across the border, Chinese state media reported that 558 people were missing in Tibet’s Gyirong County, including 260 foreign nationals. Here is what we know about what triggered the disaster, where the floods struck, and the risks facing the rapidly warming Himalayan region. At about 8:40am local time ( ) on Wednesday, flash floods and mudslides swept through mountainous areas along the Nepal-Tibet border, killing at least 157 people in Nepal and three in Tibet and leaving nearly 1,500 people missing across the region.
A massive flood of water, mud and rocks swept through the Lhende Khola river valley, engulfing villages and destroying homes and critical infrastructure. At least 19 bridges and about 40km (25 miles) of roads were washed away. Nepalese soldiers and rescue teams have been deployed with helicopters, drones and search dogs, but high river levels, damaged roads and mud have complicated efforts to reach some of the worst-hit areas.
Across the border in Tibet, deep sediment has also delayed Chinese rescue teams trying to reach the border zone. Officials were caught off-guard by the floods on Wednesday because it was not raining, according to local news editors. The disaster appears to have begun high in the Himalayas, where part of a glacier collapsed, triggering a chain of events that caused a powerful surge of water and debris downstream.
Satellite imagery showed that a substantial section of the lower end of the glacier broke away at an elevation of about 5,200 metres (17,000 feet), plunging about 1,200 metres (3,900 ft) onto the valley floor, gathering rock and sediment as it fell. The resulting ice-rock avalanche struck the Lhende River in Tibet, about 20km (12 miles) northeast of the Nepal-China border crossing. Debris temporarily blocked the river before the natural dam gave way, releasing a powerful flood downstream.
Early reports suggested that a magnitude 4.4 earthquake had triggered the collapse. However, the United States Geological Survey (USGS) later revised its assessment, saying that the seismic signal had been generated by the landslide itself rather than an earthquake. The landslide eventually registered as a magnitude 5.2 seismic event.
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