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Glacier collapse caused Nepal’s deadly flash flood — a sign of things to come?
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Houses are partially submerged in muddy water following flash floods in Nepal.Credit: Prabin RANABHAT/AFP via Getty
Around 350 people have died and more than 1,000 are missing, after a deadly deluge of rocks, mud and water hit villages along the border of Nepal and Tibet on Wednesday. The US Geological Survey says the event was caused by a glacial collapse that led to a massive landslide and flash flooding.
The ice and rock collapse was strong enough to cause a 5.2-magnitude seismic event and send a massive wall of water downstream into the Bhotekoshi River system, along which tens of thousands of people live.
Scientists say it will take time to establish the extent to which global warming had a role in this glacial collapse. But melting glaciers and permafrost — frozen soil and rocks — in the Himalayas probably contributed to the event, says Göran Ekström, a geophysicist at Columbia University in New York City.
Global warming is affecting the high-altitude regions across the world, says Alton Byers, a mountain geographer at the University of Colorado, Boulder. “These catastrophic floods are becoming more frequent,” he adds.
The disaster struck the Rasuwa district in northern Nepal, which shares a border with Tibet. Videos circulating on social media show water, mud and debris crashing into multistorey buildings.
Authorities initially thought that an earthquake had caused the flooding. But the US Geological Survey later announced that the landslide generated the seismic energy and no earthquake had occurred.
The huge amount of water also led to initial speculation that a glacial lake had collapsed. Glacial lake outburst floods occur when a natural dam holding a lake in a high-altitude mountainous region suddenly gives way, leading to a deluge downstream. With climate change, growing numbers of such lakes are a major cause for concern for flash-flooding events. An estimated 15 million people globally are at risk of glacial lake flooding1.
But Ekström says that satellite images from before the ice landslide do not show any major lakes forming in the area. Weather data also did not record excessive rainfall preceding the landslide, he adds.