Satellite images have captured the horrifying scale of the devastation caused by the flash floods in Nepal.
The floods on Wednesday occurred when a part of a Himalayan glacier broke away and crashed hundreds of metres down into a valley.
The floods swept away several towns and villages, killed at least 489 people and left nearly 900 missing in Nepal and across the border in China’s Tibet region. More than 30 British nationals are among hundreds of foreigners missing.
On Thursday, the authority said 517 foreign nationals were still out of contact.
The toll was expected to rise as emergency workers used helicopters to search for survivors and airdrop supplies to thousands of people cut off by fallen bridges and washed-away roads.
“We have resumed the search and more bodies are expected to be recovered," police spokesperson Abi Narayan Kafle said. There were at least 826 people missing in Nepal alone, officials said, and about 500 of them were foreigners.
Officials have warned of a possible further flooding risk from a lake of rising water at the flood site along the China-Nepal border.
China has warned that a barrier lake formed at the confluence of the Tsogyal and Purupqiangzangbu rivers is overflowing and could burst.
Authorities said the floods particularly devastated a rugged mountainous region thronged by trekkers and pilgrims.
Preliminary before-and-after satellite images of the region from Planet Labs show lush mountainsides buried under debris and sediment.
“It’s confirmed that a substantial portion of that glacier snout collapsed to initiate the event, probably including or entraining a fair amount of rock and sediment," Vikram Gupta, at specialist in engineering geology at India's Sikkim University, said.
Satellite imagery confirmed that a large amount of snow had melted in the 24 hours before the floods struck, Dan Shugar, earth scientist at the University of Calgary, said. “Some of the glaciers in the valley were covered in snow yesterday and today they are mostly bare ice. So in other words, it was probably warm.”
"What I can see in this morning’s satellite imagery from Planet Labs is that the lower part of a glacier broke off at about 5,200 metres and crashed onto the valley floor about 1,200 metres below,” he told Reuters.
The International Centre for Integrated Mountain Development noted that the floods sent a powerful surge of water, sediment and boulders down the Bhote Koshi and Trishuli river systems. This led to the water levels rising as much as 9m within 30 minutes in the Galchhi area downstream.
As a result of global warming, the UN said in 2023 that Nepal’s mountains had lost close to a third of their ice in just over the previous 30 years.
It added that glaciers in Nepal – wedged between two of the world’s largest carbon emitters in India and China – had melted 65 per cent faster over the last decade than in the one before.
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