The death toll from the catastrophic Himalayan flash floods rose to at least 359 in Nepal on Thursday as rescuers searched shattered villages and riverbanks for more than 1,000 people missing across Nepal and neighbouring Tibet.
Scientists meanwhile increasingly pointed to the collapse of a high-altitude glacier as the trigger for one of the region’s deadliest floods in recent history.
Nepal Police said bodies had been recovered across eight districts, including 132 in Chitwan, 82 in Nawalparasi East, 33 in Dhading and 28 in Nuwakot, The Kathmandu Post reported.
Bodies have been carried more than 100 kilometres downstream from the mountainous disaster zone, illustrating the extraordinary force of the flood.
The catastrophe began Wednesday morning when a vast mass of ice, rock and sediment collapsed high in the Himalayas and crashed into a mountain river system, generating a fast-moving wall of mud, water and debris that swept through the Nepal-Tibet border region and raced south through Nepal.
The flood devastated communities along the Bhotekoshi and Trishuli rivers, destroying houses, roads, bridges and hydropower facilities. Helicopters were being used Thursday to search inaccessible valleys, evacuate survivors and deliver supplies to communities cut off by destroyed roads.
Hundreds of foreign tourists and pilgrims are among those unaccounted for. Reuters reported that the missing in Nepal included 288 Indians, 63 Americans, 51 Malaysians, 34 Australians, 33 Britons and 25 Canadians. In Tibet's Gyirong County, Chinese state broadcaster CCTV reported 558 people missing, including 260 foreign nationals.
Many were travelling through the border region towards Mount Kailash, the sacred pilgrimage destination in Tibet.
The scale of destruction was particularly bewildering because the flood did not follow the sort of intense local rainfall normally associated with Himalayan flash floods.
On Wednesday, Rasuwa's chief district officer Narendra Pariyar told The Kathmandu Post that there had been no rain around the district headquarters and the sun was shining when the flood arrived. Officials initially wondered whether a glacial lake had burst somewhere upstream.
Evidence gathered since then points towards a different and more complex chain of events.
Scientists believe a huge ice-and-rock avalanche occurred high in the mountains, sending debris into the Lhende river system. The material may have temporarily blocked the river before the natural barrier failed, unleashing an enormous surge downstream.
The Kathmandu Post reported that satellite imagery appeared to show a major avalanche about 20 kilometres northeast of the Rasuwagadhi border crossing. Nepal's National Disaster Risk Reduction and Management Authority has identified an ice-and-rock avalanche as the leading explanation.
Scientists at the International Centre for Integrated Mountain Development, or ICIMOD, said preliminary evidence suggested a huge volume of ice and rock fell into the river and may have created a temporary landslide dam.
The flood that followed was extraordinarily violent. At Galchhi, the Trishuli rose by as much as nine metres in just 30 minutes, while at Malekhu the river climbed roughly seven metres over the same period, according to ICIMOD figures cited by The Kathmandu Post.
Early reports suggested that a magnitude-4.4 earthquake might have caused the disaster. But the US Geological Survey later concluded that the seismic signal initially interpreted as an earthquake was actually generated by the enormous collapse of glacial rock and ice and the subsequent debris flow.
Reuters reported that Chinese government geologist Guo Zhaocheng estimated the avalanche-driven debris flow travelled at about 50 metres per second and extended for more than 20 kilometres.
Chinese authorities have also identified a high-altitude glacier collapse as the cause, according to state news agency Xinhua.
The immediate danger may not be over. Nepal's disaster management authorities said satellite imagery indicated that another blockage had formed along the Bhotekoshi, creating a lake and raising fears that its failure could produce another sudden flood.
Scientists caution that the precise sequence is still being reconstructed. The wider Himalayan region, however, is experiencing rapid glacier retreat, making unstable slopes, glacial lakes and cascading mountain hazards an increasing concern.
Al Jazeera reported that glaciers across the Hindu Kush Himalaya lost ice 65 percent faster between 2011 and 2020 than during the previous decade. Researchers have not yet established a direct link between climate change and this particular collapse.
Behind the mounting national death toll are communities that were effectively erased within minutes.
The devastation was described in extraordinary personal detail by The Kathmandu Post journalist Arjun Poudel, whose childhood village of Sole and nearby Betrawati were overwhelmed.
Poudel wrote that Sole sits nearly 100 metres above the riverbed and that no flood in living memory had reached it. Yet photographs and videos reaching him showed the settlement devastated. Several members of his extended family were swept away.
A local teacher told him that about 90 percent of houses in Betrawati had disappeared. Bridges were swept away, roads vanished and electricity and communications collapsed. Rasuwa was effectively severed from Nepal's road network, leaving villages without practical access to hospitals or markets.
The flood also destroyed historic and religious landmarks around Betrawati, including an area associated with the peace treaty between Nepal and Tibet. Entire agricultural fields disappeared, while surviving families were left without functioning mills to process stored grain.
Despite the enormous scale of the emergency, Nepal has declined offers from several governments to deploy foreign search-and-rescue teams.
The Kathmandu Post reported Thursday evening that India, China, the United States, Britain, Japan, South Korea, Sri Lanka and Bangladesh had offered or sought permission to send rescue personnel. Kathmandu told them Nepal's army, police and other security agencies could manage the operation.
The decision was partly shaped by Nepal's experience following the devastating 2015 earthquake, when the arrival of numerous foreign rescue teams created coordination and management problems, a senior foreign ministry official told the newspaper.
India had specifically sought permission to deploy its National Disaster Response Force but the request was declined. Nepal is instead asking international partners to channel financial assistance through the Prime Minister's Relief Fund.
India has already delivered more than 47.5 tonnes of relief supplies and offered temporary bridges, while the United States, Britain and the World Bank have announced financial support.
Nepal's Foreign Ministry has established an Emergency Response Team to coordinate information about missing foreigners as embassies and families seek information about hundreds of people who remain unaccounted for.
More than 5,000 Nepali army and police personnel have been mobilised, according to Al Jazeera, with helicopters, drones and search dogs being deployed where terrain permits.
The search is increasingly extending far beyond the original disaster zone.
In Chitwan alone, authorities had recovered more than 100 bodies carried downstream through the river system. Hospitals there were struggling to accommodate the dead, forcing authorities to prepare temporary facilities where relatives could identify and claim bodies.
With hundreds still missing, officials warned that the toll could rise considerably.
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