The devastating Bhotekoshi flood struck the mountainous Nepal-Tibet border region, with some of the worst damage in Nepal’s Rasuwa district, immediately south of the Chinese border. Television images showed collapsed homes, floating cars and a metal bridge being washed away, while witnesses said the waters engulfed entire villages.

What Happened?

Officials initially believed that a magnitude 4.4 earthquake could have triggered the downstream floods on Wednesday morning. However, several experts and the United States Geological Survey have confirmed that “the seismic event” was a consequence of “a glacial collapse and debris flow that caused subsequent catastrophic impacts downstream”, rather than the other way around.

A glacial collapse is the detachment of a large mass of glacier ice from its bed – sometimes involving millions of cubic metres of ice, rock, and water – that can transform into a highly mobile ice-rich avalanche or debris flow. This collapse is not a formally defined scientific term in glaciology, but is widely used to describe the event.

Nepal’s National Disaster Risk Reduction and Management Authority said the “glacier-inclusive flood” occurred in the Lhende Khola (river) due to “an ice-rock avalanche on the Nepali side”, according to Prakash Pokhrel, a geologist at the authority. The initial surge entered the Lhende Khola — which feeds into the Bhotekoshi and then the Trishuli rivers, carrying floodwaters south through Nepal; Water levels in the Trishuli reportedly rose by as much as 9 metres (27ft) in just 30 minutes.

Victims and the Missing

According to Nepalese police, the death toll from the floods as of Friday morning rose to 469 people, though At least three people have also died in the neighbouring Tibet region. Official nationality counts for the dead are still pending.

Nepalese daily The Kathmandu Post reported that the bodies of the dead swept away by the floods are turning up far downstream, and local morgues are running out of space to store the bodies until they are identified. But authorities have begun finding alternatives, like using buildings in the country’s health and science academies as temporary morgues.

As the death toll continues to rise, the Post also reported on Friday that authorities in Nepal are working on solutions to bury unidentified bodies by assigning a tag number to each body, which will retain burial information. As of Friday morning, more than 1,500 people were missing in Nepal and China’s Tibet region.

According to Nepal’s Department of Tourism, 668 tourists from 34 countries had been out of contact since Wednesday morning, most of them on trekking expeditions; Among them, at least 177 are from India, 90 from the United States, 34 from Australia, 33 from the United Kingdom, and 25 from Canada. Beijing’s Foreign Ministry also said 100 Chinese nationals were among the missing in Nepal.

Many of the Indian nationals, and some from the US and Europe, but of Indian origin, were on their way to Tibet for the Kailash Mansarovar Yatra, a popular Hindu pilgrimage to a peak and lake sacred to Hindus, Buddhists and Jains. In Tibet’s Gyirong county, 558 people are reported missing, including 260 foreign nationals, according to Chinese state broadcaster CCTV.

Rescue Efforts and International Support

Rescuers in Nepal have deployed helicopters to search for survivors and drop emergency supplies to thousands of people cut off in a rugged mountainous area popular with trekkers and pilgrims travelling between Lhasa in Tibet and Kathmandu. But search and rescue operations are proving to be a “massive challenge”.

“Getting to the affected areas … to try and recover the survivors” is proving to be extremely difficult, because the roads and bridges there have suffered extensive damage, said Al Jazeera’s Minelle Fernandez, reporting from the Nepalese capital, Kathmandu. A mix of government and private helicopters have “been drafted to fly into the areas to try to bring as many survivors as possible” to hospitals to receive treatment for injuries that doctors say include broken ribcages and skin burns, said Fernandez.

Army spokesperson Raja Ram Basnet said helicopters were dropping tents, food and medicine, provided by neighbouring India, into the hardest-hit districts; more than 5,000 army and police rescue personnel have joined the rescue effort, he said. On Friday, Nepal News also reported that the army had rescued 350 workers and residents trapped in a tunnel at the Upper Trishuli hydropower project, working in poor weather and high river flows.

Nepal’s Prime Minister Balendra Shah left by road for Bidur in one of the worst-affected districts of Nuwakot to assess the flood situation, his office said on social media. Meanwhile, India evacuated thousands of people from its northern states bordering Nepal, including Bihar, Uttar Pradesh and Uttarakhand, as the floods threatened the Gandak River Basin.

Chinese Premier Li Qiang also visited the mudslide site in Tibet on Thursday afternoon to “guide emergency rescue and relief work” a day after the disaster, state media reported. United States President Donald Trump said Washington had offered support to Nepal.

“Nobody’s ever seen anything quite like that, where very powerful, strong, well-built buildings were wiped out like they were toothpicks. It’s a terrible thing. We are sending aid and we’ve spoken to the leadership and we let them know anything they want, they’ll have,” he said.