Ramesh Kumar, a journalist based in Kathmandu, on Thursday (August 27, 2026) posted a photograph of a clock tower, its hands stopped at 09.29.
“A clock that would never show the time again,” he wrote on X, formerly Twitter. “Betrawati.”
Mr. Kumar had reached Betrawati in Nuwakot district, a town devastated by the previous day’s flood in the Bhotekoshi River in neighbouring Rasuwa district, which borders Tibet. After touring Betrawati, where he was born and raised, he made a grim assessment: “Will Betrawati ever revive as a bazaar again? Almost impossible.”
The extraordinary velocity and scale of the flash flood in the Bhotekoshi River at around 8.40 a.m. on Wednesday (August 26, 2026) have left more than 600 dead and close to 2,500 missing, including foreign nationals, mostly from India.
The Nepal government promptly got into action, mobilising personnel from the Nepal Army, Nepal Police and the Armed Police Force, as it mounted a massive search-and-rescue operation.
Scientists, meanwhile, struggled to piece together the chain of events and determine the origin of the flood, as they wondered about the enormity of the disaster, with some describing it as the worst since the 2015 earthquake.
Regarding the origin, the Nepalese and Chinese sides have concluded that the source was in the Langtang Lirung area. Identifying the exact point where the initial collapse occurred and which side of the border it was on may be difficult.
According to an official at Nepal’s Department of Hydrology and Meteorology, satellite imagery shared by the Chinese side pointed to a combination of an ice avalanche, permafrost movement and a rockslide along the Nepal-China border, with the rockslide occurring on the Chinese side and its impact extending into Nepal.
“The avalanche originated on the Nepalese side of the territory, but very close to the boundary, and induced flooding that crossed the Nepal-China border, causing extensive damage on both sides,” said Binod Parajuli, a senior divisional hydrologist at the department’s flood forecasting division.
The location scientists are pointing to is in the Lhende Khola, a transboundary high-altitude river that originates in Gyirong County in Tibet and flows south into Nepal, where it is a tributary of the Bhotekoshi and Trishuli river systems.
Flooding in the Bhotekoshi River is not uncommon. Last year, in July, a flood — caused without rainfall — in the Bhotekoshi wreaked damage and destruction. Scientists later concluded that the disaster was associated with a glacial lake outburst flood (GLOF).
Different angle
While scientists initially considered whether this year’s flood could also have been linked to a GLOF, its velocity and ferocity, which washed away villages downstream in three districts — Rasuwa, Nuwakot and Dhading — prompted experts to examine it from a different angle.
Dr. Ranjan Kumar Dahal, an associate professor at the Himalayan Geodisaster Research Centre at the Central Department of Geology, Tribhuvan University, described the mass movement that triggered the flood as a sturzstrom.
“A sturzstrom is a massive rock avalanche in which a large volume of rock suddenly collapses and moves at extremely high speed over a long distance,” Mr. Dahal told The Hindu from Trishuli, another area hit hard by Wednesday’s (August 26, 2026) flood. “In high-mountain environments, when rock is mixed with ice, snow, firn and frozen soil, it can be understood as a rock-ice avalanche.”
Rasuwagadhi in Rasuwa is a border checkpoint through which most of Nepal’s trade with China takes place. From May to September, hundreds of pilgrims use this border point to cross into Tibet for the Kailash Mansarovar pilgrimage. Indians make up the largest share of the pilgrims.
It could take weeks, if not months, to assess the full scale of the damage, officials said, adding that the toll could further rise.
The International Federation of Red Cross said the remoteness of the affected areas, combined with damaged infrastructure, was making it harder both to assess the full scale of the disaster and to deliver assistance to people who need it.
“Current estimates suggest around 93,000 people may have been affected,” it said. “Many homes have been severely damaged, cutting off some of the worst-affected communities.”
In the aftermath of the disaster, two more crucial questions have also emerged — whether the early-warning systems were activated and whether climate change had a role in the disaster. Experts say early-warning systems had worked as intended but were rendered ineffective given the staggering speed of the flood.
Kamal Kishore, the head of the UN Office for Disaster Risk Reduction, said the floods had once again highlighted how fragile mountain ecosystems are and how challenging it is to set up early-warning systems in mountain environments.
Scientists have not ruled out the impact of climate change, saying the rising temperatures are causing the Himalayas to warm and glaciers to melt faster, but they stopped short of directly linking the disaster to global warming.
“We had not seen such a disaster in Nepal involving a sturzstrom. However, in 2021, there was a similar event in India,” said Mr. Dahal, referring to the Chamoli disaster in Uttarakhand, where a bedrock failure beneath a glacier triggered a massive rock-ice avalanche that subsequently transformed into a debris flow and flood.
The 2021 Chamoli event has been scientifically described as a rock-and-ice avalanche and, in some literature, explicitly as a sturzstrom. Research found that more than 25 million cubic metres of rock and ice broke loose high in the Uttarakhand Himalaya before moving rapidly downstream.
Catastrophic sturzstrom
“A sturzstrom begins when an unstable rock-ice slope suddenly collapses. The collapsing mass rapidly accelerates, fragments and mixes with ice and snow,” Mr. Dahal explained.
“Pressure and friction can generate meltwater, which may increase lubrication within the moving mass and along its base, reducing resistance and contributing to exceptionally long runout,” he added.
According to him, this process can unfold within just a few minutes.
“As it moves downslope, it may incorporate more ice, snow, rock, soil and water, potentially transforming into a massive debris flow before finally depositing its material,” he said.
Meanwhile, rescue operations have continued on the fourth day, with Prime Minister Balendra Shah saying more than 15,000 personnel have been deployed.
For communities along the Bhotekoshi-Trishuli corridor, the immediate priorities are finding the missing, restoring access and assessing whether some of the places destroyed by the flood can be rebuilt at all.
It’s a race against time.
