A rough draft of where the risk sits
About 294,000 people in Nepal live in areas exposed to extreme flood risk from rivers that drain the country's high mountain basins, according to a study published on Thursday in the journal Scientific Reports. Roughly 108,000 of them live downstream of glacial lakes, which can release a sudden pulse of water if the ice or rock holding them back fails.
The analysis began in autumn 2025 and spent months in peer review. Researchers mapped rivers that originate in the transboundary areas along Nepal's borders with Tibet and India, isolated zones within 50 kilometres downstream of glacial lakes or river basin headwaters, and mapped what a flood raising water levels by 50 metres would reach.
After a disaster that set a new benchmark
The study follows the August disaster on the Bhote Koshi river, when a rock and ice avalanche fell from the roughly 24,000-foot Langtang Lirung peak and sent a debris flow about 120 miles downstream. Nepali authorities say at least 1,455 people died, at least 5,285 are still missing and nearly 14,000 were rescued.
"This event set a new level, a new threshold," said Dipesh Chapagain, a senior scientist at the United Nations University Institute for Environment and Human Security. He said the real risk could be higher than the paper estimates, because the August flood travelled further and rose higher in some communities than the study's scenario.
Building ever closer to the water
Scott Watson, a senior research fellow at the University of Leeds, said development in Nepal is crowding the river channels, driven by tourism and trade routes. The study found that the built-up area within 50 vertical metres of riverbanks grew by about 46 per cent between 2016 and 2023.
Researchers say flood early warning systems and land use zoning should be priorities in the areas the study identifies as high risk. Thousands of new glacial lakes are forming as glaciers shrink and permafrost thaws, and many could send floodwater downstream with little notice.