Nepal study finds 108,500 people live in flood paths

At least 108,500 people in Nepal live on ground that floods from the mountains above could reach, according to a study published in a Nature Portfolio journal. More than 23,000 of them live less than 10 metres above a riverbed, the height at which the authors say exposure is highest.

The number of buildings standing inside the path of a potential glacial lake outburst flood in Nepal rose 78 percent between 2016 and 2023. Across the high mountain regions of Nepal, China and India, about 300,000 people are exposed to such flooding, the study estimates, and more than 80 percent of the structures at risk are in Nepal.

The researchers mapped buildings and populations within 50 metres of existing river levels using census and publicly available building data, then simulated how far water released by a glacier lake outburst could travel. The total area occupied by buildings within 50 metres of riverbeds grew 46 percent over the same seven years.

Mohan Bahadur Chand, an assistant professor in Kathmandu University's department of environmental science and one of the authors, told the Kathmandu Post the aim was to establish how many buildings and people sit in the path of floods coming from higher up. The paper identifies hydropower development, border and trade roads built along river channels, tourism infrastructure such as lodges and hotels, and unplanned urbanisation on floodplains as drivers of the construction.

Basanta Raj Adhikari, director of the Centre for Disaster Studies at Tribhuvan University, told the Post that road expansion, changing livelihoods and internal migration have reshaped mountain settlement in recent decades. "Most roads are built along river corridors where construction materials are readily available," he said. "But we did not adequately assess flood risks." Adhikari said local governments lack the skilled staff to apply risk-sensitive land-use rules and the federal government neither enforces them strictly nor holds anyone accountable.

The Post reported that the study cites the Rasuwa-Bhotekoshi flood, which reached settlements as high as 82 metres above river level, and gives its toll as 1,455 dead and 5,285 unaccounted for. The paper notes that Himalayan temperatures have risen by 3 degrees Celsius in individual winter months against a global average of about 1.4 degrees since preindustrial times, and that glaciers in the Hindu Kush are melting at twice the rate. Nepal identified 21 potentially dangerous glacial lakes in the Gandaki, Koshi and Karnali basins six years ago.

Shankar Limbu, an advocate, said the study and the government have both failed to prioritise indigenous people. He pointed to hydropower construction in Rasuwa that he said displaced Tamang communities from safer settlement sites, and to the Bhotkhola project, where 192,000 tonnes of explosives and 188,000 detonators are planned for tunnel work, with 26 glacial lakes upstream. "If explosions trigger an outburst in those lakes, it can destroy entire settlements downstream," he told the Post.

Chand acknowledged that the building data came from public sources and said he hoped the government would use the findings to run its own field assessments.