By Abdullahi Lukman
Nearly 294,000 people across the Himalayan regions of Nepal, India and China may be living in areas exposed to potential flooding, with the footprint of buildings in vulnerable locations increasing significantly in recent years, according to a study published in Scientific Reports.
The study found that the area occupied by buildings within 50 vertical metres of river channels increased by 45.75 per cent between 2016 and 2023, rising from 12.38 square kilometres to 18.04 square kilometres.
In areas considered highly vulnerable to glacial lake outburst floods (GLOFs), the building footprint grew by 77.78 per cent, from 0.72 to 1.28 square kilometres over the same period.
Researchers led by C. Scott Watson assessed potential flood exposure in areas extending up to 50 kilometres downstream of 1,361 Himalayan lakes across Nepal and neighbouring parts of India and China.
Using five datasets validated against manually recorded information, the team estimated the extent of buildings in potentially vulnerable areas and used the results to assess the number of people who could be exposed to flooding.
The findings suggest that approximately 293,800 people, representing 18 per cent of the population in the study area, may have been living in buildings exposed to potential flooding in 2026.
Nepal accounts for an estimated 108,500 of those potentially affected, including about 22,800 people living within 10 vertical metres of a river channel.
The study also projects that the population living within identified flood-risk zones could increase by approximately 17,900 people, or six per cent, between 2015 and 2030.
Flooding in the Himalayas is commonly triggered by seasonal monsoons, intense rainfall and, in some cases, glacial lake outburst floods or destructive flows of water and debris. Researchers warn that climate change could intensify these hazards, while steep and narrow mountain valleys can amplify flood impacts.
Glacial lake outburst floods occur when water held in glacial lakes is suddenly released, potentially sending destructive surges downstream and threatening settlements, infrastructure and livelihoods.
Despite the concerning findings, the researchers cautioned that estimates of building coverage and population exposure carry substantial uncertainty.
They stressed the need for more accurate and comprehensive building databases to improve assessments of flood exposure and help authorities plan effective disaster preparedness and risk-reduction measures in the Himalayan region.
