Nearly 294,000 people could live in housing located in flood-prone areas in the Himalayas, in parts of India, Nepal, and China. At the same time, the area occupied by buildings in these zones increased by about 46% between 2016 and 2023, according to a study published in the scientific journal Scientific Reports.
The investigation analyzed the evolution of construction in areas located up to 50 kilometres downstream of 1,361 Himalayan lakes. The researchers used five datasets to estimate the area occupied by buildings and to assess the populations’ potential exposure to floods.
Between 2016 and 2023, the area occupied by buildings located within 50 metres vertically above a river channel — used as an indicator of exposure to potential floods — increased from 12.38 to 18.04 square kilometres.
In zones classified as high risk of floods caused by the bursting of glacier lakes, the growth was even more pronounced: almost 78% in the same period, with the built area rising from 0.72 to 1.28 square kilometres.
Climate change aggravates the risks
Floods in the Himalayas can result from seasonal monsoons, episodes of extreme rainfall, or less frequent, yet potentially devastating phenomena, such as debris flows and floods caused by glacier lake outbursts.
Climate change could intensify the magnitude of these phenomena. Moreover, the narrow valleys and steep slopes characteristic of mountainous regions can amplify water levels and flood damages.
Based on the estimated built-up area, the researchers calculated that about 293,800 people, equivalent to 18% of the study area’s population, could live in buildings exposed to potential floods in 2026.
Nepal accounts for a significant portion of this at-risk population, with an estimate of 108,500 people in exposed housing. Of these, about 22,800 will be located within ten metres vertically of a river channel.
Projections also point to an increase of 17,900 people — about 6% — living in flood-risk zones between 2015 and 2030.
Data gaps limit risk assessment
The authors warn, however, that the results should be interpreted with caution. Both the estimates of the built-up area and the population growth projections carry a high degree of uncertainty due to the difficulty in obtaining reliable data.
Therefore, they advocate creating more rigorous building databases to enable a more precise identification of exposed dwellings and to improve risk assessment.
Thus, the study highlights two factors that can intensify exposure to floods in the Himalayas: the expansion of construction in potentially dangerous zones and the possibility of more severe extreme events in a context of climate change.
