Increasing exposure to potential flooding in high-mountain catchments

Exposure to flood hazards in high mountain catchments is expected to increase alongside natural hazards, driven by climate change, glacier retreat, and landscape evolution, yet temporally consistent, high-resolution exposure data remain scarce. Here we quantify changes in the exposure of buildings and people to flooding in Nepal and transboundary regions of India and China. Validation against a manually derived reference dataset revealed considerable differences in accuracy and completeness across five building footprint products. Google Open Buildings Temporal 2.5D (OBT) displayed the highest median accuracy (F1 = 0.68), followed by Google Open Buildings V3 (F1 = 0.62). We assessed exposure relative to river channels using the height above nearest drainage (HAND) metric and modelled glacial lake outburst flood (GLOF) inundation extents. Building area within 0–50 m vertical proximity to channels increased by 46% between 2016 and 2023, while those located within modelled GLOF extents increased by 77%. Population projections indicate continued growth in areas of potential flood exposure, with 18% (n = 293,800) of the study-area catchment population estimated to reside within 0–50 m HAND in 2026. Our results demonstrate rapidly increasing exposure in Himalayan catchments and highlight the importance of validated, multi-temporal exposure datasets to inform disaster risk reduction.

Watson, C.S., Rawlins, L.D., Chand, M.B. et al. Increasing exposure to potential flooding in high-mountain catchments. Sci Rep 16, 29730 (2026). https://doi.org/10.1038/s41598-026-70268-0