Underestimated Risk of Glacial Lake Outburst Floods in the Himalayas

Glacial lake outburst floods (GLOFs) in the Himalayas have caused severe consequences for downstream communities, including loss of life and substantial economic damage. The accelerated global atmospheric warming further heightens the GLOF risks. However, a gap in uncertainties underlying hazard and vulnerability constrains the accurate cognition of potential threats. Here we developed a glacial lake inventory and systematically assessed the hazard, exposure, vulnerability and comprehensive risks of all glacial lakes in ten hotspot sub-basins of the Himalayas using a DEM-based stochastic framework, numerical model and social census dataset. From 2015 to 2020, lake areas expanded by 6.52 ± 1.07 km² (0.8% annually). 38% of lakes pose high hazard, impacting 51% of the population and 76% of infrastructure. Northeastern Bhutan exhibits higher vulnerability than India, Nepal and Tibet, yet remains underexplored. The Kuri Chu and Dangme Chu sub-basins are particularly high-risk areas, with 10% of high-risk lakes previously underestimated. This work contributes to developing an effective risk assessment criteria, underscoring the need for systematic study of other glacierized regions.