How retreating glaciers turn mountain lakes into flood hazards
The disaster began when a glacial collapse released rock, ice and meltwater into valleys, producing a debris surge that destroyed settlements and infrastructure downstream.[7] By September 1, Nepal had counted 1,003 deaths and 3,916 missing people, while China reported 16 deaths and 546 missing.[7] The event renewed scrutiny of glacial lake outburst floods, or GLOFs, although researchers had not yet identified which lake may have burst.[3]
Why it matters
An estimated 15 million people live in areas exposed to glacial lake flooding, with half concentrated in Peru, India, Pakistan and China.[3] The Nepal flood also affected 15 major power stations under construction, showing how the hazard can threaten both communities and critical infrastructure.[2]
Key insights
- The number and surface area of glacial lakes have increased by 50% since the 1990s as retreating glaciers leave more meltwater behind.[3]
- Unlike engineered dams, many glacial lakes are contained by unstable ridges of sediment, ice or rock that can fail suddenly.[3]
- Documented GLOFs rose from an annual average of 7.6 in the first decade of the 20th century to 43.7 during the 2010s, although better satellite coverage and reporting explain part of that increase.[3]
- Satellite analysis indicated that failure of bedrock beneath a glacier helped initiate the August disaster, with the rockfall registering as a magnitude 5.2 seismic event.[7]