GS1 🌍 Geography

GLOF (Glacial Lake Outburst Flood)

/dʒiː ɛl oʊ ɛf/

A sudden and catastrophic release of water from a glacial lake when its moraine or ice dam is breached by an earthquake, avalanche, landslide, or excessive meltwater inflow, sending a destructive flood of water, sediment, and debris downstream — a growing hazard in the Himalayas due to climate-change-driven glacier retreat.

Context & Background

India has approximately 7,500 glacial lakes across 11 Himalayan river basins, of which 189–195 have been identified as having high GLOF potential; the South Lhonak Lake GLOF in Sikkim (October 2023) breached a moraine dam, destroyed the Chungthang Dam downstream, and killed 40+ people — highlighting the cascading risk of hydropower infrastructure in GLOF-prone zones.

UPSC Exam Relevance

GS1 (Physical Geography), GS3 (Disaster Management, Climate Change). Prelims: definition; South Lhonak Lake GLOF (2023, Sikkim); ISRO/NRSC monitoring role. Mains: asked to discuss GLOFs as a climate-disaster nexus — the tension between Himalayan hydropower development and GLOF risk; the role of satellite monitoring and early warning systems; and NDMA's mitigation strategies.