Glacial Lake Outburst Flood (GLOF): A UPSC Overview

Posted by on

 


Definition & Mechanism

  • GLOF occurs when a glacial lake, often dammed by moraine (ice/rock debris) or ice itself, suddenly bursts, releasing massive volumes of water downstream.

  • Features:

    • Sudden, rapid release (minutes to days)

    • Discharge often one order of magnitude above normal flow

Types of Glacial Lakes

  • Supraglacial lakes: On glacier surface

  • Moraine-dammed lakes: At glacier terminus, behind unstable debris

  • Also: Subglacial, ice-blocked, erosional lakes

Causes & Triggers

  • Climate change: Accelerated glacier melt leading to lake formation/expansion

  • Triggers include:

    • Landslides, ice avalanches into lakes

    • Earthquakes

    • Heavy rainfall and moraine destabilisation

    • Glacier surges or overtopping of dams

Notable Incidents

Chorabari Lake, Uttarakhand (2013)

  • Flood triggered the devastating Kedarnath tragedy, killing hundreds during heavy monsoon floods. 

South Lhonak Lake, Sikkim (2023)

  • A GLOF damaged the 1,250 MW Teesta III dam, destroyed infrastructure, raised riverbeds up to 20 ft downstream. Over 90 fatalities, 88,000 affected across Sikkim and North Bengal. 

Nepal (Thame, 2024; Tilgau, Humla, 2025)

  • Multiple GLOFs in Nepal inundated villages, destroyed bridges, displaced communities—highlighting regional risks.

Global Perspective

  • Globally over 1,348 recorded GLOFs, causing 12,000+ deaths; frequency rising due to warming climate.

  • Major hotspots: High Mountain Asia (India, Nepal, Bhutan, Pakistan), Andes (Peru). Example: Lake Palcacocha flood in Peru (1941) killed up to 5,000.

Impact & Challenges

  • Death and displacement, massive infrastructure loss (dams, roads, bridges).

  • Sediment deposition raises riverbeds, increasing flood risk (e.g. Teesta riverbed rose 2 m requiring urgent dredging in West Bengal).

  • Challenges:

    • Difficult terrain, remote lakes, sparse data
    • Insufficient early-warning infrastructure
    • Underfunded mitigation programs and weak public awareness

India’s Institutional Response

National GLOF Risk Mitigation Programme

  • Launched by NDMA (National Disaster Management Authority) prioritising 195 high-risk lakes; includes hazard assessments, early warning systems, community training. Investment ~USD 20 million.

Core strategies:

  • Installation of Automated Weather & Water Stations (AWWS) and Early-Warning Systems (EWS)

  • Controlled siphoning/draining or managed breaching

  • Use of advanced remote sensing (SAR interferometry, UAV mapping, bathymetry, Electrical Resistivity Tomography) for hazard monitoring. 

Central Water Commission & Dam Protection

  • Identified over 100 dams in six Himalayan states at risk. CWC seeks Defense assistance for real-time lake monitoring. 

  • Released ₹220 Cr to Himachal Pradesh for reconstruction and GLOF mitigation projects covering HP and neighboring states.

Way Forward

  • Enhanced monitoring: Expand AWWS/EWS networks to all vulnerable lakes; ensure maintenance and data reliability.

  • Structural mitigation: More managed draining of lakes; guided breaching and controlled overflow structures.

  • Community preparedness: Training, mock drills, and hazard education in vulnerable Himalayan communities.

  • Scientific mapping & zoning: Detailed risk zoning, vulnerability mapping, and inclusion in disaster plans.

  • Policy integration: Incorporate GLOF risk in regional climate action plans (SAPCC), hydropower planning, and infrastructure siting.

  • International collaboration: Engage through ICIMOD, UNEP, and transboundary risk sharing; learn from Nepal’s Tsho Rolpa early-warning projects.

Conclusion

Glacial Lake Outburst Floods (GLOFs) are emerging as a serious climate-induced hazard, particularly in the Himalayan region. Their increasing frequency highlights the urgent need for scientific monitoring, infrastructure safeguards, community-based early warning systems, and regional cooperation. India’s initiatives like National Mission on Sustaining Himalayan Ecosystem (NMSHE) and State Action Plans on Climate Change (SAPCC) must be integrated with proactive disaster preparedness and sustainable development planning in ecologically fragile zones.

Comments

Post a Comment