Glacial Lake Outburst Floods (GLOFs)

The Indian Himalayan Region (IHR), with its fragile ecosystems and vulnerable topography, faces increasing risks from Glacial Lake Outburst Floods (GLOFs). These events, which have already caused severe destruction in neighboring countries like Nepal, are now a growing concern for India as well. The accelerated glacial melt due to climate change and the region’s seismic activity make these events all the more unpredictable and deadly.

What is a Glacial Lake Outburst Flood (GLOF)?

A GLOF occurs when there is a sudden release of water from a glacial lake. This release is often caused by the failure of a moraine or ice dam that holds the water in place. The catastrophic flooding that follows can result in massive downstream damage, including destruction of infrastructure, homes, and ecosystems.

Causes of GLOFs:

1. Glacial Retreat Due to Climate Change: Rising temperatures are causing glaciers in the Himalayas to retreat, forming large glacial lakes. Many of these lakes are dammed by unstable moraines that are susceptible to failure. For instance, the 2013 Uttarakhand floods were triggered by such glacial melt and heavy rainfall.

2. Cloudbursts & Extreme Rainfall: Intense rainfall can raise the water levels of these lakes, putting pressure on weak moraine dams. Kedarnath GLOF (2013) and North Sikkim GLOF (2023) are examples where cloudbursts intensified the situation.

3. Avalanches & Landslides: Ice or rock falling into the lakes can create displacement waves that breach the dams. Chamoli (2021) and South Lhonak Lake (2023) are examples where avalanches and landslides caused sudden breaches.

4. Seismic Activity: The Himalayas lie in Seismic Zones IV and V, which means the region is prone to earthquakes that could alter lake stability. The 2015 Nepal Earthquake raised GLOF threats by altering lake dynamics.

5. Internal Seepage & Weak Moraines: Erosion caused by water seepage weakens moraine dams, causing them to suddenly collapse. The 1985 Dig Tsho GLOF in Nepal is a classic example.

6. Unregulated Infrastructure Development: Construction projects such as hydropower plants and roads in sensitive glacial and river zones can destabilize the region. For example, Teesta-III Dam was destroyed in the 2023 Sikkim GLOF.

Types of Glacial Lakes in the Himalayas

1. Supraglacial Lakes: These lakes form on top of glaciers from the accumulation of meltwater. They are highly vulnerable, especially during the summer melting season.

2. Moraine-dammed Lakes: These are found near the glacier snout and are held by unstable moraine dams. They are structurally weak and are prone to sudden failure under external stressors.

India's Vulnerability to GLOFs

India is highly vulnerable to GLOFs due to the vast number of glacial lakes present in the region and the unique challenges associated with monitoring and mitigating their risks.

Geographic Extent & Vulnerability:

• The Indian Himalayan Region spans 11 major river basins, housing more than 28,000 glacial lakes, with around 7,500 located within India, especially above 4,500 meters in altitude.

• Many of these lakes are remote and difficult to access, making year-round monitoring difficult.

• Satellite data from ISRO (1984–2023) indicates that out of 2,431 glacial lakes (larger than 10 hectares), 676 have expanded, and 601 of these have more than doubled, indicating an increasing vulnerability to GLOFs.

Past GLOF Events:

• 2023 South Lhonak GLOF (Sikkim): This event led to the destruction of the Rs 16,000 crore Chungthang hydropower project and significantly increased sedimentation in the Teesta River, which elevated the risk of downstream flooding.

• 2013 Chorabari GLOF (Uttarakhand): This was part of the Kedarnath tragedy, where a combination of glacial melt, cloudbursts, and landslides resulted in catastrophic damage.

Climatic Triggers:

• Climate change and extreme weather events are increasing the risk of GLOFs. About 66% of these events are caused by ice avalanches or landslides, while the rest occur due to meltwater pressure or seismic activities.

• The record-breaking heat in 2023 and 2024 has intensified glacial melt, further exacerbating GLOF risks.

Measures to Mitigate GLOF Risk in India

India has recognized the growing threat of GLOFs and is taking a multi-faceted approach to mitigate the risks.

1. National GLOF Mitigation Programme:

• The National Disaster Management Authority (NDMA) launched a USD 20 million programme targeting 195 high-risk glacial lakes (initially focusing on 56).

• This program aims to transition from post-disaster relief to pre-disaster risk reduction, coordinating through the Committee on Disaster Risk Reduction (CoDRR).

2. Scientific & Technological Interventions:

• Advanced Tools: Multi-institutional expeditions in 6 Himalayan states are employing technologies like:

  • Bathymetry to measure water volume.

  • Electrical Resistivity Tomography (ERT) to detect ice cores beneath moraine dams.

  • UAVs for terrain mapping.

  • SAR Interferometry to detect micro-slope shifts.

  • Automated Weather and Water Stations (AWWS) in Sikkim, which provide real-time data on lake conditions.

3. Security Forces & Local Participation:

• In regions lacking automated monitoring systems, ITBP personnel are trained for manual early warning systems.

• Local communities are actively involved in monitoring efforts, ensuring cultural sensitivity and building trust.

4. NDMA’s 5-Fold Strategy:

• Hazard Assessment of all vulnerable glacial lakes.

• Automated Weather & Water Stations (AWWS) for real-time monitoring.

• Early Warning Systems (EWS) for downstream areas.

• Risk Mitigation through controlled lake drawdown and structural measures.

• Community Engagement for awareness, preparedness, and trust-building.

Way Forward:

1. Advanced Monitoring & Early Warning:

• Real-time glacial lake surveillance using AWWS, remote sensing, and SAR technology.

• Implement automated alerts and community-based warning systems to proactively manage the risks of GLOFs.

2. Indigenous Solutions & Resilient Infrastructure:

• Encourage startups and academic R&D in cryosphere technologies to enhance monitoring and mitigation capabilities.

• Strengthen moraine dams, enforce construction codes, and ensure flood barriers for hydropower projects to align with GLOF safety standards.

3. Institutional, Transboundary & Community Action:

• Training SDRFs for high-altitude response and fostering data-sharing with neighboring countries like Nepal and China.

• Conduct mock drills and embed resilience into local development planning.

Conclusion:

India faces a high and growing risk from GLOF events due to climatic, geological, and infrastructural vulnerabilities. The inaccessible terrain, lack of early warning systems, and increasing glacial melt call for urgent attention to risk mapping, surveillance, and community-integrated mitigation strategies in the Indian Himalayan Region (IHR).