States Asked to Prepare for Glacial Lake Outburst Floods

Context

The Union Home Ministry has directed States and Union Territories to strengthen monitoring of glacial lakes and enhance preparedness for Glacial Lake Outburst Floods (GLOFs).

The rapid retreat of glaciers, expansion of high altitude glacial lakes and instability of natural moraine dams are increasing the vulnerability of the Himalayan region to GLOFs. Given the fragile terrain and the concentration of settlements and infrastructure in downstream valleys, such events can have severe consequences.

Key Highlights

• Authorities have been advised to strengthen glacial lake monitoring, early warning mechanisms and emergency response systems.
• GLOFs can suddenly release enormous volumes of water, ice and debris, often leaving very limited time for downstream communities to respond.
• Hydropower projects, bridges, roads, electricity infrastructure and downstream settlements are particularly vulnerable.
• The probability and intensity of a GLOF depend on several interacting factors, including rapid lake expansion, slope instability, avalanches, heavy rainfall and seismic activity.
• Climate induced glacier retreat can increase the formation and expansion of glacial lakes, thereby adding to the long-term hazard in the Himalayan region.

Understanding the GLOF Hazard Chain

A GLOF may begin when an external trigger such as an ice or rock avalanche, landslide, extreme snowfall, heavy rainfall or earthquake destabilises a glacier fed lake or its natural dam.

The resulting breach can produce a powerful flood carrying water, sediment, ice and debris downstream. As the flood travels through narrow Himalayan valleys, it can cause erosion and damage infrastructure, settlements, livelihoods and other assets.

Key Concepts

• Glacial Lake Outburst Flood (GLOF): A sudden release of a large volume of water from a glacier fed lake due to the failure, overtopping or breaching of its natural dam.
• Moraine Dam: An unconsolidated accumulation of rocks, soil and sediments deposited by a glacier that can act as a natural barrier for a glacial lake. Its unstable nature can make it vulnerable to failure.
• Remote Sensing: The use of satellite or aircraft based observations to monitor changes in glacial lakes, glaciers and surrounding slopes.
• Early Warning System: An integrated mechanism that combines hazard detection, risk communication and pre-planned community response to reduce loss of life and property.

Way Forward

• Develop and regularly update a dynamic inventory of high risk glacial lakes across the Himalayan region.
• Integrate satellite based monitoring with ground-l based sensors and community-level observation systems.
• Undertake detailed dam break and flood flow modelling to identify vulnerable downstream areas.
• Conduct regular evacuation drills and community awareness programmes in high risk valleys.
• Make GLOF risk assessment and disaster resilience measures mandatory for major infrastructure projects in vulnerable Himalayan areas.
• Strengthen coordination among central agencies, States, local authorities and communities for real time information sharing and rapid emergency response.