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Glacial Lake Outburst Floods (GLOF)

2024 APR 9

Mains   > Disaster Management   >   Disaster mitigation   >   Floods


GS 3 > Disaster Management   >  Disaster mitigation   >   Floods


  • Recently, the Uttarakhand government has constituted two teams of experts to evaluate the risk posed by five potentially hazardous glacial lakes in the region, which are at risk of Glacial Lake Outburst Floods (GLOFs). 
  • Such floods have led to numerous catastrophic events in the Himalayas over the past few years. The goal of the risk assessment exercise is to minimise the possibility of a GLOF incident and provide more time for relief and evacuation in case of a breach.


  • The National Disaster Management Authority (NDMA) has identified 188 glacial lakes in the Himalayan regions as potential threats for breach due to heavy rainfall, with 13 of these located in Uttarakhand.
  • Rising surface temperatures across the globe, including India, have increased the risk of GLOFs.
  • The study published in Nature Communications reveals that approximately 15 million people worldwide are at risk from Glacial Lake Outburst Floods (GLOFs), a threat that spans globally and not confined to India alone. Crucially, the research points out that over half of this at-risk population is concentrated in just four nations: India, Pakistan, Peru, and China.
Uttarakhand has witnessed two major GLOF events in the past few years. The first took place in June 2013, which affected large parts of the state, and Kedarnath Valley was the worst hit, where thousands of people died. The second occurred in February 2021, when Chamoli district was hit by flash floods due to the bursting of a glacier lake.



  • A Glacial Lake Outburst Floods (GLOF) is a type of flood occurring when water dammed by a glacier or a moraine is released suddenly.
  • When glaciers melt, the water in these glacial lakes accumulates behind loose naturally formed 'glacial/moraine dams' made of ice, sand, pebbles and ice residue.
  • Unlike earthen dams, the weak structure of the moraine dam leads to the abrupt failure of moraine dam on top of the glacial lake, which holds large volume of water.
  • A catastrophic failure of the moraine dam can release the water over periods of minutes to days causing extreme downstream flooding.
  • Glacial retreat due to climate change occurring in most parts of the Hindu Kush Himalaya has given rise to the formation of numerous new glacial lakes, which are the major cause of Glacial Lake Outburst Floods (GLOFs).


  • Earthquake:
    • An earthquake (Tectonic) or cryoseism (non-tectonic seismic event of the glacial cryosphere) can also cause GLOF.
    • During this, the boundary of the glacial lake will collapse suddenly and release the water in the glacial lake.
  • An avalanche of rock or heavy snow:
    • During this, the water in the glacial lake might be displaced by the avalanche.
  • Volcanic eruptions
    • Volcanic eruptions under the ice can also cause GLOF.
    • These volcanic eruptions might displace the boundary or increase the pressure on glacial lake or both.
  • Increase in flow of water:
    • A buildup of water pressure or structural weakness of boundary due to an increase in the flow of water.
  • Heavy rainfall/melting of snow:
    • This can lead to massive displacement of water in a glacial lake.
  • Long-term dam degradation can also induce GLOF.


  • Loss of Life and Property: The Kedarnath disaster in 2013, triggered by heavy rainfall leading to glacial melts, resulted in over 5,000 deaths. This event underscores the devastating potential of GLOFs on human life and property. The sudden and overwhelming flow of water can wipe out entire communities, as seen in Uttarakhand?.
  • Infrastructure Damage: The 2021 GLOF event in Rumbak, Ladakh, caused extensive damage to infrastructure, including roads and bridges. Such damage not only has immediate consequences but also long-term impacts on connectivity and economic activities in the region?.
  • Agricultural Devastation: In 2014, the Gya village in Ladakh experienced a GLOF that destroyed farmlands and crops, illustrating how these events can also devastate agriculture, a critical source of livelihood for many. The loss of agricultural land and productivity affects food security and economic stability in the region?.
  • Environmental and Ecological Damage: GLOFs cause habitat destruction and fragmentation, affecting flora and fauna. The high-velocity flow of water and sediment can significantly alter landscapes, leading to long-term environmental degradation? ?.
  • Infrastructure Resilience: The damage to the Teesta III dam during a GLOF event in 2023 reveals vulnerabilities in critical infrastructure. Dams and other structures in high-risk areas must be designed to withstand such events, incorporating considerations for spillway capacity and structural integrity to ensure safety?.
  • Socio-economic Disruptions: Beyond the immediate impact, GLOFs can have lasting socio-economic consequences. For instance, the destruction of infrastructure such as hydroelectric power plants not only causes economic losses but also disrupts power supply, affecting industries and livelihoods far beyond the immediate area of the flood?.
  • Exposure and Vulnerability: Globally, approximately 15 million people worldwide are potentially exposed to GLOF impacts, with significant numbers in India. The exposure and vulnerability to GLOFs highlight the importance of considering these factors in disaster risk management. 


  • Identifying potentially dangerous lakes:
    • Potentially dangerous lakes can be identified based on field observations, records of past events, geomorphologic and geotechnical characteristics of the lake/dam and surroundings, and other physical conditions.
  • Use of technology:
    • Promoting use of Synthetic-Aperture Radar imagery (a form of radar that is used to create two-dimensional images) to automatically detect changes in water bodies, including new lake formations, during the monsoon months.
    • Methods and protocols could also be developed to allow remote monitoring of lake bodies from space.
  • Channeling potential floods:
    • To manage lakes structurally, the NDMA recommends reducing the volume of water with methods such as controlled breaching, pumping or siphoning out water, and making a tunnel through the moraine barrier or under an ice dam.
  • Uniform codes for construction activity:
    • Developing a broad framework for infrastructure development, construction and excavation in vulnerable zones.
    • There is a need to accept procedures for land use planning in the GLOF prone areas.
  • Enhancing early warning systems (EWS):
    • The number of implemented and operational GLOF EWS is very small, even at the global scale.
    • In the Himalayan region, there are at three reported instances (two in Nepal and one in China) of implementation of sensor- and monitoring-based technical systems for GLOF early warning.
  • Training local manpower:
    • Apart from pressing specialised forces such as National Disaster Response Force (NDRF), ITBP and the Army, NDMA has emphasised the need for trained local manpower.
    • It has been observed that over 80% of search and rescue is carried out by the local community before the intervention of the state machinery and specialised search and rescue teams.
    • The local teams could also assist in planning and setting up emergency shelters, distributing relief packages, identifying missing people, and addressing the needs for food, healthcare, water supply etc.
  • Comprehensive alarm systems:
    • Besides classical alarming infrastructure consisting of acoustic alarms by sirens, modern communication technology using cell and smartphones can complement or even replace traditional alarming infrastructure.
  • Awareness generation:
    • NDMA emphasized the need for psychological counselling of victimsDissemination of accurate information through press conferences and mass media.


  • Short Term:
    • Formation of Specialized Committee under Ministry of Jal Shakti:
  • The committee should involving expert agencies dealing with research and development on Glacial, Landslide and Flood Hazards
  • It aims to formulate specific land use zoning, development control, building construction regulations etc.
  • Hiring group of expert agencies to identify susceptible sites through Remote Sensing and GIS
  • Development of Early Warning System (EWS) based on Ground Instrument, Water level sensors
  • Set up a regular monitoring system using remote sensing satellites and GIS.
  • Long Term:
    • Use of technology:
  • Use of web-based and app-based dissemination tools for the preparation of maps for common use not only by the administrators but also by the community, tourists etc.
  • Awareness programme on GLOF hazard
  • NDMA should identify not-for-profit organisations to undertake the awareness building activities
  • Use of traditional art forms/ traditional knowledge is necessary to document and disseminate old traditional best practices available in mountain regions of India through community participation in trainings
  • National Data Centre on GLOF:
  • It would integrate various data sources, a geo-portal to address the data needs and thus, enable an effective response


  • Institutional Mechanisms
    • The National Disaster Response Force (NDRF)/SDRF mandated by the DM Act, 2005, will address, in close collaboration with all other field level agencies, all concerns regarding the response to the threat of GLOF disaster
  • Centre for Glacial Research, Studies & Management (CGRSM)
    • This initiative will help in ensuring a wider view of glacial studies as a component of the environment/climate change
  • Comprehensive and Pilot National GLOF Mitigation Projects
    • It aims for assessing risk of GLOFs, enhancing the promptness and efficacy of response to impeding threats of GLOF, geological and geotechnical investigations of GLOF etc.


  • Assessment and reduction of risk:
    • Assessment of the risk and vulnerabilities associated with GLOF disasters and reduction in the degree of the risk, severity or consequences of GLOF
  • Greater coordination:
    • Unlike an earthquake, which is relatively sudden, GLOF events can be anticipated, as we could monitor changes in the size of lakes. But this requires greater coordination.
    • So early warning systems require a coordinated approach, such as multiple agencies promptly sharing satellite images (that are trained towards the Himalayas) and a network of sensors to provide adequate warning.
  • Greater care while planning infrastructure projects:
    • For instance, while the Teesta River is a source of hydropower generation for several power projects, the risk of GLOF-like events requires greater care in planning and executing dams and other infrastructure projects, which account for the huge amount of water that can potentially gush through the mountains.
  • Capacity building:
    • Establishment of monitoring and early warning systems for susceptible glacial lakes.
    • Spreading awareness with a stress on preparedness and providing advice and training to the agencies involved in the management of GLOF.
  • Efforts required post-disaster:
    • Ensuring that proper arrangements are made for organizing rescue, relief and rehabilitation works.
    • Improving the quality and increasing the speed of rehabilitation and reconstruction process.


Q. What are Glacial Lake Outburst Floods (GLOFs), and what threats do they pose? Discuss strategies to mitigate their impact and enhance resilience against these extreme weather phenomena. (15 marks, 250 words)