Glacial Lake Outburst Floods (GLOF)

Source Glacial Lake Outburst Floods (GLOF): PIB
GS III: Environment

Overview

1. News in Brief
2. Glacial Lake Outburst Floods (GLOF)
3. Prevention and Mitigation Strategies by NDMA

Why in the News?

A disastrous flood caused by a glacial lake outburst that occurred in Sikkim in the early hours of October 4 has resulted in more than 25 verified deaths, and many more are still unaccounted for. 

News in Brief

• The Teesta 3 hydroelectric project’s crucial Chungthang dam was demolished by the massive discharge.
• Also left many other hydropower plants along the river inoperable.
• In the four most affected districts of Mangan, Gangtok, Pakyong, and Namchi, water pipes, sewage lines, and 277 homes have been damaged.
• The flood formed as a result of Glacier Lake Outburst Floods (GLOF)

Glacial Lake Outburst Floods (GLOF)

• Events, which are formally known as Glacier Lake Outburst Floods (GLOF), occur when sizable lakes created by glacier melting abruptly burst through the natural moraine barriers made of rock, silt, and other debris.
• These floods can cause significant damage to infrastructure, property, and human life.
• GLOFs are becoming more frequent due to climate change, which is causing glaciers to melt at an accelerated rate.
• The resulting increase in water volume in glacial lakes is putting pressure on natural dams, making them more susceptible to failure.
• GLOFs are a serious threat to communities living downstream from glacial lakes.
• Early warning systems and disaster preparedness plans can help mitigate the impact of these floods.
• There are currently more than 300 glacial lakes in Sikkim Himalayan, according to the Sikkim State Disaster Management Authority.

Glacier Lake Outburst Floods (GLOF) Phenomenon in Himalaya

• One of the glaciers that is apparently disappearing the quickest is the South Lhonak glacier in north Sikkim.
• Between 1962 and 2008, the glacier shrank by over two kilometres.
• From 2008 to 2019, it further receded by around 400 m.
• The Himalayas are thought to have 7,500 glaciers, and GLOFs have historically been linked to significant catastrophes.
• The 1926 Jammu and Kashmir flood, the 1981 Kinnaur valley floods in Himachal Pradesh, and the 2013 Kedarnath eruption are among the disasters included in a study in the magazine Nature.

Prevention and Mitigation Strategies by NDMA

Factors Contributing

• Large lake volume
• Narrow and high moraine dam
• Stagnant glacier ice within the dam
• Limited freeboard between the lake level and the crest of the moraine ridge.
• hanging glaciers, Rock falls and Melting ice-core
• Settlement and/or piping within the dam
• Catastrophic glacial drainage into the lake from sub-glacial or englacial channels or supraglacial lakes

Prevention and Response plan

• Reduce the volume of water in the lake
  • The most important structural mitigation measure for reducing GLOF risk is to reduce the volume of water in the lake in order to reduce the peak surge discharge.
  • Any one or combination of the following methods may be applied to reduce the volume of water in the lake
    • Controlled breaching
    • Construction of an outlet control structure, pumping or siphoning out the water from the lake
• Identification of Potentially Dangerous Lakes
  • The hazard and risk assessment provide the basis for prioritising, designing, and implementing risk management strategies, and is therefore considered as a cornerstone of Disaster Risk Management (DRM).
  • Identifying where from and how likely hazard processes are to initiate, is based on an assessment of wide-ranging triggering and conditioning factors.
  • Hazard mapping: Identifying the potential threat from the hazard for downslope and downstream areas, and providing the scientific basis for decision-making and planning.
• Channeling Potential Floods
  • Methods such as controlled breaching, pumping or siphoning out water.
  • Creating a tunnel through the moraine barrier or under an ice dam can decrease water volume.
• Awareness & Peparedness
  • Automated Alert Services: In collaboration with the various government and private travel agencies including Indian Airlines, Indian Railways and mobile network operators, NDMA can send automated SMS and email messages on precautions to be taken while travelling in the GLOF/LLOF vulnerable areas at the time of booking of travel tickets to these areas.
  • Use of local mass media: A well-designed mass media campaign (both print & electronic) can be undertaken in the vulnerable and affected states.
  • Medical DisasterManagement Plans: 
  • Patient Evacuation Plan: Heli-ambulances need to be deployed to aid in the evacuation of casualties

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