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What is Glacial Lake Outburst Flood? How and why a glacier breaks?

What is Glacial Lake Outburst Flood? How and why a glacier breaks?


  • GS 3 || Disaster Management || Major Disasters || Others

Why in the news?

  • Recently a glacier break is said to be the cause of flash floods in Uttarakhand’s Chamoli district which brought severe devastation and loss of lives in the state.
  • Earlier in 2013, Glacial Lake Outburst Flood (GLOF) had caused flash floods in Kedarnath in Uttarakhand.

What is Glacial Lake Outburst Flood (GLOF)?

  • Glacial lake outburst floods (GLOFs) occur from an unstable natural dam formed from a glacial retreat (melting of glaciers).
  • Glaciers are large bodies of ice moving slowly. So, when a glacier retreats, it leaves behind a large impression in the ground, filling it with water and a lake is formed.This is known as a moraine, which can be impounded by precarious pile of debris and buried ice
  • A failure of the Moraine dam has the potential of releasing millions of cubic metres of water in a short period, causing catastrophic flooding downstream.
  • Unlike earthen dams, the weak structure of the Moraine dam leads to the abrupt failure of the dam on top of the glacial lake, which holds a large volume of water.
  • Peak flows as high as 15,000 cubic metre per second have been recorded in such events.
  • India has a remarkable history of successful warnings in relation to Landslide Lake Outburst Floods (LLOFs), dating back to the 19th century.
  • Some of the actively increasing areas of Glacial lakes have been identified in Sikkim.
  • The Chho Lhamo, a glacial lake that has grown in size significantly, is located near the border of Sikkim and Tibet Autonomous Region (TAR) and feeds the River Teesta. In 1989, its area had increased by 1.5 times its size in 1965. The increase in area of the Lhonak and South Lhonak glacial lakes over the last 45 years is significant. Both these lakes have grown in area by 2 times between 1965 and 1989.

Reasons behind Glacial Lake Outburst Flood (GLOF):

  • Increased number of Glacial lakes: According to National Disaster Management Authority (NDMA), 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 GLOFs.
    • As per the record, there are 352, 283 and 1,393 glacial lakes and water bodies in the Indus, Ganga and Brahmaputra basins respectively.
  • Climate change: Due to rapid climate change and global warming, the retreating rate of glaciers are increasing and thus increasing water volume in glacial lakes. The increased water level makes the glacial lakes vulnerable to outbursts.
  • Increased anthropogenic activities at high altitudes: The high altitudes anthropogenic activities have increased considerably in recent times. These activities cause disturbance in the form of various activities.
  • Landslides and other disasters: the land slides at higher altitudes causes glacial retreat. This also increases the Glacial Lake Outburst Flood (GLOF) vulnerability. The outburst of water can also happen due to erosion, an avalanche of snow or rock, an earthquake or volcanic eruptions under the ice.
  • Carrying capacity of high altitude ecosystems: Due to increased construction in ecologically sensitive regions in the Himalayas, the carrying capacity of overall all higher altitude ecosystems is lessening, triggering disasters such as GLOFs, flash floods, landslides, etc.

Prevention and Mitigation:

  • Identification and mapping: The NDMA guidelines say that risk reduction has to begin with identifying and mapping such lakes, taking structural measures to prevent their sudden breach and establishing mechanisms to save lives and property in times of a breach.
  • Constant monitoring and Management of Glacial lakes: As in the backdrop of climate change, the number of glacial lakes is increasing, there is a need for robust monitoring and management of these lakes.
  • Early warning systems: The early warning system specifically designed for Glacial Lake Outburst Flood (GLOF) helps in management of the disaster and mitigate the losses.
  • Sustainable development: In the long run, the development model in the Himalayas has to be sustainable. The principles of SDGs have to be incorporated in the development model being pursued in the Himalayan regions.

NDMA recommendations on Glacial Lake Outburst Flood (GLOF):

  • On identification and monitoring: NDMA has recommended use of Synthetic-Aperture Radar imagery to automatically detect changes in water bodies, including new lake formations, during the monsoon months.
  • On management: 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.
  • On immediate strategy: The NDMA also recommends to constitute an Expert Task Force which, along with the Army, can use explosives to channel water from the river using controlled blasting and manual excavation of debris.
  • On Constructions: The NDMA says that restricting constructions and development in GLOF prone areas is a very efficient means to reduce risks at no cost

India’s preparedness:

  • Identification of potential GLOF : An “Inventory and Monitoring of Glacial Lakes / Water Bodies in the Himalayan Region of Indian River Basins” has been developed by Climate Change Directorate, Central Water Commission, and being implemented by National Remote Sensing Centre.
  • No standard framework in excavation: As of now, unlike other countries, there are no uniform codes for excavation, construction and grading codes in India.
  • No land use planning framework in GLOF prone areas.: There are no widely accepted procedures or regulation in India for land use planning in the GLOF prone areas.
  • Modalities in progress: The Central Water Commission (CWC) is presently working on preparing modalities on a robust early warning system, and a broad framework for infrastructure development, construction and excavation in vulnerable zones.

Wy forward:

India needs to strengthen its mitigation framework and include more specific provisions related to GLOF. The early warning system needs to be placed in highly prone areas. Along with these measures, India is also required to implement its National Mission on National Mission for Sustaining the Himalayan Ecosystem (NMSHE) sincerely in ecologically sensitive areas.

Model Mains Question:

  1. Discuss the factors that led to Glacial Lake Outburst Floods (GLOF) in the Himalyan region. What are the NDMA recommendations for prevention and mitigation of  Glacial Lake Outburst Flood (GLOF)?