Glacial Lake outburst – UPSC GS1

Parts of Uttarakhand witnessed massive flooding due to Glacial Lake outburst.
What are Glaciers?
Glaciers are made up of fallen snow. It compresses into large, thickened ice masses over a period of time. They are formed when snow remains in one location long enough to transform into ice.
Where are Glaciers found? Glaciers are found on every continent except Australia. Some are hundreds of thousands of years old. A large cluster of glaciers are in the Himalayas, which are part of India’s long northern border.
What is Glacial Lake Outburst Floods(GLOF)?
It is a type of outburst flood. It occurs when water dammed by a glacier is released. In other words, it’s an outburst that happens when a dam containing a glacial lake fails.
How does GLOF happen?
  • Retreating glaciers, like several in the Himalayas, usually result in the formation of lakes at their tips, called proglacial lakes. It is often bound only by sediments and boulders.
  • If the boundaries of these lakes are breached, it can lead to large amounts of water rushing down to nearby streams and rivers. It gathers momentum on the way by picking up sediments, rocks, and other material, and resulting in flooding downstream.
Features of GLOF: The three main features are:
  • They involve sudden (and sometimes cyclic) releases of water.
  • They tend to be rapid events, lasting hours to days.
  • Furthermore, they result in large downstream river discharges (which often increase by an order of magnitude).
Causes behind GLOFs
The boundaries of glacial lakes breach due to multiple reasons. Like,
  • buildup of water pressure or structural weakness of boundary due to an increase in the flow of water.
  • 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 under the ice can also cause GLOF. These volcanic eruptions might displace the boundary or increase the pressure on glacial lake or both.
  • 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.
  • Other reasons such as the collapse of an adjacent glacial lake, etc.
NDMA Guidelines for Reducing GLOFs:
The NDMA, headed by PM, had issued detailed guidelines on how to reduce and deal with disasters caused by GLOFs:
  • Identify and Mapping Dangerous Lakes: Potentially dangerous lakes can be identified. This identification will be based on field observations, past events, geomorphologic and geotechnical characteristics, etc.
  • Use of Technology: It has recommended the use of Synthetic-Aperture Radar imagery. It will automatically detect changes in water bodies, including new lake formations, during the monsoon months.
  • Structural Measures: It recommends reducing the volume of water with various methods to manage lakes structurally. Methods are pumping or siphoning out water and making a tunnel through the moraine barrier or under an ice dam.
    • Example: In 2014, a landslide occurred along Phuktal (tributary to Zanskar river) in Kargil district of Ladakh. It led to a potential flood situation. The NDMA created an Expert Task Force which along with the Army used explosives to channel water from the river. It used controlled blasting and manual excavation of debris for this purpose.
  • Constructions and development in High prone areas should be prohibited. It is a very efficient means to reduce risks at no cost.
  • Land Use Planning: Land use planning regulations need to be developed. In downstream areas, Infra. development should be monitored prior to, during, and after the construction.
  • Trained Local Manpower: Apart from specialized forces such as NDRF, ITBP, and the Army, there is a need for trained local manpower. These teams will assist in planning and setting up emergency shelters, distributing relief packages, identifying missing people, and addressing the needs for food, healthcare, water supply, etc.
  • Early Warning System: A robust early warning system in vulnerable zones should be put in place.
  • Emergency medical response team: Quick Reaction Medical Teams, mobile field hospitals, Accident Relief Medical Vans, and heli-ambulances should be set up in areas inaccessible by roads.
  • Psychological Counselling: The guidelines also call for psychological counselling of victims.
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