Glacial Lake Outburst Floods

About Glacial Lake Outburst Floods:

• These are disaster events caused by the abrupt discharge of water from glacial lakes.

What are glacial lakes?

• Glacial lakes are large bodies of water that sit in front of, on top of, or beneath a melting glacier.
• As a glacier withdraws, it leaves behind a depression that gets filled with meltwater, thereby forming a lake.
• The more the glacier recedes, the bigger and more dangerous the lake becomes. Such lakes are mostly dammed by unstable ice or sediment composed of loose rock and debris.
• In case the boundary around them breaks, huge amounts of water rush down the side of the mountains, which could cause flooding in the downstream areas. This is called as Glacial Lake Outburst Flood.
• Reasons for GLOFs
  • It can be triggered by various reasons, including glacial calving, where sizable ice chunks detach from the glacier into the lake, inducing sudden water displacement.
  • Incidents such as avalanches or landslides can also impact the stability of the boundary around a glacial lake, leading to its failure, and the rapid discharge of water.

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Situation in Uttarakhand

• It has 13 glacial lakes which are prone to GLOF. Based on the analysis of available data and research from various technical institutions, these lakes have been categorised into three risk levels: ‘A’, ‘B’, and ‘C’.
• Five highly sensitive glacial lakes fall into the ‘A’ category. These include Vasudhara Tal in the Dhauliganga basin and four lakes in Pithoragarh district — Maban Lake in Lassar Yangti Valley,Pyungru Lake in the Darma basin, an unclassified lake in the Darma basin, and another unclassified lake in Kuthi Yangti Valley.

Q1: What is an avalanche?

It is a mass of material moving rapidly down a slope. An avalanche is typically triggered when material on a slope breaks loose from its surroundings; this material then quickly collects and carries additional material down the slope. There are various kinds of avalanches, including rock avalanches, ice avalanches , and debris avalanches

Source: Why Uttarakhand govt wants to evaluate the risk of Glacial Lake Outburst Floods