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Glacial Lake Outburst Floods (GLOFs)
Why is it in News?
- Glacial burst on Nandadevi caused avalanche and resulted into flash floods in Rishiganga and Dhauliganaga in Uttrakhand.
Details:
- In Oct 2020, the National Disaster Management Authority (NDMA) had issued detailed guidelines on how to reduce and deal with disasters caused by Glacial Lake Outburst Floods (GLOFs).
- GLOFs:
(1) It is a type of outburst flood that occurs when the dam containing a glacial lake fails.
(2) When glaciers melt, the water in glacial lakes creates loose, natural “glacial/moraine dams” made of ice, sand, pebbles and ice residue.
(3) The weak structure of the moraine dam leads to the abrupt failure of the dam on top of the glacial lake, which holds large volume of water.
(4) It can release millions of cubic metres of water in a short period, causing catastrophic flooding downstream.
(5) Peak flows as high as 15,000 cubic metre per second have been recorded in such events.
(6) Glacial retreat due to climate change is happening in most parts of the Hindu Kush Himalaya.
(7) It has given rise to the formation of numerous new glacial lakes, which are the major cause of GLOFs.
- NDMA guidelines for Risk Reduction:
(1) Identifying and mapping of such glacial lakes based on field observations, records of past events, geomorphologic and geotechnical characteristics.
(2) Taking structural measures to prevent their sudden breach
(3) Establishing mechanism to save lives and property in times of a breach.
Details:
- NDMA recommendations:
(1) Use of Synthetic-Aperture Radar imagery to automatically detect changes in water bodies, including new lake formations, during the monsoon months.
(2) Reduce the volume of water with methods such as controlled breaching, pumping or siphoning out water to manage lakes structurally.
(3) Reduce the volume of water by making a tunnel through the moraine barrier or under an ice dam.
(4) Restrict constructions and development in GLOF/LLOF prone areas as a very efficient means to reduce risks at no cost
- India’s Preparedness:
(1) Some work on identification of such lakes has been done by CWC.
(2) There is work on a robust early warning system, and a broad framework for infrastructure development, construction and excavation in vulnerable zones in progress.
(3) Unlike other countries, there are no uniform codes for excavation, construction and grading codes in India.
(4) There are no widely accepted procedures or regulation in India for land use planning in the GLOF/LLOF prone areas.
Source : Indian Express