National Disaster Management Authority (NDMA) has taken up expeditions to glaciers at an altitude of 4500m and above to map their vulnerability to Glacial Lake Outburst Flood (GLOF).Of the nearly 7,500 glacial lakes in the Indian Himalayas, NDMA has finalised 189 high-risk lakes that require mitigation measures.
National Glacial Lake Outburst Floods Risk Mitigation Programme
- It is an initiative launched by the Government of India to address the risks posed by GLOFs.
- 16 teams went out for expedition out of which 15 teams completed their expedition. Another seven expeditions are underway.
- Of the 15 expeditions completed, 6 were in Sikkim, 6 in Ladakh, 1 in Himachal Pradesh, and 2 in Jammu and Kashmir.
- Teams on expeditions assess the structural stability and potential breach points of glacial lakes, gathering relevant hydrological and geological samples and data, measuring water quality and flow rates, identifying risk zones and making downstream communities aware.
Objective
- To assess hazards, install automated monitoring and early warning systems, and implement lake-lowering measures to mitigate glacial lake outburst flood (GLOF) risks.
- Lake-lowering measures are techniques used to reduce the volume of water in a glacial lake to mitigate the risk of a GLOF.
- NDMA is focussing on ground-truthing of selected 189 “high-risk” glacial lakes.
- Ground-truthing is the process of validating and verifying data collected through remote sensing or other indirect methods by comparing it with direct observations made on-site.
- Methodology to Prevent GLOF: Three activities are planned to be executed simultaneously.
- Placement of automated weather and water level monitoring stations and early warning systems
- Digital elevation modelling and bathymetry.
- Assessing best means to reduce the risk of that lake including by lake-lowering.
Need of the Study
- ICIMOD Findings: As per the International Centre for Integrated Mountain Development (ICIMOD), Hindu Kush Himalayas are experiencing rapid, irreversible changes due to climate change, increasing the risk of floods and landslides.
- Climate Change: Due to climate change, India faces hazards like extreme altered FDI (frequency, duration and intensity) of precipitation and extreme heat. It may lead to an increased number of flash floods.
Previous Incidents of GLOFs
- Nepal Incident: Recently, flash floods struck Thame, a village in the Khumbu region of Nepal which was due to an outburst flood from Thyanbo glacial lake.
- Sikkim Flash Flood: A catastrophic GLOF occured in South Lhonak Lake, Sikkim, in October 2023.
- Uttarakhand Flash Floods: A glacier breach-induced flood in February 2021 in Rishi Ganga valley resulted in over 200 deaths and significant damage to hydropower plants and Raini village.
GLOF
- A GLOF is a type of flood occurring when water dammed by a glacier or a moraine is released suddenly.
- When glaciers melt, the water in these glacial lakes accumulates behind loose naturally formed ‘glacial/moraine dams’ made of ice, sand, pebbles and ice residue.
- Unlike earthen dams, the weak structure of the moraine dam leads to the abrupt failure of the moraine dam on top of the glacial lake, which holds a large volume of water.
- A catastrophic failure of the dam can release the water over periods of minutes to days causing extreme downstream flooding.