Glacial lake outburst floods (GLOFs)

GEOGRAPHY/ ENVIRONMENT

Topic:

• GS-1: Important Geophysical phenomena such as earthquakes, Tsunami, Volcanoes etc.
• GS-3: Conservation, environmental pollution and degradation, environmental impact assessment. 

Glacial lake outburst floods (GLOFs)

About GLOFs

• Glaciers are large bodies of ice moving slowly. 
• Lake Formation: 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. 
• Lake bursts: When such a lake (moraines) breaches, it is known as glacial lake outburst flood. GLOFs occur from an unstable natural dam formed from a glacial retreat.
• Causes for GLOFs: The moraine dammed lakes weaken as the water level rises and the glacier retreats. They might crumble under pressure from the swelling lake, leading to massive floods.The outburst of water can also happen due to erosion, an avalanche of snow or rock, an earthquake or volcanic eruptions under the ice.
• In the Hindu Kush Himalaya, moraine-dammed glacial lakes are common and numerous GLOF events have been traced back to the failure of moraine dams. 
• Climate Change and GLOFs: The glacial outbursts are also related to global warming. As the temperature soars during summers, the glaciers retreat, leaving behind water-filled, unstable moraine dammed lakes.
• Possibility of frequent occurrence in future: Glacier retreat and permafrost thaw are projected to decrease the stability of the mountain slopes and increase the number and area of glacier lakes, according to the latest assessment reports of the UN Intergovernmental Panel on Climate Change. Tus, there is a possibility of increase in events like GLOFs

Reducing GLOFs

• Identifying and mapping such lakes: Potentially dangerous lakes can be identified based on field observations, records of past events, geomorphologic and geotechnical characteristics of the lake/dam and surroundings, and other physical conditions.
• A robust early warning system, and a broad framework for infrastructure development, construction and excavation in vulnerable zones needs to be developed by state government in collaboration with Universities & Central govt.
• Leveraging Technology: NDMA has recommended use of Synthetic-Aperture Radar imagery to automatically detect changes in water bodies, including new lake formations, during the monsoon months. Methods and protocols could also be developed to allow remote monitoring of lake bodies from space.
• Structural measures to prevent their sudden breach: 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.
• Regulating Developmental activities: Restricting constructions and development in GLOF prone areas is a very efficient means to reduce risks at no cost. Construction of any habitation should be prohibited in the high hazard zone. 
• Existing buildings are to be relocated to a safer nearby region and all the resources for the relocation have to be managed by Central/State governments. 
• Monitoring Mechanism: New infrastructures in the medium hazard zone have to be accompanied by specific protection measures. There should be monitoring systems prior to, during, and after construction of infrastructure and settlements in the downstream area.

Connecting the dots :

• Landslides
• Polar vortex