Glacial Lake Outburst Floods (GLOF)

Glacial Lake Outburst Floods (GLOF)

News: Flash floods occurred in north Sikkim after the South Lhonak Lake burst due to incessant rains. For years,
numerous studies highlighted the lake’s rapidly growing size and marked it as susceptible to glacial lake outburst
flood.

What is GLOF?
• Glacial lakes, like the South Lhonak Lake, are large bodies of water that sit in front of, on top of, or beneath a melting glacier.
• As they grow larger, they become more dangerous because glacial 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 glacial lake outburst floods or GLOF.

Which factors trigger GLOF?
• Earthquakes
• Extremely heavy rains
• Ice Avalanches
• These lakes are also often found in steep, mountainous regions, which means landslides or ice avalanches can sometimes fall directly into the lakes and displace the water, causing it to over-top the natural dam and flood downstream

How did South Lhonak lake become susceptible to GLOF?
• With the rising global temperatures, glaciers in Sikkim Himalayan have been melting rapidly, giving rise to many glacier lakes and expanding the already existing ones in the region. There are currently more than 300 glacial lakes in Sikkim Himalayan, according to the Sikkim State Disaster Management Authority, a 2020.

How can we prevent GLOF from happening?
Preventing Glacial Lake Outburst Floods (GLOFs) is a complex task due to the unpredictable nature of these events. However, there are several strategies that can be employed to mitigate their impact:
• Reduce the volume of water in the lake: The most important mitigation measure for reducing GLOF risk is to reduce the volume of water in the lake in order to reduce the peak surge discharge. This can be achieved through techniques like controlled breaching, pumping or diverting out water, digging a tunnel through the moraine barrier, or beneath an ice dam.
• Monitoring and Early Warning Systems: Implementing monitoring systems and early warning systems can help in predicting when these outburst floods will occur and how destructive they will be. This includes the creation of a network of satellite-based monitoring stations that could provide in situ and real-time data on GLOF risk.
• Climate Change Mitigation: Since climate change is a major factor contributing to the melting of glaciers and the formation of glacial lakes, efforts to mitigate climate change can also help prevent GLOFs.
• Research and Understanding: Continued research into the stability of the moraines damming glacial lakes is crucial. Understanding all potential major and minor drivers behind sudden surges of meltwater into headwater streams is vital for understanding the hazard profile of the region.