GLACIAL LAKES OUTBURST FLOODS (GLOF)

• Glacial lakes result from shrinking glaciers. Once the water is released from them, it could cause flooding in the downstream areas. This is known as glacial lake outburst floods or GLOF
• Although GLOFs have been taking place since the ice age, the risk has increased multifold due to climate change
• GLOFs can prove to be catastrophic as they mostly arrive with little warning and result in large-scale destruction of property, infrastructure, and agricultural land. They can also lead to the death of hundreds of people
• As the climate continues to warm, glacier retreatwill form larger and more numerous lakes
• At the same time, lakes are likely to become more exposed to GLOF ‘triggers’, such as a large landslide or ice avalanche entering the lake, displacing water, and causing the natural dam that impounds the lake to fail
• lakes that perhaps aren’t a concern at present may become a concern in the future, and entirely new and potentially dangerous lakes may form
• According to a 2020 study, the number and total area of glacial lakes worldwide have increased by about 50 per cent since 1990

• In order to identify the areas and communities that are most in danger from GLOFs, the researchers used existing satellite-derived data on different locations and sizes of glacial lakes with a global population model and a series of population metrics
• Moreover, the researchers also looked at levels of human development and corruption in these zones to determine how vulnerable local communities may be when floods occur
• The paper estimates that 15 million people live within the 50 km danger zone of glacial lakes
• It adds that populations in High Mountains Asia (HMA),  a region stretching from the Hindu Kush all the way to the eastern Himalayas  are the most exposed and on average live closest to glacial lakes with around one million people living within 10 km of a glacial lake
• India and Pakistan make up one-third of the total number of people globally exposed to GLOFs  around three million people in India and around two million people in Pakistan
• Another interesting finding of the study is that the glacial flood risks don’t only depend on the size and number of glacial lakes in an area
• Number of people living in the area, their proximity to the danger zone as well as the levels of social vulnerability
• For instance, areas like Greenland and Canada, which have a large number of glacial lakes, have very few people who are vulnerable to GLOFs as their population and corruption levels are low
• While the number and size of glacial lakes in these areas (India and Pakistan) isn’t as large as in places like the Pacific Northwest or Tibet, it’s that extremely large population and the fact that they are highly vulnerable that means Pakistan and India have some of the highest GLOF danger globally
• The most dangerous catchment in the world in according to study is Khyber Pakhtunkhwa in Pakistan
• However, the most surprising bit for the scientists was to find Peru ranking third globally in danger levels
• They point out that in the past two decades, due to climate change, glacial lakes across the Andes have increased by 93 per cent, in comparison to 37 per cent in high-mountain Asia

• Glacial lakes are large bodies of water that sit in front of, on top of, or beneath a melting glacier
• As they grow larger in size, 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
• 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
• In 2013, one such event took place in Uttarakhand’s Kedarnath when the region witnessed flash floods along with a GLOF caused by the Chorabari Tal glacial lake, killing thousands of people