GLACIAL LAKE FLOODING

  • India and Pakistan make up one-third of the total number of people globally exposed to glacial lake outburst floods — around three million people in India and around two million people in Pakistan.
  • According to a 2020 study, the number and total area of glacial lakes worldwide have increased by about 50 per cent since 1990.
  • Around 15 million people across the world face the risk of sudden and deadly flooding from glacial lakes, which are expanding and rising in numbers due to global warming, according to a new study.
  • More than half of those who could be impacted live in four countries: India, Pakistan, Peru and China.
  • 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, researchers of the latest study .

GLOF

  • A glacial lake outburst flood is a type of outburst flood occurring when water dammed by a glacier or a moraine is released.
  • A water body that is dammed by the front of a glacier is called a marginal lake, and a water body that is capped by the glacier is called a sub-glacial lake.
  • When a marginal lake bursts, it may also be called marginal lake drainage.
  • When a sub-glacial lake bursts, it may be called Jaokulhlaup.
  • GLOF can be triggered by several reasons, including earthquakes and ice avalanches.
  • GLOFs often result in catastrophic flooding downstream, with major geomorphic and socioeconomic impacts.
  • GLOFs have three main features:
  • They involve sudden (and sometimes cyclic) releases of water.
  • They tend to be rapid events, lasting hours to days.
  • They result in large downstream river discharges (which often increase by an order of magnitude).
  • 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.
  • 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 retreat will 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.”
  • “So, 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.

Recent study findings:

  • 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.
  • As mentioned before, 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.
  • What also matters is the 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.
  • In fact the most dangerous catchment in the world in our 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.
  • Yet most of the previous studies done in the field have focused on the Himalayas rather than the Andes.
  • “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.

GLOF – Prevention

  • Reducing the risk of GLOFs is complex and no single solution would work.
  • “Limiting climate change and keeping warming under 1.5 degree Celsius is a big one as this will help slow the growth of glacial lakes, but unfortunately a certain amount of ice loss is already ‘locked in’ – if we stopped all emissions today GLOF hazard will continue to increase for several decades.”
  • There is a need to find effective measures by working with national and regional governments, as well as communities themselves.
  • This includes working at the local level and finding appropriate measures for the threatened populations.

SOURCE: THE TIMES OF INDIA,THE INDIAN EXPRESS

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