Geological Survey of India assessing the triggering factor that led to flash flood in Chamoli

New Delhi - Geological Survey of India is assessing the triggering factor that led to flash flood in Chamoli. Dr. Ranjit Rath, DG GSI while addressing a press gathering at Shastri Bhawan in New Delhi on the Glacial Outburst in Chamoli said, " The glaciers in the Himalayas are retreating under climate change scenario.  Such recession is a global phenomenon. With the passage of time, some of the glacial

 lakes near the terminus often coalesce together and form large glacial lakes dammed by glacial moraines. The constitution of the moraines comprising loose boulders, gravels, sand admixture often containing dead ice, imparts inherent weakness to these dams. These lakes are quite common on the debris-covered Himalayan glaciers wherein the lower part of the glacier moves very slowly and at times remains almost stationary. The breach glacial and outbursts, termed as Glacial Lake Outburst Flood (GLOF), can result in the discharge of a huge volume of water leading to severe damage in the areas falling in the downstream region.
    The glacial lake can breach due to sudden triggering mechanism, viz. calving of the snout, avalanche/ landslide in near the lake periphery, piping in the moraine dam, and subsequent subsidence, cloud burst in the catchment, a large earthquake, etc.
  As a follow up of the Kedarnath tragedy (June 2013) in Uttarakhand, a compilation of an inventory of glacial lakes of Uttarakhand Himalaya and to identify high-risk areas for Glacial Lake Outburst Floods (GLOF) was taken up between 2014-16. Based on remote sensing and multispectral data, the glacial lakes identified in Uttarakhand is 486 glacial lakes (excluding supra-glacial lakes). Out of these 13 are found to be vulnerable.
 As per the Inventory prepared by GSI on glacial lakes in Uttarakhand, a total of 71 lakes of different sizes and types are reported in upper reaches of Rishiganga and Dhauliganga valley. GSI is in the process of finding out the focal point of this unfortunate flash flood event. Right now, it is not clear whether the flood is a typical Glacial Lake Outburst Flood (GLOF) or some temporary damming due to a landslide and avalanche that might have blocked the mainstream to form a temporary lake which got burst. A team of experts is assessing the damage as well as the triggering factor responsible for the outburst. However, people living close to the river should be properly alerted.”