The devastating disaster due to intensifying effects leading to flash flood in Rishiganga basin in Chamoli Uttarakhand on February 7 is reminiscent of the Kedarnath tragedy.An avalanche/landslide in combination with breakage of rock/ice glacier might be the reason.However, an avalanche/landslide and/or breakage of rock/ice glacier might not be the sole factor for sudden deluge of water volume leading to flash flood. There should be trapped water at surface area or sub-surface, resulting in an evaluation if a glacial lake is formed at the same time.
In high mountainous surfaces, melting of glaciers due to worldwide warming resulting in higher warming rates over higher elevation than lower elevation is seen. This situation increases risk of glacial-related threats.
One of these risks is Glacial Lake Outburst Floods (GLOFs)– formed due to glacier(s) retreat, essentially forming water body behind moraine or ice ‘dams’. These ‘dams’, which act as an embankment, as soon as damaged and/or weak, will result in glacial lake breaching. It will unexpectedly discharge substantial volumes of water, debris, slurries, etc. Such outbursts have the potential of launching countless cubic meters of water in a couple of hours, causing catastrophic flooding downstream with serious damage to life and property. GLOFs develop as a repercussion of a series of different processes, for example, mass movement into lakes, glacier/ice front calving into lake, progressive enlargement of lake, increasing lake levels leading to overflow, mechanical rupture/failure of dam, hydrostatic failure, degradation of dam or melting of ice cores in dam, earthquakes, a flood wave from lake situated upstream and extensive rains or snow melt.GLOFs have become a severe hazard in the mountain region in current years due to increased human settlements, anthropogenic and other developmental activities into locations which were occupied and were not developed previously. There are numerous glacial lakes in Indian Himalayan region (IHR). A soon to be released research study (in press) by a group of scientists including me, analyzes the issue of GLOFs in the Indian Himalayan Area. An extensive inventory exposes a total of 4,418 glacial lakes within the Indian Himalayan Area. Besides, an overall l of 636 Trans Border glacial lakes, which can possibly flood the IHR, were also identified.Glacial lakes in the IHR cover an area of 428.71 sq km. Of the four major types of lakes, bedrock (67%) and morainedammed (25%) are most frequent. In Jammu & Kashmir, Sikkim, and Arunachal Pradesh 57-84% of the lakes are dammed by bedrock, while in Uttarakhand and Himachal Pradesh 76-80% of the lakes are moraine-dammed. Ice-dammed and other lakes are not so common, when compared to other lake types.To the best of our understanding, this is the most recent and most total inventory of glacial lakes in IHR, and the first research study to methodically consist of the lakes from which Trans Boundary GLOFs could originate and influence the downstream regions of IHR.