The Chamoli Disaster, as the Flash Flood calamity of 7th February 2021 is commonly known as, occurred in the outer Garhwal Himalayas in the state of Uttarakhand in India. 204 people perished in this fateful tragedy & the 13.2 MW Rishiganga Small Hydro Project situated 15 kilometres uphill, by virtue of being directly in line of the flash flood path, was completely destroyed.
Imagine being hit by a flowing mass of rock hurtling at 90 kilometers / hour (56 mph)!
Several boulders were found to be >20 metres in diameter and the floods carrying them wiped out everything in its path - twenty hectares of forest, bridges, critical infrastructure, residential units etc. By the time the debris-laden water flow reached the larger, 520 MW Tapovan-Vishnugad Hydro Project 10 kilometres further down the valley, it was still flowing at a malevolent 60 kilometres / hour (37 mph) - severely damaging the under-construction Power Plant, blocking its tunnels, and fatally trapping the manpower - 140 of them - working there.
Those of you who would have seen the devastating Flash Flood footage in the news would know that in the immediate aftermath, various theories were propounded as the cause behind the calamity- Glacier Burst, Landslide, Rockslide etc.
The root cause was validated last month (in June 2021, ~ 3 months after the disaster), first by a group of 53 researchers who published their findings in the journal Science (10th June) and subsequently by researchers from Geological Survey of India (29th June).
Video 1: News Report on what caused the Flash Flood in Chamoli, 2021
The research reports indicate that the Flash Floods were a 'Rock & Ice Avalanche' which was triggered by the sudden collapse of a massive Glacier-covered Rock - 500 metres at is widest, 1500 metres on its longest end and nearly 180 metres thick - on the steep northern-face of the 5600 metres tall Ronti (Raunthi) mountain.
The Glacier-covered Rock had a free fall for much of its initial 2 kms descent. When the estimated 27 million cubic metres of material comprising 80% rock and 20% ice hit the valley floor (Ronti Gad) - the energy released was equivalent to the detonation of 15 Hiroshima Atomic Bombs! - the release of this ferocious energy melted the snow instantaneously, creating a highly mobile avalanche of water and debris which wreaked havoc on everything in its path till a full 35 kilometers downstream, including the two ill-fated Hydro power projects.
This article posted on BBC elaborately explains the Chamoli Disaster and it prompted me to use Sentinel-2 Optical Satellite Imagery to inspect the source of the disaster for myself - before and after the incident - what I spotted has been captured in the video below and in the two Sliders attached subsequently.
Video 2: Exploring the source of the Rock & Ice Avalanche in Chamoli,2021 using Satellite Imagery
Slider 1: 21st May 2020 (1 year prior) vs 5th February 2021 (2 days prior)
Slider 2: 5th February 2021 (2 days prior) vs 31st May 2021 (a few months later)
Chilling, isn't it?
While in hindsight everything tends to seem straightforward, the impact of this disaster could have been greatly reduced had someone been monitoring Satellite Imagery around Ronti's peak. Alas, while satellites generate terabytes of imagery every day, only a miniscule portion of it gets analyzed. If anything, this highlights the value that Artificial Intelligence can bring to the table - as it is beyond human capability to continuously surveil the enormous quantities of Earth Observation data generated every moment. Additionally, this does not deflect the absolute necessity of having 'Early Warning Systems (EWS)' in place, particularly in those remote regions where critical infrastructure projects tend to be located.
It is important to recognize the role Climate Change played in the dismantling of the Glacier-covered Rock on Ronti mountain over a period of time (which as a matter of fact was showing signs of displacement since 2016) as well as due to recent weather phenomenon - a) January 2021 was the warmest January on record in Uttarakhand in six decades and b) heavy snowfall was followed by sudden warm temperatures between 4th and 6th February 2021. It is likely that these would have contributed to the considerable weakening of the Rock's binding to the Ronti mountain face, eventually culminating in the tragic sequence of events on 7th February 2021.
This incident also raises a question mark on the wisdom of developing Critical Infrastructure projects in environmentally-sensitive terrains. Uttarakhand has a fragile history replete with instances of Floods, Forest Fires and Landslides. The two destroyed Hydro Power Plants were itself damaged by floods in 2013 and 2016 respectively.
Which begs the question - 'Does adequate Risk Assessment take place before embarking on a Critical Infrastructure Project?'
If you were to read this article posted by Ms. Sunita Narain - a member of an inter-ministerial group assessing issues related to the Ganga - you'll be left aghast at the sinister designs of all those involved in the planning and sanctioning of Hydro Projects in the state of Uttarakhand - where all the five headstreams of the river Ganges, a lifeline to millions of Indians, reside.
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