The Chamoli Disaster, as the Flash Flood incident on 7th February 2021 is commonly known as, occurred in the outer Garhwal Himalayas in the state of Uttarakhand, India. 204 people lost their lives & the 13.2 MW Rishiganga Small Hydro Project, being closest to the disaster's source (15 kms uphill), faced its destructive brunt the most. It was hit by a mass of rock and water flowing at 90 km / hour and was completely destroyed as a result. Some of the rock boulders were >20 m in diameter wiping out anything that came in its path, including 20 hectares of forest, bridges and other infrastructure.
By the time the debris-laden flood flow reached the larger, 520 MW Tapovan-Vishnugad Hydro Project 10 km further down the valley, it was still flowing at a malevolent 60 km / hour - severely damaging the under-construction plant, blocking the tunnels and fatally trapping the manpower working there.
While most of us would have seen the devastating flood footage, you may be surprised to know that the root cause of the flash flood was not validated until last month (June 2021), first by a group of 53 researchers who published their report in the journal Science (10th June) and later by researchers at Geological Survey of India (29th June).
Initially, various theories were propounded - glacial burst, landslide, rockslide etc. However, the research findings indicate that the disaster was a 'Rock & Ice Avalanche' triggered by the sudden collapse of a massive glacier-covered rock (500 m at is widest, 1500 m at its longest and 180 m thick approx.) on the steep northern face of the 6 km high Ronti (Raunthi) mountain's peak. The glacier-covered rock had a free fall for much of its initial 2 kms descent. When the 27 million cubic metres of material (80% rock, 20% ice) hit the Ronti Gad valley floor - the energy released was equivalent to 15 Hiroshima atomic bombs! melting the snow and ice instantaneously and creating a hyper-mobile flood of water and rock debris which wreaked havoc on anything in its path till a full 35 kms downstream, including the two ill-fated hydro projects stated above.
This article in BBC is a very good explainer of the incident and prompted me to check Sentinel-2 optical satellite imagery and inspect the disaster's source for myself - the result of which I have captured in the video and the two sliders below.
Video: Visualizing the Source of the Avalanche using Satellite Imagery
Slider 1: 21st May 2020 (1 year prior) vs 5th Feb 2021 (2 days prior)
Slider 2: 5th Feb 2021 (2 days prior) vs 31st May 2021 (Post incident)
Chilling, isn't it?
While in hindsight everything does seem straightforward, the impact of this disaster would have been reduced had human eyes been monitoring the satellite imagery changes over a period of time. Satellites do generate terabytes of geo-data every day but only a miniscule percentage of it gets analyzed. This is where the significance of Artificial Intelligence comes in as it is beyond human will and capability to keep constant surveillance on earth observation data feed. This doesn't deflect the absolute necessity of having Early Warning Systems (EWS) in place for critical infrastructure such as the hydro power plants located in Uttarakhand's mountainous terrain.
Climate change did play a role in the dismantling of the glacier covered rock over a period of time - it was showing signs of displacement since 2016 - as well as due to a recent phenomenon - January 2021 was the warmest January on record in Uttarakhand in six decades and between 4th and 6th February 2021 heavy snowfall was followed by sudden warmer climate which would have considerably weakened the rock's binding to the peak - eventually culminating in the disastrous chain of events on 7th February 2021.
This incident also raises a question mark on the viability of developing such critical infrastructure projects in such ecologically sensitive areas. Uttarakhand is a fragile and disaster prone region - floods, forest fires, landslides are a common occurrence and these same plants were damaged by floods in 2013 and 2016. Which begs the question - Does adequate planning really take place?
If you were to read this article by Ms. Sunita Narain - a member of an inter-ministerial group assessing issues related to Ganga river - you'll be left aghast at the sinister designs of all those involved in the planning and sanctioning of hydro projects in Uttarakhand - the source of all the five headstreams of the river Ganga.
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