A view of Raini village, following an avalanche in Joshimath, in Chamoli, Uttarakhand.
This is the reconstruction of events pieced together by two teams of five scientists from the Dehradun-based Wadia Institute of Himalayan Geology on the basis of their field visit to the region. The teams left on February 8, the day after the terrifying flood in which at least 35 lives are lost and over 170 are missing. The raging waters also swept away the Rishiganga and Tapovan hydel projects. The researchers’ hypothesis is based on surveillance by teams in helicopters as well as satellite images; the high altitude and the snow-covered region make the area inaccessible. “Our scientists observed evidence of the rock fall — a clear scar is observed at that height. The broken part of the glacier was also seen at the bottom,” says Kalachand Sain, director, Wadia Institute.
While experts now agree that an avalanche of rock and ice was the trigger, the source of the huge volume of water which surged down, reminiscent of the devastating 2013 floods in Uttarakhand, is still not clear. Sain says some water would have accumulated in the artificially created temporary dam and there might have been small pockets of water bodies.
“Ice or rock avalanche fell into the valley that had melt water from the glaciers. Blocked temporarily, it formed a small lake. When the water temperature rose, the ice — mixed with sediments and rock — melted, creating more space for the water. Hydrostatic pressure was built up and pushed at different places. The sediments were pushed down and because of the elevation, it came down with accelerated velocity, creating havoc”
Anil V Kulkarni, distinguished scientist at the Divecha Centre for Climate Change at the Indian Institute of Science, has another explanation. Based on a modelling tool designed by the Divecha Centre to map depression in the bedrock below glacier ice, Kulkarni says the Raunthi glacier likely had a water pocket inside, with about 1.5 million cubic metres of water. “Our understanding is that because of tremors, the water was released. That’s why there was a flash flood,” says Kulkarni, who has spent four decades researching glaciers. Sain says the data and images they have seen so far make them sceptical about a glacial lake for now.
AgenciesSatellite image, released by Planet Labs, of the area before the ice broke off.
More details will emerge in the days and months to come. Meanwhile, experts say there is an urgent need to lend more attention to studying the glaciers in the region at a time when temperatures are rising around the world. “There are close to 1,500 glaciers in the Uttarakhand region, more than 10,000 glaciers in the entire Himalayan region. The impact climate change has on glaciology and the consequences for the downstream system need to be studied from different angles,” says Sain.
“A huge ice avalanche fell on the land vacated by the Raunthi glacier, creating micro-triggers. Our model suggests the Raunthi glacier had a water pocket inside, with 1.5 million cubic metres of water. Due to the tremor, the water was released, went through the avalanche and melted quickly. When the water was gushing down, minor avalanches took place along the banks.”
A January 2021 research paper, published in Nature, on glacier-related landslides in the high mountains of Asia (HMA) and which analysed data of the last 21 years found an “increasing trend of large landslides in the HMA over the last decade. A decline in glacier area is associated with the increase in landslide area.”
DP Dobhal, a glaciologist who retired from the Wadia Institute and who was hailed by Time magazine as a “hero of the environment”, says it is critical to do detailed studies of glaciers in the region, particularly with all the developmental work in the area. “Accessibility is a major challenge in studying glaciers in the Himalayan region but we can use remote sensing techniques. Studies must be done on a priority basis, so that mitigation measures can be taken,” says Dobhal. Importantly, he says, when hydel projects are planned in the region, glaciers must be taken into consideration. “You must know how many glaciers are there, how many (glacial) lakes and the frequency of avalanches. Most importantly, we must know how much water we have in the form of glaciers.”
“Since the rock/ice avalanche contained a large amount of ice, some of that would have melted. It’s possible that there was older, buried ice at the valley bottom that could have melted instantaneously. It’s also possible that the debris may have temporarily blocked the Rishiganga, creating a small lake, which would have burst through the dam, generating the flood.”
Others suggest setting up a special centre dedicated to monitoring glaciers. “We should establish a centre with modern technology like satellite data and use artificial intelligence and machine learning to help in decision-making, not just modelling,” says AL Ramanathan, professor, School of Environmental Sciences at JNU, Delhi. Improved monitoring would also help in adopting techniques to mitigate potential disasters. “We cannot control the climate, but we can adapt and vulnerabilities can be identified so that modifications can be carried out and disasters can be reduced.”
Kulkarni adds that the information that scientists gather also needs to be shared with local communities. “As glaciers start retreating and melting, this will be a major issue for all communities, particularly those living in the hills. We require some sort of mechanism to transfer scientific knowledge to the local communities,” he says.