Chamoli: The collapse of a hanging glacier triggered the deluge that struck Uttarakhand’s Chamoli Sunday, scientists of the Dehradun-based Wadia Institute of Himalayan Geology (WIGH) said.
A five-member team of scientists from WIGH — an autonomous institute under the Department of Science and Technology — was deployed by the central government to examine what led to the floods. As part of their brief, the team visited parts of the impacted valley.
Discussing their findings, Dr Manish Mehta, who led the team, said, “First, the loose rock material that was on top of the hanging glacier came down to the valley bottom. And in the valley bottom, it dammed up the river stream that was coming from the Ronti glacier and created a pond.”
He added, “We are assuming that the pond remained there for a few days. After that, a rock mass fell on the pond and breached it.”
What followed were flash floods that damaged two hydropower projects, a bridge and buried dozens of people along the Rishi Ganga and Dhauliganga rivers. A total of 32 bodies have been discovered so far, with around 200 people still missing.
Satellite images captured in the aftermath of the deluge — showing a scar on the shoulder of the Nanda Ghunti peak, at a prominence called Ronti peak — have pointed towards a similar assessment about the cause of the floods.
The scar is believed to have been etched into the mountain after chunks of ice and rock broke off a wall of ice from a glacier on the Ronti peak.
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Danger lurks
Scientists from WIGH visited the glacial rock on Ronti peak. Dr Vinit Kumar, one of the team members, said the team was airlifted to access the glacier.
“The factors behind this event are related to the Ronti glacier. Below the Ronti glacier, there is a peak called Mrigthuni, where there is another hanging glacier. So, that hanging glacier was sitting on a rock that possibly broke first, following which a chunk of rock came out,” Kumar said, describing it as a “multi-episodic event”.
The deluge that occurred was a mix of water and slush, which residents here say they’ve never seen before.
“Based on the conditions here and the videos we saw (of the incident) and the way the debris has accumulated, it seems that the percentage of debris is higher in comparison to water,” said Mehta. “This was a mobile, viscous material. The (initial) part of the valley is deep, narrow, and has a steep gradient, it came with a lot of speed due to gravity.”
At Raini, where the Rishi Ganga Hydropower Plant site is located, and Tapovan, the site of the NTPC’s Tapovan-Vishnugad Hydropower Project, the valley opens up. As a result, Mehta said, “there was so much disaster”.
“This happened because the Himalayas are young mountains and the relation between the landslide and rockfall activities runs parallel with the origin of the Himalayas,” he said.
The scientists also corroborated the accounts of villagers from Paing, among the first to have felt the impact of the deluge, about the formation of a lake following the event.
“A little downstream from the Ronti glacier, the debris from the disaster has blocked all the catchments on the right bank and blocked all the streams. Right in front of Paing, there is a deep narrow valley, where a small stream comes from. So, this material has blocked that stream,” Mehta said. “A lake has formed there that can be dangerous for the future.”
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‘Fragile mountains’
Asked whether developmental activities along the Rishi Ganga Valley could have played a role in the deluge, Kumar said it is not possible to draw a “1 to 1 correlation”.
“Government also takes lots of effort in a project, they also form expert teams before putting anything. That’s why I don’t think this question can be answered by any one person, a scientist or economist, whoever that is,” he added. “So, a collective answer should come out whether it is effective or not.”
He pointed out that the central Himalayan region is ecologically very volatile.
“The area is highly prone to disasters because there are many steep slopes… That’s why Chamoli has been a buffer zone of earthquakes and triggers, because we receive 2-3 magnitude earthquakes in Chamoli,” he said. “When suppose, a 5 or 6 magnitude trigger will occur, the entire (rock) material will come down. And in the future, it may also create a disaster.”
This report has been updated to indicate that it was not the IAF that airlifted the team to access the glacier.
Also Read: Satellite images reveal 550m ‘scar’ left by Uttarakhand landslide in Nanda Ghunti glacier
Debris blocking streams, water accumulated over time, landslide letting loose the water in a torrent…looks like this can repeat again when a landslide again happens in same area.
Thanks for providing the details from Wadia Institute scientists…I am confused… landslide from Ronti Peak or Mrigthuni peak was responsible for the floods or was it both? Mrigthuni is behind Trishul as seen in Google Earth so it is not clear how a steep glacier from Mrigthuni could have affected Ronti Gad or Nanda Ghunti glacier.
Kudos to our scientistS for investigatings I am looking forward to our Indian scientists getting to the bottom of this in their report. Sounds like the Chamoli region with steep slopes is not to be trifled with in terms of hydropower infrastructure by blocking rivers and damming it.
The Chamoli disaster was a natural disaster, and certainly not correlated to climate change. However infrastructure development in these areas should take cognizance of the fact that such disasters can happen due to natural geohazards in the Chamoli region. The area should be consistently monitored by government scientists for glacial ponds, glacial lakes, steep hanging glaciers/rocks and dammed streams to establish an early warning system.