Collapse of Himalayan Glacier Cause of Devastating Debris Flow in India

Roughly 200 people are dead or missing because of the catastrophic avalanche and debris flow from earlier this year.

This photograph provided by Indo Tibetan Border Police (ITBP) shows a man reacting after he was pulled out from beneath the ground by ITBP personnel during rescue operations after a portion of Nanda Devi glacier broke off in Tapovan area of the northern state of Uttarakhand, India, Sunday, Feb.7, 2021. (Indo Tibetan Border Police via AP)

(CN) — The torrent of rock and ice that rushed down the Dhauliganga River this past February in northern India scoured valley walls hundreds of feet above the valley floor. A deluge of large boulders and gray water washed away homes, temples, bridges and dams downriver, resulting in over 200 people either dead or missing.

The avalanche and subsequent floods were set off by the collapse of a Himalayan glacier in the Uttarakhand region in India, which is now referred to as the Chamoli disaster. Satellite imagery of the northern face of Ronti Peak shows that a massive avalanche, containing roughly 70 million short tons of ice and rock, cascaded down on Feb. 7, 2021, according to a study published Thursday in the journal Science.

The study is a means to illustrate the disaster in slow-motion and better explain how it attained such a devastating effect.

First, the avalanche started from a sheer vertical drop on Ronti Peak at around 12,000 ft. Researchers estimate that there have only been two other recorded avalanche events from those heights.

Second, the amount of rock to ice was greatly imbalanced. The study’s findings put it at 80% rock and 20% ice that made up the initial avalanche. Frictional heating would have nearly melted all the ice in a short amount of time, turning it into a wall of slush. While there was a storm system that passed through the region days before the avalanche, it played a minor role in the flow of debris. River water, groundwater ejected from the earth, melting snow, wet sediment and water released from the hydroelectric plant were also minimal actors in the debris flow according to the study authors.

“However, not all large, high-mountain rock and ice avalanches transform into highly mobile debris flows that cause destruction far from their source,” the study authors wrote.

The Tapovan Vishnugad and Sridhar hydropower plants were damaged by the deluge with estimates of damages totaling $223 million. The study authors point to the plants’ proximity to the region’s steep peaks as explanation for the high death toll and high infrastructure damage cost.

“The location of the failure was due to the extremely steep and high relief of Ronti Peak,” write the study authors. “Nearly all (190) of the 204 people either killed or missing in the disaster” were workers at the two plants.

The study authors raise concerns about the development of hydroelectric power projects in the region.

“The disaster tragically revealed the risks associated with the rapid expansion of hydropower infrastructure into increasingly unstable territory,” write the study authors. “Enhancing inclusive dialogues among governments, local stakeholders and communities, private sector, and the scientific community could help assess, minimize and prepare for existing risks.”

When asked what the average reader should take away from the study’s findings, lead author Dan Shugar from the University of Calgary in Canada said people should be aware that high mountains are “very dynamic places and constantly evolving.”

“And so what is deemed safe today may not be as the climate changes,” Shugar said in an email. “In particular, we need to be much more diligent about hazardous cascades when thinking about major infrastructure projects in mountainous environments.”

The stalking question of whether the avalanche was spurred by climate change is a difficult one to assess according to the study authors.

“Although we cannot attribute this individual disaster specifically to climate change, the possibly increasing frequency of high-mountain slope instabilities can likely be related to observed atmospheric warming and corresponding long-term changes in cryospheric conditions (glaciers, permafrost,” write the study authors.

While climate change is leading to more frequent large rock avalanches across the globe, Shugar says there is no “smoking gun” in the Chamoli disaster that points to this.

Multiple variables played a role in the Chamoli avalanche including the possible thermal disturbances in permafrost bedrock, stress changes from the collapse of other glaciers and increased melt water infiltration during warm periods says the study authors. The peak has seen other mass failures in recent decades, but never anything like what happened earlier this year.

Early theories behind the Chamoli disaster pointed to a glacial lake dam bursting and sending out all the water down the peak. But that proved to be wrong, Shugar said.

“In my opinion, it is important to understand what the actual cause was so that we can plan better for future development,” Shugar said. “There were no glacial lakes in the valley that saw the flood. If we were only concerned with glacial lakes, we would therefore think this valley was totally safe, which is obviously untrue.”

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