Uttarakhand disaster kills or misses more than 200 people – could happen again

The Tapovan Vishnugad hydroelectric power plant was destroyed after a devastating debris flow on February 7, 2021. Credit: Irfan Rashid, Department of Geoinformatics, University of Kashmir

The causes and extent of deadly debris flows in winter have been identified in Uttarakhand, India.

Uttarakhand, India, experienced a humanitarian tragedy on February 7, 2021, with debris and water walls flowing down the valleys of the Rontigado, Rishiganga, and Dhauliganga rivers.

The event began when a glacier-carrying rock wedge collapsed from a steep ridge in the Himalayas. The resulting debris flow destroyed two hydropower plants, killing or missing more than 200 people.

A self-organized coalition of 53 scientists met a few days after the disaster to investigate its causes, extents and consequences. The researchers determined that the cause of the flood was not the lake or the divergent river, but the melted rocks and glacier ice during the fall. This will help researchers and policy makers more accurately identify the dangers that are occurring in the area.

The study, which created a computer model of the flow using satellite images, seismic records, and witness videos, will be published today (June 10, 2021). Science..

Chamori rocks and ice avalanches

Computer modeling of Chamori rocks and ice avalanches. Credits: Ashim Sattar.Zurich

“When I was reading the news over coffee the morning of the event, I saw a headline about the Himalayan disaster,” said co-author David Shen. University of Washington Associate professor of civil engineering and environmental engineering. “I sat in front of my computer and took out the satellite image I got that morning. When I saw a cloud of dust going down the valley, I started sending emails to other scientists and they Asked if they were working on this. One mail thread quickly went to 5 and then 10 and then for the next 2 weeks most of our waking hours were spent replying. I did. “

The first hypothesis about the cause of the event suggested a glacial lake outburst flood. However, the team determined that there was no glacial lake near the site large enough to cause a flood.

“Access to high-resolution satellite imagery and research software and expertise in satellite remote sensing were essential to get a bird’s eye view of how the event unfolded.” Environmental engineering. “We worked with a French collaborator to coordinate the satellite collection within a few days of the event and quickly process the images to derive a detailed topographic map of the site.”

Researchers compared images before and after the event with topographic maps to record all changes and reconstruct the sequence of events.

Dan Sugar, an assistant professor at the University of Calgary, said the lead author of the paper, Dan Sugar, said:

The dark areas were found to be scars left by the lost 35 million cubic yards of rock and glacier ice. This is enough material to cover Washington DC with a layer 3 feet deep.

“This caused a huge landslide that triggered a series of events, resulting in huge deaths and destruction,” said Sugar, a former assistant professor at the University of Washington Tacoma.

Researchers used maps to determine how far ice and rock masses had fallen.

“The failed block fell more than a mile before it hit the bottom of the valley. Applying this height to the context, imagine stacking 11 Space Needles or 6 Eiffel Towers vertically. “Bhushan says.

Larger teams were then able to quantify how the crushed rock and ice were redistributed downstream.

“When the block fell, most of the glacier’s ice melted within minutes, resulting in a large amount of water associated with the flood,” said Bhushan. “This is very unusual. Normal rock landslides and snow / ice avalanches could not produce so much water.”

For Boushan, the job was personal.

“In general, PhD research projects are very niche. It can be difficult to explain to parents why it is important to measure glacier dynamics,” says Bhushan. “But because of the scale of this disaster, my family and friends who returned to India were very interested in how this event unfolded and they expected me to give an answer. These interactions have given me a sense of belonging and motivation that some of my research can be immediately useful to society. “

The team also used satellite imagery archives to show that a former large ice block was pushed out of the same ridge and collided with the same valley in recent years. Researchers suggest that climate change is likely to increase the frequency of such events and that the larger scale of modern disasters should be considered before further infrastructure development in the region. I will.

“These alpine rivers are attractive for hydropower projects and we need to better understand the full range of potential alpine hazards,” Shean said. “Lessons learned from this effort We hope to improve our ability to respond to future disasters and guide life-saving policy decisions. “

Reference: June 10, 2021, Science..
DOI: 10.1126 / science.abh4455

In addition to Shean, Bhushan, and Shugar, 50 co-authors from 14 countries have been added. The list of co-authors includes water policy experts and social scientists, in addition to geoscientists. Shean and Bhushan NASA NASA Geospace Science and Technology Fellowship High Mountain Asia Team and Future Researchers. Other co-authors have been funded by various government agencies such as India, Canada, France, Germany and Switzerland. The satellite images used by the UW team were provided by MAXAR, Planet, ISRO, and CNES, the French government’s space agency. Uttarakhand disaster kills or misses more than 200 people – could happen again

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