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How satellites can help us understand deadly avalanches
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How satellites can help us understand deadly avalanches

A gif showing the height of debris that broke off a hanging glacier and fell down a mountain in India in 2016.


A little over a decade ago, one of most destructive was discovered. Rock-ice avalanches in the Indian HimalayaA small township was devastated by the devastating impact of the hurricane, which claimed more than 200 lives, many bridges, roads, and two power plants.

It is commonly known as the Chamoli disaster. It was unprecedented in its size. Despite its size, it was made up of Only 20% of ice is found in rock, while 80% is in ice.The avalanche mass could travel approximately 13km downstream, before it became a debris stream, causing a flash flooding in the Rishiganga-Dhauliganga rivers.

Scientists around the globe were attracted to the scale of the disaster. More than ten research articles on the disaster have been published over the past few months. InvestigationsExplore possible causes and potential changes in the valley.

Remote sensing

Due to the lack of field measurements in this remote area, all published studies extensively used Earth Observation data (EO) from Satellites for remote sensing. Special cameras on EO satellites capture energy that is either emitted or reflected from the Earth’s surface or its atmosphere, so remote sensing helps monitor particular environments quickly and effectively.

Space agencies such as NASAThe European Space AgencyCompanies such as Planet Labsprovide free images of Earth at medium-to high resolution, encouraging independent research. In fact, Planet Lab’s PlanetScope satellites were able to capture the Chamoli disaster in real-time.

These satellites are becoming more and more useful in understanding high mountain hazards. Online geo-visualization platforms such as Google EarthYou can easily and quickly analyze visuals by comparing high-resolution images. You can find our StudyThanks to the rich archive remote sensing data, we were able simulate and reconstruct both the Chamoli disaster as well as an earlier ice avalanche at this site.

Avalanche hot spot

Our research began with an interesting observation, also reported in Other studiesThe Chamoli disaster site is a hotspot of avalanches. We identified two ice and several snow avalanches within the same valley by scanning through satellite images over the past 20 years.

A gif showing the height of debris that broke off a hanging glacier and fell down a mountain in India in 2016.
The 2016 avalanche left the area more vulnerable to the 2021 avalanche.
Anshuman Bhadraj/University of Aberdeen, Author provided

Ice avalanches caused by breakage of a hanging glacier in early 2000 and again in September 2016 were massive, consisting of approximately 10 million m³ of glacial ice, filling around 3.5km of the valley floor with debris deposits that reached heights of up to 50m. It is interesting that the Chamoli disaster took place within 4.5 year of the September 2016 Ice Avalanche.

The 2021 disaster was caused by an avalanche which, although more than 2.5 times more voluminous than the 2016 event, was made of 80% of rocks contrary to the pure icy composition of 2016’s avalanche.

This is a rare sequence of two huge and distinct ice avalanches which originated from the same elevation, and struck the same valley over a five-year period. It was a unique natural testbed that allowed us to study how frequent avalanches with different levels of ice can differ in terms both of their destructive power as well as their run-out.

A gif showing the height of debris that broke off a hanging glacier and fell down a mountain in India in February 2021.
The 2021 Chamoli Avalanche was made up of 80% rock & 20% ice. This made it more deadly.
Anshuman Bhadraj/University of Aberdeen

Predicting what the future will look like

We adopted an integrative approach and studied both the pre and during-event flow characteristics in the 2016 and 2020 avalanches. We observed both short-term as well as long-term changes in surface movement, which reached up to more than five times the normal values.

The ability to estimate surface movements has allowed us to track the trajectory and development of ice-avalanches in the past. 1973 was the year when movements were measured. first timeto predict its eventual collapse on an unstable hanging glacier. This field-based monitoring approach proved to be a success in 2014. accurate prediction of a hanging glacier “break-off” from the south face of the Grandes Jorasses in Italy, 10 days before the avalanche happened.

However, logistics problems in high-mountain areas make it difficult to conduct field-based efforts. Our observations, especially regarding the 2016 avalanche show that remote sensing movement estimations can not only provide greater coverage but also offer a more timely, cost-effective, safer and faster way to monitor hanging glaciers and potentially even predict large and deadly ice avalanches.

Remote sensing observations are not perfect and there are uncertainties. Therefore, more research is needed to identify statistically significant trends.

Use a Thermomechanical modelWe then simulated the September 2016 earthquake and the maximum impact it had on the valley. We discovered it was 6,000 kilopascal (a measurement of compressive strength) – big enough to make visible changes in the valley profile by adding erodible sediments, which could worsen any future event.

This part of the valley is also kept sufficiently lubricated by seasonal snow avalanches. The 2021 event was then simulated under two scenarios. One without specifying the erosion characteristics for the avalanche deposit from the past and the other with defined erosional zones.

The results indicate that the remaining valley deposits from past ice and snow avalanches likely aided the volume and flow of the 2021 rock-ice avalanche – which would explain its exceptional reach to the downstream population.

Although the past ice-avalanches of 2000, 2016 and 2016 did not cause any damage to property or life, they are recurring events that occur in this valley. However, it is difficult for us to predict their future impact when combined with other glacial hazards like the Chamoli disaster.

As global climate change accelerates, these life-threatening scenarios are also emerging in other mountain regions, with greater frequency, uncertainty, and impact. Satellites offer frequently updated images so that it is possible to understand the patterns of high-mountain dangers and protect infrastructure.


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