Chamoli disaster due to a “rock and ice avalanche” which turned into a massive “debris flow”: study


The Chamoli disaster on February 7, 2021, which killed more than 200 people, was caused by an avalanche of rocks and ice that turned into a huge “debris flow” carrying rocks over 20 m in diameter. and eroded the valley walls up to 220 m above the valley floor. , says the latest disaster study published in the renowned academic journal ‘Science’.

Although the study stops before directly linking the disaster to climate change, it does indicate that the increasing frequency of instabilities in high mountain slopes may likely be related to “observed atmospheric warming and the corresponding long-term changes in cryospheric conditions. (glaciers, permafrost) ”.

He also warns of upcoming hydroelectric projects in Hill State.

“The disaster tragically exposed the risks associated with the rapid expansion of hydropower infrastructure in an increasingly unstable territory,” says the study titled – Huge avalanche of rocks and ice caused the 2021 disaster in Chamoli, in the Indian Himalayas.

The study was carried out by researchers from prestigious institutes in India and abroad as part of an international collaboration.

He adds that “human activities crossing the mountain cryosphere can increase risk and are common in the Himalayan valleys where hydropower development is proliferating due to increasing demand for energy, the need for economic development, and effort. transition to a low-carbon society “.

CLIMATE LINK

Expanding the possible link with climate change, the study highlights that air and surface temperatures have increased in the Himalayan region, with higher rates of warming during the second half of the 20th century and at elevations higher.

“Most of the Himalayan glaciers are shrinking and rates of mass loss are accelerating across the region. The retreat of the glaciers uncovers and destabilizes the mountain sides and strongly modifies the hydrological and thermal regimes of the underlying rock, ”he says.

He says the analysis suggests that “the regional climate and associated cryospheric changes could have interacted in complex ways with the geological and topographical setting to produce this massive slope collapse.”

He also hypothesized that the increase in ground temperatures at the Chamoli avalanche rupture site could have resulted in a reduction in the strength of the frozen rock mass by altering the hydrology of the rock and the mechanical properties of the discontinuities and of the broken rock mass.

“Multiple factors beyond those listed above contributed to the Chamoli rock and ice avalanche, including the geologic structure and steep topography, possible long-term thermal disturbances in the permafrost bedrock induced by atmospheric warming, stress changes due to the decline and collapse of adjacent and overlying areas. glaciers and increased infiltration of meltwater during warm periods, ”the study says.

Researchers say Chamoli’s event also raises “important questions about cleanliness

, climate change adaptation, disaster governance, conservation, environmental justice and sustainable development in the Himalayas and other high mountain environments ”and stresses the importance of a better understanding of the cause and of the impact of mountain hazards, leading to disasters.

DISASTER SCALE
The rock and ice avalanche was described as “a very large event with an extraordinarily high fall height which resulted in a disaster due to its extreme mobility and the presence of downstream infrastructure”.

The high loss of life and damage to infrastructure, however, was due to the “debris flow”, not the initial avalanche of rocks and ice, according to the document.

The drop of about 3,700 m to the Tapovan hydroelectric power station is clearly exceeded only by two events known in the historical record, namely the Huascaran avalanches of 1962 and 1970, while its mobility is not exceeded. than by a few recent glacial detachments, adds the study.

Almost all of the 204 people killed or missing in the disaster were workers at the Rishiganga (13.2 MW) and Tapovan (520 MW) project sites. Direct economic losses due to damage to the two hydropower structures alone are estimated to be over USD 223 million.


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