Heavy rain, soaring temp could have led to collapse of rock mass in U'khand

Maximum temp rising at the rate of

0.032 degrees C per year in Chamoli

Jan 2021 was the warmest month in six decades

58 mm of cumulative precipitation between Feb 3 and 5

Casualties

72 bodies recovered

41 identified

132 still missing

New Delhi, March 6

Heavy precipitation in the Chamoli region from February 4-6 and an overall rise in temperature in Uttarakhand in the past four decades could have led to the rock collapse that triggered the deadly flashfloods in the state last month, according to a study by the International Centre for Integrated Mountain Development.

Kathmandu-based ICIMOD’s report found that a crack had formed prior to the incident at the site, where the rock detachment led to a rockslide from the Raunti peak.

The rockslide brought along with it mounds of earth and snow which could have triggered the flashfloods. With a straight slide line of 1.6 km (5,500 to 3,900 masl), the kinetic energy during the fall generated enough heat to melt the ice. As the debris moved downstream in the Rishi Ganga, it pushed running riverwater ahead of it, including water from small structures along the river path.

So far, 72 bodies and 30 body parts have been recovered from different places in the avalanche-hit areas, out of which 41 bodies have been identified.

As many as 132 persons are still missing.

The ICIMOD is a regional organisation that works on different aspects in the Himalayan-Hindukush region. It has eight members — India, China, Pakistan, Afghanistan, Myanmar, Bangladesh, Bhutan and Nepal. At the same headwall of the Raunthi peak, an avalanche deposited ice and more bedrock in the valley below between September 19 and October 9, 2016.

“The resulting destabilisation of the rock due to the lack of ice cover (glacial debuttressing, stress-release fracturing), increased exposure to solar radiation, a freeze thaw cycle in combination with a large snowfall event preceding the event of February 7, 2021, and rapid melt water production may have favoured the fracturing of rock,” the report states.

“This can, however, not explain the depth of the fracture (150 m), which must have evolved over a longer period of time,” the report states. The ICIMOD report further states that a strong western disturbance passed across Kashmir and northwest India from February 4-6. It was fully charged with convective instability that may have contributed to the heavy precipitation. The Uttarakhand tragedy occurred on February 7.

“Numerical simulation of some of the attributes have been carried out which depict strong evidence of heavy precipitation contributing to high flows downstream,” it said. The numerical simulation on February 4 shows heavy precipitation over the region. The western disturbance travelled with relatively slower speed and its stagnancy produced concentrated precipitation, the report states.

“Precipitation data derived from Global Precipitation Measurement (GPM) Mission suggests that there were continuous precipitation events from February 3-5, which resulted in approximately 58 mm of cumulative precipitation. Most of the precipitation in the high altitude areas of Chamoli would have occurred as snowfall,” it states. — PTI