Heavy snowfall for two days may have triggered an avalanche, which led to the Uttarakhand disaster

An avalanche triggered by heavy snowfall for two consecutive days in the upper reaches of Chamoli district – and not the snapping of a glacier as thought earlier - was the likely cause behind the devastating flash flood in Uttarakhand, Indian scientists have found after analysing satellite images of the area.

At a review meeting in Dehradun on Monday, scientists from the Indian Institute of Remote Sensing presented images showing heavy snowfall on the catchment area of Rishi Ganga on February 5-6, which disappeared after the event.

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"This accumulated snow may have fallen down the slope after attaining a critical mass, triggering the disaster. It is not a case of a part of any glacier being broken down,” Santosh Rai, a senior glaciologist at the Wadia Institute for Himalayan Geology, Dehradun told DH.

The institute has dispatched a team of researchers to Joshimath to look for the signature of such an event on the ground. They would explore the areas near NTPC’s Tapovan power plant and may even trek upwards in the mountain to check if there is back up evidence.

After a meeting with the scientists Uttarakhand Chief Minister Trivendra Singh Rawat also said that the disaster took place due to lakhs of metric tonnes of snow sliding down abruptly from a trigger point on top of a naked hill.

Rai said such a course of action was entirely “plausible” because after a heavy snowfall if a small portion of it melts, the water acts as a “lubricant” for the entire mass of ice to flow downward.

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As the avalanche goes down it acquires high velocity and generate a lot of friction energy that melts the snow.

But the chain of events would leave its imprints on the ground such as crashed trees, which the WIHG team would try to find out.

Besides the two institutes, representatives from the Uttarakhand State Disaster Management Authority, Central Water Commission and ITBP attended the review.

However, neither the five IMD stations at Chamoli districts recorded heavy snowfall nor the DRDO issued an avalanche warning. The MeT officials said that the stations recorded “light to moderate” rainfall whereas DRDO didn’t issue any avalanche warning.

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“IMD observatories are over towns and cities. Only satellites can measure snowfall over hilly regions and over glaciers. Let us wait for the ground inspection reports for conclusions,” said M Rajeevan, Secretary, Ministry of Earth Sciences.