Dehradun: While many research teams have been deployed in Uttarakhand to carry out their investigation into the cause of Sunday’s flash flood that played havoc in the region, affecting millions of lives and destructing whatever came in its way.
Initially, the cause of the tragedy was considered to be a breach in a temporary pool or lake formed by obstructions due to landslides or snow avalanches, an event described as a Landslide Lake Outburst Flood (LLOF). However, the satellite images circulated among scientists tracking the incident, show that a large chunk of fresh snow from a mountain near Raini village in Chamoli district had dropped off on February 7, which probably set off the flash flood. The avalanche triggered by this could have released 3-4 million cubic metres of water in the rivers.
“Our preliminary investigation through satellite imaging has pointed to the possibility of the flood having been caused by the melting of snow, and not a glacial lake outburst. Of course, we need to investigate this further. We have sent two teams of scientists to the site and will have more accurate information when the investigation has been completed,” said Santosh Rai, head of the Glaciology and Hydrology division at the Dehradun-based Wadia Institute of Himalayan Geology.
“So far, the satellite pictures have revealed that there was no snow on February 2 in the valley, but very heavy snowfall was witnessed on February 5 and 6. This fresh snow started melting on February 7, which led to the slumping of the snow bank, and a subsequent avalanche. As the snow bank travelled down the valley, it gained momentum and kinetic energy, thus increasing the amount of water and soil on the way,” he added.
Furthermore, a member of the investigating team, also revealed that new evidence had indeed made Sunday’s incident look like a result of a landslide or snow avalanche. “The possibility of this being a LLOF event does seem more likely after the emergence of the satellite images. A landslide or snow avalanche can create obstructions in the normal path of a flowing river or stream, which results in the formation of a temporary pool, or a dam-like situation. When this obstruction finally gives way to the force of accumulating water, it creates a situation similar to a lake burst. In the case of an avalanche, snow adds to the volume of water,” the team member said on the condition of anonymity.
Before the emergence of the satellite images, the Uttarakhand disaster was believed to have been a natural calamity caused by a ‘Glacial Lake Outburst Flood’, or a breach in a proglacial lake that forms at the tip of a glacier that is retreating due to rising temperatures. What made scientists doubt that theory was the fact that they did not know of the existence of any such lake in that area.
“What is being discussed right now are still just possibilities. We haven’t even begun our work and we are still quite a distance away from the actual place,” the team member said.
Meanwhile, Anil Kulkarni of the Divecha Centre for Climate Change at the Indian Institute of Science in Bengaluru said in his preliminary analysis that the flash flood could have been caused by the release of water trapped in a lake under the north Nanda Devi glacier. Kulkarni informed that this underground lake had the capacity to store 4.5 million cubic metres of water.
“If this depression filled with water develops appropriate hydrostatic pressure, it can accelerate the lower part of the ablation zone (near the tip of the glacier where the snowmelt happens), possibly releasing water from the underground lake. It could be the potential reason for the flash flood,” Kulkarni had said.