Landslip likely triggered Flash Flood: experts

What is the News?

According to glaciologists and experts, the cause of flash floods in Uttarakhand Chamoli district was most probably a landslip(Landslide) and not a glacial lake burst.

Why are experts calling it a Landslide and not a glacial lake burst?

• The glacial lake outburst flood(GLOF) occurs when a natural lake, formed from a glacial ice melt and the glacial lake is breached. However, available satellite images do not show the presence of a glacial lake before the flooding event.
• Moreover, the Central Water Commission(CWC) monitors and prepares monthly reports on the state of glacial lakes and waterbodies measuring 10 hectares and above via satellite. Nothing out of the ordinary was observed by CWC.

Then, what might have caused the flooding?

• There was a hanging glacier and on top of the glacier was a huge rock mass.
• The rock mass became loosened due to freezing, thawing, and temperature variation. It came crashing down, creating pressure on the hanging part of the glacier. The fresh snowfall had also been added to the weight over the hanging glacier.
• This hanging glacier broke off due to gravitational pull, slid down with the entire rock mass. It slowed down near the base of the valley, where the Raunthi Gadhera stream flows.
• As the huge mass slowed a bit, then stopped, it blocked the water of the stream and the water quantum kept increasing. This damming up of the stream increased to such an extent that it breached the whole accumulated mass of water.
• Hence, this whole mass of water, boulders, and rock mass came crashing down with force towards the Rishi Ganga dam site. It caused massive damage to the under-construction Tapovan hydel project and caused floods.

Source: The Hindu

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