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Uttarakhand glacier burst: What is a glacier outburst flood and why does it occur?

Parts of Uttarakhand on Sunday witnessed massive flooding after a chunk of the Nanda Devi glacier broke off at Joshimath in Uttarakhand’s Chamoli district. Read on to know what is a glacier break and why does it occur.

UPDATED: February 8, 2021 10:20 IST

Parts of Uttarakhand on Sunday witnessed massive flooding after a chunk of the Nanda Devi glacier broke off at Joshimath in Uttarakhand’s Chamoli district. Bringing back haunting memories of the 2013 Kedarnath calamity, the glacier break caused large-scale devastation in the upper reaches of the ecologically fragile Himalaya.

As per the available information, over 150 labourers working at a power project in Tapovan-Reni are missing while rescue teams have recovered 10 bodies so far.

The power project was completely washed off and homes along the way were also swept away as the waters rushed down the mountainsides in a raging torrent.

Meanwhile, all 16 people who were trapped in a tunnel near Tapovan area have been safely rescued by Indo-Tibetan Border Police (ITBP) personnel.

What glacial lake outburst flood (GLOF)?

A glacial lake outburst is a type of outburst flood that takes place occurs when water dammed by a glacier or moraine is released. To simplify it, GLOF is an outburst that happens when a dam containing a glacial lake fails.

-They involve sudden (and sometimes cyclic) releases of water.
-They tend to be rapid events, lasting hours to days.
-They result in large downstream river discharges (which often increase by an order of magnitude).

What is Nanda Devi glacier?

The Nanda Devi glacier forms part of the second-highest mountain in India — the Nanda Devi mountain. While it the second-highest after Kangchenjunga, it is the highest mountain located entirely within the country as Kangchenjunga lies on the border of India and Nepal.

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On the northern side of the Nanda Devi lies the Uttari Nanda Devi Glacier which flows into the ‘Uttari Rishi Glacier’. To the southwest lies the Dakkhini Nanda Devi Glacier which flows into the Dakkhini Rishi Glacier. All of these glaciers drain west into the Rishiganga.

Why does a glacier break?

A glacier break or burst can occur for a number of reasons like erosion, a build-up of water pressure, an avalanche of snow or rocks, and also an earthquake under the ice.

A glacier burst can also be triggered by massive displacement of water in a glacial lake when a large portion of an adjacent glacier collapses into it.

Although glacier lakes can vary in volume, they are known to hold millions to hundreds of millions of cubic metres of water and a failure to contain ice or glacial sediment can result in water being released even for days.

What happened in Uttarakhand in 2013?

In June 2013, a multi-day cloudburst centred on Uttarakhand caused devastating floods and landslides.

According to the state government, more than 5,700 people were presumed dead in the disaster. A number of bridges and roads were destroyed and more than 3 lakh people were trapped in the valleys leading to the Char Dham pilgrimage sites.

 

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