Topics Covered: Disaster and disaster management.
What is a glacier outburst flood and why does it occur?
Context:
Parts of Uttarakhand recently 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.
What is glacial lake outburst flood (GLOF)?
It is an outburst that happens when a dam containing a glacial lake fails.
GLOFs have three main features:
- 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).
Why does a glacier break?
- Erosion.
- A build-up of water pressure.
- An avalanche of snow or rocks.
- An earthquake under the ice.
- Massive displacement of water in a glacial lake when a large portion of an adjacent glacier collapses into it.
Impact:
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 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.
Sources: the Hindu.
