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

New Delhi, Feb 07: A part of the Nanda Devi glacier broke off in Uttarakhand's Chamoli district on Sunday, leading to massive floods, that led to the death of 10 people. The deluge also brought spotlight on the 2013 flash floods in the hill states that wiped out settlements and killed over 5,000 people.

At least 150 people have been reported missing and at least 10 have lost their lives so far.

What is a glacial lake outburst flood (GLOF)?

Glacier retreat is considered to be one of the most obvious manifestations of ongoing climate change in the majority of high-latitude regions throughout the world.

"Glacial lake outburst flood" (GLOF) is used to describe a sudden release of a significant amount of water retained in a glacial lake, irrespective of the cause.

GLOFs are characterised by extreme peak discharges, often several times in excess of the maximum discharges of hydrometeorologically induced floods, with an exceptional erosion/transport potential; therefore, they can turn into flow-type movements.

According to antarcticglaciers.org, 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?

A buildup of water pressure, an earthquake or cryoseism, an avalanche of rock or heavy snow, volcanic eruptions under the ice could be the reason for a glacier break.

The outburst can also happen after a massive displacement of water in a glacial lake when a large portion of an adjacent glacier collapses into it.

The direct causes of glacial outbursts linked to earthquake, heavy rainfall/snowmelt, long-term dam degradation, etc.

Is climate change responsible for glacier burst in Uttarakhand?

"It is an unfortunate incident. Our thoughts are with the missing construction workers and affected people of Uttarakhand. While exact cause of this incident is yet to be ascertained and needs an honest investigation, it is evident that increasing human interventions in ecologically sensitive Himalayan region are making it more vulnerable to climate change.

"Heavy construction work in the fragile eco-sensitive zones should be avoided," Avinash Chanchal, senior climate and energy campaigner, Greenpeace India said.

Another expert, Anjal Prakash, one of the lead authors of a special report on oceans and cryosphere of the Intergovernmental Panel on Climate Change (IPCC), said while it was too early to explain the cause of the devastation, prima facie it seemed to be due to climate change and global warming which has become "an alarming and irreversible situation now".

What happened in Uttarakhand in 2013?

A devastating natural disaster in the form of torrential rains of unseen magnitude had struck Kedarnath on 16-17 June in 2013.

The banks of the Chorabari lake in Kedarnath collapsed due to a cloudburst that had resulted in a major flash flood causing widespread destruction in Uttarakhand and led to heavy losses to infrastructure, agriculture lands, human and animal lives.

with PTI inputs