Glacial Lake Outburst Flood in Uttarakhand | What is the reason behind the outburst

 Nearly one-third of Uttarakhand is at risk of devastating glacier floods.

Scientists claimed that there are more than 500 glacier lakes in Uttarakhand at risk of an outburst.

Thousands of people living close to the Alaknanda and Dhauliganga rivers had to be evacuated.

A recent flash flood in the Chamoli district flooded hundreds of people and wiped out newly constructed dams and bridges and two power projects in the Tapovan area of the district on Sunday, Feb 7.

While some reports say that the Nanda Devi glacier had broken off triggering an avalanche followed by a flood in the Alaknanda and Dhauli Ganga rivers, the exact cause of the calamity is yet to be ascertained.

On Monday, 8 February, a DRDO team of snow and avalanche experts from its newly-created Defence Geo-Informatics Research Establishment visited the site for assessment. The director of the Wadia Institute of Himalayan Geology, Kalachand Sain, said two teams of glaciologists will leave Dehradun on Monday morning.

As political leaders extended their consolations, several environmentalists and climate activists are trying to draw attention to India’s climate crisis that gets largely ignored in policy-making. They have blamed mindless developmental projects and human interventions for destroying the Himalayan ecology, that they say, triggered this calamity.

Himalayan glaciers occupy the highest altitudes in the world and hold the largest amount of ice cover outside the polar regions; there are 9,575 glaciers in the Indian Himalayas, spread over an area of 37,466 square km area, some of which form the perennial source of major rivers. They are highly sensitive to ongoing warming and have lost mass at an accelerating rate in recent decades.

Following the 2013 Uttarakhand floods, several reports had warned that the fragile Himalayan region could face more disasters. In 2014, the report of an expert committee, formed on Supreme Court’s order and led by environmentalist Ravi Chopra, had held that the construction of so many dams had worsened the impact of the 2013 floods and recommended dropping of 23 hydropower projects. But repeated warnings have been ignored.

What are GLOFs and how vulnerable are

 the Himalayas?

Glacial lake outburst floods (GLOFs) are related to global warming. As the temperatures in the Himalaya soar, the glaciers retreat during the summer, leaving behind water filled, moraine dammed, precarious lakes holding huge amounts of water in a very unstable geomorphology. GLOFs have been known to occur in different parts of the world. In 1941, an outburst flood destroyed the city of Huaraz in Peru killing 4,500 people. Outbursts from a glacier-dammed lake in the Swiss Alps in 1968 and 1970 triggered debris flow and caused heavy damage to the village of Saas Balen. In the Himalayan realms, with its greatest concentration of glaciers outside of the poles, such an event would assume catastrophic proportions with urban inroads in higher altitudes, ever-expanding infrastructure and poor to non-existent integrated water management systems as opined in a paper by P Mukhopadhyay, 2011, titled ‘GLOF- A Threat Present and Real: Indian Summary’. According to the IPCC, 2001 assessments, the rising global mean temperatures by 2100 from 1.4° to 5.8°C, depending on the climate model and greenhouse gases emission scenario, would mean that up to a quarter of the global mountain glacier mass can disappear by 2050 and up to half could be lost by 2100 (IPCC, 1996).

What triggered the event?

“Most mountain glaciers around the world were much larger in the past and have been melting and shrinking dramatically due to climate change and global warming,” said Sarah Das, an associate scientist at Woods Hole Oceanographic Institute. 

In the immediate aftermath of the floods, initial reports suggested that a “glacial

  lake outburst flood” was a possible cause of the event. Glacial lakes form behind natural dams created by debris collected at the front of glaciers and then left behind as glacier fronts retreat. As a Carbon Brief guest post from last year explained, thousands of such lakes around the world are expanding as glaciers melt in response to rising temperatures. If the natural dam breaks, glacial lakes can cause potentially Catastrophic Outburst floods.

What scientists are almost certain of is that the incident was not a result of any glacier ‘breaking off’. In fact, glaciers are not known to break in a manner that ice-sheets in the polar regions do. Some chunks of snow from near the tip of the glacier can indeed slide down, but they do not result in huge amounts of water like those seen in incidents like these.

Argha Banerjee, a glaciologist who works at the Indian Institute of Science Education and Research (IISER), Pune, said it was possible that a glacier lake was present in the area but not known to scientists.

“There are hundreds of such lakes all over the place. We know about many of them, but it is possible that there is one that we do not know about. After today’s event, I started looking at the satellite images, and I couldn’t find any glacial lake in that area. But maybe, if we look at higher resolution satellite images, we would find one,” Banerjee said, adding that there are also instances of lakes forming inside the glaciers, which cannot be detected in satellite images.

“But if there are indeed no glacial lakes in that area, then Sunday’s event would seem to be a bit of a surprise,” he said.

But there are other possibilities, as Banerjee suggested.

“It is possible that an avalanche or a landslide created an obstruction in the flow of the river or streams in the upper mountains, resulting in a makeshift dam-like situation. When the pressure of the flowing water became large, the dam probably gave away, leading to a sudden gush of water. These are just the possible scenarios. We would know the exact reason only after reaching the site. It might take a day or two,” Banerjee said.

What are the guidelines for rescue?

The rescue operation continued at Tapovan tunnel in Chamoli district on the eighth day following the glacier burst, informed the state government on Friday.

Earlier on Thursday the rescue operation was halted following the rise in the level of water in the Rishiganaga river.

Around 30 peoples are trapped inside the tunnel, As many as 36 bodies has been recovered from different areas hit by the glacier burst in chamoli district while 204 is still missing.

GLOF threats to the Indian Subcontinent

 

The Himalaya, ‘third pole’ of the earth, comprises one of the largest collections of glaciers – around 9600, with a total glacier cover of 33000 km which holds the largest reserves of water in the form of ice and snow outside the Polar Regions. The climatic change/variability in recent decades has made considerable impacts on the lifecycle of the glacier with at least 20 significant GLOF events recorded in the last seven decades. The GLOF event in Nepal during 1981 damaged the Friendship Bridge of the China–Nepal Highway, destroyed the Kosi power station in Nepal causing significant economic losses. In fact the GLOFs at Dig Tsho in 1985 (Nepal) and Luggye Tso in 1994 (Bhutan) are considered ‘textbook’ case studies of such events globally. During August 2000, in the Tibetan Plateau, the GLOF occurred and destroyed more than 10,000 houses and 98 bridges – with financial losses of around Rs. 75 crore. In 2008, GLOF from Gulkin glacier, Karakoram Himalayas damaged a large number of properties.

Is India prepared to face such situation(s)?

 While some work on identification of such lakes has been done by CWC, other aspects are still a work in progress: a robust early warning system, and a broad framework for infrastructure development, construction and excavation in vulnerable zones. Uttarakhand glacier burst: 36 bodies recovered, 204 missing; experts study cause The NDMA, in its guidelines said, "In contrast to other countries, there are no uniform codes for excavation, construction and grading codes in India. Restricting constructions and development in GLOF/LLOF prone areas is a very efficient means to reduce risks at no cost." Ghulam Nabi Azad retires as MP, hopes for Pandits' return to Kashmir. The guidelines say construction of any habitation should be prohibited in the high hazard zone. "Existing buildings are to be relocated to a safer nearby region and all the resources for the relocation have to be managed by Central/State governments. New infrastructures in the medium hazard zone have to be accompanied by specific protection measures."

Prediction and measures

In several high mountain ranges around the world, a grave uncertainty about the hazard potential of glacial lakes still exists, especially with respect to the effects of accelerating rates of glacier retreat as a consequence of atmospheric warming. Area-wise detection and modelling hazard potential is, therefore, a major challenge. There are several possible methods for mitigating and monitoring the impact of GLOF surges and for putting in place early warning systems. The most important mitigation measure for reducing GLOF risk is to reduce the volume of water in the lake in order to reduce the peak surge discharge. The GLOF prone area downstream need measures to protect infrastructure against the GLOF surge. Monitoring systems prior to, during, and after construction of infrastructure and settlements in such areas should be in place, which includes the signal transmission system, the glacial lake outburst flood sensing system, and the glacial lake outburst flood warning system.