As authorities race to rescue people trapped in Uttarakhand, following a devastating landslide-induced flash flood on February 7, scientists have called for deciphering the possibility of glacier-related hazards and enhance the capabilities of monitoring and early warning in the high mountain areas.

Scientists in a review published on February 2, before the floods, stressed on improved in situ monitoring network for weather, hydrology and glacier change as a crucial requirement for predicting the future of this resource and associated hazards and their impact on regional water, energy and food security.

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 sq 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, in contrast with relatively stable Karakoram glaciers, said the review published by scientists from China, Nepal, the United Kingdom, Canada and Germany, recommending a balanced strategy for hydropower development with improved transboundary cooperation.

The frequency of glacial-lake outburst floods and run-off floods have increased recently and could increase further in coming decades, threatening existing and planned hydropower infrastructure downstream. A lower-emissions climate change pathway would reduce the rate of glacier loss, increasing the time available for adaptation. This pathway would have considerable socio-economic benefits, added the review.

Arun B Shrestha, Regional Programme Manager for River Basins and Cryosphere at the intergovernmental International Centre for Integrated Mountain Development, who was not involved in the review said that infrastructure planning should factor in the probability of Uttarakhand-like events. The probability of such events happening in the future increases with the ongoing rate of climate change and socio-economic changes, he said.

“Infrastructure such as hydropower and roads can impact the surrounding environment and also can be impacted by the surrounding environment,” said Shrestha. “So environmental sustainability should be an important part of the feasibility study of infrastructure projects.”

Agreeing with the review on in-situ measurements and monitoring, Shrestha elaborated that remote sensing-based study can provide a broad understanding of the status of a glacial lake in a large area. This can be used to identify potentially dangerous lakes.

“Field-based assessment should be conducted for those potentially dangerous lakes to have a detailed understanding of the hazard,” he told Mongabay-India. “The study should also include the area downstream of the lake to understand the risk. Glacial lake outburst flood modelling can provide scenarios of its impacts in the downstream. Yes, for all those studies we need to have robust methodology and capacity to conduct those studies.”

He added that apart from hazard assessment, it is also important to assess risk.

International Centre for Integrated Mountain Development is working on a complete Hindu Kush Himalayas glacial lake inventory. It has found 47 lakes potentially dangerous in the Hindu Kush Himalayas region. Among them, 25 glacial lakes are in China, 21 in Nepal, and one in India. They lie in basin upstream of Nepal and a glacial lake outburst flood from them could impact Nepal, added Shrestha.

Ravichandran, Director of National Centre for Polar and Ocean Research under the Ministry of Earth Sciences said the organisation has undertaken studies in the western Himalayas in Chandra basin in Himachal Pradesh since 2013. A total of six glaciers of this basin are monitored for mass, energy and hydrological balance.

“So far we know where the glaciers are and we are monitoring their surface area,” Ravichandran told Mongabay-India. “But next, we are planning to monitor the depth of the glaciers in the Chandra river basin and see how much water is available and how they are depleting. We are making intense observations on one location and then we will expand it to other locations in the Himalayas.”

“We have started networking with other institutes from last year,” he said. “We can monitor almost all the glaciers from satellite data, but we need in situ measurements to understand the process of depletion.”

“Himalayan topography is changing very fast, so it is challenging to model but in situ measurements will help us in understanding the physics so we can model better,” he said, adding that accessing remote areas is an additional challenge.

Scientists such as Dan Shugar analysed satellite images that indicated a potential landslide.

Cascading impacts

On February 7, telling camera shots panned on gushing floodwaters bringing down a torrent of mud and boulders in the Rishiganga and Dhauliganga rivers sweeping through Chamoli district of Uttarakhand in the Himalayas, destroying life and property and pummeling dams for the Rishiganga hydroelectric project and the Tapovan hydroelectric project.

A section of scientists has suggested and converged on a landslide as the likely trigger for the flash flood, ruling out the glacial lake outburst flood theory that was initially considered. A landslide triggered snow/ice avalanche in the upper catchment of the Rishiganga river and caused severe damage downstream, according to Indian Institute of Remote Sensing.

As scientists work round-the-clock to further demystify the event, the disaster also spotlights the expansion of hydropower development into high mountain areas such as the Himalayas.

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.

A 2016 study revealed that of the 177 hydropower projects located close to Himalayan glaciers, over a fifth (including many in India) could be under threat from floods caused by glacial lake outburst floods. Most of the sampled hydropower projects are in the Indian Himalayan states of Himachal Pradesh, Uttarakhand, and Sikkim and some in Nepal and Bhutan.

Wolfgang Schwanghart, author of the 2016 study observed that events such as the current Uttarakhand floods are composed of a cascade of events that can be “best compared to falling dominoes”.

“As researchers, we need to better understand these cascades and quantify their probability. However, this will be only possible to some degree, leaving decision-makers with much uncertainties about the risks of climate change and water resources,” said Schwanghart, at the University of Potsdam Institute of Environmental Science and Geography.

“Our [2016] study was mainly concerned with glacier lake outburst floods, a process that – to our best knowledge – was not responsible for the current catastrophe in Uttarakhand,” Schwanghart told Mongabay-India. “Yet, there is one important aspect that is also pertinent to the Uttarakhand floods: the expansion of hydropower development into high mountain areas. This development is particularly obvious in Uttarakhand where new projects have been built or are currently constructed in close vicinity to glaciers and steep and unstable terrain.”

While it is speculative at this stage to attributing such events (the 2021 flood) to climate change, Schwanghart stresses that it is known that global climate change has led to glacier mass loss since the 1970s and that high-altitude permafrost has been thawing, potentially destabilising high mountain slopes and peaks. Hence, while such events have always been happening in the past, it is very likely that they occur more often during climate warming, he said.

Analysing potential reasons

Uttarakhand has more than a thousand glaciers. A 2020 study found a 10% reduction in glacier area from 1980-2017 in the glaciers of the upper Rishiganga catchment nestled in the Nanda Devi mountains, India’s second-highest mountain.

As the events unfolded on February 7, in Chamoli in Uttarakhand, the site of the iconic Chipko environmental movement, world experts in landslides, glaciers and remote sensing, and citizen scientists pieced together satellite images before and after the event to decipher the sequence within 8 hours of the event. The likely sequence of events is documented in the American Geophysical Union Landslide blog by Dave Petley, vice-president (research and innovation) at the University of Sheffield.

Analysis by geomorphologist Dan Shugar of the University of Calgary and colleagues suggests that a “landslide took out part of a hanging glacier” that transitioned into flash floods along the Rishiganga and Dhauliganga rivers.

“Glaciers are changing rapidly, and so too are the hazards posed by glaciers and steep, glacially carved slopes. In other words, just because we mapped something 5-year, 10-year or 20-year-ago, does not mean those maps are accurate anymore,” Shugar said, adding that so many valleys in the Himalayas are glaciated and steep, and so we cannot avoid all risk from glacial lake outburst floods and landslides.

Building onto the understanding, the French space agency National Centre for Space Studies activated the International Charter “Space and Major Disasters” to image the area of the disaster in Uttarakhand.

The Charter is a global collaboration through which satellite data are made available for the benefit of disaster management. Images from Pléiades (an optical satellite constellation) show a clear rupture line of 550 m on the north face of Ronti peak, what is believed to be the origin of the event.

Saurabh Vijay, Assistant Professor, Geomatics Group, Civil Engineering Department, IIT Roorkee emphasised that there is a need to regularly monitor hanging glaciers located in the valleys like Rishiganga and assess their potential to bring such catastrophic events. “Hanging glaciers are not very typical valley glaciers that we see in the Himalayas,” he said. “They are very steep, while most Himalayan glaciers are gentle in nature.”

Vijay said a similar event occurred on the neighbouring glacier during September 2016-October 2016, but its severity is not well known.

“It is still unknown how a large amount of water for a short time-period came into the picture (in the 2021 event), which collapsed the infrastructure,” he said. “One potential reason is that the avalanche material deposited in the valley and trapped the ongoing water stream (sort of temporary lake) before it burst. We do not have any evidence of such a temporary lake using satellite images, but this will be further investigated by the glaciologists, who are already in the valley. The speculations related to any hidden subsurface lake or water trapped in the old sediments in the valley can also be verified during the field visit.”

A team led by professor Anil Kulkarni from IISc Bengaluru identified a subglacial lake as the potential for the water source using a remote sensing tool. “Our assessment suggests the event might have started with a massive ice avalanche, as suggested by AGU blog,” claimed Kulkarni in a statement. “It might have led to snow avalanche/landslide downstream and release of 1.6 million cubic metre water stored in the subglacial lakes in the Raunthi glacier. It can also explain the rapid melting of snow and ice accumulated by the series of the avalanches.” He associated the event with climate change.

A landslide triggered snow/ice avalanche in the upper catchment of the Rishiganga river and caused severe damage downstream, according to Indian Institute of Remote System. Photo credit: Hridayesh Joshi

A lot of unknowns

Chandan Mahanta of Indian Institutes of Technology, Guwahati’s Civil Engineering Department advised extreme caution on planning hydro projects in the eastern Himalayan region, especially where the distance between glaciers and planned dams is less. The nature and number of glaciers in the eastern Himalayas are different than the western counterparts. Typically, the glaciers in the eastern Himalayan region are in four sub-regions; Sikkim, Bhutan, West Arunachal and East Arunachal.

“There are several small glaciers not properly mapped, and are less than 5 sq km in area and possibly they are more susceptible to climate change-related fluctuation, especially in Dibang valley in eastern Arunachal where numbers of small glaciers and glacial lakes are quite large,” Mahanta explained. “With the continuous glacial melting such glacial lakes pose danger to turn into glacial lake outburst flood events and any downstream reservoir adds to the risk and vulnerability.”

He reiterated the need of the hour is to prepare the baseline data to understand the hydrology, geology and climate change response of these glaciers. “Most of these glaciers in the eastern Himalayas share the administrative boundaries of China, India and Bhutan but they all come under the same hydrological boundary,” Mahanta added in a statement. “It becomes extremely important and challenging to work collaboratively on these glaciers. Currently, there are a lot of unknowns to successfully predict and quantify future catastrophic events.”

This is reinforced in the review that underscores that although remote sensing is now yielding valuable insights into these remote mountain catchments, there are substantial knowledge gaps in the cryosphere of the Himalayas and Karakoram.

According to the Ministry of Science and Technology, eastern Himalayan glaciers “have tended to shrink faster than glaciers in the central and western Himalaya” based on a compilation of area change studies. The mass balance studies conducted for some Himalayan glaciers revealed that the majority of Himalayan glaciers are receding at varying rates because of many reasons including climate change, according to the ministry. The total amount spent on research on Indian Himalayan glaciers from 2016 to 2019 is about Rs 14.90 crore.

This article first appeared on Mongabay.