On Wednesday, 4 October, a cloudburst over South Lhonak Lake resulted in a flash flood in the Teesta River, killing at least 14 people – with 102 others missing – and causing massive destruction in North Sikkim.
The swollen river submerged Teesta basin towns like Dikchu, Singtam, and Rangpo – and the flooding was made worse by the release of water from the Chungthang dam.
The Teesta-V and Teesta-VI hydropower stations, owned by the National Hydroelectric Power Corporation (NHPC), were also impacted by the flash floods and had to be shut down.
Being a part of the Eastern Himalayas and having a terrain marked by geological formations such as Kanchenjunga and Darjeeling gneiss, Sikkim's topography is vital to look at in the event of such calamities.
A vehicle is seen partially submerged in water after flash floods.
(Photo: PTI)
The main drainage systems in the area are the Teesta, Rangpo Chhu, and Dik Chhu rivers. Numerous glacial lakes may be found in Sikkim's high-altitude glacierised regions, including South Lhonak Lake, at an elevation of 5,200 meters.
Due to glacial retreat and an increased risk of glacial lake outburst floods (GLOFs), previous studies have cautioned that South Lhonak Lake may bust one day, threatening downstream settlements.
Unravelling the Potential Triggers Behind Sikkim's Devastating Floods
Critical questions concerning the circumstances that caused this calamity have been raised in the wake of the recent flash floods that wreaked havoc in Sikkim.
Though detailed scientific information will reveal the actual cause of the flood, prima facie, it looks like the tragedy may have been caused by a deadly confluence of excessive rainfall and a GLOF occurrence at South Lhonak Lake in North Sikkim. According to media reports, the National Disaster Management Authority (NDMA) has claimed so.
GLOFs are a perilous type of natural occurrence that frequently takes place in high mountain areas, most notably, the Himalayas. The sudden release of water from glacial lakes – which normally emerge as glaciers melt due to rising temperatures – causes these catastrophic disasters.
Even if scientists are actively examining the actual cause, the persistent snowfall in the upper parts and the rain in the lower regions caused serious difficulties for deployment and relief efforts.
Due to its enormous network of glacial lakes, Sikkim, situated within the Himalayan Ranges, is especially vulnerable to such disasters. According to the NDMA, about 10 percent of the 7,500 such lakes – estimated through remote sensing – are found in Sikkim, with about 25 designated as 'at-risk'. The risk is further increased because this area is known for local heavy rainfall events.
It is also being investigated whether the recent earthquake in Nepal was the cause of the South Lhonak Lake eruption.
The lake's vulnerability is shown by the fact that it went from covering 168 hectares to only 60 hectares – a large release of water volume that a simple cloudburst cannot explain.
The Looming Peril of GLOFs in the Himalayas
The population in the Himalayas is under significant danger from GLOFs because of their potential for destruction and extensive effects. The rapid retreat of glaciers, unstable moraine dams that hold back glacial lakes, and temperature changes that cause pressure differences within these natural reservoirs are some causes of GLOFs.
Devastating floods are brought on by the abrupt release of massive amounts of water, rocks, and debris downstream when a GLOF occurs.
The Himalayan region accentuates the severity of GLOFs due to its high population density, insufficient disaster infrastructure, and susceptibility to economic and environmental implications.
To protect lives and livelihoods in this sensitive area, addressing this hazard requires a comprehensive strategy that includes monitoring, early warning systems, infrastructure development, and climate change mitigation. It is essential for efficient disaster management in the Himalayas to understand the continuous dangers of GLOFs.
A jeep stuck in muddy waters in Singtam.
(Photo: Accessed by The Quint)
When a GLOF event occurs, it unleashes an enormous release of water, boulders, and debris, which is sudden, overwhelming, and leads to catastrophic floods. Due to several important variables, the Himalayan region is particularly vulnerable to the destructive effects of GLOFs.
First, millions of people live in the valleys and along riverbanks, giving the region a high population density. This makes them extremely sensitive to GLOFs, which can cause terrible loss of life and property.
Second, the Himalayas frequently struggle with poor infrastructure for disaster preparedness and response, which makes it more difficult to lessen the effects of GLOFs and quickly help affected communities.
Thirdly, the economic effects are severe since GLOFs have the potential to ruin crops, interfere with crucial transportation systems, and harm key infrastructure, causing enormous financial losses for local communities and entire countries. Furthermore, because these floods transport glacial silt, trash, and pollutants downstream, they hurt ecosystems and water quality.
Mitigating the Threat of GLOFs in the Himalayas
Policymakers must implement several measures to reduce the harmful effects of GLOFs to address this crucial issue.
The first step is to create and implement comprehensive GLOF monitoring and early warning systems that use cutting-edge tools like satellite images and remote sensing. These devices can monitor the health of glacial lakes and send timely alerts to people downstream so that they can be ready and leave as necessary.
Second, it is essential to prioritise sustainable glacier conservation and climate change mitigation measures to reduce glacier melt, a major cause of GLOFs. In this sense, programmes like afforestation and developing renewable energy sources are crucial.
Third, the construction of environmentally benign infrastructure and measures for disaster readiness should also be implemented, including reinforced riverbanks, flood-resistant structures, evacuation routes, and public awareness programmes.
We can collectively fight to lessen the danger and effects of GLOFs in the Himalayas by putting these policy measures into place, protecting the lives and livelihoods of those who live in this high-risk area.
The current situation in the Himalayan region highlights the urgent need for proactive disaster management and mitigation techniques. The devastating effects that climate change and glacial melting can have on vulnerable communities are starkly illustrated by the floods in Sikkim.
To safeguard the lives and livelihoods of persons in this high-risk area, we must combine scientific knowledge with comprehensive policies and infrastructural development.
(Anjal Prakash is a Clinical Associate Professor (Research) at Bharti Institute of Public Policy, Indian School of Business (ISB). He teaches sustainability at ISB and contributes to IPCC reports. This is an opinion article and the views expressed above are the author’s own. The Quint neither endorses nor is responsible for them.)
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