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The recent flash flood in Dharali village in Uttarkashi, Uttarakhand, suspected to be triggered by the breaking of a glacial lake coupled with heavy rainfall, underscores the escalating threat posed by Glacial Lake Outburst Floods (GLOFs) in the Himalayan region. This event, where over 60 people remain missing, highlights the urgent need for comprehensive strategies to mitigate the risks associated with these phenomena. Glaciologist Anil V Kulkarni's observation of past lake formations in the Kheer Ganga river's origin area, even in non-winter months, strongly suggests the potential for newly formed lakes to breach due to glacier movements. The National Disaster Management Authority (NDMA) is also considering the possibility of a glacial snout detachment contributing to the disaster, further emphasizing the complex and unpredictable nature of these events. The fact that rescue operations have been ongoing for four days underscores the scale of the challenge and the necessity for robust preparedness measures.
The NDMA's 2020 guidelines on managing GLOF-related disasters offer a crucial framework for addressing this challenge. GLOFs, resulting from the sudden release of large water masses dammed by glaciers or moraines, are becoming increasingly prevalent due to climate change-induced glacier retreat in the Hindu Kush Himalayas. The inherent weakness of moraine dams, composed of ice, sand, pebbles, and ice residue, makes them susceptible to abrupt failures, unleashing millions of cubic meters of water downstream with devastating force. Documented peak flows reaching 15,000 cubic meters per second during such events illustrate the immense destructive potential. The Himalayan glaciers' retreating phase, coupled with the growing size and number of glacial lakes, amplifies the risk to downstream infrastructure and human life. The National Remote Sensing Centre's (NRSC) inventory of glacial lakes, identifying 352, 283, and 1,393 such bodies in the Indus, Ganga, and Brahmaputra river basins, respectively, reinforces the scale of the problem.
The NDMA guidelines rightly emphasize that effective risk reduction begins with identifying and mapping potentially dangerous glacial lakes, implementing structural measures to prevent breaches, and establishing mechanisms for saving lives and property during a GLOF event. The identification process should consider various factors, including the condition of lakes, dams, associated glaciers, topographic features, and past events, based on field observations, geomorphological and geotechnical characteristics, and other physical conditions. The NDMA's recommendation to utilize Synthetic Aperture Radar (SAR) imagery for detecting changes in water bodies, including the formation of new lakes, during the monsoon season is a valuable tool. Further development of all-year remote monitoring protocols from space can serve as a crucial complement and precursor to ground-based early warning systems at critical lakes, enabling more proactive and timely interventions.
Structurally, managing GLOF risks involves reducing the volume of water in the lake, which can be achieved through various methods such as controlled breaching, constructing outlet-control structures, pumping or siphoning water, and creating tunnels through moraine barriers or under ice dams. The successful intervention following a landslide on the Phuktal river in Ladakh in 2014, where the NDMA and the Indian Army cleared debris and channeled water using controlled blasting and manual excavation, demonstrates the effectiveness of these structural measures. However, India's preparedness in handling GLOF situations remains a concern. While the Central Water Commission (CWC) has made progress in identifying glacial lakes, the development of a robust early warning system (EWS) and a comprehensive framework for infrastructure development, construction, and excavation in vulnerable zones is still ongoing.
A critical gap highlighted by the NDMA guidelines is the absence of uniform codes for excavation, construction, and grading in India, unlike other countries. Restricting construction and development in GLOF/LLOF-prone areas is a cost-effective means of risk reduction. The guidelines clearly state that no habitation should be permitted in high-hazard zones, and existing buildings should be relocated to safer regions, with the Central and State governments managing the relocation process. New infrastructure in medium-hazard zones must be accompanied by specific protection measures. Emphasizing land use planning that avoids hazards and minimizes risks is crucial for reducing losses caused by landslides.
The NDMA rightly points out the lack of widely accepted procedures or regulations for land use planning in GLOF/LLOF-prone areas in India. The development of such regulations is essential, given the increased risk of future GLOF/LLOF events. Monitoring systems should be in place before, during, and after the construction of infrastructure and settlements in downstream areas to ensure safety and minimize potential damage. The implementation of effective Early Warning Systems (EWS) is paramount for disaster risk management.
Despite the crucial role of EWS, the number of implemented and operational GLOF EWS remains limited, even globally. In the Himalayan region, only three cases – two in Nepal and one in China – have reported sensor- and monitoring-based technical systems for GLOF early warning. It is important to note, however, that India does have a notable history of successful warnings related to Landslide Lake Outburst Floods (LLOFs). The 1894 Gohna landslide event in Uttarakhand demonstrates the effectiveness of early warning dissemination. Accurate prediction of the lake overflow, coupled with timely dissemination of the warning through a newly installed telephone line, prevented fatalities despite the devastating impact of the flood. This historical success story highlights the importance of investing in and developing similar early warning systems for GLOFs today.
Rescue operations in the event of a GLOF require a multi-faceted approach. In addition to deploying specialized forces such as the National Disaster Response Force (NDRF), Indo-Tibetan Border Police (ITBP), and the Indian Army, the NDMA emphasizes the crucial role of trained local manpower. Local communities often carry out the majority of search and rescue operations before the arrival of state machinery and specialized teams. Therefore, establishing trained and equipped local teams in GLOF and LLOF-prone areas is essential. These teams can assist in planning and setting up emergency shelters, distributing relief packages, identifying missing people, and addressing needs for food, healthcare, water supply, sanitation, and education. They can also identify vulnerable individuals who require special assistance after the disaster.
Furthermore, the NDMA calls for comprehensive alarm systems that enable rapid evacuation. Given the fast-moving nature of GLOFs, evacuation must be executed within a very short timeframe, requiring a robust alarm infrastructure, clear protocols for all actors involved, and well-informed and prepared populations and authorities. In addition to traditional acoustic alarms such as sirens, modern communication technologies, including cell phones, can be leveraged. Ensuring the availability of specialized heavy earthmoving and search and rescue equipment is also vital for clearing debris and carrying out search and rescue operations. Motor launches, country boats, inflatable rubber boats, life jackets, lifebuoys, and similar equipment should also be readily accessible.
Acknowledging the potential inaccessibility of disaster sites for heavy machinery, the NDMA encourages the use of innovative methods utilizing locally available natural resources. The development of lighter machinery, designed for disassembly and transportation in mountainous regions, is crucial. This equipment can be transported by helicopter in disassembled form and assembled on-site. Temporary shelters for local populations should be built in elevated locations to provide resilience against landslides and floods. Finally, emergency medical response should be provided by Quick Reaction Medical Teams (QRMTs), mobile field hospitals, Accident Relief Medical Vans (ARMVs), and heli-ambulances in areas inaccessible by roads. Psychological counseling of victims and the dissemination of accurate information through press conferences and mass media are also essential components of disaster response.
Source: How to reduce risks from glacial lake bursts and carry out effective rescue operations