Context

• The recent glacial lake outburst flood (GLOF) in Sikkim wreaked havoc along the Teesta river, bringing into focus the magnifying risk of climate change-induced GLOF across the Indian Himalayan Region(IHR). 
• The article discusses the causes and impacts of glacial lake outburst flood along with the challenges and need to evolve a system to mitigate risks and provide early warnings.

What are Glacial Lake Outburst Floods?

• A GLOF is created when large amounts of water dammed by a glacier or a moraine is released suddenly. 
• Some of the glacial lakes are unstable and particularly moraine dammed lakes are potentially susceptible to sudden discharge of large volumes of water and debris which causes floods downstream i.e. GLOF.
• Eg: ​​In 2013 Kedarnath calamity, the glacier break caused large-scale devastation in the upper reaches of the ecologically fragile Himalaya

How does a GLOF happen/Causes?

• Heavy rainfall triggers a landslide, which may in turn cause a glacial lake outburst and more landslides downstream, and create conditions for flash floods as in case of Kedarnath Calamity 2013.
• In case of the recent Sikkim Calamity, while the exact combination of causes of the event is yet to be ascertained, monitoring equipment had reported higher-than-normal temperatures of zero to 5°C in the four days that data was received — exceptionally warm for Himalayan glaciers. 
• The key trigger in the process chain of the disaster was the collapse of a huge mass of rock/moraine from the north-western bank of the South Lhonak glacial lake. 
  • Assessed to be more than a quarter million cubic meters in volume, it displaced a significant volume of melt water, widening the river mouth at the eastern end, resulting in flash floods. 

Risks in IHR

• The Himalayan Region is susceptible to a range of hydro-meteorological, tectonic, climate and human-induced mountain hazards.
• Risks from glacial melting, slope shifting, landslides, intense precipitation, and heatwaves, among other hydro-meteorological and geo-physical hazards, are rising. 

Risks associated with GLOF

• Downstream hill communities and authorities stand to suffer serious damage to life, property, and livelihood as they get a very short lead time to respond.
• GLOF events bring permanent changes in morphology, topography and stream hydrology. 
• People downstream are mostly unaware of the risks posed by sudden glacier-melt and cascading hazards. 

Vulnerability to GLOF

• National Remote Sensing Centre’s (NRSC) Glacial Lake Atlas of 2023 reveals that three major river basins, of the Indus, Ganga, and Brahmaputra, are host to 28,000 glacial lakes greater than 0.25 hectares in area, in five countries. 
• Of these, 27% are in India, in six States and Union Territories. This region has witnessed catastrophic GLOF events in the past few decades. 
• A study published in Nature this year indicates that 90 million people across 30 countries live in 1,089 basins containing glacial lakes. 

Measures to mitigate GLOF

• Many geo-technical solutions for mitigation of GLOFs have been tried globally, including excavating channels for regulated discharge, drainage using pipes and pumps, spillway construction, and setting up small catchment dams to cut the speed of outflow. 
• NRSC’s atlases have provided high-resolution data via remote sensing, which allows for monitoring spatial change. 
• The Central Water Commission is conducting hydro-dynamic assessments of high-risk lakes, mapping water flow, height and routing simulations using digital elevation models. 
• The NDMA’s national guidelines (2020) provide States with a technical overview of the hazard and risk-zonation and suggest strategies for monitoring, risk-reduction and mitigation. 

Issues associated with GLOF management

• Predicting the chain of events in GOLF is difficult. 
• The multitude of glaciers and temporal variations in glacial recession makes monitoring and estimation of the risk more difficult. 
• Conditions above 5,000 meters above mean sea level create formidable challenges such as inaccessibility, impossibilities in transporting and retaining excavation equipment, strong winds, difficulties in sourcing power and connectivity, and vandalism.
• The measures suggested for mitigation by the government are difficult to implement and are labor-intensive. 

What needs to be done?

• Institutional awareness of these risks is increasing, but the challenge is to evolve a system to mitigate risks from such hazards, and provide early warnings.
• While meeting the development needs of hill communities, disaster and climate resilience principles need to be assimilated into government policy and practice as well as private investment. 
• All governments and scientific institutions need to come together to integrate resources and capacities in disaster risk reduction to create a comprehensive GLOF risk mitigation plan that includes installation of monitoring and end-to-end early warning systems at high-risk glacial lakes. 

• While appropriate synergies have been created, increased focus on prevention and mitigation will reduce loss and damage and bring stability into the lives of hill communities.

https://www.thehindu.com/opinion/op-ed/mitigating-tragedies-in-the-himalayan-region/article67453790.ece