Flood management |
Understanding the true dangers of GLOF
Millions of people are at risk of Glacial Lake Outburst Floods on a global scale
Right: State Disaster Rapid Force personnel searching for lost people in Srinagar, Uttarakhand, India. On 7 February 2021, more than 200 people were killed when a wall of rock and ice collapsed, forming a debris flow that barrelled down the river valley and destroyed two hydropower generating facilities. Initial suggestions had pointed to a glacial lake outburst flood. Such events are occurring more frequently due to climate change © gsrsirji /
Shutterstock.com
Below: Melting glacier in the Himalayas
MORE THAN 100 PEOPLE are reported to have been killed by a Glacial Lake Outburst Flood (GLOF) that occurred in India at the beginning of October, re- iterating calls for the installation of advanced early warning systems at such high-risk lakes. On 4 October 2023, the southern bank of the South Lhonak Lake was breached, washing away the 60m high Chaungthang Dam which is part of the 1.2GW Teesta-III, Sikkim’s largest hydropower project. Reports estimate that more than 88,000 people were affected by the incident and over 2000 houses were damaged. Glacial lakes are formed when meltwater accumulates and, as they increase in size, can become more dangerous due to mostly being dammed by unstable ice, sediment, loose rock and debris.
Previously the speed with which climate change was melting glaciers and thus filling these lakes was seen as the biggest problem, but such thinning and retreating glaciers are also impacting the surrounding geography. This can result in an increased risk of avalanche and rockfall, while the production of more rain than snow at high altitude and the thawing of permafrost, is also contributing to geological instability in mountainous regions such as the Himalayas. A GLOF is created when glacial lakes are breached but triggering this is described as a being a complex process. There is debate about whether Lhonak Lake was triggered by torrential rain, the failure of moraine or even an earthquake. Nonetheless reports suggest that previous warnings had been given about the possibility of flooding at the lake which has more than doubled in size over the past three decades due to the rapidly melting glacier which feeds it. Back in 2016 water was drawn from the lake to prevent it from overflowing and questions have been asked about why early warning systems hadn’t been installed if there were concerns about its stability. However, the first part of such a system (including a camera and weather instruments) were installed in September, officials reportedly told Reuters. Plans were underway to add a tripwire sensor that would be triggered if the lake was about to burst, giving downstream residents warnings for immediate evacuation. It could have also saved the hydropower dam by giving time to open the gates – when orders were received to open them, floodwater had already started inundating the structure on the Teesta River back in October.
India’s National Disaster Management Authority has 22 | December 2023 |
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