In the floods that battered Sikkim on October 4, over 53 people have died while almost 150 remain missing. The floods that were caused by the bursting of the South Lhonak Lake due to excess rainfall have reminded people of repeated warnings by experts and environmentalists.
According to a media briefing compiled by the Delhi-based Strategic Communications group Climate Trends, the impending disaster was talked about back in 2021 when a study was conducted about the increasing length of Lhonak glacial lake which was sensitive to extreme weather events such as cloudbursts.
Since it cannot be forecasted when Glacier-related floods, including floods from lake outbursts (GLOFs) would burst, the only option left was to be prepared with disaster planning and mitigation.
“It was already predicted in 2021 that this lake would breach and impact the dam. There has been a substantial increase in the number of glacial lakes as the glaciers are melting due to global warming. When the glaciers advance, they erode the river bed, leading to the deepening of the river. Also, climate change has resulted in erratic precipitation, including events like cloudbursts, as we saw in Sikkim, leading to the partial breach of the moraine dam,” Farooq Azam, Glaciologist, at the Indian Institute of Technology- Indore was quoted in the briefing.
Also Read: Sikkim Floods: Experts Attribute Glacial Outburst To Climate Change
“When glaciers are eroding, they put pressure on the bedrock, producing more silt. Whenever there is flash flooding, you would witness more silt and debris flowing downhill, aggravating the destruction caused by floods and landslides,” he added.
The Climate Trends briefing mentioned that the south Lhonak glacier is one of the fastest retreating glaciers, and the associated proglacial lake has become the largest and fastest-growing in the state. The glacier receded almost two kilometres in 46 years from 1962 to 2008. It further retreated by almost 400 m from 2008 to 2019.
“There has been a growing concern now about the hazard potential of this lake, as the downstream valley is heavily populated with numerous settlements and infrastructure,” it added.
Glacial Lake Outburst Floods (GLOFs)
A glacial lake outburst flood (GLOF) is a release of meltwater from a moraine-dam [moraine is consolidated debris in a dam] or ice-dam glacial lake due to dam failure. They cause disastrous floods downstream and create a huge loss of lives and property. There are three chief features of GLOFs which are mentioned below:
- There is a sudden release of water
- They are generally rapid events, lasting hours to days
- They cause large downstream river discharges
GLOFs can be triggered by extreme meteorological conditions, especially heavy rainfall events that cause degradation of the dams and lead to overfilling of the lake.
According to a report published by Intergovernmental Panel on Climate Change [IPCC], there are also chances that the number and area of glacier lakes will continue to increase in most regions in the coming decades and new lakes will develop closer to steep.
Some researchers and scientists have suggested the need for focussed scientific research mechanisms that include high resolution monitoring networks to identify the hotspot.
“We all know that in the warming world, the potential of cloudbursts, extreme rains, GLOF has gone up. Moreover, we do not have high-resolution monitoring systems that could tell us what happened, how it happened, and to what extent climate change aggravated the scenario. We know the Himalayan region is prone to cloudbursts, but we cannot identify the hotspot. Thus, a proper monitoring network is the need of the hour,” Roxy Mathew Koll, Climate Scientist at the Kochi-based Indian Institute of Tropical Meteorology, was quoted.
