What caused the flood in Sikkim?

Source: This post has been created based on the article “What caused the flood in Sikkim?” published in The Hindu on 9^th October 2023.

UPSC Syllabus Topic: GS Paper 3 Environment — Environmental pollution and degradation; Disaster and disaster management.

News: This article discusses the causes and consequences of the recent Sikkim Glacier Lake Outburst Flood (GLOF) and provides suggestions to mitigate such disasters in the fragile ecology of the Himalayas.

The recent flood in Sikkim as a result of a glacier-lake outburst left more than 25 people dead and many more are still missing.

The voluminous outflow destroyed the Chungthang dam, which is critical to the Teesta 3 hydropower project, and rendered several hydropower projects along the river dysfunctional.

What is a Glacier Lake Outburst Flood (GLOF)?

GLOFs are instances of large lakes formed from the melting of glaciers, suddenly breaking free of their moraines — natural dams that are formed from rock, sediment and other debris.

There are an estimated 7,500 glaciers in the Himalayas and GLOFs have been associated with major disasters through the years. Previous instances of GLOFs include the 1926 Jammu and Kashmir deluge, the 1981 Kinnaur valley floods in Himachal Pradesh and the 2013 Kedarnath outburst in Uttarakhand.

Among the Himalayan States in India, Sikkim has the highest number of glaciers. Climatologists have warned that they could be responsible for GLOFs.

What triggered the Sikkim GLOF event?

There is uncertainty regarding the immediate causes behind the GLOF event.

According to the National Disaster Management Agency, the primary reason for the sudden surge appears to be a likely combination of excess rainfall and a GLOF event.

A huge ice-capped feature is near the lake’s north. There is speculation that heavy rainfall might have tipped the moraine to collapse and triggered the flood.

There is also a suggestion that a series of earthquakes in Nepal on October 3 might have played a role.

However, the inaccessibility of the terrain and the limitations of satellite imagery make it difficult to ascertain the causes with surety.

What was the resulting damage?

The major consequence of the flooding was the destruction of the Chungthang dam.

All bridges downstream to the Teesta-V hydropower station were submerged or washed out, disrupting communication. All connecting roads to the project sites as well as parts of the residential colony have been severely damaged.

Heavy siltation due to the floodwaters kept hydropower projects in downstream West Bengal shut.

The flood also destroyed bridges, water pipelines, sewage lines and houses.

Are such events likely in the future?

Several studies have warned of both the frequency and severity of GLOF events in the Himalayas increasing exponentially in the future.

This is more so because the Himalayan ecosystem is the most fragile in the world and any disruption in managing these resources will have a problematic outcome.

The fragility of the Himalayan ecosystem is also being disturbed through hydropower and other dams.

Rising temperatures are leading to a wetter future and contributing to climate change-led extreme events. GLOF is an outcome of warming of the region.

What should be done?

Greater care in planning and executing dam and other infrastructure projects is required due to the risk of GLOF-like events.

GLOF events can be anticipated as we can monitor changes in the size of lakes. Hence, “Early Warning Systems” (EWS) are implementable.

This would require a coordinated approach such as multiple agencies promptly sharing satellite images (that are trained towards the Himalayas) and a network of sensors to provide adequate warning.