GLOF: The Threat of Glacial Lake Outburst Floods in Sikkim

What is GLOF?

GLOF, or Glacial Lake Outburst Flood, is a significant natural phenomenon characterized by the sudden failure of a dam that contains a glacial lake. This failure leads to a rapid and often devastating release of water, capable of causing extensive damage downstream.

Formation of a Glacial Lake

Glacial lakes are formed when glaciers retreat, leaving behind depressions in the landscape. These depressions collect meltwater from the glacier and rainfall, creating lakes that are often held back by moraines—accumulations of debris such as boulders and soil left behind by the glacier.

Sikkim and GLOF

Located in the eastern Himalayan region, Sikkim is home to numerous glaciers. The ongoing melting of these glaciers, accelerated by climate change, has resulted in the formation of various glacial lakes. Some of these lakes present significant GLOF risks to the surrounding communities.

Causes of GLOF in Sikkim

• Moraine Failures: One of the predominant causes of GLOFs. Recently, the moraine dam of South Lhonak lake failed, leading to a catastrophic flood. These natural dams, composed of loose boulders, sediment, and ice, can be unstable and vulnerable to failure.
• Accelerated Glacier Melting: Rising temperatures contribute to a faster rate of glacier melting, increasing the volume of water in glacial lakes and exerting additional pressure on their moraine dams.
• Avalanches or Landslides: Sudden events such as avalanches or landslides can displace large amounts of material into a glacial lake, causing water to overflow and potentially breach the dam.
• Seismic Activity: Earthquakes can destabilize both the moraine dams and the lake bed, triggering an outburst flood.

Sikkim’s Recent GLOF Event

In early October, a significant disaster occurred when the South Lhonak glacial lake in Sikkim burst its banks. Satellite imagery revealed a reduction in the lake’s size post-flood, yet the risk of another GLOF persists due to continued glacier melting and additional inflow from surrounding areas.

Implications of GLOFs

GLOFs can cause widespread destruction, including the washing away of infrastructure, loss of life, and substantial changes to the landscape. The recent GLOF event in Sikkim resulted in considerable casualties and damage to essential infrastructure, highlighting the urgent need for effective disaster management strategies.

Frequently Asked Questions (FAQs)

Q1. What are the main causes of GLOF in Sikkim?
Answer: GLOFs in Sikkim are primarily caused by moraine failures, accelerated glacier melting, avalanches or landslides, and seismic activity that destabilizes the glacial lake’s dam.

Q2. How does climate change affect GLOF risks?
Answer: Climate change accelerates glacier melting, increasing the volume of water in glacial lakes. This extra water heightens the risk of moraine dam failure, leading to GLOFs.

Q3. What impact do GLOFs have on communities?
Answer: GLOFs can cause severe flooding, leading to loss of life, destruction of infrastructure, and displacement of communities, significantly altering local environments.

Q4. What measures can be taken to mitigate GLOF risks?
Answer: Mitigation strategies include monitoring glacial lakes, reinforcing moraine dams, implementing early warning systems, and educating communities about flood preparedness.

Q5. How does Sikkim’s geography contribute to GLOF incidents?
Answer: Sikkim's mountainous terrain and numerous glaciers create conditions conducive to glacial lake formation and increase the likelihood of GLOFs due to unstable moraines.

UPSC Practice MCQs

Question 1: What does GLOF stand for?
A) Glacial Lake Overflow Flood
B) Glacial Lake Outburst Flood
C) Glacial Lake Operational Flood
D) Glacial Lake Observation Flood
Correct Answer: B

Question 2: What is a major cause of GLOF in Sikkim?
A) Urbanization
B) Moraine failure
C) Deforestation
D) River damming
Correct Answer: B

Question 3: Which factor contributes to accelerated glacier melting?
A) Decreased rainfall
B) Rising temperatures
C) Increased snowfall
D) Urban heat islands
Correct Answer: B

Question 4: What can trigger a GLOF event?
A) Heavy rainfall
B) Seismic activity
C) Drought conditions
D) Wind erosion
Correct Answer: B