Glacial Lake Outburst Flood [GLOF]

The melting of mountain glaciers throughout the world is one of the most significant signals of global climate change. Melting glaciers around snow-capped mountains increases the danger of glacial-related risks. Glacial Lake Outburst Flood are one of these dangers (GLOFs).

What is Glacial Lake Outburst Flood?

A GLOF is the abrupt discharge of water from a reservoir fuelled by glacier melt that has developed at the glacier's in front, edge, beneath, within, or on the top.

GLOFs, are created by the discharge of naturally frozen lakes in glaciers, on or near their margins. GLOFs are not a recent concept, but with the melting of glaciers throughout the world and rising temperatures, the likelihood of their occurring in several snow-capped mountains has increased.

How does GLOFs form?

When glaciers move, glacial lakes emerge inside moraine or ice 'dams'. These 'dams' are rather weak and can unexpectedly burst, releasing a massive amount of water and debris. Such eruptions release millions of cubic metres of water in a matter of hours, producing catastrophic flooding downstream and significant property and human loss. Some known direct causes of GLOFs includes heavy snowmelt/rainfall and melting of ice forming the dam, earthquake, long-term degradation of the dam, etc.

GLOFs in the Himalayas

GLOFs are alleged to have triggered flash floods in the Chamoli area of Uttarakhand in February 2021. A glacial lake break was also involved in the 2013 Kedarnath disaster, which killed over 5000 people.

In the Himalayas, glacier melt has gradually created over 5,000 glacial lakes, which are blocked by highly risky moraines. When these dams fail, the resulting GLOFs can have disastrous socioeconomic and geomorphic consequences.

National Disaster Management Authority (NDMA) says that Glacial retreat owing to climate change in most regions of the Hindu Kush Himalaya has resulted in the emergence of several new glacial lakes, which are the primary source of GLOFs. Glacial lakes are expanding due to the receding glaciers in the Himalayas, posing significant damage to downstream civilization and lifestyle.

Dam Breach Modelling (DBM) to tackle the Risks of GLOFs

The Bhote Koshi floods of 2016 placed the lives of around 200 Nepalese families in jeopardy. The flood was first considered to be caused by heavy rains, but a year later, experts from the Department of Hydrology and Meteorology (DHM) discovered that the actual cause was a GLOF in Tibet was to blame. The GLOF breach in this flood was caused by a glacial lake which was nearly equal to 7 Olympic-size swimming pools that covered an area of approx. 9,000 m2.

To address the risks of GLOFs for communities near Koshi River, the United Nations Development Programme (UNDP) in Nepal, International Centre for Integrated Mountain Development (ICIMOD), and DHM have jointly aimed at educating DHM personnel, on the principles of DBM.

• This modelling helps measure the implications of a prospective flood disaster.
• DBM examines the incidence of the breach and also the water flowing from the resultant breach.
• Before such disasters, DBM may assist local governments and communities in preparing and implementing rescue operations and other disaster recovery protocols.

Further, timely identification of GLOFs is critical to handling upcoming disasters. Analysis of records of past events, field observations, examination of geomorphologic attributes of the dam/lakes and the areas in its vicinity, the study of other physical conditions, etc. are some of the factors to consider for prompt identification of GLOFs.

Rapidly increasing global warming and changing climatic conditions has escalated the occurrence of GLOFs. Hence, it is imperative for the communities at risk to be prepared as they are the primary observers of a disaster before professional rescue workers arrive.

FAQS on Glacial Lake Outburst Flood

Q.1. What is Glacial Lake Outburst Flood?

A Glacial Lake Outburst Flood is the abrupt discharge of water from a reservoir fueled by glacier melt that has developed at the glaciers in front, edge, beneath, within, or on the top.

Q.2. What causes Glacial Lake Outburst Flood?

Some known direct causes of Glacial Lake Outburst Floods includes heavy snowmelt/rainfall and melting of ice forming the dam, earthquake, long-term degradation of the dam, etc.

Q.3. What are the effects of the Glacial Lake Outburst Flood?

Glacial Lake Outburst Flood causes millions of cubic metres of water in a matter of hours, producing catastrophic flooding downstream and significant property and human loss.

Q.4. How to handle the Glacial Lake Outburst Flood?

Timely identification of the Glacial Lake Outburst Flood is critical to handle any impending disasters. Analysis of records of past events, field observations, examination of geomorphologic attributes of the dam/lakes and the areas in its vicinity, the study of other physical conditions, etc. are some of the factors to consider for prompt identification of GLOFs.