GLACIAL LAKE OUTBURST FLOODS (GLOFs)

The Uttarakhand government has constituted 2 teams of experts to evaluate the risk posed by five potentially hazardous glacial lakes in the region. These lakes are prone to Glacial Lake Outburst Floods (GLOFs), the kind of events that have resulted in several disasters in the Himalayan states in recent years.

1. Rising surface temperatures across the globe, including India, have increased the risk of GLOFs.
2. Studies have shown that around 15 million people face the risk of sudden and deadly flooding from glacial lakes, which are expanding and rising in numbers due to global warming.

About Glacial Lake Outburst Floods:

• A glacial lake outburst flood (GLOF) is a sudden release of water and sediment from a dammed lake. These floods can be caused by melting glaciers, avalanches, or earthquakes.

What are Glacial Lakes?

1. Glacial lakes are large water bodies situated in front of, on top of, or beneath a melting glacier.
2. As the glacier retreats, it leaves behind a crater that fills with meltwater, forming a lake.
3. The larger the glacier retreats, the larger and more dangerous the lake becomes.
4. These lakes are often damaged by unstable ice or sediment made up of loose rock and debris.
5. If the boundary around the lake is broken, a huge amount of water starts flowing down the hill, causing floods downstream.

Glacial Lake Outburst Floods (GLOFs) can be caused by a number of factors, including:

1. Glacial retreat: As glaciers melt, they can form lakes that can burst their natural dams if they fill up too quickly.
2. Geothermal activity: Volcanic or geothermal activity can cause glaciers to melt quickly, which can lead to the formation of glacial lakes that can burst their natural dams.
3. Avalanches: Avalanches can create natural dams, which can be destroyed by the pressure of the water that builds up behind them.
4. Landslides: Landslides can introduce large amounts of debris into glacial lakes, which can displace the water and cause a GLOF.
5. Earthquakes: Earthquakes can rupture glacial dams or trigger landslides, which can lead to the sudden release of water from the glacial lakes.
6. Heavy rainfall and snowmelt: Heavy rainfall and snowmelt can cause GLOFs.
7. Cascading processes: A flood from a lake upstream can cause a GLOF.
8. Blocking of subsurface outflow tunnels: This only applies to lakes without surface outflow or lakes with a combination of surface and subsurface outflow.
9. Long-term dam degradation: This is also known as Emmer.

Situation in Uttarakhand:

1. There are 13 glacial lakes in Uttarakhand which are vulnerable to GLOF. Based on available data and research by various technical institutions, these lakes have been classified into three risk levels: 'A,' 'B,' and 'C.'
2. 5 highly sensitive glacial lakes fall in the 'A' category. These include Vasudhara Tal in the Dhauliganga basin and 4 lakes in Pithoragarh district – Maban Lake in the Lassar Yangti Valley, Pyungru Lake in the Darma Basin, an unclassified lake in the Darma Basin and another unclassified lake in the Kuthi Yangti Valley.

FAQs:

Q: What is an avalanche?

1. An avalanche is a rapid flow of snow, ice, rock, and soil down a mountainside or slope.
2. Avalanches are also known as snow slides.
3. They can be caused by natural forces like precipitation, earthquakes, or the weakening of snowpack.
4. Avalanches can also be triggered by human activity, rapid temperature changes, or heavy snowfall.
5. Avalanches can occur on any steep slope, but some locations and times of the year are naturally more dangerous.
6. Avalanches typically occur in mountainous areas with steep slopes and heavy snowfall.
7. Avalanches can be caused by a combination of gravity and the mechanical failure of the snowpack.
8. The slope must be shallow enough for snow to accumulate, but steep enough for the snow to accelerate.

There are several types of avalanches, including:

1. Powder snow avalanches: The largest avalanches, which consist of a powder cloud over a dense avalanche
2. Wet snow avalanches: Low velocity suspensions of snow and water

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