GS 3 Environment Disaster and disaster management.
Introduction
A glacial lake outburst flood is a type of outburst flood caused by the failure of a dam containing a glacial lake.

Recent Incident:
- Recently a glacial burst has occurred in Nanda Devi glacier in Uttarakhand’s Chamoli district.
- 19 bodies have been recovered so far and over 150 persons went missing in the glacial outburst.
- Many geologists issued warnings that these types of climate-related disasters are going to increase.
- They all pointed out global warming as a major contributing factor to these disasters.
- A part of the Nanda Devi glacier broke off and flooded the Rishiganga river.
- It led to massive floods in the region that damaged many villages in its path.
- The flood also wiped out two hydroelectric power projects on its way;
- The Rishiganga hydroelectric power project (13.2 MW)
- The Tapovan hydroelectric power project
- on the Dhauliganga river (a tributary of the Alakananda).
- Wadia Institute of Himalayan Geology, Dehradun has sent two teams of scientists,will study the possible cause and find out the exact reason behind the glacial burst.
Glacier and Glacier retreat
- Glaciers are large masses of ice that flow slowly downhill like water flowing down as a river.
- A glacier grows (advance) whenever snow accumulates faster than it melts.
- Glacier retreats (shrinks) whenever the melting exceeds accumulation.
- Most of the world’s glaciers have been retreating since about 1850.
Glacial burst
- Retreating glaciers usually result in the formation of lakes at their tips. These lakes are called proglacial lakes.
- These proglacial lakes are often bound by sediments, boulders, and moraines.
- If the boundaries of these lakes are breached, then flooding will take place downstream of that glacial lake. This is called a Glacial Lake Outburst Flood or GLOF.
- The occurrence of GLOF will release a significant amount of water retained in a glacial lake.
- A large amount of water rush down to nearby streams and rivers (like the recent glacial burst that flooded the Rishiganga river).
- This further gathers momentum by picking up sediments, rocks, and other materials on the way.
- In conclusion, GLOF will result in large scale flooding downstream.
- These GLOFs have three major characteristics. They are,
- There will be a sudden release of water and sometimes this might be cyclic in nature.
- GLOFs are generally rapid events. They can range from a few hours to days.
- GLOFs result in large downstream discharges in the river.
- (This often depend on the amount of glacial lake size, level of the breach in the boundary of the glacial lake, etc).
Possible reasons behind the Glacial burst
- A build-up of water pressure or structural weakness of the boundary due to an increase in the flow of water.
- An earthquake (Tectonic) or cryoseism (non-tectonic seismic event of the glacial cryosphere) can cause GLOF. During this, the boundary of the glacial lake will collapse suddenly and release the water of the glacial lake.
- An avalanche of rock or heavy snow:
- During this, the water in the glacial lake might be displaced by the avalanche.
- Volcanic eruptions under the ice can lead to GLOF.
- These volcanic eruptions might displace the boundary or increase the pressure on the glacial lake or both.
- Heavy rainfall/melting of snow:
- This can lead to massive displacement of water in a glacial lake.
- Long-term dam degradation can also cause GLOF.
- Other reasons include the collapse of an adjacent glacial lake, etc.
Other Incidents:
- The Glacial Lake Outburst Flood occurs all over the world except Australia (Glaciers are not found in Australia).
- Peru and Nepal in the past faced deadly or highly destructive glacial floods.
- Dig Tsho glacial lake was present in Eastern Nepal (in a valley next to Mount Everest).
- In 1985 a GLOF occurred in Dig Tsho and brought out the dangerous potential of glacial lakes nationally and internationally.
- The Dig Tsho GLOF resulted in an estimated loss of US$ 1.5 million but fortunately only 4-5 casualties.
- So far 14 GLOF events have been recorded in Nepal.
- In another ten events, the outburst occurred in Tibet (China) but it affected Nepal.
- A flood caused by a GLOF in 1941 in Peru led to the death of an estimated 1,800.
- This event has been described as a historic inspiration for getting into research regarding GLOF.
- In India, in 1929, a GLOF occurred from the Chong Khumdan Glacier in the Karakoram. It resulted into flood in the Indus River.
Vulnerability of Hindu Kush-Himalayan Region to Glacial Lake Outburst Flood(GLOF):
- The Hindu Kush Himalayan (HKH) region is known as Asia’s water tower.
- It has the maximum snow cover after the poles.
- The Hindu Kush Himalayan region sustains more than two billion people directly and indirectly.
- There are numerous glaciers in the HKH region.
- For example, there are 8,800 glacial lakes in the Himalayas and these are spread across countries.
- Among these, more than 200 of these have been classified as dangerous.
- These glacial lakes can trigger the Glacial outburst.
- The soil is getting loose in the HKH region.
- The large human settlements and human activities have resulted in deforestation and large-scale agricultural activities in the region.
- This intensifies the GLOF, as there is no natural barrier to control the flood.
- The factor of global warming and climate change.
- Global warming and climate change lead to glacial retreat and glacier fragmentation (big glaciers splitting into smaller ones).
- According to the Hindu Kush Himalaya Assessment report, even after fulfilling the commitments made under the Paris Agreement,
- one-third of the HKH region’s glaciers would melt and will potentially destabilize the river regime in Asia.
- The heat-island effect in the HKH region.
- The Himalayas are getting warm faster than other mountain ranges.
- This is due to the increase in the use of reinforced concrete (RCC) in building construction instead of eco -friendly traditional wood and stone masonry.
- This adds to regional warming and increases the number of glacial lakes or the water level of glacial lakes.
- Tectonic activity in the region.
- The Indian plate is continuously moving towards north about 2 cm every year.
- So the Himalayas is rising about 5 mm a year.
- This makes the Himalayan region geologically active and structurally unstable.
- Landslides and earthquakes will continue to happen in the region.
- This can trigger a Glacial outburst.
- For example, the entire State of Uttarakhand is categorized as Zone IV (High-Risk Zone) and V ( Very High-Risk zone) of the earthquake risk map of India.
Way forward:
- A long-term solution will be feasible if all the countries start working towards reducing global warming.
- India needs to form clear policy guidelines
- to restrict further human activities like building roads, constructing hotels on banks, etc.
- Any further human activity without proper guidelines will harm the already fragile landscape.
- India needs to undertake a cumulative assessment and strategic planning.
- Geological Survey of India can use satellite images and technology like GIS (geographic information systems) and provide a clear analysis of the HKH region.
- Capacity building of the local community will ensure disaster mitigation in the near future.
- The government has to be proactive and set up an early warning system in the Himalayas.
Conclusion:
India is one of the most vulnerable countries to climate change and global warming. Even though international cooperation is required to restrict the global temperature to 1.5°C, India can move ahead and implement the suggestions.
With this India can be a role model to the other countries in mitigating the disasters.