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