What are Avalanches?

 

Why is it in the news ? 

1. Twenty four workers went missing after an avalanche hit the BRO project site in Uttrakhand. Efforts are being made by Indian Army personnel to rescue workers trapped under mountains of ice affected by continuous snowfall. It is feared that 24 workers were trapped beneath the ice after a devastating glacier avalanche hit a Border Road Organisation Project site at Mana village in the Chamoli District of Uttarakhand on 28th February. 

2. The Avalanche hit the containers inside which construction workers and earth mover drivers were sleeping. There has been continuous snowfall in the area for the past 48 hours. While many of the workers manage to run out of the sheds, others are trapped under a mountain of ice that has covered the site.  

3. Due to the rescue operations, all but four workers could not be rescued and they are supposed to be killed. However, drones, radars, sniffer dogs are being deployed to trace out bodies. The rescue operation is getting difficult because about 20 km of the road leading to the place of occurrence is covered with 5ft of snow and so it is cut off from the main highway. 

4. It should be noted that western Himalaya regions including J & K, Ladakh, Himachal Pradesh and Uttarakhand are prone to frequent avalanches.  

What are Avalanches?

1.Avalanches are masses of materials that move rapidly down a slope. They occur when material on a slope breaks loose from its surroundings and quickly gathers additional materials as it descends. Avalanches can involve materials like rock, ice, debris and snow. Snow avalanches are the most common and may range from small shifts of loose snow to large slab avalanches. They descend at a high speed of 130 km/hr, causing significant destruction of forest and villages. 

2.Avalanches cause damage to roads. Traffic is blocked. Structures coming in the way of an avalanche like bridges, villages, schools, hospitals are damaged. Rivers are blocked causing floods. 

What are the different types of Avalanches? 

Avalanches can be categorised into different types based upon the materials involved. These are snow avalanches, rock avalanches, ice avalanches and debris avalanches.  

How do they occur ? 

1.Avalanches are caused by a combination of terrain, snowpack and triggers.

• Terrain - Steep slopes of mountains at 30 degree to 45 degree are prone to avalanches.

• Snowpack conditions - Weak layers of snow beneath heavier layers can lead to instability. 

• Triggers - Avalanches can be caused by heavy snowfall, rapid temperature changes, earthquakes, vibrations from explosion, human activities like construction, skiing and tracking. 

How do weather conditions affect Avalanche risks? 

1. Weather conditions significantly affect avalanche risks by influencing the stability of the snowpack. Important weather related factors include 

• Heavy snowfall - Heavy accumulation of snow can overload weaknesses in the existing snowpack leading to its instability. If the new snow does not bond well with the underlying layers, it increases the risk of slab avalanches. 

• Strong winds - Strong winds transport loose snow from one area to another causing excessive accumulation on leeward slopes. Secondly, the extra weight increases stress on the snowpack making it unstable and prone to avalanches. Wind slabs are compact snow layers formed by wind driven snow deposition. These slabs create a hard and dense layer over a weaker snow layer. These slabs can easily move down swiftly when disturbed by natural or manmade activities. 

• Rapid temperature rise - A sudden increase in temperature can weaken the snowpack by melting the bonds between the snow layers, thereby, causing avalanches. 

• Rainfall - Rainfall can saturate the snowpack reducing its stability and thereby increasing the possibility of avalanches. 

 Avalanche prone areas in India

1. Avalanches are common in the western Himalayan region. They also occur in the eastern Himalayan region of Arunachal Pradesh. 

2. Gulmarg, Sonmarg and Dras regions of Jammu & Kashmir. 

3. Ladakh

4. Lahaul and Spiti, Kinnaur in Himachal Pradesh

5. Chamoli, Kedarnath, Badrinath and Pitoragarh in Uttrakhand

6. Arunachal Pradesh - Tawang and other high altitude border areas. 

Snow Avalanche Zones 

1.Red Zone - These are areas which witness snow avalanches frequently. It has an impact pressure of more than three tons per square metre.  

2. Blue Zone - Where the avalanche force is less than 3 tons per square metre. These areas can be inhabited by the people. But such areas have to be vacated on warning. 

3. Yellow Zone - These areas are visited by avalanches occasionally. 

What safety measures can be taken to mitigate the impact of Avalanches? 

1. Construction of snow barriers and fences to hold snow in place and prevent them from sudden collapse. 

2. Controlled explosion for controlled avalanches often used by the Indian army. 

3. Artificial terraces and afforestation.

4.Construction of retaining walls to block the flow of avalanches before they reach the road sides. 

5. Deflecting structures are installed to deflect the flow of an avalanche. 

6. Snow sheds are constructed which act as roof structures installed over a road to allow the flow of an avalanche over the roof. 

7. Establishment of avalanche monitoring centres by DRDO in avalanche prone areas. 

8. Establishment of satellite and weather forecasting centres to help prediction of snowfall and avalanche risk.

9. Use of sniffer dogs, beacons and sensors to track trapped individuals. 

10. Personnels of the army, ITBP and Disaster rescue teams are trained. 

Conclusion

Avalanches are a major natural hazard in high altitude regions, particularly in the Himalayas. These regions experience heavy snowfalls and strong winds creating unstable wind slabs and triggering collapses. Although avalanches cannot be prevented, its impact can be reduced by structural reinforcements, early warning systems and controlled detonations. Awareness and preparedness of rescue operators, ITBP and Army are crucial for effective rescue operations and minimising the loss of lives and property.