Daily Answer Writing
30 June 2021

Q) Discuss the causes of an avalanche. Describe the mechanisms for preparedness to reduce the risk during such events. (150 Words)

Source: <https://www.thehindu.com/news/national/chamoli-disaster-due-to-avalanche-says-geological-survey-of-india/article35031786.ece>

GS 3: Disaster management

Approach Answer:

Introduction: An avalanche  is a rapid flow of snow down a slope, such as a hill or mountain. Primarily composed of flowing snow and air, large avalanches have the capability to capture and move ice, rocks, and trees.

 

They occur in two general forms, or some combination: slab avalanches made of tightly packed snow, triggered by a collapse of an underlying weak snow layer, and loose snow avalanches made of looser snow. After being set off, avalanches usually accelerate rapidly and grow in mass and volume as they capture more snow. If an avalanche moves fast enough, some of the snow may mix with the air, forming a powder snow avalanche.


Major Causes of Avalanch

  • Natural factors:
  1. Earthquakes: They disrupt the stability of the latent snow causing it to slide.
  2. Snowstorm and Wind: Wind normally blows from one side of the slope of mountain to another side. This may cause snow storm.
  3. Heavy snowfall: it deposits snow in unstable areas and puts pressure on the snow-pack. Precipitation during the summer months is the leading cause of wet snow avalanches

 

  1. Layers of Snow: There are conditions where snow is already on the mountains and has turned into ice. Then, fresh snow falls on top which can easily slide down.
  2. Steep Slopes: Layers of snow build up become heavy and slide down the mountain.
  3. Warm Temperature: Warm temperatures that can last several hours a day can weaken some of the upper layers of snow and cause it to slide down.
  4. Movement of Animal: This too can destabilise the snow

 

  • Human Activity: Humans have contributed to the start of many avalanches in recent years.
  1. Winter sports: Winter sports that require steep slopes often put pressure on the snow-pack which it cannot deal.
  2. Vibration or Movement: The use of All Terrain Vehicles and Snowmobiles creates vibrations within the snow that it cannot withstand. Coupled with the gravitational pull, it is one of the quickest ways to cause an avalanche.
  3. Construction activities: can cause vibrations which can trigger avalanche. For example the recent Chamoli disaster.
  4. Mining: It hollows the relief making the slope unstable.

 

Strategies to mitigate avalanche risks

  • Stabilization of slopes: slopes with pitches greater than 25 degrees are dangerous. 
  • Plantation: Treeless slopes and gullies are particularly susceptible to avalanches. The absence of trees may reflect that previous avalanches have occurred in the area. 
  1. Avoiding Hiking after storm: Avoid hiking immediately after a storm. Most avalanches occur at the time of or shortly after a heavy snowfall
  2. Snow retention and retardation  structures (snow racks, avalanche snow bridges, snow nets), used in the upper path of probable avalanche paths. Snow guard devices (used to increase snow retention on roofs). For example avalanche net and avalanche dams.
  3. Snow redistribution structures (wind baffles, snow fences): Snow deflection structures used to deflect and confine the moving snow within the avalanche track. They should not deflect the avalanche sharply, because in the latter case they may be easily overrun by snow.
  4. Monitoring natural movement: For example, HIMANSH is a project in Spitit district of Himachal Pradesh using Terrestrial Laser Scanners (TLS) mounted on UAV that would digitize the glacier motion and snow cover variations with exceptional precision.
  5. Regulation of construction and mining activities: Which significantly enhance the risk of disaster.
  6. Local community participation: For planning and risk assessment in the area.

 

Conclusion: Avalanches are one of the most severe disasters that India faces. In the past couple of decades several hundreds of our solders have died in Siachin, and disasters like Chamoli are common in the Himalayan region. India need a comprehensive policy in this regard with regulatory updates and use of technology for prevention and mitigation of the disaster.

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