Avalanche

Context: Recently, an avalanche struck a Border Roads Organisation (BRO) project site near Mana, India’s “first” village, in Chamoli district, Uttarakhand.

About Avalanche

• It is the downward motion of a large mass of snowline on a slope with high speed and great force causing widespread destruction on its way downhill and in the valley region.
• An avalanche comprises three zones i.e. Starting Zone, Run out Zone, and the Avalanche Track.
• Avalanches occur when the weight of the upper snow layers exceeds the bond with the material underneath. The snow can break loose in chunks or as a wall sweeping victims down the mountain.
• Many times, vibrations caused by loud noise, such as artillery fire, thunder, or rock blasting can set the snow mass in motion, thus triggering an avalanche.

Formation of Avalanche

• Avalanches are primarily caused by three factors:
  • Snow Conditions:
    • Avalanches occur when the weight of the upper snow layers exceeds the bond with the material underneath.
    • Snow metamorphism, influenced by temperature changes, can either strengthen or weaken the snowpack.
    • When snow is soft and fluffy, it has a low angle of repose (17°–30°); as it becomes more cohesive, the angle increases (30°–35°), making slopes more prone to avalanches.
  • Terrain Characteristics:
    • The nature of the ground, including slope steepness and surface roughness, significantly influences avalanche formation.
    • Avalanches generally occur on slopes steeper than 30 degrees.
    • The terrain’s shape can affect how snow accumulates and where avalanches are more likely to initiate.
  • Meteorological Influences:
    • Weather conditions play a crucial role in avalanche dynamics.
    • Heavy snowfall adds weight to the snowpack, increasing the likelihood of avalanches.
    • Strong winds can transport snow from windward slopes and deposit it as wind slabs on leeward slopes, creating unstable conditions.
    • Temperature fluctuations can cause the snowpack to melt and refreeze, altering its stability. For instance, rapid warming can destabilize the snowpack, leading to avalanche formation

Avalanche Prone area:

• According to USDMA, avalanches are common in the Himalayan region with altitudes over 3,500 meters and where the slope is generally more than 30 degrees.
• North-facing slopes are known to have avalanches in winter, whereas south-facing slopes usually get them during the springtime.

Impacts of Avalanches

It can cause significant destruction, particularly affecting transportation routes and structures. Common impacts include:

• Transportation Disruptions: Avalanches can completely disconnect mountain settlements from the rest of the world by covering roads and railways with thick snow, making vehicle movement impossible until the snow is cleared.
• Structural Damage: The force of avalanches can cause structural damage to roads, retaining walls, and buildings, leading to costly repairs and potential displacement of residents.
• Construction Hazards: Avalanches pose significant risks during construction projects in avalanche-prone areas, making certain regions unsafe for infrastructure development.

Preventive Measures and Hazard Assessment

To mitigate avalanche risks, authorities implement various strategies:

• Risk Mapping and Public Awareness: Identifying areas prone to avalanches and informing residents helps in understanding and avoiding potential hazards.
• Afforestation: Planting trees to stabilize snow cover can reduce the likelihood of avalanches by reinforcing the snowpack.
• Artificial Triggering: Controlled explosions or other methods are used to release excess snow accumulation safely, preventing larger, uncontrolled avalanches.
• Predictive Analysis and Early Warning Systems: Monitoring weather conditions and snowpack stability allows for early warnings and evacuation procedures, enhancing public safety.

Implementing these measures is crucial for protecting communities and infrastructure in avalanche-prone regions.