This document discusses natural disasters and focuses on avalanches. It defines an avalanche as a rapid movement of snow down a slope due to structural weakness in the snow cover. There are three main types of avalanches: loose avalanches which can occur with little warning; slab avalanches, the most commonly occurring type, often started by human error; and slush avalanches which usually occur later in the season. Avalanches are caused by layers of snow building up strength and then a vibration or temperature change causes the snow to slide down the mountain. Avalanches pose deadly risks by trapping and killing people under the snow and damaging infrastructure.

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-By Ameya Singh
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2. Natural Disaster and its Types
•A natural disaster is a major adverse event
resulting from natural processes of the Earth
Avalanche
Thunderstorms
Tornados
Earthquakes
Tsunami
Hurricanes
Landslides
Volcanoes
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3. Avalanches
What is Avalanche?
An avalanche is a rapid movement of snow
down a slope as a result of structural weakness
in the snow cover
Three main forms:
• Loose
• Slab
• Slush
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4. Loose Avalanche
These can occur with little warning
At any time in the season
Speeds up to 300 km/hr
Force up to 50 tonnes per m2
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5. Slab Avalanche
The most commonly occurring type
Often started by human error
Speeds up to 10 – 150 km/hr
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6. Slush Avalanche
Usually occur later in the season
Movement rate 8 – 25 km/hr
Carry a considerable weight of snow – up to 1 million
tonnes
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7. What causes Avalanches
Avalanches are caused by layers of snow
building up and gaining strength
A vibration, voice or a train can cause a
avalanche
Rapid temperature changes which cause the
snow to melt or where rain falls on to the snow
When water under the snow build up, it can
cause an avalanche
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8. Avalanche Prone Regions
Avalanches are common in mountainous
areas of the world, especially in Arctic and
temperate regions
Frequency is variable according to local
climatic and topographic conditions
Examples: Alps, Scandinavian countries, US
and Canadian Rockies
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10. Effects of Avalanches
Avalanches can tear down trees, plants and ski lifts
Avalanches kill people by trapping them under the snow
Death and injury from the avalanches are the results of
impacts which fracture limbs, suffocation, hypothermia,
exhaustion, frostbite and shock
Communications, power lines and transport routes are
at risk
Buildings and structures are at risk from impact
pressures of up to 100 tonnes/m2
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11. Modifying the Avalanche
Most management techniques aim to retain the snow
on the mountainside or to deflect the avalanche
Artificially Triggering avalanches using explosive
charges or shelling at safe times and before the
snow accumulates to dangerous levels.
Planting tress along known avalanche paths.
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12. Modifying Vulnerability
Warning systems
These use forecasts and prediction
Land use planning / Avalanche Zoning
This identifies 3 zones:
•High potential
•Moderate
•No hazard
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