Avalanche

An avalanche is a mass of snow and ice falling suddenly down a mountain slope and often taking with it earth, rocks and rubble of every description (WMO, 1992).

Thousands of avalanches occur every year, killing an average of 500 people worldwide. Avalanches occur when massive slabs of snow break loose from a mountainside and shatter like broken glass as they race downhill. These moving masses can reach speeds of 130 km/hour within about five seconds. They cannot always be predicted but the weather conditions, which make them more likely, can be forecast in advance. Most accidents now occur because people ignore warnings. The majority of avalanche incidents are due to slab avalanches with skiers involved. Avalanches are bigger, travel greater distances and are triggered earlier in the year. These changes can be attributed clearly to rising temperatures, which have reached 0.2 to 0.4 degrees annually in some parts of the Himalayas.

Avalanche protection and control measures include early warning which is key (EAWS). By way of controlled explosions, artificial avalanche triggering aims temporarily to safeguard possible starting zones (SLF). Defensive structures prevent the formation of avalanches. In order circumstances, when an avalanche is released, it can be diverted or intercepted by a dam. Other means of protection against avalanches include physical structures for buildings and snow sheds (SLF).

Avalanche risk factors

  • Quick changes in weather, snowpack and terrain.
  • Increasing human populations: winter sports lovers at ski resorts and developers building in vulnerable locations.
  • Climate change.

Vulnerable areas

  • Human settlements in avalanche-prone zones.
  • Rural mountainous villages with no early warning systems.
  • Human settlements with no forest cover.
  • Skiing populations and tourists not educated in avalanche risk.

Risk reduction measures

  • Not constructing buildings, roads, etc. in avalanche hazard areas.
  • Early warning systems at local and national levels.
  • Information on avalanches, their impacts and risks for tourism information offices.
  • Tree planting to protect against the release of avalanches.
  • Building codes and appropriate materials to reinforce resilience.
  • Raising awareness, educating and training residents and visitors on what to do before, during and after an avalanche.

Latest Avalanche additions in the Knowledge Base

Update

Switzerland: Exceptional avalanche situation in January 2018 well handled

For the first time in 20 years, the highest danger level was forecast in large parts of the Swiss Alps in January 2018. Despite 150 destructive avalanches occurring, no lives were lost in settlements or controlled areas. The measures introduced after the extreme winter of 1999, when the occurrence of avalanches was very high, have proven effective.
WSL Institute for Snow and Avalanche Research SLF
Documents and publications

Using forest ecosystems to build resilience in Chile

Ecosystem-based adaptation (EbA) is an increasingly popular and tested strategy among governments looking for the best ways to help their people adapt to the challenges of climate change. The Ecosystems Protecting Infrastructure and Communities (EPIC)

Update

USA: Avalanche forecasters say Rocky Mountain region now at higher risk

Storms sweeping across the Rocky Mountains have caused the highest avalanche danger since ratings started in 1973. More than 3,000 avalanches have already occurred in Colorado alone, and they are unusually large. As the climate warms, wet snow avalanches could start weeks earlier than normal, leading to a longer avalanche season and increasing the risk of disaster.
Public Radio International
Update

Switzerland: Large-scale hazard indication mapping for avalanches

To calculate and visualize potential avalanche hazards, researchers at the SLF have developed a method that automatically and efficiently pinpoints avalanche starting zones. Using RAMMS, a simulation software, researchers can model avalanches to produce danger maps that facilitate risk management.
WSL Institute for Snow and Avalanche Research SLF
Update

Avalanche winter 1999 in Switzerland

February 1999 saw a spate of avalanches throughout the Alps, claiming many lives and in some cases causing extensive damage to property. Switzerland learned lessons from this experience, in particular by improving the training and organisation of avalanche services. But even today there is no absolute security.
WSL Institute for Snow and Avalanche Research SLF
Documents and publications

Natural hazard fatalities in Switzerland from 1946 to 2015

A database of fatalities caused by natural hazard processes in Switzerland was compiled for the period between 1946 and 2015. Using information from the Swiss flood and landslide damage database and the Swiss destructive avalanche database, the data set

Update

Switzerland: What’s the real risk from avalanches?

With a twice-daily national avalanche bulletin, hazards maps, and protocols for days of high risk, Switzerland has averaged 100 avalanches and 23 fatalities since 1999. The density of the avalanche warning network and the level of training and expertise is unique to Switzerland, but the network cannot catch every avalanche.
swissinfo.ch - International Service of the Swiss Broadcasting Corporation
Update

Switzerland: New maps illuminate avalanche terrain

The SLF has developed maps that illustrate threats of typical skier-triggered avalanches in the Swiss Alps. The maps depict situations in which small to large avalanches are expected, provide a basis for interpreting the avalanche terrain, and facilitate both tour planning and route selection.
WSL Institute for Snow and Avalanche Research SLF
View all content in the Knowledge Base
View all Hazards

Is this page useful?

Yes No Report an issue on this page

Thank you. If you have 2 minutes, we would benefit from additional feedback (link opens in a new window).