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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.

New simulations can improve avalanche forecasting.

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

Uploaded on
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.

European Geosciences Union
Update
Switzerland: What’s the real risk from avalanches?

On Thursday, an avalanche crashed spectacularly into a hotel restaurant at a small mountain resort in eastern Switzerland. Three people received minor injuries. What are the avalanche risks in Switzerland and how are such hazards monitored?

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)
Research briefs
Climate change leading to water shortage in Andes, Himalayas

New research finds that glaciers in the Andes mountains and the Tibetan plateau are melting more rapidly than at any point in the last 10,000 years, potentially triggering avalanches and floods while jeopardizing future water supply. By 2100, half the ice will disappear under the best case scenario - the worst case scenario predicts a decline of two-thirds.

Ohio State University
Update
Switzerland, Austria: Managing avalanche risks wins UNESCO status

Switzerland and Austria have been awarded coveted UNESCO intangible cultural heritage status for their management of avalanche risks. The award celebrates well-known traditions, art forms and practices. Switzerland’s management approach in particular is unique because of its long history, which dates back centuries, and its level of sophistication.

WSL Institute for Snow and Avalanche Research (SLF)
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