Environmental Engineering Reference
In-Depth Information
Chapter 2
Snow Avalanches
2.1. Introduction
Over the last century, recreational activities, transportation and constructions
in high-altitude areas (ski resorts and dams) have shown a rapid growth in many
mountain ranges in Europe and North America. In these areas, snow avalanches are a
major threat, causing damage and death. A typical example in recent years is provided
by the winter of 1999, during which several snow storms hit the Alps, producing huge
avalanches, which reached the valley bottoms and killed 62 people in their house.
The growth in winter sports has also led to a significant increase in avalanche deaths
over the last few decades, with some 200 skiers or alpinists killed worldwide on
average every year. Some years such as in 2006, the death toll can be as high as
300 persons killed by avalanches in Europe. There is thus a rising demand for higher
safety measures.
For more than a century, scientists have been studying avalanches to try to improve
predictions of when they will occur and to optimize defenses against them. In the
late 19th century, the Swiss forest engineer Johann Coaz started studying snow
and monitoring several paths around Davos, which allowed him to publish the first
monograph on snow avalanches [COA 81]. Another forest engineer, Paul Mougin,
proposed a very simple model in the 1920s to calculate avalanche velocity and run-out
distance [MOU 22]. The model assumes that avalanches behave like sliding blocks.
It is still used (in a modified form known as the Voellmy model) by engineers
today. A more realistic generation of models, first put forward in the 1970s by
Soviet researchers Sergei Grigorian and Margarita Eglit, relies instead on an analogy
with flash floods and uses differential equations that describe the motion of water
waves [GRI 67].
Search WWH ::




Custom Search