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Show appeal was filed against withholding a building permit for construction of a vacation house. The reason given was that a situation conflicting with safety laws only exists if " immediate" danger is present. Avalanches that only sweep down occasionally do not present immediate danger. It is possible to give information on the frequency and probability of avalanches by analyzing weather and avalanche statistics. However, since a slide event cannot be predicted in advance, this information is practically useless. This problem can be stated with an example as follows: Should an area that in a span of one hundred or several hundred years recorded only one avalanche be proscribed for building projects? We can imagine such an event occurring the following winter. The reader will arrive at the conclusion that construction would be irresponsible. But if the event is imagined in the distant future, a totally different reaction could be expected. Such problems were recently discussed openly in connection with the avalanche catastrophe " Auf den Boden" in Davos. De Quervain wrote: " To eliminate every possible risk by considering regular avalanche activity and every historical avalanche event as a basis for zone planning, several well- known resorts had to put under the ban entire quarters. A certain final risk in the future must be accepted even if only one serious catastrophe occurs in hundreds of years, or if more frequent but less serious damage is inflicted. The extent of the risk for the different area sections should be evaluated by people that have knowledge of the area or, if possible, by an avalanche expert. The final evaluation on what is reasonable has to be left to a judicial court." The Avalanche Zoning Map should incorporate every danger associated with snow. Factors that should be considered are the type of avalanches, air blast caused by dust avalanches, the erratic path taken by wet snow slides, the creeping and sliding movement of the snow cover and unusual and extreme events. The thankless job of determining the extent of risks to be taken, by defining areas where building should be specified or construction prohibited, is left to the government. Together these constitute the avalanche zoning plan, which then presents the blueprint for local planners. I I. Avalanche Zone Mapping Mountain communities are often scattered over extensive areas with much unproductive terrain which is characterized by boulder fields, rocks and glaciers. To illustrate this, the five largest communities have been selected : Community Total Area Unproductive Terrain Percent Bagnes VS 28' 230 ha 18' 800 ha 67 Davos GR 25' 378 ha 6' 780 ha 27 Zermatt VS 24' 336 ha 21' 800 ha 90 EvoTene VS 20' 997 ha 12' 800 ha 61 Zernez GR 20' 550 ha 7' 240 ha 35 10 |