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Show CHAPTER 7. SNOW SAFETY PLANS Use of an area exposed to avalanche hazard requires a systematic snow safety plan. Such plans are necessarily tailor- made to fit the use and the area. A safety plan for an isolated structure like a mine building could scarcely be applied to a highway extending for many miles. Neither would have much value for a complex development such as a winter sports center. However, all safety plans, regardless of the type of use or character of the area, have the same objective- maximum use with adequate safety- and are prepared in the same way. Knowing the type of use contemplated or already developed, the observer proceeds step by step: 1. Terrain analysis 2. Climate and weather analysis 3. Hazard classification 4. Protective measures 5. Operations plan Terrain Analysis Terrain analysis ( Figure 25) should be made on the ground, and it is desirable for the observer to see the area in both winter and summer. Photomaps of excellent quality are almost a necessity for this work. Topographical maps are of limited value for analysis since they lack sufficient detail. They can be used to record the results after an analysis has been made. The low oblique photomap is the most desirable, followed by ground level panoramas and verticals. Vertical photomaps have a special value for the location of cross- country routes. It is generally possible to pick out the major slidepaths at once and make a tentative route selection. The purpose of the terrain analysis is to identify the slidepaths and the zones of safety, to estimate the effect of natural barriers ( Figure 26) and in general to determine the hazard pattern of the area. This pattern will govern the location of improvements. Buildings are always placed to take advantage of the natural barriers. If this is impossible for any reason, the fact must be noted and recommendations made for protection by other means. It is seldom possible, for instance, to survey an alpine highway on an entirely protected route. However, a hazard reconnaissance prior to construction will always suggest ways of reducing the number of avalanche paths which must be crossed. - 76 - |