Ministry of Construction, Japan, started “Model Project for Comprehensive Countermeasures against Snow Avalanches” in 1990 to protect human lives in towns and villages from snow avalanches not only by constructing facilities but also by rationalizing the warning and evacuation system. In this paper, we report the result of examination about the zoning method of threatened areas, which is one of the main items of this model project.
Perla's calculation model was examined to apply the numerical calculation. Since this model has two parameters, combination of which can be selected widely, the relationship between μ and velocity which Schaerer assumed for simplification was applied and unknown parameter became only
M/D.
M/D value were counted backward to fit runout distance of each past avalanche records. Relationship between various factors and
M/D was examined and volume of avalanche was found to have a clear relationship with
M/D. Basically it was assumed that M l D could be estimated by volume of avalanche. Slope length was also found to be another influential factor to
M/D and was adoped to estimate
M/D.
A concrete method to determine dangerous area of snow avalanche was proposed with a scale of probabil-ity and case studies were carried out. Although a few problems still remain, the whole method has been almost completed.
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