Journal of the Japanese Society of Snow and Ice

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For accurate avalanche predictions at cold regions, we observed the relation between snow density and shear strength for new deposited at two sites in Hokkaido：Nakayama Pass and Rikubetsu. Nakayama Pass is located near Sapporo and characterized with heavy snow accumulation (3m in maximum) and low temperature (Tmin is −20℃)．Rikubetsu is located in inland of eastern Hokkaido, where is small snow accumulation area (0.5m in maximum) and one of the coldest region in Japan (Tmin is −35℃)．At Nakayama Pass the shear strength of new snow, lightly compacted snow and compacted snow was smaller than the relation at Tohkamachi in Niigata, about 30% and 21% at the density of 150 and 220 kg m⁻³ respectively, which was similar to the relation at Canadian mountains. At Rikubetsu the shear strength of solid-type depth hoar and depth hoar was smaller than the relation at Canadian mountains, about 50% and 33% at the density of 150 and 250 kg m⁻³ respectively. We also observed the shallow layer of new snow transformed to depth hoar directly, which will become a weak layer and a cause of avalanches after heavy snowfall in short time. We consider that analytical results on the relation between snow density and shear strength in this paper should be used for avalanche predictions using snow metamorphosis models under about −5℃ of maximum air temperature during snow precipitation．

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