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Vol.52-5 CONTENTS

Geomorphological Features of Avalanche Furrows in Heavy Snow Region in Japan

Abstract

The occurrence of full-depth snow avalanches (FDSAs) on slopes in Japanese mountain areas is indicated by narrow straight scratch patterns, called "avalanche furrows", on aerial photographs. Avalanche furrows show a semicircular or U-shaped transverse profile as if they had been scored by a round chisel. They have a width of 2-4 m and a depth of 1-3 m and occur mainly on slopes with a 35°-45° inclination. Avalanche furrows are exposed on a smooth surface of bedrock and show striae produced by FDSAs.
      Aerial-photo interpretation over Japanese Islands shows that avalanche furrows are mainly distributed from Hokkaido to the Chugoku Mountains along the Japan Sea coast. The distribution of avalanche furrows corresponds to mountains with deep snow cover over 2 m and increases with altitude. In other countries, wet snow avalanches occur mainly in polar and alpine areas with much colder climates. In contrast, FDSAs occur in temperate climates and at altitudes as low as 300 m in Japan. The major factors controlling the formation of avalanche furrows in Japan are considered to be the temperate climate, heavy snowfall, steep slopes and poor vegetation.

Contents

1. Introduction
2. Characteristics slopes subjected to full-depth snow avalanches
3. Morphology of avalanche furrows
4. Local distribution of avalanche furrows
  4.1 Slope inclination
  4.2 Direction
5. Regional distribution of avalanche furrows in Japan
  5.1 General characteristics
  5.2 The effect of altitude
6. Discussion
  6.1 Formative factors of avalanche furrows
  6.2 Comparison of snow avalanche landforms between Japan and other countries
  6.3 Avalanche patches on full-depth snow avalanche slope
  6.4 The effect of surface avalanche
  6.5 Investigation of the snow avalanche landform using airbone laser scanning
7. Conclusions and perspective on snow avalanche research
References

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