Abstract
In August, 1980, a great number of slope-failure occurred at Tomiura area, Noboribetsu City. In this area, late Pleistocene pyroclastic deposits of Kuttara Volcano are widely developed.
Results obtained from this study are as follows:
1. The slope-failure is caused by heavy rains with maximum intensity reaching 40-60 mm/hour.
2. The original slope-failure is produced by the abundance of water absorbed by the piping system of the slope, is occurred at the cutting slope of the City Road and Route 36.
3. At the top of the natural slope, hollowed area, secondary collapse and gully erosion occurred, producing the debris flow. This debris flow ran down the valley wall taking off the surface soils and made the gullies.
