抄録
From 17th to 18th of August, 1968, very active fronts passing through the southeastern part of Gif u Prefecture, central Japan, brought about extraordinarily heavy rainfall, and disastrous floods and landslides resulted. The authors investigated the relation of the distribution and form of the landslides to rainfall, landf orm and geology. The results are summarized as follows:
(1) After intermittent rain which had continued from the morning of 17th, downpour started by midnight. At the time of the maximum intensity, more than 80 mm of rainfall were recorded during one hour and a half. It was after this time that most of the landslides occurred.
(2) All the landslides are of a small-scale, and only the weathered material 0.5_??_2 meters thick lying on the top has slided.
(3) The area of the most frequent landslides nearly coincides with the area where the maximum hourly rainfall exceeds 60 mm.
(4) The area where few landslides occurred in spite of hourly rainfall exceeding 60 mm has a landf orm composed mainly of gentle slopes.
(5) Between the area of palaeozoic rocks and that of rhyolitic rocks, no difference is found in the density or in the form of landslides.
