Area surveyed is about 220 km², which is predominated by slopes. A half of all sloping grounds has been influenced by landslides where gentle and steep slope appear equally. An uncertain river system and watersheds are concerned in the most recent landslide movements. Topography due to such recent movements corresponds to about 10% of the whole landslide topography.
This district is divided into three parts. The northwest part of gentle slopes is almost covered by basalt, where scattered small landslides are observed. The southwest part is not covered by basalt, in which the best part of steep slopes has in various places large landslides developed in ancient times. The east half part stands in strong relief and is covered equally by basalt and other tertiary layers, where many large landslides of ancient and present movements are concentrated. Contemporary movements are considered as secondary movements of former landslides mainly to grade lower half of hill slopes.

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Quantitative and morphologic variation of river-bed deposits are surveyed by comparison of airphotographs taken in different stages in order to check the annual variation and the influence of disaster of Typhoon No. 26, 1966.
Many profiles along each same cross line settled on the airphotographs taken in 1957 and 1966 are drafted by stereoplanigraph C-8 and the areal variation of each profiles are summarized in connection with the river length between each cross line. In this surveyed area, river bed deposits are increased 2, 740, 000m³in volume for 9 years, and about 370, 000m³are derived by Typhoon No. 26.
The greater part of increased deposits are derived from ready-transported river-bed deposits, terrace deposits and talus deposits along river side, and volume from mountain land slides are not so much.

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