徳島県那賀川上流域に分布する地すべりの地形的特徴

In this study, Geomorphological features of landslide distributed in the upper stream of Naka-river, Tokushima, are studied with air-photograph interpretation and map reading. The number of landslide in investigation area is 0.29 number/km2 in Chichibu belt, 0.34 number/km2 in Kurosegawa belt, 0.17 number/km2 in Sambosan belt and 0.09 number/km2 in Shimanto belt. The most number of landslide is Kurosegawa belt and the least number of landslide is Shimanto belt. Landslides show tendency to become smaller in equivalent coefficient of friction as a large scale landslide. Direction of landslide in Kurosegawa belt has a lot of trend of NNE to NE and in Chichibu belt has a lot of trend of ENE to E. Some 63% is in under 50 meters of height from river bed to end of landslide body, but some 23% is in over 100 meters. Deepening of river beds proceeds in transverse valley at the Sakasyukito-river in Kurosegawa belt, while ingrown meander grows in the Naka-river that flows in Sambosan belt and Shimanto belt. Distribution of landslides in these areas is related to the effect of deepening and lateral erosion of river.