Classification of rivers based on fluvial land forms and debris transport processes in Yaku Island, southern Japan.

在形态计量学分析和野外调查的基础上，探讨了日本南部雅库岛的地形起伏条件、碎屑的产生和搬运过程。日本山脉的平均海拔与平均起伏呈较强的正相关。雅库岛的最高点在这条回归线附近，这表明该岛的地势与它的海拔相当。崖库岛中部是海拔最高的地区，地势比其他地区要低。雅库岛在低海拔地区地势很高，在高海拔地区地势很低。在海岸的高起伏地区，有深谷和陡峭的斜坡。在岛中部的低起伏区，低起伏面分布在山脊上。在中上河段，通过较大的起伏区，河床上充填着巨大的砾石，其最大直径为3 ~ 10m。随着河道坡度的减小，最大粒径向下游逐渐减小，说明这些巨大的砾石是受到分选过程的影响而运移的。在这些河段与干流汇合的支流上有许多滑坡疤痕。在这些支流的交汇处，在主河道的谷底形成冲积锥。河床和冲积锥的沉积物包括几米大小的砾石。雅库岛独特的地形条件可归因于该岛的隆起特征。块体产量巨大与地质特征有关。这些土块有时会在支流与干流的交汇处形成滑坡坝。这些巨大的砾石是由支流头部的山体滑坡或大坝的溃决引起的大规模泥石流或洪水带来的。

Based on morphometric analysis and field survey, the relief condition, debris production and transport processes of Yaku Island, Southern Japan are discussed. Mean altitude and mean relief derived from Japanese mountains show a strong positive relationship. The highest point on Yaku Island plots near this regression line indicating that the relief of the island is high enough for its altitude. The relief in the central area of Yaku Island, which is the area with the highest altitude, is lower than in other regions. Yaku Island has very high relief in lower altitude areas and very low relief in higher altitude areas. In the high relief areas of the coast, there are deep valleys with steep slopes. In the low relief areas of the central part of the island, low relief surfaces are distributed on the ridges. In the upper-middle reaches through the large relief area, huge gravels, whose maximum diameters are 3-10m, fill on the riverbed. Gradual downstream decrease of maximum diameter according to the decrease of channel slope shows that these huge gravels were transported being affected by sorting process. There are many landslide scars in the tributaries which join the main stream in these reaches. At the junctions these tributaries develop alluvial cones on the valley floor of the main stream. The deposits of the riverbed and the alluvial cones include several meters size gravels. The distinctive relief conditions of Yaku Island can be attributed to the uplift characteristics of the island. Huge block production owes to the geological characteristics. These blocks sometimes formed landslide dams at the tributary junctions with the main stream. Large debris flows or torrential floods, caused by landslides in the tributary heads or burst of the dams, transported such huge gravels.