Study on the development of fluvial landforms after large landslides

点击翻译按钮获取中文摘要

A large slope failure with a volume of 34 million cubic meters took place at Ontakesan, Japan, in Sept.1984. The volume of the failure is the eighth largest among historical large slope failures in Japan. The sediments produced by the failure went down along the valley of the Otaki river, and were deposited in the middle reach. Subsequently the deposits were incised to reproduce sediments which have been transported downstream. This slope failure and subsequent geomorphic changes provide a good example to analyze the development of fluvial landforms and changes in hydrological processes after big slope failures. For this reason, synthetic research were performed in the drainage basin of the Otaki river.Our research focuses mainly on five issues : a) change in channel forms, b) transportation of river sediments, c) rates of erosion and deposition, d) development of terrace scarps and valley forms, and e) change in river runoff. Related issues such as geology, climate, and vegetation in the river basin were also examined. To cover such broad scientific fields, researchers with experiences and knowledge in various fields took part in the group. Some of the members had already worked in the Otaki river basin before the group foundation. The preceding research data were also used in this study. As a result, some new insights were obtained regarding geomorphology, sedimentology, hydrology, climate, and vegetation in the river basin. This publishing report contains ten papers to present our results.Furthermore, our group performed research in other areas of Japan to improve the understanding of fluvial geomorphology, slope failure, river runoff, clinate, and vegetation. Although the results of these studies are not included in this report, they were presented in journals, scientific reports, and conferences. The list of these papers is carried in this report.