中小河川の中山間地から扇状地区間における河道平面形状による魚類生息場および種の特性の比較

抄録

Recently, serious flood disasters have been occurred in small- medium-sized steep rivers from mountainous to fluvial fan segments, however, there are few guidelines for designing plane shapes of river channel for disaster recovery works due to lack of studies on relationship among the channel plane shape, topography and environment in such segments. In this study, we provided information on the relationship by comparing field data of river morphology, flow environment and fish assemblage in different types of channel shape, straight, bended and widening. As a result, it is found that formation of pools is likely to occur in the bended part but not in the widening part. In terms of greatly widened reach, stream shrinkage by sedimentation and plant invasion occurs, which also affects the formation of the riffle-pool flow environment. Comparing the obtained fish assemblage data with that in straight parts as a reference, the bended part has a role of providing a specific habitat not seen in the straight part and the widening part likely work to enhance habitat diversity where the environment already reasonably good.