Session3: Environmental Hydraulics
Title: INFLUENCES OF RIVER CHANNEL PLANAR SHAPES ON CHARACTERISTICS OF FISH HABITAT IN SMALL-MIDDLE SIZED STREAMS
Kazuaki Ohtsuki, Mori Terutaka, Keigo Nakamura, Yuichi Kayaba
Changes in planer shaped of river channel is affected on river environment. However, knowledge about relations between channel shapes and river environment including river morphology and fish assemblages is not enough so far. In this study, we provide some patterns of hydraulic environment and fish fauna in bending and partial widening reaches in point of comparing on straight reaches based on field survey data in small-middle sized rivers in Japan. As a result, from the viewpoint of the physical habitat properties, bending part typically provide high diversity in depth and velocity by creating pools, while the widened part was uncertain in giving habitat diversity. It strongly relates to invading plants. In point of fishes, there are some differences in dependence on each focused reach. Percentage of fish species found in bended area is larger as fish assemblage in the river is rich but that in widening reaches is opposite. It was suggested that there is a characteristic in the “positive effect” brought to the river channel by the planar shape of the river channel.