POOL-AND-WEIR- FISHWAY WITH GRAVEL DEPOSIT AND PROPOSAL FOR SIMPLE IMPROVEMENT

Abstract

 It has been confirmed that gravel deposited in a pool-and-weir-fishway and the fish run-up ratio decreases. In this research, for the purposes of proposing simple improvement, we conducted observe the movements of real fish and hydraulic experiment. As the results, by smoothing the part where the flowing collision collides with the gravel from the partition wall, the turbulence in the flow on the gravel bed is reduced and the number of real fish remaining in place decreases. However, it is considered that the environment was such that the flow velocity across the partition walls and the flow velocity difference in the pool were large and it was difficult to move downstream continuously. Moreover, by disposing a flat plate on the gravel deposited in the pool, the turbulence of the flow on the bed could be reduced and the fish run-up ratio improved. However, the flow velocity increased throughout the pool, and many individuals were washed away downstream. On the other hand, since the flow velocity across the partition walls and the flow velocity difference in the pool are small, it may be considered that the environment was easy to move downstream continuously.