Professor, Laboratory of Environmental Hydraulics, Department sub-head of Civil Engineering, College of Science and Technology, Nihon University, Japan

Youichi YASUDA started his research carrier on hydraulics of drop structures with Prof. Ohtsu, and he earned a Doctoral degree in Engineering from Nihon University in 1993. After that, he has been mainly focusing on assessing eco-hydraulic researches on fish passage for the upstream migration of multi-aquatic animals, hydraulics below hydraulic drop structures (Dam, Check dam, Sabo dam, Irrigation weir, and Ground sill), drainage ability of rain flows in pipes, river restoration, nature conservation projects, and etc. He also was honored by ASCE (American Society of Civil Engineers) as Karl-Emil Hilgard Hydraulic Prize (Best paper in Journal of Hydraulic Engineering prize) in 2000, and J. C. Stevens Award (Best Discussion paper in Journal of Hydraulic Engineering prize) in 2005 and 2013.

Speech Title: Eco-hydraulics on Stacked Boulders below Low Drops

Abstract: Many fish passages were installed at several types of drop structures. Unfortunately, most of fish passages did not worked as migration route of fishes, because the problems might be caused by poor design for the installation plan, river degradation below drop structure, sediments of driftwoods and gravels, destroy of fish passage due to transported rocks, and etc. As the reconstruction of permanent fish passage needs high cost and long time for the project process, it might be difficult for local prefecture to decide the improvement of the fish passage. Also, there is poor information on the protection method against the river degradation below drop structures. The jump formation might not be helpful for the protection of river bed even if the horizontal apron and the protection brocks are installed on the basis of hydraulic design manual. The naturally stacked boulders can be found in natural rivers, and the stability of the boulders might be confirmed after many flood stages. While, there is poor study on flow characteristics and structure in natural stacked boulders. As an artificial design, the installation of stacked boulders below low drop structures has been proposed. The field and experimental investigations may help that the fish passage with stacked boulders is effective for the upstream migration of aquatic animals, the stability of structure after floods, the short period and low cost for the construction. Also, the surface jet formation on the stacked boulders during flood stages might be effective for the protection against the river degradation below low drop structure. The author would like to present the possibility for the application of stacked boulders in the conference.