Abstract: Recently, a channelized river was constructed in natural rivers from the point of flood control, and the river fell into drainage channel. During flood stages, it might be impossible for aquatic animals to stay at channelized river. Also, degradation and disappearance of gravel bed might be formed easily, because flood flow was concentrated into the same route for normal stage. The improvement of flow condition in channelized river must be required as soon as possible. As a short-term of construction for the improvement, the installation of stacked boulders might be helpful for both habitat and refuge of aquatic animals. The installation of stacked boulders with about 1 m size was conducted at channelized portion with 20 m wide and 1/200 slope in Kando River, Shimane Prefecture, and a surface jet flow with three dimensional could be formed in both normal and flood stages. The stability of the installation during flood stages has been confirmed in both scale model and prototype. After the installation, several kinds of aquatic animals could be observed around stacked boulders, and movable gravels with 3 mm to 100 mm diameters were deposited below stacked boulders.

Biography: 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.