Hydraulics of Roughness Mild Slope With Stacked Boulders in Half Trapezoidal Section

Youichi Yasuda, and Nozomi Fuchino

Department of Civil Engineering, College of Science and Technology, Nihon University, Tokyo, Japan

Abstract: Many kinds of fish passages have been installed in order to help the upstream migration for swimming fishes at hydraulic drop structures. Especially, pool-type fish passage was applied for both rest and upstream migration. In each pool, a plunging flow is formed, and also the capacity of discharge is limited in order to keep steady flow condition. For the formation of plunging flow, it is difficult for multi-aquatic animals to find the migration route. In this paper, roughness mild slope with stacked boulders in half trapezoidal section was presented as a new construction of fish passage. In proto type, around 50 cm long size was utilized as the stacked boulder. The longitudinal slope was settled as 1/25, and the fish passage had 4 m width with around 1/8 transverse slope. The migration route for multi-aquatic animals can be kept, even if the discharge changes from 0.45 m³/s to 3.2 m³/s. As the main flow passing over the roughness slope is always located near the water surface for several tailwater elevations, it might be easy to find the migration route.

Key words: stacked boulders, roughness mild slope, surface jet flow, diverse flow, migration route