Hydraulic model test results of baffle–brush fish pass

The flow characteristics (depth, velocity, energy dissipation) of a new baffle–brush fish pass were investigated experimentally in a 2 m wide rectangular flume which has a bed slope of 4% for discharges of 100–550 l/s. In all the experiments, quasi-uniform and sub-critical flow conditions and Froude numbers between 0·17 and 0·23 were observed. The Darcy–Weisbach friction factor was negatively correlated with the relative submergence of the brush elements. Two different characteristic velocity regions were identified, namely the baffle region and the brush region. The turbulence intensities were in the range 38–79% in the baffle zone and 13–31% in the brush zone. The hydraulic test results showed that this type of fish pass can produce adequate flow depth and favourable local flow velocities for the design discharge of 0·2 m 2 /s (relative submergence of brushes = 1·03), which is suitable for different fish species.