Alternative mitigation measures for fish passage in standard box culverts: Physical modelling

Abstract

Abstract:Road crossings and culverts are common man-made structures along river courses, ranging from national highways to rural roads and urban networks. Present expertise in culvert hydraulic design is deficient because many empirically-based guidelines are often inadequate for fish passage. This project focused on the development of simple solutions for box culverts, with the aim to maximise slow flow regions suitable for small-bodied fish passage and to minimise the reduction in discharge capacity. Herein a physical study of box culvert was performed under controlled flow conditions, and seven designs were tested. In all the cases, the turbulence of the flowing waters was used to assist with fish migration. One baffle configuration presented promising results: i.e., small corner baffles. The triangular baffle system produced little additional afflux, while creating excellent recirculations both upstream and downstream of each baffle. Another configuration was based upon a rough bed and sidewall, enhancing secondary currents and recirculation in the corner region. This resulted in flow conditions that could be potentially used to enhance small-bodied fish passage, though further experiments involving detailed fish behaviour study are required for quantitative guidelines.

Hybrid modelling of low velocity zones in an asymmetrical channel with sidewall longitudinal rib to assist fish passage

“…Longitudinal velocities below 0.75 × V mean covered around 18% of the cross‐sectional area of the flume. Data from experiments conducted under similar flow rates by Cabonce, Fernando, Wang, and Chanson (2017, 2019) and Wang, Uys, and Chanson (2018) showed longitudinal velocities below 0.75 × V mean covering areas between 21% and 32%. Compared to these configurations, the sidewall rib geometry appeared to produce lesser LVZ areas.…”

“…Fractions of low velocity regions where V x / V mean is less than a set value, for different discharges and longitudinal locations—comparison with smooth channel data (Cabonce et al, 2019) (black hollow symbols), asymmetrical rough channel data (Wang et al, 2018) (black symbols) and present CFD using a Reynolds stress model on a refined mesh [Colour figure can be viewed at wileyonlinelibrary.com]…”

Modelling upstream fish passage in standard box culverts: Interplay between turbulence, fish kinematics, and energetics

“…Detailed velocity measurements showed the existence of sizeable slow‐velocity regions next to the left rough sidewall and at the corner between the rough bed and sidewall, which might be suitable to the upstream passage of small body mass fish. Wang, Uys, and Chanson () tested several baffles designs in a standard box culvert model. One configuration, a series of corner baffles, assisted with the development of recirculation zones between each baffle, with a small increase (10%) in afflux at design discharge, and might be suitable to small‐body‐mass fish species.…”

Hybrid modelling of low velocity zones in box culverts to assist fish passage: Why simple is better!

“…Boundary roughening induces a decrease in flow velocity by increasing boundary friction and thickening the boundary layer regions. Wang, Chanson, Kern, and Franklin (2016); Wang, Uys, and Chanson (2018) conducted physical experiments to study the effect of various boundary roughness on fish passage. The study included both hydrodynamic and fish behaviour investigations with small‐bodied fish, adult Duboulay's rainbowfish ( Melanotaenia duboulay ) and juvenile silver perch ( Bidyanus bidyanus ) (Figures 5c,d).…”

“…The physical modelling combined several datasets for the velocity fields on a smooth invert for a 12 m long 0.5 m wide box culvert barrel flume (Cabonce et al, 2017, 2019; Wang et al, 2016, 2018). The experimental conditions were limited to only one box geometry and a few inflow conditions.…”