Rock-weir fishway I: flow regimes and hydraulic characteristics

ABSTRACT

In recent years, ecologically oriented river engineering practices such as nature-like fishways have become a common solution to mitigate or compensate for negative environmental impacts. This study investigated the flow regimes and hydraulics of rock-weir-type nature-like fishways for different structure geometries (weir configurations, pool spacing and boulder diameter) and channel characteristics (bed slope and flow rate). A criterion was proposed to predict three distinct flow regimes (weir, transitional and streaming) based on quantitative thresholds associated with three dimensionless parameters for discharge, pool spacing and pool water depth. For the depth–discharge relationship, a new equation to predict the weir flow based on water depth, weir length and bed slope of the fishway was introduced. Finally, a maximum velocity reduction factor as a function of discharge was proposed to predict maximum weir velocity in rock-weir fishways. These results must be compared with the swimming ability of the fish that the fishway is being designed for to assess passability.

KEYWORDS:

• Computational fluid dynamics
• depth–discharge
• fishway
• flow regimes
• hydraulics
• maximum velocity
• rock-weir
• velocity profiles

Acknowledgments

Special thanks due to Cody Kupferschmidt and Perry Fedum, who carried out the physical model study at the T. Blench Hydraulics Laboratory of the University of Alberta, and two anonymous reviewers for their constructive comments and suggestions.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was made possible through grants from the Natural Sciences and Engineering Research Council (NSERC) of Canada and Ecofish Research Ltd. under an NSERC Industrial R&D Fellowship programme.