Author(s): Hubert Chanson

Linked Author(s): Hubert Chanson

Keywords: Standard box culverts; Upstream fish passage; Hydraulic engineering; Small-body-mass fish; Low-velocity zones;

Abstract: While important for delivering a range of important socio-economic services, road crossings and culverts are known to block the upstream fish passage, particularly for small-body-mass fish species. Using a combination of physical and numerical CFD modelling, design guidelines were developed for smooth box culverts without appurtenance, with a novel approach based upon the basic concepts: (a) the culvert design is optimised for fish passage for small to medium water discharges, and for flood capacity for larger discharges, and (b) low-velocity zones are provided along the wetted perimeter in the culvert barrel, and quantified in terms of a fraction of the wetted flow area where the local longitudinal velocity is less than a characteristic fish speed linked to swimming performances of targeted fish species. The approach relies upon an accurate physically-based knowledge of the entire velocity field in the culvert barrel, specifically the longitudinal velocity map, given that behavioural observations confirmed that fish prefer to swim upstream in low-velocity zones (LVZs) next to the walls and bottom corners. While the focus of the study is on the upstream passage of small-body-mass fish, typical of Australian native fish species, the approach and methodology are relevant to most box culvert structures.

DOI: https://doi.org/10.3850/38WC092019-0429

Year: 2019