How full-height sidewall baffles affect box culvert capacity: balancing fish passage and discharge requirements

ABSTRACT Low-level river crossings and culverts deliver valuable transportation and hydraulic control services to the society, but have negative impacts in terms of upstream fish passage. Recently, full-height sidewall baffles have been imposed in north-eastern Australia to assist upstream passage of small-bodied fish in box culverts, although the impact on the culvert discharge capacity was ignored. Detailed physical modelling was conducted under controlled flow conditions in a near-full-scale culvert barrel channel, equipped with such full-height sidewall baffles. The results provide a quantitative assessment of the impact of full-height sidewall baffles on the discharge capacity of box culverts. Applications were developed for single- and multi-cell box culverts, and practical implications are discussed.