Abstract | Culverts - implications for aquatic fauna

Road culverts and piped sections may be an essential part of road and infrastructure projects when crossing waterways. But what are the implications for the aquatic fauna that reside in the streams and rivers to be piped?

There is a wealth of literature and empirical evidence to indicate that road culverts can pose significant barriers to the movement of freshwater fishes. Much research has been conducted to determine maximum culvert slopes and barrel velocities for freshwater fishes with varying climbing and swimming abilities, but there remains a number of gaps in our knowledge on how waterway crossings should be designed and constructed to avoid creating barriers to freshwater fishes and stream invertebrates. Moreover, culverts are more commonly being required to be sufficient to take 1-in-100 year floods. Even some very small waterways, with very low baseflows, are required to have extremely large culverts with extensive rip rap and armouring at the inlet and outlets. These together can sever surface flows of these small waterways and create significant barriers to dispersal of fauna.

This presentation will provide some examples of design and construction of road culverts from recent transport recovery projects in New Zealand, the challenges faced during construction to ensure the passage of fauna was not impeded, and novel ways to remediate barriers to the passage of aquatic fauna during the construction and operation of new structures.

Bio | Tanya Blakely

Tanya Blakely is a consultant ecologist with Boffa Miskell, in Christchurch, New Zealand. She is an expert freshwater ecologist, bringing excellent understanding of the range of pressures on, and drivers of, aquatic ecosystem health. Tanya has worked on numerous multi-disciplinary and major infrastructure projects, including Roads of National Significance with NZTA where freshwater restoration and loss of, or modification to, freshwater habitat were key challenges. Her recent involvement as Project Freshwater Ecologist for road and recovery projects in New Zealand, such as the Western Belfast Bypass and North Canterbury Transport Infrastructure Recovery, has provided exciting opportunities to work with designers, engineers, and construction teams to find ways to minimise the effects of transport routes on freshwater ecology.

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