Ōtara Fish Passage Barrier Remediation

Our freshwater streams are home to the migratory fish that move between these waterways and the open ocean.

The Ōtara Creek, a tributary of the Tāmaki River, provides essential freshwater habitats for these native migratory fish; however, the intersection of East Tāmaki Road and the Creek posed a barrier to migration for native swimming species. The twin concrete box culverts at this site included a vertical drop at its downstream end, obstructing fish passage.

Healthy Waters engaged Morphum Environmental to address this issue and develop a cost-effective, easily constructable and ecologically conscious solution to improve fish passage. By designing a fish ramp, Morphum helped to inform the improvement of upstream habitats of Ōtara Creek, enabling native fish species to complete their migratory patterns.

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Solution Design

Morphum began by conducting detailed assessments  and identified the culvert at East Tāmaki Road as a priority for remediation due to the extents of upstream habitat, its proximity to the coast  and the feasibility of a cost-effective solution.

We developed a grouted fish ramp design tailored to the site’s specific needs. The designed focused on using the culvert on the true left bank of the stream as the dedicated fish passage channel by using steel angle baffles to direct base flow toward the ramp design. The ramp consists of a meandering low flow channel between grouted rocks to provide a range of complex flows, a full wetted width and resting areas that mimic what fish would encounter and navigate in nature.

This solution was both cost-effective and ecologically sensitive, minimising construction impact while increasing fish passage potential. The design was informed by a series of desktop assessments, field studies, and client consultations to ensure practical and sustainable outcomes.

Our multidisciplinary team collaborated closely with Auckland Council and other stakeholders. Following the concept design phase, the plan was finalised, before construction was completed by Glasgow Contractors.

The project achieved its primary goal: enhancing fish migration pathways and reconnecting approximately two kilometres of upstream habitat in Ōtara Creek. This initiative will contribute to the long-term health of the local aquatic ecosystem, supporting the growth of native fish populations and promoting biodiversity.

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Impact

This improved culvert with accessibility for fish passage fosters a healthier aquatic ecosystem, which enhances the natural beauty and ecological value of the area for our native species and our communities. Morphum received some awesome feedback from the local community education coordinator and her students who found a torrent fish upstream of the fish passage. This was the first time they had ever seen one.

With more projects based on the combined disciplines of engineering and science, we can design areas to mimic the natural world and benefit every group of stakeholders.

Let’s co-create more thriving ecosystems together.