38 | DEVELOPMENT Waikato Regional Council T T Karen Phelps Managing floods, protecting wildlife Waikato Regional Council Integrated Catchment Management director, Greg Ryan, says this consolidation not only reduces maintenance costs, but also introduces innovative engineering solutions to address multiple environmental challenges. A new flood-management project in Waikato has demonstrated how infrastructure upgrades can simultaneously enhance flood protection, improve environmental outcomes and create new wildlife habitats through collaborative partnerships. The three-year asset rationalisation project near the Piako River mouth, completed by Waikato Regional Council, has transformed an ageing flood-protection system into a modern, environmentally conscious infrastructure that will serve the region for the next century. “When the Piako River flood-protection scheme was built, the focus was solely on enabling farming,” says Greg Ryan, Integrated Catchment Management director. “At that time, the environmental issues we’re seeing now, such as high sediment loads in the waterways, habitat loss and obstructions to fish passage, weren’t as well understood, nor were they even considered as being a possible impact on our environment.” The $8.86 million project, which had significant funding from the Government’s Climate Resilience Programme (administered by Kānoa - Regional Economic Development and Commercial Services), has replaced three ageing floodgates with a single modern structure. Other funders included the New Zealand Lottery Commission’s Environment and Heritage Fund and Hauraki District Council to support drain changes. Greg says this consolidation not only reduces maintenance costs, but also introduces innovative engineering solutions to address multiple environmental challenges. He says the new infrastructure provides flood protection for 829 hectares of land, much of which lies below sea level, ensuring the continued viability of productive farmland while addressing modern environmental concerns. This balance between agricultural needs and environmental protection represents a new paradigm in infrastructure development. Project manager Grant Ockleston describes the complex considerations that shaped the design: “Every site is unique, so the concept is specific to the site. We engineered multiple ways of resolving the problems, so that we can be confident they will no longer be an issue.” A key innovation is the strategic placement of the new floodgate, set back 69 metres from the river to accommodate channel migration. This design includes a naturally angled discharge channel to prevent erosion, and a buffer zone with riparian planting to protect the infrastructure from the encroaching river channel. The project introduces several environmental improvements, including a 24/7 flushing mechanism that allows fish passage while preventing sediment build-up. A specially designed U-shaped pond captures more than 90% of sediment before water enters the river, simultaneously providing a refuge for native eels during drought conditions. The drainage efficiency has seen a dramatic improvement, with the catchment now able to clear runoff much faster and well within the agreed performance standard. The system’s design also anticipates future needs, with the storage pond capable of supporting a pump station should one be required. Perhaps most significantly, the project has created a 10-hectare wetland habitat for resident and migratory shorebirds, including a 5000sqm island roost. This habitat addresses the need for safe roosting areas, as mangrove encroachment in the Firth of Thames has reduced natural shorebird habitats, says Greg. “The wetland’s tidal control structure allows regular inundation while preventing mangrove colonisation through an innovative floating boom and submerged screen system. This careful balance maintains the habitat’s suitability for both birds and marine life.” Waikato Regional Council chair Pamela Storey emphasises the collaborative nature of the project’s success: “It has been a true partnership, with funding from central government, the New Zealand Lottery Commission, and Hauraki District Council. The development planning for the wetland habitat involved input from Pūkorokoro Miranda Shorebird Centre, iwi and landowners.” The project also includes recreational and educational aspects. A bird hide with informational panels has been installed adjacent to the Hauraki Rail Trail, allowing cyclists and visitors to learn about and observe the shorebirds in their new habitat. Michelle Paki, director Māori at Kānoa, highlights the broader implications of the project: “The establishment of the wetland habitat alongside upgrades to infrastructure is a marriage of climate resilience and environmental protection. The positive impact of this project will be evident well into the future.” River, Stormwater & Coastal Hydraulics | Onsite Wastewater Design Engineers specialising in hydraulic & hydrological modelling BARNETT & MACMURRAY LTD +64 3 434 8612 | www.riversandfloods.co.nz Your Partner in Project Success. Supporting You. Leading Progress. Seven Rivers is a leading project management company that collaborates with government agencies, large private clients, and community groups to deliver exceptional projects across New Zealand. Specialising in everything from essential infrastructure to airport rebuilds and community initiatives, we manage every aspect of the project lifecycle to ensure successful outcomes and lasting impact. 0800 7 RIVERS enquires@sevenrivers.co.nz www.sevenrivers.co.nz
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