Protecting Christchurch’s communities and nature through reimagined waterways
Integrating flood management, stormwater treatment and ecological restoration to protect communities and restore waterways
Photo courtesy of Christchurch City Council
As climate change increases flood risk, putting greater pressure on urban waterways, cities are challenged to rethink resilience. In Christchurch, New Zealand, the Canterbury earthquakes of 2010 and 2011 created a unique opportunity to reimagine the waterways, landscapes and communities along the Ōtākaro Avon River Corridor (OARC).
Through Christchurch City Council’s OARC Capacity and Conveyance Project, a vision was developed for how 1483-acres (600-hectare) of former red-zone land could evolve into a resilient river corridor. Jacobs provided consulting services to define an integrated scheme for flood management, stormwater treatment and ecological restoration, establishing the foundations for future design and construction.
Up to 5M
cubic feet (140,000 cubic meters) of urban runoff is expected to be treated every rainfall event
13 miles
(21 kilometers) of flood defenses
14
stormwater treatment facilities
From red zone to resilient landscape
At the heart of the OARC Capacity and Conveyance project was the opportunity to improve water quality and restore the health of the river corridor. This reflects the vital role healthy waterways play in Te Mana o te Wai — the Māori concept that recognizes the fundamental importance of water to life, as well as mahinga kai — traditional Māori food-gathering practices and resources, ecosystem health, recreation and community wellbeing.
Approximately one-third of the 6425-acre (2,600-hectare) Ōtākaro Avon catchment drains through the river corridor, creating a significant opportunity to improve the health of local waterways.
Reimagining stormwater infrastructure
The project involves retrofitting the stormwater system within a constrained urban environment.
Drawing on our experience in flood hydrology, climate science, stormwater treatment, hydraulics, pumping systems and civil engineering, we worked with Christchurch City Council to assess and develop options for an ecology-led river corridor. Using advanced hydraulic modeling, feasibility assessment and integrated planning, we developed a framework that brought together flood management, stormwater treatment, climate adaptation and ecological restoration. This framework identified the most effective locations for treatment systems and pumping infrastructure, establishing a pathway for the future delivery of ~13. miles (over 21 kilometers) of flood management infrastructure, several stormwater treatment facilities, pump stations and an extensive stormwater conveyance network.
We also challenged traditional gravity-driven stormwater design approaches by introducing an adaptive hybrid system and shifting planning from individual assets to a catchment-wide perspective.
Optimizing stormwater outcomes through a treatment hierarchy
Jacobs developed a stormwater treatment hierarchy for Christchurch City Council, creating a structured decision-making framework that prioritized the most effective stormwater treatment solutions — first flush basins and constructed wetlands — while providing flexibility to respond to varying site conditions through more compact flow-based filtration devices.
The proposed system is expected to treat approximately 5 million cubic feet (140,000 cubic meters) of urban runoff during each rainfall event and remove contaminants such as sediment, heavy metals, nutrients, hydrocarbons, microbial contaminants and other pollutants before they reach the river.
37 acres
(15 hectares) of land expected to be returned for community use
40 acres
(16 hectares) additional room for the river through the realignment of flood defenses
$436M
(770 million NZD) estimated reduction in future flood damage costs (by 2060)
*Taonga is the māori concept that recognizes the intrinsic and cultural value of an item, environment, resource or living being. It is commonly translated as "treasure."
Delivering environmental and community benefits
This stormwater treatment hierarchy enabled Christchurch City Council to select the most appropriate treatment solution for each location while maintaining consistent water quality outcomes across the corridor. By streamlining decision-making and integrating stormwater treatment with flood management, ecological restoration and landscape design, the framework improved planning efficiency and maximized environmental and community value.
As a result, approximately 37 acres (15 hectares) of land previously allocated for stormwater treatment is expected to be returned to the community, and an additional 40 acres (16 hectares) of room to be created for the river through the realignment of flood defenses.
Restoring the environment while building stormwater resilience
Our team tested how the system would perform under a range of future scenarios, including sea level rise and vertical land movement. Rather than planning for a single end state, the project established a flexible pathway for infrastructure delivery, allowing investments to be phased as environmental conditions evolve and prioritized where they deliver the greatest value.
By restoring natural processes while planning for uncertainty, the project is creating a healthier river corridor with improved water quality, enhanced habitats and greater resilience to climate impacts. It demonstrates how cities can use nature-led, adaptive solutions to improve biodiversity, create vibrant community spaces and strengthen long-term environmental resilience.
Building resilience and creating community value
Through the project, a landscape once defined by disaster has been provided with a clear vision for retrofitting nature-led stormwater infrastructure in an urban environment, laying the foundation for improvements in water quality, habitat restoration, flood resilience and community amenity, while helping safeguard more than 2,000 properties as the wider scheme is delivered.
