Making space for water to safely flow through Tāmaki Makaurau neighbourhoods without causing risk to people and property has become more urgent following extreme weather events.
One way to help manage excess water and flooding is by creating more ‘blue-green networks.’
A blue-green network is an open stream created in parkland to carry rainwater during a storm to keep it away from neighbouring properties. During dry weather, the park is there for the community to enjoy. The streams are designed to fill and overflow – safely moving water away from buildings through natural green pathways. Additional vegetation planted on the banks helps to naturally absorb water.
How are blue-green networks created?
To create a blue-green network, we may need to bring streams back to their natural state, increase planting, widen the stream, and deepen some areas to allow more water to flow.
In some urban areas, homes may be in the way of a proposed stream flow. Many of these properties have been affected by flooding before or are at high-risk of flooding because they are built on or near flood plains. Deciding to remove these homes is a critical step, as in many cases it's not safe for homes to remain here due to their vulnerability to flooding. In these cases, homes need to be removed or relocated to non-flood prone areas, and the land repurposed for flood management.
There are existing examples of these networks in Auckland. Are they effective and are they a good benchmark for more?
Greenslade Reserve in Northcote is a great example of what can be achieved in flood-prone parts of the city. The reserve was designed to manage heavy rainfall so that downstream flooding stays mostly within the street network and damage to neighbouring properties is minimised. It does this by providing more space to hold water and by slowing down the water flow.
The design included bringing the Awataha Stream to the surface so stormwater can move along the stream bed, instead of through private property. More water can flow through an open channel than through a traditional stormwater pipe.
It is important to note that nothing can prevent all flooding. Even though blue-green networks are designed to carry large amounts of water, they can and will still flood in extreme weather events.
Why blue-green networks are good for our communities
As well as reducing flood risk to homes and communities, blue-green networks also benefit the wider community and society. Reducing flood risk in this way supports clusters of homes, communities, and neighbourhoods.
As we develop greener networks, we also see improved water quality and biodiversity. By bringing back more of the natural environment, we’re encouraging larger numbers of fish, eel, bird, and insect life. Plus, there are more trees and green recreational spaces for people to enjoy in dry weather, helping to reverse tree cover loss and increase open spaces.
Are blue-green networks the answer to Auckland’s flood risk areas?
Blue-green networks are a great initiative and one that has already been successful, but they are only one part of a wider plan for managing water.
Auckland Council’s Making Space for Water programme is a six-year flood mitigation scheme. It identifies actions such as increasing stormwater network maintenance, improving flood intelligence tools and fostering community-led resilience to flooding across the region.
Auckland Council’s Healthy Waters Head of Sustainable Outcomes, Tom Mansell advocates for blue-green networks in Auckland.
“We have been trying to constrain and contain stormwater for the last 60-70 years. However, it has become clear that to manage stormwater effectively, we must work with nature, instead of against it,” Mr Mansell said.
“We’re putting streams back in low lying flood plains and adding vegetation to slow down the flow,” he adds.
We know that some of our existing infrastructure is based on old weather patterns and is now not fit for purpose. By creating more blue-green networks as part of the Making Space for Water initiative, we’re replicating nature’s solutions to help reduce damage to properties in some of Auckland’s high flood risk areas.
Learn more about blue-green networks on the council website.
