Why we need to integrate green and grey infrastructure in our towns and cities. By Shaun Jones.
Without the constraint of cost, the multiple priorities juggled by our cities’ decision-makers would be easier to manage. But cost is often the biggest constraint, and as the government, local councils and business deliver capital infrastructure, the ever- growing demands on revenue are coming under scrutiny. Given that each dollar comes from ratepayers’ pockets, ensuring a positive return on investment is essential. Traditionally, this has meant focusing on the efficiency gains of grey infrastructure such as the initial investment, hydraulics and durability.
Yet the concept of project efficiency becomes muddled when factors such as resilience, costs over the project’s entire lifespan and design integration are considered. Arguably, the attention paid to cost becomes a cost in itself.
When design and innovation is limited by this framework, an opportunity to integrate the benefits of green infrastructure is lost.
By balancing grey and green infrastructure we can create spaces and places that enhance our built, natural and social environments, ensuring they are inherently resilient and sustainable.
By integrating green infrastructure approaches into planning controls, we reduce combined sewer overflow (CSO) volumes, remove heavy metals and other contaminants, reduce heat island effects and improve urban engineering and landscape design to create liveable cities.
Auckland Council is working towards this integrated approach on projects such as Te Auaunga Awa – Walmsley and Underwood Reserves Project, which is seeing the restoration of an area also known as Oakley Creek.
Here, road bridges are being re-built and heavy civils are being utilised to provide flood protection to hundreds of homes, and significant planning has gone into ensuring this grey infrastructure is integrated with its green counterpart.
The result is that while the traditional infrastructure needs have been met, there’s an added social and environmental payoff; communities can gather at the awa and water quality objectives can be met.
The cost of achieving these wider benefits is marginal compared to the cost required to meet the minimum project objective of flood management. What could be considered as competing priorities are now integrated with good effect.
The awa project proves that thinking about our projects with holistic and multiple outcomes can achieve cost- effective solutions that engage and satisfy a range of key stakeholders.
Competing priorities in planning for the future of our cities will always be at the heart of this issue. Getting the right balance is tricky when prioritising investment on outcomes like growth and affordable housing versus community health and cleaning up our waterways.
Strategic decisions that direct local government over long periods of time should be the cornerstone for prioritisation with checks and balances in a local context.
The National Policy Statement for Freshwater Management (NPSFM) is an example of this.
Although best practice is moving towards the integration of green and grey infrastructure, a transformational and strategic shift in mindset will be required to effect a long-term change.
The objectives of the NPSFM imply a step-change away from current approaches where water quality is considered but easily de-prioritised in the face of competing objectives such as flood control, yield of residential units or other outcomes that generate immediate economic benefits.
To achieve these wider objectives in urban environments, councils and communities will need to make challenging decisions that balance equally important objectives such as housing supply and the health of our rivers and harbours.
While investments in grey infrastructure will remain essential on projects, the changing needs of cities and their citizens will force integrated design solutions to become the norm. Understanding and managing the inherent challenges will be critically important in order to realise the real and long-term benefits.
Proof of this approach can be found in New York City, where billions of dollars have been invested to minimise sewer overflows into their receiving environment.
The scheme found that about 80 percent of its objective – a harbour that is cleaner than it has been in the past 100 years – could be achieved with grey infrastructure. However, New York has reached a point where achieving further reduction in contaminants entering the receiving environment through conventional infrastructure could only be achieved through excessively, and disproportionately, high costs.
As a result, a green infrastructure plan was developed which combines the value gained through traditional infrastructure with the benefits of green infrastructure.
Back home at the Te Auaunga Awa – Walmsley and Underwood Reserves Project, the careful integration of green and grey infrastructure is proving seamless. The outcome will be a merger of grey and green infrastructure enabling a community space.
At this river, water is valued and the environment is given significance – alongside the steel and concrete. But the economic benefits of the project have also been maintained in the form of flood protection of hundreds of properties and the enabling of future growth for hundreds more.
Both green and grey infrastructure have a place in our modern cities. Despite the evidence supporting the efficacy and co-benefits of incorporating green infrastructure, large-scale implementation is yet to be consistently incorporated.
When a balance is achieved, we can transform the cities and places in which we live. By applying innovative engineering and integrated design, we can move towards efficient, environmentally- sustainable, and sensitive places for our communities – a future our children’s children will value.
• Shaun Jones is a water and urban development specialist at AECOM. He would like to acknowledge the contribution of his colleague and principal consultant – environment, James Hughes.
This article was first published in the June 2015 issue of NZ Local Government Magazine.