69 Green infrastructure and resilience

Guest contribution Alethea Goddard

Green Infrastructure and SuDS are becoming the new norm for surface water management in the UK, particularly thanks to the long-awaited (although still waiting) implementation of Schedule 3 of the Flood and Water Management Act. ?Other pieces of legislation and local policy further the expectations for the delivery of Green Infrastructure, such as the requirement for Biodiversity Net Gain. ?I (Alethea) personally welcome the inclusion of more Green Infrastructure and think it offers a much more adaptable and resilient solution to its grey counterparts. ?That is not to negate the challenges to delivery: contaminated land, high groundwater, impermeable soil, and boundary constraints etc. ?Although solutions also exist to overcome this: lining, alternative outfalls, raised components and planning from the outset of development.

Considering the grey vs green debate further, Green Infrastructure offers a variety of wider benefits a culvert or storage tank could never achieve. ?Firstly, within the UK we are still hesitant to consider the water quality improvements that can be achieved with Green Infrastructure, however, across the ‘pond’ (pun intended), our American counterparts primarily use Green Infrastructure for its water quality benefits, citing the cleaning properties of the SuDS substrate. ?Alongside water quality and quantity management benefits, Green Infrastructure has gained considerable traction for its potential to adapt to and mitigate the impacts of the climate crisis, such as reducing the urban heat island effect, carbon capture, replenishing groundwater, and protecting biodiversity. ?It also provides benefits to its local communities such as reducing noise, reducing energy demands of buildings, and providing healthy Place. ?However, all these extra benefits rely on the plants themselves that exist within the Green Infrastructure component, something that we lack the full understanding of.

My PhD Research

The big question I’m asking in my PhD is how resilient Green Infrastructure is to survive the very challenges it is designed to solve. ?How well can the vegetation, and system survive climatic extremes? ?Are we designing components that integrate well into their environment to prevent failure? ?How does the system interact with its local environment? ?Through my PhD research I am seeking to examine the interdependency and complex relationship between Green Infrastructure and Resilience, considering both how we can better build resilience into Green Infrastructure but how we can ensure that Green Infrastructure is contributing to our resilience to manage urban challenges. ?In essence, I hope my research can help our cities have thriving vegetation: green infrastructure that stays green.

To address these questions, I’m using a multi-method approach to consider resilience through a series of both vegetated experiments and a case-study comparison of Green Infrastructure delivery in Philadelphia, USA compared to Newcastle-upon-Tyne, UK.?

Putting the green into Green Infrastructure

Currently, our knowledge of which plants to use in Green Infrastructure comes from a variety of horticultural experts, but we lack the science to support their suitability for SuDS components. ??My experiments at the UKCRIC National Green Infrastructure Facility, Newcastle University, compare three Green Infrastructure planting regimes: amenity grassland, typical raingarden planting, and edible herbs (to represent urban agriculture). ?At a pilot-scale I’m putting the plants through their paces; examining their physiological responses to artificial weather extremes. ?At a street-scale the planting regimes exist under natural weather conditions within individual fully functioning raingardens, where I examine the soil-plant-atmosphere interactions, to compare performance.

Currently, status quo works best although some individual species perform better than others, but grass contributes little to water storage and is the least resilient to drought conditions.

Resilient decisions and design

Moving beyond the resilience of the vegetation itself, my work examines the resilience within decision-making and governance of Green Infrastructure. Newcastle-upon-Tyne and Philadelphia have very similar water management challenges, primarily reducing the amount of Combined Sewer Overflows. ?Each city has taken a different approach, with Philadelphia implementing a pioneering Green City, Clean Waters plan, a 25-year programme to green nearly 10,000 acres. ?Whereas Newcastle have opted for a more blended approach, retrofitting a series of above and below ground storage options within the city.

By interviewing a variety of those involved in Green Infrastructure delivery: from government officials to those who carry out maintenance, I’ve been able to understand the successes and challenges to the Green City, Clean Waters plan. Their biggest success is an over-performance of the features they’ve delivered and their clever initiatives for job creation in maintenance, a cost which was built into the plan from the outset. ?Their biggest challenge: vegetation. Vegetative death is frequent and related to different issues, such as: lack of investment, salt intolerance, incorrect planting, not supporting the establishment period.?

Resilience

Our urban spaces are facing increasing challenges: population growth, pollution, and a biodiversity and climate crisis, innovative solutions are needed to help manage these. ?Green Infrastructure can provide some solutions but only if designed and delivered thoughtfully. ?Caution needs to be taken in a ‘one-size (or SuDS) fits all’ approach of rolling out the same kind of feature repeatedly, as this will most likely lead to failure, this approach has lent itself to some of the issues in Philadelphia. ?Instead, each component needs to be individual and create a network of functioning and resilient Green Infrastructure. ?Lastly, it’s time to move away from grass and the humble lawn and move towards careful selection of tolerant vegetation. ?I implore all drainage engineers to be a little more green-fingered.