Sponge Cities: "What we need next is a change of mindsets"
Heather Wilkins, WSP Principal Landscape Architect, describes being involved with the research report Sponge Cities: Can they help us survive more intense rainfall? as an affirming experience.
The report won the Research and Communication category of the 2024 Resene NZILA Awards in May. It was authored by Kali Mercier, WSP Fellow and Deputy Director of the Helen Clark Foundation, and published by WSP as part of its ongoing partnership with the Foundation.
Excerpts from the Sponge Cities report. See a synopsis and review below.
“I was really pleased and proud to have landscape architecture featured by Kali as one of the inputs to her wide-ranging report,” says Heather.
“Being able to contribute information on the role that indigenous vegetation can play in flood mitigation was an opportunity to highlight just how effective green infrastructure can be.
“Indigenous planting can be both a resilient and cost-efficient way of bridging the gap between our built and natural environments. As I wrote in the report, while we can’t convert all of the impervious surfaces of our towns and cities into restored forests, we can incorporate more natural systems and processes into our urban areas”.
Heather’s contribution to the Sponge Cities report included practical advice on taking a cue from the native plants that are already thriving in an area and how they function in the water cycle. She also urged urban planners and landscape architects to work closely with the nursery industry to keep genetic plant material diverse, and with the science community to identify and use resilient local plant varieties that are “better able to take the knocks”.
Now into her third year at WSP, Heather originally trained in Fashion Design and worked in that field for a decade before making landscape architecture her ‘second career’ after completing studies at Unitec.
She counts pioneering female landscape architects like Kathryn Gustafson, also a former fashion designer, as points of inspiration, and also acknowledges the influence of landscape leaders she has worked with in Aotearoa for growing her knowledge of water sensitive design and ecological restoration.
Calling herself a long-time Westie (West Aucklander), Heather has always had a strong passion and respect for water and sites of natural splendour in Aotearoa New Zealand. “We didn’t know how spoilt we were growing up with access to magical places such as Whatipū Beach, which I still marvel at”.
Heather says she is encouraged that the anticipation, scale and pace of necessary responses to climate change has picked up in Tāmaki Makaurau Auckland.
“Set against all of the natural vulnerabilities that the places we live and work in are exposed to, it’s more and more noticeable that the focus of our work is shifting to landscape resilience and recovery.
“In the face of the climate challenges being presented by the 21st century, I’m especially heartened by the number of projects that are helping to create better conditions for biodiversity, with all the benefits that flow from that.
“It’s affirming to know that the approach on major projects being taken is more and more multidisciplinary and that the voice of landscape architects around things like the importance of long-term decision-making is being heard. I think that is a sign of the tenacity that is needed as well as of a maturing regard for, and within, our profession.
“What we need next is a change of mindsets from all decision-makers to do more to embrace nature-based solutions. That needs to be coupled with better planning mechanisms and a better acceptance of the economic case and cost-saving that is possible from applying blue-green models to future developments – regionally and nationally”.
Heather: “This is stuff that I talk about all of the time with my 9-year-old daughter. She’s all over it, and it’s encouraging that environmental topics and issues are a strong part of the school curriculum. It makes our adventures in places like Whatipū Beach all the more interesting”.
SPONGE CITIES: A BRIEF SYNOPSIS AND REVIEW
Written for LAA by guest editor Stephen Olsen
Artwork credit: Alex Scott Studio - see a readable full-scale at Helen Clark Foundation
After around 100 pages of intense reading, the Sponge Cities report drives home its conclusion that the time for amping up nature-based sponge city approaches, as a compellingly necessary response to extreme climate events - and not in a piecemeal fashion - is now.
The report sits well withing a reframing of flood mitigation and climate resilience away from a response to threat and towards being an enabler for urban transformation.
Sponge Cities is a hopeful report and Kali Mercier, WSP Fellow and Deputy Director of the Helen Clark Foundation, is upbeat in writing that the vision that emerged from putting the report together wasn’t all doom and gloom.
Instead it brought to light a value proposition of “green and blue cities that can both survive, and thrive” – of a model for cities “that are more beautiful, less polluted, and more hospitable, both to humans and wildlife”.
If acted on as envisioned, this report would see cities and towns strategically retrofitted to become sponge cities, in a combination of large-scale intervention with small-scale infrastructure and with high confidence that urban density and future-proofing for floods can be compatible.
As asserted in the report “even small, incremental steps to make urban areas spongier can have a swift impact”.
If the logic in this report is followed, approaches that are evident already in New Zealand would become more mainstream, and more of a “first got-to for stormwater management”. Costings would be centered towards full life cycles and other wider benefits to balance out the short-term thinking of most decision-making criteria.
To quote Dr Konjian Yu, the progenitor of the sponge cities concept in China, the days of being fixated on “single-minded, industrial technology-based solutions” need to give way to “nature-based and symbiotic solutions”.
The vulnerability of cities and towns to increases in both the frequency and intensity of extreme rainfall events is undeniable, and this report puts the case that the expense of failing to prepare without including more sponge city approaches will be “considerably more expensive”.
Retrofitting – incremental or otherwise - would also see more action taken arounding making existing neighbourhoods, roads and private land more absorbent. Approaches that focus equally across the whole-city level and across new developments and private residences, would be both required and incentivised to optimise their likely success and overall affordability.
The warning is plainly put that “in many places there will be no real alternative as the cost of enhancing the capacity of our pipes to deal with increasing water load becomes ever more prohibitive”.
There is, in the executive summary to Sponge Cities, a ‘calling out’ of current flood management and urban design approaches for falling short, resulting in a net negative for the environment.
Existing, ageing ‘grey infrastructure’ (pipes and drains) is “not coping with current requirements, much less (being) up to the task ahead”. Even though much of it will inevitably be retained, the point is made that it is an infrastructure that in the bigger picture will only “prove to be inadequate again and again”.
On top of that our “urban areas have become less green in recent years, and therefore less able to absorb the large amounts of rain with which they have to deal, now and in the future”.
At the city and catchment level, the argument is that councils should be doing more to plan for and provide public green spaces as they do with other infrastructure.
A staggering reduction in the number of urban trees over the past decade or more is also raised as a massive concern. Its another measure on which we appear to be going backwards not forwards. All at a time too when managing floods, protecting biodiversity and sequestering carbon is more and more important.
Although it tends to be implemented at the level of the individual development rather than city or catchment level, water sensitive urban design (WSUD) is given attention for its close alignment to sponge city approaches.
Slowing the passage of stormwater is the essence of a sponge city approach, with cities pivoting to “work with water rather than against it”. This report is an in-depth catalogue of ways to achieve that.
Chapter Six titled ‘Making It Happen’, should alone be compulsory reading for politicians of all stripes, policy setters, decision makers and all communities of related practice and interest. It’s where the priorities are identified, namely:
Identifying areas at the greatest risk
Funding sponge cities upfront to save money later
Rising above silos and other structural barriers
Encouraging community involvement to achieve more equitable outcomes
Improving access to good information
Investing in research and development
The practical options that are expanded on throughout the Sponge Cities report include “building or restoring urban wetlands, ‘daylighting’ streams and creating space for urban waterways to flood safetly” as well as “relatively new but effective ideas such as pocket parks and tiny urban forests”.
Chapter by chapter further interventions and variations are acknowledged and added to an almost overwhelming list if you string them together: Amendments to conditions for housing developments, application of covenants, betterment charges or hypothecated rates, bioretention basins and devices, better connected urban water systems, bioswales, development fee caps, extending pluvial floodplains, filter strips, flood plain restoration, green roofs and walls, ‘green score’ accreditations or certifications, higher compliance standards, ‘hydraulic neutrality’, infiltration trenches, land value capture, linear parks, local tree-planting with ‘treebates’ (rates rebates), mini-wetlands, overland flow paths, permeable paving/ asphalt/ concrete, planted buffer zones, pond creation, protecting riparian vegetation, rain gardens, rain tanks, rehabilitating rivers and streams, retaining and reusing rain water, ‘sacrificial storage areas’, soakaways, stop banks, sustainable drainage systems, tree pits, tree retention, underground detention tanks, unsealing pavements and car parks, water conservation, wet proofing techniques for houses.
The cumulative list of benefits is just as impressive from temperature regulation to biodiversity enhancements and from noise reduction to air purification.
By applying high aspirations, as urged in the report, a sponge city model would be considered and evaluated as much for its ability to accelerate ecological restoration as for its ability to mitigate flood risks. And to do so to flourishing levels, not just to a minimum baseline. It would be guided and enabled at all points too by mātauranga Māori.
Notes of caution and critiques are also abundant in the report. For instance the caution that “specific and comprehensive responses to increasing flood risks – and the importance of nature-based solutions to strengthen this resilience – have not yet been woven systematially into Aotearoa New Zealand’s policy frameworks”.
Too often, rather that full embracing the necessity of making space for water, flood plains still continue to be built on. It is noted that designing “bigger and better” grey infrastructure may be the only solution for flood prone areas that must be protected at all costs.
A key point made in Sponge Cities is that there are plenty of emerging national and international examples to draw upon for inspiration and ideas for all solutions, as recently witnessed at both the 2024 IFLA Congress and the 2024 World Green Infrastructure Congress.
Further reading and links:
Embracing sponge cities: A nature-based approach to urban climate change adaptation in Aotearoa New Zealand [PDF] - Liam Foster and Kali Mercier (Hynds Paper of the Year 2024)
NZ cities need to become ‘spongier’ - Te Herenga Waka Victoria University
The ‘More Than Water’ WSUD Assessment Tool - Building Better Homes, Towns and Cities