Water Sensitive Urban Design ‘desperately needed’

Robyn says the large, tree-filled raingardens in Auckland’s Wynyard Quarter show how to absorb excess run-off water from impermeable surfaces. There are a myriad of ways to help create ‘sponge’ cities such as dual use of low-lying parks to hold runoff, roadside raingardens to reduce flow into guttering, trees beside roads, greenroofs, and reducing impermeable surfaces. Photo: Robyn Simcock, Landcare Research.

At the end of January, an “atmospheric river” deluged Auckland, causing wide-spread flooding and a State of Emergency in the region.

Although the rain was an unprecedented record setter, how has the city performed? When the water recedes, are there lessons to be learned and changes to be made in how we create our urban environments? Do our stormwater systems need revising in the face of a changing climate? Do we need to radically change our thinking about non-porous hard surfaces that force water into surface run-off? Should councils be mandating Water Sensitive Urban Design on all new developments and actively retrofitting existing infrastructure to try and prevent the events that occurred in Auckland from happening again?

A team of researchers supported by the Building Better Homes, Towns and Cities (BBHTC) National Science Challenge say we need to shift our thinking and start adopting Water Sensitive Urban Design (WSUD) now, as extreme events such as that in Auckland are likely to become more frequent.

Dr Robyn Simcock, an ecologist and soil scientist from Manaaki Whenua – Landcare Research, herself an Auckland resident, says the solutions for WSUD are there, but are currently viewed as being ‘nice to have’.

“WSUD, Green Infrastructure [GI], or Nature Based Solutions – the use of a network of natural systems involving soil and vegetation – is increasingly appreciated as fundamental to also achieving wellbeing as well as its primary role of floodplains and overland flow paths. It’s also a question of equity, Green Infrastructure is generally lowest in the most deprived areas and the flood risk is higher. One of the lessons to be learnt here is that we desperately need to soften our cities and other urban areas.”

Urban areas typically alter landscapes from permeable soils with plant cover that absorbs and transpires water, to a series of interconnected hard surfaces piped to streams that result in large quantities of storm-water runoff quickly overloading our waterways. In addition, this run-off is often polluted with metals, litter (including plastics), and sediment.

This run-off requires management, but the WSUD team says this isn’t just a matter of big gutters and large pipes piping the excess straight to waterways, but also about making good land-use decisions that facilitate safe and aesthetically pleasing urban lay-outs, which promote water re-use, water absorption, and enhance urban liveability and human wellbeing through resilient stormwater systems.

“International studies show benefits of GI are greatest where social deprivation is high – it’s a way to improve social equity and health. In the Aotearoa New Zealand context, this means paying attention to the outdoor landscapes to optimise liveability and expression of kaitiakitanga, rather than just to the building itself, followed by slapping down a thin skin of topsoil and ready-lawn, or worse plastic grass or concrete.”

Researcher Sue Ira, Director of Koru Environmental Consultants, says land use and development decisions are closely connected to the health and wellbeing of water, and the risks of water-related natural hazards to communities.

“Improving the integration of land use and water planning is essential and is fundamentally underpinned by a WSUD approach. Primary stormwater networks will always become overwhelmed during extreme rainfall events, but city planning needs to ensure that flood plains are kept free from development and that overland flow paths are protected so that flood waters can flow safely away from the city without causing risks to life, critical infrastructure, homes and businesses. Retrofitting green infrastructure in existing urban areas can also increase the resilience of the stormwater system during extreme events and assist with climate change adaptation,” says Sue.

Robyn says New Zealand may the best place in the world to implement WSUD, “Many areas have a temperate climate with frequent rain and year-round plant growth. WSUD has been available and used in a few places in New Zealand for more than 10 years, but barriers remain to its widespread adoption, and in many places its full benefits haven’t been realised – especially its community liveability benefits.”

The wellbeing benefits of Water Sensitive Urban Design and GI are summarised in a report, Assessing the Full Benefits of WSUD, the team has also developed the ‘More than Water’ Tool to help communities, designers, and funders compare the nature and extent of benefits of projects with and without Water Sensitive Urban Design.

The benefits report says that the assessments of the benefits of WSUD that focus solely on these water-related outcomes are incomplete in their scope. “WSUD has the potential to deliver a wide range of other environmental and social co-benefits, for instance: the preservation of natural soils; microclimate moderation; terrestrial habitat provision for native biodiversity; the provision of supplementary water supplies; better public safety; and improved health and wellbeing deriving from the use of green infrastructure.”

Researchers Troy Brockbank and Emily Afoa, who have investigated the alignment between te ao Māori and WSUD, say the principles of WSUD and intended outcomes are interwoven with the fabric of te ao Māori. “Rather than trying to integrate te ao Māori into WSUD, we should consider the different perspectives in parallel avoiding compartmentalising cultural values. Co-designing with mana whenua through the lens of te ao Māori, applied as a mainstream principle through the WSUD framework, will empower the desired social and environmental connections to create resilient and healthy communities.”

The BBHTC Water Sensitive Urban Design team was a collaboration in 2018/19 between Robyn Simcock, Manaaki Whenua – Landcare Research (plants and soils, WSUD maintenance); Jonathan Moores, NIWA (assessing environmental effects of WSUD); Sue Ira, Koru Environmental Consultants, (implementation and costing of WSUD); and Chris Batstone, Batstone Associates, (indirect benefits of WSUD).

Read more water and urban design research from the BBHTC Water Sensitive Urban Design team.