Can sponges cities save us from the next climate crisis?

The Sponge City concept originated in China in response to the growing frequency and intensity of urban flooding. Since the successful 2014 Suzhou pilot, the Chinese government has launched a nationwide program promoting the development of Sponge Cities. The concept has also been adopted by several cities in the US and Singapore.

Interestingly, in contrast to global trends, the Auckland mayor has controversially proposed cuts to climate and environmental programs.

Outdated stormwater infrastructure, proximity to the coast and low-lying areas make New Zealand cities vulnerable. Clearly evidenced by the widespread flooding, damage and disruption caused by recent summer storms.

Naturally occurring large green spaces, while beneficial, may not offer the absorbency or holding capacity required in more densely populated spaces. We need to employ site-specific supporting infrastructure, with media designed for its ‘sponginess’ or capacity to retain, detain and clean rainwater.

Different green infrastructure devices offer varying levels of ‘sponginess’:

·       Super sponge: Green Roofs, Rain Gardens, Bio swales, Wetlands

·       High sponge: Stormwater Tree Pits,Permeable paving, asphalt and concrete alternatives.

·       Moderate sponge: Tree Pits, Gardens,Parks, Golf Course

The efficacy of these devices was recently demonstrated in Auckland’s Wynyard Quarter and Hobsonville Point. Both areas where bioretention devices have been installed were resilient to unprecedented rain fall, while flooding was severe in neighbouring areas.

Extreme weather events are a sign of things to come. Auckland and other cities must explore ways to increase urban sponginess, promoting and prioritising the use of green infrastructure to improve overall sustainability and resilience. Taking our lead from the global community we could look to update our best-practice and council standards, mandate the use of green infrastructure in new developments, retrofit existing infrastructure to incorporate green elements, or incentivize private property owners to invest in green infrastructure.

Implementing Sponge Cities requires coordination and collaboration between agencies and stakeholders, investment in infrastructure, as well as changes to building codes and zoning regulations to promote the use of permeable surfaces and other green infrastructure.

As many North Islanders’ will attest, it is increasingly important for our cities to work together to increase resilience to flooding and other impacts of heavy rainfall and climate change. By promoting the development of Sponge Cities, and refreshing best-practice guidelines, we can create more sustainable, resilient, and liveable urban environments.