Aotearoa New Zealand’s current approach to urban design and flood management is falling short. The so-called ‘grey infrastructure’ (pipes and drains) is ageing and in many cases not coping with current requirements, much less up to the task ahead. Meanwhile, 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.

Could ‘sponge cities’ offer a solution? That approach aims to protect, enhance and sustainably manage water resources in urban environments by slowing the passage of stormwater. It involves cities working with water rather than against it. This can include building or restoring urban wetlands, ‘daylighting’ streams and creating space for urban waterways to flood safely – including by moving people and houses out of the way, for example. It also includes relatively new but effective ideas such as pocket parks and tiny urban forests.

Some potential solutions lie in the public domain, and some in the private. Using all the different types of spaces in our urban areas, including parks and school grounds, roads, industrial areas, homes and businesses, helps to spread the water load and the cost, and ensures a better outcome overall.

Adapting Aotearoa New Zealand’s cities and towns to a sponge cities model will be expensive. However, there is strong evidence that sponge city approaches provide a compelling cost-benefit ratio, both when compared with conventional stormwater management approaches, and especially when compared with taking no action to prepare for climate change.