The Times Australia
The Times World News

.

Creating ‘sponge cities’ to cope with more rainfall needn't cost billions – but NZ has to start now

  • Written by Timothy Welch, Senior Lecturer in Urban Planning, University of Auckland
Creating ‘sponge cities’ to cope with more rainfall needn't cost billions – but NZ has to start now

Tune into news from about any part of the planet, and there will likely be a headline about extreme weather. While these stories will be specific to the location, they all tend to include the amplifying effects of climate change.

This includes the wildfire devastation[1] on the island of Maui in Hawaii, where rising temperatures have dried vegetation and made the risk that much greater[2]. In Italy, summer temperatures hit an all-time high one week, followed by massive hail storms and flooding[3] the next.

Flooding in Slovenia[4] recently left three people dead and caused an estimated €500 million in damage. At the same time, rainfall in Beijing[5] has exceeded a 140-year record, causing wide-scale flooding and leaving 21 dead.

These northern hemisphere summer events mirror what happened last summer in Auckland, classified as a one-in-200-year event[6], and elsewhere in the North Island. So far this year, rainfall at Auckland Airport has surpassed all records dating back to 1964.

Given more rainfall is one of the likeliest symptoms of a changing climate, the new report from the Helen Clark Foundation and WSP[7] – Sponge Cities: Can they help us survive more intense rainfall?[8] – is a timely (and sobering) reminder of the urgency of the challenge.

NIWA, CC BY-NC-ND[9][10] Pipe dreams The “sponge city[11]” concept is gaining traction as a way to mitigate extreme weather, save lives and even make cities more pleasant places to live. This is particularly important when existing urban stormwater infrastructure is often already ageing and inadequate. Auckland has even been cutting spending on critical stormwater repairs[12] for at least the past two years. Read more: Auckland floods: even stormwater reform won’t be enough – we need a ‘sponge city’ to avoid future disasters[13] Politically at least, this isn’t surprising. Stormwater infrastructure, as it is currently built and planned, is costly to develop and maintain. As the Helen Clark Foundation report makes clear, New Zealand’s pipes simply “were not designed for the huge volumes they will have to manage with rising seas and increasing extreme rainfall events”. The country’s current combined stormwater infrastructure involves a 17,000 kilometre pipe network – enough to span the length of the country ten times. The cost of upgrading the entire water system, which encompasses stormwater, could reach NZ$180 billion. This contrasts starkly with the $1.5 billion councils now spend annually on water pipes. The report makes clear that implementing sponge city principles won’t wholly solve flooding, but it can significantly reduce flood risks. Trees and green spaces The real bonus, though, lies in the potential for sponge city design to reduce dependence on expensive and high-maintenance infrastructure. There are already examples in Auckland’s Hobsonville Point and Northcote. Both communities have incorporated green infrastructure, such as floodable parks and planted wetlands, which kept nearby homes from flooding. But the report’s recommendations are at odds with some of the current political rhetoric around land use policy – in particular “greenfields” development that encourages urban sprawl[14]. Read more: National’s housing u-turn promotes urban sprawl – cities and ratepayers will pick up the bill[15] The report urges that cities be built upwards rather than outwards, and pushes back on residential infill development encouraged by the Medium Density Residential Standards[16]. Citing a recent report[17] on green space from the Parliamentary Commissioner for the Environment, the Helen Clark Foundation report argues for the preservation of urban green spaces – like backyards – as part of the flood mitigation approach. Preserving tree cover is another urgent priority. Trees help absorb rainfall, reduce erosion and provide essential shade and cooling in urban areas – counteracting the dangerous urban “heat island” effect[18]. Citing data from Global Forest Watch[19], the report states: Auckland has lost as much as 19% of its tree cover in the past 20 years, Dunedin a staggering 24%, Greater Wellington around 11% and Christchurch 13%. Read more: Planting more trees could reduce premature heat-related deaths in European cities by a third – new research[20] Incentives for homeowners Making Aotearoa New Zealand more resilient to extreme weather, the report says, need not break the bank. It recommends raising the national minimum standards governing the percentage of the total area of new developments that must be left unsealed. This would ensure the implementation of sponge city concepts, and see buildings clustered to maximise preserved green space. The government should also require local councils to plan for and provide public green spaces, and to develop long-term sponge city plans – just as they do for other types of critical infrastructure. Read more: We’re building harder, hotter cities: it’s vital we protect and grow urban green spaces – new report[21] Neighbourhoods could be retrofitted to include green roofs, permeable pavements and unsealed car parks. Land use and zoning could also encourage more vertical development, rather than sprawl or infill housing. The government could also provide incentives and education for homeowners to encourage minimising sealed surfaces, unblocking stormwater flow paths, and replacing lawns with native plants and rain gardens. More extreme weather and intense rainfall is a matter of when, not if. As the Helen Clark Foundation report makes clear, spending future billions is less of a priority than acting urgently now.

References

  1. ^ wildfire devastation (theconversation.com)
  2. ^ risk that much greater (www.theguardian.com)
  3. ^ massive hail storms and flooding (edition.cnn.com)
  4. ^ Slovenia (www.politico.eu)
  5. ^ Beijing (apnews.com)
  6. ^ one-in-200-year event (niwa.co.nz)
  7. ^ WSP (www.wsp.com)
  8. ^ Sponge Cities: Can they help us survive more intense rainfall? (helenclark.foundation)
  9. ^ NIWA (niwa.co.nz)
  10. ^ CC BY-NC-ND (creativecommons.org)
  11. ^ sponge city (theconversation.com)
  12. ^ cutting spending on critical stormwater repairs (www.nzherald.co.nz)
  13. ^ Auckland floods: even stormwater reform won’t be enough – we need a ‘sponge city’ to avoid future disasters (theconversation.com)
  14. ^ encourages urban sprawl (theconversation.com)
  15. ^ National’s housing u-turn promotes urban sprawl – cities and ratepayers will pick up the bill (theconversation.com)
  16. ^ Medium Density Residential Standards (environment.govt.nz)
  17. ^ recent report (theconversation.com)
  18. ^ urban “heat island” effect (theconversation.com)
  19. ^ Global Forest Watch (www.globalforestwatch.org)
  20. ^ Planting more trees could reduce premature heat-related deaths in European cities by a third – new research (theconversation.com)
  21. ^ We’re building harder, hotter cities: it’s vital we protect and grow urban green spaces – new report (theconversation.com)

Read more https://theconversation.com/creating-sponge-cities-to-cope-with-more-rainfall-neednt-cost-billions-but-nz-has-to-start-now-211181

Times Magazine

Headless CMS in Digital Twins and 3D Product Experiences

Image by freepik As the metaverse becomes more advanced and accessible, it's clear that multiple sectors will use digital twins and 3D product experiences to visualize, connect, and streamline efforts better. A digital twin is a virtual replica of ...

The Decline of Hyper-Casual: How Mid-Core Mobile Games Took Over in 2025

In recent years, the mobile gaming landscape has undergone a significant transformation, with mid-core mobile games emerging as the dominant force in app stores by 2025. This shift is underpinned by changing user habits and evolving monetization tr...

Understanding ITIL 4 and PRINCE2 Project Management Synergy

Key Highlights ITIL 4 focuses on IT service management, emphasising continual improvement and value creation through modern digital transformation approaches. PRINCE2 project management supports systematic planning and execution of projects wit...

What AI Adoption Means for the Future of Workplace Risk Management

Image by freepik As industrial operations become more complex and fast-paced, the risks faced by workers and employers alike continue to grow. Traditional safety models—reliant on manual oversight, reactive investigations, and standardised checklist...

From Beach Bops to Alpine Anthems: Your Sonos Survival Guide for a Long Weekend Escape

Alright, fellow adventurers and relaxation enthusiasts! So, you've packed your bags, charged your devices, and mentally prepared for that glorious King's Birthday long weekend. But hold on, are you really ready? Because a true long weekend warrior kn...

Effective Commercial Pest Control Solutions for a Safer Workplace

Keeping a workplace clean, safe, and free from pests is essential for maintaining productivity, protecting employee health, and upholding a company's reputation. Pests pose health risks, can cause structural damage, and can lead to serious legal an...

The Times Features

The Role of Your GP in Creating a Chronic Disease Management Plan That Works

Living with a long-term condition, whether that is diabetes, asthma, arthritis or heart disease, means making hundreds of small decisions every day. You plan your diet against m...

Troubleshooting Flickering Lights: A Comprehensive Guide for Homeowners

Image by rawpixel.com on Freepik Effectively addressing flickering lights in your home is more than just a matter of convenience; it's a pivotal aspect of both home safety and en...

My shins hurt after running. Could it be shin splints?

If you’ve started running for the first time, started again after a break, or your workout is more intense, you might have felt it. A dull, nagging ache down your shins after...

Metal Roof Replacement Cost Per Square Metre in 2025: A Comprehensive Guide for Australian Homeowners

In recent years, the trend of installing metal roofs has surged across Australia. With their reputation for being both robust and visually appealing, it's easy to understand thei...

Why You’re Always Adjusting Your Bra — and What to Do Instead

Image by freepik It starts with a gentle tug, then a subtle shift, and before you know it, you're adjusting your bra again — in the middle of work, at dinner, even on the couch. I...

How to Tell If Your Eyes Are Working Harder Than They Should Be

Image by freepik Most of us take our vision for granted—until it starts to let us down. Whether it's squinting at your phone, rubbing your eyes at the end of the day, or feeling ...