Rethinking the urban dream

With weather disasters becoming more frequent, overheating, flooding and growing stresses in everyday life, can the design of our homes and communities provide relief? Research shows the answer is a resounding 'yes'!

We’re not making them anymore, but the old quarter-acre sections with big back lawns, feijoa and plum trees and a veggie garden still hold a special place in our hearts. They gave us a lot: the practical advantages of space for leisure and home-grown food, room to unwind and large green areas to soak up the rain.

We have lost many of those benefits. The 2023 report from Parliamentary Commissioner for the Environment, Are we building harder, hotter cities? The vital importance of urban green spaces, found that, between 1980 and 2016, green space per person fell by at least 30% in Auckland and at least 20% in Hamilton. Most of this loss occurred on private residential land, largely the result of infill development and a shift towards larger houses on smaller sections in new subdivisions.

There is a move under way to turn around the loss of green space and amenities we once took for granted. This will help deal with all sorts of challenges – from climate change to massive infrastructure costs to physical and mental health issues. Studies overseas have found reduced prescriptions for anti-depressants in the types of homes and communities we are talking about. Cities with many green spaces, such as London with all its parks and squares, are much more popular with both residents and visitors alike than cities with little green space.

There’s no going back to quarter-acre sections, but we can take steps to restore the comforts and benefits they once provided. These will become increasingly valuable as our climate continues to change.

What Auckland and Paris have in common

Christophe Najdovski, Deputy Mayor of Paris, has described the city leaders' role as 'protecting Parisians from heatwaves, anticipating the risk of flooding, preserving biodiversity and preventing the growing scarcity of water resources'. His words apply equally to Auckland. So, what is Paris doing?

• In 2024, the Paris City Council adopted the Local Bioclimatic Urbanism Plan to protect existing green spaces and create more, adapting the capital to heat waves and flooding.

  
  

• The city has a target of 300 additional hectares of public green space by 2040.

  
  

• More than 100,000 trees have been planted in the city since 2020.

  
  

• Mixed-use developments are encouraged – in western Paris, large new or redeveloped office complexes must include a certain amount of housing.

  
  

• Renovation is becoming the new standard for reducing the environmental impact of construction. Demolition will become an exception.

  
  

• Asphalt surfaces are being replaced with permeable materials adapted to heatwaves.

Auckland has its Urban Ngahere (Forest) Strategy, which aims to increase average canopy cover to 30% across its urban area. However, there is limited incentive to encourage pocket forest expansion and over 60% of existing trees are on private land and difficult to protect. The city has actually been losing trees – as much as 19% of tree cover in two decades according to one estimate.

Gardens for the rain

For flood resilience and improved-quality green space, there are some practical steps to take for new homes:

• Avoid removing topsoil from a building site wherever possible or reinstate topsoil after building is completed. Where topsoil has been stripped off, it can be more difficult to plant trees and gardens.

  
  

• Limit paved/concreted areas to those strictly necessary and make paved driveways and paths permeable so rainwater soaks into the ground. Permeable concrete is available with small, interconnected voids (and no sand), letting water drain quickly. It is strong enough for driveways.

  
  

• Design rain gardens of flax and other natives to hold and process water naturally. This is better than lawns, which may not be much more permeable than paving if the ground is hard.

  
  

• Leave trees in place and plant new trees. Mature trees can intercept a significant proportion of the rain that falls on them, keeping it out of stormwater drains and ultimately reducing pressure (and therefore costs) on our grey infrastructure (stormwater pipes and so on).

Hot in the city, cooler in a garden city

Getting new housing right is only part of what is required. We need a different approach to tackle the ever-more expensive costs of flooding and overheating in our communities. More holistic, systematic planning that involves a range of agencies is likely to give the best results. Just prioritising pipes isn’t supported by evidence from Aotearoa New Zealand or around the world.

Since the 1960s, temperatures in Hong Kong have been climbing steadily – a result of the city’s development itself as much as climate change. Researchers, who combined real-world climate data with simulations, uncovered how urban structure and wind dynamics uniquely shape thermal conditions.

They advocate moving from isolated technical fixes to a system-of-systems strategy that considers the city as a holistic, interactive climate entity.

Singapore’s long-term holistic vision of a ‘garden city’ began with founder Lee Kwan Yew back in the mid-1960s.

Today, its Green Plan 2030, led by five government ministries working closely together, will expand the Nature Park Network, strengthen connectivity between Singapore’s green spaces and restore nature into the urban landscape.

Sponge cities and flood plains

Kali Mercier, WSP fellow and author of The Helen Clark Foundation/WSP 2023 publication Sponge Cities: Can they help us survive more intense rainfall? found a compelling cost-benefit ratio for the sponge city concept. It involves building or restoring urban green spaces, pocket forests and wetlands, and daylighting streams by opening up and restoring watercourses that had been diverted below ground, to create space for urban waterways to safely flood (which Auckland is already doing), and moving people and houses out of high-risk areas.

“We keep building on high-risk flood plains, which is absolutely mad,” she told Build. “I’m not saying you can never build on land that carries a level of risk, but it needs to be carefully planned. In particular, we need to be aware of [floodwater] flow paths and not get in their way.” She cites Auckland City’s Making Space for Water programme as a good initiative.

“Housing densification needs to be thought of as a whole process. We can’t fill in all the gaps with buildings without looking at what we are losing in terms of green, absorbent infrastructure that protects us from floods.” Kali Mercier talks about ‘bucket cities’ as well as sponge cities – cities that plan areas that can temporarily hold large volumes of stormwater.

There is currently a proposal to create a ‘bucket’, using part of AF Thomas Park on Auckland’s North Shore, site of the Takapuna Golf Course. This would temporarily capture about 550,000m³ of floodwater, reducing the risk to 10 hectares of homes and critical infrastructure.

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Original article by David Hindley, Freelance Technical Writer. The full article was first published in Issue 207 of BRANZ Build magazine. www.branz.co.nz