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two polaroid type photos on a rainy background, one of a garden by a busy street and another of plants and trees lining a gently winding road in west Auckland
From Wynyard Quarter to the Waitākere Ranges, Auckland’s future infrastructure is being built now (Image: Archi Banal Photos: Shanti Mathias)

SocietyJuly 10, 2023

The spongier city rising from the Auckland floods

two polaroid type photos on a rainy background, one of a garden by a busy street and another of plants and trees lining a gently winding road in west Auckland
From Wynyard Quarter to the Waitākere Ranges, Auckland’s future infrastructure is being built now (Image: Archi Banal Photos: Shanti Mathias)

Auckland’s floods damaged roads and wiped out houses. Repairs might also be an opportunity to make the city more resilient for the future.

‘The problem is that we build our cities to be impermeable,” says Murray Burt, surveying effects of that approach: a section of road near Titirangi where a bank has collapsed, a tumble of mud and trees cascading down the side of the road.  Cyclone Gabrielle was nearly five months ago, but the damage here is still present. Burt, Auckland Transport’s chief engineer and flood recovery manager, and Andy Patrick, flood recovery manager, go out every Wednesday afternoon to look at some of the 500-plus sites on the long list due for repairs. They want to have seen the places they’re trying to fix as they look at designs. 

I’m accompanying Burt and Patrick, wearing a slightly loose hard hat and surprisingly warm hi-vis jacket, because I want to get a sense of the specifics of flood recovery at individual sites. It’s easy to see the big numbers about how much a natural disaster costs or how long it will take to fix, but how do decisions get made about which options are chosen? And given a hotter, wetter future, will these choices be able to endure the weather of the future?

In the weeks immediately following the Auckland Anniversary and Cylone Gabrielle floods, there was a deluge of headlines about the concept of “sponge cities” – an idea immediately comprehensible through its name. Sponge cities provide the opposite of impermeable tarmac roads and iron roofs and concrete footpaths that channel water through cities into enormous storm drains, and wipe out roads and houses when those storm drains fill. Instead, they work with natural systems to absorb water into soil, not channel it into pipes, refilling groundwater supplies instead of depleting them.

two images of a green field and a flooded field
Greenslade Reserve during (right) and the day after (left) the January flood (Photos: Supplied)

Designing to accommodate water can be exceptionally successful. In Auckland’s Northcote, Greenslade Reserve was dug out to be at a lower level, channelling water away from the town centre and into the grass, where it could drain slower. During the Auckland Anniversary floods, 12 million litres of water drained through the field. 

That said, the concept of a spongy city isn’t entirely straightforward. “It reduces overland flow and runoff,”  Burt says. Less water racing across the surface means less slips and flooding, but there’s a flip side. “If there’s too much water in the ground, that can cause slips too – that’s actually resulted in slips occurring in places where there hasn’t been slips in the past.”

Projects like Greenslade are an obvious success, part of Auckland’s overall Healthy Waters plan – an approach that will be emphasised in the ongoing flood recovery. And while some “sponge city” developments are big, like Greenslade Reserve, they can also be small, like the gardens Auckland Transport’s Cathy Bebelman shows me. 

a drain next to a footpath surrounded by greenery
An overflow drain in a rain garden in Wynyard Quarter (Photo: Shanti Mathias)

“We get habitat, we get clean air, we get access to nature and we get flood mitigation,” she says, showing me the roadside gardens throughout Wynyard Quarter. Once she points them out, I see them everywhere: spaces where there are plants and a few trees, inset at the side of the road. While these rain gardens look simple on the surface, they’re more complicated to build, requiring several layers of different media underneath to help water drain quicker. Mulch and pebbles on the top prevent the plants from drying out too quickly, and sand and loam help water filter through, while an overflow drain at the top channels water into the stormwater system quickly when there’s a flood. 

The entire system, Bebelman explains, is designed to decrease the amount of contaminants getting into the harbour, as well as decreasing surface flooding on the roads. Roads are covered in grotty stuff: microplastics from car tires, macroplastics from litter and lots of chemicals from exhaust. Bebelman gestures out towards the Waitematā. In the 1990s, she could go and stand at Wynyard wharf on her lunch break and see plastic drifting into the sea from the stormwater pipes. Now, drains have treatment devices to remove contaminants – but it works even better in rain gardens, where the plants absorb the contaminants and they’re filtered out by the soil.

And the system works. Bebelman says that in the Auckland Anniversary floods, Wynyard Quarter fared relatively well, despite being downhill from a lot of impermeable streets and buildings. Part of that is because of the stormwater drains, but rain gardens and other efforts to make the city more porous helped too. While rain gardens do require valuable road real estate, the benefits go beyond just draining and filtering the water. Manholes fitted with water treatment devices are unobtrusive, but that isn’t necessarily a good thing. “You lose the opportunity to educate the public about what you’re doing,” Bebelman says. 

a road with a toppled tree and scoured out muddy gulch
Landslides can damage roads and be a result of sodden earth (Image: Shanti Mathias)

Rain gardens – or other water absorbing mechanisms like tree pits – are now included in most new developments in Auckland, along with other features that consider climatic change. As roads are upgraded, Bebelman says Auckland Transport looks at climate models for predicted future rainfall and heat. As we stroll from a street with rain gardens to one with standard footpaths, she points out that rising temperatures have to be a consideration too. “Black asphalt traps heat – you couldn’t walk across this road in the middle of summer in bare feet now,” she says. Compared to tarmac roads and concrete footpaths, the addition of rain gardens makes streets resilient in both sunshine and rain. 

Having to think hard about water and climate has been a complete shift in landscape architecture practice for Bridget Law, principal regenerative architect at Eke Panuku, the urban development arm of Auckland Council. “Previously, we would work around amenity and beauty – now we want those places to provide stormwater management and lots of other benefits,” she says.

Law has been involved in the redevelopment of Wynyard Quarter, including a new park on Wynyard Point which was previously an industrial zone. The park is an example, she says, of how complicated redevelopment really is. “There’s no one-size-fits-all development,” she says. “We have to prevent the water [there] from permeating into the land because it’s contaminated, so our rain gardens are vaulted structures that go into a stormwater drain.” 

The storms at the start of this year have also contributed to a rethink of priorities in the site design. “It’s usually best practice to design for one in 100 year storms,” Law says. “If we build climate into the brief and we think those storms are going to be more frequent, what’s the next level we need to design for?” There are a variety of different climate possibilities, and complex tensions at play. Building for relatively rare storm events, even in a warmer and wetter future, requires resources now, and may mean that infrastructure takes longer to deliver. Law, like everyone in this story, consults climate models as part of her decision-making around designs, but she also has to think about budgets, delivery targets, and the amount of carbon created in implementing a project. 

Including more water-sensitive design is also a question of cultural respect. “Lots of the practice around using rain gardens and letting natural systems do the work is aligned around te ao Māori worldviews too – it’s a way to look at water with more respect as a valuable resource, not shoving it underground and treating it as a nuisance.”

But in large volumes at unexpected times, water is a nuisance, as the damaged roads that Burt and Patrick visit each week show. As we drive around West Auckland (in an Auckland Transport electric vehicle), there are many sections of road where a collapsed bank has made the road one-way only. At one site, a massive retaining wall is being built. It’s been raining all week, and big beams of steel and a drill bit are sitting at the bottom of a bank; the road is slippery with mud. I start to question how interesting it will be to describe road fixing processes in my story. 

While Burt and Patrick talk to the contractor, I strike up a conversation with the two men who have been working here for a month to manage traffic, with only pedestrians allowed past. They tell me that one neighbour is upset because there’s a possibility her garage could be taken out by a landslide, but most of the other locals understand that the team is fixing things as quickly as possible. “The main problem is just the weather, fighting with the water,” one tells me, glancing at the lowering sky. 

two people in orange high vis stand on a road looking at a landslide
Andy Patrick (left) and Murray Burt (right) survey a place where there was landslide in Waikowhai Park (Image Shanti Mathias)

As we drive to the next landslide sight (in a branded electric car), I ask: how have the enormous number of road repairs in recent months been a chance to build back stronger and spongier? Improving drainage standards is an obvious one, says Burt, as Patrick, who is driving, skirts around another team of contractors. (“Must be Watercare – it’s not one of ours.”) 

“And if there’s an option for more resilience, we’ll add it – if we lost a bridge, we’ll propose building back at a higher level.”

Burt worked in disaster recovery overseas for more than a decade before returning to Aotearoa. He was part of international aid efforts to rebuild in Sri Lanka after the Boxing Day tsunami, in Haiti after the 2010 earthquake, in Myanmar after Cyclone Nargis, and in refugee camps with the UN. In many of those places he saw a different approach to infrastructure, born out of necessity: things that were easy and cheap to rebuild instead of “hard infrastructure, more walls, more concrete”, requiring investment but intended to last. “Do you build back to protect from another tsunami, or do you build back in a way that if you got hit by another tsunami, you can quickly rebuild your life?”

a corner of road with two big ol' poles plunged into the empty space to build a future retaining wall
A retaining wall in progress (Photo: Shanti Mathias)

One thing at least is clear: some of the design standards that Auckland Transport has been using are out of date. “We’ve been building for the one in 100 year storm, but on the basis that this storm was so enormous, some of those design charts will need to change,” Burt says. There’s always more willingness to invest in fixing something after it’s happened than to reinforce infrastructure for the hypothetical disaster. “We’re rebuilding something that already exists,” adds Patrick. “The road is already here.” That makes it easier to stick with current systems, even as design protocols slowly change. 

As well as climate change, population growth is a major consideration for what kinds of disasters to prepare for. The bigger Auckland gets, the more land area it takes up, the more tarmac-covered surfaces there are for water to run off. After the improvement to Greenslade Reserve in Northcote, improving flooding infrastructure in densely populated Māngere is going to be a priority; Burt says newer developments in areas like Green Bay fared relatively well in the flood thanks to their bigger pipes.

Auckland’s flood recovery is being shaped by a need to be spongy and climate resilient – priorities that those working on the recovery hope have been adequately factored into the buffet of plans and design standards that they are expected to adhere to. As I walk with Patrick and Burt through Waikowhai Park in Hillsborough, they try to figure out why the road is closed now that the main landslide has been cleared and conclude it’s probably a decision by the Parks team, which is part of Auckland Council, not AT. The necessary bureaucracy of a city like Auckland impacts the kinds of solutions that are chosen. “Sometimes we’re able to build an asset and maintain it ourselves, but at other times that maintenance will be managed by AT or Watercare or Parks,” Law explains. In a big city, there are a lot of actors involved in making a spongy city, a juggle of different stakeholders. 

In some ways, Patrick says, it might look like nothing’s changing in Auckland after two climate change-connected floods at the start of the year – just road cones and the same old car dependence. But things are getting fixed with the expectation of an altered future. “Lifeline” routes have been opened to the most-affected communities.“We’ve been doing investigations, drilling into the land to see what to change, someone in an office is drawing up designs. A lot is happening!” he says. Sure, a lot is happening; but as we drive through the rain garden-lined streets back to the Auckland Transport building, the windscreen wipers thwacking raindrops away, it’s clear there’s a lot more work like this ahead.

Keep going!