Sustain Episode 4: How can nature guide our remedies for climate change driven flooding?

Maria Armoudian: Hello and welcome to Sustain, a production of Ngā Ara Whetū: Center for Climate, Biodiversity and Society, I’m Maria Armoudian. As the climate crisis continues, flooding has become an increasingly serious problem, causing death and destruction all over the world. How can we adapt to this new reality? Do we need to reassess our relationship with water? Can nature itself inform us about how to minimise these disasters? Joining us today are two experts, University of Auckland, Professor Gary Brierley of Geography, and Tim Welch, Senior Lecturer in Architecture and Planning. Welcome to you both, to the Sustain podcast. So glad that you could be with us here.

Maria Armoudian: I think we should start with both of your arguments about how, through really trying to manage the environment, whether how we’ve built our cities, Tim, the way you’ve looked at things, or control our rivers, Gary, the way you’ve looked at things, we’ve made ourselves more vulnerable to climate change threats like flooding, and that we’re exacerbating the problem because of these things. So maybe we should lay out the problems first. Tim Welch, Would you like to start?

Tim Welch: Coming from an urban planning perspective, so much of what we’ve done in building our cities has been fighting against nature, and obviously water is one of those big things. We’ve tried to figure out ways that we can shed water away from buildings, channel it down our streets, put it into drains, into pipes, and then send it back out into rivers and lakes and out into the sea. As a result, we’ve kind of limited ourselves on how well we can handle water. Any time we see any kind of rainfall or event that’s greater, or exceeds what we engineered years and years ago, we’re suddenly in a lot of trouble, we see flooding. We see damage to property, and we start spinning around wondering what are we going to do next? How are we going to handle what’s inevitably a changing and wetter climate in the future?

MA: How much of it in your work is really about building materials?

Tim Welch: That’s really kind of the crux of it. We’ve put a lot of stock in our ability to engineer our way out of every single problem, and that comes right down to the building materials. They’re all impervious surfaces, things that don’t drain water, they channel water, they let it flow across surfaces and into drains, but they don’t absorb water. That’s the exact opposite of what we see in nature. We’re fighting nature to a big degree, and as a result, we’ve put ourselves in a precarious situation.

MA: How widespread is this? Is this every city on the planet that’s dealing with this, because we’ve all tried to build cities in a particular way?

TW: The headlines over the last year have been pretty stark. It wasn’t just Auckland that had a one in 200 year flood, although that 200 year number is probably a lot smaller now as we see wetter climate coming. But there are cities all across the globe that dealt with catastrophic flooding, and every city has essentially been built the same way for years and years and years, with lots of impervious surfaces. That’s just the way business is done. A number of cities have started to pull back and try to address that and build in new ways. There’s no one city that’s done a perfect job of it, but there are lots of examples of cities that are trying to address this finally.

MA: Great, and I’m looking forward to getting into all of that. One last question for you, before we turn to rivers and what we’ve done to them in a similar capacity, and that is one of the things I read in your piece, Tim Welch, one of your pieces was about how with this flooding comes this mix of toxic sludge and sewage and yucky stuff. Why is that happening?

TW: We have a nice name for it, we just call it CSO or combined sewage overflow. But the reality is, every time it rains, not every time, but many times when it rains heavily, our drainage systems, our stormwater systems are overwhelmed and they can flood into and mix with our sewage systems. They all follow, essentially, pipes underground. They’re all linked in some way, and as a result, we get these really disgusting mixes, and then that all goes out to the sea. As soon as we see a big flood, a big rain happening across the city, we see all our beaches shutting down because of this gross toxic flow that goes out there.

TW: The reality is we have, across New Zealand, 17,000 kilometres of pipes of stormwater, fresh water and sewage pipes, and they all need to be renewed eventually. We built massively through the 1950s and 1960s for an expanding population in cities and so we’re at a situation where we’re looking at $180 billion or so of cost to renew all of that infrastructure. As it ages, and as we don’t pay that bill, we see more and more events where we get these kind of mixes of sewage and stormwater into our waterways.

MA: I suspect it’s going on beyond Auckland and New Zealand.

TW: Yeah, it’s not just a New Zealand thing, it’s a global phenomenon.

MA: Gary Brierley, let’s bring you in. You’ve been talking about how we’re trying to confine rivers and that’s exacerbating the problem too, how we’ve kind of strangled them. How does this make flooding and disaster worse?

Gary Brierley: It’s a different context to the one that Tim’s just been talking to because oftentimes we’re now talking about rural settings rather than urban settings, although there are issues in urban settings relating to confining rivers or strangling rivers or burying rivers. When you confine a river, you concentrate its energy. When you concentrate the energy of a river system, you’ve got the same body of water going down through a smaller space. And when you concentrate that energy of the river, the river reacts and responds in a different way to what it did previously.

Gary Brierley: Just in the same way that Tim was saying a second ago, the way that we planned for these kinds of activities, because this was purposeful. We had a total catchment management ethos of trying to regulate and manage our rivers in a particular kind of way. That came about largely in the 1950s and onwards, but we tried to separate the channel from the valley floor, separate the channel from its floodplain and concentrate the flow in that area, so the mentality or relationships with which we saw rivers was one of flushing systems, systems that just washed that water away, got it offshore, no problem. Away we go.

GB: But that’s not how rivers work. Rivers previously built those floodplains. They were all part of that river system, and we have changed the morphodynamics of those systems. Rivers respond now in different ways, and depending upon how much sediment is moving through that river system, the bed of the river has either incised, it’s cut down, or in other instances, the bed of the river has built up, it’s aggraded. If there’s been too much sediment coming from upstream, if you have excess sediment from upstream that used to be spread over the floodplain but is now concentrated in the channel, that means that your capacity of the channel has been reduced, which means that we are now manufacturing future disasters in the ways that we’re looking after those situations.

MA: Because of that energy?

GB: Because of the concentration of the energy. And if you’ve had excess sediment load from upstream, and the bed of the river is built up, the only option that we now have is to build stopbanks higher, artificial levees, build them higher. There’s not just issues of environmental damage that comes from these kind of practices, it’s also issues of the economic cost and the cost for future generations. What we call path dependencies. We’re locked into a limited way of doing things now because that’s the way that we have been doing things for a long, long time. And I know this is preempting where we’re going to.

MA: Before you preempt, there’s a phrase that you used in one of your pieces. That was zombie rivers. And so I wanted to understand exactly how rivers can become zombies.

GB: We’re making them lifeless. In the sense that, if you think of the way that a river system adjusts on its valley floor when it doesn’t have stopbanks, it dissipates its energy and creates all this diversity of habitat across the valley floor and all this wide range of landforms in pools and riffles and runs and backwater effects, and these kinds of things, and swamps and wetlands. All of those diverse habitats drive how a river system works in ecological terms because you’ve got all those features, you channelised a river, you concentrate its energy and you diminish that habitat. You take a lot of that habitat away.

GB: Rivers that used to be living systems, they’re now concentrated energy systems which have far less habitat than they previously did have. So we’re creating these zombie lifeless forms that simply, the ecosystem processes that fashioned and shaped the way those river systems work, the rivers had those options taken away from it

MA: Because you did mention also in that piece about the self-correcting nature of rivers, it knows what to do in a way.

GB: Rivers are absolutely wonderful. They’re just amazing at looking after themselves. The river, if it’s a setting where the river itself adjusts, what we call an alluvial river, the river creates its own morphology. It decides how many channels it wants to have. It decides what the sinuosity, the wiggliness, of those channels is going to be. It decides how it’s going to adjust on the valley floor. Rivers are attuned to use their own energy through those different kinds of mechanisms, how they create their own roughness within those systems.

MA: And that is both from the water and the biodiversity

GB: And the sediment that they’re moving, the ways that sediments are moved and the ways that they manage their roughness, the riparian vegetation, or the role of wood within river systems, are fundamental to the ways that river systems work. When a river hangs together well, all those different parts are in harmony, they’re in sync with each other, and we’ve kind of taken that functionality away.

MA: Through you said narrowing the channels, but also damming.

GB: Absolutely, we talk about damming in terms of silencing rivers and we talk about stopbanks as strangling rivers. And so, we’ve modified connectivity relationships, the ways that these systems function

MA: In fact, I think I remember reading about how you said language really matters in one of your pieces too, and really the language you’re choosing does articulate something in a different way than how we traditionally speak about them,

GB: Particularly in the context of Aotearoa, I think that language is absolutely pivotal to everything we’re talking about now. I’ll be honest, I don’t even like the language of management, because management is asserting human authority over rivers as opposed to living generatively with living rivers. That’s the language that I prefer to use in terms of expressing our relationships to rivers and aspirations for what rivers can be.

MA: One other thing that you touched on briefly as you were talking, but I just want to go back to it, is you were talking about rivers that have been sort of buried. How do you unearth a river that’s been buried?

GB: There have been numerous daylighting exercises, including here in Auckland City. There are plans or proposals for other ventures in that space here, just in the same way as has happened in other parts of the world. Essentially you are recreating a space that the river has back on the valley floor and taking it out of the pipe.

GB: As a general direction, I approve of things that way, but we’re kind of playing God in thinking about what kind of river we want whenever we daylight. Do we want something that largely puts the river over there, separate from society, as opposed to merging that river as a part of society in the way we conceptualise it? So there are examples here in Auckland where if we let the river do its own thing, it would become a wetland, and wetlands aren’t necessarily the kind of rivers that we want. If we have a river that is in a nice, smooth, meandering channel that behaves itself, then that’s the river that is deemed to be acceptable.

MA: Well, now that you said wetland, let’s go back to Tim Welch for a minute, because that’s one of the ways that these new ways of working with nature, sponge city types of things, is enabling wetlands. Can you talk to us about this idea of sponge cities, what they are exactly, and how they work with these water bodies?

Tim Welch: Sponge City is really just kind of a name that’s marketable, that was put on a general concept of not burying nature under a lot of pavement. A professor named Kongjian Yu in the year 2000 came up with this term and broadly the idea is to move away from what we call grey infrastructure, paved and engineered solutions, as we were just mentioning. Putting streams and rivers in in culverts, in cement boxes underground, in paving over every surface, in making sure that every driveway has runoff to pipes, and moving it over to what we call green systems. Letting green space do the work that it’s done since before people were around even, that it’s well attuned to do, and part of that, there’s two prongs to it.

TW: One of it is trying to preserve as much green space and wetland as possible, something we’ve done pretty poorly and we’re still not doing well in the city, in the country and most cities around the world. We still think that outward expansion of our cities, paving over lots of green space areas that are prone to flooding is still a cheaper way to develop and provide housing. We continue to do that, putting ourselves more at risk and reducing the capacity of the natural environment to absorb floodwater, rain, etc.

TW: Then the other way that we can retrofit our cities to make them spongier, more absorbent, some of the simple ways we do things is collect the water as it falls, as much as we can so that we can reuse it. So, rain barrels, things that collect water at your house, that is, they run off the roof, where it can be reused in your gardens. Simple things like not planting lawns, but using more native plants in your garden, they’re better at absorbing and holding water. Using the rainwater you collect to water those gardens. Driveways that have permeable surfaces, if you’re going to rebuild your driveway, replace it with gravel or cement strips, rather than one big cement block that just creates a river for water to flow into the streets.

TW: There’s all sorts of other examples of things that are done around the city and in other places. One of the ways we’ve tried to do things is build green space that can flood. Up in Northcote here in Auckland, there’s a great floodable park, it’s green space, you can play rugby or football on it, and then during a major event it basically fills with water. But it’s been designed in a way to quickly drain and then return to green space. Hobsonville Point also has special zoning that requires it to build in a lot of things that mitigate flooding. They have bioswales, which are boxes along the way before you get to a storm drain, that have natural plantings in them, and sand and rock that drains and filters rainwater and captures a lot of that before it goes into the pipes.

TW: Everybody has cisterns in their house so they can capture at least a thousand litres of rain before it goes into the system. And then a lot of the flood plain has been preserved over time, and as a result, during last year’s floods in January, Hobsonville Point didn’t flood really, it mostly stayed dry. Same with Northcote, a lot of those houses did not flood as a result because the park flooded instead and even a place closer to the central city in Stonefields development, it used to be an old stone quarry and they left that quarry essentially there. It could continue to flood during a storm and then it’s a recreation area afterwards. It’s just a lot of working with what already exists in nature, letting things flood where possible and not trying to control or, as Gary said, manage water as much as we do.

TW: There’s really great examples from all over the world. One of the leading examples of ways that we do this in an urban environment is in Seoul, South Korea. The Yangjaecheon River, in the 1970s, they put it underground, essentially put it in a cement box, and built a six lane highway over the top in 2000. Yeah, it was pretty bad, and then in 2003, the mayor of the city decided that they wanted to revive the river, get rid of the highway, and they proceeded and they essentially tore down the highway and brought that river back up to the surface. It’s still not a 100% natural environment, but it does a great job channelling flood water. It’s a huge centrepiece for the city, it’s a tourist attraction, but also a gathering point for festivals. It’s one of those things where, if we start to build more sponge city concepts into cities, it not just makes it more resilient, but it makes it a nicer place to live as well.

MA: Are there any other examples that you can think of where people have integrated sponge city ideas that make sense and that have worked?

TW: We go back a few years, Berlin had catastrophic flooding and they spent a lot of time since then building stormwater catchment that uses more natural integration in the city. Big reservoirs and lakes that capture water, reducing their reliance on pipes. Jakarta, Indonesia, suffers a lot from monsoon flooding. They get a huge rainy season, plus they’re dealing with soil subsistence, so the city itself is actually sinking. They have a strange relationship, or a rough relationship with water as it is, but they’ve worked hard on building more of these sponge city concepts into the city as well.

TW: Singapore is leading the way as well. And again, where sponge cities originated in China, there’s over 200 cities that are starting to build sponge city concepts. Wuhan is one of the leaders in that, but Shanghai is also doing it as well. There’s a lot of work being done, and it’s mostly in cities that have had either catastrophic flooding at one point or have this relationship with a really rainy season. They know it’s only going to get worse over time and they might as well do it now rather than kick the ball and wait longer.

MA: Gary Brierley, over to you.

Gary Brierley: I just think it’s fascinating to reflect on parallels in the ways that thinking is shifting. If I move into the bigger picture, rivers space, rather than specifically focusing on urban environments, the principles and ethos that we’re moving towards, nature-based solutions, are very, very similar. It’s like a conservation-first ethos. If you’ve got bits that are working well, look after them. Identify what those bits are. If you’ve got bits of river systems that have got space to adjust where water can be stored, allow those bits of the system to function in that kind of way.

GB: I think the conservation-first ethos definitely works and then it’s kind of, well, how do we frame recovery programmes? What does that mean? What does that look like? And across the world there’s a move towards natural flood management programmes and there are key principles that underpin that. The first one is catchment scale, watershed scale planning, where you manage at source and at scale, and you recognise that the issues at the bottom ends of catchments are largely products of what happens upstream. There’s massive issues of equity and social and environmental justice in the ways that we frame these kinds of applications.

GB: But shifting the mentality towards one of bigger picture thinking, about the ways that water is moving through systems, thinking about, for example, how deforestation in certain systems has changed the flow in sediment budgets and how we’ve got legacy effects from that. But what the benefits could be of reforesting certain areas, or targeted interventions that do that, and how these relationships play out for different river systems.

GB: There’s a nice language that’s emerging of understanding the story of the river, understanding how each river system works, and if you understand it’s the story of that river, then you’ve got a sense of what targeted-event interventions can look like for that particular system. Recognising that one of the best interventions we’ve got is to promote self-healing, to let the river look after itself as far as practicable. But then there are other instances where we need to give the river more space. We need to work out what is possible where, in giving the river back the space that the river sees as its land already.

GB: When you look across Aotearoa, you can see very different opportunities for that in different contexts. But this space-to-move intervention, this freedom space or erodible corridor thinking, again, is global in terms of its scope. There’s amazing sets of activities that have taken place in Europe and in North America in relation to these kinds of practices, and this kind of thinking is already well-embedded across various parts of Asia and we have to seriously think about what this looks like in a New Zealand context.

MA: One of the things that you have noted in some of your writing is that nature-based solutions really need to be examined through an indigenous lens, because if you do then introduce species, it can also do damage.

GB: 100%, not speaking on behalf of others, but working and collaborating with colleagues for whom I have immense respect in this space, I think that we need to embrace a different way of thinking, and working with colleagues such as Dan Hikuroa and with Anne Salmond and Billie Lythberg from Business and Māori Studies.

MA: But also in terms of the Indigenous species.

GB: Again, got to be very, very careful, in terms of how we conceptualise these things and what works well where, because there are definitely instances where, if we want to act quickly, then exotics provide a mechanism to do that. There’s massive controversy in things like natural sequence farming in Australia over the use of exotic species, and there’s various major-scale river restoration, river rehabilitation projects in China that are using plants that come out of Mexico. Everything is contextual. That’s the one thing that I would say. I think that there are times when we can’t afford to be too precious because the issues that we’ve got to address need attention now. We’ve got to look at these things over an array of different time scales, and not just hone in on notional quick fixes, but in some instances, that is what we need.

MA: Let’s finalise with the politics and policy of all this. What does it take policy-wise and politically to advance these types of things? Tim Welch, you first.

TW: The direction we want to go in the future politically has put ourselves at odds with implementing these more nature-based solutions. Our current trajectory is, again, to build out our cities, to continue to pave over green space and wetlands, putting people at risk, our cities at risk, and again, to build out and not up. We have historically densified in a way that’s also made ourselves more vulnerable over time. This gets back to politics here, but we have swallowed up backyards and trees, and things like that, that also help mitigate floods, in order to build more single family housing.

TW: What we really need to do is build ourselves more vertically. Rain doesn’t have a problem with us going vertical. It’s the same roof space no matter how many stories you have, essentially. That’s one way in which we can start to combat in the future, through policy, some of the risks to flooding and be more sustainable as a city, is to continue to grow upwards rather than outwards. So that’s a big component of it. Things like car parks could be reduced and could be using more permeable surfaces.

TW: If we build that into our policy, as we redevelop road space, we could build into our policy that, instead of just like-for-like replacement, repaving a road, we can build in more materials and more things like bioswales that help us collect rainwater and channel it more appropriately, relying less on pipes. There’s all kinds of things that we can do politically, through policy that doesn’t require significantly more funding than we’re already facing in upgrading the existing systems, but it requires political willpower to do that. At this stage, we just don’t have that leadership politically right now, we’re focused on building as quickly as we can, as much as we can, as far out as we can, and so we’re really just setting ourselves up for more problems down the road.

MA: Last word, Gary Brierley.

GB: I’ve got a playful way of dealing with this at the moment. My big mantra at the moment, I’m pushing for CORPS, Communities Of River Practitioners, ways of working together towards better futures. And it’s a play on language there, because it’s a bit of a critique on the Corps of Engineers that created the silenced and strangled rivers that we’re dealing with. I see our future very much as a collective community-focused set of outcomes that moves beyond the singular focus on a development ethos that is just making the same mistakes that we’ve been making recurrently. We can do better, we owe it to ourselves and future generations to do better.

GB: Unfortunately, I agree completely with that set of comments from Tim there. I think that there’s an enormous disconnect between the practitioners, the people who are working in agencies and councils, consulting groups and CRIs, in the sense of what they want to be doing relative to what policy is allowing them to do. There is this tragic disconnect, the situation is bordering on woeful at the moment, in the ways in which some of these things are moving forward. There’s a positive side to that. The people are available who can bring about transformative practice. There’s a very large number of individuals in those various bodies and organisations who can pull together to enact change in different kinds of ways.

MA: Well, thank you both so much for sharing your research and your wisdom with us, really appreciate your work. Thank you.

GB: Final comment, listen to the river and learn from it.

MA: And that’s it for today’s programme. Thank you so much to our guests, Gary Brierley and Tim Welch, both of the University of Auckland. Thank you so much to Tim Page for engineering and Ben Goldson for production. We’ll see you next time.