From extreme storms, to changes in the water cycle, the urban environment is becoming more susceptible to environmental change. Many cities around the world are now looking towards Blue-Green infrastructure to manage the impacts of climate change and make cities better places to live.

Emily O’Donnell

With the MET Office suggesting that the summer of 2024 could be the wettest since the year the Titanic sank, I visited Dr. Emily O’Donnell from the School of Geography at the University of Nottingham to discuss this idea and how it might be valuable to the residents of the Meadows. Emily is an expert on managing flood risk through Blue-Green infrastructure: natural and designed landscapes of various scales that include small physical interventions such as swales and green roofs, alongside green spaces that are designed to turn ‘blue’ during rainfall events. These measures aim to recreate a more natural water cycle at the city scale, protect the hydrological and ecological values of the urban landscape, and provide resilient and adaptive solutions to deal with flood events.

If you’d like to hear Emily introduce this idea before reading the conversation that we had then you can find that here.

So where did this idea originally come from?

It started off in America; in Portland, Oregon around thirty years ago, following changes to the Clean Water Act. There was an excessive burden on the city’s drainage system that led to the repeated discharge of sewage into the Willamette River because of overflows. They realised that they could either spend billions on a new sewer pipe or find other ways to stop rain and surface water draining into the old pipes.

Traditionally, here in the U.K., we manage water by building walls and barriers and redirecting water into pipes. We don't want to see rain; it's a nuisance; we just want to get rid of it. But, as with Portland, there comes a point when you realise that you can’t keep doing this for ever. I mean, how big do the pipes need to be, especially if you don't know how much rain we're going to have in the future? So, the question is, how can you manage this rainfall in a different way?

When Portland started to answer this question, there was a push for working with nature by reintroducing green space into cities. They began to think about how they could combine these challenges and use green space to manage water and flood risk in a better way. For instance, they started to build swales across the city—relatively small areas designed for surface water to run into them, allowing it to drain into the ground. They filled them with plants and vegetation to capture carbon dioxide from the atmosphere, improving air quality by trapping pollutants, and providing a habitat for wildlife.

And has this idea caught on here?

There is no statutory requirement to use blue and green spaces to manage flood risk, which is the problem. There are lots of policies around green space, but not all green space is designed to manage water. There are examples in the U.K. where Blue-Green infrastructure has been put in and there are cities adopting a Blue-Green approach, but it's not national.

Newcastle has a new scheme at the moment called Newcastle Blue-Green City and they have around £70 million of government funding to put Blue-Green infrastructure into place. London has lots of examples but it's piece meal. There'll be a nice example for one housing development, but then the rest of the city will just be what we call Grey infrastructure, with lots of underground piped drainage, lots of sewer systems that get full when it rains, leading to an increased flood risk.

You can read more about these ‘Sustainable Drainage Solutions (SUDS) here.

An artist’s impression of blue green infrastructure on Newcastle's Barrack Road.

The new Labour government have prioritised house building, through the private sector. If I was building a housing development and wanted to incorporate Blue-Green infrastructure, what would I do?

You'd have an area of space that wouldn't have a house on it. It would have a detention pond or something similar, so that all the water that rains onto that housing development is channelled down into that pond, where it eventually reaches the groundwater or slowly travels through the subsurface. The aim is to ensure that none of the rainwater goes into the sewers and that you use those solely for sewage.

You'd have green roofs on the houses. You'd have permeable paving (using a material such as ‘thirsty concrete’), so where you've got parking spaces the rain could infiltrate into the ground, rather than just being stuck on the surface. In Rotterdam, they have green tram tracks, but you can only do that if you haven't got traffic driving across them and turning them into mud.

There is a requirement for larger housing developments to incorporate some form of sustainable drainage; however you often find that a pond may be put in a corner that nobody really sees or uses. What makes Blue-Green infrastructure valuable is its ability to manage water while also being used in other ways. If designed well, people can use and enjoy that space, it can have social and psychological benefits and improve public health.

What is your work doing in trying to promote this idea?

I measure what we've already got to see if it works.

We have sensors in our swales to see if they’re actually storing water— which they are. I also talk to people about what they think about these kinds of assets and explore public perceptions. Usually people like them, if they look nice, and they usually have no idea that they have any water management function. When people understand what the BGI are doing they're more likely to look after them.

There’s a push, not just in the U.K. but everywhere, for local stewardship of Blue-Green infrastructure to help engage residents in managing their local environment and because the local authorities often don't have capacity to do the required maintenance. Things like clearing out litter from a swale for instance is something that residents could do, because if you get litter filling up these assets then the water's not going to drain as well.

In places like Portland, where they've been doing this for thirty years, they have a Green Street Steward programme where people look after the swale outside their houses; they take ownership of it.