SuDS or duds: spot the difference

Jo Bradley knows good sustainable drainage systems (SuDS). And she can’t help but wonder: in a world with nature in crisis, why don’t we design SuDS that create habitats for wildlife?

I love SuDS. I love the whole concept of having green spaces in and around our homes and offices, creating pockets of habitat for wildlife to thrive in.

But we’ve been delivering SuDS in the UK now for 20 years and we’ve got stuck in a rut. Our SuDS are starting to look the same and maybe water-company adoption will make that worse as developers learn how to meet the needs of the companies with text-book SuDS that – quote – tick all the boxes?

But do they really tick the boxes at all? Or are they just monotonous swales and dreary basins?

We’ve become pretty good at the hydraulic design of SuDS, attenuating and capturing water to reduce flood risk. I’m pleased to say that most designers are getting better at the water-quality element too, including treatment devices where necessary to capture the pollutants – it’s not true of some obvious infrastructure operators, but let’s save that story for another day.

Good landscape designers have created divine SuDS for people to spend time outside and children to frolic amongst the flowers. But the bit that’s missing – the bit we only pay lip-service to – is providing habitats for wildlife.

Drought lessons

As climate change bites, bringing long, hot dry spells with temperatures we have never seen before and as access to water determines success or failure for all urban creatures, isn’t it time we come clean about the habitats we create and the creatures we claim to support?

This summer brought drought conditions to large parts of the UK. Surface-water puddles, ponds, ditches and streams dried up for days and weeks on end.

Imagine you’re a small shrew living in a bioretention zone in a large commercial park. Suddenly the soil is too hard to reach invertebrates. The flying insects are gone. There is no green vegetation. There is no water nearby and all the flowering plants have wilted. The habitat is no longer viable. Nothing can live there. Everything is dead.

Meanwhile, local people are grumbling about a hose-pipe ban and water companies are seeking ever deeper boreholes and permission to take more water out of the environment to meet our needs; fill our baths, water our begonias, wash our BMWs and cool our Labrador puppies.

How dare we pretend our desiccated SuDS are anything more than a sop to the planning authority to get homes built and offices erected. It’s time to be realistic about the habitats that SuDS really offer and the sustainability of the creatures that live in them.

We must design SuDS with year-round surface water, augmented by captured rainwater pumped up from below with solar pumps. Or bioretention zones that suck stored water up from below with wicking systems to keep the soil moist and the plants alive.

Maybe we can ask local residents to take water from their butts and to keep their SuDS alive. We must consider trickle-down systems for green-walls and linear devices. We must create cool, damp, dark places for small animals and insects to hide from the searing heat and to find soft soils and moisture.

It falls to us to provide reliable food sources for the pollinator species we love to promote on our showstopper SuDS schemes. But if the plants dry up and fail to thrive, they stop producing pollen and nectar leaving all of those precious pollinators high and dry.

Smarter systems

We can do this. We are awash with magnificent engineers who can design water-capture devices across their SuDS schemes, with solar pumps to move water to where it is needed when sunshine becomes fierce.

Innovators can create devices that design in their own water supply, so that they can thrive through drought. And our excellent ecologists can work with designers to imagine and describe how the creatures live and how to support them through the perils of climate change.

The ecologists will tell us, too, that the trees and shrubs should provide quiet, dark places that help our nocturnal friends to go about their business, for birds, insects and bats to scuttle about in the dark, seeking food and friends.

We must limit illumination of SuDS schemes in towns and cities. That means leaving them in the dark at night so that we can truly share them with nature. As every creature finds survival more difficult, as our summers become more brutal, we must make our SuDS more inviting to wildlife, more dense, more remote and apart from people.

SuDS shouldn’t be all about benches and beauty; we have enough space to enjoy our evenings without crowding out other species.

The trees along Fishergate in Preston City Centre are lit every night by cheery fairy lights. Although pretty, they are pointless. The lights prevent wild creatures hiding out in the leaves.

Everything about our designs is anthropocentric. We have to break that loop and think again. We must align designs to the needs of the local wildlife.

Designers must speak to local wildlife groups and read the local Biodiversity Action Plan. What species exist locally? How can you amend your SuDS plan to accommodate them, to help them to survive?

Is there a species of moth that requires a specific plant? What seeds do the local birds like to eat? Can you incorporate bat boxes for the local priority species? Or nest sites in your green wall?

Food for thought

It’s not good enough to do this with a broad brush – we need a calligraphy of creatures’ needs, creating niches, nooks and crannies for things to lurk in. I would even argue for including spider habitats in SuDS – but only from a respectful distance.

Finally, we must wonder who dines in our cities? I want to give a shout-out to the food crops and the provender from plants. There is no reason not to plant our SuDS schemes with fruit trees, fruit bushes, edible flowers and the strange, often unloved plants that insects love to lunch on.

Let’s hear it for the nettles and thistles! If we include foodstuffs for people and wildlife together, we can encourage youngsters to see opportunity in green spaces – not just as somewhere to play and get muddy, but as somewhere to share food with nature, taking home some pears and apples, leaving enough for rodents and butterflies to feast on.

We need to squeeze more out of our SuDS. We need to add another layer to the design process. And we need to revisit schemes at night to see whether we have really created a meaningful, magical, messy and marvellous place for creatures and critters to thrive in the heat of the day and fossick in the depths of the night.

Jo Bradley is director of UK operations at Stormwater Shepherds