Nature in the City grant helps make an urban oasis

Chris came to the bush capital in 1972 to study ecology and he’s pursued his interest in environment throughout a 40-year career in the public service.

One day workmen came to clear the stormwater drain in his local park, as they had done many times before. Chris, with his knowledge of ecology and land management, started thinking about how the problem could be solved once and for all.

With the help of a Nature in the City: Cooling Your Suburb grant, Chris and his neighbours installed a series of swales in the park in August 2021.

Swales are shallow ditches that capture rainwater runoff. When combined with water harvesting trenches, swales hold water in the ground for a long time after the rain. They blend into the surrounding landscape and encourage natural irrigation.

Along with performing their intended role of reducing erosion and flooding, the Bragg Street Park’s new swales and trenches are home to a diverse range of plants and animals.

The challenge

“The Bragg Street Park is one of biggest parks in Hackett. The site was originally earmarked for housing in the 1960s but for some reason houses were never built. The park remained as natural grassy woodland,” says Chris, convener of the Bragg St Park Volunteers Group.

“After long dry periods the park used to become a dust bowl. Any rain that fell would run off the ground and into the storm water drain. The drain would become blocked with soil and then overflow, sometimes even flooding properties downhill of the park.

“I could see that if we didn't do something to reduce run-off in the park, the problems of erosion and flooding would just keep happening.

“Someone in the neighbourhood mentioned that swales might be a good solution, so we put it forward as a project for the 2020-21 Nature in the City grant funding.

“We started spreading the word and gaining the support of our neighbours. Then, we engaged Paul Barnett, a local architect with a particular interest in water sensitive urban design, to help.

“Paul worked with his long-time collaborator Paul Totterdell, from Sustainable Organic Solutions, to bring the vision to life. Both Pauls have designed and built similar swales together in many locations in the ACT,” Chris says.

The action

“Traditional urban infrastructure is all about shedding water as quickly as possible, but that’s an old paradigm. In Canberra, with our clay soils, water runs off the land and it’s dry again within a few days. When there are storms you get problems with flooding,” says Paul Barnett.

“A swale is essentially shaped earth that can hold and direct water. The aim of swales is to retain water – a precious resource – and improve the moisture content of the soil.

“While it’s the mound form of swales that we see on the surface, it’s what’s happening below that really matters. Behind the mound and hidden below the surface, there is a rainwater retention trench. It is about a metre deep and half a metre wide. The trench is filled with materials like rocks and sand which creates a space for water to permeate and flow through.

“Rainwater retention trenches mimic our alpine creek beds. Even when there’s no water visible on the surface, a subterranean aquatic environment persists. Paul Totterdell has dedicated much of his career to simulating this natural phenomenon in the built environment with swales and rainwater retention trenches.

“I and several other practitioners with a wide range of experience in urban design, ecology and placemaking, have collaborated with Paul over many years. We have contributed our thoughts and experiences as his theories and work processes have evolved. It’s only through many years of research, reflection, collaboration and iterative processes that Paul’s design for water harvesting systems could emerge.

“A swale by itself will hold water and slow erosion. But when you design a series of swales and incorporate rainwater retention trenches you multiply their benefits. This creates the right conditions to grow plants to create canopy. The canopy then cools the city through shading and evapotranspiration.

“Ideally swales are never without water harvesting trenches – they work hand in hand. They enable flora and fauna, like frogs, to survive long after the rains have passed.

“In the Bragg Street Park, the swales solved a problem of overland flow and flooding. But what they've also done is create a play space for the community, habitat for wildlife, and the foundation for a changed microclimate,” Paul says.

“Paul Totterdell bought his small diggers into the park and formed seven swales with rainwater retention trenches. After that, the community came in and prepared them for revegetation. Urban Parks provided woodchip for mulch. The plants were provided by Urban Parks, Urban Treescapes and members of our group,” says Chris.

“We’ve had a lot of rain since the swales were built, so the plantings are off to a good start. I’ve been surprised to see the number of eucalypts that have self-seeded. After the rains, we had hot weather which provided perfect conditions for germination. Some of these eucalypts are 1.5-2 metres high.

The benefit

“The look and feel of the park has really changed. People love the swales. The swales encourage nature play for people of all ages – even adults like to walk along the top of them! I think we’ll see more of cooling effect that swales can have as the plants grow.

“A side benefit of the project was that, with water in the swales and trenches, it created a perfect habitat for frogs. We’ve had one or two frogs in our backyard in the past, but to suddenly to hear the park alive with a whole chorus of frogs was amazing. We recorded five different species in spring 2023”.

“This project has shown how we can achieve great outcomes when we work with nature. If we seek to understand what’s there in the first place, then we can support nature to do what it does best.

“The project is also an example of collaboration between community and the government. Local residents bring on-the-ground knowledge that can help solve complex problems.

“The sense of achievement you get from completing a grant project is great. But it’s also important to think about the longer term – ‘how can I follow on from this?’. Hopefully what we’ve started will continue for many years to come.

"I walk my dog in the park in the evening, and if I see someone who seem interested in the swales I'll go and have a chat. It’s nice to get the positive feedback. People often say, 'the park’s looking fantastic', and it is."