Rain gardens provide cleaner water through design

Construction resumes in Bridgeland-Riverside after floods

Pale yellows dark oranges and deep purples enrich a residential greenspace in the northeast community of Winston Heights-Mountview but what many visitors to the neighbourhood may not realize is that these plants serve a more important function than just eye-catching landscape.

In 2011 the City of Calgary finished the construction of two rain gardens in Winston Heights-Mountview and are currently building two more in Bridgeland-Riverside as part of a pilot project to manage the level of sediment entering rivers from Calgary’s storm drainage system.

Rain gardens are designed to help pool rain and melted snow to filter out silt solids chemicals and bacteria through plants and soils before it enters creeks and rivers. “Most of the water that rushes into Calgary’s storm drains goes directly to the river untreated” says Catriona Laird public program co-ordinator with the City of Calgary.

The land is first excavated to make it concave then planted with hardy low-maintenance water-wise plants using engineered soils that absorb and naturally filter the stormwater. According to the city’s website properly constructed rain gardens are designed to allow overflow in a large rain event and hold standing water for no more than 72 hours.

Keith Hlewka planning director at the Bridgeland-Riverside Community Association says sustainability of the land and water was a huge draw for the community when they were first approached about the idea.

“I think the most exciting part of the project is the fact that instead of diverting water from a parking lot into our sewer system the water is now maintaining a garden in our community” says Hlewka.

Construction on the Bridgeland rain gardens was originally set for June but was delayed by the flooding — and that’s not a problem the gardens can solve on their own. Laird says the gardens are designed to not only collect excess stormwater but also to reduce the amount of stormwater entering the storm drainage system at one time. “They will help with very localized flooding but for it to have a larger impact on the city we need to have more of them” she says.

Laird says that the city worked with both communities to gain feedback on the design elements that were most important to residents. The rain gardens in Winston Heights-Mountview she says reflect a more natural foothills design. In Bridgeland-Riverside residents wanted amenities that would allow them to gather within the garden and enjoy the space including a small bridge a bench a pergola and a garbage can and the garden will have more grasses than flowering plants.

“The great thing about rain gardens” says Laird “ is that they can be designed to complement the surrounding area and the landscaping can accommodate a number of different styles.”

Bridgeland-Riverside is home to numerous community gardens and Hlewka says the community has “a long history of being the gardeners of the city.” But he adds that the rain garden “is more about participation with the garden aesthetics” than it is about the act of gardening.

“Until this year the area where the rain garden is was just essentially a passive piece of grass underneath some trees” says Hlewka. “So now it will actually be a textured landscape with a variety of different native species.”