Interactive Map

Project planning & design

The raingarden in the carpark at the Watershed Function Centre and Cafe, 665 Salisbury Highway, Mawson Lakes SA, was planned as part of the redevelopment of the City of Salisbury’s Wetlands Education Centre. The site was chosen to integrate with Kaurna artwork and other cultural and environmental features. A raingarden and a grassy swale were installed to improve the existing car park drainage and provide some pre-treatment of stormwater prior to it entering the adjacent wetlands. The wetlands are part of an extensive network of over 50 constructed wetlands and biofilters across Salisbury that cleanse stormwater run-off from the surrounding suburbs. Each year, this prevents hundreds of tonnes of litter, sediment and chemical pollutants from damaging Adelaide’s coastal waters.

It also facilitates Salisbury stormwater harvesting scheme, which provides cleansed wetland water to thousands of customers, including over 100 schools and sports grounds.

The aims of this City of Salisbury project for the Watershed site included:

• To upgrade the existing carpark drainage, including swales and rain gardens.
• To further engage Kaurna youth with a focus on natural management.
• To enhance visitor experience and increase use of the precinct by the local community, school groups, business and tourists.

WSUD features & design criteria

The result is a large bioretention raingarden in the shape of a rain drop. The design came from Kaurna input and the Council request for a roundabout to enable large school and commercial buses to safely deliver and pickup visitors at the site. Kaurna input to the design and selection of plants for the site was facilitated by two site workshops held during 2017.

Previously, stormwater from the carpark drained into the wetlands via a vegetated swale. This acted as a litter trap and had become an eyesore. Misguided attempts to landscape the area with mulch had blocked under-road drains. Now the specifically designed raingarden, with infiltration drainage layers and specifically selected nitrogen removing native plants, actively filters the run-off from the carpark before feeding the water to a low-maintenance grassy swale that feeds the water to the wetlands.

The raingarden demonstrates how stormwater runoff from roadways and car park can be partially treated through specifically selected infiltration layers and native sedges and rushes that are effective at removing pollutants. This pre-treatment, before the stormwater enters the wetland, helps reduce the pollutant load on the wetland, thus helping to achieve a very high water quality that is required for stormwater harvesting, storage and reuse. Note, the City of Salisbury undertakes extensive managed aquifer recharge (MAR) in the underlying confined sandy limestone aquifers in order to store the large volumes of harvested water and retrieves the water for irrigation during the long dry summers. MAR is an EPA licenced activity with very stringent water quality criteria.

The design of the raingarden was prepared by Dan French of French Enviro following Kaurna input at the two workshops. Construction adhered to the Rain Garden 500 construction guidelines of having specially selected layers of filter media (gravel, sand and planting layer) for the native plants to be planted into (refer to rain garden – typical cross section image).

Contact us to provide any new information or images for existing WSUD projects.