City of Sydney Raingardens

At the City of Sydney (FMA Member), the engineers in Technical Services developed a range of water quality components for the drainage network to meet ambitious Sydney 2030 water quality targets. One of the most innovative ideas is using small spaces in the city’s streets for decentralised water quality systems.

‘Online’ raingardens were introduced in 2008 to reduce the pollutants from surface runoff and have since been refined in design and construction. By June 2015 the City of Sydney has built 143 raingardens with a combined total area of over 2720 square meters.

The team’s studies showed many factors contributed to the health of these original online raingardens, but that hydraulic performance had the greatest overall influence. Other factors included catchment size, in-flow rates, plant types, raingarden size, terrain of the location and sun exposure.

To improve hydraulic performance the City’s Infrastructure Design Team shifted from the online concept and created ‘offline’ raingardens. Offline raingardens with a high-flow bypass were found to perform and maintain their appearance better than online systems.

Achieving an effective raingarden system in any urban area demands great effort in planning, design, construction and maintenance. However, raingardens are excellent water sensitive urban design components that can greatly reduce stormwater pollution.

For more information, download Hassan Narimani, Senior Engineer, City of Sydney's full paper Raingardens in Densley Developed Urban Areas provided to the 2016 IPWEA NSW State Conference.