Stream restoration at Johnstons Creek

The challenge: Stormwater channel restoration and rehabilitation

Johnstons Creek, a concrete lined stormwater channel at Rozelle Bay, Sydney, was due for repair and upgrade as the invert and channel walls were deteriorating.

Instead of just relining the channel with more concrete, Sydney Water Corporation and Thompson Berrill Landscape Design saw potential to adapt the channel. They wanted to find an innovative way to make it more aesthetic, environmentally friendly, and sustainable – and provide a habitat for many species of aquatic marine life.

The project was awarded based on a Design and Construct Tender submitted by Diona Civil Contractors, who approached Royal HaskoningDHV as an experienced partner to carry out design and provide technical support during the construction phase. The design called for the concrete lined channel to be transformed into a meandering, rock-lined stream with salt-marsh benching that would provide a extensive increase in habitat for estuarine and marine life to thrive.

The solution: Designing a channel for local wildlife and the community

Diona enlisted Royal HaskoningDHV on the project based on our proven track record working on stormwater-related projects together before.

We undertook flood modelling to optimise the functionality of the stormwater channel. After demonstrating through modelling and calculations that the proposed sandstone blocks would be stable during a flood, and that the increased channel dimensions would provide additional flood benefit, we carried out detailed design of the preferred works.

A key part of Johnstons Creek’s restoration was to enhance habitat for plants, animals, and provide an attractive park for the local community around the stream. We also needed to consider the impacts of our work on an active light rail viaduct operated by Transport for NSW.

To ensure our design benefited the community –a key outcome was to make the stream beautiful and introduce seating, signage, and paths on both sides of the channel for cycling and walking, including the design of a new shared path bridge across the channel to enhance pedestrian and cycle connectivity. And we introduced salt marshes along the banks of the creek to create new habitat and encourage more biodiversity.

The result: Flood protection and habitat for Rozelle Bay

The stream is now fully operational and will more effectively convey floodwater from the surrounding urban environments. The construction materials chosen have been successful in enhancing biodiversity and aquaculture, as well as providing an accessible and aesthetically pleasing environment, to attract users to the park.

The intricately patterned sandstone low flow channel and walls created a naturalistic, beautiful place for the community to visit and spend time – as well as creating more space for marine life to thrive in, including intertidal rock pools. And the creek itself provides habitat for many species of marine life and wading birds.