An innovative approach to stormwater management by Wallbridge Gilbert Aztec for the Newenham development on Mount Barker’s urban fringe, received the Minister’s Award for Excellence in Sustainable Water Management at the Water Industry Alliance Smart Water Awards held on 7 July 2017.
Growth areas in Mount Barker will generate an additional 4 GL of stormwater by 2040, according to the region’s Integrated Water Management Plan. If not managed sustainably, this excess stormwater stands to destroy the urban streams that form part of the character of the township. Increases in imperviousness of our urban areas vastly reduce infiltration of rainfall into the soil profile depriving local streams of base flows.
Newenham has set a new benchmark for greenfield development by incorporating small-scale wetlands or ecological sponges to manage frequent flow events up to the 1.5-year average recurrence interval (ARI). These design features will protect the integrity of Western Flat Creek by managing the smaller, frequent flows that are responsible for stream formation.
“The stormwater management plan challenges the notion that wetlands need to hold permanent water for aesthetic purposes,” stated Wallbridge Gilbert Aztec‘s lead designer, Joe LaSpina. “These systems are designed with wetting and drying cycles to infiltrate and lose water to contribute to base flows. Most importantly, this strategy aims to reduce the direct connection of impervious areas to the stormwater network, and hence the stream.”
The living systems within this 1500 allotment development that will contribute to habitat, biodiversity and environmental values along Western Flat Creek include wetlands, and biofiltration basins, designed for infiltration, and with low flow (sub surface release) to the creek. Many roadways, including the boulevards adjacent to the creek, have one-way cross fall with no kerb on the low-side to enable stormwater runoff to sheet flow to verges and swales, prior to reaching the creek, to aid pollutant removal and promoting infiltration. In conjunction with these WSUD assets, the creek will undergo restoration works incorporating pool and riffle sequences at key locations throughout the site.
The developer, Burke Urban, has worked in close collaboration with David Lawry of TreeNet to adapt the standard TreeNet inlet design to suit a rollover kerb, while increasing the soakage well storage capacity to 350 L.
Kym Burke, Managing Director, Burke Urban explained why his company has invested in stormwater and wastewater innovation within their developments over the past 25 years: “Sustainability for us means being practical and commercial, whilst achieving a community, environmental and marketing triple bottom line outcome. These awards for excellence in this field recognises the commitment to these outcomes and reward for effort and innovation by our team.”
Burke Urban should be congratulated for embracing a stormwater strategy that shows leadership in best practice water sensitive urban design – design that will sustain the ecological function of Western Flat Creek, ensuring that the community can enjoy a high-quality living stream now and into the future.
Images: Burke Urban and Wallbridge Gilbert Aztec