by Lulu Shen, Communications Officer, Georges River Council
An award-winning environmental restoration improvement project in Georges River has changed our perspective of stormwater, to a resource rather than a problem. By creating a beautiful, natural landscape and supporting wetlands as a filter, the project has reduced water pollution and developed sustainable water use practices.
In the fast rate of global urbanisation, stormwater and green infrastructure are now a significant focus to provide sustainable solutions to the problems that major cities face.
Building intelligent and efficient ways to utilise water, as well as constructing and preserving wetlands can bring us great environmental and economic benefits.
Professor Tim Fletcher from Melbourne University said during an interview with ABC, “In a natural environment, around 80 per cent of rainfall is evaporated into the atmosphere and digested by vegetation; but in an urban setting, 90 per cent of the rainfall runs straight into the drainage system.”
An award-winning environment improvement project in Georges River has changed our perspective of stormwater, to a resource rather than a problem, by creating a natural landscape with wetlands as a filter, to reduce water pollution and encourage sustainable water use practices.
Gannons Park, which reaches down to Lime Kiln Bay of the Georges River in Sydney’s south and comprises the eastern boundary of the suburb of Lugarno, has an inspirational history of restoration work.
An historical document from Pocket Guide to Sydney recorded that, “in the early 1900s, the land was the depot for Peakhurst Heights, where they buried the nightsoil, before the area was connected to sewerage system”.
It was then gradually developed into a scenic 35ha patch of green from 1964, with eight sports fields and a combination of remnant bushland and open parkland.
In 2020, Georges River Council committed close to $12 million (including funding secured from the Federal Government and the New South Wales Government) for the Gannons Park Water Quality Improvement and Stormwater Harvesting Scheme.
The large-scale landscape and stormwater treatment project focused on on-site stormwater harvesting, reinstating a section of Boggywell Creek including natural waterway features such as swales, wetlands, ponds and bioretention systems.
The project has since won the Award for Excellence in Integrated Stormwater Design at the Stormwater NSW 2021 Awards with Stormwater NSW noting that, “the site demonstrates a very good example of how this style of design can enhance a community’s resource – an excellent work in integrated stormwater management.”
What does the project aim to achieve?
The Gannons Park Water Quality Improvement and Stormwater Harvesting Scheme aims to use landscape architecture and engineering infrastructure to support both the improvement of stormwater quality and the management of this water as a valuable resource, by the below methods, according to a Hurstville Council report:
∞ Substituting potable water with non-potable recycled stormwater for irrigation of sports fields
∞ Reducing pollutants discharging into the Georges River by providing stormwater quality treatment
∞ Enhancing biodiversity and aesthetics through the creation of a water body wetland
∞ Reinstating a former water course through the park via the introduction of swales along the length of the park to the foreshore of the Georges River
The report also states that, “the project saw the introduction of vegetated walkways, boardwalks and bridges spanning over the ponds and wetlands and extensions to the shared cycleway and walking path.
“These enhancements linked and reactivated the lower, lesser-used areas of Gannons Park, thereby creating a new identity for this important regional park.”
The project enabled on-site stormwater collection, diversion and treatments, reused from the underground culverts to the surface, and created swales, wetlands, ponds and bioretention systems.
What are the benefits of the design?
The project will see the reduction in potable water usage, through the harvesting and treatment of catchment stormwater. 26 million litres of water is anticipated to be harvested each year to replace potable water use in this one public park alone.
Through the integration of the stormwater treatment system and naturalisation work, Council has improved the biodiversity and opportunities for passive recreation on site. The constructed ponds store the water for reuse on-site along with reestablishing aquatic and riparian habitats in their historic location.
Georges River is a regionally significant and highly valued waterway in the Sydney Metropolitan area. More than 16,000kg of polluting chemical debris is anticipated to be removed annually by stormwater wetlands, leaving the precious waterways of the nearby Georges River cleaner.
This water quality improvement work has resulted in enhancement of aquatic and terrestrial environmental habitats within Gannons Park. Over time, there will be an increase in biodiversity and habitat complexity through the natural features used to treat the stormwater and subsequent naturalisation works.
There will also be predicted longterm and broader benefits than those directly on site, including: introduction of more than 41,000 new native plants to enhance the biodiversity and habitat value of the park; the reduction in heat island effect, improved air quality and improvement of excess stormwater entering the Georges River.
Flooding and drainage control
The design includes a series of wetlands, swales and bioretention features which treat the water as it flows through the system.
These key features slow stormwater streams and allow drainage of overland flow. The new system, which replaced an underground culvert, assists with the prevention of upstream back up due to the limiting capacity of underground culverts.
The construction of dynamic open spaces is a key hallmark of livability in urban areas. Georges River Council recognised the value of Gannons Park as a significant recreational and green space within the increasingly urbanised setting.
The project improved Council’s ability to maintain public sporting fields to a high standard whilst the stormwater improvement work increased the accessibility, useability and quality of the natural environment through meandering pathways, green walls, raised pedestrian bridges and improved biodiversity.
Adaptation to climate change
Climate change will see the frequency and intensity of weather events change. This system will assist during peak rain events through the flood mitigation features whilst the retention and treatment system will allow the reuse of water on the adjoining sport fields.
This on-site reuse will reduce the impact on potable water sources during drought events. This best-practice approach also enables Georges River Council to evolve as technology improves to progress environmentally sensitive reuse aspirations, assisting Council to meet a target of net zero emissions by July 2025.
The growth in Australia’s urban space and increased weather events due to climate change means there will be larger volumes of stormwater available.
Over the years, understanding of wetlands and stormwater has grown, as has appreciation for their contributions to the local environment.
The improvements to Gannons Park have set an example for us to change the way we think about water, create innovative means for it to work with us, and become a resource for us.
The park is now vital for local pollution control, water efficiency and flood buffering. It has truly become an urban oasis for families across the Georges River area and keeps the neighbouring Lime Kiln Bay, Boggywell Creek and many tributaries of the Georges River clean for years to come.