Green infrastructure to cool western Sydney

The hottest and driest part of Greater Sydney will be smarter, cooler and greener under a new approach to planning and development led by Sydney Water.

The Western Parkland City, the biggest and most ambitious city build project in Australian history, will be a future-focused smart city built from the ground up. With 1.5 million people expected to move west of Parramatta by 2056, the Parkland City is set to become an economic powerhouse, a hub that integrates industry with community.

This burgeoning area of Greater Sydney will see the development of new neighbourhoods, complementing the nearby established centres of Liverpool, Penrith and Campbelltown. These areas are among the hottest and driest parts of Sydney and building cool, green and resilient neighbourhoods requires a new approach to managing water.

Wianamatta Urban Typologies and Stormwater Management report

Sydney Water, in partnership with leading architects, engineers and urban designers, is testing an innovative new approach that integrates urban design, planning and sustainable stormwater management, with the aim of holding as much water within the urban footprint as possible.

This approach will provide effective drainage and flood mitigation, as well as address broader objectives like urban cooling, greening, environment protection and recreation. The smart planning techniques outlined in the Urban Typologies and Stormwater Management report will guide urban development in Western Sydney, ultimately reducing temperatures by 4.6 degrees.

The report will help influence the design of buildings, open spaces, streetscapes and green corridors to deliver a true Parkland City.

Cooling actions such as permeable surfaces that allow for natural infiltration of water; using tanks, wetlands and green roofs for holding and treating water; and larger scale stormwater harvesting schemes built into the precinct will repurpose large volumes of rainwater and stormwater for irrigation, water in the landscape or agricultural uses.

An abundance of street trees will create a natural canopy in the Parkland City. A ‘Wianamatta street tree’, designed specifically for Western Sydney, will be passively irrigated through the street stormwater drainage system, capturing and reusing stormwater and contributing to the health and longevity of street trees under hot, dry conditions.

Modelling of these cooling actions shows the number of extreme, very strong and strong heat-stress days per summer decreases dramatically from 47 to 19 days.

Case study precincts

To explore the extent to which the urban environment can retain stormwater, a series of urban typologies were developed depicting roads, open space, subdivision patterns and built form at a block scale. The typologies cover a range of commercial, industrial and residential developments and are intended to be used as tools in the strategic planning of Western Parkland City.

To determine the effectiveness of integrated urban form and stormwater design, 3D models of two case study precincts were developed.

Performance was measured and compared with a business-as-usual approach. The key outcomes of the integrated design approach include:

• Surplus run-off reduced by some 75 per cent
• Open space increased by between eight-ten per cent
• Three times more canopy cover
• Potential reduction of volume of stormwater detention in basins
• Doubling of days with no thermal heat stress (2055)
• Reduction of four-five degrees in maximum temperature on an extreme heat day (2055)

Water, the heart of the city

The NSW Government’s vision of A Metropolis of Three Cities – Eastern Harbour, Central River and Western Parkland – puts water at the core of the identity of each city.

The Eastern City boasts Sydney Harbour, the Central City has Parramatta River at its heart, and the Parkland City has Wianamatta-South Creek and its waterways as its central defining feature.

Unlike the ever-present open water of the Eastern and Central cities, water in the Parkland City is seasonal. Wianamatta – a Dharug name meaning ‘mother’s place’ or ‘mother’s creek’ – is the longest freshwater, ephemeral waterway in Sydney. Its creek beds are sometimes dry, with water ponding in subtle depressions and pools.

Agricultural activity in the area has left a legacy of thousands of dams that provide a more permanent sense of water in the landscape.

The challenge of stormwater run-off

The unique characteristics of Wianamatta-South Creekand its waterways makes them vulnerable to the impact of urbanisation. Excess stormwater is a key challenge for urban planning in this environment, with development and urbanisation expected to increase the volume of run-off reaching the waterways by up to six times.

The traditional approach drains excess stormwater from the urban environment as quickly as possible to protect health and safety, and mitigate potential flooding of buildings and infrastructure. This is usually done by directing stormwater through engineered pipes and channels into local waterways.

Adapting this approach in the Parkland City would be problematic, leading to the degradation and decline of the Wianamatta waterway systems. The approach trialled by Sydney Water and its team of experts will hold enough stormwater within the urban environment, ensuring the sustainability of Wianamatta-South Creek as the catchment is urbanised.

Importantly, the innovative approach will preserve the values that are central to the identity of the future Parkland City.