Green Square: Enabling Urban Renewal Through Effective Flood Risk Management
Annual Conference
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The Green Square urban renewal area in Sydney, New South Wales is Australia’s largest urban renewal project delivering significant economic benefits, including 31,000 residential dwellings housing 60,000 new residents and catering for a permanent workforce of 21,000. Total development costs are forecast to exceed $16 billion.
The Green Square Town Centre is located at the heart of this urban renewal area. Prior to European settlement, this area was part of a series of ponds, swamps and creeks that drained through to Botany Bay. Urbanisation changed the hydraulic character of the area, from a natural water reservoir and waterway corridor to an area of hazardous flash flooding. As old industrial land gives way to modern high-density development, existing flood hazards needed to be resolved to protect a growing community.
The preferred solution involved the installation of 2.5km of new conduits specifically to reduce high hazard flooding to low hazard in the 1% AEP. The project presented many technical, logistical and community related challenges from solving complex hydraulic issues to installing large conduits in heavily built-up areas with extensive existing services clashes and potential major traffic disruption. The trunk drain, now substantially complete, interacts with the local sub-surface drainage system and the ground surface therefore requiring extensive 1D and 2D hydraulic modelling as well as Computational Fluid Dynamics (CFD) and physical modelling of local drainage inflow structures, to ensure the finished system would meet the project objectives. To meet the construction challenges, minimise the social impact and minimise cost, the Drying Green Alliance (consisting of City of Sydney, Sydney Water, WSP, UGL, Seymour Whyte and RPS) adopted a design and construction method that used tunnel boring machines to install 1800mm diameter pipes in long runs (known as micro-tunnelling) well below street level.
This is a complex project that is critical in eliminating the high-hazard flooding from the area to deliver a liveable urban renewal of this inner-city area. It is being delivered through the cooperation of local and state government, construction contractors and designers through an alliance framework. The most beneficial and cost-effective infrastructure is being built because of the thorough planning process and rigorous hydraulic modelling that has been undertaken, both as part of developing the reference design and by the alliance designers in optimising the final design. Innovative construction methods and a collaborative approach will help to nurture the thriving communities and reap further economic benefits.
Highlights of the project include: