The Study Area

The study area comprises four sub-catchments within the Canterbury-Bankstown Council Local Government Area (LGA) that drain to Prospect Creek:

• Georges Hall Sub-Catchment: Covering approximately 145 hectares, this area predominantly features residential land with notable reserves, such as Crest Reserve and Garrison Point Reserve.
• Lansdowne Sub-Catchment: Spanning 243 hectares, it includes residential areas alongside significant bushland and parklands, such as Lansdowne Park and Mirambeena Regional Park.
• Miller Road Sub-Catchment: Covering 50 hectares, this area includes residential zones with no defined water channels, relying on overland flow paths and a piped drainage network.
• Villawood Sub-Catchment: The largest at approximately 740 hectares, this area comprises residential and industrial zones with a network of concrete-lined open channels.

A map of the study area is shown in Figure 1-2.

Consultation

Community and stakeholder consultation has been integral to this project. Key consultation activities included:

• Engagement with the Floodplain Management Committee throughout the project phases;
• Community feedback collected through online surveys, email submissions, and in-person sessions, with a total of 67 recorded responses during initial consultation;
• Public exhibition of the draft study and plan, incorporating input from 57 engagements; and
• Targeted discussions on identified issues, such as voluntary house raising and stormwater management concerns.

Modelling of Flood Behaviour

Canterbury-Bankstown Council has implemented a consistent and advanced approach for modelling stormwater catchment flooding. The methodology integrates a dynamically linked 2D/1D hydrodynamic model (TUFLOW), which simulates flood behaviours with precision.

The TUFLOW model uses a two-dimensional grid to represent surface terrain while incorporating one-dimensional elements for stormwater pipes and channels. Overflow from drainage elements is accounted for, allowing flows to spill onto the grid and replicate overland and sheet flows across floodplains.

Flood Risk Mapping & Development Controls

Flood risk mapping for the Prospect Creek sub-catchments categorises the area into three flood risk precincts, guiding development controls:

• High Flood Risk Areas: Areas prone to significant flood damages and evacuation challenges, where development is generally restricted.
• Medium Flood Risk Areas: Zones with moderate risk, where damages can be mitigated with suitable controls.
• Low Flood Risk Areas: Regions with minimal risk where most developments are permitted, subject to planning regulations.

Additionally, overland flow precincts have been identified to account for shallow inundation areas, enabling tailored development controls.

The Flood Problem

A comprehensive flood damages database was developed to evaluate flood impacts and inform flood mitigation strategies. Key findings include:

• Approximately 2,667 properties are impacted in the Probable Maximum Flood (PMF) event, with over 60% located in the Villawood sub-catchment.
• Average Annual Damages (AAD) across the sub-catchments exceed $93.7 million, with the Villawood sub-catchment contributing a significant portion due to its low-lying industrial areas.

Flood mitigation measures were assessed, and recommendations for effective floodplain management have been outlined to address these challenges.