The greater Macquarie Rivulet catchment incorporates a number of creeks including, Albion Creek, Frazers Creek and Marshall Mount Creek. The catchment drains an area of 110km2 and includes the suburbs of Albion Park, Calderwood, Tongarra and Yellow Rock. The catchment elevations vary from 770 m AHD to almost sea level and ultimately discharging into Lake Illawarra. There have been several recorded instances of flood producing storms in the catchment including November 1961, June 1975, February 1984, June 1991 and March 2011.

Large parts of the catchment remain rural, with urban development concentrated around Albion Park. The catchment also contains major infrastructure such as the Illawarra Regional Airport, Princes Highway and proposed upgrades and Illawarra railway line. The catchment represents a complex system of rural environment riverine flooding, urban catchment flooding, large event cross catchment flooding and tidal interactions.

WMAwater have been engaged by Shellharbour City Council to undertake a Flood Study for the Great Macquarie Rivulet catchment. As urbanisation and development continues, the ability to effectively manage flood prone lands will be dependent on an accurate assessment of existing flood conditions upon which to base future floodplain management decisions. It is therefore important that appropriate tools and information to assess flood risk are available to Shellharbour City Council for planning purposes.

The main objectives of the study require the following to be undertaken:

  • Consider of historical flooding including catchment conditions and complex recorded rainfall patterns over the relatively large catchment;
  • Develop of a computer model to assist in the definition of the nature and extent of flooding for historical, current and future conditions (development and climate change);
  • Derive information to assist Council in making effective investments in future floodplain management and floodplain development, and;
  • Derive information to inform emergency response organisations of the existing and potential future flood risk.

Complex hydrologic and hydraulic models of the study area have been developed in order to achieve the project objectives.