Brief description

The objective of the study was to undertake a detailed flood study of the Clarence Town catchment
and establish models as necessary for accurate flood level prediction. Central to this was the
development of a two-dimensional hydraulic model of the floodplain.
In completing the flood study, the following activities were undertaken:
• Collation of database of historical flood information for the Clarence Town catchment;
• Acquisition of topographical data for the catchment including cross section and hydraulic
structure survey;
• Consultation with the community to acquire historical flood information and liaison in regard to
flooding concerns/perceptions and future floodplain management activities;
• Development of a hydraulic model (using TUFLOW software) to simulate flood behaviour in the
catchment;
• Calibration of the developed models using the June 2007, February 2009 and February 2011
flood events;
• Prediction of design flood conditions in the catchment using the calibrated models; and
• Production of design flood mapping series.
A good model calibration and validation was achieved with the available data, confirming the
appropriateness of the model for design flood simulation.
The local catchment flooding is typically characterised by a series of well-defined overland flow paths
that feed the main Town Creek channel prior to discharge to the Williams River. Given the relatively
small size of the contributing catchments, extensive flood inundation of property is somewhat limited.
Only three existing properties (all commercial premises) have been identified as at potential risk of
above floor flooding for events up to the 1% AEP flood magnitude.
The majority of the natural flood flow paths are through private land. In most part, development on
these lots has been located a sufficient distance from the natural drainage lines to limit potential for
building inundation.
The lower reaches of the Town Creek catchment are dominated by Williams River flooding. Typically
downstream of approximately the IGA culvert, the Williams River 1% AEP design flood results in
higher flood conditions than corresponding 1% AEP local catchment event. Accordingly, the Williams
River design flood conditions established by BMT WBM (2009) should be applied for future flood
planning and development control in these lower reaches.