The NSW Department of Commerce (DoC) was commissioned by the Carrathool Shire Council with assistance from the Department of Environment and Climate Change (DECC formerly the Department of Water Resources) to carry out additional hydraulic modelling investigations to finalise the design flood levels and alignment for the Hillston Eastern Levee. DoC was commissioned by Council to undertake the detailed design and documentation for the proposed Hillston Eastern Levee. The main objective of the current study was to undertake additional hydraulic modelling to determine the alignment and crest level of the proposed Hillston Eastern Levee and any associated works required to mitigate against any adverse flood impacts. The key tasks involved:

1. Review all available data and information including “validating” the MIKE 11 model developed as part of the Flood Study, 2001 and the HEC-RAS model developed as part of the Urban Plan, 2005.
2. Prepare an updated MIKE11 model for the current study area based on “existing’ or “current” conditions.
3. Estimate design flood behaviour for “existing” conditions over the range of potential flood events (1990, 1% AEP and extreme flood).
4. Modify the MIKE11 model to represent the current levee alignment and crest levels and the Norwood Lane floodway and assess the flood impacts on ‘existing’ flood behaviour.
5. Assess a range of options to mitigate any adverse flood impacts identified in (4) above.
6. Recommend a proposed alignment and crest levels for the levee and any associated works.