Since the Picton Flood Study Report, 1989 (Department of Water Resources), and subsequent Flood Plain Management Study (1992), there has been significant development in the Stonequarry Creek catchment. In 2006 Wollondilly Shire Council engaged Patterson Britton and Partners to update the previous studies using current hydrologic and 2D modelling techniques. This project involved a review and update of the 1989 hydrologic modelling (RAFTS) and the development of a 2D RMA hydraulic model, covering the same extent as the 1989 HEC-RAS model. A subsequent study by WorleyParsons (incorporating Patterson Britton and Partners) in 2008 investigated the impact of climate change on flooding in Stonequarry Creek. In 2010, Council engaged WorleyParsons to extend the 2D flood model upstream, and carry out a climate change assessment on the extended model network. This report aims to collate the methodology, results and conclusions from the various studies into a single, standalone document. As such, the key components of this report are:

1. Review and update of 1989 hydrology
2. 2D model development and comparison against the 1989 HEC2 model
3. Update of hydrology to provide inflows to facilitate extension of model upstream
4. 2D hydraulics for extended model network, including development since the 1989 study, and incorporation of the “stream clearing option” from the 1992 study, which Council advised has been implemented.
5. Climate change impact assessment