The Peach Tree and Lower Surveyors Creeks Flood Study covers an area of 1,250 hectares within the Penrith City Council Local Government Area (LGA). As shown in Figure 1, the study area extends across parts of the suburbs of Penrith, South Penrith and Jamisontown. The study area occupies the lower part of a larger 2,450 hectare catchment that originates in the Glenmore Park area and ultimately drains into the Nepean River just west of Penrith. Penrith City Council outlined a range of objectives for the Peach Tree and Lower Surveyors Creeks Flood Study. This included:
- to review available flood-related information and historic flood data for the catchment;
- to consult with the community to gain an understanding of flooding and drainage ‘trouble spots’ and gather information on past floods;
- to undertake a detailed survey of the creeks, open channels, bridges and culverts;
- to develop a computer-based hydrologic flood model to simulate the transformation of rainfall into runoff
- to develop a computer based hydraulic model to simulate the movement of runoff across the catchment;
- to calibrate and validate the computer models against observed information on past floods;
- to use the calibrated and validated computer models to estimate peak discharges, water levels, depths and velocities for the design 20%, 10%, 5%, 2%, 1%, 0.5% and 0.2% AEP floods as well as the 0.5 exceedances per year (0.5EY) flood and the Probable Maximum Flood (PMF);
- to verify the design flood results against other studies as well as the experiences of residents and business owners in the catchment;
- to produce maps showing predicted floodwater depths, levels and velocities for the full range of design floods;
- to quantify the capacity of the existing stormwater drainage system;
- to produce maps showing flood hazard and flood function (i.e., hydraulic categories) for the 5%, 1% and 0.5% AEP floods and the PMF;
- to produce emergency response precinct classification mapping to assist the State Emergency Service with emergency response planning;
- to quantify the potential impact of climate change on existing design flood behaviour;
- to quantify the potential impact of future development on existing flood behaviour
- to provide information to assist with land use planning activities;
- to develop a list of preliminary flood mitigation options; and
- to map the flood planning area and preliminary flood control lots.