Lake lllawarra is a shallow coastal lagoon located on the undulating coastal plain between the ocean and the cliffs of the lllawarra Escarpment. The Lake lllawarra Catchment has an area of approximately 270 square kilometres, rising from sea level to an elevation of 760m at Mount Murray. The catchment is largely rural, with some residential and commercial land uses located mainly in the lower catchment. Continuing development pressure on the lake foreshore has necessitated a study of lake flooding. The lake catchment is characterised by a low coastal plain, dominated by the western backdrop of the lllawarra Escarpment. The escarpment rises to a height in the catchment of 760m at Mount Murray, but more impressive is the slope of the escarpment, which rises over 400m over a horizontal distance of approximately 3km. The specific objectives of this study are to:

• Review design hydrology including PMP calculations
• Review the development and calibration of appropriate hydrologic and hydraulic models to define existing flood behaviour
• Review design flood levels, velocities and flow distributions for Lake lllawarra for the 50%, 20%, 1 0%, 5%, 2%, 1% AEP events and an extreme flood event for existing lake entrance conditions
• Define the extent of flooding for the 1 % AEP Flood for Lake lllawarra.