The objectives of the Flood Study are to: • Identify all the flood-related data by searching all relevant data sources. • Determine the likely extent and nature of flooding and identify potential hydraulic controls by carrying out detailed site visits of the study area. • Define existing catchment condition flood behaviour for mainstream flooding in the catchment with due consideration to the impact of Lake Macquarie levels on flooding characteristics. • Define design flood levels, velocities and flow distributions for the catchment. • Define the extent of flooding for the 200 year, 100 year, 20 year, 10 year and 5 year ARI floods and Probable Maximum Flood (PMF) for the catchment. • Define Provisional Flood Hazard for the flood-affected areas. • Define the Hydraulic Categories for the flood-affected areas. Two numerical modelling tools were developed: • A hydrologic model to convert rainfall on the catchment into runoff. The hydrologic model combines rainfall information with local catchment characteristics to estimate runoff hydrographs. • A hydraulic model to convert runoff hydrographs into water levels and velocities throughout the study area. The model simulates the hydraulic behaviour of the water within the study area by accounting for flow in the major channels as well as all the potential overland flowpaths, which develop when the capacity of the channels is exceeded. It relies on boundary conditions, which include the runoff hydrographs produced by the hydrologic model and the appropriate downstream boundary level from Lake Macquarie.