This Flood Study Review details the updating of the hydraulic modelling approach for Wallis Lake, in accordance with the NSW Floodplain Development Manual (Reference 1), from that undertaken in the 1989 Forster/Tuncurry Flood Study (Reference 2). The hydrologic modelling approach was not updated and uses the same WBNM hydrologic model. The main reasons for updating the hydraulic modelling approach are as follows:

• the use of a two Dimensional (2D) hydraulic model,
• availability of detailed bathymetric data to better describe the bed of Wallis Lake rather than the use of cross sections,
• availability of Airborne Laser Scanning survey that provides a very accurate definition of the topography of the floodplain,
• a more detailed appraisal of design ocean level conditions,
• the incorporation of an “envelope” approach based on the maximum of an ocean dominated event and a runoff dominated event,
• a rigorous review of the available historical flood level data was undertaken to “explain” the reasons for the relatively high recorded levels for the April 1927 event compared to those recorded in the last 25 years.