Wallis Lake is located on the mid-north coast of NSW, about 120 km north of Newcastle. The twin towns of Forster and Tuncurry at the mouth of Wallis Lake form the urban centre of the region. There are also scattered commercial, tourist and residential developments along the extensive foreshores of the lake. Wallis Lake is a large tidal estuary with a waterway area of some 78 square kilometres. The lake has a catchment of some 1,200 square kilometres, which rises to its western boundary in the foothills of the Great Dividing Range. Flows entering the lake from surrounding river catchments (Wallamba River, Wang Wauk River, Coolongolook River and Wallingat River) discharge to the ocean through a permanent entrance channel.

The aim of this study was to determine the likely maximal water levels at a range of locations around the lake due to the combined effects of floods and wind waves. The 1 % AEP (Annual Exceedance Probability), 5% AEP and extreme design wind-elevated flood levels for Wallis Lake have been estimated. This determination takes into account the still water level, wave run up and wave setup from local wind waves, the bathymetry of Wallis Lake and the presence of any foreshore structures.