Potential for forecasting inundation from flooding and storm surge: a case study of a small urban catchment during ex Tropical Cyclone Oswald. Takehiko Nose 1, Joanna M. Burston 1, Daniel Gee 1, and Rodger Tomlinson 1 1 Griffith Centre for Coastal Management, Griffith University, Southport, Qld, Australia;
[email protected] Abstract Forecasting inundation resulting from the dynamics of storm tide combining with freshwater flooding in estuarine environments and the behaviour of wave set-up in tidal inlets is complex yet important for effective disaster management. As part of a Griffith University project sponsored by the Queensland (Qld) State Government, a case study of a small urban catchment with a wave-dominated tidal inlet is used to investigate the potential for numerical modelling of such processes. Ex Tropical Cyclone (TC) Oswald, January 2013, generated freshwater flooding, storm surge and extreme wave conditions along eastern Qld coastline, causing extreme water levels in the case study site of Currumbin Creek on the Gold Coast. A field survey following this event combined with measured discharge, wave, and hydrographic data allows analysis of the hydrodynamic response of the system using numerical modelling. A numerical model built using DHI’s MIKE21 is used to simulate interactions between the riverine flood, storm surge and waves within the tidal inlet during the ex-TC Oswald event. In particular, the effect of possible wave set-up at the entrance on the tailwater level is investigated. We conclude that dynamical forecasting of inundation due to a combination of storm tide, extreme waves and freshwater flooding in such environments requires detailed inputs, including accurate discharge, tailwater levels and up-to-date bathymetry.