Identification of areas exposed to storm-tide inundation is of importance for coastal flood risk management. In June 2016 the coincidence of a storm surge with a high spring tide caused severe inundation across the coast of NSW. Settlements in low-lying areas of estuarine environments were particularly at risk due to the potential enhancement of extreme water levels by riverine flooding. Traditional flood risk assessments do not account for the latter driver, even though the degree of impact on flood extent can vary with the catchment size of an estuarine environment. This study compares flood extent generated from static ("bathtub") and dynamic (Delft3D) modelling approaches in two wave-dominated barrier estuaries (Shoalhaven Estuary and Lake Illawarra) at different stages of infill, tidal modification and catchment size. Observed water levels of the June 2016 storm surge were used to force the models, whereas observational data such as satellite imagery, aerial photography, tidal gauges and water level logger measurements were used to validate modelling results. Modelling differences in flood extent between the two approaches were smallest in Lake Illawarra (0.2 km²), where riverine discharge appeared to be negligible. At the Shoalhaven estuary modelling differences were larger (11 km²) and the consideration of river discharge through dynamic modelling techniques was shown to be crucial for the modelling of observed water levels and flood extents, because storm-tide inundation and riverine flooding appeared to coincide. In conclusion, results show that the static "bathtub" modelling is an efficient management approach to map flood extent at low cost and low computational expenses in wave-dominated barrier estuaries at youthful/intermediate stages of infill and similar catchment area (<1000 >km²) to Lake Illawarra, such as Lake Macquarie or St. Georges Basin.