Comparing static and dynamic flood models in estuarine environments: a case study from south-east Australia

Static and dynamic flood models differ substantially in their complexity and their ability to represent environmental processes such as storm tide or riverine flooding. This study analysed spatial differences in flood extent between static (bathtub) and dynamic flood models (Delft3D) in estuarine environments with different morphology and hydrodynamics in order to investigate which approach is most suitable to map flooding due to storm surges and river discharge in estuarine environments. Time series of observed water levels and river discharge measurements were used to force model boundaries. Observational data, such as tidal gauge and water level logger measurements, satellite imagery and aerial photography, were used to validate modelling results. Flood extents were calculated including and excluding river discharge to quantify and investigate its effect on the mapping of flooding. Modelling results indicate that the mature estuarine system, which has largely infilled broad flood plains, requires a consideration of bottom friction and riverine discharge through dynamic modelling techniques, whereas static models may provide an alternative approach to map flooding at low cost and low computational expense in young lake-like estuarine systems that have not been infilled with sediments. Our results suggest that estuarine classifications based on geomorphological characteristics can potentially guide flood risk assessments in estuarine environments