Rising sea levels are placing more coastal assets at risk from inundation. To date, a static inundation approach referred to as the ‘bathtub’ model has been used to investigate the coastal regions and infrastructure at risk from overland flooding due to storm tides (the combination of atmospheric-driven storm surge and astronomical tide) and rising sea levels. The bathtub approach suffers the disadvantage of; (1) not accounting for the time dependence of coastal flooding and hence the duration of flood events and (2) considering only the overland inundation and not potential inundation that can occur due to backwater effects within underground drainage networks. CSIRO’s DATA61 group have developed the CFAST modelling tool to address these shortcomings and in collaboration with CSIRO Oceans and Atmosphere are developing the capability to enable coastal practitioners to more realistically model the impact of sea level rise and storm tides on inundation.

Extreme value analysis of storm tide water levels provide a design height for inundation studies. These extreme water levels can be added to the projection of changes in global mean sea level to investigate future extreme water levels. For dynamic modelling of inundation, a time series (not a single height) of water level is required to force the hydrodynamic model boundary. In this study we demonstrate and evaluate the impacts arising from differently constructed extreme water level boundary condition scenarios of surge and tide and use the CFAST hydrodynamic model to simulate the dynamic inundation. The CFAST model is aimed to assist coastal councils investigate the location and duration of the local impact of sea level rise on the extreme inundation events of coastal assets.