Assessment of Coastal Compound Flooding in Tropical Catchment: Saltwater Creek Catchment in Australia

Compound flooding in coastal tropical cities is becoming increasingly prominent, driven by extreme rainfall events and sea level rise, under a changing climate. Quantifying the impact of these events is limited due to a lack of long-term data and funding and the need for advanced computational tools. To address this issue, this study employed a coupled one-dimensional (1D) and two-dimensional (2D) hydrodynamic model for the Saltwater Creek catchment in tropical north Queensland, Australia. In total, eight scenarios with compounding effects were assessed: four under the current climate (CC) and four under representative concentration pathway (RCP) 8.5. Under CC, the compound flooding event inundated almost 3% to 18% of the area conditions. This condition is further exacerbated under the RCP 8.5 climate change scenario, expanding the area flooded by 2% to 7% by 2090. The site experiences inundation up to 4.6 m at low-lying locations and extreme velocities up to 4 m/s at the upstream catchment with high flooding risk. The results suggest that this catchment requires an integrated approach to flood mitigation to meet the challenges posed by climate change, but careful consideration is required in interpreting the results. The results can be further improved by adopting higher-resolution and longer datasets for modelling, as well as considering land use change under the climate change scenarios.