An evidence based approach to evaluating flood adaptation effectiveness including climate change considerations for coastal cities: City of Port Phillip, Victoria, Australia

Coastal cities provide a modelling challenge as surface flow is strongly affected by urban drainage networks and there is interaction between coastal and inland flooding. We present a graphics processing unit (GPU)-based hydrodynamic model coupled to a hydraulic network that integrates adaptation analysis in the context of current and future flooding. The hydrodynamic model is based on a finite volume implementation of the shallow water equations formulated for overland flow. The hydraulic network is based on a pressure relaxation method, and uses a GPU-based sparse matrix solver for computational speed. The integrated model is used for modelling potential combined coastal and catchment inundation and climate adaptation analysis for the City of Port Phillip, Victoria, Australia. The key outcome from the adaptation study was that resources spent towards adaptation infrastructure should be investigated in the context of sea level rise (SLR) at least for the next 50 years. The adaptation analysis identified "a tipping point" beyond a SLR of around 0.4 m (expected in the next 30 years) where conventional adaptation approaches will fail. This outcome has resulted in the City realising that significant changes in infrastructure for the region will be necessary rather than just incremental adaptation approaches to deal with future flooding.