This report describes a detailed assessment of coastal vulnerability and infrastructure exposure undertaken for Mandurah local government area (LGA) to complement the analyses in the National Coastal Risk Assessment. The assessment modelled both storm surge and coastal recession. The hydrodynamic storm surge modelling conditions were based on those observed during TC Alby (1978) and included scenarios with the storm track shifted to create maximum impact of the wind field on Mandurah, and sea-level rise scenarios from 0.0 m (current climate) to 1.1 m. Potential shifts in the shoreline position were modelled based on changes in the sediment transport regime under sea-level rise. The resulting inundation from the modelled surge and erosion event was projected onto the coastline to give impact 'footprints' for each event. These footprints were overlaid with built asset data from Geoscience Australia's National Exposure Information System (NEXIS), as well as road, railway and bridge infrastructure. The storm modelling exposure analysis found that if the 1978 Tropical Cyclone Alby storm were to directly impact Mandurah LGA today then approximately 560 buildings are exposed to storm-tide inundation. This exposure increases to nearly 3,000 buildings when factoring in a rise in sea level of 1.1m by 2100. Within the area modelled to be potentially subject to erosion due to sea-level rise by 2030 there are between 140 and 800 buildings. However, by 2100 the range increases to between 2,300 and 4,100 buildings. This study has provided fundamental coastal process predictions that can better enable adaptation plans; and a benchmark of coastal vulnerability to inundation and erosion for the City of Mandurah against which the success of future adaptation initiatives can be measured. With refinements, the modelling methodology presented here is capable of being utilised across Australia to further quantify our coastal vulnerability.
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