National Climate Risk Assessment: Probabilistic Coastal Inundation Layers

The Australian Climate Service (ACS), has generated coastal inundation layers covering all coastal capital cities and many regional cities around Australia for different sea level rise increments. This method provides a nationally consistent dataset on the hazard of future coastal extreme sea levels and flooding.\n\nCoastal inundation layers are available for 164 Local Government Areas (LGAs) within Australia for different annual probabilities of coastal inundation (greater than 95%, between 95% and 50%, between 50% and 5% and less than 5%) for a given average recurrence interval (ARI) extreme coastal water level. The layers are at 5 metre resolution and are available in vector spatial file formats (.geoJSON .shp).\n\nThe National Climate Risk Assessment data is provided for the 1% Annual Exceedance Probability (AEP) with SLR increments of 0.06, 0.1, 0.2, 0.38, 0.6 and 1.0 m. \nLineage: The coast of Australia was broken up into 4029 tiles, each tile is ~5km wide and extends ~5km inland. Tiles overlapping each LGA in the 2023 LGA shapefile (Australian Bureau of Statistics) were analysed separately. The three main sources of data to compute inundation extents were gridded land elevations, tide gauge water levels and ocean modelled waves. The availability of these datasets across the nation determined the coverage of the inundation modelling, which includes all major cities and many regional cities, within ~160 LGAs. Further coverage could be provided in the future with the inclusion of hydrodynamic water level simulations where there is no tide gauge, future government funded LiDAR DEM surveys, and increasingly accurate satellite remote sensing mission data.\n\nWhile the methods have certain assumptions and limitations, they offer valuable insights into plausible future climate conditions across Australia. These hazard layers can be combined with detailed local information about exposure and vulnerability to assess climate risks on a regional scale.\n\nOne limitation of using inundation layers for evaluating impacts on individual properties is the dependence on the accuracy and resolution of the underlying data and models. These potential inaccuracies can lead to overestimations or underestimations of impact. However, when considering the number of affected properties at a larger, aggregated scale, the estimates become more reliable and robust for regional planning and risk assessment. For precise impact assessments at the individual property level, additional data and localised analysis should be employed.\n