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Australia's coastlines are of significant environmental, cultural, and economic value but are under constant threat from both natural and human induced influences. While early warning systems for coastal hazards have been recommended by the UN for disaster risk reduction, to date most of this development has focussed on the short prediction horizons (i.e., up to one week) of extreme coastal storm events to support emergency response. However, a better understanding of the regional drivers of coastal hazards such as erosion and coastal flooding at the seasonal timescale can enhance preparedness of coastal communities. This study presents the first analysis of shoreline position variability at the seasonal scale across Australia, utilising an unprecedented multi-decadal dataset of satellite derived shorelines. Initial results indicate that at the seasonal scale, significant shoreline erosion occurs more commonly in the southern states during the Austral winter months and in the northern states in the Austral summer months. Across Australia, enhanced shoreline erosion coincides with the La Niña phase of ENSO. La Niña was associated with 10-40m narrower beach widths than in El Niño or neutral states across Australia, although this was influenced at the beach scale by beach rotation. These results show that insight on the effects of climate drivers on coastlines is integral to our understanding of seasonal scale coastal processes. [ABSTRACT FROM AUTHOR]

East Coast Low (ECL) storms along the NSW coastline can result in substantial beach erosion and threats to adjacent coastal property and infrastructure. These erosion events are primarily driven by extreme wave heights generated by low-pressure systems, sometimes exceeding 8 m offshore but varying considerably as ECL storm waves approach the embayed coastline. Understanding possible changes in the extreme coastal wave climate caused by ECLs is critical for both coastal engineering design and planning of any future mitigation activities. This is complicated by climate change, which is projected to alter both the direction of future ECL storm tracks and their associated wind fields that generate large waves. This study explores the potential future impacts of ECLs on coastal wave climate of NSW in a warming climate. A unique high-resolution atmospheric model of the SE Australia region (HiRes-MESECA) is used to simulate the 2007 Pasha Bulker and the June 2016 storms. Simulations are undertaken using both present conditions and a range of future climate scenarios. A triple-nested WaveWatch3 (WW3) wave model is then applied that simulates the propagation of the deepwater regional wave climate to the nearshore (i.e., to the 10m depth contour along the entire NSW coastline). Somewhat surprisingly, initial investigations from these simulations indicate that coastal waves that are anticipated to result from future ECLs may become less extreme at the coast, even under high range (RCP8.5) climate scenarios. These results have important implications for coastal engineering design, where the design life typically needs to consider climate change effects. [ABSTRACT FROM AUTHOR]