Estimates of Future Sea Levels Under Sea‐Level Rise: A Novel Hybrid Block Bootstrapping Approach and Australian Case Study

Abstract Coastal flood events are increasing in both frequency and magnitude with ongoing sea‐level rise. Here we present a new statistical approach to generate future daily maximum water level timeseries and associated annual and daily flood probabilities for Australia. Our method provides several improvements on existing projection methods, including accounting for how variability in storm surges, tides and mean sea level impact the timing of annual maxima within and between years. Our method presents projected future water levels with autocorrelation and other key statistical properties of observations preserved. Under a sea level rise scenario of approximately 0.8 m by 2100, new record sea levels will be set at least once at 86% of Australian tide gauges between 2020 and 2050. By the 2090s, even a small storm surge can exceed the 2020 current day record sea level at most locations, with exceedances especially likely at times of higher tides. The impacts of future extreme sea levels will be more extreme than current or past record sea levels. For example, in the coastal town of Ballina, New South Wales, there is a 50% chance that 94% of all land parcels will be flooded at least once this century.