Probabilistic projections of high-tide flooding frequency in the United States during the 21st century

The frequency of high-tide flooding episodes continues to increase in coastal locations around the United States. To quantify the impact of sea level rise on the frequency of such events, we developed a hierarchical statistical model to generate probabilistic projections of threshold exceedance frequency for the 21st century. The projections include probabilistic tide predictions that account for trends and inflection points in the amplitude of individual tidal constituents. Annual analysis of the projections demonstrates how planning for the `typical' future year can substantially underestimate flooding impacts during inevitable severe years, as well as pronounced inflections in the frequency of exceedance days in some locations due to the interaction between sea level rise and long-period (18.6-year) modulation of tidal amplitude. Seasonal analysis of the projections shows that the rate of change in high-tide flooding frequency is dependent on time of year, which when compared with climatological precipitation patterns has implications for changes in the frequency of compound flooding events. Finally, results of these calculations from locations around the United States have been aggregated into a dynamic web-based tool that allows users to view probabilistic projections and analyses of future exceedance days for a chosen location, including the ability to customize results for locally relevant threshold elevations.