Sunny day flooding is becoming a serious problem in many U.S. coastal communities and is expected to become much worse in the coming decades. Measured by NOAA tide gauges, annual frequencies of 'minor' floods are today 300 to more than 1000% greater than 50 years ago largely due to increasing mean sea level with shorter-term rate fluctuations associated with the El Niño Southern Oscillation (ENSO) and Gulf Stream transport changes. In this talk, historical trends and interannual patterns of sea level and high-water exceedances above locally relevant NOAA elevation thresholds for flood impacts will be discussed. Historical changes will be presented in terms of the regionalized projections of relative sea level under the recently updated global sea level rise scenarios for the U.S. Time horizons are introduced that provide freeboard-based estimates for when in the future 'moderate' flooding associated with NOAA coastal flood warnings for a serious risk to life and property may become the new normal.

William Sweet is an Oceanographer with NOAA's Center for Operational Oceanographic Products and Services (CO-OPS). He is focused on detecting sea level extreme trends and patterns important for future preparedness needs. His work is helping public, commercial and government agencies develop coastal planning guidance for an uncertain future. He received his Ph.D. in oceanography from North Carolina State University and his undergraduate in physics from the University of North Carolina at Chapel Hill.

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