NOAA documents increasing high-tide flooding

Design firms have to be aware of the changing climate and variable weather patterns when providing services for new capital assets. Such awareness is especially vital when designing facilities in coastal areas. The National Oceanographic and Atmospheric Agency (NOAA) annually publishes information on “high-tide flooding.” That refers to tides that reach anywhere from 1.75 to 2 feet above the daily average high tide and, at a minimum, create nuisance problems by flooding streets or causing storm drains to discharge their contents.

In July, NOAA issued its 2021 State of High Tide Flooding and Annual Outlook. The report, which tracks 97 NOAA tide gauges along the coasts of the US, is the latest documentation of changes in high-tide flooding patterns from the previous year. In addition to documenting flooding, it provides projections for the monitored locations for the coming year as well as the next several decades.

According to the report, coastal communities continued to see record-setting high-tide flooding, forcing their residents and visitors to deal with flooded shorelines, streets, and basements. Moreover, that trend is expected to continue into 2022. The report shows that between May 2020 and April 2021, coastal communities saw twice as many high-tide flooding days than they did 20 years ago.

During the monitored period, 14 locations tied or broke their records for the number of high-tide flooding days along the Southeast Atlantic and Gulf coastlines, a range of 400% – 1,100% increase over 2000. At NOAA water level stations along the East and Gulf Coasts, the number of high-tide flood events is now accelerating by 80%. By 2030, NOAA predicts that high-tide flooding is likely to be in the range of 7-15 days, and by 2050, between 25-75 days.

NOAA bases these long-term outlooks on the range of relative sea level rise “more likely” to occur by 2030 and 2050 using projections of the Fourth National Climate Assessment, which was published in 2018. That assessment, required by the Global Change Research Act of 1990, requires a comprehensive report by the US Global Change Research Program every four years. The most recent analysis included a volume on the climate science used for the report and a volume that focused on the human welfare, societal, and environmental elements of climate change and variability. The report examines 10 regions and 18 national topics, with particular attention paid to observed and projected risks, impacts, consideration of risk reduction, and implications under different mitigation pathways. The report also provides examples of actions underway in communities to reduce the risks associated with climate change, increase resilience, and improve livelihoods.

NOAA’s information is one source of design considerations and should be recognized by design professionals working on projects in coastal areas. The warning that coastal high-tide floods, causing significant risks to life and property, will become much more commonplace as we approach mid-century and will influence the ability of design firms to protect public health, safety, and welfare.

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