NOAA has released the 2021 State of High Tide Flooding and Annual Outlook, which documents changes in high-tide flooding patterns from May 2020 to April 2021 at 97 NOAA tide gauges along the U.S. coast and provides a flooding outlook for these locations through April 2022, as well as projections for the next several decades.
High-tide flooding, often referred to as “nuisance” or “sunny day” flooding, is increasingly common due to years of sea level rise. It occurs when tides reach anywhere from 1.75 to 2 feet above the daily average high tide and start spilling onto streets or bubbling up from storm drains. As sea level rise continues, damaging floods that decades ago happened only during a storm now happen more regularly, such as during a full-moon tide or with a change in prevailing winds or currents.
According to the report, U.S. coastal communities saw twice as many high tide flooding days than they did 20 years ago, and the trend of near-record high tides is expected to continue through April 2022, as well as in decades to come.
Along the Southeast Atlantic and Gulf coastlines, 14 locations set or tied records where rapidly increasing trends in high-tide flooding have emerged.