(CN) — High tide flooding, otherwise known as “nuisance” or “sunny day” flooding, doubled along the U.S. coast when compared with similar instances of flooding twenty years ago and is expected to continue to increase, according to a new government report.
Between May 2020 and April 2021, coastal communities along the United States saw twice the number of floods from high tide as in 2020, especially along coastal areas along the Atlantic and Gulf Coast, according to a report published Wednesday by the National Oceanic and Atmospheric Administration, 2021 State of High Tide Flooding and Annual Outlook. The trend is expected to continue into 2022.
The report documents change in high tide and flooding patterns over the last year at 97 NOAA tide gauges along the U.S. coast, and provides a flooding outlook for these locations through April 2022 along with projections for the next several decades.
“High tide flooding is becoming common and damaging in many parts of the U.S.,” William Sweet, an oceanographer for NOAA’s National Ocean Service and lead author on the report said Wednesday in an emailed press release. “Many coastal communities are saddled with this problem, so NOAA is working to provide them with the kinds of information needed to anticipate, prepare for, and respond to increasingly frequent high tide flooding.”
The study showed that during the period from 2020-21, 14 locations along the Southeast Atlantic and Gulf coastlines, tied or broke their records for the number of flood days — a 400-1100% increase over what was experienced in 2000, the report said. The number of high tide flood events is currently accelerating at 80% of NOAA water level stations along those coasts.
High tide flooding, or what is defined as NOAA as “flooding which causes public inconvenience,” causes flooded shorelines, streets and basements, obstructions to traffic and cancelation of events.
The term “high tide flooding” refers to incidences when tides reach anywhere from 1.75 to 2 feet above the daily average high tide and begin to spill over into streets or bubble up from storm drains.
Incidences of such flooding, which decades ago only happened during storms, are becoming increasingly prevalent during full-moon tides and changes in prevailing winds and currents as sea levels continue to rise.
“NOAA’s tide gauges show that 80% of locations where we collect data along the Southeast Atlantic and Gulf coasts are seeing an acceleration in the number of flood days,” Nicole LeBoeuf, director of NOAA’s National Ocean Service, said in an emailed press release.
“High-tide flooding disrupts people’s lives when they can’t get to and from work or have to repeatedly deal with a flooded basement,” LeBoeuf continued. “NOAA is committed to working with coastal communities to provide the information and tools they need to tackle the problem of high-tide flooding, both now and in the coming years as sea levels continue to rise.”
Regions of particular concern, according to the data, are in Texas and Florida, with records also broken along the South Carolina and Georgia coasts.
During the relevant period, Galveston and Corpus Christi, Texas and Bay Waveland, Mississippi each set a record of more than 20 days of high tide flooding. Twenty years ago, according to the report, these areas would have only typically seen 2-3 days each.
Dauphin Island, Alabama; Grand Isle, Louisiana; Pensacola, Panama City Beach and Trident Pier, Florida; Charleston, South Carolina; Port Isabel and Rockport, Texas all saw between 10 and 20 days of flooding. In 2000, they would have seen between 0-2 days of flooding from high tide.
Authors of the study project that from May 2021 to April 2022, the national high tide flood frequency is expected to continue to rise, with U.S. coastal communities seeing an average 3 to 7 days of flooding in the year ahead, compared with last year’s projection of 2 to 6 days. Locations along the Atlantic and Gulf coasts may experience even more days of flooding.
By 2030, projections show 7 to 15 days of flooding per year across national coastal communities, and by 2050, the prediction rises to 25 to 75 days annually.
Long term forecasts are based on the range of relative sea level rise, using two scenarios, Intermediate Low and Intermediate, of the Fourth National Climate Assessment considered more likely to occur by 2030 and 2050.
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