High tides are flooding basements, streets and septic systems up and down U.S. coastlines more often as sea levels rise—and the future looks even more soggy, the National Oceanic and Atmospheric Administration said July 10.
The frequency of this high-tide flooding—often called “nuisance” or “sunny day” flooding—in 2019 is expected to be double the frequency of flooding observed in 2000, according to the agency’s outlook.
Climate-related sea level rise, land subsidence, and the loss of natural barriers have been the cause of such flooding in many areas, the agency has said.
“We cannot wait to act. This issue only gets more urgent and complex with each passing day,” Nicole LeBoeuf, acting director of NOAA’s National Ocean Service, said in a teleconference with reporters.
The number of flooding days recorded in 2018 broke or tied records at 12 out of 98 NOAA tidal gauges along U.S. coasts. High-tide flooding can happen even when there are no off-shore storms pushing water toward land.
Record in Baltimore
One of the record-setting gauges was located in Baltimore. Installed in 1902, it recorded just 12 high-tide flood days in its first 35 years of operation, said Gregory Dusek, chief scientist at NOAA’s Center for Operational Oceanographic Products and Services.
Baltimore’s gauge set a record for 2018, with 12 high-tide flood days in just that year.
Higher tides mean failing septic systems in the Miami suburbs and fewer parking spaces at stores across Annapolis, Md., said William Sweet, a NOAA oceanographer.
“We’re losing space between our infrastructure and the ocean,” Sweet said.
Nationally, an average of five days of high-tide flooding recorded in 2018 is expected to increase to seven to 15 days by 2030 and 25 to 75 days by 2050, according the report.
Some coastal communities will see significantly more frequent flooding. By the time a 30-year mortgage purchased today in the New York City region is paid off, that area could see an average of 55 to 135 days of high tide flooding each year, Sweet said.
The data do not include rainfall flooding, which can combine with high tides and make things worse.
The rate of flooding is accelerating fastest along the heavily populated Northeast Atlantic coastline and along the eastern Gulf of Mexico, where water pushed ashore by hurricanes and other storms combines with rising sea levels.
Weather conditions known as El Nino—the natural warming in the Pacific Ocean that changes weather worldwide—are expected to persist this year and contribute to the increased flooding, Sweet said.