NOAA High Tide Flooding Update: Coastal Flooding on the Increase

Above: Potomac River Flooding on King Street in Alexandria, Virginia in 2015 (Credit: NOAA) NOAA has released data from the previous year on high tide flooding in coastal locations in the United States. The data shows an increased number of days with High Tide Flooding for many coastal cities in the Untied States. NOAA attributes the increase in flooding to sea level rise.

“High tide flooding is becoming more common and damaging in many parts of the U.S.,” said Rick Spinrad, Ph.D., NOAA Administrator. "As part of NOAA’s work to build a Climate-Ready Nation, we will continue to provide coastal communities with the information needed to anticipate, prepare for and respond to increasingly frequent high tide flooding.”

High tide flooding is defined as "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". Because of rising sea levels, NOAA is saying high tide flooding is occurring "during full moons or with a change in prevailing winds or currents" rather than just during major storm systems.

“The East and Gulf coasts already experience twice as many days of high tide flooding compared to the year 2000, flooding shorelines, streets and basements and damaging critical infrastructure,” said Nicole LeBoeuf, director of NOAA’s National Ocean Service. “As sea levels continue to rise, NOAA is committed to working with coastal communities to provide the tide gauge information and tools they need to tackle the problem, both now and in coming years.”

High tide flooding is also subject to global patterns; in the Pacific we are experiencing a La Nina pattern, or cooler than ocean waters. The ocean waters temperature impact the atmosphere-ocean interface, and subsequent storm tracks. In a La Nina pattern, NOAA anticipates a lower threat high tide flooding potential for the U.S. West Coast and Hawaii. With ongoing sea level rise and the expected rise of a foot within the next 25 years, coastal High Tide flooding days are expected to increase as well. By 2050 the U.S. will see an average of 45-70 days per year as compared to the 3-7 days per year predicted for 2023. That would be a 10x increase in national flooding days. https://twitter.com/noaaocean/status/1554530487166652416 Compared to 2000, the U.S. and Gulf Coast States have seen a 150% increase in the number of High Tide Days. For example, the city of Galveston, TX saw only 3 High Tide flood days in 2003. In 2021 they saw 14. NOAA predicts that by 2050 they could see 170-210 High Tide flood days per year, varying in intensity. To look at all locations at the United States, click here.