A new NOAA report says the problem of seawater spilling into communities along the Atlantic, Pacific and Gulf coasts is likely to worsen
By Eric Niiler, The Wall Street Journal, Aug. 2, 2022
Flooding along U.S. coasts has become more frequent in recent years and is likely to worsen, government scientists said in a new report. Unusually high tides driven by rising seas sloshed water onto coastal areas more than 500 times over the past year, according to the report.
The Atlantic, Pacific and Gulf coasts will experience this so-called high-tide or sunny-day flooding an average of three to seven days between May 2022 and April 2023, according to projections in the annual report, which was released Tuesday by the National Oceanic and Atmospheric Administration. That is the same as during the preceding year but up from an average of two to six days of flooding between May 2019 and April 2020.
Along the Atlantic and Gulf coasts, high-tide coastal flooding now occurs twice as frequently as it did in 2000, according to the report.
Although not as destructive as flooding associated with storms, sunny-day flooding can pose a nuisance to motorists, pedestrians and landowners as seawater surges over sea walls and bubbles up from storm drains before retreating hours later. Coastal floods can also force affected communities to find ways to ease the inconvenience and mitigate the damage—in much the same way that some northern communities develop detailed ways to cope with heavy snowfall.
“There are communities now that are starting to realize that there’s an expense to flooding,” said William Sweet, an oceanographer with NOAA’s National Ocean Service and an author of the report. “It’s like snow days in the Northeast when you have to have enough trucks, salt and people budgeted. With flooding, you have to pay police to close the street, you have to get enough pumps, you have to pay for overtime.”
The report projected even more severe increases in the long term, with 45 to 70 days of flooding per 12-month period by 2050.
For the report, the NOAA scientists gathered tidal records from past decades and current tidal data from 97 stations across the U.S. and compared them with satellite imagery showing existing sea levels across a swath of the U.S. coastline. The scientists then modeled future high-tide flooding using that data along with estimates of sea level rise from the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, which was released in February 2022.
High-tide flooding results when seawater surges at least 1.75 feet above normal high-tide levels. It is caused not by the storms and heavy rain that typically cause inland flooding but by rising seas, the scientists said in the report. Sea levels are rising as the world’s oceans warm and their volumes expand and as polar ice sheets melt, according to a 2019 report by the United Nations Intergovernmental Panel on Climate Change.
“Sea level rise is the most important cause of high-tide flooding,” said Thomas Wahl, assistant professor of civil, environmental and construction engineering at the University of Central Florida. In addition, he said, high tides in some areas have been amplified by changes to the contours of riverbeds and seafloors resulting from the dredging of coastal waterways.
A study co-authored by Dr. Wahl and published in 2021 in the journal Science Advances identified 18 locations where such dredging worsened high-tide flooding, including New York City, Wilmington, N.C., and Cedar Key, Fla.
Sea level rise is also being driven by the loss of seawater-absorbing wetlands to coastal development and by the sinking of land overlying reservoirs from which freshwater has been pumped for drinking or other uses.
South Florida has been hit especially hard by high-tide flooding between September and November, when the year’s highest tides occur. The high tides during these months, known as king tides, are amplified by seasonal ocean currents and warm ocean temperatures along the Florida coast that bring seas to their highest levels for the year. Between May 2022 and April 2023, the NOAA report predicts, the Miami area will be hit with three to six days of high-tide flooding. That is expected to rise to 35 to 60 days during that same 12-month period in 2050, the report said.
A 2021 report by the Urban Land Institute estimated that such flooding could cause South Florida more than $4.2 billion in property damage by 2040. That number will top $53 billion by 2070, the report said.
Fort Lauderdale plans to spend $200 million over the next five years to install seawater pumps in low-lying areas, said Nancy Gassman, the city’s assistant director of public works. But she said the initiative would bring only temporary relief.
“You can’t pump the ocean. In certain locations you will just pump it out and the tide will just bring it back,” Dr. Gassman said, adding that “we have to be smart about where we target areas for development and recognize certain neighborhoods will be reclaimed by the ocean.”
https://www.wsj.com/articles/coastal-flooding-in-the-u-s-on-the-rise-as-sea-levels-climb-scientists-say-11659460994?mod=Searchresults_pos10&page=1