Tidal flooding may worsen to the point of rendering some sections of cities in coastal areas unusable in the not-so-distant future, the Union of Concerned Scientists said in a recent report.
Floods during high tides weren’t a problem and rarely happened in the past but have become common now in some places, the report notes.
“Today, when the tide is extra high, people find themselves splashing through downtown Miami, Norfolk and Annapolis on sunny days and dealing with flooded roads in Atlantic City, Savannah and the coast of New Hampshire,” Melanie Fitzpatrick, UCS climate scientist and co-author of report, said in a statement. “In parts of New York City and elsewhere, homeowners are dealing with flooded basements, salt-poisoned yards and falling property values, not only because of catastrophic storms, but because tides, aided by sea level rise, now cause flooding where they live.”
The report explains that tidal flooding can happen twice each month, during new and full moons, when the combined gravitational pull of the sun and moon creates tides that rise slightly higher than normal. "Strong winds, rainfall, and storms that coincide with high tides can result in even more extensive and damaging floods," it notes.
The report said in 15 years, the scenarios would be these: most communities analyzed would experience a minimum of 24 floods annually in exposed areas, which is the equal of flooding twice a month; and 15 of these communities would experience a minimum of 48 floods annually, which is the equal of flooding four times a month.
Meanwhile, in 30 years, most towns analyzed will have a minimum of 48 tidal floods annually, which is the equal of four floods in a month. Same time frame would bring over 100 floods yearly to half of the towns, the equal of flooding eight times a month. Also, a minimum of 180 floods yearly, or about 15 floods monthly, would beset 17 towns, and nine towns would experience 240 times or even more tidal flooding yearly.
Co-author and UCS senior analyst Erika Spanger-Siegfried also said the report shows how many communities in the East Coast will witness intense changes in the severity and number of tidal floods yearly, unless steps are undertaken to manage the problem.
Among those steps, the report recommends flood-proofing homes and infrastructure; curtailing development in areas subject to tidal flooding; considering the risks and benefits of adaptation measures such as sea walls and natural buffers; and developing long-term plans based on the best available science.
The researchers indicated that the increases in cases of flooding are prevalent and that Atlantic Coast communities not covered by their analysis may experience similar changes. The rising sea level from global warming is the main cause, the report notes, as globally sea levels have risen about 8 inches from 1880 to 2009. However, in New York City the rise has been more than 17 inches ince 1856; in Boston, 10 inches since 1921 and in Baltimore, 13 inches since 1902.
They also said that communities along the Mid-Atlantic and East Coast would witness the highest increase of flooding yearly, not only because of the rise in sea level but also because of changing ocean dynamics and sinking land.
For instance, Wilmington, N.C., Washington, D.C., Lewisetta, Va., and Annapolis, Md., would see over 300 cases of flooding annually.
Spanger-Siegfried said some of these future floods could greatly affect South Beach’s Art Deco Historic District. No serious countermeasures would mean frequent flooding would begin to interfere with daily life as well as alter the functions of a particular area, which could come sooner than expected.
The report has its basis on the analysis of 52 tide gauges of the National Oceanic and Atmospheric Administration (NOAA) in communities extending from Portland, Maine, to Freeport, Texas, with the use of moderate projections of sea level rise.
The full report, titled “Encroaching Tides: How Sea Level Rise and Tidal Flooding Threaten U.S. East and Gulf Coast Communities over the Next 30 Years,” can be read at the UCS website.
