- As sea levels rise, sunny-day flooding – which occurs when tides are high, rather than during an abnormal weather event – is on the rise as well.
- In 2018, the number of days with high-tide flooding in the US tied the record set in 2015. In the coming year – from May 2019 through April 2020 – experts expect that record to be broken.
- New projections show that the risk of high-tide flooding is rapidly increasing for communities on the Gulf and East coasts: By 2050, some coastal areas are likely to underwater for at least 100 days per year.
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Increasingly, sunny days don’t guarantee dry ground for those living along the coast.
As sea levels rise due to climate change, high tides are creeping further up onto coastal land, flooding communities even without any rain or stormy weather.
Oceans along US coasts have risen nearly 10 inches (25 centimeters) since 1920 (12 inches when you factor in sinking land). That has led high-tide flooding to occur twice as often now as it did nearly two decades ago, according to a recent report from the National Oceanic and Atmospheric Administration (NOAA).
NOAA monitors sea levels along US coastlines, and the agency’s data suggests that overall, coastal communities saw a median of five days with high-tide floods in 2018, tying a record set in 2015. The water blocked roadways, damaged homes and basements, and overwhelmed septic tanks and storm-water systems.
The researchers say this is just the beginning: They expect to see that record broken this year, and within 30 years, the frequency could jump to 75 flood days per year.
“The future is already here in terms of sea-level rise impacts,” William Sweet, a NOAA oceanographer and the report’s lead author, said during a press conference. “The current trajectory suggests, let’s say, a floodier future.”
By 2050, some parts of the country could spend at least 100 days under high-tide water each year, according to the report. That doesn’t even include flooding from storms and hurricanes.
“Once communities realise they are susceptible to high-tide flooding, they need to begin to address the impacts, which can become chronic rather quickly,” Sweet said in a release. “Communities find themselves not knowing what to expect next year and the decades to come, which makes planning difficult. Our high-tide projections can play a vital role in helping them plan mitigation and other remedies.”
Here’s where to expect the worst.
The NOAA report analysed data between May 2018 and April 2019 from 98 sensors along US coastlines. More than 65 of those locations showed increasing rates of high-tide flooding.
In the Northeast, sea levels are rising faster than the global average. Overall, the frequency of high-tide floods for the entire region this year is expected to be 140% of what it was in 2000.
In 2018, Annapolis and Baltimore, Maryland saw 12 days of high-tide flooding; Wilmington, North Carolina had 14 days; and Apalachicola, Florida had 10. These are all record-breaking frequencies.
In Boston, Massachusetts, meanwhile, the frequency of high-tide floods has tripled since 2000. And Washington, DC saw a record 22 flood days last year. Three decades from now, the city could see sunny-day floods on up to 120 days per year.
Norfolk, Virginia, meanwhile, experienced some of the most severe impacts over the last year. Sea levels rose 10.5 inches there between 1963 and 2012. In 2018, floodwaters blocked roads and damaged cars to such an extent that residents approved a property-tax hike to fund flood-mitigation projects like tide gates, pumps, and flood walls.
Western Gulf Coast
This coming year, the western part of the US Gulf Coast (Texas and Louisiana) could see an annual median of six days with high-tide flooding, NOAA predicts.
That’s a 130% increase from the numbers in 2000. By 2050, the area could see 165 flood days per year.
The Galveston-Houston area of Texas, specifically, could get up to 215 days of high-tide flooding per year by 2050 – that’s more flood days than dry days. Sea levels in the Galveston-Houston region rose 12.5 inches in 50 years, according to measurements from 2012.
Last year, Miami-Dade county did not have high-tide flood days, according to the report; however, rising sea levels still elevated groundwater levels and stumped septic tanks there. The report projects one to three days of high-tide flooding in the area in 2019.
In the Southeast region overall, the projected frequency of high-tide flooding for this coming year is 190% of what it was in 2000.
Charleston, South Carolina can expect up to seven days of high-tide floods this year. By 2050, that number is expected to jump to 90 days.
“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 press conference.
The government experts hope this report will alert vulnerable coastal communities to that threat and spur them to implement plans like the one recently enacted in Norfolk, Virginia.
“With projections, folks can get a better handle on what to expect as they plan and prepare for the future,” Sweet said.
You can check the projections for your specific area on NOAA’s interactive map.