By Abbie Bennett
RALEIGH – Living in cities threatened by sea-level rise could be like living near an active volcano, according to NOAA oceanographer William Sweet.
Some parts of the Earth are seeing sea levels rise far beyond average, and it’s just a waiting game before some areas are inundated with sea water, studies show.
The East Coast of the U.S. is experiencing “sunny day flooding” that scientists didn’t expect for decades yet.
Residents of coastal communities most often feel the effects of sea level rise during tidal flooding.
Tidal flooding, also known as “sunny day flooding” is the temporary inundation of low-lying areas, such as roads, during high-tide events — especially during “king tides,” the highest tides of the year.
King tides aren’t caused by sea level rise in and of themselves, but because they are the annual peak tides, they demonstrate how sea level has already risen over the past 100 years.
Sea levels aren’t rising equally “like water in a bathtub,” according to a report from Yale Environment 360. “The oceans are more akin to a rubber kiddie pool where the water sloshes around unevenly, often considerably higher on one side than another.”
More flooding, higher costs
Climate scientists view sea level rise as one of the most obvious signals of a warming planet. Sea water expands as it warms, and melting land-based ice sheets adds to rising water levels.
There are neighborhoods that now flood on sunny days, but didn’t years ago even during especially high tides, according to the National Oceanic and Atmospheric Administration.
And as sea levels continue to rise, the frequency, depth and extent of coastal flooding will continue to worsen, according to NOAA.
In 2016, Charleston saw 50 days of tidal flooding.
Fifty years ago? Just four days.
Flooding projections are set at about 25 percent above average for 2017-18 for areas including Wilmington, according to a recent NOAA report.
Wilmington had 84 days of high-tide flooding in 2016, according to NOAA.
“It is important for planning purposes that U.S. coastal cities become better informed about the extent that high-tide flooding is increasing and will likely increase in the coming decades,” according to the February 2018 NOAA report.
Sea levels rise and waters inundate storm drains and wash over flood barricades — flooding buildings and streets.
While flooding impacts might be limited or not obvious in those area right now, stormwater systems are reported to be degraded, “increasing the risk of compound flooding during heavy rains,” according to NOAA.
And coastal cities should be particularly concerned that the cost of dealing with an increase of many smaller floods will be greater than major, but much rarer, flood events, NOAA said.
NC towns underwater?
A 2017 report “When Rising Seas Hit Home: Hard Choices Ahead for Hundreds of U.S. Coastal Communities” analyzed three projected scenarios of when towns and cities along U.S. coasts can expect to see the ocean rise enough to disrupt daily life.
That report found that as many as 20 North Carolina communities could be submerged by sea water in the next 15 years.
The report was created by the Union of Concerned Scientists, a U.S. nonprofit science advocacy group founded in 1969 by faculty and students of the Massachusetts Institute of Technology.