In just 18 years — less than the life of some mortgages — rising seas will cause disruptive flooding in about 170 coastal communities across the United States, including Edisto and Kiawah islands, a new analysis says.
Prepared by the Union of Concerned Scientists, a nonprofit science advocacy group, the report is said to be the first nationwide attempt to identify tipping points — times and places where flooding is so frequent that residents abandon their land or pump big bucks into projects to hold back the ocean.
No stranger to high water, Charleston already sees regular “nuisance floods” at seasonal high tides, though the problem has grown worse in recent years. Charleston averaged four days of tidal flooding 50 years ago. Last year, the city had a record 50 flooding days, many when the sun shined.
Even so, the city has yet to reach a “chronic inundation” threshold — when 10 percent or more of its usable, non-wetland area floods at least 26 times per year, according to the Union of Concerned Scientists report.
That will change within a couple of generations.
By 2060, under moderate sea-rise scenarios, the group predicts 16 percent of peninsular Charleston will see debilitating floods at an average rate of every other week.
By then, chronic floods also will affect roughly:
- 17 percent of James Island
- 41 percent of Kiawah Island
- 27 percent of Edisto Island
- 10 percent of Mount Pleasant and McClellanville and the Waccamaw Neck
The situation only grows worse after that, the report said.
By 2100, rising waters could swallow or routinely flood nearly 87 percent of Kiawah Island, 57 percent of Edisto Island, 40 percent of James Island, and about one-third of the Charleston peninsula and Mount Pleasant. This assumes that sea levels increase by 4 feet by the end of the century, which is in the mid-range of current scientific estimates.
With its low elevation and expansive marshes, the South Carolina Lowcountry is well-named. Even relatively small rises in the sea level can move water far inland.
In Lowcountry on the Edge, The Post and Courier’s climate change series, the newspaper reported how 1 foot of rising water could flood 204,000 acres of marsh and 64,000 acres of land in Charleston County alone. This would affect nearly 1,000 homes, offices and other buildings, according to a College of Charleston geology department report.
Locally, the city of Charleston is spending or plans to spend about $300 million on drainage work and a future seawall in peninsular Charleston.
"We're already concerned" about sea rise, said Charleston Mayor John Tecklenburg, adding that he hasn't seen the report.
In addition to the drainage and seawall project, the city has been working on more specific sea-rise adaptation plans. Recommendations may be discussed at a public workshop later this month. He said the city likely will need to prioritize which land in the city should be protected from rising waters and which should be left to the waves.
“You don’t want to create another flood problem by building in a flood plain.”
South of Charleston, Kiawah Island Mayor Craig Weaver said the October 2015 storm and Hurricane Matthew in 2016 helped spur what he described as a “low-key” look at the island’s vulnerabilities to sea rise. The town established a citizens committee earlier this year that should make recommendations later in 2017.
He said he didn’t consider sea rise an urgent issue, adding that “we are not wading into the broader political debate about global warming or its causes.”
Gone with the sea
The Lowcountry is by no means alone in its sea-level struggles.
About 270 communities face chronic flooding and possible retreat by 2060, according to the Union of Concerned Scientists report, which is called "When Rising Seas Hit Home." The analysis was published Wednesday in the scientific journal Elementa.
Coastal Maryland and Virginia will be especially hard hit. In addition to rising sea levels, land there is subsiding — sinking downward because of movements in the earth's tectonic plates. Louisiana's situation is even worse. Land there is subsiding in part because of efforts to reroute the Mississippi River. A football field of land in Louisiana now washes away every hour, scientists say.
Wednesday's report comes at a time of high political tension about how to address a climate that’s changing at a rapidly increasing pace.
The Trump administration recently pulled the United States out of the Paris climate accord, the international agreement to reduce greenhouse gases. Meantime, new reports have trickled out during the past month about potentially devastating melting trends in Greenland and Antarctica.
The report’s authors said that hundreds of coastal communities could be spared if world leaders follow the Paris accord’s guidelines to reduce carbon emissions and other greenhouse gases.
Despite the Trump administration’s opposition, states and cities have vowed to uphold the Paris agreement’s goals in their jurisdictions.
“They understand that if we fail to limit warming, we’re committing a great many people to a future of flooding and inundation,” said Rachel Cleetus, lead economist and climate policy manager at the Union of Concerned Scientists.