Encore: D.C.'s unique history provides a bit of extra security from sea level rise
AILSA CHANG, HOST:
As climate change raises sea levels and energizes hurricanes, a big concern is flooding from storm surge. NPR has analyzed National Hurricane Center modeling from Miami, New York City and Washington, D.C. And as WAMU's Jacob Fenston reports, D.C. has a bit more protection than other locations due in part to the city's history as the nation's capital.
JACOB FENSTON, BYLINE: The last time there was major storm surge flooding in Washington was during Hurricane Isabel back in 2003.
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UNIDENTIFIED REPORTER: Three hundred fifty thousand federal workers have been told to stay home.
FENSTON: As the storm blew inland from the Atlantic, it pushed a bulge of water up the Potomac River, cresting in Washington at more than 11 feet above normal. Sea level on the Potomac has already risen about a foot due to climate change. It's expected to go up another 3 feet or more this century, meaning future storm surges could be that much higher. But much of the area that floods is parkland. It provides a kind of buffer to the rest of the city.
DAVID RAMOS: It is a strange thing. It's where D.C.'s gotten lucky in its exposure to flooding risk.
FENSTON: David Ramos teaches at American University and has studied and mapped Washington's historic waterways.
RAMOS: We've got parks down here, and the parks can flood without people being at risk.
FENSTON: I met Ramos at one of the places in the city most at risk to flooding - a low-lying peninsula at the confluence of the Potomac and Anacostia Rivers. In fact, this wasn't land at all back in the day.
RAMOS: Let's go back to maybe 1840, and we're standing, really, right in the river.
FENSTON: In the mid-1800s, D.C. had a big problem. After decades of cutting down forests and expanding the city, the rivers were silting up from all the runoff, and there was no sewage treatment at the time, so...
RAMOS: It's just a giant, smelly mudflat.
FENSTON: The solution was to dredge the rivers. The federal government used the dredged-up muck to extend the shoreline, building new land. Other cities, like New York, built office towers and apartments on reclaimed land along the water, places that are now vulnerable to storm surge. In Washington, though, the federal government happened to be in a park-building craze at the time, part of the City Beautiful movement.
RAMOS: The idea that cities can be more deliberately planned and that they can and should include large areas of parks.
FENSTON: Today, some 90% of D.C.'s waterfront is owned by the government. It's home to some of the most famous monuments in the city, areas that can flood without displacing anyone. An NPR analysis of data from the National Hurricane Center projects that a Hurricane Isabel, if it happened in 2080, could impact more than 2,000 people in Washington, up from 600 today, because of sea level rise. But that's compared to more than 400,000 people who'd be impacted in New York or Miami. There is pressure to develop along the waterfront, though. Nicholas Bonard is with D.C.'s Department of Energy and Environment.
NICHOLAS BONARD: If you only cared about floodplain management and nothing else, you would probably say, let's not build in these areas.
FENSTON: But he says you have to balance flood risk.
BONARD: Cities have lots of other priorities, too - housing, great spaces. You know, people want to be on the water.
FENSTON: And while D.C. may have lucked out when it comes to vulnerability to storm surge, another threat - interior flooding - is getting worse because of climate change. This is when a storm dumps lots of rain all at once, overwhelming drainage pipes. Stacey Underwood with the Army Corps of Engineers heads up a local flooding task force.
STACEY UNDERWOOD: D.C. did experience that interior flooding in 2018, 2019, 2020. So it really is becoming a frequent, recurring event.
FENSTON: In a worst-case scenario, interior flooding could happen at the same time as the storm surge. In fact, that's what officials were preparing for in 2003, why the entire city shut down ahead of the storm. Forecasters warned of up to 12 inches of rain. After Isabel passed through, less than an inch had fallen on the city. D.C. got lucky.
For NPR News, I'm Jacob Fenston. Transcript provided by NPR, Copyright NPR.