High-Tide Flooding On The Rise, Especially Along The East Coast, Forecasters Warn

ARI SHAPIRO, HOST:

Flooding in coastal cities is happening more and more, and rainstorms aren't the only culprit. A new report out today says that means chronic flooding in many places. NPR's Rebecca Hersher explains.

REBECCA HERSHER, BYLINE: Charleston, S.C., is one of the dozens of coastal cities where high tides increasingly mean water in the streets.

KATIE MCKAIN: Yeah, there was one two weeks ago.

HERSHER: Katie McKain is the director of sustainability for the city of Charleston. She says between rising sea levels and more extreme rain - both driven by climate change - she deals with floods and the weather forecast all the time.

MCKAIN: At this time of year, it can easily be once a week or more.

HERSHER: It's expensive, it's time-consuming and it's only getting worse. High-tide flooding events in Charleston have more than doubled since 2000. And by 2030, the city is projected to experience 10 to 20 days a year of ocean flooding without any storm to cause it. That's according to an annual report on high-tide flooding from the National Oceanic and Atmospheric Administration.

Mark Wilbert is the resilience director for Charleston.

MARK WILBERT: I do think we're going to have to adapt. I think everybody up and down the coast is going to have to adapt.

HERSHER: Positions like Wilbert's are a relatively new part of city government. He started as resilience director a couple years ago, specifically because of flooding. He says forecasts like the one released today by NOAA are extremely important tools for local officials who are trying to plan city services.

WILBERT: That's really about budgeting because as we're going to have to respond to each of these, we're going to need, you know, resources to meet what the expected demand will be.

HERSHER: For example, the number of high-tide flood days affects how much money needs to be set aside for police, for sewer maintenance, for public education about how to prepare for floods. High-tide flooding can also hurt local economies. A study last year found that one sunny-day flood in Annapolis, Md., cost businesses about $100,000. The new NOAA report finds that Annapolis and nearby Baltimore and Washington, D.C., all set new records for high-tide flooding last year. And the trend is accelerating. The same is true to the South and Florida, along the Gulf Coast in cities like Houston and Galveston and to the North.

Stephanie Kruel is an environmental planner with the Boston engineering firm VHB. She says much of the city was built on dirt that was trucked in, mostly to fill marshy areas.

STEPHANIE KRUEL: At the time they were filled, sea level rise wasn't something that anybody contemplated, and so the areas that were filled were just a couple of feet above high tide.

HERSHER: But as sea levels have risen, tides have gotten higher. Today, Boston has about 20 days of high-tide flooding a year in major downtown areas.

KRUEL: We have a major commercial district, the downtown financial district. Even City Hall itself is very low-lying.

HERSHER: And then there's planning for the future. There is still demand for new office space and homes right on the water. To protect those areas, the city plans to upgrade stormwater systems and raise roads higher. Kruel says there's also a plan to require new buildings in low-lying areas to have elevated first floors, which seems straightforward, but higher first floors actually change a normal city street a lot. For one thing, buildings still need to be accessible to strollers and people in wheelchairs.

KRUEL: So now you have to deal with, you know, ramps or elevators or something like that.

HERSHER: It's an example of how cities are grappling with the basics of how they're built, and they're being forced to figure it out now, with ocean water already in the basement. Rebecca Hersher, NPR News. Transcript provided by NPR, Copyright NPR.