ROBERT SIEGEL, HOST:
From NPR News, this IS ALL THINGS CONSIDERED. I'm Robert Siegel.
Congress may be deadlocked over climate change, but many U.S. cities are finding it's something they can't ignore. That's especially true after the devastation of Superstorm Sandy. NPR's Jennifer Ludden looks at preparations being made right here in the nation's capital.
JENNIFER LUDDEN, BYLINE: Hollywood loves a D.C. disaster plot. This past year, Washington's been captured by a terrorist mastermind in "Olympus Has Fallen."
(SOUNDBITE OF MOVIE, "OLYMPUS HAS FALLEN")
GERARD BUTLER: (as Mike Banning) Mr. President, there's been an intrusion. Let's go. Move.
LUDDEN: And the president's been taken hostage in "White House Down."
(SOUNDBITE OF MOVIE, "WHITE HOUSE DOWN")
CHANNING TATUM: (As Cale) We gotta, we gotta, we gotta go.
LUDDEN: But filmmakers have not taken on the far more likely threat that keeps some federal workers awake at night, maybe because the sound effects aren't as good.
(SOUNDBITE OF WATER)
LUDDEN: Flooding. Washington, D.C., is not exactly a beach town but this title basin, fed by the Potomac River, laps at the steps of the Jefferson Memorial.
TONY VIDAL: The water would go across the World War II Memorial, come up 17th Street.
LUDDEN: Where Tony Vidal is standing not much above sea level. He's with the U.S. Army Corps of Engineers.
VIDAL: And there's actually three spots where the water would come up where we don't have, currently, a closure structure right now.
LUDDEN: Enough water and it would flood what's called the Federal Triangle.
Now, we are pretty close to the White House here.
VIDAL: Yes, we are. Past that intersection, there's a low area. But then after that, the ground rises, so they're pretty protected.
LUDDEN: Likewise Congress - it is called Capitol Hill. But in between those two places, new flood maps in 2010 declared really key government buildings to be in a flood zone. Among them, the departments of Justice, Commerce, the IRS. Now, the Army Corps is building a new $10 million barrier in one of the trouble spots.
It's here at the corner of 17th Street and Constitution Avenue. There is the Washington Monument. On either side is 17th Street. I'm looking at two curved, concrete walls. They come almost up to the sidewalk. Each one has a big groove on the edge. In a flood emergency, this street would be shut down. They'd haul in big panels and build a 10-foot barrier across the street connecting to each wall. That would hold back millions of gallons of water.
VIDAL: We believe it could protect against the 500-year event with a few feet of free board. But no matter what you design it to, there's always going to be an event that can overtop it.
LUDDEN: In fact, even if the wall does keep in check hurricanes, storm surges and sea-level rise, there's another threat - increasingly heavy rains.
AMY TARCE: The Federal Triangle is actually the lowest point in this large drainage basin that's 24 times its size.
LUDDEN: Amy Tarce is a federal urban planner with the National Capital Planning Commission.
TARCE: So if you can just imagine all that water coming down, it's like the bathtub of the whole area.
LUDDEN: In a blustery wind below the Washington Monument, I ask Tarce what's the absolute lowest point in this bathtub? She gestures right across the street, where the National Museum of African-American History and Culture is under construction, complete with underground galleries.
The National Mall is where they mean when they say Washington was built on a swamp or, more precisely, malarial marshland. Constitution Avenue was a boggy creek. So you can imagine water rushing over manicured lawns, pouring into marble lobbies, threatening the national treasures within, just like one of those Hollywood movies, except it already happened in 2006, says Tarce, after a week of continuous rain.
TARCE: Basically, all of Constitution Avenue was under water, metro rail tunnels flooded, as well as the basements of the Smithsonian museums. In fact, some of these federal buildings were closed down for months.
TIM EDWARDS: Water was coming through about the door handle height there.
LUDDEN: Tim Edwards is facilities manager at the National Archives. He shows me a beautiful red velvet basement theater with a raised wooden stage.
EDWARDS: The water was up to the seat backs of that first row. All that woodwork had to be pulled off and underneath had to be dried out.
LUDDEN: Luckily, the U.S. Constitution and Declaration of Independence were safe in their vault. Down the street, the cafeteria flooded at the National Museum of American History. But Dorothy's ruby slippers and Julia Child's kitchen, safe. Still, who wants to risk it?
The National Archives has installed a self-rising flood wall tucked underground on the loading dock driveway. Edwards peers into a 16-foot-deep well next to it.
EDWARDS: There's a 6-inch line that's coming from that catch pipe at street level.
Rainwater runs from the street into the well. When that's full, it spills into a cavity underneath the fiberglass floodwall.
And once it starts stopping in there, that wall will move pretty quick.
LUDDEN: It will float up, sealing off the driveway. The new African-American Museum will also have an automatic floodgate, plus manually installed panels, sandbags and special glazing, all designed to protect against a 500-year flood.
BRENDAN SHANE: There's a very interesting discussion always about, you know, how bad it's going to get in 50 years.
LUDDEN: Brendan Shane is with District of Columbia's Department of the Environment.
SHANE: Well, the problem is, it could get really bad already.
LUDDEN: And really costly. A University of Maryland study finds that if D.C. got hit with a Superstorm Sandy, property damage alone would top $24 billion. Cities all along the East Coast are grappling with that risk.
Outside his office, Shane shows me how Washington is trying to prevent what flooding it can. Public sidewalks now have big rain gardens to absorb thousands of gallons of water. We go into a high-rise condo complex and up onto a spacious second-story patio.
SHANE: It feels sort of like we're in a park but it's really a roof.
LUDDEN: It's lovely.
SHANE: Yeah. It's beautiful.
LUDDEN: There are sprawling gardens, a woman walking her dog. D.C. has installed more than 2 million square feet of green roofs like this and it's starting to require them for new construction.
SHANE: And so the idea is that if it rains an inch in a day or two days, that roof will be able to manage that and it won't flow off into the pipes and into the sewer.
LUDDEN: Down on the National Mall, officials are considering a huge underground pumping station, a new sewer tunnel 30 feet in diameter, a giant cistern the size of 20 football fields. None would be cheap. Estimates range from 300 to $500 million. But federal urban planner Amy Tarce says there's an even bigger challenge: keeping a sense of urgency.
AMY TARCE: People have short-term memories. They see the cars are running. They can go to work. The office buildings are back. So it's hard to convince people that there's actually a threat.
LUDDEN: At least until the next time disaster hits the heart of the nation's capital. Jennifer Ludden, NPR News, Washington.