A MARTÍNEZ, HOST:
The nor'easter this past weekend dumped more than 6 inches of rain on parts of the Northeast. Extreme rainfall like that can overwhelm old sewer systems and cause flooding. Some cities are developing better ways to handle flash floods. Reporter Steve Kastenbaum in New York reports on some low-cost fixes that are hiding in plain sight.
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STEVE KASTENBAUM, BYLINE: Backhoes are digging up a paved yard at the Jefferson Houses. It's a public housing complex in East Harlem. Rit Aggarwala says the reason is below the surface.
RIT AGGARWALA: A historic stream. There used to be Harlem Creek that flowed down 116th Street.
KASTENBAUM: Aggarwala is a former commissioner of the city's Department of Environmental Protection. He said water has a memory. It wants to follow well-worn paths, but the city's old sewer system can't handle the extreme rainfalls that are happening more often here.
AGGARWALA: All of that water trying to get into the sewer system - it's like taking a 2-liter bottle of water and trying to dump it into an 8-ounce cup.
KASTENBAUM: With nowhere to go, the rain then floods streets and buildings. So crews here are building tanks under the yard and topping it with pavers that let rain seep through the soil into the holding area.
AGGARWALA: So that instead of just a concrete slab that's a playground or other open space for the residents that creates flooding in the areas around it, this actually becomes a solution that keeps the apartment buildings from getting flooded.
KASTENBAUM: While billions of dollars have been earmarked for sewer upgrades, hundreds of less disruptive flood mitigation projects like this were installed across New York over the last few years. Other cities, like Philadelphia and Portland, Oregon, are doing the same. The idea is to turn the ground into a sponge and absorb the water. The compounding effect of these adaptations enables cities to bounce back more quickly from flash floods.
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UNIDENTIFIED PERSON: Taxi.
KASTENBAUM: Walk along 116th street by Malcolm X Boulevard in Manhattan and you see the city's most basic flood defense on every corner.
AGGARWALA: So this is a catch basin. We have roughly 150,000 of them across New York City.
KASTENBAUM: When it rains, litter in the street blocks some catch basins, or storm drains. So Aggarwala said the city launched a pilot program recruiting volunteers to clear away garbage and restore the flow.
AGGARWALA: Some good citizen will just rake aside whatever's covering it over and the intersection will drain in a matter of minutes, often.
KASTENBAUM: There's another flood mitigation fix on this corner that's easy to miss. The 116th Street subway station was prone to flooding, so the Transit Authority's Eric Wilson said they installed a riser at each entrance. People now have to step up before they climb down into the station.
ERIC WILSON: And that little elevation creates just enough of a run-off mitigation to keep rainwater from going down into the stairs below.
KASTENBAUM: The city installed steps like this at hundreds of subway entrances, with more to come. They also raised sidewalk air vents that were prone to flooding. And there's been a payoff. Extreme rainfall used to shut down entire subway lines for hours. But during the recent nor'easter, the disruptions were localized and short-lasting. During several flash floods over the summer, the impact was also limited.
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KASTENBAUM: Engineers also designed protection right into the sidewalks. Andrea Parker of the Gowanus Canal Conservancy showed off a curbside rain garden in Brooklyn. It's filled with greenery and a tree, but it's not typical landscaping. Water flows into the rain garden from the street instead of into the sewer system.
ANDREA PARKER: And then it soaks in. There's about 3 feet of soil and then 2 feet of gravel that have tons of pore space for that water to percolate into.
KASTENBAUM: Adding sewer capacity in a neighborhood like this cost tens and sometimes hundreds of millions of dollars. A curbside rain garden costs about $40,000 to build.
PARKER: Each of those pieces of decentralized green infrastructure is part of the larger solution.
KASTENBAUM: Back in Harlem, Aggarwala said the payoff shows up after a storm passes.
AGGARWALA: There's tremendous flooding at a given intersection, and then half an hour later it's totally gone.
KASTENBAUM: Extreme rain is the new normal for some cities. They can't stop it, but they're bouncing back faster with fixes many people never notice.
For NPR News, I'm Steve Kastenbaum in New York.
(SOUNDBITE OF KAKI KING'S "SKIMMING THE FRACTURED SURFACE TO A PLACE OF ENDLESS LIGHT") Transcript provided by NPR, Copyright NPR.
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