One centerpiece of the Gentilly Resilience District will be creating the 25-acre Mirabeau Water Garden to filter stormwater while providing beautified space for recreation and education. New Orleans Redevelopment Authority

The city is using a big federal grant to filter and retain the stormwater it once banished.

Unlike some other flood-prone, below-sea-level cities, New Orleans keeps its water hidden.

Whereas Amsterdam and Venice channel the seas through a dense network of canals dispersed throughout the city, New Orleans long ago resorted to fortifying its borders against the lakes, river, and swamps that surround it—pumping out whatever water got through. That was one reason why Hurricane Katrina hit the levees with such ferocity: the pent-up floodwaters got funneled down the man-made canals until they crashed against man-made barriers.

After decades of fighting the tide, the city now is changing course. Using a $141 million grant from the U.S. Department of Housing and Urban Development, New Orleans will radically alter the landscape of its Gentilly neighborhood to filter and retain stormwater, rather than banishing it, The Times-Picayune has reported. This approach has worked well in places like the Netherlands and Denmark, but success in New Orleans could signal a new era in how American coastal cities handle the water around them.

Turning a swamp into a home

Gentilly sits due north of the French Quarter, bordered by the spacious City Park to the west, the Inner Harbor Navigation Canal to the east, and Lake Pontchartrain to the north. It houses the University of New Orleans as well as Dillard University. Mostly, though, the district is made up of single-family homes spread out along a spacious grid of streets—not quite suburban, but far from dense. It also used to be a swamp.

(Google Maps)

For most of New Orleans’s history, homebuilders kept to the high ground for the simple reason that if you built homes in the swampy lowlands, they’d eventually get flooded. In the housing boom after World War II, though, developers grew less cautious about the risks of low topography. They filled in the wet land north of downtown and created the pleasant residential district of Gentilly.

With this claim staked, the city followed up with a series of fortifications to keep out the waters. These concrete barriers work pretty well at blocking river and lake water and most hurricanes, but they can’t stop rainwater, says Mark Davis, director of Tulane’s Institute on Water Resources Law and Policy. Instead, New Orleans relied on a vast system of pumps to keep rainwater from filling up its low-lying districts.

But years of pumping have dewatered the soil, causing the land to sink relative to the surrounding water and making the process of staying dry even more complicated. After the devastation of Katrina, which submerged Gentilly along with many other districts, the city decided to chart a new course. “What’s being tried now are the ways we can store water so we don’t have to continually buy bigger pumps and bigger canals,” Davis says.

And now for something completely different

The Gentilly Resilience District proposes to retrofit the area with a series of interventions to filter and store rainwater in public land, while helping private homeowners protect their property from runoff. But the city wants these efforts to do more than manage water: they’re designed to simultaneously strengthen the fabric of the community and generate economic opportunities. That caught the attention of the folks at HUD doling out money left over from Hurricane Sandy relief in the National Disaster Resilience Competition.

“It’s huge—it’s really a down-payment on the future of the city,” says New Orleans Chief Resilience Officer Jeff Hebert. And not just huge for Gentilly: “The way we designed our submission was to concentrate these efforts in one area of the city in order to prove its viability and then transfer it to other parts of the city.”

The Gentilly proposal developed out of a resilience strategy Hebert’s office published in 2015, which in turn drew heavily on the 2013 Greater New Orleans Urban Water Plan. That document, profiled in detail by The Atlantic, established the philosophy of working with water instead of hiding it and banishing it from the city. (They even nailed down the URL before some other city got to it.)

One flagship project that made it from the water plan into the HUD grant is the Mirabeau Water Garden, a 25-acre site that will be turned into a natural filtration system capable of absorbing 1.23 million cubic feet of stormwater from the surrounding streets. Hebert says the HUD money will help the city design this park to be beautiful and educational, beyond its flood-mitigation function. The Resilience District will also turn portions of the canals into public waterfronts by demolishing the drab concrete walls that have long hidden them from view.

The largest item in the budget will be more than $90 million for a network of interlocking canals and water-absorbing parks in the neutral grounds—the wide medians that run through the larger boulevards of New Orleans. The goal is to make the public lands more attractive for recreation while expanding the city’s capacity to absorb stormwater.

This rain garden in the Gentilly neighborhood of Filmore Gardens was finished in 2014. It collects rainwater and drains it through native Louisiana plants, while serving the neighborhood as a mini park. (New Orleans Redevelopment Authority)

Since the transformation has to occur at all scales, as Hebert says, the Resilience District will support a series of neighborhood-level street overhauls and will use $7 million to support low- and moderate-income homeowners in flood-proofing their property with landscaping and elevating the house.

David Waggonner, the architect who spearheaded the urban water plan, hopes the water-centric installations will catalyze the growth of neighborhood centers in the generally suburban Gentilly area, which in turn will drive more revenue for the city. “Cities can’t exist without revenue,” Waggonner tells CityLab. “Part of it is to get more taxpayers, more utility users, more density in this key area of the city, and to use the physical changes to spur that.”

A sea change

The “living with water” philosophy is poised to guide development in Gentilly on a scale not yet seen in the U.S. It’s already practiced expertly by the Dutch water managers in Amsterdam and Rotterdam, who advised New Orleans in crafting the water plan. Copenhagen adopted a “green and blue approach” to adapt to climate change without relying on more sewage and pumping.

On the American side the idea is still gaining traction. Philadelphia committed to a $2.5 billion, 25-year green infrastructure stormwater treatment plan. Seattle wants to absorb another 700 million gallons of stormwater runoff by 2025. Hoboken won a $230 million HUD grant after Superstorm Sandy for a citywide system designed, in part, to store and discharge floodwater. Hebert says the Gentilly resilience work will be completed between 2019 and 2022, making it the first large-scale urban transformation of its kind in an American city.

It’s too early to know how it will turn out. “Is it possible that foolishness and corruption will arise here?” Davis asks. “Yes, just like any public works project. We have to watch for that.” And, Davis notes, with the installation of all these bodies of water the city will have to grapple with a new source of mosquito-born illnesses and even drowning risks. But if the Gentilly project pulls off a success, the city that was once the textbook case for storm-based calamity could write the textbook on how to avert the next flood.

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