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How these New Orleans nuns helped turn their convent into a beautiful, flood-preventing urban wetland

The 25-acre Mirabeau Water Garden will be one of the country’s largest urban wetlands, managing stormwater and easing the workload of the city’s current drainage system—all thanks to the Sisters of St. Joseph.

How these New Orleans nuns helped turn their convent into a beautiful, flood-preventing urban wetland
[Image: courtesy WBAE]
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When Sister Joan Laplace returned to New Orleans after evacuating for Hurricane Katrina, she was struck by the destruction in the city. She saw debris piled up on one main boulevard—house shingles, air conditioners, and refrigerators amassed into a nearly 30-foot mound—and thought it was like seeing “the city piled up in a trash heap.” Then she got to the 25-acre property that her congregation, the Sisters of St. Joseph, owned in the Filmore neighborhood in Gentilly, an area bordered to the north by Lake Pontchartrain and right next to New Orleans’s 1,300-acre public City Park. The Sisters had owned that land since the 1950s; it was home to their convent and provincial house, where those in the ministry lived and were trained.

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The once well-kept grounds were torn up, the building bedraggled; the first floor had flooded and was badly damaged. Ultimately, this was the beginning of the end for that provincial house, but it was also the beginning of a new project. Soon after Katrina, the Sisters would begin working on a way to give those 25 acres a second life, and help protect the city from future storms.

[Image: courtesy WBAE]

“To see the devastation, to see how little prepared we were in that city to take care of the people when they needed it was extremely difficult,” Laplace, 79, says of Hurricane Katrina. She was raised in New Orleans and had entered the Sisters of St. Joseph’s community at that particular building in the early 1960s. Less than a year after Katrina, in August 2006, lightning struck the roof, sparking a fire and leading to water damage on the second story. All that destruction to the building, along with a shrinking number of residents—at one time around 150 people lived on site, but at the time of Hurricane Katrina, there were only around 30—essentially spelled the end of the convent. The remaining sisters were getting older; they couldn’t care for—and didn’t need—all that land.

Joan Laplace (center) with other Medaille Sisters. [Image: Congregation of St. Joseph]

The Sisters didn’t sell it off to developers right away, though Laplace says developers would have “grabbed it very quickly.” (It’s the largest parcel in New Orleans under single ownership.) They considered it, she admits, because the congregation was low on funds. But the Sisters had recently merged with six other Sisters of St. Joseph communities across the country, which helped their finances, and put them in a position where they didn’t need that money right away. Instead, by coincidence, they were connected with the architecture firm Waggonner & Ball, which was already doing work to repair the city post-Katrina through its Dutch Dialogues, which looked to take advice from the Netherlands for how to ensure New Orleans could weather its next storm.

Mirabeau Provincial House, 1955. [Photo: courtesy Congregation of St. Joseph]

Waggonner & Ball needed a site for a flood mitigation project, and the Sisters had a site to give. They leased the 25-acre parcel to the city for just $1 a year and one condition: that it be used to “enhance and protect the neighborhood.” Soon, it will be the site of a new urban wetland called Mirabeau Water Garden, which will help manage storm flooding in one of New Orleans’ lowest-lying areas.

City officials are soliciting construction bids for the project in the first quarter of 2020, and construction is set to start by this summer, but the Sisters first connected with architect David Waggonner back in 2006. It’s been years of meetings and conference calls and coordination with the Federal Emergency Management Agency (the initial phase of the project, up to summer 2021, is funded by a FEMA Hazard Mitigation Grant Program) to get to this point.

“As sisters, we had no idea what we were getting into,” says Laplace. “We were just trying to say, ‘This is a great piece of property, we don’t need it, we’re too small . . . So what are we going to do?’ We kept praying about that, and then David Waggonner and his firm came up with this idea and asked about the possibility of doing it there. We thought this was an answer to our prayers.”

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Joan Laplace (center) at Mirabeau in 1967. [Photo: courtesy Congregation of St. Joseph]
When complete, the Mirabeau Water Garden will be one of the country’s largest urban wetlands, managing stormwater and easing the workload of the city’s current drainage system. “The idea is to manage water where it falls and not pump it out of the city as much as we can,” says Ramiro Diaz, senior project designer with Waggonner & Ball. New Orleans has long managed stormwater by pumping it out of the city, but that system gets easily overloaded.

The Mirabeau Water Garden will have the capacity to store 10 million gallons of water, diverting a deluge of stormwater from hitting the city’s drainage system all at once. When rain falls, that water will be redirected from the city’s pump system into the Garden; the Water Garden’s design includes various elevation levels throughout the 25 acres and that incoming water will fill those lower-elevation areas, forming an artificial lake within the site, with a path that remains dry so visitors can walk around it. That water will then slowly trickle back into the city’s drainage system after the storm, when it can handle more volume.

[Image: courtesy WBAE]

The design will also feature trees planted up on mounds, with those areas connected by bridges, so that visitors can navigate the site even when it’s wet. A hardwood forest will be built on one piece of the land as a habitat for birds and other creatures. The architecture firm is also working with City Park, right next to the Mirabeau land, to facilitate how that land can also take water that would otherwise go into the drainage system.

Heavy rains have led to more frequent flash flooding in New Orleans. A July 2019 thunderstorm dropped more than six inches of rain an hour on some areas of the city; six inches of rain dropped on 20 acres is more than 3.2 million gallons of water. For the city’s drainage system, that can be too much. Currently, all the water in Gentilly goes to one pipe station, first captured in catch basins, then through pipes into underground canals that pump the water out of the city. For the Mirabeau Water Garden, though, a typical storm event may only add a few inches of water to those lower-elevation basins; it’s meant to handle really large storms—those “10-year floods”—at which point the basins will be filled, creating an artificial lake.

[Image: courtesy WBAE]
“This idea of using water management projects as an amenity rather than just, say, a hard engineering project is something that we certainly would say we’ve learned a lot from the Dutch,” says Diaz. “If we’re only thinking about drainage ditches and underground things, yeah, sure, we can do infrastructure taxes, but it’s harder to get people to take ownership of that. But a park people can own and want to use, and, you know, why not have parks be something that hold water? Right now, most of the parks in New Orleans actually drain into the city, when they should be the other way around.”

The Mirabeau Water Garden is also in a unique place geologically, Diaz says, and that will help stormwater infiltrate the land, rather than only sitting on top. Most of New Orleans was built on swampland; a ground made up of clay and peat means falling water doesn’t drain well, and instead sits on the surface, leading to floods. Underneath the Mirabeau Water Garden site are former barrier islands, with only a few inches of clay above sand; water infiltrates sand much better than clay, so water will be better absorbed into the ground there, bypassing the drainage system.

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Easing the burden on the New Orleans drainage system—which is part of what failed during Katrina—is key to mitigating future flooding. The drainage system can only handle so much, and as storms get more intense and rain comes down really fast, it overloads the system, leading to flash floods. In New Orleans, “there’s only so many pipes and so many catch basins and so much capacity in the system, and the pumps only can pump so much,” Diaz says. “So either we need to build giant freeways for water and bigger pumps, which is unfathomable . . . or we could try to manage it where it falls and ask everybody to do a little bit on their property.”

New Orleans’s drainage system has another big flaw: it’s constantly sinking the city. As part of the natural water cycle, some water is always stored in the soil—how much depends on how porous that soil is. The city’s drainage system is so effective that as it removes stormwater, it also removes this groundwater from the soil, and when the soil dries out, the space where that groundwater was turns into air pockets. The soil particles settle, consolidating that space, and the ground sinks lower and lower, exacerbating the flooding problems and creating a dangerous cycle.

“The Dutch alerted us to this,” Diaz says, and that’s what prompted the firm’s Dutch Dialogues, which were in collaboration with the Royal Netherlands Embassy and the American Planning Association. Like New Orleans, much of the Netherlands is below sea level. All those canals in Holland are not just for water management as it relates to flooding, but to manage the groundwater, as well. Part of the strategy with the Mirabeau Water Garden, and the other projects that are part of Waggonner & Ball’s Living with Water initiative, is to maintain the groundwater it at the correct level instead of draining it all out of the soil.

“When we started doing this Dutch-inspired water management work in New Orleans, it’s really a renovation project for the city. We’re looking at how to integrate water into the existing urban footprint,” he says. Even though it’s not even built yet, the Mirabeau Water Garden design has already been used as an example for other cities. People are already pointing to this as a model project, and even the Sisters see how it could benefit more places than just their once-home.

“I’m sure all cities have their issue with water. In this case this particular project is about stormwater management, when the system is flooded over and can’t handle it, and so this becomes a retaining place until it can be released back—either it subsides into the Earth or into the system,” says Laplace. “Certainly whether you’re in Kansas or Michigan or wherever you are, there’s flooding at times, and so I think it does have a specific relationship in that effect to almost any city in this country that has stormwater issues—and not just this country, but everywhere.”

It’ll still be years before the Mirabeau Water Garden is ready to welcome visitors, or water. The city plans to begin construction this summer, a city spokesperson said, and construction of the FEMA-funded portion of the project will conclude summer 2021. There’s also a few U.S. Department of Housing and Urban Development-funded components to the Water Garden, and design of those, which will include educational spaces, is ongoing, the spokesperson said, and includes interactive community engagement. Then there’s the landscaping elements, and the time it takes to grow all the trees and plants on those 25 acres. “Green infrastructure projects are not turnkey,” Diaz says. “You don’t build it and move in the next day.” One area of the land is planned to be set aside as an homage to the Sisters, featuring a preserved piece of the convent’s original terrazzo floor that was recovered from the site, with a symbol for the Sisters of St. Joseph on it.

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Laplace is eager to see the revitalization of this land, and she says Sisters in congregations all across the country are praying that the Mirabeau Water Garden project will be successful.

“I think one of the things—that hopefully the city as a whole is learning—that we learned from David Waggonner and his team was the expression that New Orleans has never learned to live with the water, in harmony with the water,” she says. “We’ve always fought the water, which is true. I think that’s been our mentality, until this.”