Mirabeau Water Garden
When the Sisters of St. Joseph returned to their convent after evacuating New Orleans for Hurricane Katrina, they found the property in shambles. Water had flooded the building’s first floor, damaging it badly, and its parklike grounds were a disaster. Adding insult to injury, less than a year later, or perhaps signaling divine intervention, a lightning strike set the building on fire, leading to further water damage. Although they thought about selling the property, the sisters began exploring how to give the 25-acre site a new life—one that would offer the Gentilly neighborhood new protection from future storms.
They were introduced to Waggonner & Ball, an architecture firm that was already working to repair the city’s infrastructure through the Greater New Orleans Urban Water Plan. That vision was embraced by the sisters as one that, in their words, “would manifest the holiness and the beauty of this land … and evoke a huge systemic shift in the way humans relate with water and land.” Ultimately they decided to lease the property to the city for 100 years at $1 per year.
Now, with Sherwood Design Engineers collaborating as civil engineers, the property has been reimagined as Mirabeau Water Garden, which will be one of the country’s largest urban wetlands. It features an innovative approach to site design and stormwater management that will reduce stress on the city’s existing drainage system. Rather than battling floods in the low-lying district by pumping water out, at Mirabeau water will be pumped in—filling a new retention pond that can store up to 10 million gallons of water.
Water stored in the park will offset neighborhood flooding while helping to restore the groundwater levels in an area of the city that has experienced severe subsidence—a sinking of the land caused when organic soils dry out. Pumping water off the site makes the problem worse, causing soil to shrink and then swell again when it rains. This shrink-swell cycle severely damages streets and building foundations.
When the project is completed, much of the site will be covered in native meadow grasses that will absorb stormwater runoff and filter pollutants. The grasses’ filtration will be complemented by a series of bioswales that slow and collect rainwater.
A new perimeter underdrain captures the groundwater and pumps it into the retention pond. The response is specific to New Orleans’s unique conditions, where the elevation is so low that a gravity-driven solution is not feasible.
In addition to addressing chronic flooding, the site is being developed to revitalize the surrounding neighborhood by providing a place for recreation. Most of the site will be a landscaped zone dedicated to stormwater management. But part will be open space that can be used for picnicking or tossing a ball. A boardwalk is also planned to circle the lower zone, encouraging people to enjoy the site even when it is inundated with water.
From the beginning, the team has also woven an educational mission into the project. The plan calls for interactive features that explain the site’s role as part of an integrated water management system that diverts flood water from streets and homes and stores them in the landscape. The first phase includes a pump station and maintenance building, which will be augmented by a community center or farmer’s market for the community’s benefit.
The design solution at Mirabeau Water Garden addresses bigger questions about how cities repair themselves. In a place like New Orleans, where many houses have been abandoned, there’s a new opportunity to reclaim parts of the city as public realm that can be repurposed for the greater good—as open space, pedestrian pathways, and community services.
Overall, the project is a unique combination of engineering and landscape-based solutions that will redirect stormwater from the city’s drainage system and runoff from neighboring streets. It will store and clean the water as it flows through the landscape, allowing it to soak into the sand layer beneath the site or be fed gradually into the city’s drainage system once a flood threat has passed.
As a living laboratory, Mirabeau Water Garden is a model for other open spaces in New Orleans and for flood-prone communities across the country
