In New Orleans, nuns are shepherding a former Catholic convent that was badly damaged in Hurricane Katrina towards becoming a 25-acre urban wetland, one of the largest in the United States. This month, city officials will begin to solicit construction bids for the estimated $30 million project, called the Mirabeau Water Garden, E&E News reports.

Flash floods have become hugely problematic over the last 20 years in New Orleans, because much of the city sits below sea level and more powerful storms now pass over the city. Even average rains can cause flooding, but big storms can deliver 2 to 3 inches in a single hour.

The Mirabeau Water Garden will have the capacity to absorb almost 10 million gallons of stormwater runoff from the surrounding neighborhood. The water will still trickle down into the city’s old drainage system, but filtering through the wetland will mete out the water from even the largest deluges more gradually, preventing storm drains from becoming overwhelmed.

Other cities have implemented similar strategies to intercept, store and slowly release stormwater, but Mirabeau is distinct for its size and for highlighting how, even in dense cities, underutilized or abandoned structures can be repurposed to enhance flood resilience and provide other public benefits.

Experts say New Orleans has undertaken similar water management projects on a smaller scale, but that Mirabeau is the most substantial and symbolic to date. Part of that symbolism is how fundamentally the project’s approach to managing water differs from the $14.6 billion levee system built by the U.S. Army Corps of Engineers after Katrina. That beefy levee system is now predicted to stop providing adequate protection by 2023 because the heavy structures are sinking and sea levels are rising due to human-caused climate change.

The project was conceived by the Sisters of St. Joseph, who had occupied the convent for many years. For these nuns, commitment to their faith entails a lifetime of service but also stewardship of the planet. After the property was damaged by flooding and fires the sisters opted not to rebuild the convent or sell to developers.

"What we were doing is praying for an idea that would allow this land to continue ministering" to the neighborhood, Sister Pat Bergen, a leader of the religious order headquartered in La Grange, Ill., told E&E News. "I mean, this land had been prayed upon for years, and we already had a commitment to save and restore planet Earth in light of climate change. So it seemed like a good fit."

The nuns commissioned a design firm to create a water management project aimed at fostering environmental, educational and spiritual well-being, and leased it to the city of New Orleans for $1 on the condition that the property be used to preserve and protect the environment, enhance local quality of life and reduce flood risk.

"With a 10-year storm event, which we see every couple of years now, this project will protect a lot more homes from water," Ramiro Diaz, of Waggonner & Ball, the architecture firm designing the Mirabeau project, told E&E News. "And even with the one- and two-year events, over the long run this will provide greater benefit than the massive flood eradication projects we've seen since Katrina."

Correction: This story has been updated to reflect that the levees and other coastal flood mitigation structures built by the U.S. Army Corps of Engineers after Hurricane Katrina are currently effective but are predicted to become increasingly less so beginning in 2023.