No Small Feat—Stormwater and Corridor Enhancements in The Big Easy 

The city of New Orleans is almost as famous for its considerable rainfall events as it is for its legendary food, music and culture. The devastation of Hurricane Katrina made worldwide headlines, but city residents continue to cope with smaller-scale water inundation on an annual basis. Due to the coastal location and bowl-like topography of New Orleans—about half of the city is below sea level—even a 1-year storm is a significant event, to say nothing of the 100-year storms that cities plan for. For over a century, New Orleans thrived despite these challenging conditions by aggres­sively pumping water out of the city into Lake Pontchar­train.  

In the aftermath of Hurricane Katrina, extensive federal funding was made available, sparking the first opportunity to implement large-scale green infra­struc­ture in the city. The result was a commitment to transform the city’s stormwater infra­struc­ture, turning water from a nuisance—and at times a risk—into an enhancement. As part of this effort, CDM Smith was retained by the New Orleans Rede­vel­op­ment Authority (NORA) and worked in partnership with the city to develop several compre­hen­sive corridor improve­ments that provide enhanced safety, acces­si­bil­ity and resiliency.  

The Pontilly Stormwater Hazard Mitigation Grant Program project has strength­ened, beautified and connected the Pontchar­train Park and Gentilly Woods communities. Histor­i­cally, these communities were racially segregated, with Dwyer Canal serving as a dividing line. Today’s residents see a vision of a single, connected neigh­bor­hood, with a stronger drainage system, better water quality and more resilient infra­struc­ture. The CDM Smith team repurposed dozens of unrestored residential lots left vacant after Katrina and other existing green spaces into urban pocket parks with stormwater detention and wetlands. Street-side bio-retention cells redirect stormwater into detention facilities, preventing the system from being overwhelmed. Meanwhile, green alleyways with walking trails, lights, and benches enrich community life. 

“What I really love about this project was that it was requested by the neigh­bor­hood, a real grass roots project,” said Jessica Watts, CDM Smith civil engineer and green infra­struc­ture expert. “The neigh­bor­hood came to the rede­vel­op­ment authority and asked to do something green and inventive to deal with their stormwater issues in a new way. The entire project arose from there.” As Watts relates, local passion and state-of-the-art engineering expertise came together on this project. “Every New Orleanian knows you can’t have standing water because mosquitoes will breed. So, we designed filter boxes that trickle water out slowly, and it’s all gone within 48 hours. Each pocket park is like a little relief valve that takes stormwater pressure off the overall system. But, it’s not just about how it works as engineering—it’s about how the community can interact with what we’re designing.” 

The DPS 01 Drainage Upgrades and Green Infra­struc­ture Project is the largest in the city in terms of total area. The project will include over $50M in improve­ments to the Central City, Garden District, Lower Garden District, St. Thomas Development, Touro, East Riverside, and Milan neigh­bor­hoods. This project was developed in close coor­di­na­tion with local stake­hold­ers, with a vision built upon workshops with stake­hold­ers and many hydrologic and hydraulic modeling iterations to find the right solutions for these neigh­bor­hoods. 

The CDM Smith team is working to reduce localized flooding through a network of traditional (“gray”) and green infra­struc­ture improve­ments throughout the project area. Large storage areas are inter­con­nected by improved drainage conveyance, delivering stormwater runoff to where it can be stored and gradually released once the pumping system can handle it. Meanwhile, a constel­la­tion of smaller-scale green infra­struc­ture improve­ments intercept, slow down, and store stormwater. Cross-connections between storage areas allow excess stormwater to be equalized between them, so that no single area becomes dispro­por­tion­ately overloaded during a storm event. Not only will the DPS01 project benefit the neigh­bor­hoods in the project area, it will also take pressure off shared drainage pipe as well, allowing neighboring areas to drain while the project area retains stormwater. 

Just as traditional stormwater management methods could not solve the problems posed to the city of New Orleans, basic trans­porta­tion-related improve­ments were not compre­hen­sive enough to mitigate each roadway’s challenges. Working with CDM Smith, the team applied a complete corridors approach to enhance the overall func­tion­al­ity and appearance of the corridor via improve­ments in landscaping, bicycle and pedestrian services, safety, roadway reha­bil­i­ta­tion and drainage modi­fi­ca­tions.  

Baronne Street is the centerpiece of this concept; Watts calls it the “Cadillac prototype” as it incor­po­rates all aspects of green infra­struc­ture, resiliency, and improved multi-modal trans­porta­tion into one streetscape. Some site integration elements include: 

• An elevated bike track, which provides an added layer of safety by separating it from the driving surface, along with roadway improve­ments that utilize one-lane driving to reduce vehicle volume and add space for parking. 
• Urban bioswale and approx­i­mately 220,000 cubic feet of right-of-way subsurface stormwater storage to collect and filter stormwater runoff within the right of way.   
• Sanitary sewer, water, and drainage conveyance upgrades including adding a large drainage pipe to connect the area’s three large canals.  
• A combination of street basins and permeable, ADA-compliant paver crosswalks to create safer “green inter­sec­tions” for pedestrians by narrowing the vehicular travel lane. This both reduces the distance a pedestrian must travel within the vehicular path and creates a natural slowing in traffic velocity, which was partic­u­larly important as several inter­sec­tions are adjacent to a popular park. 

And because New Orleans has areas of historic designation, Watts and her colleagues worked with the city’s historic preser­va­tion officer to incorporate as many historic right-of-way elements into the final design, including historic streetcar rails, granite curbs, and the iconic street name tiles.  

The CDM Smith team also worked with the city’s Department of Parks and Parkways to make sure to utilize as much open green space as they could without removing the space from its function. “We added subsurface storage tanks to parks and playgrounds and replaced the turf and equipment so that the park could be used as it was designed to be.” said Watts. “I’m partic­u­larly proud of our work at the Van McMurray Playground, where the CDM Smith team worked in concert with the adjacent senior center, daycare and high school to improve each group’s use of the shared space and reprogrammed the areas to meet multi-gener­a­tional needs.”  

With the development of green infra­struc­ture and complete corridor projects throughout the city, New Orleans is creating resiliency through community involvement and innovative design.