Innovation drives Wilson's stormwater management

Rain is something most people don’t think twice about, until it negatively affects their lives by flooding homes, damaging property and impacting essential services.

Heavy rain events are a significant problem in North Carolina that likely will get worse as a result of climate change, experts warn. According to Riskfactor.com, which evaluates the risk of flooding in each state, there are 636,641 properties in North Carolina that have a greater than 26 percent chance of being severely affected by flooding over the next 30 years.

The City of Wilson has taken a proactive approach to stormwater management and infrastructure by developing innovative programs to mitigate residential and municipal flooding, carefully evaluating projects so they have minimal impact on residents and businesses, and educating citizens on what they can do to help.

Overseeing the city’s stormwater management efforts are Bill Bass, Public Works Director, and Noah Parsons, Water Infrastructure Division Manager. “Stormwater is whatever falls from the sky, and we have to manage it once it’s on the ground,” explained Bass. “We have to make sure that we don’t have peak flows that our system can’t handle, as well as deal with excessive runoff.”

Another concern, said Bass, is stormwater erosion, which can result in unwanted sediment in local streams, as well as property damage.

Most municipalities have rivers, streams and other waterways running through them, and Wilson is no different. Of greatest concern is Hominy Swamp, a creek swamp that runs through the center of town.

“A big issue with the Hominy Swamp is the topography, because we’re pretty low,” Bass said. “The Hominy Swamp is about 18 miles in length, but there is about a foot of fall over those 18 miles, so you can imagine the difficulties we run into with water flow through some of the older sections of town and through older, undersized infrastructure [during heavy rain storms].”

And therein lies another issue. According to Parsons, much of Wilson’s underground stormwater infrastructure is 70 to 80 years old, and in frequent need of repair or replacement. “We look at how we can retrofit stormwater control measures during the redevelopment process to improve that older infrastructure,” said Parsons. “That is something that Wilson has gotten pretty good at, and sets us apart.”

Stormwater management also impacts municipal growth in that developers are required to incorporate stormwater control measures into their projects, which may range from a pond at a park to ditches and swales that carry water to a retention area.

Among other benefits, such mitigation efforts help prevent the release of unwanted nutrients, such as nitrogen, into local waterways, where they can adversely affect plants and animals. Better still, when excess nitrogen is removed, the city receives credits from the state – credits that can be sold. "Wilson is the first municipality to open up a nutrient offset bank by which we can sell these credits and generate a return on our project, then put that into our next project to help push tax dollars even further, making it more efficient,” said Parsons.

Developers may purchase nitrogen credits as part of their deal with the city. “We want to entice development to benefit the community,” said Bass. “That’s giving something back because the value of that nitrogen credit is small compared to the tax base of a large business coming to town.”

Over the past few years, Wilson’s Water Infrastructure Division has put forward some cutting-edge ideas to make stormwater management more efficient. One project involved the construction of an underground water storage facility beneath a parking lot scheduled for resurfacing, which helped slow storm flow velocity and reduced flooding in the area. The project resulted in an American Public Works Association Infrastructure Project of the Year Award.

“By doing this while the parking lot was unused, we were able to keep streets open to business, and we didn’t have to upsize the existing pipes in the area, which would have disrupted traffic and resulted in huge costs,” said Parsons.

Another innovation involved converting the city’s downtown alleyways into inviting greenways for pedestrians, while also making the paths better able to handle stormwater runoff. “We used permeable pavers instead of asphalt so now the water soaks into the ground instead of just running off,” observed Parsons. “This helps alleviate localized flooding. We’re also incorporating more cisterns and rain gardens. Our goal is projects that are useful to the community while addressing water quality and quantity issues.”

In part because it has become such a leader in stormwater innovation, Wilson hosted the 2023 Southeastern Regional Stormwater Summit on March 14. The hybrid event attracted more than 100 in-person attendees from across the northeast, in addition to many more who attended virtually.

The citizens of Wilson can assist with stormwater management by participating in the city’s rain barrel program. The 55-gallon barrels collect roof runoff, which can be used to water plants and gardens. “We’ve sold more than 450 rain barrels at cost, so now with each storm we’re collecting more than 20,000 gallons of water that is reused rather than discharged into a creek,” said Parsons. “That’s just one small project, one barrel at a time, that has a pretty good impact citywide.”

Bass and Parsons understand the negative impact that stormwater can have on the citizens of Wilson, and are pleased with the solutions they have been able to enact to date. But they know the fight continues.

“If you’re worried about flooding every time it rains, that’s very stressful,” said Bass. “Our goal is to remove that negative impact and make our community a better place. We try our best to think outside the box and do things that may be outside the norm. We don’t limit ourselves to things others have done. We take those things and see how we can use them to improve our city.”