The City of Fayetteville’s flood resiliency in the face of climate change: mapping 15 watersheds

Eric Suesz Eric Suesz December 12, 2023

11 min read

You’ll find dozens of US cities and counties named after Revolutionary War hero Gilbert du Motier, the Marquis de Lafayette, but the city in North Carolina was the first – and probably the only one he ever actually visited. Originally called Cross Creek by the Highland Scottish immigrants who helped populate it, Fayetteville was founded next to a body of water large enough and swift enough for commerce: the Cape Fear River. Like so many cities that grow up around rivers in hilly watersheds, some flooding is expected, but the waters are rising higher and more often than ever before as massive storms continue to batter the east coast of the US.

In the path of the storms

The city of Fayetteville, North Carolina has always had flooding issues, but it’s been getting worse as weather patterns have been changing. They were hit four years in a row by storms Matthew (2016), Irma (2017), Florence (2018), and Dorian (2019). 

Before the storms, they had been performing small-scale capital improvement plans with a modest stormwater fund, but those were small projects, upsizing a culvert here, tackling a neighborhood-based flooding complaint there. This succession of storms that resulted in catastrophic flooding in some parts of the city encouraged them to get proactive. 

“After this series of large events, our leaders directed us to accelerate the stormwater capital improvement program and expand city-wide with comprehensive watershed studies,” says Stormwater Project Manager Alicia Lanier. 

A “worst-first” approach that is also equitable

The city’s new Public Services Director Sheila Thomas-Ambat, who took over the reins of Fayetteville Public Services Department in 2018, had an ambitious plan: begin with an investment of $13M to accelerate their watershed studies with a highly data-driven approach and comprehensively evaluate stormwater problems before they arise. 

“My charge was to study the entire city – 100 square miles – within 5 years. The problem was, I had no data,” says Thomas-Ambat. “We needed to understand where we flooded, the severity of that flooding, and solutions to the flooding for the entire city.” Importantly, she also wanted to ensure that increased funding addressed stormwater flooding holistically, fairly, and equitably – and did not simply funnel resources to neighborhoods that hollered the loudest after a storm. 

Sheila is responsible for 187 employees and a $40 million operational budget that encompasses much more than just water. A long-time North Carolinian, Sheila is not only a water engineer with a big-picture-view of the possibilities of public works projects, she also has studied journalism and mass communication. This secondary qualification shouldn’t be discounted. Perhaps the biggest challenge in leading a municipality may be finding the right words, putting them in the right order, and presenting them with enough passion to gain crucial buy-in from politicians who also need to get their constituents excited about embracing change. 

“Sheila has a deep vision for what’s possible, having worked in Raleigh on their stormwater program. She has helped foster inter-departmental collaboration between Public Services and Emergency Management to develop water rescue maps so we can be better prepared for the next hurricane,” says Lanier. “Because they keep coming.”

Beginning is always the hardest part, but they knew up-front that trying to do it all at once was not feasible. “Studying all 15 watersheds in-depth and delivering the results as one enormous project would be slow and expensive,” explains Alicia. “Plus, it wouldn’t ensure that future work would proceed.” Instead of delivering a full city-wide plan as a giant document, they worked closely with Freese and Nichols to create a “worst-first” prioritization-based plan, evaluating, scoring, and ranking sub-basins to prioritize work that could be started quickly. 

Getting their assets organized

Before beginning individual watershed studies, they needed to comprehensively survey their stormwater assets across the entire city, including city-owned and maintained assets, drainage on state rights-of-way, and outfalls on some private property.

Freese and Nichols helped them create a comprehensive stormwater geodatabase to connect their separate data systems and assist with long-term planning and system performance evaluation. Existing information that was stored in shapefile and Excel formats were assimilated and translated into an ESRI geodatabase format to provide a framework for uniform formatting and storage.

Beyond making the greater project possible, the geodatabase also gave the city a more efficient framework for addressing its future asset management work. 

Combining 1D and 2D 

In addition to inventorying assets, they assembled an impressive group of consultants to help with modeling their 15 watersheds – an ambitious undertaking. This was the first time a North Carolina city has used this type of modeling at such a large scale, and the city, along with Freese and Nichols, wisely created a consultant management and standards manual to set the framework for hydrology and hydraulics and ensure consistency across everyone’s models. 

They chose HEC-HMS for overall hydrology of watersheds, along with HEC-RAS for primary system hydraulics, but it was especially important for them to model their secondary systems as close to real life as possible. 

“Freese and Nichols had used InfoWorks ICM in the past, and they created a comparison for us of the different tools we could use in this work, to help us justify an investment in additional software,” says Stormwater Engineer Ali Shallal, the city’s hydraulic modeler. “Ultimately, we decided: If we’re going to do something like this, let’s use the best tool.” 

Pull the slider to examine before-and-after HEC-RAS + InfoWorks ICM flood mapping results.

To successfully bridge their 1D and 2D models and gain deeper insights into the effects of flooding across the city, they used InfoWorks ICM so they could clearly visualize inundation and depth from 2-yr to 100-year storm events in the studied sub-basins. It was especially important for them to be able to quantify impacts to essential facilities, structures, disconnected structures, and roadways. They wanted to pay special attention to road crossings because that is often where the most common flood-related drownings occur according to the CDC – when people drive into hazardous floodwaters.

“By using InfoWorks ICM in coordination with other hydraulic and hydrologic software such as HEC-RAS and HEC-HMS,” says Thomas-Ambat, “we were able to precisely measure all of our project goals and prove – without a doubt – that our watershed planning would deliver positive outcomes for the community.”

Prioritization through collaboration

They came up with a highly structured methodology for ranking and prioritizing the work that relied on a city-wide, rain-on-mesh InfoWorks ICM model. But they also weaved in data that might have otherwise gone untapped. They tied together citizen flooding complaints from their legacy system and their institutional knowledge of roadway and neighborhood flooding concerns. 

With so much ground to cover, they needed to rank and prioritize sub-basins.

One difficulty with such a large project that employs so many consultants and gathers so much data is the cost of the assessment work itself. Once they had scored, ranked, and identified priority sub-basins within the watershed, they associated a cost with studying each sub-basin. By using a model-based approach to focus only on the prioritized sub basins, and not creating an entire city-wide plan in one massive assessment, Freese and Nichols was able to save the city $25 million in watershed studies. 

An early success: Blount’s Creek 

One of the largest and most developed watersheds in the community, Blount’s Creek, was modeled in the initial round of work by Arcadis, one of the many consultants working on the larger watershed plan. 

Thanks to the consulting guides prepared by Fayetteville to standardize the modeling across consultants, Arcadis helped them identify structures that would be impacted by flooding, as well as the extent of the flooding outside the stream banks, creeks, and yards. They discovered that the backwater effects of flooding from Blount’s Creek limited the ability of the stormwater collections systems to discharge during extreme storm events. No amount of money to increase pipe sizes was going to make a difference in those areas, and demonstrating this with a model means you can quickly pivot to another solution.  

In the end, taking all of their secondary modeling details into account, as part of the Russell-Person St. Bridges and Stream Enhancement, they chose to rebuild and extend four bridge sections and enlarge the floodplain for Blount’s Creek to provide additional floodplain storage.  This project was both the least intrusive to the community and offered the most environmental protection in relation to its cost.

It’s always flooded here. Both directions of a flooded Person Street in 1945.

Of course, putting together a plan doesn’t mean you’ll get funding. You need to make a good case by tailoring your presentation to the community. To provide the often-missing context of history, Arcadis Senior Hydraulics Design Manager Scott Brookhart was able to dig up a photo taken by his grandfather of a flooded Person Street in 1945. “I think it is so cool that I get to work on developing a solution for this area of Fayetteville,” says Brookhart.  

A solid social-equity approach

To secure much-needed additional funding, it helped the City of Fayetteville that many of their ambitious projects checked a lot of boxes for federal funding applications for FEMA’s Building Resilient Infrastructure and Communities (BRIC) program. All benefitting census tracts of the project met Justice-40 criteria, and all but one had CDC Social Vulnerability Index (SVI) scores above 0.93. They just needed to create a winning argument for the grant.

“What struck me as I looked at our goals was that I needed to rely on data to achieve them,” says Thomas-Ambat. “It is the power of data that connects people and processes – in this case it was flood resiliency data.”

Data for flood mapping can come from all kinds of sources, including 911 calls.

They were able to leverage their 911 rescue call data as part of the grant process to support the BRIC grant. They also included their Person Street “green street” – which incorporates vegetation, soil, and permeable pavement to slow, filter, and cleanse stormwater runoff – to show how the city understands and is embracing nature-based solutions. 

Adding layers of data that highlights inequality to their grant proposal was a big win for their project management practices. It can help increase the chances of receiving grants, but more importantly it sets the expectation that the work you do strives to consider historic imbalances when determining the allocation of future resources.

Presenting it all

Putting it all together, they were able to create side-by-side maps that showed the difference between existing conditions, highlighting a range of storm events from 2- to 100-year events, alongside their modeled map of the improvements using the same storm event data. Even better, they were able to show that the Russell-Person solution intersects with 10 other areas of concern, meaning that the resolution of work on this solution would reduce the flood impacts in 10 other areas. 

In the end, they were able to estimate a $24.7M benefit over 10 years in flood risk reduction and property damage. Their thoughtful, data-intensive approach really paid off. The Russell-Person solution was approved by the city council in 2022. 

Better prepared for the next storm

The entire program is still ongoing, but it has already achieved stellar success. The City of Fayetteville has developed over 200 proposed solutions in four of the 15 watersheds, allowing the city to prioritize areas of significant flood risk to focus on from those that didn’t have significant flooding. 

The work they did to present their program through a social-equity lens put them under consideration for a $14.7M FEMA BRIC grant for their Russell-Person St. Bridges and Stream Enhancement corner-stone project, which would essentially pay for the watershed master plan program. 

As Thomas-Ambat told an assembled crowd at Autodesk University, “Because of the technology and the processes we used in our FEMA application, we were able to show that we reduced the 100-year flood plain by 136 acres, eliminated three-and-a-half miles of impacted lane length, prevented more than 144 structures from flooding, and provided a $25M benefit in flood risk reduction and property damage.

A high-level view of the 15 watersheds with ICM flood validation points.

They continue to go further, publishing a flood map of the city on their website that depicts 100- and 500-year floods and creating a campaign to communicate risk and vulnerability across the community. 

When you consider the forecasts for future climate-related flooding, other riverside cities are going to need a template to follow to become more proactive in their flooding efforts. The City of Fayetteville’s dedication to an iterative and adaptive project management approach along with thoroughness and documentation provides a wealth of information and ideas for others to follow. 

If you need a map to lead the way to a comprehensive watershed study for your city, Fayetteville has done the work – and documented it thoroughly.

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