Urban stream restoration can be a real challenge. Urban streams tend to be constrained by utilities and private property. The water has significant power and can be erosive. Invasive and exotic vegetation often runs rampant. And perhaps most importantly, urban streams are surrounded by property owners with widely divergent degrees of enthusiasm for projects in their backyards.
Officials in three East Coast cities can attest to the challenging nature of urban stream restoration. Yet these three communities are successfully completing projects that are improving water quality and restoring critically impaired waters, all with the support and enthusiasm of adjacent property owners.
Upper McDowell Creek - Charlotte, North Carolina
The Challenge
McDowell Creek in Charlotte, North Carolina, is one of two tributaries that feed into Mountain Island Lake, which provides much of the drinking water for the Greater Charlotte area. According to state and federal officials, McDowell Creek was critically impaired, said David Woodie, PE, a project manager with Charlotte-Mecklenburg Storm Water Services.
Creek banks had eroded and were overrun with poison ivy and kudzu. Following rain events, rushing water swept sediment downstream, threatening to clog waterways. And although the area was becoming a flood hazard, adjacent neighbors weren't completely on board with the stormwater management plan, according to Woodie.
Approximately 1,600 LF of streambed needed protection and restoration, and the water quality needed to be improved. "We needed to re-establish a natural channel and vegetation so McDowell Creek can basically sustain itself for the long haul," said Woodie. In addition, Charlotte-Mecklenburg needed to convince neighbors that the improvements were necessary and beneficial.
The Solution
To restore Upper McDowell Creek to its natural state, Charlotte-Mecklenburg Storm Water Services implemented stormwater best management practices (BMPs) - specifically, stream stabilization and restoration for 1,600 LF of stream bed - within the town limits of Cornelius, North Carolina.
The natural shape has now been restored on both sides of the stream. "Step pools" have been installed to dissipate energy at areas of concentrated flow and to prevent future erosion. These structures are lined with stone and supported by soil, seed and binding degradable fiber. "A rain garden is positioned on the property to capture the 'first flush' stormwater from an adjacent municipal property, allowing it to pond and soak into the ground gradually," explained Kerry Bray, EI, of McKim & Creed.
Mecklenburg County bought a home that had been flooded by the stream and demolished it, donating windows, doors and usable lumber to Habitat for Humanity. A pocket wetland is now situated on the site where the home once stood. Cross vanes in the stream help slow water flow during heavy rains, and sections of rock-lined stream beds create riffles that help aerate the water and filter out sediments.
"We're also reducing nitrogen, phosphorus and total suspended solids (TSS) levels in the headwaters while providing utility and riparian protection and enhancing aquatic habitat," said Tim Schueler, PE, senior project manager with McKim & Creed who oversaw the design of the new stream structure.
To garner public support, Charlotte-Mecklenburg Storm Water Services educated property owners through a series of public meetings. "We had several projects already on the ground that helped educate what it would be," said Woodie. "This being so impaired and a lot of invasive vegetation, like kudzu, people were open to remove all that. Then they became excited about the project."
As the project nears completion, Schueler reports that "adjacent owners downstream have now said, 'Why don't you expand the work?'"
Construction costs for McDowell Creek totaled $235 per linear foot. The project was funded through a grant from NCDENR and EPA-Section 319, as well as local funding from both Mecklenburg County and the town of Cornelius.
Doctors Branch - Wilmington, North Carolina
The Challenge
"There are always three reasons that we pursue a capital drainage project: 1) flooding, 2) water quality and 3) the ability to make connections within our system and improve those connections," said David Mayes, stormwater services manager with the city of Wilmington, North Carolina.
In this pre-restoration photo taken in December 2009, Doctors Branch has engulfed nearly all the backyard space at this home.
Doctors Branch, a coastal stream that drains approximately 288 acres, was experiencing two of those three issues; specifically, water quality and connectivity.
Erosion was threatening the property of nearby residents. Water quality was suffering and, in places where the stream crossed private property, the city didn't have easements to enact stormwater management protection. "We need to connect the dots with public easements and restore the stream back to its natural and manageable state," said Mayes.
But while one resident "was very much in favor because his house was the most threatened, others were cooler [to the project] because it was going to significantly change the way their backyards looked," Mayes said.
The Solution
To address the water quality and erosion issues, engineers performed a full stream restoration based on the natural channel design for Doctors Branch. The restoration included Rosgen Priority 1 and 2 grading plans, new storm drain easement locations and planting plans.
An added bonus was a mitigation credit. "Because of the way the project was designed and subsequently permitted, we are able to use environmental benefit for mitigation credit that we are able to use in other parts of the city. McKim & Creed was instrumental in making sure that occurred. This was not an original goal of the project but it certainly has tremendous value," said Mayes.
The city addressed residents' concerns in public meetings that showcased the benefits of the project, like how elevating the rise of the stream would restore backyards and provide usable space people didn't have before, according to Mayes. Nearby residents "were losing their lawns but, on average, ended up gaining quite a bit of land back," said Schueler.
"Natural stream restoration was not only the best choice because of the benefits we're getting, but it's the right thing to do because of the long-term water quality benefits," said Mayes.
The original channel alignment was shifted approximately 20 feet to the left to protect existing homes near Doctors Branch.
A priority 1 restoration reconnects the channel to its original floodplain.
College Gardens - Rockville, Maryland
The Challenge
In Rockville, Maryland, urbanized runoff had significantly enlarged and incised the College Gardens Tributary, a stream that ultimately flows into the Chesapeake Bay. Stormwater management for the tributary had been approved in 1999, but residents were opposed to the plan. They feared any stormwater improvements would involve unsightly structures that would detract from their neighborhoods, and the project was put on hold.
Located proximate to the tributary is College Gardens Park, a 6.2-acre urban park featuring a playground, basketball court, paved trails and a shelter. The park is an important part of the community but was in sore need of a facelift.
"First and foremost we needed an effective stormwater management facility," said Lise Soukup, environmental engineer with the city of Rockville. "We also needed to address the water quality goals and downstream erosion. And because we were retrofitting the park and going into established neighborhoods, we had to come up with a design that fit the location."
The Solution
To accomplish its stormwater needs, the city of Rockville retrofitted a farm pond at the park with an extended detention wet pond that has become a "showcase pond," said Soukup.
The pond features a fountain, bridges, decks, and extensive landscaping. According to an article in Water & Environment Technology, specific goals for the pond retrofit include "a 42 percent reduction of sediment being generated by streambank erosion, along with an 80 percent removal of TSS from water exiting the new pond. The pond would reduce peak storm flows by 60 percent for a 1-year storm, 40 percent for a 2-year storm, and 15 percent for a 10-year storm."
The pond is the central component of the park renovation. The eroded basketball court has been relocated, and walking paths and other amenities have been approved and are now ADA compliant.
To gain community support, residents and the city "embarked on a year-long conceptual design and park rehabilitation evaluation, and that turned the tide," said Soukup. "We worked together for an intense nine months and proved that this was a valuable and necessary stormwater improvement project. There was a lot of honest and open discussion and we answered questions instead of saying, 'That's not relevant.'"
"Stormwater management in urban settings is hard to do, and you don't get many chances where you can put a surface stormwater pond in an established neighborhood," concluded Soukup. "We're thrilled we could do this in an aesthetic way that suits the community."
