City of Frisco Erosion Study and Dominion Creek Trail Protection Project

The City of Frisco, Texas, has over 140 miles of streams within the city limits. In an effort to effectively manage the streams in the future, the City of Frisco engaged Walter P Moore to conduct an erosion control study as well as complete a protection project for the Dominion Creek Trail.

Walter P Moore performed the task of physically inspecting the entire stream network and creating an inventory of stream locations where conflicts may exist between the stream and the built environment.

One of the streams inspected early in the study was a large tributary of Panther Creek. The creek had several locations of erosion-related issues that were only addressed once identified. Citizens of nearby residential areas typically reported these erosion-related issues. Walter P Moore was called in to inspect the stream and provide a viable solution to the City of Frisco.

Additionally, a nearby recreation trail—the Dominion Creek Trail—runs parallel to the channel in the reach. As viewed from the trail, the stream was partially concealed by dense vegetation, therefore, the poor conditions were not immediately obvious to the engineers.

Because the scope of the study included viewing the stream reach from within the channel, the stream bank erosion from this vantage point was more evident compared to the view from the trail. The Walter P Moore team noted several signs of active erosion and slope instability, including the general steepness of the bank—nearly vertical—and the lack of vegetation along portions of the bank. The challenging location also occurred at a steep bend in the channel which made it more susceptible to erosion. As a result, the area was given a very poor score on the City’s rating system and put into a high priority category for rehabilitation.

Upstream from the trail, a second problem area was identified—an exposed manhole. Originally, the manhole had been built on the bank, but channel migration exposed the manhole to a degree that it was within the eroded channel.

Finally, a significant storm in April 2020 caused a rapid loss of the bank in the vicinity of the trail site resulting in the temporary closure of the trail to the public.

Engineering Solutions

Because of the early identification of these sites, the City of Frisco has already begun the process of alerting the stakeholders of the erosion-related concerns for these areas. The City selected Walter P Moore to design the repair the storm damage. A significant rehabilitation project was started in May 2021—approximately one year after the storm event that closed the trail. The trail site was repaired with an anchored gabion retaining wall and with the slope from the trail to the wall protected with a turf reinforcement mat.

The sanitary sewer was relocated from where the manhole was exposed by the stream in order to allow the manhole to be placed in a more stable location. The turf reinforcement mat was also utilized on the repaired bank to create a natural appearing solution in the park.

The project also placed grade control structures throughout the stream reach to aid in future stream stability and to minimize future channel downcutting. These grade control structures were incorporated into the project along with the main channel improvements. This very unusual method of structural toe protection allowed for less disturbance of the natural channel bottom while lowering installation costs versus traditional methods.

Other sites not originally in the scope were also repaired in the project because of the study performed by Walter P Moore. By addressing these locations before they became emergency situations, less expensive, non-structural solutions were possible.

One site downstream of the trail site was experiencing slope instability which was causing bank loss that would eventually threaten the trail. The bank was protected utilizing a lower cost more natural appearing turf reinforcement mat instead of a concrete slope repair. The resulting repairs were environmentally friendly, locally resources, and more cost-effective than conventional approaches.

The knowledge and experience the Walter P Moore team brought to the project positioned the firm to assess and evaluate the geomorphological issues the site would face in the future. Additionally, the team designed the unique structures required to remediate the channel.