Irwin Creek on I-77

Typically, when we think of stream restoration projects, we are thinking about habitat protection and aesthetics. However, some projects have higher stakes involved. That’s exactly the case with the Irwin Creek portion of the Interstate 77 project in Charlotte, North Carolina.

About Irwin Creek

Irwin Creek is a major drainage-way for the City of Charlotte and runs alongside highly-trafficked I-77. With a watershed of about 3.4 square miles, the stream has experienced bank instability and erosion over time. This combination of issues threatens private and public property and causes public safety concerns.

Not a Typical Stream Restoration

Although our team has been working on the I-77 project for three years, we recently started on a stream restoration portion of the project that does not allow for natural channel design we would typically use. This section’s extremely narrow corridor and proximity to Irwin Creek leaves very limited space for stream restoration construction. 

There are several different systems for stream restoration design. How we choose the appropriate design depends on:

  • the size of the stream channel, 
  • the confines of the space, 
  • the velocity of the water in normal flows and in storm events, 
  • the type of soil/stone/materials available on site, and 
  • the habitat that depends on the ecology of the system. 

In order to stabilize the 2:1 stream banks within this narrow corridor, CEC was tasked with rock plating the banks, in lieu of performing a more typical natural channel design, and its corresponding sider flood plains. 

“Rock plating was the go-to method for stabilizing the banks of Irwin Creek,” said CEC founder and president Joanne Cheatham. “This method requires grading the slopes and then applying geotextile to the graded slope, followed by the application of Class 1 riprap to a depth of two-feet. This large rock will interlock and preserve the integrity of the slope during high-water rain events.” 

Goals for this Charlotte Stream Restoration

Many sections of existing Charlotte-area interstates have flooding concerns during heavy rains, and the goal of this project’s scope is to avoid that very dangerous situation. In addition, this type of stabilization will not require the large floodplains of the natural channel design to dissipate the energy of the high flow waters. This is not the aesthetic norm we expect for stream restoration, but it certainly does the job to move the water through a busy urban area during high water events while protecting the corridor from degradation. 

“It does a fine job of moving water through a busy urban area during heavy rain and flood events while protecting the stream corridor from degradation,” she added.

CEC is on track to complete this project this summer. Given the tight timetable and challenging project restrictions, communication between equipment operators is key to keeping everyone safe and the project on time. The bottom line? CEC thrives between a rock and hard place.