by Lisa Cutshaw, PLA, ASLA
Stream restoration has become a necessary and timely tool in the effort to combat environmental issues like flooding and erosion, especially as they are accelerated by more frequent storm events associated with climate change. The author, Lisa Cutshaw, is the Principal Landscape Architect for Summit Design and Engineering and collaborates with colleagues to understand and implement emerging best practices to promote a more resilient approach to the built environment.
Is it ever a good idea to pour concrete in a stream bed? What about riprap and other common erosion control measures? To dig into the specifics, we spoke with Paxton Ramsdell of Ecosystem Planning and Restoration (EPR) in Raleigh, NC. Paxton has many years of experience with stream restoration, recently with Environmental Defense Fund and now with EPR.
Engineered solutions have fallen out of favor in recent years among sustainability advocates, but back in the day, it was common to create concrete channels to try to control streams. The idea was this would stop erosion and direct the water where people wanted it to go. The design professions learned the hard way that channelization actually compounded erosion and flooding problems, but riprap, etc., are still commonly used.
What are the biggest pros to using vegetated solutions rather than engineered solutions?
To be clear, a vegetated solution essentially means restoring the stream with a functional flood plain, allowing the plant root systems to stabilize the soil while also allowing the stream to overflow onto the flood plain when the water rises after rainfall. Research has found that in addition to soil stabilization, vegetated solutions have other benefits, such as slowing down runoff, reducing particulates and excess nutrients in the water, moderating stream temperature, and promoting groundwater recharge.
Paxton Ramsdell: “Vegetated stream restoration projects can reduce erosion and flooding problems, and they tend to last longer than engineered solutions. When streams are able to flood naturally onto the flood plain along the length of the stream, the severity of flooding downstream is reduced, and the stream bed itself has less scour to contend with. When they are properly designed and protected from encroachment, vegetated stream restoration projects should last for generations.”