To Restore Streams On The Cheap, Franklin County Mimics Beaver Dams | WOSU Radio

To Restore Streams On The Cheap, Franklin County Mimics Beaver Dams

Dec 9, 2019

Rows of nearly identical houses run along gently meandering roads in Jefferson Township’s Willow Brook subdivision. It’s suburban, but tucked in here is a pretty innovative environmental project.

Dave Router is decked out in waders, standing in a stream up above his knees to show one off.

“Our first ones have been in for seven years, and we’re just seeing some erosion on this top layer and that is surprising to us actually how well that’s held up,” Router says with a bark of a laugh. “You know all we need to do is come back in and put a new layer on top.”

Franklin County environmental officials have come up with a way to improve the health of streams for a fraction of what other approaches cost. These stream inserts mimic beaver dams to create pools where wildlife can flourish and help control erosion on riverbanks.

Router is Franklin County Soil and Water’s Urban Conservationist, which means he spends a lot of time working in places like this, where human development intersects with the natural environment. The inserts are a series of filters—think really thick Brillo pads—stacked one on top of the other.

The structure runs the width of the stream, and it’s held in place with stakes and anchors. Router says the idea was sort of a happy accident.

“It was it was really a eureka moment when we looked at some of those other stream channels and saw the aggradation that was occurring,” Router says. “[We were] like, this is really a fast process, and we could probably use that to good advantage.”

Franklin County has been installing these fake beaver dams to help improve stream health.
Credit Nick Evans / WOSU

The material is primarily used for floating islands meant to draw nutrients out of water, but officials noticed when people used the filters for home sewage runoff, sediment piled up quickly.  

That’s exactly what they’re trying to encourage in many stream restoration projects. Kyle Wilson, the county’s conservation program manager, explains how it works.  

“Very quickly, rock starts to aggregate behind it,” Wilson says. “You start to get plant growth on the actual material, and so a month later you could walk this stream and if you weren’t looking for these inserts, you wouldn’t even notice that they were there.”

It also lets them influence what’s known as the thalweg. “It’s the deeper flow section of the channel, is the easiest way to describe it,” Wilson says.

The German term, commonly used in geography, refers to the lowest point of elevation in a river.

“You can kind of see it on this little insert here where that babbling part is,” Router explains. “We’ve got the thalweg directed more away from that far bank so it’s aiming more towards the downstream open channel and keeping the erosion off of there.”

By lightly damming the stream here, they create pools, which provide habitat for aquatic species. It also gives the stream access to the floodplain during heavy flows—helping filter out sediment, creating wetlands and avoiding worse flooding downstream.

Standing in a stream in Jefferson Township, where Franklin County is trying an innovative method of stream restoration.
Credit Nick Evans / WOSU

Aside from blending in with the environment, Wilson says there’s another serious benefit: It’s really, really cheap.

“Stream restoration can be very expensive,” he says. “You get equipment out here, earth moving costs, cost of material such as rock and other things. This is an approach that we want to do on that scale of maybe $10,000 or less these projects could be done.”

Wilson explains the material they use for the dams comes in big rolled up sheets. All they need is a small circular saw to cut it and some hardware to anchor it.

This entire project comes in at around $10,000. That covers about 20 of these dams strung along half a mile of the stream, as well as removal of invasive species and planting trees near the banks. Funding for the project came from a federal grant through the EPA.

The approach is still in the demonstration phase, but Router says they’ve seen positive signs in the limited ecological sampling they’ve done.