THE INNOVATORS
Improving Fish Passage With the Flexi Baffle
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fforts to improve fish passage in ecosystems like the Yakima River basin typically focus on large dams that block fish in a particularly obvious way. However, thousands of culverts in the small tributaries that feed a river system can block salmon and other fish from their spawning grounds, too. One solution for this problem is the Flexi Baffle, a New Zealand–developed product that allows fish to pass through culverts without reducing the capacity of the culvert. In North America, the Flexi Baffle is supplied by S. Scott & Associates, LLC, a natural resource consulting firm. In this interview, Shane Scott, the owner of S. Scott & Associates, speaks with Irrigation Leader Editor-in-Chief Kris Polly about the advantages of the Flexi Baffle. Kris Polly: Please tell us about your background. Shane Scott: After college, I worked for a small engineering consulting firm in Port Orchard, Washington, that designed fish hatcheries and fish passage systems and conducted natural resource assessments. When I started working at Tacoma Power in 1994, I worked on utility-related natural resource issues, Federal Energy Regulatory Commission relicensing, and supporting the engineering staff. I also did a short stint at the Washington Department of Fish and Wildlife, where I worked in the director’s office, addressing Columbia River hydro policy issues. In 2003, I moved the family down to Vancouver, Washington, where I worked in a similar capacity for the Public Power Council, which is an association of public utilities that purchase power from the Bonneville Power Administration. In 2006, I started my own natural resource consulting business, S. Scott & Associates. I still work on an advisory basis with the Public Power Council and consult on other natural resource issues for utilities, irrigators, municipal water groups, and other water users. Our work has expanded into marketing, sales, and manufacturing in the last few years. Kris Polly: Please explain the significance of fish passage in culverts in Washington State.
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a bridge. However, that is often an expensive fix that requires engineering, construction, and permitting, and it takes a couple of years even on a good timeline. There’s just not enough time and money to replace all of them. Kris Polly: What is the engineering solution to that problem? Shane Scott: I met a manufacturer in New Zealand who developed a flexible weir that can be installed in a culvert to modify its hydrology to improve fish passage by creating a fish ladder inside the culvert. The flexibility of the weir is important. In the past, solid weirs were installed or retrofitted in culverts and bedrock, sticks, and logs would get caught in these weirs, blocking fish passage and maybe even blocking the water altogether and causing flooding. The Flexi Baffle, on the other hand, is made of a flexible polymer material that folds over in high water and allows water and debris to pass through. When the flow drops, the Flexi Baffle pops back up and forms the pools that create a fish ladder through the culvert. The Flexi Baffle preserves the hydraulic capacity of the culvert and improves habitat connectivity in a watershed, not only for fish but for other aquatic creatures such as amphibians, crustaceans, and insects. It is made of nontoxic materials and doesn’t create any environmentally harmful microplastic byproducts. Kris Polly: How is the Flexi Baffle physically connected to the culvert? Shane Scott: There are a couple of different ways to connect the Flexi Baffle to the culvert, depending on its composition. If you have a concrete culvert, you use a sleeve screw to attach
PHOTOS COURTESY OF S. SCOTT AND ASSOCIATES.
Shane Scott: A recent Supreme Court case requires the State of Washington to protect salmon habitat. Part of that involves improving fish passage at barriers, including road culverts. Habitat surveys found that there are over 7,000 culverts in Washington State that could present at least a partial barrier to fish passage. Similar surveys all over North America have identified tens of thousands of similar fish passage barriers. Culverts are typically sized to pass water under roads or driveways. Not a lot of thought is put into their role in fish passage. During high water events, the water velocity through culverts is often so high that it blocks fish from swimming upstream. During low water, there’s not enough water in the culvert for fish to swim upstream. The best way to fix the culvert is to replace it with another adequately sized culvert or
Water flows over a series of Flexi Baffles inside a culvert, creating a viable passage for fish.
