Culvert Technology May Help Young Salmon Muscle Their Way Upstream

Tens of thousands of culverts lie beneath roads in the Pacific Northwest, successfully moving water under the roadbed to preserve the road and prevent flooding. At the same time, many of these same culverts are blocking juvenile salmon from migrating upstream to their habitat where they need to survive and grow.

Pacific Northwest National Laboratory (PNNL), under operation by Battelle, participates in a consortium led by the Washington State Department of Transportation (WSDOT), which includes transportation departments from other West Coast states, including Alaska. The consortium funds a program to find viable retrofits for the culverts in the Pacific Northwest that may be preventing juvenile salmon from completing their life cycles.

The culvert testbed program promises not only to evaluate current and future retrofits, but to do so in a comprehensive way. “This project is a true interdisciplinary project because we’re blending the expertise of hydraulics engineers, mechanical engineers, statisticians, fish biologists and fish behavior specialists to find a solution to a problem that faces the entire Northwest and has implications for culverts throughout the country,” said Dr. Walter “We’re doing this in a systematic, scientific way, using well-designed experiments in a wellengineered facility.”

Located at the Washington Department of Fish and Wildlife Skookumchuck Hatchery near Tenino, Washington, the culvert testbed is a physical device, into which scientists can place an active culvert. By changing the culvert’s water flow and slope settings, scientists can measure hydraulic conditions, or how water flow interacts with the culvert system, influencing water velocity or creating turbulence. These scientists will also conduct trials with juvenile fish to determine how well fish pass through various retrofit designs.

This new testbed program will enable scientists to set the hydraulics and observe fish behavior and then adjust the hydraulics and observe changes in fish behavior. “There are hundreds of possibilities for bed configurations. A particular design will stop passing fish at some flow or some slope and that’s what we’ll be looking for,” Dr. Pearson stated.

Installation of the testbed is almost complete and researchers will soon begin testing the mechanics of the device. WSDOT, and its consortium, funds PNNL through the U.S. Department of Energy for the purpose of conducting the culvert testbed program and evaluating its retrofit efforts.

For more information, please contact Dr. Walter Pearson at (360) 681-3661, walter.pearson@pnl.gov.