Road Ecology Center

The passage of juvenile salmonids and other fish through culverts is a significant Endangered Species Act (ESA) issue throughout the Pacific Northwest and now in other areas of the nation. Much of recent research and engineering has focused on increased passage of returning adult salmon; however, juvenile-salmonid movement both up and downstream throughout the year is now recognized as substantial and is a key area in which future research promises practical returns. Because a large percentage of the culverts beneath roads in the Pacific Northwest are judged as blocking juvenile salmon from thousands of miles of habitat, determining appropriate hydraulic and fish-passage designs for retrofitted culverts before installation has both substantial cost and environmental implications. To address these issues, the Washington State Department of Transportation (WSDOT) leads a partnership that includes the Washington Department of Fish and Wildlife (WDFW), Alaska Department of Transportation, Alaska Department of Fish and Game, Oregon Department of Transportation, California Department of Transportation, the Federal Highway Administration, and the Pacific Northwest National Laboratory (PNNL). The partnership has undertaken a phased program conducted by an interdisciplinary team of scientists and engineers from PNNL to address the hydraulic and behavioral issues associated with juvenile-salmonid fish passage through culvert systems. This program addresses the testing and assessment of full-scale physical models of culvert systems deployed in an experimental test bed. Experiments in the test bed have begun and will measure the hydraulic conditions (mean velocity, turbulence, and water depth) associated with various culvert designs under various slopes and flow regimes, and then relate these measures to repeatable, quantitative measures of fish-passage success. The culvert test-bed program is a one-of-a-kind capability designed to provide scientifically sound information that can be used to develop better designs for retrofitted culvert installations. Compared with field studies or temporary installations, the facility promises fast results, scientific and statistically controlled evaluations, an ability to quickly discern optimum engineering principles, and elimination of expensive trial-and-error approaches of field installations.