Road Ecology Center

The Washington State Department of Transportation (WSDOT) has identified the need to evaluate all aspects of Department programs that may affect Pacific salmon and their habitats under the Endangered Species Act, and to correct situations where adverse effects exist. The great deal of research and engineering conducted to date has resulted in enhanced passage of returning adult salmon. However, the movement of juvenile salmonid both up and downstream throughout the year is now recognized as substantial, and the need for them to pass this life stage has made the problem even larger in scope. Tens of thousands of culverts exist in the state of Washington alone, and many are judged as blocking juvenile salmonids from thousands of miles of habitat. Determining appropriate hydraulic and fish passage designs for new and retrofitted culverts before installation has both substantial cost and environmental implications. The optimal conditions for culvert passage by juvenile salmonids are not well understood, and thus are a key area upon which WSDOT has decided to focus its research efforts.

In partnership with WSDOT, the Pacific Northwest National Laboratory has undertaken a phased program to address the hydraulic and behavioral issues associated with juvenile salmonid fish passage through culvert systems. This program addresses the testing and assessment of culvert designs, along with associated measurements of hydraulic conditions and fish behavior occurring in full-scale physical models of culvert systems deployed in an experimental test bed. Experiments in the testing apparatus will measure the hydraulic conditions (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 long-term intent is to develop the test bed into a regional and national-level capability that can be used by other agencies that need to develop appropriate culvert designs to enhance the passage juvenile fish.