Using three dimensional hydrodynamic modeling and fish swimming energetics to assess culverts as potential physical barriers to upstream fish movement




Montana State University. Bozeman, MT


swimming, energetics, culverts, physical barriers, barriers, upstream, fish passage, design, streams, water velocity, water depth, fish movement, computational fluid dynamics


Fish passage through culverts is an important consideration in road and streamcrossing design. Although no comprehensive inventory of culverts on fish-bearing streams in theUnited States is available, there are an estimated 1.4 million stream–road crossings. The mostcommon physical characteristics that create barriers to upstream fish passage include excessivewater velocity, insufficient water depth and large outlet drop heights. Over the past decade,interest in the effect of culvert barriers on aquatic systems has grown; accordingly, variouspassage assessment techniques have been used to determine whether a structure is a barrierand under what flow conditions. Recent research has shown that determining the barrier status ofa culvert is not trivial, and that different methods are often not congruent in their classification ofbarriers.The purpose of this research was to test the use of 3-D hydrodynamic modeling to assesspotential culvert barriers to upstream fish movement. The approach quantified the 3-D velocityfield within the culvert barrel using computational fluid dynamics. A range of potential pathsthrough the culvert were identified using an algorithm that estimates energy paths, and passagealong the paths was assessed by combining the swim speed–fatigue time relationship with the 3-D velocity field. Results from the 3-D approach were compared to an approach that used the 1-Dvelocity field to estimate passability. Comparisons between estimated passage and measuredpassage showed the 3-D method more accurately predicted passage through the culvertcompared to the 1-D method.

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