The purpose of this study was to determine what hydraulic characteristics enhance or diminish upstream juvenile salmon passage within a sloped-weir baffled culvert. The culvert slope, baffle spacing, and baffle height were varied to observe flow regime trends that describe conditions suitable for fish passage. Biological testing was conducted in conjunction with the hydraulic micro-Acoustic Doppler Velocimeter (ADV) measurements. There was considerable spatial variability in the flow created by the sloped baffles within the culvert. The asymmetry of flow (As) decreased for increasing discharge, larger baffle spacing and smaller baffle heights. To describe the flow features essential to fish passage, the interrelation between flow asymmetry, depth, and velocity were presented in comparison biological testing. For the range of parameters tested, flows were described by a series of three jet regimes which were a function of water depth over baffles. Comparing these regimes to the biological study revealed peak juvenile salmon passage was associated with a critical transition between jet regimes. Generalizing this transition for the entire data set using dimensionless scales provides professionals with guidance for retrofitting culverts.
Washington State Transportation Center (TRAC)
Hydrodynamics, Culverts, Salmon, Animal migration, Retrofitting, Flow measurement, Velocity measurement, Experiments, Weirs, Critical flow, Depth, Fish ladders, Endangered species, Velocimeters.