Nicholas Kehler

Anthropogenic barriers to fish passage at stream crossings are an important issue in North America. Environmental regulations impose velocity restrictions on culvert flow, which may be overly simplistic. A series of laboratory experiments were conducted in a corrugated metal pipe culvert at three mild slopes. Acoustic Doppler velocimeters were used to measure velocity and turbulence quantities. A significant percentage of the cross-sectional flow area was found to have a streamwise velocity lower than the mean bulk velocity. Secondary currents were measured and are believed to contribute to the strong velocity dip at the water surface and the non-uniform shape of the boundary shear stress distribution. A modified version of the log law is proposed to estimate water velocities within the fully-developed flow region. Results may be of interest to hydraulic engineers and regulators involved with fish passage issues at stream crossings as also for calibration and verification of numerical culvert models.