Culvert Placed Flat (ɘ.5%) Assumptions
Juvenile fish need 2 feet/second or less velocity to pass upstream (ODFW, 1996)
Because of low roughness, bare culverts at almost any slope exceed 2 ft/sec on average and the little area of the culvert cross-section with low water velocity. (Belke et al.,. 1990)
Washington DFW study shows passage problems for Juvenile coho salmon at experimental culvert slopes of 0.5% and above (Powers et al. 1997).