J. S. TOEWS, S. P. CLARK 841
Figure 7. Comparison of predicted and measured relative depth for Manning’s Equation and Equation (3).
more accurate means of estimating minimum flow depths
for fish passage at low discharge. At these very shallow
flows the resistance from the corrugations seem to act as
form drag, rather than merely a uniform skin friction.
The difficulty with Equation (3) is that its accuracy has
not been verified over a significant range of corrugation
heights and culvert diameters. The advantage of using
this equation is that a varying roughness coefficient does
not need to be developed. It also has been shown to be
accurate up to the mid-depth of the culvert, which corres-
ponds to the upper depth limit in the Manitoba Stream
Crossing Guidelines for culverts. Some recommended
future works include testing other corrugation sizes at
similar slopes to determine the variation of Manning’s n
for different CMP culvert types. This would also allow
for a better determination of the relative depths reliance
on the relative roughness.
The authors wish to thank the NSERC, Manitoba Hydro,
Manitoba Infrastructure and Transportation, and the Cor-
rugated Steel Pipe Institute of Canada for their support.
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