Sorry, this is not a question about modeling. Right now I am looking for the hardware. The modeling questions will probably come later.

I am looking for comments on experiences with large tide (flap) gates on culverts. We are designing a replacement tide gate structure at the mouth of a drainage canal; the purpose is to keep the tide from filling all the available flood storage during high tide. The existing structure has had numerous maintenance problems, including corrosion of the cast iron flap gates from the brackish water, and debris clogging in the outlets preventing the flaps from closing properly. Additionally, the flaps are so heavy that there is a significant head required to push the flaps open. The head differential results in higher velocities through the openings and scour holes. The pipes will be fairly large, roughly 2 meters + or -.

We will be fitting the upstream side of the structure with sluice gates so that an emergency full closure may be made in case of a fuel spill upstream along the canal, and the downstream side of the structure will have the flap gates.

In addition to the cast iron flap gates, I have seen some heavy wooden gates on other structures that didn't seem to work very well either. It seems to me that a flap made of some plastic composite material would be corrosion resistant and also be easier to open and thus less obstructive to flow, but I have been unable to locate any manufacturers. Also, are there any designs that are less susceptible to debris clogging? I have seen flaps on mitred-end pipes that seemed to close more securely, but I have not seen any this large. I have received one recommendation thus far for a twin-linkage hinge that is supposed to work better on large sizes of flap valves and one suggestion to investigate a rubber choke-type valve.

I have posted this only to the SWMM-users at U. of Guelph and the Hydrology group at Monash Univ. If anyone is a member of another group that might be more appropriate for this question, please forward it for me. You can reply directly to me at the following e-mail address:

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joseph.t.hoke@sas02.usace.army.mil

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Any suggestions or names of manufacturers would be welcome.