HY-8 multiple culverts

[TerryScan]

I was wondering if anyone might have an explanation for varying HY-8 results depending on how one models multiple culverts (I am using the latest release v7.1).

I am simply modeling 2 identical parrallel culverts. One option is to set the "Number of Barrels" in the culvert properties to 2.

At one point I wished to check some alternatives with varying the inverts of the second culvert. So I took the second approach of having 2 culvert definitions for the one crossing. Using this approach, setting all properties identical for both culverts yeilds a different headwater for the same flows than using a single culvert definition with 2 barrels.

I have attached the file in question for those interested.

Any ideas?

 

[cvg]

according to my computer, headwater is the same - 20.63 for 158 cfs design flow on both crossings. I can't see a difference.

 

[TerryScan]

Thanks CVG, I opened the file again here and get 21.60 for both. I swear it was not the case the day I sent this. Although, I would be unlikely to believe it if someone else was stating the same.

I was abount to post this, then tried one more thing. When I opened the file from HY-8, the headwaters agree. When I launch HY-8 by double clicking the data file in Windows Explorer, I get 21.60 for the doubld barrel, but get 21.10 with the two culvert definitions. It seems something does not get initialized when launching from Explorer.

 

[youngEIT]

yep, its the same for me as well! anyway, good that you have it figured out now..