Weir? or Obstruction?

[burnen2]

What should I do? I have three openings under a bridge. Two of which are controlled by a weir or obstruction. The flows then re-combine on the downstream of the bridge. I even thought about a gated opening but once its open, there would be no more weir. Any suggestions?

[MattZ]

It is tough to answer this question without a diagram of the bridge. It sounds like a good alternative to this problem would be to create a split with three separate river reaches so that HEC-RAS can calculate a separate water surface profile through each opening. You can see an example of this in the Hydraulic Reference Manual on page 7-7 and 7-8.

Another option may be to use the Multiple Opening analysis contained within the Bridge/Culvert Editor screen. Or you may want to set up separate plans to run both of these options and compare your results. I hope that helps you out.