Modeling a small bridge

[spn4125]

I am trying to model a small 16' bridge and need some input. The bridge is being replaced with several large culverts and I need to prove the replacement is hydraulically in-kind. This area routinely over tops the roadway so I can't model it as open channel flow as it quickly show signs of flowing full. I tried to model the upstream cross section as a custom weir but then I cannot model the over topping of the road. My initial thought was to have a custom weir as primary, and a broad crested weir as secondary for the roadway. Is there a way to have a custom weir with a top? This body of water is also tidal so I will need to input a tailwater elevation. Any help would be appreciated.

 

[TerryScan]

Probably best to model as a pond with a box culvert Primary outlet and weir Secondary outlet for overtopping. There are Custom and asymmetrical weirs available.