How to model a bridge in SWMM

[sshao]

If I have a natural channel and a bridge with some piers, how do I model the bridge in SWMM. I saw people handled it in different ways. Some treat it as a user-define conduit for the section under the deck combined with a weir to simulate the flow over the road. Some people model it with specifying a maximum depth of the natural channel for the for the section under the deck. Other people think it can be treated as a storage node in SWMM and use a rating curve developed from Hec-ras. Which one is the conventional way to model a bridge?