Weir Submergence in 2D model

[Anonymous]

I am currently using an internal connection within a 2D flow area to model to overtopping of a weir into a spillway channel (and develop a spillway rating curve). Using the model, I have been able to develop a rating curve that closely follows the weir equation, although it does not seem to be accounting for submergence once tailwater elevations are high.

My question is, are internal connections effective at capturing the effects of submergence? Would I be better off using a lateral structure to represent the weir, where the structure connects a 2D (upstream) flow area to a 1D (downstream) spillway?

[Anonymous]

Assuming you are using the weir equation (and not the 2D domain), I believe the weir computations are the same and take into account submergence. I’ve gotten similar results when converting a 1D reach with lateral structure to a 2D area with internal connection. Obviously there can be differences when you convert the 1D reach to a 2D area. Presumably the 2D will be more accurate.

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