modeling riser pipe

[hunter82]

I am attempting to model a riser pipe in Hec-Hms. I know that at the beginning stages of the pipe flowing, it functions like a weir, with the circumferece of the pipe equal to the length of the weir, but as the water level increases the riser pipe begins to flow full and it is modeled like an orifice.
My question is can this be modeled in hec-hms or do I need to find another program to perform the combination modeling.