I am modeling a pedestrian trail underpass culvert that will be placed adjacent to an existing culvert. An upstream levee is proposed to keep the smaller flows from inundating the trail and culvert. The issue I’m having is that even though I have defined the levee up to the cross section at the upstream face of the culvert, the program is using the both the existing and proposed underpass culvert to pass flow for the smaller flows. How can I model the levee “through” the culvert system so that the proposed culvert is not used until the levee is overtopped?
If you start with an inline structure (you can still enter a culvert) or a lateral structure you could use the rules capability to set the max flow to zero until a certain water surface is reached.
If the culvert is flowing under inlet control you could model it as a rating curve.