Flooding at manholes in SewerCAD and inlets in StormCAD occurs whenever the elevation of water is above the structure rim elevation. When this occurs, the backwater analysis will continue by resetting the hydraulic grade to the structure rim elevation or ground elevation, whichever is higher. However, if a structure is defined with a bolted cover, the hydraulic grade is not reset to the rim elevation.

In actual flooding situations, flows may be diverted away from the junction structure and out of the system, or attenuated due to surcharged storage. In this program, even though the governing downstream boundary for the next conduit is artificially lowered to prevent the propagation of an incorrect backwater, the peak discharges at the structure are conserved and are not reduced by the occurrence of flooding at a junction.