Subject: Exit, Other and Entrance Loss Values in SWMM 5
The entrance, exit and other losses in SWMM 5 are computed at the upstream, downstream and midpoint of the sections of the link. However, if the normal flow equation is used for the link during a time step then these losses are zero as the flow in the link is based solely on the upstream area and upstream hydraulic radius of the link. If you add loss coefficients and the normal flow equation is used then you will not see any change in the flow as you modify the loss coefficients.
via Blogger http://www.swmm5.net/2013/08/exit-other-and-entrance-loss-values-in.html