I am an XP-SWMM user and am in the process of developing a major/minor drainage system for my model. I am uncertain as to how I can model the surcharged water exiting my manhole structures and entering my roadways.

The SWMM manual recommends using equivalent pipes for manholes. It goes further to suggest using orifices to simulate inflow constrictions.

To account for the head/friction losses, do I simply adjust my orifice discharge coefficient? The documentation is very slim in this area.

Furthermore, should the inflow of water from my streets and into my pipe network be modeled differently than the water surcharging from my pipe network and into the streets. ie. isn't node outflow modeled differently than inflow.

Has anyone set up this type of model that may have some insight?

Regards,
Jon Marshall