I am trying to model a combined surface and sub-surface drainage system and the main software I have to use is StormCAD. I know CivilStorm can model both of these systems simultaneously but I can't purchase this software at this time. What I am wanting to know is if I can achieve this in StormCAD.

Basically I have a model already created in StormCAD and when I view the HGL at various inlets it is way over the top of the grate of the inlets. Now I know b/c some downstream pipes lack sufficient capacity the HGL is back-calculated up the pipe system until it surges out of the far upstream inlets. What I am wanting to determine is how much water is coming out of these inlets. I already looked at the help menus for StormCAD and it says the HGL here is innaccurate so I can't depend on it for any calculations. What I have tried as a work around is to start with an EGL downstream and adding friction losses and assuming an HGL at the upstream top of grate elevation I can achieve a velocity and from that get the flow that should be in the pipe and subtract that from its capacity to get how much is coming out of the inlet. What I am worried about however is the value I am using for the headloss. I have tried to calculate my own headloss but I get nothing close to what StormCAD does and I am worried that if I use the value it report for the conduit I am analyzing, it will be based off a too small velocity.

Please help anyone. I know CivilStorm is the no-brainer solution to this but I can't afford to purchase this software at this time.

Thanks for any help.

Paul