Calibration Techniques

[jeffc]

I am building a SWMM model and I want to calibrate it. I was wondering what ways there is to calibrate it. Do I just pick and choose parameters and hope for the best or is there a statistical way to do it. Is there a program?

I know that PCSWMM includes an automatic calibration algorithm, however, I am a student and cannot afford to buy PCSWMM.

Along the same lines, I have a couple of questions,

What is a good width for roofs? From calibration attempts it seems that really small widths are the best.

Is there a way to have a maximum peak flow? I know that roof drains (catch basins as well) have a maximum flow.

Thanks
Jeff

[swmmguy]

as a start point, you can estimate your width as sqrt(area).
you need adjust this value when calibrating your model.