which route would be most conservative approach? I would use the overland flow thru the swale with the grass cover, not the underdrain pipe.

Thank you for the suggestion. I was also trying to model the dry swale using "Pond", but my swale as a 4% longitudinal gradient and I can't find any outlet device that can describe it.

Thanks again,
Serene

Sounds like a segment of channel flow.

Peter Smart
HydroCAD Software
www.hydrocad.net

Hello Peter,

Do you mean the Tc line? Would the shallow concentrated flow work as well?

Yes, I was referring to a Tc segment for channel flow. For very small depths you could use shallow concentrated flow. Or try both and compare the results.

Peter Smart
HydroCAD Software
www.hydrocad.net

Thanks Peter, I'll try both. What about the to model the dry swale using "Pond"? I'm using a pond storage with outlet "exfiltration" and "broad-crested weir", what should be the conductivity in the "exfiltration"? The current model is giving me very small exfiltration at the 100-year storm event I gave a very large conductivity (a random number). I also attached the HydroCAD file here. Please let me know if you have any questions.

• https://files.engineering.com/getfile.aspx?folder=148dc220-6e87-4dc8-92bc-3

If you have free flow through the swale then you should model it as a reach or a Tc segment of channel flow. A pond node would apply only is you have level pool storage controlled by one or more outlet devices.

If you don't know the conductivity value I suggest you specify a constant velocity instead. Click help on the exfiltration screen for details.

Peter Smart
HydroCAD Software
www.hydrocad.net

Got it. Thank you, Peter!