Hydrographs
Hydrographs
(OP)
Why do hydrographs show no flow in or out of my pond for so many hours, then suddenly jump up? This doesn't seem logical to me. Shouldn't flow start almost right away?

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RE: Hydrographs
From the web site:
Why don't I get any runoff until about 10 hours?
According to the SCS runoff equation, there will be no runoff until the rainfall exceeds the initial abstraction, which may not happen until 8-10 hours into the storm. Until that point, the runoff will be zero. This effect is most pronounced for low CN values and low rainfall depths, such as water quality events. For example, a CN value of 80 has an initial abstraction of 1/2 inch, which isn't satisfied until 11.2 hours for a 2-inch 24-hour Type II storm, and significant runoff does not occur until about 11.7 hours.
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Hydrographs
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Hydrographs
My coworker thinks this doesn't make sense, and I have a setting "off".
The CN of my drainage area is 83, and I have a pond with a 24" outlet through a control structure with a low-flow orifice and weir.
RE: Hydrographs
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Hydrographs