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Modeling drainage subarea CN with split pervious and impervious areas in HydroCAD

Modeling drainage subarea CN with split pervious and impervious areas in HydroCAD

Modeling drainage subarea CN with split pervious and impervious areas in HydroCAD

I am computing peak runoff from a development site using HydroCAD. The New Jersey code has the following requirement

"In computing stormwater runoff from all design storms, the design engineer shall
consider the relative stormwater runoff rates and/or volumes of pervious and
impervious surfaces separately to accurately compute the rates and volume of
stormwater runoff from the site."

I see, there is an option in hydroCAD to do just that
settings -> calculations -> Advanced - > Calculated separate Pervious/Impervious runoff (SBUH weighting)

But it seems like this option is tied to Santa Barabara Unit Hydrograph

Can I use this option, even when I am using a Delmarva Hydrograph?

RE: Modeling drainage subarea CN with split pervious and impervious areas in HydroCAD

Yes. Although this option is required for proper evaluation of the SBUH runoff procedure, it can also be used with the SCS/NRCS method. For further details see www.hydrocad.net/impervious.htm

Note: SBUH = Santa Barbara Urban Hydrograph, not Unit Hydrograph. SBUH does not employ a UH at all.

Peter Smart
HydroCAD Software

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