Weighted Q Output

[LincolnPE]

I am using the Weighted Q method and I am getting confusing output that states the entire site is 100% pervious.

Please see the attached file.

 

[psmart]

CN values less than 98 are reported as "pervious".

Pleas note: When using the weighted-Q option, the pervious/impervious percentages have no effect on the runoff calculations. They are calculated strictly for informational purposes. The runoff is calculated separately for each CN, regardless of the CN value. If you wish, you can disable the pervious/impervious reporting on the Advanced tab of the Settings | Calculation screen.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[LincolnPE]

If I do that it displays a weighted average CN, that is not to be used with the Weighted Q method. Please see attachment.

 

[psmart]

The weighted CN is still displayed for informational purposes, but the value is not used in the weighted-Q calculations.


Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[LincolnPE]

Why do that? This will be wildly confusing to the reviewer and everyone else...


It would be helpful to have the correct information summarized in the report. I would like to see this done as it is done in the NEH. Please see attachment.

 

[psmart]

The weighted CN is displayed in many HydroCAD reports, and removing it would be problematic. Even though the value is not used in the weighted CN calculations, it's still a convenient way to summarize the subcatchment. Yes, the breakdown you suggest would be a nice enhancement for the subcatchment report, but it wouldn't fit in the many other places where the weighted CN is reported. We can consider an option to suppress the weighted CN, but it's not as trivial as you might think.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[psmart]

Sorry, that should have been "not used in the weighted-Q calculations"

Peter Smart
HydroCAD Software

http://www.hydrocad.net