HydroCAD - Detention Basin Model
HydroCAD - Detention Basin Model
(OP)
We are working on a project with a wet basin and a detention basin. They are not connected and are at different design points.
With the wet pond model, I have the permanent pool area as impervious area. If the detention basin drains dry, do I model the bottom area of the basin also as impervious?
With the wet pond model, I have the permanent pool area as impervious area. If the detention basin drains dry, do I model the bottom area of the basin also as impervious?





RE: HydroCAD - Detention Basin Model
RE: HydroCAD - Detention Basin Model
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: HydroCAD - Detention Basin Model
forum789: HydroCAD Stormwater Modeling
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: HydroCAD - Detention Basin Model
If I am understanding the question correctly, this is really a question of CN value and is not Hydrocad specific.
I understand you saying that you have a wet pond and a "dry" pond within the same watershed. You already plan to model the wet pond as an impervious surface and are unsure how to model the dry pond.
In dry weather, it is possible for the "dry" pond to drain completely. However, when you are running a hydrologic model, it isn't exactly dry weather is it? I think it would be safest to assume the basin is impervious even if you may be discounting some soil storage capacity at the beginning of the event (prior to runoff).
If you are actually modeling the "dry" basin as infiltration, it should stil be modeled as impervious in runoff calculations, since you don't want to "double count" the soil storage in the runoff componant and the routing component of modeling.
RE: HydroCAD - Detention Basin Model
Yes..I guess my question was more of a CN value question.
We are not taking credit for infiltration, as the dry basin is for attenuation of peak flows only. I will treat the dry basin bottom as impervious for my model.