Pond Surface SCS CN
Pond Surface SCS CN
(OP)
I'm currently working on a project with an area of 38 acres. The requirements are to reduce the discharge resulting from the 25, 50, and 100 year 24 hour storms by 25% after development. That's not my problem, just a little background.
The site is situated in a wetlands area. The local agencies recommend using the heavily wooded condition for predevelopment rates, which is fine. The developer would like the detention pond to be an 8 acre wet pond. What CN value should I use to model this pond post-development? Should I assume that all rainfall that falls over this 8 acres will runoff? The DOTD manual I am referencing does not provide any values for this condition.
The site is situated in a wetlands area. The local agencies recommend using the heavily wooded condition for predevelopment rates, which is fine. The developer would like the detention pond to be an 8 acre wet pond. What CN value should I use to model this pond post-development? Should I assume that all rainfall that falls over this 8 acres will runoff? The DOTD manual I am referencing does not provide any values for this condition.





RE: Pond Surface SCS CN
RE: Pond Surface SCS CN
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Pond Surface SCS CN
I would have to disagree with using a CN of 98, even though it wouldn't have any practical effect because the models aren't accurate to that extent.
Using a CN of 98 implies that some of the stormwater is being stored in the system. Pavement has cracks, grass can store quite a bit of water, but how can a water surface do anything but rise? The water falls directly on the surface, so there is no time of concentration and no losses.
RE: Pond Surface SCS CN
RE: Pond Surface SCS CN