Modified Rataional for Pond Sizing: Outflow Calculations

[Dredger01]

I've been trying to understand the Modified Rational Method for pond sizing. One thing that is confusing me is calculating the outflow volume. In particular, the calculation calls for 1/2 of the inflow duration x control release discharge x 60 s/min.

Does anyone understand why one half is used as a multiplication factor on that?

 

[psmart]

My guess would be that the 1/2 is used when calculating the volume of a presumed triangular hydrograph with a given duration and peak.


Peter Smart
HydroCAD Software

http://www.hydrocad.net