| Product(s): | PondPack |
| Version(s): | CONNECT Edition, V8i |
| Area: | Layout and Data Input |
Why must I enter the Tc, C and area twice in the properties of a modified rational method catchment?
The "predevelopment Tc" and "Predevelopment C/Area" are for the predevelopment conditions, used to establish the target peak flow rate. The other Tc and C/Area fields are for the postdevelopment conditions. PondPack determines the critical storm duration based on the requires storage volume, using the target flow rate and a series of postdevelopment storm durations. See the help documentation and the link below for more information on how the modified rational hydrograph is constructed. PondPack assumes that the pond will be designed such that it will store the required storage volume with the peak pond outflow rate equal to the predevelopment target flow.
If you do not have predevelopment information and would like to force a specific critical duration (Td) to produce an outflow hydrograph, use the Custom TD option per the second link below.
Understanding the Modified Rational Method
Using modified rational method without predevelopment information