Problem

How can the Modified Rational method be used in a case where separate predevelopment and postdevelopment information is not known? For example a case where you are not concerned with predevelopment peak flow and simply want PondPack to use the current or postdevelopment conditions to generate a runoff hydrograph.

Solution

For this situation, select "true" for "User Defined TD?", then enter the desired critical storm duration. Select "User Defined" for the "Outflow Criteria" and set the "target" to zero. This bypasses PondPack's iterative process of determining the critical storm duration, which would otherwise fail if the Pre and post information are the same.

See Also

Understanding the Modified Rational Method

Why must I enter the Tc, C and area twice for a modified rational catchment? 

What is the workflow for setting up pre and postdeveloped conditions for multiple return events?