You are currently reviewing an older revision of this page.
What do all the lines in PondMaker step 4 represent?
The blue line represents your outflow from your currently defined outlet structure.
The orange line represents the target rating curve you are trying to meet.
The dashed lines are the estimated maximum water sruface elevation for each storm event that you have defined.
In this step of PondMaker the object is to define your outlet structure in such a way so the outflow meets your target rating curve as closely as possible. If your outflow curve is above your target rating curve you have essentially overdesigned your outlet structure and have restricted your flow too much. On the other hand, if your outflow curve is below the target rating curve your outlet structure is underdesigned the structure and may not have restricted the flow enough.
In the best case you would like to meet your target rating curve exactly, but this is not always possible. For many designs as long as you are within a certain tolerance your design will considered sufficient. You should check with your local governing agency on the policy for your town, city, or state.
Below is a simple example of an outlet structure that is slightly overdesigned for the 10 year event and just slightly underdesigned for the 100 year event, but meets the acceptable tolerance design for this project of 10% above/below.