Once the final design is completed, the designer must review the design to assure that all the design criteria in Step 3 are still being met.

The intent of a check flood is to verify that the system will not experience problems for a frequency higher than the design AEP. Department policy is to use the 100-year frequency (1% AEP) as the check flood. This check is more than simply running the storm drain analysis with all the flow forced into the system; it is considering what will happen to excess flow which can't go into the inlets. Will it safely flow down the gutter to the outfall, or will it flow down a driveway and flood a structure? Are contingencies made for these possibilities? These are only a few of the circumstances which may be found on a project.