Where is the default rainfall frequency defined in InRoads Storm & Sanitary?
Tools>Drainage Options>Area Tab
The Area tab allows you to set parameters to use when computing the peak runoff (flow rate) from drainage areas. You select the computation method and enter the required parameters, which vary depending on the method. Once these parameters are set, you can use the Drainage>Flows>Compute Flow command to compute the area and runoff of a selected shape (polygon).
Frequency displays a list of standard rainfall frequencies corresponding to the selected IDF file. This parameter applies to the IDF File method only.