The IDF Table or Curve is intended to only work with the Rational Method Hydrology:

1. You make a Curve called Reserved
2. The X column is time in Minutes
3. The Y column is either Intensity in inches/hour or millimeters per hour
4. If you use the Modified Rational Method the IDF Curve is called from the Rainfall Type Dropdown menu under MRM Rainfall Type
5. The duration is entered in the MRM Duration row. The program will extract the intensity from the X, Y values of the Reserved IDF Curve Type.