When trying to compute a model, the following user notification is generated:IDF data is not support by SWMM. Storm event is excluded from export.
This is a warning message providing information about what to expect when the model is exported to EPA SWMM. EPA SWMM 5 does not support the Modified Rational Method, so if the model were to be exported the SWMM 5 format, the hydrograph data would not be valid. If exporting to EPA SWMM 5, you will need to select a different global storm event before the export is done.
However, if you are using the Modified Rational Method in SewerGEMS or CivilStorm, the results will be valid. The Explicit (SWMM) solver in SewerGEMS and CivilStorm completely supports the Modified Rational Method.
When computing model in SewerGEMS or CivilStorm with Explicit solver and if this user notification is generated then this is an informational notification, to let you know that the IDF storm data was not included in the SWMM INP file that gets created during the process of computing with the SWMM solver. When you compute, it first exports the model to an INP file (the native format of EPA-SWMM), then loads that into the EPA-SWMM solver. Because EPA-SWMM itself does not support IDF storm data, this message informs you that the storm data will not be available in that INP file.
This should not be a problem unless you are attempting to open that INP file (which will be saved alongside the other SewerGEMS model file) in EPA-SWMM, because the actual catchment runoff calculations are performed separately and independently from the SWMM hydraulics. A separate solver first calculates the runoff hydrographs (in this case based on your IDF data), and then injects those hydrographs into the nodes for the SWMM solver to route through the network.
SWMM export problem: You cannot add or change a record because a related record is required in table hmisupportelement