To Add and Modify Intensity-Data-Frequency (IDF) Rainfall Sets

Add variable IDF Rainfall data to test and analyze a drainage system. IDF data defines the relationship between rainfall intensity (or depth) and rainfall duration for different return periods (or frequency).

1. In the Analysis Criteria workspace, click Open Rainfall Manager.

2. In the Rainfall Manager, click the IDF tile. The IDF Creation editor opens.

   

3. In the Name field, enter a unique name for the rainfall set.

To Import an IDF Dataset

Multiple IDF rainfall curves can be created for different return periods by specifying rainfall intensity (or depth) values for different rainfall durations.

1. Click to import idf data files. The supported files are as follows:

   • Custom file (.csv)
   • NOAA file (.csv)
   • Hydraflow IDF file (.idf)
   • SSA IDF file (.idfdb)

2. The data is then presented in a table and an IDF curve graph.

   Note: use the Show graph button to hide and show the curve graph.

   

   The table and IDF curve graph can display either Depth or Intensity data. Data displays using the units defined in the source drawing.

   Note: there must be at least 2 entries containing the minute increment and its coinciding rain depth in inches (or millimeters depending on drawing units).

3. Click Create IDF to add IDF rain data set to the Rainfall List.

To Modify IDF Sets

1. In the IDF data list, select the set to be modified. The IDF editor displays.

2. To add or delete more duration rows to the set:

   • Add new row. Adds a new duration row at the bottom of the IDF set.
   • Insert row above. Adds a new duration row above the currently selected row.
   • Insert row below. Adds a new duration row below the currently selected row.
   • Delete row. Deletes the currently selected row.

3. To add, edit or delete return period columns, click Set return period . The Set return periods editor displays:

   • In the Enter number of years field, enter a number representing the year duration of the return period, then click Add.

   • To edit or delete a return period, click the corresponding .

     Click Save to accept changes to the return periods.

4. Click Save Changes to accept changes to the IDF dataset.