First of all, be sure you really need to import the data.  Most calculations can be done automatically within HydroCAD, eliminating the need to import hydrograph data.

If you do need to import the data (perhaps from another runoff model?) there are several ways to use a "link" to accomplish the task:

1) If you have only a few flow values, you can enter the data manually into the link:  Just drag a link onto the diagram, double-click to edit, and select "Enter hydrograph manually."  Select the "Manual" tab and enter the data.

2) To avoid typing the values, you can right-click the manual entry table and select "Load From File".  You'll need a CSV file with the flow values in the first column.

3) If you want to specify a different hydrograph for several events, then you'll need to create a special hydrograph file with a .HCE extension.  It's a plain text file that contains a complete hydrograph for each event, as shown below.  Just follow this model, omitting the comments I've added to each line.

FileUnits=English
Comment=This is a sample multi-event hydrograph file

[hydrograph]    // marks the start of each event
Name=Outflow   // all hydrographs should have the same name
Event=2-Year    // event name MUST match an event in the project
Area=8733780   // inflow area in square-feet (optional)
t0=32400        // hydrograph start time in seconds
dt=360          // hydrograph time increment in seconds
Flow= 0  1  4  8.2  9 8   // flow values in CFS
Flow= 7.5  4  3.5  3      // use as many lines as required
Flow= 2.85  2  0.9  .6  0 // any number of values per line

[hydrograph]    // repeat the same format for each event
Name=Outflow
Event=5-Year
Area=8733780
t0=32400
dt=360
Flow= 0  1  4  8.2  9 8
Flow= 7.5  4  3 2  1  0

After creating the HCE file, edit the link and select "Import Hydrograph from file."  Click the "File" tab and use the Browse button to select the file.  Click OK to save the link.  The link will now produce the corresponding hydrograph as you change the event selection in HydroCAD.

For further details on the HCE file format please see www.hydrocad.net/filetypes.htm

Thank You