Unit Hydrograph Tables
The SCS runoff procedure employs a Unit Hydrograph, which predicts the runoff hydrograph that will be produced by a short burst of rainfall. (See the training slides for complete details.) A prominent feature of the UH is the Peak Factor. Most projects are performed with the default SCS unit hydrograph (PF=484) or the Delmarva unit hydrograph (PF=284).
 | If you wish to use a different peak factor, you must
select a different unit hydrograph on the UH tab of the Settings|Calculation. |
| To examine the UH tables installed on your computer, click View|Unit Hydrograph: |
Additional UH tables may be downloaded for special applications. To use one of these files, right-click the desired link and save the file to your HydroCAD\Rainfall folder. The new UH can then be selected in any HydroCAD project.
SWFWMD-256 Southwest Florida Water Management District, PF=256
Georgia-300
Georgia Stormwater Management Manual, PF=300
Georgia-323
Georgia Stormwater Management Manual, custom table for PF=323
Georgia-484
Georgia Stormwater Management Manual, PF=484
Note: The Georgia tables are commonly used in Florida.
For rare applications that may require other peak factors, you can create a custom unit hydrograph file. For details select Start|Programs|HydroCAD|Unit Hydrograph Info or see the UH.TXT file in the HydroCAD\Rainfall folder.