HEC-1 HC Card Drainage Area Calculation Tool

Release Date
May 8, 2012

About HEC-1 HC Card Cumulative Drainage Area 

The HEC-1 software internally needs the cumulative drainage areas (adding up all the upstream sub basin areas) for the computation of other HEC-1 cards. For example, the cumulative drainage area is often used in the computation especially when the JD card for the rainfall is used. The HEC-1 software automatically keeps track of the cumulative drainage area for each 'combine' command. When there is a diversion card that diverts flow out of the node/branch/system, the cumulative drainage area for the 'combine' node downstream should be reduced since the flow is taken out. However, the Hec-1 software does not reduce the cumulative drainage area automatically based on the diverted flow. The reduced cumulative drainage area has to be manually estimated and input back into the second field of the 'HC' command.

Ideally, to estimate the cumulative drainage area, the model input file has to be run under HEC-1 to obtain the peak flows before and after the diversion to find the ratio of the peak flow change, which will be used to compute the reduced cumulative drainage area. This reduced cumulative drainage area is then put back into the second field of the 'HC' card for another run of HEC-1. If the flow is retrieved back, the area should be added to the retrieved node, and then run HEC-1 to update the results. If there are more diversions, this procedure has to be repeated for each diversion/retrieval from upstream to downstream, which is time-consuming and sometimes impossible to do.

About HEC-1 HC Card Cumulative Drainage Area Calculation Tool 1.3.0 

This program assumes that the entire area of the immediate upstream hydrology component will be carried in the diversion if there is a diversion, and the entire area is routed to the downstream hydrology component. Based on the above assumption, this program is not running the HEC-1 program to generate the difference of the peak flow to compute the reduced cumulative areas. Instead the combined hydrology component will carry down all the areas it combines to the downstream. With the above assumption such possibility exists that some of the diverted areas might be double counted if these diversions are retrieved back into the system at the same hydrology branch as where the diversions occur. When this happens, the areas should be deducted to avoid double-counting.

Features of HEC-1 HC Card Cumulative Drainage Area Calculation Tool 1.3.0 

  • This program is designed to have very simple and user-friendly interface with minimum user input to run.
  • This program provides the on-screen instruction and quick-tip to assist the user to run the program.
  • This program also provides the users the options of cleaning up the input file, generating the log file, and monitoring the running process.
  • This program provides the on-screen links to view the input file and log file.


If you have any questions, please email Carlos Carriaga

Installation Procedures

  1. Download the installation package (ZIP).
  2. Browse to the location where the installation package was saved, and unzip the package. Double click the "setup.exe" file, and follow the on-screen instruction to finish the installation. It is strongly recommended to use the default installation path. The links of this program point to the default installation location.
  3. After the installation is finished, a shortcut will be generated on the Desktop. Double click the shortcut to launch the program.

Installation Package Details

Included in the installation package:

  • Program Algorithm and Flow Chart
  • Sample input files and running results
  • Test cases
  • User's Manual