Return to Accessing Data and Setting up Meteorologic Model

Navigate to the Hypothetical Storm Editor Panel for Hyp_HMR51_Storm7 and click the Fit Parameters calculator button to open the Depth Area Duration Table dialog. The Depth Area Duration table can take either depths, in inches or mm, or reduction factors normalized to the smallest area (typically 10 square miles or the square km equivalent). Default values for duration (row 1) and area (column 1) are filled in, but can be copied over to customize for your dataset.  The figure below steps through how to copy data into the dialog.

  1. The default number of duration columns is 13 with default values from 6 hours up to 240 hours.  Use this column spinner to increase or decrease the number of columns for copying in your data. Blank columns with no depths or factors will be ignored in calculations.
  2. Default duration and area values are loaded into each table.  These values can and should be overwritten for the user's dataset. Cells can be directly copied over to customize values. When the unit system is switched, the Area values will automatically be converted, but depths and computed fitted parameters will remain the same.
  3. Select the Depths or Factors option for your dataset. Factors range 0 to 1 and Depths will be normalized to a factor based on the lowest area provided in the table which should be around 10 square miles.
  4. After data has been input, you can decide to use or not use a particular dataset with Apply Depth-Area Duration Table box and the Plot? button can be used to include the points from a dataset on the depth area reduction plots.

Input data units consistency

The software can fit parameters to either depths or reduction factors, however the input must be consistent across all input datasets.  If using reduction factors, it's customary that at or around 10 square miles of drainage area is assumed to be a point and no reduction is applied. Similarly, the unit system used for area should be consistent with the unit system of the Basin Model. The parameters will not automatically update if the unit system is switched after fitting.

Copy in Depth Area Duration Table

  1.  Open the storm7.csv file.
  1. Copy in the full table from the storm7.csv file into the table in HEC-HMS.
  2. Double click on the tab labeled Dataset 1 and change the table name to Storm7.
  3. Click Apply and then Fit Parmaters. The parameters will populate in the editor panel. Also notice that the coefficient of determination, R2, is calculated and appears in the bottom left of the dialog. This describes the goodness of fit of your parameters to your input datasets, the closer to 1, the better.


Depending on the duration and intensity of storm that the parametric depth area reduction curve will be applied to, you may choose to use storms of similar duration or annual exceedance probability. For this tutorial, we'll try a few different sets of input data and their respective parameters to compare results. Repeat steps 1 through 4 for the Hyp_HMR51_ShortStorms Meteorologic Model. Copy in data for Storm 57 and Storm 65. Use the Add DAD table button to add a second table. Rename your datasets as Storm57 and Storm65, respectively. Notice that three existing Meteorologic Models are already in the model for you, we'll use these later for comparison purposes:

  •  Hypo Storm User-Spec Storm47 - User-specified area reduction curve based on 96 hr reduction factors of observed HMR 51 historic Storm 47
  • Hypo Storm User-Spec 100YR -  User-specified area reduction curve based on 96 hr reduction factors of 100 yr NOAA precipitation grid
  • Hyp_HMR51_AllStorms - Parametric Area Reduction with parameters fit to all HMR51 TX storms

To Use or Not to Use

Notice the Use? toggle button in the upper left of the dataset table dialog. This allows you to include or exclude different datasets when fitting parameters.