The first step in performing a frequency analysis within HEC-SSP is to establish which directory you wish to work in and to enter a title for the new study.

  • Create a new HEC-SSP study.
  • Name this project “Parametric_Modeling”.
  • Leave the Unit System and Coordinate System set to their default values of English and Geographic, respectively.

Before any analyses can be performed, data must be imported to the HEC-SSP study.  Within this study, you will utilize data for a National Weather Service (NWS) precipitation gage located at Detroit Dam as well as a Natural Resource Conservation Service (NRCS) Snow Telemetry (SNOTEL) station located near Detroit Dam.  The locations of these data sources in relation to Detroit Dam is shown in Figure 1.  This data must be imported using HEC-DSSVue plugins. In this tutorial, we will only be analyzing the precipitation data. If you are interested in analyzing the SNOTEL SWE data, check out the full Parametric Modeling tutorial.

Detroit Lake and Data Source Locations

You must import the NWS precipitation data to the HEC-SSP study.  This information has already been loaded into a DSS file for you.  However, this information can be easily ingested to a DSS file using the NCDC plugin as described within the Introduction to HEC-SSP Task 6. Import Data using an HEC-DSSVue Plugin tutorial.

  • Click Data | New | Using Import Wizard to open the new Data Importer Wizard.
  • Enter DETROIT DAM 3DAY PRECIP in the Name field.
  • Click the Next button.
  • Change the Source to HEC-DSS and click the Next button.
  • Click the ellipsis button within the Selected DSS File entry field.
  • Within the pop up window, navigate to and select the Detroit_Dam_Precipitation.dss file.
  • Click Open to select this file.  This will cause two records to populate within the table listing selectable data sets.

  • Double left click on the 3-day duration dataset to add it to the window at the bottom of the Data Importer.
    New Data Import Wizard

  • Click Next and review your data one last time.
  • When ready, click Import to to import the data set and return to the main HEC-SSP desktop.
  • Edit the metadata for the precipitation data sets to better identify it as the 3-day time series. The Study Explorer should appear similar to the figure below.
  • Click the Save button to save the study.
    3-day Duration Precipitation Data Set

Continue to Task 2. Fit and Compare Multiple Models to the Winter Season 3-day Precipitation Time Series.