Last Modified: Oct 20, 2022 09:23

Software Version

HEC-HMS version 4.11 was used to create this tutorial. You will need to use HEC-HMS version 4.11, or newer, to open the project files.

Overview

In this tutorial you will create a new basin model consisting of three subbasins, two junctions, and a routing reach; then you will connect the elements to form a hydrologic network, and finally enter parameter data for these hydrologic elements.

Steps

  1. Open HEC-HMS.
  2. From the File | New menu, create a new project.
  3. Name the project "Punxsutawney". Set the default unit system to U.S. Customary.
  4. From Components on the menu bar, select the Basin Model Manager option. The Basin Model Manager window will open.
  5. Click the New… button to begin the process of creating a basin model. The Create A New Basin Model window will open.
  6. Change the default basin model name (Basin 1) to Punxsutawney and add the description Headwaters to the City of Punxsutawney - Existing Conditions.
  7. Click the Create button when all the information is correct. The new, empty basin model will be added to the Watershed Explorer. Close the Basin Model Manager.
  8. Set the default methods for subbasins and reaches that will be used when creating new elements. From the Tools menu, select the Program Settings … option.
  9. Select the Defaults tab and set the default loss method to Initial and Constant, the default transform method to Clark Unit Hydrograph, the default baseflow method to Linear Reservoir, and the default routing method to Lag. Click the OK button when you have finished making the selections.
  10. Open the basin model by clicking on it in the Watershed Explorer.
  11. Click the subbasin creation tool icon  in the components toolbar.
  12. Click on the basin map to create the first subbasin element. You can use the default name.
  13. Add two more subbasin elements.
  14. Switch to the reach creation tool and click on the basin map to create a reach element.
  15. Switch to the junction creation tool and add two junction elements to the basin map. The elements should be placed as shown in the figure below.
    Figure 1.  Creating the elements in the basin model.
  16. Connect the elements into a hydrologic network as shown in the figure below. Right click on each element and select the Connect Downstream option. Use the mouse to identify the element that should be downstream. A connection line is drawn to show the elements are connected.
    Figure 2.  Connected basin model elements.

    Question: In this step modeling elements are graphically connected. What is another way to connect elements?

    Elements can be connected from the component editor for a given element by selecting a downstream element.

  17. Click on the Subbasin-1 icon in the Watershed Explorer and rename it to Stump Creek.
  18. Similarly, click on the other subbasin elements and rename them too; Subbasin-2 becomes EB Mahoning Creek and Subbasin-3 becomes Mahoning Creek Local as shown in the figure below.
    Figure 3.  Basin model with local subbasin names.
  19. Enter the area for each of the subbasins. First select basin model, then Click on the Parameters menu and select the Subbasin Area option. Enter the area as shown in the table below

    NameArea (mi2)
    EB Mahoning Creek41
    Stump Creek

    29

    Mahoning Creek Local88

    Parameters | Subbasin Area

    Input the subbasin areas provided in the table above

  20. Set up Baseflow Parameters. From the Parameters menu, select the Baseflow and then Linear Reservoir option. 
  21. Enter the values from the table below, then click the Close button when finished. Be sure to select the correct type of initial condition: Discharge Per Area. Also be sure to select the correct number of layers:

    SubbasinNumber of LayersInitial TypeGW 1 InitialGW 1 FractionGW 1 CoefficientGW 1 StepsGW 2 InitialGW 2 FractionGW 2 CoefficientGW 2 Steps
    EB Mahoning Creek2Discharge Per Area10.570110.51001

    Stump Creek

    2Discharge Per Area

    1

    0.570110.51001
    Mahoning Creek Local2Discharge Per Area10.570110.51001

    Parameters | Baseflow | Linear Reservoir

    Input baseflow Parameters provided in the table above

  22. Set up Loss Parameters. From the Parameters menu, select the Loss and then Initial and Constant option. Enter the values from the table below, then click the Close button when finished.

    SubbasinInitial Loss (in)Constant Rate (in/hr)Impervious (%)
    EB Mahoning Creek10.10
    Stump Creek10.10
    Mahoning Creek Local10.10

    Parameters | Loss | Initial and Constant


    Input the Initial loss, Constant rate and Impervious parameters provided in the table above

  23. From the Parameters menu, select the Transform and then Clark Unit Hydrograph option. Enter the values from the table below, then click the Close button when finished.

    SubbasinTime of Concentration (hr)Storage Coefficient (hr)
    EB Mahoning Creek711
    Stump Creek912
    Mahoning Creek Local1013

    Parameters | Transform | Clark Unit Hydrograph

    Input Time of Concentration and Storage Coefficients provided in the table above

    Question: In steps 20-23 modeling methods are parameterized from the Parameters menu. What is an alternative way to parameterize modeling methods in the HEC-HMS user interface?

    The component editor is an alternative way to parameterize the model. Globally editing tends to be much faster when parameterizing multiple elements of the same modeling method.


  24.  On the basin map in the desktop area, click the Reach-1 element to open its Component Editor. Click on the Routing tab and then enter a lag value of 300 minutes.

Summary

You have now completed steps for adding hydrologic elements to a basin model, connected the hydrologic elements to form a hydrologic network, and parameterized the methods used to simulate hydrologic processes.

Project Files

Download the final project files here:

Final_Create_New_Basin.zip

Continue to Creating a New Meteorologic Model