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Draw and Assign Junctions Command

Junction elements are used to combine runoff and stream flow from hydrologic elements located upstream. The inflow into the junction element can come from one or multiple upstream elements.

In GeoHECHMS, junctions can be defined by either drawing or assigning nodes on the Map View using the following commands:

  • Draw Junctions
  • Assign Junctions

Drawing Junctions

The Draw Junctions command allows the user to interactively draw nodes on the Map View as junctions.

Follow the steps below to use the Draw Junctions command:

  1. From the Input ribbon menu, select the Routing Junctions dropdown menu and then choose the Draw Junctions command.
    Draw Junctions ribbon menu command
  2. The Draw Junctions dialog box will be displayed.
    Draw Junctions dialog box

The following sections describe how to use the Draw Junctions command and interact with the above dialog box.

Drawing Junction Nodes

The Draw Junction Nodes section is used to place/draw the junction on the Map View using nodes. To draw a junction node, follow the steps below:

  1. Click on the [Draw] button and the dialog box will temporarily disappear.
    Draw Junctions dialog box - Draw Junction nodes section
  2. The status bar (shown under the Map View) will prompt you to place a junction node on the Map View.
    Placing junction node on Map ViewNotes:

    • To place the node more accurately, use the mouse roller wheel to zoom into a specific location.
    • The Snap Mode option can be enabled to cause the drawn junction to snap to the nearest HEC-HMS element.
  3. After placing the junction, either press the [Enter] key or right-click and select Done from the displayed context menu. The user can press the [Esc] key to abort the draw command.
  4. After completing the junction drawing, the Draw Junctions dialog box will be redisplayed, and the Junction nodes read-only field will be changed from Not Drawn to Drawn.
    Draw Junctions dialog box - Junction nodes drawn

Junction Specifications

This section is used to specify the junction ID for each drawn junction. The user can assign these IDs either manually or automatically using some predefined formats.

Follow the steps below to assign junction IDs to the junctions:

  1. If a junction has been drawn while the Junction ID radio button option was selected, the user can manually enter the junction ID in the corresponding field as shown below.
    Draw Junctions dialog box - Junction ID
  2. Alternately, the user can enable the Auto-name junction ID radio button option in order to automatically name every newly drawn junction as per the user’s predefined naming formats as shown below.
    Draw Junctions dialog box - Auto-name junction IDThe different junction naming formats present in the Auto-name junction ID option are as follows:

    • Junction ID prefix: This option allows a prefix to be added to the start of the junction ID.
    • Junction ID digits: This option permits specification of a set number of digits to use for the junction ID. For example, using 3 digits causes the junction ID to be of the format 001, 002, etc.
    • Next available junction ID: This entry defines the next element ID number to be used.
    • Junction ID increment: This entry defines the increment to use when numbering elements. The default value is 1.
    • Junction ID suffix: This option allows a suffix to be added to the end of the junction ID.
    • Junction ID preview: This entry provides a preview of the junction naming specifications defined above.
  3. After providing the Junction ID, press the [Enter] key or click on the [Apply] button.
    Drawing junctionNote that if the auto-name option was selected and the user returns to the dialog box, the [Apply] button is disabled since the just drawn junctions have already been named and created.
  4. The drawn junction will be displayed on the Map View.

Assign Invert Elevation

This section of the dialog box allows the user to assign an invert elevation to the junction using a terrain model. Define this section before drawing the junctions so that the invert elevations can be assigned.
Assign Invert Elevation section

To assign an invert elevation, the Terrain elevation source dropdown combo box supports the following surface types:

  • Elevation grids
  • LandXML data
  • TIN surfaces

The user can also apply an elevation offset to raise or lower the junction by the specified amount by checking the Apply elevation offset checkbox option. On selecting this checkbox option, the entry field next to it becomes available for entering an elevation offset value. A negative offset value will lower the junction by the specified amount.

Assigning Junctions

The Assign Junctions command is used to manually associate previously drawn nodes as junctions.

Follow the steps below to use the Assign Junctions command:

  1. From the Input ribbon menu, select the Routing Junctions dropdown menu and then choose the Assign Junctions command.
    Assign Junctions ribbon menu command
  2. The Assign Junctions dialog box will be displayed.
    Assign Junctions dialog box

The following sections describe how to use the Assign Junctions command and interact with the above dialog box.

Selecting Junction Nodes

The Select Junction Nodes section is used to select the previously drawn nodes from the Map View to assign them as junctions.

Follow the steps below to assign a junction node:

  1. Click the [Pick] button, and the dialog box will temporarily disappear.
    Assign Junctions dialog box - Select Junction nodes section
  2. The status bar will prompt you to select the node on the Map View. Select the junction node on the Map View.
    Junction node selection on Map View
  3. After selecting the junction node, the Assign Junctions dialog box will be redisplayed. The number of selected nodes will be displayed in the Junction nodes read-only field.
    Assign Junctions dialog box - Junction nodes selected

Junction Specifications

This section is used to specify an ID for each selected junction node. The user can assign these IDs either manually or automatically by using some predefined formats.

Note that this section is similar to the Junction Specifications section of the Draw Junctions dialog box. Hence, see the second subsection under Drawing Junctions to learn more about it.

Assign Invert Elevation

This section is similar to the Assign Invert Elevation section of the Draw Junctions dialog box. Hence, see the third subsection under Drawing Junctions to learn more about it.

About the Author Chris Maeder

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