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Draw 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 the Draw Junctions command is used to interactively draw multiple junction nodes on the Map View. The user can also assign a unique junction ID and the invert elevation using this command.

Follow the steps below to use the Draw Junctions command:

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

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

Drawing Junction Nodes

Selection of a naming method from the Junction Specifications settings should be considered before drawing (or placing) junctions. If the Junction ID radio button option is selected, then only one junction can be drawn at a time. By contrast, if the Auto-name junction ID radio button option is selected, the user can interactively and continuously draw junctions on the Map View without having to purposefully interact with the dialog box each time a junction needs to be identified and named.

Drawing Individual Junctions

To draw junctions one at a time, naming each individual junction before drawing the next junction, follow these steps:

  1. From the Junction Specifications settings section, select the Junction ID radio button option.
  2. From the Junction node entry, click on the [Draw] button and the dialog box will temporarily disappear.
  3. The status line (shown under the Map View) will prompt you to place a junction on the Map View. Click on the Map View to place the junction. To position the junction 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 a HEC-HMS element (e.g., at the end of a previously drawn reach).
  4. Following placement of a junction, the user is immediately returned to the Draw Junctions dialog box, and the Junction node read-only field will be changed from Not Drawn to Drawn.
  5. After entering the Junction ID, press the [Enter] key or click on the [Apply] button.

Continue this process of drawing one junction at a time until all the junctions have been placed on the Map View. When finished, click the [Close] button to close the dialog box.

Drawing Multiple Junctions

To draw multiple junctions continuously and without prompting from the software to name each individual junction, follow these steps:

  1. From the Junction Specifications settings section, select the Auto-name junction ID radio button option.
    The different 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 front 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.
  2. From the Junction node entry, click on the [Draw] button and the dialog box will temporarily disappear.
  3. The status line (shown under the Map View) will prompt you to place a junction on the Map View. Click on the Map View to place the junction. To position the junction 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 a HEC-HMS element (e.g., at the end of a previously drawn reach).
  4. From the Map View, click on a point to place the junction. To position the junction 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 a HEC-HMS element (e.g., at the end of a previously drawn reach).
  5. After drawing the first junction, the software will prompt you to place the next junction on the status line.
  6. Continue this process of drawing one junction at a time until all the junctions have been placed on the Map View. When finished, right-click and choose [Done] from the displayed context menu or press the [Enter] or [Esc] key. You will be returned to the dialog box. Click the [Close] button to close the dialog box.

Assign Invert Elevation

This section of the dialog box allows the user to assign an invert elevation using a terrain model while drawing junctions. Define this section before drawing junctions in order that the invert elevations can be assigned. Alternatively, the Assign Junction Elevations command can be used at a later time to assign elevations to the junctions.
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 the elevation offset by enabling the Apply elevation offset check box entry. To lower the junction for specific circumstances—a manhole bottom elevation, for example—define a negative offset value.

About the Author Chris Maeder

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