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Draw and Assign Diversions Command

A diversion is an element with two outflows, main and diverted, and one or more inflows. Inflow comes from other elements in the basin model. If there is more than one inflow, all inflows are added together before computing the outflows. A diversion can be used to represent weirs or pump stations that divert flow into canals or off-stream storage. The diversion element includes optional properties for limiting the amount of diverted flow.

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

  • Draw Diversions
  • Assign Diversions

Drawing Diversions

The Draw Diversions command is used to manually draw multiple diversion nodes on the Map View, one after another until completed.

Follow the steps below to use the Draw Diversions command:

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

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

Drawing Diversion Nodes

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

Drawing Individual Diversions

To draw diversions one at a time, naming each individual diversion before drawing the next one, follow the steps below:

  1. From the Diversion Specifications section, select the Diversion ID radio button option.
  2. Click the [Draw] button, and the dialog box will temporarily disappear.
    [Draw] button
  3. The status bar (shown under the Map View) will prompt you to place a diversion on the Map View. Click on the Map View to place the diversion. To position the diversion more accurately, use the mouse roller wheel to zoom into a specific location. The Snap Mode option can be enabled to cause the drawn diversion to snap to the nearest HEC-HMS element.
    Snap Mode option
  4. Following placement of a diversion, the user is immediately returned to the Draw Diversions dialog box, and the Diversion nodes read-only field will be changed from Not Drawn to Drawn.
  5. Enter a unique name to identify the drawn diversion in the Diversion ID entry field. After entering the name, press the [Enter] key or click the [Apply] button.
    [Apply] button – Draw Diversions dialog box
  6. Continue this process of drawing one diversion at a time until all the diversions have been placed on the Map View. When finished, click the [Close] button to close the dialog box.

Drawing Multiple Diversions

To draw multiple diversions continuously without having to purposefully interact with the dialog box to identify and name each diversion, follow the steps below:

  1. From the Diversion Specifications section, select the Auto-name diversion ID radio button option.
    Auto-name diversion ID radio button optionThe different naming formats present in the Auto-name diversion ID option are as follows:

    • Diversion ID prefix: This option allows a prefix to be added to the start of the diversion ID.
    • Diversion ID digits: This option permits specification of a set number of digits to use for the diversion ID. For example, using 3 digits causes the diversion ID to be of the format 001, 002, etc.
    • Next available diversion ID: This entry defines the next element ID number to be used.
    • Diversion ID increment: This entry defines the increment to use when numbering elements. The default value is 1.
    • Diversion ID suffix: This option allows a suffix to be added to the end of the diversion ID.
    • Diversion ID preview: This entry provides a preview of the diversion naming specification defined above.
  2. Click the [Draw] button and the dialog box will temporarily disappear.
    [Draw] button
  3. On the Map View, click at a point to place the diversion. To position the diversion more accurately, use the mouse roller wheel to zoom into a specific location.
  4. After drawing the first diversion, a prompt will be displayed on the status bar asking you to place the next diversion.
    Status bar prompt for placing diversions
  5. Continue this process of drawing one diversion at a time until all the diversions have been placed on the Map View. When finished, right-click and choose Done from the displayed context menu or press the [Enter] 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 to the diversion using a terrain model. Define this section before drawing diversions so that the invert elevations can be assigned.

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 diversion by the specified amount by checking the Apply elevation offset checkbox. On selecting this checkbox, the entry field next to it becomes available for entering an elevation offset value. A negative offset value will lower the diversion by the specified amount.

Assigning Diversions

The Assign Diversions command is used to manually associate previously drawn nodes as diversions. Note that this command works similarly to the Draw Diversions command.

Follow the steps below to use the Assign Diversions command:

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

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

Selecting Diversion Nodes

Selection of a naming method from the Diversion Specifications section should be considered before selecting diversion nodes. If the Diversion ID radio button option is selected, then only one node can be selected and assigned as a diversion at a time. By contrast, if the Auto-name Diversion ID radio button option is selected, the user can interactively and continuously select nodes on the Map View to assign them as diversions without having to purposefully interact with the dialog box each time a diversion needs to be identified and named.

Assigning Individual Diversions

To assign diversions one at a time, naming each individual diversion before assigning the next one, follow the steps below:

  1. From the Diversion Specifications section, select the Diversion ID radio button option.
  2. From the Select Diversion Nodes section, click on the [Pick] button, and the dialog box will temporarily disappear.
    [Pick] button
  3. The status bar (shown under the Map View) will prompt you to select a diversion node from the Map View. Click on the previously drawn diversion node on the Map View to select it. The Snap Mode option can be enabled to cause the selected diversion node to snap to the nearest HEC-HMS element.
    Status bar prompt for selecting diversion node
  4. Following selection of a diversion node, the user is immediately returned to the Assign Diversions dialog box, and the Diversion nodes read-only field will be changed from Not Selected to Selected.
  5. Enter the unique name to identify the selected diversion node in the Diversion ID entry field. After entering the name, press the [Enter] key or click on the [Apply] button.
    [Apply] button – Assign Diversions dialog box
  6. Continue this process of assigning one diversion at a time until all the diversions have been defined on the Map View. When finished, click the [Close] button to close the dialog box.

Assigning Multiple Diversions

To assigns multiple diversions continuously without having to purposefully interact with the dialog box to identify and name each diversion node, follow the steps below:

  1. From the Diversion Specifications section, select the Auto-name diversion ID radio button option. Note that the naming format in the Auto-name diversion ID option works similar to that of the Draw Diversions dialog box.
  2. From the Select Diversion Nodes section, click on the [Pick] button, and the dialog box will temporarily disappear.
    [Pick] button
  3. On the Map View, click on a previously drawn diversion node to select it. The Snap Mode option can be enabled to cause the selected diversion node to snap to a HEC-HMS element. The status bar will display the number of selected diversion nodes.
    Status bar prompt displaying the count of selected diversions
  4. Continue this process of selecting one diversion node at a time until all the nodes on the Map View have been assigned as diversions. When finished, right-click and choose [Done] from the displayed context menu or press the [Enter] key. You will be returned to the dialog box. Click the [Close] button to close the dialog box.

Note that the Assign Invert Elevation section of the Assign Diversions command is similar to that of the Draw Diversions command. Hence, refer to the Assign Invert Elevation section of this article to learn more about it.

About the Author Chris Maeder

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