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
The Draw/Assign Junctions command allows the user to manually draw/assign multiple nodes on the Map View as junctions, one after another until completed.
Follow the steps below to use the Draw/Assign Junctions command:
- From the Input ribbon menu, select the Routing Junctions dropdown menu and then choose the Draw/Assign Junctions command.
- The following dialog box(s) will be displayed.
- Draw Junctions:
- Assign Junctions:
- Draw Junctions:
The following sections describe how to use the Draw/Assign Junctions command and interact with the above dialog box(s).
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:
- From the Draw Junction Nodes section, click the [Draw] button, and the dialog box will temporarily disappear.
- The status bar (shown under the Map View) will prompt you to place a junction node on the Map View. Click on the Map View to place the junction.
- 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.
- Following placement of a junction, the Draw Junctions dialog box will be redisplayed, and the Junction nodes read-only field will be changed from Not Drawn to Drawn.
To abort the current draw command, press the [Esc] key.
Selecting Junction Nodes
The Select Junction Nodes section can be used to manually assign multiple nodes on the Map View as junctions. To assign junction nodes, follow the steps below:
- From the Select Junction Nodes section, click the [Pick] button and the dialog box will temporarily disappear.
- The status bar (shown under the Map View) will prompt you to select a junction node from the Map View. Click on the previously drawn junction node on the Map View to select it.
- Following the selection of a junction node, the Assign Junctions dialog box will be redisplayed, and the Junction nodes read-only field will be changed from Not Selected to 1 Selected.
- Click the [Clear] button to cancel the previous selection and redo the entire process.
This section is common to both the Draw Junctions and Assign Junctions dialog box and is used to specify the junction ID for each drawn/assigned 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:
- If a junction was drawn/assigned while the Junction ID radio button option was selected, the user can manually enter the junction ID in the corresponding field as shown below.
- Alternately, the user can enable the Auto-name junction ID radio button option in order to automatically name every newly drawn/assigned junction as per the user’s predefined naming formats as shown below.
The 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.
- After providing the Junction ID, press the [Enter] key or click on the [Apply] button.
Note 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/assigned junctions have already been named and created.
Assign Invert Elevation
This section is common to both the Draw Sinks and Assign Sinks dialog box and allows the user to assign an invert elevation to the junction using a terrain model. Define this section before drawing/assigning junctions so that 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 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.