Draw and Assign River Junctions Command

River junctions are defined as locations where two or more river reaches join together or split apart.

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

• Draw River Junctions
• Assign River Junctions

Drawing/Assigning River Junctions

The Draw/Assign River Junctions command allows the user to manually draw/assign multiple nodes on the Map View as river junctions, one after another until completed.

Follow the steps below to use the Draw/Assign River Junctions command:

1. From the Input ribbon menu, click on the River Reaches dropdown menu and then choose the Draw/Assign River Junctions command.
   
2. The following dialog boxes will be displayed.
   • Draw River Junctions:
     
   • Assign River Junctions:
     

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

Drawing River Junctions

Drawing River Junction Node

The River Junction Node section is used to manually draw nodes on the Map View as river junctions. The user can draw the river junctions either before or after the river reaches have been created. However, it is generally better to place the river junctions first, and then connect the river reaches to the junctions.

To draw a river junction node, follow the steps below:

1. Click the [Draw] button, and the dialog box will temporarily disappear.
   
2. The status bar (shown under the Map View) will prompt you to select a river junction node location on the Map View. Click on the Map View to place the river junction node. To abort the draw command, press the [Esc] key.
   Notes:
   • 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 river junction to snap to the nearest HEC-RAS element.
3. Following placement of a river junction, the Draw River Junctions dialog box will be redisplayed, and the River junction node read-only field will be changed from Not Drawn to Drawn.
   

Assigning River Junctions

Selecting River Junction Node

The Select River Junction Node section can be used to manually assign previously drawn nodes on the Map View as river junctions. Note that at least three river reaches must be connected to the node to be assigned as river junctions.

To select river junction nodes, follow the steps below:

1. Click the [Pick] button and the dialog box will temporarily disappear.
   
2. The status bar (shown under the Map View) will prompt you to select a node from the Map View as a river junction. Click on the previously drawn junction node on the Map View to select it.
   
3. Following the selection of a junction node, the Assign River Junctions dialog box will be redisplayed, and the River junction node read-only field will be changed from Not Selected to Selected.
   

Note that if a river junction node has been preselected before running this command, the River junction node read-only field will be shown selected on opening the Assign River Junctions command.

Junction Specifications

This section is common to both the Draw River Junctions and Assign River Junctions dialog boxes and is used to specify the data for each drawn/assigned river junction.

The following data are provided in this section:

• River junction name
  This entry field allows the user to provide the river junction name. Note that the river junction name must be unique. Otherwise, the Duplicate Junction Name dialog box will be displayed.
  To abort the rename operation, press the [Esc] key.
• Steady flow computation mode
  This dropdown combo box allows the user to select the computational method to be used at the junction when performing steady flow hydraulic computations. The following methods are available in the dropdown combo box.
  To learn more about the methods available in the dropdown combo box, refer to this article in our knowledge base.
• Unsteady flow computational mode
  This dropdown combo box allows the user to select the computational method to be used at the junction when performing unsteady flow hydraulic computations. The following methods are available in the dropdown combo box.
  To learn more about the methods available in the dropdown combo box, refer to this article in our knowledge base.
• Description
  The Description box allows the user to describe the location of the river junction in more detail.

Junction Type

The dialog box automatically defines the types of river junctions of the selected node. The software automatically determines the type of junction based upon the number of river reaches that are connected to the node, as well as the direction of the river reaches. The user cannot override the selected junction type radio button option.

The following types of junctions are available in the dialog box:

Undefined Junction

This radio button selection section defines the junction as undefined when the following conditions have not been met:

• Three or more river reaches connecting to the junction node.
• Only one river reach pointing downstream towards or downstream from the junction node.

Confluence Junction

This radio button selection section defines data for river confluences, where rivers combine flow into a single reach. This junction type requires the following conditions to be met:

• Three or more river reaches connected to the junction node.
• One river reach pointing downstream from the junction node.

The following data correspond to this radio button selection section.

To learn more about this section, refer to this article in our knowledge base.

Split Flow Junction

This radio button selection section is used to define data for split flow diversions, where a river splits into two (or more) river reaches. This junction type requires the following conditions to be met:

• Three or more river reaches connecting to the junction node.
• One river reach pointing downstream towards the junction node.

The following data corresponds to this radio button selection section:

To learn more about this section, refer to this article in our knowledge base.