Assign Flow Lengths Command

In GeoHECRAS, the Assign Flow Lengths command is used to manually associate previously drawn polylines as left and right overbank flow lengths as well as the (optional) channel flow length. This article describes how to use the Assign Flow Lengths command.

Follow the steps below to use the Assign Flow Lengths command:

1. From the Input ribbon menu, click the Assign Entities dropdown menu and then select the Assign Flow Lengths command.
   
2. The Assign Flow Lengths dialog box will be displayed.
   

The following sections describe how to interact with the above dialog box.

Selecting Cross Sections

The Select Cross Sections section provides a table listing the cross sections contained within the project. This section allows the user to select which cross sections are to be assigned as channel and overbank flow lengths.

By default, no cross sections are selected. Clicking the [Select All] button causes all cross sections to be selected. Clicking the [Clear All] button will cause all cross sections to be deselected. In addition, the user can manually select from the table the cross sections that are to be assigned as channel and overbank flow lengths.

Alternatively, the user can click the [Pick] button to interactively select the cross sections from the Map View. The dialog box will temporarily disappear. Select either cross sections one by one or click on the river reach and all associated cross sections will be selected from the Map View. After selecting the cross sections, press the Enter key or right-click and choose Done from the displayed context menu. The Assign Flow Lengths dialog box will be redisplayed and the total number of selected cross sections will be shown in the Total selected read-only field as shown below.

Note that if a cross section is already selected on the Map View prior to running this command, the same cross section will be shown selected within the table as well as in the Total selected read-only field.

Selecting Junctions

The Select Junctions section provides a table listing the river junctions contained within the project. This section allows the user to select the river junction(s) to compute the flow lengths.

By default, no river junctions are selected. Clicking the [Select All] button causes all river junctions to be selected. Clicking the [Clear All] button will cause all river junctions to be deselected. In addition, the user can manually select from the table the river junctions that are to be updated flow lengths.

Alternatively, the user can click the [Pick] button to interactively select the river junctions from the Map View. After selecting the river junction, press the Enter key or right-click and choose Done from the displayed context menu. The Assign Flow Lengths dialog box will be redisplayed and the total number of selected river junctions will be displayed in the read-only field as shown below.

Note that if a river junction is already selected on the Map View prior to running this command, the same river junction will be shown selected within the table.

Selecting Flow Length Polylines

The Select Flow Length Polylines section allows the user to interactively select polyline(s) on the Map View to be associated as flow lengths.

This section requires the following data:

The user can click the [Clear] buttons to cancel any previous selection and redo the entire process.

Additional Options

This section contains the Assign channel flow lengths to undefined overbank flow lengths checkbox option. This checkbox option is used to assign the channel flow length to the adjacent overbanks if the flow lengths are not already defined. By default, this checkbox option is checked.

Assigning Flow Lengths

After defining all the required data, click the [OK] button. The software will then assign polylines as cross section channel and overbank flow lengths.