The Input | River Reaches | Draw River Reaches command enables the user to quickly draw a river reach on the Map View.
Selecting this command will display the Draw River Reaches dialog box.
The following sections are used for defining data in drawing river reaches.
Draw River Reach Polyline
This section is used to interactively draw a polyline on the Map View for assigning as a river reach. Click on the [Draw] button and the dialog box will temporarily disappear. A prompt will be displayed at the status line, informing the user what to do next. Within the Map View, draw a polyline along the river in a downstream direction.
After the river reach polyline has been drawn, right-click and select Done from the displayed context menu or press the [Enter] key. The software will then return the user to the dialog box showing that a river reach polyline was drawn.
The river reach flow direction is defined by starting at the upstream end and then progressing in a downstream direction. A flow directional arrow is shown at the center of the river reach to show the assigned flow direction. If the river reach is accidentally drawn in an upstream direction, click on the [Reverse Direction] button.
Note that the Create curvilinear polyline checkbox option can be used to create a more naturally looking river reach. The software will fit a cubic spline through the digitized points, as shown below.
River Reach Specifications
This section is used to define the river name and reach name of the river reach that was digitized. Note that each river reach must have an unique ID which is formed from the combination of the river name and reach name. This is how the HEC‑RAS software can correctly identify each river reach.
The river name dropdown combo box can be used to select from an existing river name or to create a new river name.
To create a new river name, either select Add New River from the dropdown combo box listing or click the [New] button. The software will then provide an empty field to define the new river name.