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Draw River Reaches Command

The Draw River Reaches command enables the user to draw a river reach on the Map View.

From the Input ribbon menu, select the River Reaches menu item, and then choose Draw River Reaches command.

Selecting this command will display the Draw River Reaches dialog box.

The following sections are used for defining data when 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 natural looking river reach. The software will fit a cubic spline through the digitized points, as shown below.

While digitizing the river reach polyline, the user can interactively toggle between linear (straight line) and curvilinear digitizing by holding down the [Ctrl] key. This provides more control over the placement of the river reach polyline where additional detail is needed.

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 a 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 entry 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.

About the Author Chris Maeder

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