Georeferencing Diversions

A diversion is an element with two outflows (main and diverted) and one or more inflows. Inflow comes from other elements in the basin model. If there is more than one inflow, all inflows are added together before computing the outflows. A diversion can be used to represent weirs or pump stations that divert flow into canals or off-stream storage.

In GeoHECHMS, if a diversion is not located at the correct location on the river reach, the Georeference Diversions command can be used to automatically map a diversion to a desired location.

The Georeference Diversions command provides the following options to map a diversion to the desired location:

Follow the steps below to use the Georeference Diversions command:

1. From the Input ribbon menu, expand the Diversions menu item and select the Georeference Diversions command.
   
2. The Georeference Diversions dialog box will be displayed.
   

The following sections describe how to georeference a diversion to a desired location and to interact with the above dialog box.

Selecting Diversion to Georeference

The Select Diversion to Georeference section allows the user to select the diversion that is to be georeferenced. The user can select the diversion from the Diversion ID dropdown combo box that lists all the diversions contained within the model. Alternatively, the user can click the [Pick] button to select the diversion from the Map View.

After clicking the [Pick] button, the Georeference Diversions dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user on what to do next. The user can then interactively select a diversion from the Map View.

Note that the user can select only one diversion at a time to georeference.

Upon selecting a diversion, the dialog box will be redisplayed, and the Diversion ID dropdown combo box updates automatically to match the selected diversion.

The user can click the [Clear] button to unselect the diversion.

Snapping Diversion to an Alignment Point

If an existing alignment point for the diversion exists on the Map View, the Snap to Alignment Point option can be used to snap the HEC-HMS diversion to the alignment point.

The user can click the [Pick] button to select the alignment point from the Map View. On clicking the [Pick] button, the Georeference Diversions dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user on what to do next. The user can then interactively select the alignment point from the Map View.

Upon selecting the point, the dialog box will be redisplayed, and the status of Select alignment point read-only field changes to Selected. Note that the user can select only one alignment point to use for georeferencing.

The user can click on the [Clear] button to deselect the alignment point.

Once the diversion alignment point is selected, click the [Snap] button, and the software will snap the selected diversion to the selected alignment point.

Drawing Diversion Node on Map View

The Draw on Map View radio button option allows the user to draw a diversion node on the Map View to which the selected diversion is to be georeferenced. Selecting the Draw on Map View radio button option enables the [Draw] button.

On clicking the [Draw] button, the Georeference Diversions dialog box will temporarily disappear, and a prompt will be displayed on the status bar instructing the user on what to do next. The user can then draw the diversion node on the Map View.

Once finished, press the [Enter] key or right-click and choose Done from the displayed context menu. The dialog box will be redisplayed, and the selected diversion will be georeferenced to the drawn node.

Assigning Diversion Elevation

The Assign Diversion Elevation section uses the elevation data to assign an invert elevation to the georeferenced diversions. The user should define the data for this section before georeferencing diversions. Alternatively, the user can use the Assign Diversion Elevations command to assign invert elevations to the already drawn diversions. Refer to this article in our knowledge base to learn more about Assign Diversion Elevations command.

For assigning elevation data, the Terrain elevation source dropdown combo box supports the following surface types:

The following surface types are unsupported:

The user can also apply an elevation offset to raise or lower the selected diversions by the specified amount by checking the Apply elevation offset checkbox option. On selecting this checkbox, the user can enter the offset value in the entry field next to Apply elevation offset checkbox option.