This tutorial describes how to edit a river in a Digital Surface Model (DSM).
Flowing water like rivers must be flattened into steps due to the changing
elevation of the water surface along the river course.
Prior to commencing a project perform the following steps.
Flowing water like rivers and streams can be editing using river centerlines drawn manually or semi-automatically.
Start Collection
Click 2DRiver.shp in the TOC to remove from the View
Navigate to the western most portion of the river
Within the Shapes tab click Trace In Class
Press Shift + Left Click over a non-void pixel within the river to start the centerline.
Note: The height of the node is taken from the DSM. If all water is void the elevation can be set manually.
End Collection
River centerlines can be collected between a start and end node saving time delineating the river.
Navigate to the eastern most portion of the river
Within the Shapes tab click Trace In Class
Press Shift + Left Click over a non-void pixel nearest the end of the river
Notes:
The centerline is delineated from the first node to the last node along the river classification
The height of the last node is taken from the DSM. If all water is void the elevation can be set manually
All elevations within the River shape are intepolated between the first and last node
Review and Control River Elevations Along Centerline
River slopes vary along the coarse of flow. To ensure that river elevations do not "float" above the shoreline it is recommended
that the elevation of some of nodes along the river coarse are set.
In some instances such as when a river has been void filled the river must be lowered below neighboring tree heights.
Working from the western portion of the river (top to bottom)locate nodes intermittently that are over non-void river pixels
Mouse over the node and nearby non-void water heights. If they are close to one another continue down the river
When the centerline height does deviate from the river perform the following:
Press Shift + Right Click over the node to be changed
Select Set Elevation
Select Fixed for the Z mode
Enter the new height for the node
Repeat as required
Notes:
All elevations within the River shape are intepolated between the manually set elevation nodes
The centerline can be applied (below) and this step can be revisited as needed.