Retention Basin
Creation Mode: Draw Polygon on Terrain
Purpose and Effect: This action allows you to modify the terrain by defining a basin to store flood water. Draw a polygon to set its outline. Configure the parameters for depth and slope in the Action Settings Panel to customize its shape.
Action Settings
Angle of Slope
This setting can be used to modify the shape of the basin: the higher the value, the steeper the slope.
Slope Interpolation
The four interpolation types allow you to define how the depth values of the basin and the base elevation are interpolated.
Hint: In the Action Tool Panel of the Retention Basin you can enable the display of the interpolation area enclosed by two lines with Show Interpolation Lines, as shown in gray above.
Depth Determination Mode
A basin's depth is defined by a separate setting. The interpretation of this depth is determined by one of three available modes:
| Relative to Terrain (default): The base elevation is determined by the underlying terrain, which is equally decreased by the depth of the basin. |  |
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| Absolute Elevation: The base elevation is determined by the underlying coordinate system. The terrain is decreased by applying the absolute depth of the basin. |  |
| Line Elevation: The depth of the basin can be freely modified via blue handles at the control points of its outline in edit mode. | .png) |