Thrown when FlowSegment.FlowType is NOT TR55FlowSegmentType.FlowTypeChannel.
Remarks
This property only takes part in TR-55 calculation when FlowSegment.FlowType is TR55FlowSegmentType.FlowTypeChannel.
The unit of value is defined by the drawing unit in drawing settings (CivilDocument.Settings.DrawingSettings.UnitZoneSettings.DrawingUnits).
Drawing Unit is feet: square foot; Drawing unit is meter: square meter.