Flow paths are used for calculating the catchment Time of Concentration (Tc) value. A flow path may use the TR-55 calculation method to calculate the Tc, or it may have a user-defined Tc.
A flow path defines the path that water travels in the catchment between the hydraulically most distant point in the catchment and the discharge point. Flow paths may have one or more flow segments. Flow segments define locations along the flow path line where there is a change in flow type, ground cover, and slope.
- A flow path may be calculated from a surface, using the surface terrain to determine the path the water would flow, or it may be defined from a polyline.
- A flow path may be defined initially when you create the catchment, and it may be created or edited with the Create Flow Path From Surface and Create Flow Path From Object commands.
- When a flow path is initially created, it is created with the number of flow segments defined in the Catchment Settings.
- A flow path may have multiple segments if the Tc method is specified as TR-55. You can use the Create Flow Segments command to divide a flow path into more segments. A flow path that has a user-defined Tc can only have one flow segment.
- You can edit the flow segment data using the Edit Flow Segments command.
- Flow paths do not have grips.
- Flow segment lengths and slopes cannot be edited by moving the flow segment start or end points. To change the length or slope of a segment, you can delete a segment and recreate it.