Share Email Facebook Twitter LinkedIn Catchment Flow Paths and Segments Topics in this section About Catchment Flow Paths and Segments 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. To Work With Flow Path Segments To Create a Flow Path From a Surface To Create a Flow Path From an Object Parent topic: Catchments