In the uniform flow computations, the HEC-RAS default Conveyance Subdivision Method is used to determine total conveyance. Subareas are broken up by roughness value break points and then each subarea's conveyance is calculated using Manning's equation. Conveyances are then combined for the left overbank, the right overbank, and the main channel and then further summed to obtain the total cross section conveyance. Refer to "Theoretical Basis for One-Dimensional and Two-Dimensional Hydrodynamic Calculations" for more detail.