Detailed field measurements of channel properties and flow characteristics collected in the Ashley and Cropp catchments (New Zealand) are used to investigate the spatial variation of resistance to flow across upland channel networks. The application of the Darcy-Weisbach equation and semilogarithmic flow resistance relationships reveals that mean flow velocities calculated from local measurements of bed material particle size, hydraulic depth, and channel bed slope may be inaccurate. The Manning-Gauckler-Strickler equation with resistance coefficient independent of bed material particle size is found to be relatively more reliable but not sufficiently general to reproduce the spatial variation of resistance to flow across a complex channel network. A new methodology is developed by combining a hydraulic equation of the Manning-Gauckler-Strickler type, a flow discharge-upstream drainage area relationship, and geomorphological fluvial relationships for mean flow velocity, Gauckler-Strickler resistance coefficient, hydraulic depth, and friction slope. This methodology is found to improve the reproduction of the spatial variation of mean flow velocity across the Ashley catchment and appears of general applicability for the parameterization of resistance to flow in distributed catchment models.