Testing flow resistance equation for rill flow

At first, in this paper a flow resistance equation for rill flow, deduced applyingdimensional analysis and self-similarity theory, is presented. The incomplete self-similarityhypothesis is used for establishing the flow velocity distribution whose integrationgives the theoretical expression of the Darcy-Weisbach friction factor.Then the deduced theoretical resistance equation, which is calibrated by somemeasurements of flow velocity, water depth, cross section area, wetted perimeter andbed slope carried out in 106 reaches of some rills modelled on an experimental plot, istested using the literature data by Abrahams et al. (1996), Strohmeier et al. (2014) andPeng et al. (2015) for rill flows.The relationship among the velocity profile, the channel slope and the flow Froudenumber is also calibrated using all available data. Finally the analysis shows that theDarcy-Weisbach friction factor can be accurately estimated by the proposed theoreticalapproach based on a power-velocity profile.