Bedload roughness is the roughness produced by sediment transported near the bed. While it is well established that the magnitude of this roughness is proportional to the thickness of the moving sediment layer, the eect of sediment concentration remains largely unknown. This paper presents the results of a ยฏume experiment that was designed to investigate the eect of sediment concentration on bedload roughness. The experiment consisted of creating ยฏow conditions where bedload transport is supply-limited and injecting gravel size particles (D 50 7.4 mm) at the upstream end of the ยฏume in order to produce bedload transport. While keeping ยฏow conditions constant, sediment concentration was varied by successively increasing the injection rate of gravel in the ยฏow. For each injection rate, ยฏow velocity proยฎles were measured in order to evaluate changes of mean ยฏow velocity U, shear velocity u * , roughness length z o and resistance to ยฏow f. The results indicate that low sediment concentration aects mainly the near bed portion of the ยฏow where it causes a reduction of mean ยฏow velocity and an increase of shear velocity and roughness length. For larger sediment concentration, the whole ยฏow velocity proยฎle becomes aected by bedload roughness but the importance of this eect always remain larger near the bed. As sediment concentration is augmented, mean ยฏow velocity is consistently reduced but shear velocity and roughness length increase until a plateau is reached where these two variables become constant.