In this paper, a technique for establishing the boundary shear stress distribution in open channel flows is proposed and used. The boundary shear stress along the wetted perimeter of a large river cross-section was estimated from repeated Doppler profiler (aDcp) campaigns conducted for a range of flow conditions. Experimental vertical velocity profiles were extracted from 18 series of aDcp discharge measurements performed in the Saône river at the Saint-Georges gauging station in Lyon, France. Post-processing methods for aDcp data positioning, averaging and depth-integrating were implemented and applied to each of the 18 aDcp series, in order to establish 23 mean vertical velocity profiles across the 96 m-wide, 10 m-deep cross-section. An average non-dimensional profile was computed from the resulting 414 velocity profiles. It was found that the lowest 70% part of this unit profile can be represented accurately by a log law with a zero-velocity shift (or roughness height) of z0 = 4-5 mm approximately. This value corresponds to a 50 mm medium grain size for the bed material, which seems consistent with the in-situ observation. Consequently each experimental profile was regressed individually against a log-law, below a maximum relative elevation ζc=0.7 only, and assuming the mean value for z0 (4.6 mm). For each campaign, the mean shear stress and the boundary shear stress distribution along the wetted perimeter were estimated. The mean shear stress was also computed using an energy slope estimate stemming from the Manning-Strickler formula, in which the mean velocity and hydraulic radius were calculated using the aDcp measurements. The resulting mean Manning coefficient was n = 0.026 m-1/3.s. The sensitivity of the experimental results to the regression parameters (z0, ζc) was tested and discussed.