Interaction of vegetation and bedforms plays an important role on main flow components including velocity, shear stress and turbulence intension. The objective of present research is to investigate this interaction over flat-crest dunes with and without vegetated banks experiments were conducted in two sections: laboratory and field. In laboratory section 88 velocity profile were measured over flat-crest dunes with vegetated and bare banks. In field section, 17 velocity profile were taken in a gravel-bed river, Babolroud, located in north in Iran. The results shows that the velocity distribution are similar the shor-crest dunes and vegetated banks play an important role on location of maximum velocity in each profile. The peak value of Reynolds stress and turbulence intention occur at the lee zone and 4 cm for from the vegetated banks. Considerable variations of local velocity and turbulent flow components lead to apply double-averaged method to calculate shear velocity and roughness coefficient in average, 75 percent of total roughness coefficient is due to bedform roughness, showing considerable influence of dune on the roughness coefficient estimation. The results of this research can be used in hydraulic models Keywords: Flat-crest dunes, Roughness coefficient, Double-averaged method, Vegetated banks