This paper describes a theoretical approach of longitudinal turbulent flow in an infinite square array of emergent rigid vegetation distributed uniformly along a channel bottom. Laboratory experiments were carried out to investigate the flow velocity characteristics in order to confirm this theoretical approach. The vegetation was simulated by an array of straight, rigid, circular and rough iron cylinders mounted on the bed of a recirculating hydraulic flume. Measurements of the threedimensional flow velocity components were taken using a 3D Acoustic Doppler Velocimeter ADV. The formulation proposed is consistent with the experimental data for a specific range of the Reynolds number. In addition, a new formula to estimate the bulk drag coefficient CD of the vegetation is suggested and validated.