Vegetation altering hydrodynamic conditions of an open channel flow controls the exchanges of sediment, nutrients and contaminants. Thus, the knowledge of the hydraulic characteristics of flow over vegetation is very important to support the management of fluvial processes. In this paper the flow over real flexible vegetation is experimentally studied. A 2D-ADV (Acoustic Doppler Velocimeter) is used to measure the local flow velocities for different vegetation concentrations and varying the discharge and the flume slope. The flow velocity measures are used to test the hyperbolic tangent profile of a pure mixing layer and to evaluate the mixing-layer parameters. The formation of turbulence structures inside the vegetated layer is verified through spectral analysis.