Natural streams commonly feature a compound channel characterized by main channels and floodplains. During flood events, sediment and particulate organic matter deposition in floodplains promotes vegetation growth, influencing river hydrodynamics and ecosystems. Current hydrodynamics investigations frequently employ arbitrary vegetation characteristics, potentially misrepresenting natural conditions. This study experimentally explores compound-channel flows in which the floodplain is occupied with natural vegetation characteristics sourced from the Upper Rhine, including both young and mature plants. A 30 m long, 5 m wide asymmetrical compound channel with a 0.5‰ longitudinal slope was used. Two flow conditions, deep and intermediary flow, were tested. Velocity and depth data were collected under simulated flow conditions corresponding to a 15 to 20-year return period. Vegetation accentuated the shear between the floodplain and the main channel, compared to non-vegetated conditions. Furthermore, vegetation effects on water depth were observed downstream the patch until 1.75 times the vegetation patch length.
