Aquatic vegetation frequently determines the mean and turbulent flow structure in natural river and impacts the transport of sediment and nutrients. These vegetation communities are often observed to grow in stripe pattern or patches within main stream channel. In this paper, the influence that interaction of longitudinal vegetation zones gave the momentum transport and coherent vortex generation in an open-channel was examined experimentally. Laboratory experiments were conducted using a two-component electromagnetic current-meter and a Particle-Image-Velocimetry (PIV). Results showed that horizontal large scale vortex generation significantly depended on the lateral distance between longitudinal vegetation zones and these vortices controls the momentum transport through the interaction.