Aquatic plants are critical components of many aquatic ecosystems. A large-scale coherent vortex is generated near the vegetation edge, which dominates the momentum and scalar transport. Thus, estimating the flow resistance of vegetation is of great importance for engineering and ecological applications. Interactions between flow and vegetation are complex and depend on environmental factors and plant characteristics such as plant flexibility, size and vegetation density. Therefore, in the present study, turbulence measurements were conducted for rigid and flexible vegetation flows by using PIV technique. As the results, the characterization of flow resistance due to flexible vegetation roughness was examined for different plant heights.