Stream-scale experiment and numerical modelling for vegetated flows

Vegetation roughness has been an important topic for several decades because of the effects vegetation can have on water conveyance. Since most of Korean and Dutch rivers are regulated a good understanding of the potential impact of vegetation dynamics on river hydraulics can help to improve long term planning of river management. Parameters related to river vegetation roughness are expected to affect river processes hydraulically, morphologically, environmentally or ecologically. There is a need to further investigate their effects or relationships so as to help physical understanding and be used for better prediction. This study experimentally and numerically investigated the effects of vegetation patches on the flow characteristics and morphological changes in a large-scale outdoor experimental channel with rooted willows. Stream-scale experiments on vegetated flows were performed for partially submerged condition of vegetation arranged by alternative bar formation. Three-dimensional flow structure was measured by ADV (Acoustic Doppler Velocimeter) and ADCP (Acoustic Doppler Current Profiler). Vertical, cross-sectional, and longitudinal velocity distributions were analyzed. Also, flow velocities and bed changes measured from stream-scale experiment were used to calibrate and validate Delft3D model for flow and bed change simulations.