Flow-vegetation interactions at the patch scale: spatial flow variation and coupling of flow with macrophyte motion (#105)
Flow-vegetation interactions occur at multiple scales, from the sub organism to the patch mosaic. At the larger scales vegetation such as macrophytes can alter the flow, creating regions of enhanced and reduced bed shear stress. This flow alteration can manifest as deposition of fine sediment in the wake region, scour in lateral regions and potential changes to river morphology. This study focuses on the spatial variation of flow variables around large macrophyte patches in rivers and the coupling of flow with vegetation motion. Flow is quantified by a pair of synchronous Nortek Vectrino+ Acoustic Doppler Velocimeters (ADVs), while macrophyte motion is quantified through a synchronous underwater camera system. Spectral analysis shows distinct frequency regions of turbulence production and dissipation by the macrophyte, while spatial analysis of flow shows significant variation that can regionally enhance erosion or deposition. Turbulent length scales and frequencies are also compared with synchronous measurements of macrophyte motion to couple flow and plant motion. This research to experimentally determine the flow-vegetation interactions for large macrophyte patches is relevant for a wide range of applications, particularly where high macrophyte densities are common, causing alteration to flow and sediment dynamics.