\textenglish[variant=american]P\textenglish[variant=american]hragmites australis\textenglish[variant=american] is an abundant vegetation species in the Mississippi River Delta (MRD) that is experiencing widespread dieback, which threatens MRD resiliency to coastal erosion and relative sea level rise. The presence and density of P\textenglish[variant=american]hragmites \textenglish[variant=american]regulates the flow of water and sediment between MRD distributary channels and marsh. Quantifying channel-marsh connectivity modulated by \textenglish[variant=american]Phragmites \textenglish[variant=american]at various densities, life stages, spatial scales and seasons increases our ability to forecast the fate of the deltaic systems. Seasonal acoustic Doppler current profiler (ADCP) surveys along South Pass indicate that discharge decreases seaward as water is routed into smaller distributary channels and overbank flow to the marsh platform. To directly observe flow modulation from P\textenglish[variant=american]hragmites \textenglish[variant=american]at the patch scale, a small unoccupied aerial system (sUAS) collected multi-spectral aerial photos of dye propagation near and through patches of P\textenglish[variant=american]hragmites \textenglish[variant=american]of various stem densities.\textenglish[variant=american] \textenglish[variant=american]Using a trained image classification system that compares band ratios to distinguish between water, vegetation, and dye, the reduction in water velocity caused by vegetation was observed and analyzed. Informed by the field observations, a Delft3D hydrodynamic model was developed to test the influence of P\textenglish[variant=american]hragmites \textenglish[variant=american]patch\textenglish[variant=american] \textenglish[variant=american]densit\textenglish[variant=american]y \textenglish[variant=american]on velocity reduction, flow localization, and erosion/deposition. Low density patches cause flow velocity reductions that promote sedimentation within the patch. However, at higher densities, the patch effectively blocks flow through it, leading to flow localization and sedimentation rate reductions. Understanding both seasonal and climatic changes in hydrodynamics caused by P\textenglish[variant=american]hragmites\textenglish[variant=american] \textenglish[variant=american]australis\textenglish[variant=american] will inform ongoing efforts to evaluate the resiliency of the MRD.