Vegetation has a paramount impact on water flow resistance and water quality in vegetated open channels. Defining the most appropriate management practice of riparian vegetation inside both natural and manmade water bodies is crucial for assuring a balance between a satisfactory level of hydraulic and hydrodynamic conveyance and a high environmental value of water resources. The presence of riparian vegetation significantly affects both mean and turbulent water flow fields, with important implications on oxygen production and transport of nutrients within vegetated open channels. Experimental analysis and modeling were performed in the present study, aiming at providing an additional understanding of the hydrodynamic interaction between riparian vegetation and water flow at field scale in an Italian abandoned reclamation channel colonized by rigid and emergent plants of Phragmites australis (Cav.) Trin. ex Steud., also known as Common reed. The calibration of predictive models of flow resistance in vegetated water bodies was performed by employing Unmanned Aerial Vehicle (UAV)-multispectral acquired images, from which it was feasible to cover the whole water bodies and to correlate ground-based and UIAV-derived Leaf Area Index (LAI) estimations. The outcomes of this study represent a useful tool for land managers and environmental engineers when dealing with riparian vegetation management at different temporal and spatial scales.