Velocity uncertainty quantification based on Riparian vegetation indices in open channels colonized by Phragmites australis

Abstract One of the main purposes of Ecohydraulics is to predict the effects of riparian vegetation on aquatic ecosystems within real water channels. The interaction between water flow and riparian plants significantly affects flow dynamics, hydraulic conveyance, and water quality of vegetated water bodies. This study aimed at quantifying analytically the uncertainty in flow average velocity estimations associated with the uncertainty of Leaf Area Index (LAI) of Phragmites australis (Cav.) Trin. ex Steudel covering a vegetated channel. The impacts of this species on the hydrodynamics of vegetated streams are far to be completely understood. The uncertainty in flow average velocity was assessed through the first-order second-moment statistical method, by comparing direct and indirect LAI measurements of mature Phragmites australis plants. Indirect LAI values were obtained using the LICOR® LAI-2000 Plant Canopy Analyzer device. The results of this study suggest that the uncertainties in flow average velocity estimations are comparable to those associated with experimental measurements of streamwise velocity components retrieved in real vegetated flows fully covered by mature Phragmites australis plants.