Effect of riparian vegetation on habitat metrics P. Gualtieri M. Abdollahpour C. Gualtieri

channels, velocity magnitude, as well as spatial velocity gradient, are among the main drivers of aquatic organism motion, mainly related to feeding, reproduction and searching for optimal environmental conditions. Such hydrodynamic heterogeneity can be described with habitat metrics based on velocity gradients as M1 and M2, that quantifying local changes in kinetic energy, approximate the energy expended by fish and all other aquatic organisms to move from one point to another within the flow. Riparian lands and their vegetation, recognized as areas of high biodiversity, are characterized by a strong shear developing at the interface between two approximately parallel streams of different velocities, such as the main channel and the vegetated zone. In this study, the effect of riparian vegetation density on the above metrics was experimentally investigated. Riparian plants were modeled with rigid cylinders arranged in different streamwise and spanwise spacing distances. It was found that, vegetation density significantly affects the metrics M1 and M2 in the channel cross-section, with peak values in the shear layer, while the lower values observed in the vegetated zone, can allow aquatic organisms to exploit a water volume for feeding, resting, refugee, and reproduction.