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The analysis and the prediction of the effects of the hydrodynamic interaction between water flow and riparian vegetation in natural and manmade vegetated water bodies are the main objectives of Ecohydraulics. Riparian vegetation has a paramount impact on both 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 conveyance and a high environmental value of water. 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 this thesis, to provide additional understanding of the hydrodynamic interaction between riparian vegetation and water flow at field scale in an abandoned reclamation channel colonized by rigid and emergent plants of Phragmites australis (Cav.) Trin. ex Steud., also known as Common reed. Different riparian vegetation management scenarios were evaluated: undisturbed conditions, partial riparian vegetation cover and total riparian vegetation removal. Field hydraulic tests were carried out for investigating the experimental cross sectional distributions of streamwise velocity and main turbulence features (Reynolds stresses and Turbulent Kinetic Energy). The outcomes of the experimental activities were employed for modeling the flow resistance of the examined vegetated reclamation channel by employing both 1D numerical simulations and literature models, which accuracies were assessed by comparing experimental and modeled vegetative global water flow resistance coefficients. In the case of partial riparian vegetation cover, a methodology based on the detailed analysis of the experimental cross sectional streamwise velocity distribution was proposed. This methodology provides estimates of global water flow resistance with prediction errors smaller than the direct application of the examined models. In the last part of the doctoral research program, the feasibility of Digital Hemispherical Photography (DHP) technology was evaluated for assessing Leaf Area Index (LAI) of mature Common reed plants to be exploited for flow resistance modeling of vegetated streams. The uncertainty of DHP-derived LAI was evaluated from a functional perspective, by estimating its impact on the uniform water flow velocity predicted with Västilä & Järvelä model. DHP proved to be a reliable technology for ecohydraulic modeling at field scale.

This work presents the results of experimental activities carried out during a 3-years research program, to assess the effects of infesting reed beds on the mean and turbulent hydrodynamic features of vegetated reclamation channels at field scale. The devices and methodologies employed in the experiments represent an innovation in the study of vegetative flow resistance directly at field. Different management scenarios of the vegetated cover were evaluated, with the aim to assess the optimal strategy for balancing the need for an effective hydraulic conveyance and the need to preserve the environmental quality of the vegetated water bodies.

Drainage channels are a widespread component of agricultural and urbanized lowland landscapes. Management of instream and riparian vegetation along drainage channels must be planned by reconciling the need to ensure channel hydraulic efficiency with the need to preserve the riparian habitat. The present paper reports the experimental results of a study conducted on a drainage channel colonized by Phragmites australis in undisturbed natural conditions. The impacts of common reed on flow resistance, flow velocity distribution and turbulence parameters were examined with different discharges under three different scenarios of channel vegetation, which were obtained by means of machineries traditionally used in land reclamation areas. Removing either totally or partially the channel vegetation had great effects on streamwise velocity distribution and turbulence patterns, with small differences in global flow resistance. The experimental results suggest that clearing the channel vegetation just in the center of the cross section can improve the channel conveyance to values close to those obtained with the total removal of the vegetation, while maintaining relatively high levels of turbulent intensities.