Hydraulic Modeling of Field Experiments in a Drainage Channel Under Different Riparian Vegetation Scenarios

A hydraulic model was implemented for interpreting the real-scale hydraulic tests conducted in a vegetated drainage channel, colonized by dormant Phragmites australis (Cav.) Trin. ex Steud. (common reed), located in the San Rossore-Migliarino-Massaciuccoli Regional Park (Tuscany, Italy). The hydraulic tests encompassed six flow rates and three vegetation scenarios: (a) natural scenario, with common reed fully covering the drainage channel; (b) side vegetation scenario, achieved by removing the in-stream reed just in the central portion of the channel, with two lateral buffers of undisturbed vegetation and (c) unvegetated scenario, corresponding to the complete removal of the riparian reed plants. The outputs of the simulation were compared with the experimental flow average velocities and vegetative Manning’s roughness coefficient, obtained from measured punctual flow velocities by means of an acoustic Doppler velocimeter (ADV) and a propeller-type current meter, respectively located at the upstream and downstream cross sections of the experimental stretch of the drainage channel. The results of this study are discussed for assessing the impact of the vegetation management scenarios on both hydraulic conveyance and riparian habitat functionality of the examined vegetated drainage channel.