A comprehensive study of the river plume in a microtidal setting

We performed a comprehensive study of the generation and transport mechanisms of a river plume flowing into a microtidal environment. First, we analysed images simultaneously acquired by both two shore-based stations and satellite and correlated the plume offshore extension with the estuarine forcing. Furthermore, we run numerical simulations to reproduce real-life events, characterized by a combination of forces, and to distinguish the role of each forcing. We identified the river discharge and the wind as the main generation and transport mechanisms, respectively. Moreover, waves were able to both generate and drag plumes. Results showed that a river discharge associated with a return period of 1 year produced a denser plume than 10-years return period waves. The transport mechanisms were responsible for the alongshore extension of the plume and consequent potential nourishment of the beaches. The tide, even if secondarily, could affect the plume evolution, depending on its phase shift with respect to the river discharge peak. Finally, we used Particle Tracking Velocimetry on videos acquired by a shore-based station to obtain the surface velocity field in the final river stretch. Such velocity was then modified to consider the effect of wind and waves, so that it could be correlated with the plume extension. The relation between the along-river component of the plume velocity and the plume extension followed a linear law with angular coefficient inversely proportional to the alongshore component of the plume velocity.