Factors influencing the spreading of a low-discharge river plume

Coastal plumes resulting from the continuous discharge of brackish or fresh river water are common features of continental and shelf seas. They are important for several aspects of the coastal environment, and can influence the local socio-economy to some degree. It is known from many studies that the evolution of plumes depends on various factors, such as the local bathymetry, hydrodynamics and meteorological conditions; most of these works; however, have focused on medium to large-scale rivers, while the smaller-scale discharges commonly found in the microtidal environments of the Mediterranean Sea have been less studied. This paper is centred on the behaviour of a freshwater plume arising from one of such outflows, in terms of both the physical configuration of the waterbody and the characteristics of the main driving mechanisms (discharge rate and wind stress). The modelled cases correspond to an open shallow bay, limited at one end by a large headland, and into which a typical Mediterranean waterway discharges. This particular setup is representative of a number of different bays existing on the Eastern Spanish coast. The numerical results highlight the large influence of the bay's topography on the river plume's extension and inner structure.