Coastal bays as a sink for pollutants and sediment

Water quality in coastal and estuarine areas plays a very important role in both the ecological balance and the closely linked economic profitability and development. However, these areas have been progressively degraded in the last decades due to overexploitation of their natural resources; in semi-enclosed coastal basins, where the circulation is physically limited, particular problems associated to water quality degradation are enhanced, leading to possible eutrophication issues. This is the main aim of this paper, which focuses on coastal bays as traps for water-borne substances. The analysis is based on a comparison between the behavior of the river Júcar's freshwater plume and the plume of the Cullera marine outfall under typical wind conditions. Both plumes evolve within Cullera Bay, whose northern side is bounded by a cape. The obtained and simulated “actual” dynamics are compared to an hypothetical situation in which the cape has been removed. Numerical simulations of wind- and river-induced hydrodynamic fields and pollutant transport have been performed, and the results show that the presence of the cape is significant in determining the fate of the wastewater discharge, whereas the river plume, although affected also by the cape, shows a larger dependence on the wind speed