Numerical analysis of the impact of morphodynamics on the water quality of a coastal lagoon

Abstract

The morphodynamics of coastal lagoons, and in particular of their inlets, can significantly affect the water quality of these water bodies. The present work explores the coupling of a morphodynamic model (accounting for waves, tides and their interactions) with a water quality model to analyse the evolution of fecal contamination plumes in a highly dynamic lagoon, under morphodynamic and morphostatic conditions. Concentration differences for plumes released in two areas under morphodynamic and morphostatic conditions are significant. Different patterns are observed for releases in areas of short and long residence times, due to the different impact of decay relative to flushing on the reduction of the pollutant's mass. Morphologically dynamic coastal lagoons are also challenging to monitor, as the changes in the bathymetry may alter significantly the pathways of the pollutants. A preliminary strategy for defining a monitoring network in these systems is sought, based on residence times and residual velocities.