Seiche-forced resuspension events in a Mediterranean harbour

The variability of suspended sediments in a Mediterranean harbour was studied using high-frequency moored instruments. Data analysis revealed that the fundamental mode of oscillation or seiche is the main contribution to the sea level variability and currents. Yet a direct relation between the seiche and suspended sediment was not clear. To study the sediment dynamics, a coupled hydrodynamic-sediment one-dimensional vertical model for sand and non-cohesive mud was implemented. Results showed good agreement between most of the observed and simulated resuspension events. Indeed, the vertical extension and the duration of these events were satisfactorily simulated for mud class. Model simulations were used to determine the time delay between suspended sediment and currents, which improved the correlation between the seiche and suspended sediment to some degree. Scarce events of sediment advection from outside waters and fresh water discharges from land-based sources were identified. It is suggested that phytoplankton species detected in the harbour were responsible for discrepancies between observations and simulations.