Wind- and tide-induced currents in the Stagnone Lagoon (Sicily)

The Stagnone is a coastal lagoon located in a natural reserve of about 2200 ha characterized by: shallow water (the mean depth is about 95 cm), two openings connecting the lagoon with the open sea, the northern and the southern mouths, presence of islands within the lagoon, presence of a submerged road connecting the Mothia Island with the coast and submerged seagrasses. In this paper, the results of numerical simulations of the hydrodynamic fields in the Stagnone lagoon are compared with experimental measurements of velocities and water levels, carried out in several points using an electromagnetic velocimeter (2D) and two ultrasound ADV sensor (3D). The comparison shows the ability of the code to capture the hydrodynamic behaviour of shallow water coastal lagoons. The simulations are performed using a three-dimensional non-hydrostatic numerical model based on the finite-volume method to discretize the Reynolds-averaged momentum and mass balance differential equations. The numerical model, which is second-order accurate both in time and space, employs the k-ε model to represent the turbulent Reynolds stresses. In order to analyse the wind and of the tide effects of on the hydrodynamic flow field two set of simulations were performed: 1) the analysis of the contribution of the wind stress acting on the water surface and 2) the tidal motion, dominated by semi-diurnal components with supplementary contributions of the diurnal one. These simulations reveal that the tidal forces dominate in the North-South direction, whereas wind plays a fundamental role in the East-West water currents.