3D hydrodynamic characterisation of a meso-tidal harbour: The case of Bilbao (northern Spain)

A background knowledge of marine dynamics helps harbour managers to control pollution and to manage dredging and traffic operations. This contribution studies the hydrodynamic conditions within Bilbao Harbour, which is enclosed by the Nervión Estuary (in the Basque Country, Spain). The results obtained from hydrographical surveys are compared with numerical simulations obtained using the Regional Ocean Modelling System (ROMS). Hydrodynamic modelling was carried out to determine the inner harbour currents for a specific period in which data were available. Then, numerical experiments were designed in order to quantify the importance of different driving mechanisms in the harbour hydrodynamics. The results show that, in addition to the strong tidal influence on water circulation, the wind forcing and freshwater discharge also have a non-negligible influence on the currents. The computational domain is complex due to the presence of harbour infrastructures (i.e. breakwaters and piers). As a result, topographic eddies are therefore observed in the results. The freshwater influence of the Nervión river can also be observed in residual currents. This paper presents an improvement to the application of numerical modelling to a complex geometry domain, contributing to our understanding of the behaviour of the marine systems in meso-tidal harbours. This can be used to deal with harbour engineering and management problems.