In this methodology, a key
element is to get hydrodynamic forecasts. Thus, the system is composed of a hierarchy of nested
hydrodynamic models covering from the basin scale to the harbour scale and a module that computes the
different parameters needed for risk assessment. Special emphasis is made on describing the steps followed
for system implementation because such implementation is far from a mere technical problem. The first step
is to identify the main forcing factors for the harbour hydrodynamics from both field data and numerical
experiments, which has never been done before for the Barcelona harbour. Wind and shelf currents are
suggested as the main forcing factors for the harbour circulation. The second step is to identify the
requirements that a numerical model must fulfil in order to properly solve the Barcelona harbour's
hydrodynamics.