Abstract:
In the framework of a research project entitled “BERNA”, a methodology was devised to characterize the wind
waves at the Alfeite beach, in the inner estuary of the Tagus river, by making in-situ measurements and using a
numerical wave propagation model. With this goal in mind, a number of in-situ measurements were made, for a
few selected positions in front of the Alfeite beach, at three different days, using resistive wave gauges and
pressure transducers. During this period, a number of wave records, with different durations, were obtained and
analyzed. Although these measurements proved to be useful to give a good insight of the main characteristics of
the wind waves that might occur at that particular location, they cannot give a general characterization of the
wind wave climate on the Tagus estuary, especially at the Alfeite beach, since they are in a small number and are
limited to a few positions only. To overcome these shortcomings, the SWAN numerical model was used to
account for the wave generation, propagation, attenuation and non linear interactions between waves and
currents phenomena in the whole estuary, in particular in the Alfeite beach. In this way, the model is applied to
the same conditions of wind and tide observed on the measurement days. This paper summarizes the wave
characterization work performed under the BERNA project. A comparison of the SWAN results to the wave
parameters from wave records obtained in front of Alfeite beach is made and discussed.
