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The TRANSFER and MAR3G methodologies have been applied recently on a number of studies where the definition of wave regimes at locations is sought but no in-situ measured data are available. Those methodologies are based upon wave ray propagation models. However, these basic propagation models may be too simple to employ in more complex site areas. Therefore, in this paper, the implementation of a more complete wave propagation model (SWAN) into TRANSFER methodology is attempted and described. Results on the application of this improved methodology to two selected sites on the Portuguese coast will enable a better evaluation of its advantages and disadvantages to estimate the wave climate. INTRODUCTION The continental Portuguese coastal zone is characterized by a large number of sandy beaches, harbours and coastal works. The study of dynamics and sedimentary equilibrium of these beaches and the design and protection of harbours and coastal works, amongst others, in its vicinity depend significantly on the knowledge of the local sea wave regime characteristics. However, along the largest coast of Portugal, the west coast, only two buoys are at the moment in operation: at Leixões, in the north-western coast and at Sines, in the south-western coast. As a consequence, the design and protection of harbours and coastal works at some site where no wave buoy has been deployed is usually compromised by the lack of wave data. Therefore, there is a need to employ some methodology to make up for this absence of wave data, and consequently to define the wave regime at the desired location.
Wave Forecast At the Tagus Estuary By Using the SWAN Model
Santos, João Alfredo (Laboratório Nacional de Engenharia Civil) | Coli, Alexandre Braga (Laboratório Nacional de Engenharia Civil) | Capitão, Rui (Laboratório Nacional de Engenharia Civil) | Fortes, Conceição Juana (Laboratório Nacional de Engenharia Civil)
The use of the SWAN model to forecast the parameters of wind-generated waves in the Tagus estuary is illustrated in this paper. In addition to sensitivity tests with that model for idealized wind fields and tide levels in the Tagus estuary, the paper contains a brief description of the wind regime close to a beach in the same estuary as well as of the wave characteristics forecast by the SWAN model for the most common weather conditions there. A comparison of the SWAN results to the wave parameters from wave records made in front of the same beach is also presented. INTRODUCTION Between Alcochete and Alfeite, on the left bank of the Tagus estuary, close to Lisbon, Portugal, there are sand beaches that are typically the result of the action of wind waves generated in the estuary. The genesis and the evolution of these beaches were studied by Freire (2003) and by Freire and Andrade (1999). There is a research project going on now - BERNA - that aims at improving the tools for forecasting the medium and short term evolution of this kind of beaches. For this there is the need to know both wind generated sea waves in restricted areas (such as the Tagus estuary) and their propagation across the estuary up to their breaking at beaches. Although, within the scope of that project, it is expected to couple a numerical model for wind wave generation with a numerical model for wave propagation, a first step consisted in checking the possibility of using one model only to solve the whole problem. For this, the numerical model SWAN (Booij et al., 1999) was chosen. This model, which takes into account the wave generation, propagation, attenuation and non linear interactions between waves and currents phenomena, is a model that is usually employed in open coastal regions although not so often in enclosed regions, such as estuaries or lakes.