Revista de Gestão Costeira Integrada
Volume 11, Número 3, Setembro 2011, Páginas 283-296

DOI: 10.5894/rgci269
Submissao: 22 Março 2011; Avaliacao: 10 Maio 2011; Recepcao da versao revista: 8 Julho 2011; Aceitacao: 24 Agosto 2011; Disponibilizacao on-line: 8 Setembro 2011
Artigo decorrente da comunicação efectuada no MEC 2011 - Conferência sobre Morfodinâmica Estuarina e Costeira, 3 a 4 de Fevereiro de 2011, Lisboa, Portugal

Análise comparativa entre estimativas do modelo SWAN e medições de agitação marítima efectuadas na Praia da Amoreira, Portugal

Comparative analysis between SWAN’s numerical estimates and sea wave measurements made at the Amoreira’s Beach, Portugal

Rui Capitão ^{@, 1}, Conceição Fortes ¹

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@ - Autor correspondente
1 - Laboratório Nacional de Engenharia Civil, LNEC, Departamento de Hidráulica e Ambiente, Núcleo de Portos e Estruturas Marítimas, Av. do Brasil, 101, 1700-066 Lisboa, Portugal..
e-mails: [email protected], [email protected]

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RESUMO
Neste trabalho, analisa-se o desempenho do modelo numérico SWAN (Booij et al., 1999) na caracterização da agitação marítima na zona costeira da praia da Amoreira, em Aljezur, Algarve. Para este efeito, efectua-se uma análise comparativa entre as medições de agitação marítima realizadas na Praia da Amoreira e as estimativas produzidas por esse modelo. Assim, partindo dos resultados do modelo regional de previsão da agitação marítima, WAVEWATCH III, Tolman (1999, 2002), para os dias em que foram realizadas as medições in-situ, efectuaram-se cálculos com o modelo SWAN, obtendo-se nos locais de medição valores de altura significativa, período de pico e período médio. A comparação das simulações numéricas com os dados medidos permitiu avaliar o desempenho do modelo numérico e reforçar a confiança que já existia neste modelo na sua utilização em estudos de morfodinâmica e dinâmica costeira.

Palavras-chave: Ribeira de Aljezur (Portugal), Medições in-situ, Modelação numérica, SWAN

 

ABSTRACT
The understanding of hydrodynamics, morphodynamics and fecal contamination of intermittent coastal streams encompasses an interdisciplinary study that integrates three different methodologies, although complementary: acquisition of field data, laboratory investigation and numerical modeling. The results of this methodology in the study area, the Ribeira de Aljezur, will enable the assessment of the relative importance of various forcings on the morphology of the system and its impact on the water quality of generic coastal streams.
In this work a sea wave characterization is made on the intermittent-type Aljezur stream, Algarve, Portugal, to understand the hydrodynamics, morphodynamics and fecal contamination effects, as well as its impact both on the water quality and on the evolution of the bottom and of the water exchanges in the region under study. Thus, in-situ measurements of sea waves were made using pressure transducers at points near the mouth of the river and on the Amoreira’s Beach, at the mouth of Aljezur stream. Numerical modeling was also employed to obtain a spatial characterization of the study area, through the use of SWAN numerical model (Booij et al., 1999). This model enables sea-wave generation, propagation and dissipation based on the wave action balance equation and is used to propagate sea waves from offshore up to the shoreline, taking into account the major physical processes of wave refraction, diffraction and shoaling due to bottom depth variation and to the presence of currents. It also includes wind induced wave growth, wave breaking due to bottom variation and to whitecapping, energy dissipation by bottom friction, wave blocking and reflection by opposing currents as well as wave transmission.
In order to evaluate the performance of this numerical model to characterize the sea waves at this beach, and to get even more confidence on this well-known model, currently used in many studies of coastal morphodynamics and long-term dynamics, a comparative analysis between measurements of sea waves made at Amoreira beach and the estimates produced by this model was performed. Thus, based on the results of the regional model prediction of sea waves, WAVEWATCH III, Tolman (1999, 2002), and for the days where in-situ measurements were taken, calculations were made ​​with the SWAN model, resulting in significant wave heights​​, peak periods and mean periods for an area adjacent to the Amoreira beach, where those measurements were taken. A comparison of numerical simulations with the measured data allowed the evaluation of the behavior of the numerical model to simulate the propagation of sea waves on the beach.
In this work, the measurement campaigns, the analysis of the data obtained at the measuring campaigns and the application made with SWAN model to characterize the wave field generated by the wind at the study area were described and a comparison of numerical simulations with the in-situ measured data allowed the evaluation of the performance of the SWAN model for this location, guaranteeing even more confidence in its use in studies of morphodynamics and coastal dynamics.

Keywords: Ribeira de Aljezur (Portugal), in-situ measurements, Numerical modeling, SWAN

 

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