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Avaliação da profundidade de fecho ao longo do litoral de Portugal Continental
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Resumo(s)
A profundidade de fecho corresponde à profundidade a partir da qual o perfil de praia
não sofre modificações morfológicas significativas. Este é um conceito fundamental para
definir a extensão da praia submarina, com relevância para um conjunto alargado de tópicos
que interessam para a gestão costeira. No entanto, na maior parte dos casos, esta profundidade
é calculada unicamente através de fórmulas empíricas a partir do conhecimento da altura
significativa e o período das ondas, havendo poucos trabalhos baseados em dados de campo e
geralmente representativos de um único local.
O objetivo deste estágio foi avaliar a profundidade de fecho ao longo do litoral
de Portugal continental, com base nos dados recentemente adquiridos no âmbito Programa de
Monitorização da Faixa Costeira de Portugal Continental – COSMO relativos aos anos de
2018 a 2021. Para cumprir este objetivo foi desenvolvido um método de análise automático
(em linguagem de programação Python) baseado no cálculo adimensional da variabilidade
morfológica ao longo do perfil. Foi ainda calculada a profundidade de fecho através de três
equações empíricas e posteriormente comparadas com os valores experimentais.
A profundidade de fecho experimental calculada ao longo da costa ocidental de
Portugal foi cerca de 11 m (NMM) enquanto no Algarve foi de cerca de 6m (NMM). De entre
as fórmulas empíricas analisadas para o cálculo da profundidade de fecho, a de Birkemeier
demonstrou ser a mais adequada em comparação com os dados de campo analisados.
Aos valores apresentados têm as limitações inerentes à quantidade e qualidade
dos dados disponíveis, um problema que tem especial acuidade no Algarve onde o reduzido
número de perfis e o facto de estes serem geralmente adquiridos no verão poderá levar à
subestimação da profundidade de fecho obtida no âmbito deste trabalho.
The depth of closure, which represents the point beyond which the beach profile experiences minimal morphological changes, is a crucial concept in defining the underwater beach extent, with direct implications for coastal management. Despite its significance, the depth of closure is often determined using empirical formulas based solely on knowledge of wave height and period, with limited studies relying on field data, usually from a single site. This internship aimed to evaluate the depth of closure along the coast of mainland Portugal, utilizing recent data obtained through the Coastal Strip of Continental Portugal Monitoring Program (COSMO) spanning from 2018 to 2021. An automated analysis method was developed using the Python programming language, employing a dimensionless calculation of morphological variability along the profile. Three empirical equations were applied to calculate the closing depth, and the results were compared with experimental values. The experimental closure depth calculated along the western coast of Portugal was approximately 11 m (NMM), while in the Algarve region, it was approximately 6 m (NMM). Among the empirical formulas analyzed for calculating the closing depth, Birkemeier's formula was found to be the most appropriate when compared with the field data. The results obtained during the study are valuable; however, they are subject to the inherent limitations arising from the quantity and quality of available data. Notably, the Algarve region faced particular challenges due to the limited number of profiles available, which were primarily acquired during the summer months. Consequently, this may have led to an underestimation of the closing depth obtained in the scope of this work.
The depth of closure, which represents the point beyond which the beach profile experiences minimal morphological changes, is a crucial concept in defining the underwater beach extent, with direct implications for coastal management. Despite its significance, the depth of closure is often determined using empirical formulas based solely on knowledge of wave height and period, with limited studies relying on field data, usually from a single site. This internship aimed to evaluate the depth of closure along the coast of mainland Portugal, utilizing recent data obtained through the Coastal Strip of Continental Portugal Monitoring Program (COSMO) spanning from 2018 to 2021. An automated analysis method was developed using the Python programming language, employing a dimensionless calculation of morphological variability along the profile. Three empirical equations were applied to calculate the closing depth, and the results were compared with experimental values. The experimental closure depth calculated along the western coast of Portugal was approximately 11 m (NMM), while in the Algarve region, it was approximately 6 m (NMM). Among the empirical formulas analyzed for calculating the closing depth, Birkemeier's formula was found to be the most appropriate when compared with the field data. The results obtained during the study are valuable; however, they are subject to the inherent limitations arising from the quantity and quality of available data. Notably, the Algarve region faced particular challenges due to the limited number of profiles available, which were primarily acquired during the summer months. Consequently, this may have led to an underestimation of the closing depth obtained in the scope of this work.
Descrição
Relatório de Estágio de Mestrado, Geologia do Ambiente, Riscos Geológicos e Ordenamento do Território, 2024, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Limite oceânico da praia submarina COSMO Agitação marítima Perfis Formulações empíricas Teses de mestrado - 2024