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Abstract(s)
A vídeo-monitorização tem-se revelado uma técnica de grande utilidade em estudos da morfodinâmica de praias. No entanto, a maior parte dos sistemas desenvolvidos depende da existência de uma infraestrutura própria que exige custos de operação e manutenção elevados. Uma potencial alternativa consiste na utilização da rede surfcams que se encontra instalada num elevado número de praias. Este trabalho teve como objetivo desenvolver técnicas que permitam otimizar a utilização de imagens provenientes das surfcams em estudos de morfodinâmica costeira. O processamento destas imagens apresenta desafios técnicos adicionais relativamente aos sistemas de vídeo-monitorização dedicados uma vez que a localização e características de aquisição de imagem são otimizadas para fornecer uma perspetiva qualitativa da rebentação para a prática do surf. Este trabalho enquadrou-se no âmbito do protocolo estabelecido entre a Agência Portuguesa do Ambiente (APA), a Universidade de Aveiro (UA) e a MEO Beachcam, que tem por objetivo adquirir e processar informações provenientes das imagens de duas câmaras MEO Beachcam, em locais particularmente sensíveis a processos de erosão costeira e galgamento, casos de estudo das praias do Furadouro e da Costa Nova. Nesta dissertação foram definidos procedimentos para a aquisição de dados provenientes dos sistemas de vídeo-monitorização, com vista à monitorização da hidrodinâmica e morfologia das praias, que associam fenómenos de erosão e acreção da praia, assim como os processos de galgamentos de estruturas. Foram também analisadas as capacidades e limitações dos métodos de aquisição com vista à geração de produtos standard para o propósito do estudo: geração de imagens Timex, Variância e Timestack. Complementarmente foi executado um programa de monitorização que incluiu levantamentos de perfis topográficos mensais por GPS nos dois locais de estudo. A base de dados de registo topográfico em conjugação com a informação hidro-morfológica obtida a partir dos perfis Timestack, permitiu estabelecer relações entre os parâmetros de agitação marítima, em situações de temporal, quantificar o runup associado e monitorizar o número de galgamentos em estruturas de proteção costeira e em defesas naturais. Neste contexto, foram criadas técnicas de observação (estimativa da largura de praia, a quantificação de galgamentos e a estimativa da distância/profundidade a que ocorre a rebentação) e através destas e da exportação desses indicadores, foram criadas duas técnicas (metodologia 1 – previsão de runup baseado no sistema de vídeo; metodologia 2 – previsão de runup baseado nos dados de campo) para cálculo da cota de runup e dar apoio à previsão de galgamentos. Com o algoritmo desenvolvido para quantificar o número de eventos de galgamentos através das imagens timestack, registaram-se estes eventos nos dias 28, 29 e 30 de outubro de 2020, nos dias 4, 12, 14 e 16 de dezembro de 2020, 1 de março e nos dias 24 e 25 de abril de 2021, havendo para alguns, dados de ocorrências registadas pela APA e coerência com o cálculo da cota de runup nos dias 28 e 29 de outubro; 4, 5, 12, 13, 14, 15 e 16 de dezembro e 1 de março de 2021. Com este trabalho, apresenta-se a primeira iteração tecnológica para construção de um modelo de previsão de galgamentos com base na infraestrutura das surfcams.
Video monitoring has proved to be a very useful technique in studies of beach morphodynamics. However, most of systems developed depend of its own infrastructure that requires high operating and maintenance costs. A potential alternative consists in using the network surfcams that is installed in a large number of beaches. This work aims to develop techniques for the use of images from surfcams in studies of coastal morphodynamics. The processing of these images presents additional technical challenges compared to dedicated video monitoring systems as their location and image acquisition characteristics are optimized to provide a qualitative view of the break wave location for surfing. This work was framed within the scope of the protocol established between the Portuguese Environment Agency, the University of Aveiro and MEO Beachcam, it is intended to acquire and process information from the images of two MEO Beachcam cameras, in places particularly sensitive to coastal erosion and overtopping processes, case studies of Furadouro and Costa Nova beaches, Aveiro District. Procedures were defined for the acquisition of data from the video-monitoring systems, with a view to monitoring the hydrodynamics and morphology of the beaches that lead to the erosion and accretion of the beach and its influence on structures overtopping, as well as the analysis of capacities and limitations of the acquisition methods regarding the generation of standard products for the purpose of the study: generation of Timex, Variance and Timestack images. In addition, a monitoring program was carried out, which included monthly surveys of GPS topographic profiles in the two study sites. The topographic data together with the hydro-morphological information obtained from the timestack profiles, allowed to establish relationships between the parameters of wave regime during storms, to quantify the associated runup and to measure the number of overtopping occurrences in structures of coastal protection and in natural defenses. In this context, techniques were created for exporting the indicators (beach width estimation, quantification of overtopping and estimation of wave breaking distance/depth), as well as two techniques to calculate the runup and support the prediction of overtopping (methodology 1 - extraction of indicators through videos and methodology 2 – extraction of indicators through field data). With the algorithm developed to quantify the number of overtopping through timestack images, these events were recorded on October 28, 29 and 30, on December 4, 12, 14 and 16, 2020, 1st of March and on April 24 and 25, 2021. Some occurrences registered by the APA and consistency with the calculation of the runup on October 28 and 29; December 4, 5, 12, 13, 14, 15 and 16 and March 1, 2021. With this work, we present the first simple technological iteration to build an overtopping prediction model more adjusted to reality.
Video monitoring has proved to be a very useful technique in studies of beach morphodynamics. However, most of systems developed depend of its own infrastructure that requires high operating and maintenance costs. A potential alternative consists in using the network surfcams that is installed in a large number of beaches. This work aims to develop techniques for the use of images from surfcams in studies of coastal morphodynamics. The processing of these images presents additional technical challenges compared to dedicated video monitoring systems as their location and image acquisition characteristics are optimized to provide a qualitative view of the break wave location for surfing. This work was framed within the scope of the protocol established between the Portuguese Environment Agency, the University of Aveiro and MEO Beachcam, it is intended to acquire and process information from the images of two MEO Beachcam cameras, in places particularly sensitive to coastal erosion and overtopping processes, case studies of Furadouro and Costa Nova beaches, Aveiro District. Procedures were defined for the acquisition of data from the video-monitoring systems, with a view to monitoring the hydrodynamics and morphology of the beaches that lead to the erosion and accretion of the beach and its influence on structures overtopping, as well as the analysis of capacities and limitations of the acquisition methods regarding the generation of standard products for the purpose of the study: generation of Timex, Variance and Timestack images. In addition, a monitoring program was carried out, which included monthly surveys of GPS topographic profiles in the two study sites. The topographic data together with the hydro-morphological information obtained from the timestack profiles, allowed to establish relationships between the parameters of wave regime during storms, to quantify the associated runup and to measure the number of overtopping occurrences in structures of coastal protection and in natural defenses. In this context, techniques were created for exporting the indicators (beach width estimation, quantification of overtopping and estimation of wave breaking distance/depth), as well as two techniques to calculate the runup and support the prediction of overtopping (methodology 1 - extraction of indicators through videos and methodology 2 – extraction of indicators through field data). With the algorithm developed to quantify the number of overtopping through timestack images, these events were recorded on October 28, 29 and 30, on December 4, 12, 14 and 16, 2020, 1st of March and on April 24 and 25, 2021. Some occurrences registered by the APA and consistency with the calculation of the runup on October 28 and 29; December 4, 5, 12, 13, 14, 15 and 16 and March 1, 2021. With this work, we present the first simple technological iteration to build an overtopping prediction model more adjusted to reality.
Description
Tese de Mestrado, Geologia do Ambiente, Riscos Geológicos e Ordenamento do Território, 2022, Universidade de Lisboa, Faculdade de Ciências
Keywords
Vídeo-monitorização Surfcams Morfodinâmica costeira Galgamento Cota de runup Largura de praia Costa Praia Teses de mestrado - 2022