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Avaliação de vulnerabilidade costeira a tempestades em ilhas barreira, para períodos de retorno multi-paramétricos
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Abstract(s)
O primeiro objetivo deste trabalho consistiu na determinação da vulnerabilidade a colisão e a galgamento das barreiras arenosas em estudo, com base na análise probabilística das ocorrências de máximos anuais de níveis de run-up para períodos de retorno de 5, 10, 25 e 50 anos multi-paramétricos, e para diferentes classes de pendor de face de praia definidas para cada seção de 100 m, ao longo da série temporal de 19 anos. Os regimes de colisão e galgamento foram obtidos através de uma adaptação à abordagem de Sallenger (2000). Praticamente toda a extensão de base de duna da zona de estudo é propensa a colisão, exceto nas seções que foram definidas com larguras de berma acima do threshold de colisão. O regime de galgamento ocorre para períodos de retorno de 5 anos em praticamente toda a extensão da zona ocidental da Ilha da Barreta e do extremo nascente da zona oriental da Ilha da Culatra. Nas zonas central da Península do Ancão e oriental da Ilha da Armona o regime de galgamento ocorre para períodos de retorno de 5 e 25 anos com algumas seções para períodos de retorno de 50 anos.
O segundo objetivo consistiu na determinação dos Índices Costeiros de erosão e de galgamento, para tempestades com períodos de retorno de 10 e 50 anos multi-paramétricos, e consequente identificação de hotspots de erosão e galgamento, de acordo com o método de avaliação de risco costeiro CRAF1 (Coastal Risk Assessment Framework - Phase 1). Na generalidade, a zona em estudo é caracterizada por índices costeiros de erosão e galgamento médios a baixos, com exceção da zona central da Península do Ancão, realçando esta como hotspot tanto para erosão como para galgamento para tempestades com períodos de retorno de 10 e 50 anos. Os resultados obtidos demonstram concordância com os obtidos em estudos anteriores.
The first objective of this work was to determine the vulnerability to collision and overwash of the sand barriers under study based on the probabilistic analysis of the occurrences of annual maximum run-up levels for multiparametric return periods of 5, 10, 25 and 50 years, and for different beach face slope classes defined for each 100 m section, over the 19-year time series. The collision and overwash regimes were obtained through an adaptation of Sallenger's (2000) approach. Practically the entire dune base extension of the study zone is prone to collision, except in the sections that were defined with berm widths above the collision threshold. The overwash regime occurs for 5-year return periods in practically the entire extension of the western zone of Barreta Island and the eastern end of the eastern zone of Culatra Island. In the central zones of Ancão Peninsula and eastern zones of Armona Island, the overwash regime occurs for 5 and 25-year return periods, with some sections for 50-year return periods. The second objective consisted in determining the erosion and overwash coastal indices for storms with 10 and 50-year multiparametric return periods, and consequent identification of erosion and overwash hotspots, according to the coastal risk assessment method CRAF1 (Coastal Risk Assessment Framework - Phase 1). In general, the area under study is characterized by medium to low erosion and overwash coastal indices, with the exception of the central area of Ancão Peninsula, highlighting this as a hotspot for both erosion and overwash for storms with 10 and 50-year return periods. The results obtained demonstrate agreement with those obtained in previous studies.
The first objective of this work was to determine the vulnerability to collision and overwash of the sand barriers under study based on the probabilistic analysis of the occurrences of annual maximum run-up levels for multiparametric return periods of 5, 10, 25 and 50 years, and for different beach face slope classes defined for each 100 m section, over the 19-year time series. The collision and overwash regimes were obtained through an adaptation of Sallenger's (2000) approach. Practically the entire dune base extension of the study zone is prone to collision, except in the sections that were defined with berm widths above the collision threshold. The overwash regime occurs for 5-year return periods in practically the entire extension of the western zone of Barreta Island and the eastern end of the eastern zone of Culatra Island. In the central zones of Ancão Peninsula and eastern zones of Armona Island, the overwash regime occurs for 5 and 25-year return periods, with some sections for 50-year return periods. The second objective consisted in determining the erosion and overwash coastal indices for storms with 10 and 50-year multiparametric return periods, and consequent identification of erosion and overwash hotspots, according to the coastal risk assessment method CRAF1 (Coastal Risk Assessment Framework - Phase 1). In general, the area under study is characterized by medium to low erosion and overwash coastal indices, with the exception of the central area of Ancão Peninsula, highlighting this as a hotspot for both erosion and overwash for storms with 10 and 50-year return periods. The results obtained demonstrate agreement with those obtained in previous studies.
Description
Keywords
Erosão Galgamento Tempestades Vulnerabilidade Índice costeiro