PROFUNDIDADE DE FECHAMENTO E PERFIL DE EQUILÍBRIO DE PRAIA UM ESTUDO DE CASO EM SAND KEY, FLORIDA (depth of closure and the equilibrium beach profile - a case study from Sand Key, West-Central Florida)
Abstract
A presente pesquisa foi realizada a partir da análise de quinhentos e cinqüenta e cinco perfis de praia, realizados no campo durante o intervalo de 5 anos, ao longo dos 20 km de extensão da ilha-barreira ‘Sand Key”, localizada na costa oeste central da Flórida (Golfo do México). Os perfis foram analisados com o objetivo de compreensão das características regionais de profundidade de fechamento e perfil de equilíbrio de praia. Usando uma média de 6 anos do comportamento de condições extremas de ondas para um intervalo de 12 horas obtidas em uma estação “WIS”(“Sistema de Informação de Ondas”, desenvolvido pelo “Army Corps of Engineers”, EUA) e aplicadas à fórmula de Birkemeier (1985), foi possível reproduzir em boas condições a profundidade de fechamento na parte norte da área de estudo (sem o controle direto do fundo rígido), enquanto o uso da fórmula de Hallermeier (1978, 1981) ultrapassou bastante o valor obtido nos levantamentos de campo.
Palavras-chave: perfis de praia, perfis de equilíbrio, mode- lização de perfis de equilíbrio, profundidade de fechamento, transporte sedimentar litorâneo, costa da Flórida.
ABSTRACT
Five hundred and fifty-five beach profiles surveyed during 5 years (3 years for the Indian Shores) along the 20-km beach at Sand Key, west-central Florida were analyzed to understand the regional characteristics of closure depth and equilibrium beach profile. Using a 6-yr average of 12- hr extreme wave conditions obtained from a local WIS station, the Birkemeier (1985) formula reproduced the measured closure depth at the northern part of the study area (without the direct control of the hard bottom) well, whereas the Hallermeier (1978, 1981) formula significantly over-predicted the measured value.
Key Words: Beach profiles, equilibrium profiles, beach profile models, depth of closure, cross-shore sediment transport, Florida Gulf coast.
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