Short-term changes in the morphodynamic states of beaches and surf zones: An empirical predictive model

Wright, L. D.; Short, Andrew D.; Green, M.O

doi:10.1016/0025-3227(85)90123-9

Cited by 303 publications

(210 citation statements)

References 14 publications

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“…The different beach types can be predicted using the dimensionless fall velocity Ω = H b /Tw s , where H b is significant breaker height, T is peak wave period and w s is median sediment fall velocity (Gourlay, 1968;Dean, 1973). Temporal changes in environmental conditions, quantified by Ω, drive concurrent changes in beach state, albeit with a lag due to relaxation time effects (Wright et al, 1985;Aagaard, 1988;Davidson et al, 2013). This beach state model stimulated a large volume of subsequent research into the key factors controlling beach morphology.…”

Section: Introductionmentioning

confidence: 99%

Role of wave forcing, storms and NAO in outer bar dynamics on a high-energy, macro-tidal beach

et al. 2014

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Outer sand bar dynamics on a high-energy macro-tidal beach were investigated using long-term (multi-year) field datasets of intertidal morphology and offshore bathymetry. Utilising a 15-year time-series of Argus video images, five distinct outer bar types were identified: Mega Rip, Longshore, Crescentic, Crescentic Attached and Welded. The most common classification was Crescentic Attached, with the outer bar oscillations being out of phase with the inner bar oscillations, as would be expected for the shore-normal wave approach at this site. The outer bar had a typical amplitude of 0.5-1 m and a longshore wavelength of 600 m. Changes in outer bar morphology were related to measured and modelled nearshore wave data. However, the outer bar morphology changed over a much longer time scale (monthly-to-annual) than the daily-to-weekly variations in wave height and period. An extended duration of energetic wave action was required to bring about an upstate bar transition to the Longshore or Mega Rip state, where the bar then remained arrested for a significant amount of time, requiring several months of low wave conditions to induce a down state transition through Crescentic to Welded. This slow morphological response is explained by extended relaxation times attributed to the large tidal range at the study site where the outer bar morphology is only active for part of the tidal cycle (several hours around low tide). The configuration and position of the outer bar were related: the more upstate (downstate) bar types being associated with a more offshore (onshore) bar position. The detrended outer bar position was significantly related to a forcing term based on wave power and disequilibrium of the dimensionless fall velocity with offshore (onshore) bar migration occurring when wave conditions were more (less) energetic that the antecedent conditions. The upstate end member (Longshore or Mega Rip) was attained sometime during the winter months for 14 out of the 16 years of monitoring; the outer bar remained attached to the low tide shoreline over the winter 2005/2006 and 2010/2011. These two winters with incomplete upstate cycles were characterised by the lowest winter wave conditions and negative winter North Atlantic Oscillation (NAO) indices, suggesting that the winter NAO is correlated with both beach state and nearshore bar configuration. KEYWORDS

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Section: Introductionmentioning

confidence: 99%

Role of wave forcing, storms and NAO in outer bar dynamics on a high-energy, macro-tidal beach

et al. 2014

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“…During the survey period, the profiles did not present likeness to models and studies in morphological and volumetric changes in existing literature, for the cited beaches, as for example the studies of Larson e Kraus (1994), Morton et al, (1995), Lee et al, (1998), Gornitz et al, (2002), Allan e Komar (2006), Short (2006), Wright e Short (1984), Wright et al, (1985), Short (2003), Masselink e Pattiaratchi (2001), Eliot et al, (2006), Short (2006). The seasonal cycles of the beaches are attributed to variations in the levels of wave energy (Komar 1998), but not all beaches are characterized by seasonal variations of incident waves, some beaches are narrower in the summer and wider in the winter (Masselink & Pattiaratchi 2001).…”

Section: Discussionmentioning

confidence: 96%

“…Studies by Wright e Short (1984), Aubrey e Ross (1985), Wright et al (1985), Bird (1996), Masselink e Pattiaratchi (2001), among others, presented the profile of a beach result which corresponds to an adjustment to seasonal cycles, with erosion occurring in more energetic conditions during the winter, and accretion in conditions of a calmer sea during winter.…”

Section: Discussionmentioning

confidence: 99%

Variabilidade Morfológica Interanual Da Praia De Boa Viagem, Localizada Na Região Nordeste Do Brasil

Gregório¹,

Araújo²

2008

GEO

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Boa Viagem and Pina are urban beaches highly economically important both locally and regionally providing protection for the southern coast of Recife, Pernambuco -Brazil. The objective of this paper is to study the interannual morphological changes which occur on these beaches in order to gather information on the erosion processes. For this purpose 6 topographical profiles were monitored, monthly, from August 2002 to December 2005, during spring tide. To establish the position of each profile it was considered whether the beach was protected by reefs, or not, and if there were coastal protection structures. The largest morphological variation was observed in profiles located to the extreme South and North of the area of study (profiles 1 and 5), as well as the profiles located immediately to the North of the coastal protection features (profiles 4A and 4B). Profiles located in the middle of the study area showed stability. As for sedimentary budget the following variations were observed: negative sedimentary budget in profiles P1 (-4 . Profiles 2 and 3 presented a more consistent budget than those of the profiles located at the extremities of the area (profiles 1, 4A, 4B and 5). The profiles did not present morphologic variations in the beach environment like those mentioned in conventional literature. Profiles 2-1, 3-2 e 4A-3 do not present a linear relation between rates of sedimentary budget. However a positive linear relation between profiles 4B-3 and 5-4B was observed. Variations of accretion and erosion found in this study may be related to seasonal variations in the direction of currents along the coast.

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“…Na Figura 6a, as setas pretas apontam para as dunas frontais que marcam o limite entre a zona de praia e a planície de defl ação. A zona de praia possui uma face com inclinação média de 2,9º, que, de acordo com os valores de ômega (Ω) fi xados por Wright et al (1985) e por meio da Equação 5, proposta por Klein (1997), apresenta um estágio de "praia intermediária" (Ω=4,4), típico dessa porção do litoral do RN (FERREIRA et al, 2014). Na mesma Figura 6a destaca-se, ainda, o cordão de dunas frontais (BIGA-RELLA et al, 1972) paralelo à linha de costa, resultante do acúmulo contínuo de areia devido à ação eólica (HESP et al, 2005), que na fi gura aparece recoberto por uma "rala" cobertura vegetal herbácea.…”

Section: Análise Das Unidades Geomorfológicas Mapeadasunclassified

Mapeamento Geomorfológico De Detalhe Para Delimitação De Áreas De Preservação Permanente (App) De Zonas Costeiras Em Atendimento Ao Cadastro Ambiental Rural (Car)

Ferreira

Santos

Fernandes

et al. 2016

Rev. Bras. Geomorfol.

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Resumo:Este trabalho teve como objetivo apresentar a metodologia para o mapeamento de Áreas de Preservação Permanente (APP) de zonas costeiras em atendimento ao Cadastro Ambiental Rural (CAR), adequada para escala de detalhe que exige o imóvel rural. A metodologia consistiu na geração do Modelo Digital de Elevação (MDE) da zona costeira, a partir do posicionamento GNSS (Global Navigation Satellite Systems); no mapeamento das feições morfológicas costeiras, com reconhecimento in situ; e no atendimento à legislação ambiental vigente quanto às defi nições de APP. No controle de qualidade do MDE do estudo de caso, as discrepâncias entre as altitudes do modelo e as de referência tiveram erro médio quadrático de 0,047 m. No mapa de APP, o índice de exatidão kappa com valor de 83% indicou que a probabilidade das categorias mapeadas (40% de APP e 60% passível de uso) terem sido classifi cadas corretamente representou uma avaliação muito boa, indicando a alta sensibilidade do mapa em classifi car as unidades geomorfológicas do terreno. Os resultados obtidos mostraram que a

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Short-term changes in the morphodynamic states of beaches and surf zones: An empirical predictive model

Cited by 303 publications

References 14 publications

Role of wave forcing, storms and NAO in outer bar dynamics on a high-energy, macro-tidal beach

Role of wave forcing, storms and NAO in outer bar dynamics on a high-energy, macro-tidal beach

Variabilidade Morfológica Interanual Da Praia De Boa Viagem, Localizada Na Região Nordeste Do Brasil

Mapeamento Geomorfológico De Detalhe Para Delimitação De Áreas De Preservação Permanente (App) De Zonas Costeiras Em Atendimento Ao Cadastro Ambiental Rural (Car)

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