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Large beach cusps (LBC, wavelength of ~ 30 m) are intertidal features that can alternately exist in the swash and in the inner surf zone due to tidal sea level changes. They have a larger cross-shore extent (up to 50 m) than traditional cusps. This extent has been explained by a shift of the swash zone during falling tide. The cusps immerse at rising tide and previous studies indicate that surf zone processes are exclusively destructive. Here, the behaviour of large beach cusps in the inner surf zone is investigated by using a 2DH morphological numerical model applied to Trafalgar Beach (Cádiz, Spain). The model results indicate that the inner surf zone processes do not always destroy the cusps but can in fact reinforce them by considering neither the swash processes nor the tidal changes. More generally, in conditions favouring the presence of the LBC the surf zone of a beach can be unstable, leading to the formation of transverse/oblique sand bars that can have characteristics similar to the LBC. Thus, in principle, the LBC could emerge not only due to swash zone morphodynamics but also due to surf zone morphodynamics or a combination of both.

Este trabalho teve como objetivo efetuar uma análise comparativa da estrutura da comunidade fitoplanctônica, variação da biomassa e dados ambientais, na zona de arrebentação das praias arenosas de Brasília Formosa (8º04'S; 34º52'W), Boa Viagem (8º07'S; 34º53'W) e Piedade (8º10'S; 34º54'W) no litoral pernambucano. Amostras com garrafa e com rede foram coletadas durante o período chuvoso (maio, junho e julho/2005) e de estiagem (novembro, dezembro/2005 e janeiro/2006), simultaneamente com os dados ambientais (temperatura da água e do ar, salinidade, material em suspensão, nitrito, nitrato, fosfato, silicato, precipitação pluviométrica, velocidade e direção do vento). Do total de 119 táxons infragenéricos, as diatomáceas obtiveram maior representatividade, em termos de frequência e abundância, destacando-se Asterionellopsis glacialis (Castracane) Round, Bellerochea malleus (Brightwell) Van Heurck, Dactyliosolen fragilissimus (Bergon) Hasle, Helicotheca tamesis (Shrubsole) Ricard e Licmophora abbreviata Agardh. A. glacialis foi dominante durante o período chuvoso e H. tamesis durante o período de estiagem. Os resultados indicaram que as condições ambientais de cada período sazonal refletiram sobre a composição específica, clorofila a e densidade total, propiciando florescimentos esporádicos (2,3 x 10(6) cél.L-1) no período de estiagem. A morfologia e o hidrodinamismo dos ambientes de praia analisados não favoreceram a formação de manchas por acumulação de microalgas.This study aimed to make a comparative analysis of phytoplankton community structure, biomass variation and environmental data in the surf-zone of Brasilia Formosa (8º04'S; 34º52'W), Boa Viagem (8º07'S; 34º53'W) and Piedade (8º10'S; 34º54'W) sandy beaches, on the Pernambuco coast. Bottle and net samples were collected during the rainy season (May, June and July/2005) and the dry season (November, December/2005 and January/2006) with simultaneous environmental data collection (water temperature, salinity, suspended material, nitrite, nitrate, phosphate, silicate, rainfall, wind speed and direction). Among the 119 infrageneric taxa identified, diatoms were the most representative group regarding abundance and frequency, notably Asterionellopsis glacialis (Castracane) Round, Bellerochea malleus (Brightwell) Van Heurck, Dactyliosolen fragilissimus (Bergon) Hasle, Helicotheca tamesis (Shrubsole) Ricard and Licmophora abbreviata Agardh. A. glacialis was dominant in the rainy season while H. tamesis was more numerous in the dry one. Study results indicate that specific composition, chlorophyll a and total density evidenced the seasonal environmental conditions, with occasional blooms (2.3 x 10(6) cells.L-1) in the dry season. Morphology and hydrodynamics were unfavorable to the formation of microalgae patches.

Estudamos a dieta dos juvenis de Trachinotus carolinus (Linnaeus, 1766) em praias da Baía de Sepetiba (Rio de Janeiro, Brasil) entre janeiro de 2000 e abril de 2001. Procuramos avaliar a plasticidade trófica de peixes desta espécie ao longo de um gradiente espacial com diferentes níveis de exposição às ondas, sazonalidade, além de avaliar mudanças ontogenéticas na dieta. Os itens alimentares foram analisados através do índice de importância relativa (IIR), determinado pelos valores das frequências de ocorrência, de número e de peso. Os itens de maior importância foram do subfilo Crustacea, ordens Mysidacea, e o representante da ordem Decapoda Emerita brasiliensis (Schmitt, 1935), além de Cefalochordata, representado por Branchiostoma platae (Fitzinger, 1862). Na zona de maior exposição às ondas (praia de Barra de Guaratiba) e com substrato predominantemente arenoso, a dieta foi constituída principalmente por Emerita brasiliensis e Cirripedia, este último presente nos costões rochosos que limitam a praia; na zona de exposição intermediária (praia de Muriqui), houve um predomínio de Mysidacea e Branchiostoma platae; na zona mais protegida (praia de Itacuruçá), os itens de maior abundância foram Polychaeta, Mysidacea e Branchiostoma platae. Sazonalmente não ocorreu variação no uso de Mysidacea, enquanto Branchiostoma platae foi mais consumido durante o inverno, Polychaeta na primavera e Cirripedia e Emerita brasiliensis, no verão. Mysidacea foi o alimento predominante em todas as classes de tamanho, enquanto Polychaeta foi utilizado predominantemente por peixes menores que 20 mm de comprimento padrão e Emerita brasiliensis e Cirripedia foram consumidos principalmente por indivíduos maiores que 40 mm, somente na praia de maior exposição. O sucesso no uso de praias desprotegidas e zonas de arrebentação por esta espécie de peixe pode ser em parte devido à estratégia trófica oportunista, que utiliza uma ampla variedade de recursos disponíveis no ambiente.We studied the diet of juvenile Trachinotus carolinus (Linnaeus, 1766) in sandy beaches of Sepetiba Bay (Rio de Janeiro, Brazil), between January 2000 and April 2001. We tried to evaluate the trophic plasticity of fish this species along a spatial gradient of wave exposure, seasonality, besides to evaluate ontogenetic changes in the diet. The Index of Relative Importance (IRI) was used to measure the food items, determined by their frequency of occurrence, numbers and weights. The subphylum Crustacea, mainly the order Mysidacea, Decapoda Emerita brasiliensis (Schmitt, 1935) and Cephalochordata, represented by Branchiostoma platae (Fitzinger, 1862) were dominant in the diet. In the most exposed zone (Barra de Guaratiba beach) with predominant sandy substrate, the diet was comprised mainly by Emerita brasiliensis and Cirripedia, this later item common in rocky shores at the beach edge; in the intermediate exposed beach (Muriqui beach), Mysidacea and Branchiostoma platae; in the most protected beach (Itacuruçá beach), Polychaeta, Mysidacea and Branchiostoma platae was predominant. No seasonal change was recorded for the use of Mysidacea, while Branchiostoma platae was the more consumed during the winter, Polychaeta in spring, Cirripedia and Emerita brasiliensis, in summer. Mysidacea was the predominate food in all size classes, while Polychaeta was used predominantly by fish smaller than 20 mm standard length (SL) and Emerita brasiliensis and Cirripedia, were consumed mainly by larger individuals than 40 mm in the most exposed beach only. The success in use of surf zones and sand beaches by this fishes species, it can be partly, due the opportunist trophic strategy that uses a wide variety of available resources on environmental.

The ecomorphology and food habits of juvenile Trachinotus carolinus and Menticirrhus littoralis caught in the surf zone of sandy beaches in Niterói, RJ, were investigated between July 2006 and May 2007. These fish species differ morphologically, but present similarities in their diet composition suggest some slight overlapping in their diet. The importance of food items was assessed using Kawakami and Vazzoler's feeding index. Morphometric variables were recorded to correlate with the diet composition of the different size classes for each species. A total of 210 fishes (Trachinotus carolinus - 122, Menticirrhus littoralis - 88), ranging between 24.2 mm and 112 mm total length, were analyzed, but the stomachs of only 84.8% of them contained food. Trachinotus carolinus presented mysids, Polychaetes and Emerita spp. as the predominant items in their diet. Formicidae and Isopoda were the most important items for class I individuals, whereas mysids and Emerita spp. were important for classes II and III. Class I individuals also showed smaller sized prey (amphipods and isopods) and clupeid fish larvae in their diet. Emerita spp. dominated the food items of Menticirrhus littoralis regardless of the size class. Polychaetes, the second most important item was better represented in class sizes II and III. The main morphometric variable correlated with such differences included mouth position and diameter of the eye.A ecomorfologia e os hábitos alimentares de juvenis de Trachinotus carolinus e Menticirrhus littoralis capturados na zona de arrebentação de praias arenosas em Niterói, RJ, foram investigados entre julho de 2006 e Maio de 2007. Ambas as espécies diferem morfologicamente, mas apresentam semelhanças em sua dieta, sugerindo uma possível sobreposição alimentar. A importância dos itens alimentares foi avaliada utilizando o índice alimentar de Kawakami e Vazzoler. Variáveis morfométricas foram correlacionadas à dieta observada para diferentes classes de tamanho, para cada espécie. Um total de 210 peixes (Trachinotus carolinus - 122, Menticirrhus littoralis - 88), variando entre 24.2 mm e 112 mm de comprimento total, foram analisados, mas apenas 84.8% continham alimento. Trachinotus carolinus apresentou mysidáceos, poliquetas e Emerita spp. como os itens predominantes na dieta. Formicidae e Isopoda foram os itens mais importantes para a classe I de tamanho dos indivíduos, enquanto que mysidáceos e Emerita spp. foram importantes para as classes II e III. Indivíduos da classe I também apresentaram itens de menor tamanho (anfípodos e isópodos) bem como larvas de peixes clupeídeos na dieta. Emerita spp. dominou a alimentação de Menticirrhus littoralis, independentemente da classe de tamanho. Poliquetas, o segundo item mais importante, foi mais bem representado na classe II e III de tamanho dos indivíduos. As principais variáveis morfométricas correlacionadas com essas diferenças incluíram a posição da boca e o diâmetro do olho.

Com o objetivo de conhecer a variação temporal da composição, abundância, diversidade e biomassa do zooplâncton da zona de arrebentação da Praia de Tramandaí, Rio Grande do Sul, amostragens quinzenais foram realizadas entre agosto de 2005 e agosto de 2006. Os arrastos foram efetuados com rede cilindro-cônica com 150 cm de comprimento, 50 cm de diâmetro de boca e malha de 300 µm. Dados de clorofila-a, direção do vento, corrente de deriva litorânea, salinidade, temperatura do ar e da água também foram obtidos. O grupo dos Copepoda foi responsável pela maior diversidade de espécies, sendo que Temora turbinata (Dana, 1849) apresentou maior abundância relativa e freqüência de ocorrência. Outras espécies de Copepoda também foram importantes numericamente como Acartia tonsa (Dana, 1849), Subeucalanus pileatus (Glesbrecht, 1888) e Ctenocalanus vanus (Glesbrecht, 1888). O Mysidacea Metamysidopsis elongata atlantica (Bascescu, 1968) apresentou freqüência de 58,33% e abundância relativa de 44%, sendo o pico de biomassa de mesozooplâncton (96 mg.m-3) registrado em setembro de 2005 correspondente ao máximo valor de densidade apresentado pela espécie (3.535 org.m-3). Informações sobre o zooplâncton desta região são muito escassos e os dados levantados servirão de base para o conhecimento dos processos biológicos que ocorrem na coluna d'água da Praia de Tramandaí.The temporal variability of density, species composition, biomass and diversity of the surf zone zooplankton from Tramandaí Beach, RS, Brazil, was studied between August 2005 and August 2006. Samples were taken forthnightly using a zooplankton net of 150 cm total length, 50 cm mouth diameter and 300 μm nylon mesh size. Data on clorofila-a, wind direction, longshore current, salinity, air and water temperature were taken as well. Copepoda presented the highest species diversity, being Temora turbinata (Dana, 1849) the species with higher relative abundance and frequency of occurrence. Other Copepoda species were also numerically important, such as Acartia tonsa (Dana, 1849), Subeucalanus pileatus (Glesbrecht, 1888) and Ctenocalanus vanus (Glesbrecht, 1888). The Mysidacea Metamysidopsis elongata atlantica (Bascescu, 1968) presented frequency of 58.33% and relative abundance of 44%. The peak of mesozooplanktonic biomass (96 mg.m-3) was recorded in September/2005, corresponding to the maximum density value presented for this species (3,535 org.m-3). Information about zooplankton of this region is scarce and the results of this study will provide a base for the knowledge about the biological processes occurring in the surf zone of Tramandaí Beach.

Natural assemblages show large variability at multiple scales in space and time as a consequence of several abiotic and biotic factors. This study was conducted in the surf zone of Arraial do Cabo (22º 58'S, 42º 01'W) and tested the hypothesis that the ichthyofauna composition and structure differ according to the tidal variation at three beaches with different morphodynamic characteristics. From September 2001 to August 2002 three monthly hauls were carried out at each beach during high (N = 6) and low tide (N = 6) with a beach seine (25 m length, 2,50 m height, 10 mm mesh). At Praia Grande and Prainha beaches, the number of species and individuals was higher during low tide. Also, CPUE (grams) at Praia Grande and Prainha was higher during high tide indicating a movement of many benthivore and piscivore species into the intertidal zone, due to the greater food availability. The fish community structure differed between Prainha and Praia Grande according to the tide in relation to fish biomass, which was higher at high tide, except for Praia dos Anjos (low tide) partially supporting the initial hypotheses. However, the number of individuals and species richness and diversity were higher during low tide, different from the proposed statement, as a reflex of juvenile individuals' abundance.Comunidades de peixes sofrem grande variabilidade em escala espacial e temporal em conseqüência de vários fatores abióticos e bióticos. Este estudo foi realizado na zona de arrebentação em Arraial do Cabo (22º 58'S, 42º 01'W) e testada a hipótese de que a composição e a estrutura da ictiofauna difere de acordo com a variação de maré em três praias com características morfodinâmicas distintas. De setembro/2001 a agosto/2002 foram realizados três arrastos mensais em três pontos de cada praia nos períodos de maré baixa (N = 6) e alta (N = 6), através de uma rede do tipo picaré (beach seine) com 25 m de comprimento por 2,50 m de altura e malha de 10 mm. Na Praia Grande e Prainha, o número de espécies e indivíduos foi superior em maré baixa. Já a CPUE (grama) na Praia Grande e Prainha foi superior na maré alta, indicando um movimento de muitas espécies bentívoras e piscívoras para a zona entremarés em maré cheias, devido à maior disponibilidade de alimento. A estrutura da comunidade de peixes na zona de arrebentação, Praia Grande e Prainha diferiu em função da maré com relação à biomassa de peixes capturados, superior no período de maré alta, exceto na Praia dos Anjos (maré baixa) confirmando parcialmente a hipótese inicial. Já o número de indivíduos, a riqueza e a diversidade de espécies foi superior na maré baixa, diferente do proposto, reflexo da grande abundância de indivíduos juvenis.

This study was undertaken to develop a simple energy dissipation model for computing the root mean square wave height transformation. The parametric wave approach of Battjes and Janssen (1978) was used as a framework for developingthe energy dissipation model. In contrast to the common derivation, the fraction of breaking waves was not derived from the assumed probability density function of wave heights, but derived directly from the measured wave heights. The presentmodel was verified extensively for a variety of wave and beach conditions (including small-scale, large-scale, and field experiments), and compared with four existing dissipation models. The present model gives very good accuracy for a widerange of wave and beach conditions and gives better predictions than those of existing models.

Fish living in coastal waters present behavior patterns ruled by environmental light levels. Diel variations in fish community structure were investigated at Arraial do Cabo surf zone (22º58'S, 42º01'W). From September/2001 to August/2002 monthly sampling consisted of 12 hauls of a beach seine during the day and at night at Praia dos Anjos, Praia Grande and Prainha beaches. Different temporal distribution patterns of the ichthyc community were recorded. At Praia dos Anjos, total richness was higher at night while the average number of species, CPUE, Margalef's richness and Shannon diversity were generally higher during the day. We believe that this pattern was caused by the displacement of some species such as Harengula clupeola,Trachinotus carolinus and Umbrina coroides at night to deeper areas searching for food or for predator avoidance. At Praia Grande and Prainha the average number of species, CPUE, richness and diversity indexes were generally higher at night with the dominant species H. clupeola, Pomatomus saltatrix and Sardinella brasiliensis. It is suggested that the main factor to diel variation is the protection against predators due to darkness, making visualization of the prey difficult, besides the presence of seasonal macroalgae beds at Prainha, which might function as a food area for piscivorous fishes due to the proximity of larger individuals in shallower water especially at night.Peixes que vivem em águas costeiras marinhas exibem modelos de comportamento que são regulados pelos níveis de luz do ambiente. A variação nictemeral na estrutura da comunidade de peixes de zona de arrebentação foi investigada na região de Arraial do Cabo (22º58'S, 42º01'W). Desetembro/2001 a agosto/2002 foram realizadas coletas mensais, sendo efetuadas 12 arrastos utilizando cerco de praia nos períodos diurnos e noturnos na Praia dos Anjos, Praia Grande e Prainha. Diferentes padrões de distribuição da comunidade ictíca foram registrados. Na Praia dos Anjos, o número de espécies foi superior no período noturno. Já o número médio de espécies, CPUE, riqueza de Margalef e diversidade de Shannon foram, em geral, superiores no período diurno. Este padrão de comportamento foi causado pelo deslocamento noturno de algumas espécies, tais como Harengula clupeola,Trachinotus carolinus e Umbrina coroides para áreas mais profundas a procura de alimento ou para evitar predadores. Na Praia Grande e na Prainha, o número médio de espécies, CPUE e os índices de riqueza e diversidade foram, em geral, superiores no período noturno, com a dominância das espécies H. clupeola, Pomatomus saltatrix e Sardinella brasiliensis. Sugere-se que o principal fator para esta variação nictemeral seja a proteção contra predadores devido à escuridão, tornando a visualização da presa mais difícil, além da presença de bancos sazonais de macroalgas na Prainha, que pode funcionar como uma área de alimentação para peixes piscívoros devido ao encontro de uma grande quantidade de indivíduos em águas rasas especialmente à noite.

The paper presents the results of studies of wave transformation on a multi-bar cross-shore profile of the southern Baltic Sea. The field investigations of wave motion were carried out using an offshore wave buoy and string wave gauges at the IBW PAN Coastal Research Station, Lubiatowo (Poland). These experimental results were used to validate statistical relationships between characteristic wave parameters in the coastal region and to assess wave energy dissipation in the surf zone. A simple model for calculating the residual nearshore wave energy is proposed and tested versus the data collected in situ.

The ability to model bar migration in the nearshore zone is critically important for predicting coastal morphology. We present a cost-effective wave-averaged 3D model (CROCO) with parameterization of wave-related bedload transport (adapted SANTOSS), and evaluate/calibrate its performance in comparison with data measured in a two-dimensional wave channel. In this model, suspended-load transport (both in and above the wave bottom boundary layer) is resolved by the flow model. We assume that if the tuning parameters are not robust to varying forcing conditions, the parameterization can be considered a failure. The present work is therefore a first step towards a numerical model capable of predicting the onshore and offshore migration of a sandbar under storm and post-storm conditions using the same set of parameters. One way to achieve this goal is to treat the effects of waves and currents in separate formulations to avoid conflicts and redundancy. We show that the implementation and adaptation of SANTOSS in CROCO can achieve this goal, provided that the hydrodynamics are accurately reproduced and the separation between the wave-related bedload and current-related suspended load formulations is respected. • An adapted version of the SANTOSS formulation is successfully implemented in the 3D waveaveraged CROCO model. • CROCO is tested against the LIP11D flume experiment for onshore and offshore sandbar migration. • The model can predict onshore and offshore sandbar migration with the same set of parameters. • The main drivers of sandbar migration are discussed. • The undertow/velocity skewness drive the offshore/onshore migration within suspended/bed loads. [ABSTRACT FROM AUTHOR]

• Detailed flow measurements along a reef under combined waves and currents are presented. • Offshore/onshore mean flow below wave trough can be found under seaward/shoreward tidal current. • A Reynolds-averaged-Navier-Stokes-equation-based model is validated to analyze the mean flow field and the turbulent kinetic energy. • An existing wave generation module is modified to consider the current effect on waves. Recent field observations have improved our understanding of the role of tidal currents in modulating the wave dynamics over coral reefs. In this study, detailed flow measurements are conducted across an idealized reef profile in a wave-current flume. A typical plunging breaker propagating over both the flooding (shoreward) and the ebbing (seaward) tides are tested, respectively, and compared to the scenario without tidal current (wave only). Laboratory results are reported for the cross-shore distributions of wave height and mean water level as well as the vertical variation of cross-shore mean current below wave trough across a reef. Subsequently, to reproduce the laboratory measurements, the Reynolds-Averaged Navier-Stokes (RANS) equations with a stabilized k-ω SST turbulence model are solved to establish a numerical wave tank. The Volume of Fluid (VOF) method is used to track the free surface and an existing wave generation module is modified to consider the tidal current effect on waves. The numerical model is first validated by the experimental measurements based on the aforementioned three wave-current scenarios. Subsequently, the mean flow field around the reef surf zone and the cross-shore distribution of turbulent kinetic energy (TKE) and Reynolds shear stress along the reef profile are examined via numerical simulations. [ABSTRACT FROM AUTHOR]

In this paper, the development of a class of depth-integrated, phase-resolving models for surface wave propagation, known as Boussinesq-type models (BTMs), is reviewed. This review concentrates on the extension of the leading order formulation for weakly dispersive waves to include a range of physical effects and considers model applications at a range of scales ranging from surf zone processes to ocean basin-scale tsunami propagation. A brief overview of the connection of BTMs to nonhydrostatic models, in either depth-integrated or three-dimensional form, is included. [ABSTRACT FROM AUTHOR]

The diatom Asterionellopsis glacialis sensu lato forms high-density patches in the surf zone of some sandy beaches worldwide and was until recently considered a cosmopolitan species. With the recent description of four cryptic species, the identity of specimens found in these accumulations remains uncertain. In this study, diatom patches were sampled from two sandy beaches of the Brazilian coast: one tropical (Futuro Beach, 3° S; 38° W) and one subtropical (Cassino Beach, 32° S; 52° W). Fine structure of frustules and the sequencing of three phylogenetic markers revealed the subtropical strains to be A. guyunusae and the tropical strains to be a new species, here described as Asterionellopsis tropicalis sp. nov. A. tropicalis was differentiated morphologically by the number of striae in 10 μm at the foot pole and head (39-44; 38-45, respectively), from A. lenisilicea (46-55; 46-64), A. maritima (46-51; 46-60), and A. thurstonii (42-58; 55-70). The number of striae at the head region of the valvocopula (10 μm) helped to distinguish A. tropicalis (56-62) from A. guyunusae (61-64), but A. tropicalis was morphologically undistinguishable from A. glacialis. The sequence divergence from other identified Asterionellopsis species was 13%-16% ( Cox1), 11%-12% (5.8S + ITS2) and 2%-6% ( RbcL), and A. tropicalis formed a distinct monophyletic clade with high support in all analyzed phylogenetic trees (single or multi-locus). This work will aid in the understanding of the ecological and physiological diversity of diatom patches that are key to the trophic webs of sandy beaches. [ABSTRACT FROM AUTHOR]

The Chavara coast of southwest India is well known for its rich beach placer deposits which are being commercially exploited by the industries. Replenishment of these resources, which consist of heavy minerals of varying densities, by the hydrodynamic processes is essential for maintaining the stability of the coast as well as sustenance of mining. Rich concentrations of heavy minerals were reported consistently in the beach sediments of this coast in the past, but a systematic reduction in the concentration of the heavies has been reported during the past one-and-a-half decades. This paper, the first in a series of three, emanates from a programme of study launched to understand the mechanisms that manifest the reported changes in the morphology and mineralogy along this coast. In this study the longshore and cross-shore sediment transport rates along this coast have been estimated adopting numerical model studies. The validated LITDRIFT and LITPROF modules of the LITPACK modelling system have been used for computing the longshore and cross-shore sediment fluxes in the surf zone and innershelf region. The net annual longshore sediment transport is northerly in the surf zone where as it is southerly in the innershelf. Detailed analysis of the computed results shows domination of onshore transport over offshore transport. The beach volume change estimated from the measured beach profile on the other hand shows a reduction in the annual replenishment. The domination of the onshore flux as seen in the computations is actually not reflected in the field observations, and this can be attributed to the influence of excessive sand mining by the industries. [ABSTRACT FROM AUTHOR]

Turbulence closure models are evaluated for application to spilling and plunging breakers in the surf zone using open source computational fluid dynamics software. A new library of turbulence models for application to multiphase flows has been developed and is assessed for numerical efficiency and accuracy by comparing against existing laboratory data for surface elevation, velocity and turbulent kinetic energy profiles. Out of the models considered, it was found that, overall, the best model is the nonlinear k - ϵ model. The model is also shown to exhibit different turbulent characteristics between the different breaker types, consistent with experimental data. [ABSTRACT FROM AUTHOR]

In shallow water, the spectral evolution associated with energy transfers due to three-wave (or triad) interactions is important for the prediction of nearshore wave propagation and wave-driven dynamics. The numerical evaluation of these nonlinear interactions involves the evaluation of a weighted convolution integral in both frequency and directional space for each frequency-direction component in the wave field. For reasons of efficiency, operational wave models often rely on a so-called collinear approximation that assumes that energy is only exchanged between wave components travelling in the same direction (collinear propagation) to eliminate the directional convolution. In this work, we show that the collinear approximation as presently implemented in operational models is inconsistent. This causes energy transfers to become unbounded in the limit of unidirectional waves (narrow aperture), and results in the underestimation of energy transfers in short-crested wave conditions. We propose a modification to the collinear approximation to remove this inconsistency and to make it physically more realistic. Through comparison with laboratory observations and results from Monte Carlo simulations, we demonstrate that the proposed modified collinear model is consistent, remains bounded, smoothly converges to the unidirectional limit, and is numerically more robust. Our results show that the modifications proposed here result in a consistent collinear approximation, which remains bounded and can provide an efficient approximation to model nonlinear triad effects in operational wave models. [ABSTRACT FROM AUTHOR]

This paper provides qualitative descriptions of the physical mechanisms that can cause human instability in surf zones, where human instability is considered the loss of solid contact between an individual's feet and the seabed. The forces resulting from the combination of waves and currents typical in surf zones present a hazard to novice beachgoers and weak swimmers that is often not recognized by those individuals. A conservative 'rule of thumb' is that the deepest water a novice beachgoer should reach, even during the passage of wave crests, is a depth that only reaches the persons thigh, that is, between the knee and the waste. [ABSTRACT FROM AUTHOR]

Chun, H. and Suh, K.-D., 2016. Wave-induced Reynolds stress in three-dimensional nearshore currents model. This paper presents the formulation of the wave-induced Reynolds stress (WIRS), i.e. the correlation of horizontal and vertical water particle velocities, based on the Airy's wave theory. Even though the correlation of the velocities is zero in a constant-depth water, it has a nonzero value if there are slopes on the bottom and mean water level. Comparison of the vertical gradient of the WIRS term with the horizontal gradient of wave-forcing terms shows that the two terms have the same order of magnitude, which in turn is comparable to that of the radiation stress in the surf zone. For the three-dimensional computation of nearshore currents, the WIRS term is incorporated into a three-dimensional ocean model in the σ coordinates. The numerical model is then applied to two laboratory experiments. To see the effect of the WIRS term on the mean flow, numerical simulations without this term are also carried out. The numerical simulations show that the WIRS term influences the flow properties such as mean water level, longshore current, and undertow. [ABSTRACT FROM AUTHOR]

Boulders numbering in the high hundreds/low thousands, and with masses up to 30 tonnes, were transported onshore by Super Typhoon Haiyan in Calicoan Island, Philippines to maximum ground elevations that could exceed 9m and terminal positions up to 180m inland. One-dimensional Boussinesq hindcasts of coastal boulder motion showed intermittent transport initiated at the fronts of infragravity swash bores. Transport distances were found to be highly sensitive to wave-height, enough so that observations of terminal positions may be a viable method of estimating rough paleostorm magnitudes. The large accelerations at bore fronts generated significant inertial forces, particularly for larger boulders, but drag forces had greater root-mean-square magnitudes in all simulations. Widely used relations to infer fluid velocities from boulder properties were tested using modeled boulders - inferred velocities at modeled terminal boulder positions were compared to maximum computed Boussinesq fluid velocities at these locations and found to be significantly lower. This underprediction of inferred velocities was greatest for smaller boulders that were strongly mobile. Inferred drag loads compared to modeled values were somewhat more accurate for large boulders when a Froude number of unity was assumed to estimate flow depths. Although these boulders were unequivocally transported by storm waves, their large sizes and distances traveled venture into what has been considered the tsunami range. Thus, care must be taken to interpret the provenance of coastal boulder fields with unknown origin for lower to mid-latitude regions. [ABSTRACT FROM AUTHOR]

Short, A D, 2016. The Coastal Studies Unit and development of the Australian beach models. In: Vila-Concejo, A.; McCarroll, R.J.; Kennedy, D.M., and Bruce, E. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1-7. Coconut Creek (Florida), ISSN 0749-0208. The Australian coast provides an ideal laboratory in which to undertake beach research on a continental scale. The 30 000 km of open coast surrounds an entire continent that ranges from tropical to temperate latitudes (9-43°S); with tides ranging from <0.5 to 12 m; average breaker wave height from <0.5 m to ∼3 m; beach sediment from fine to medium sand, half of which is carbonate; and many of the ∼12 000 beach systems are embayed. Commencing in the mid-1970s this laboratory was utilized by members of the Coastal Studies Unit (CSU) leading to the development of beach models that encompass the full range of beach types and states that incorporate every Australian beach and most global beaches. This paper will review the development of these models, based initially on beach research on the micro-tidal, wave-dominated southeast coast; then expanding into both the higher wave energy environments of southern Australia and the higher tide range environments of northern Australia; culminating with an assessment of every beach system around the coast. The end result was the wave-dominated, tide-modified and tide-dominated beach models. [ABSTRACT FROM AUTHOR]

Gallop, S.L.; Bryan, K.R.; Pitman, S.J.; Ranasinghe, R., and Sandwell, D., 2016. Pulsations in surf zone currents on a high energy mesotidal beach in New Zealand. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 378-382. Coconut Creek (Florida), ISSN 0749-0208. The exchange of material between the surf zone and continental shelf can be driven by pulsations in rip current velocities. However, there is a poor understanding of the relationship of these pulsations to surf zone morphology and material exchange. Moreover, understanding of rip current dynamics has focused mainly on single-barred beaches in an intermediate state, and there have been few studies on high energy beaches. Therefore, this paper undertakes preliminary research on surf zone current velocity pulsations, on a high energy beach in New Zealand. This initial analysis presents results from two days of measurements using Acoustic Doppler Velocimeters and Lagrangian GPS drifters. Drifters revealed pulsations in current velocities on the order of ∼0.5-2 m s−1 throughout the surf zone, whether inside a rip current circulation cell or not. More infragravity wave energy was associated with constant pulsations in current velocity, and lower infragravity energy with pulsation bursts, lasting 5-10 minutes, interspersed with periods of relatively constant velocity lasting 15-25 minutes. However, higher wave conditions also reduced the exit rate from the surf zone. [ABSTRACT FROM AUTHOR]

McCarroll, R.J.; Brander, R.W., and Turner, I.L., 2016. Bathymetric controls on very low frequency rip current motions. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 418-422. Coconut Creek (Florida), ISSN 0749-0208. Time-averaged mean rip currents are forced by persistent gradients in dissipation over shallow bars and deep rip channels. Time-variable horizontal surfzone eddies, at the ∼10 min or very low frequency (VLF) range, are forced by stochastic wave breaking injecting vortical energy into the surfzone. Previous observations note that deep channel rips have greater variability of velocity while shallow channel rips exhibit greater variability in trajectory, this suggests a continuum of flow states that at present are poorly understood. This paper investigates the degree of bathymetric control on VLF motions illustrating how VLF motions manifest on different morphologies. Three field sites are investigated using low-pass filtered: (i) mean velocity; (ii) variable eddy velocity; (iii) directional standard deviation; and (iv) instantaneous vorticity. A VLF flow-type parameter is introduced to differentiate flow regimes, based on degree of bathymetric control. A novel classification scheme is introduced: (i) strong bathymetric control, with high mean velocities and rip cell oscillation; (ii) moderate control, with high mean velocities and variable VLF trajectories; and (iii) weak control, with low mean velocities and mobile eddies. Level of bathymetric control may be related to channel orientation, in addition to relative depth. This study improves our understanding of rip flow variability over short times frames, with implications for sediment transport and beach safety. [ABSTRACT FROM AUTHOR]

Power, H.E.; Nielsen, P.; Hughes, M.G.; Aagaard, T., and Baldock, T.E., 2016. Wave height distributions in the surf zone on natural beaches. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 917-921. Coconut Creek (Florida), ISSN 0749-0208. Wave height distributions in the surf zone are examined using a large existing field dataset. Observed distributions are compared to the Rayleigh distribution, the Weibull distribution, and the normal distribution. In more than half the 15-minute data runs (57%), wave height distributions were statistically significantly different to a Rayleigh distribution, of which the majority were more narrowly distributed, with fewer extrema. In contrast, only 6% of distributions were statistically significantly different to a normal distribution. The distributions were observed to become narrower with decreasing depth. Data were subsequently fitted to a Weibull distribution with a varying exponent to allow for a change in the shape of the distribution with changing depth. The data show distributions with a wide range of exponents, but a mean of 2.4 indicating that, on average, data are more narrowly distributed than a Rayleigh distribution (exponent of 2). The value of the exponent was observed to increase in shallower water, with a strong inverse correlation between depth and the exponent. [ABSTRACT FROM AUTHOR]

This study presents the analysis of the water surface elevation, velocity and suspended sediment concentration measurements obtained at a large wave flume under mobile bed conditions. The wave reproduced erosive and accretive conditions, and included monochromatic, short waves perturbed with a free long wave, bichromatic and random conditions. Each tested condition started from a handmade 1/15 slope and lasted for an approximate time period of 2.4 h (6 runs of the selected wave condition), to compare the different beach profile developments and, in particular, the events that control sediment transport in the swash and surf zones. All erosive tested conditions produced a shoreline retreat and a bar at the breaking area whose development in time is directly correlated to the length of the breaking area. On the other hand, not all accretive conditions present a shoreward transport, and random conditions do not seem to alter the initial profile. The processed data show the suspended sediment event control produced by the existence or absence of wave–backwash interactions in the swash zone. The existence of these interactions, and their number within the wave group, will be a key parameter in controlling the sediment stirring, water velocity magnitudes and, therefore, the suspended sediment fluxes in the inner surf and outer swash. [ABSTRACT FROM AUTHOR]

2D modeling for surf zone phenomenons are validated in present work using the rotational Boussinesq–Green–Naghdi model. Three benchmark test cases are simulated: tsunami wave runup a conical island; tsunami wave runup complex shelf; and rip current and wave setup over sand bars. The computed results are compared to the experimental data including the free surface deformation and depth-averaged velocities. The simulated 2D cases fundamentally validate the model׳s ability in predicting wave transformation, wave breaking, wave runup and the velocity field for complex hydrodynamic conditions and give the basis for moving on to more complex applications. The lack of irrotationality would strongly contribute to the depth-varying velocity profile of rotational modeling, which has been partially proven in 1D undertow test ( Zhang et al., 2014a ). Unfortunately, few 2D experiments with rotational vortex data measured could be found due to the difficulty of recording the vortex characteristics. Future work would be the model application to much more complex geophysical and engineering problems, where the lack of any irrotational constrain is expected to excel. [ABSTRACT FROM AUTHOR]

Understanding wave breaking phenomena is a challenging problem that still lacks satisfactory understanding. The present paper is concerned with the development of novel instrumentation adapted to obtain Lagrangian field measurements of essential variables that are intimately related to the physics of wave breaking. These miniature (6.4 cm) Lagrangian drifters are equipped with micro-electromechanical systems (MEMS) inertial measurement units (IMUs) that record acceleration, angular rate and magnetic field data at rapid sampling rates (100 Hz). Using a quaternion-based sensor fusion algorithm, multiple sensor data is filtered in postprocessing procedures to obtain the best possible estimates of particle orientation and acceleration. We show that the developed instrumentation is able to collect meaningful data of inertial particle dynamics in a controlled laboratory flow, where the instrumented particle trajectories are benchmarked against an analytical representation of the flow. Results indicate that dead reckoning errors grow quadratically in time and that for a typical wave overturning event trajectory estimates are expected to remain within a radius r<0.7 m with a 95% confidence level. Also, special attention is given to gyroscope reliability during the actual wave breaking process through an empirical evaluation of gyroscope performance in plunging waves. Angular rate measurements from two separate gyroscopes mounted inside the same drifter show high agreement leading to the conclusion that gyroscope errors arising from wave induced vibrations are negligible. Finally, we report on the first ever Lagrangian field observations of inertial particle dynamics in plunging waves with heights on the order of 2 m. We expect that further development of the technology and analysis tools presented herein could revolutionize our understanding of the hydrodynamics of breaking waves. [ABSTRACT FROM PUBLISHER]