Publications

The economical and ecological importance of tidal inlets has fostered the development of empirical tools forinlet management during the last century. This study aims at confronting these empirical theories with resultsobtained with a process-based numerical model, MORSYS2D. This 2DH morphodynamic modeling system isapplied to an idealized tidal inlet/lagoon system with different combinations of significant wave height,tidal range and tidal prism. The numerical model predictions are compared to the empirical models ofHayes, Bruun, O'Brien and FitzGerald and to morphologies observed at natural tidal inlets. The results presentgood accordance with observations as well as with some key behaviors predicted with the empirical theories.The predicted morphologies satisfy the relation of O'Brien between the tidal prism and the cross-sectionalarea, the model reproduces the conceptual model of sand by-passing by ebb-tidal delta breaching of FitzGeraldand the classifications of Hayes and Bruun are generally respected. However, some inconsistencies betweenmodel results andHayes classification highlight the limitations of applying this classification,which only considersthe yearly-averaged significant wave height and tidal range, to a single tidal inlet case.

The patterns of water quality and ecological dynamics in estuaries vary at different time scales. Characterizing thisvariability at short (diurnal and seasonal) time scales is a pre-requisite to investigate the effects of long-term climatechanges. Seasonal scales depend mostly on the natural climatic variability, while diurnal scales are generallyassociated with the tidal cycle and wind events. In order to study the role of these superimposed scales in the Aveirolagoon, an integrated approach, which combines data acquisition and numerical modelling, was followed. Theanalysis was conducted with the three-dimensional, fully coupled hydrodynamic and ecological numerical model,ECO-SELFE, extended to account for the oxygen cycle. For data acquisition three field campaigns were performedalong a salinity gradient (Mira channel), covering different seasonal situations: March 2009, September 2009 andJanuary 2010. These campaigns, each lasting 24 hours, included the measurement of physical, chemical andbiological parameters (river flow, water levels, currents velocities, water temperature, salinity, dissolved oxygen,nutrients and chlorophyll a). Results show the ability of the model to represent both the spatial and temporal patternsobserved for the different variables. Chlorophyll a and nutrients tend to present larger concentrations upstream thandownstream, with the largest values observed in spring. The distribution patterns are significantly influenced by thetidal dynamics.

ABSTRACT: This study investigates sediment transport at a very low-energy backbarrier beach in southern Portugal, from aspring-to-neap tide period, during fair-weather conditions. Rates and directions of transport were determined based on the applicationof fluorescent tracer techniques. Wind and currents were collected locally, whereas the dominant small and short-period wind waveswere characterized using a morphodynamic modelling system coupling a circulation model, a spectral wave model, and a bottomevolution model, well validated over the study area.For the recorded conditions sediment transport was small and ebb oriented, with daily transport rates below 0.02m3 day-1. Tidalcurrents (mainly ebb velocities) were found to be the main causative forcing controlling sediment displacements. Transport rateswere higher during spring tides, tending towards very small values at neap tides. Results herein reported points towards thedistinction between tracer advection and tracer dispersion in this type of environment. Transport by advection was low as a consequenceof the prevailing hydrodynamic conditions (Hs<0.1 m, and max. current velocity of 0.5ms-1) and the tracer adjustment tothe transport layer, whereas dispersion was relatively high (few metres per day). Tracer techniques allowed distinguishing the broadpicture of transport, but revealed the need for refinement in this type of environments (bi-directional forcing by ebb and flood cycles).

Tidal asymmetry is a key factor in the geomorphology of many coastal lagoons. Whilst tidal asymmetry insemi-diurnal tidal regimes has been extensively studied, its occurrence in mixed tidal regimes is less wellunderstood, and has a number of unique causes and characteristics. Tidal phase duration analysis andleast squares harmonic analysis have been used to study the temporal and spatial nature of asymmetryin both offshore and coastal lagoon tides at the Murray Mouth in south-eastern Australia. GIS analysis ofbathymetric survey data has been used to study the roles of lagoon bathymetry on tidal distortion.Tidal asymmetry in the Murray Mouth coastal lagoon results from frequency relationships between majorastronomical driving tides as well as bathymetry-induced tidal transformations. The frequency differencebetween the K1 and S2 tides produces an important 6-monthly ebb/flood-dominant asymmetry cycle in theincoming oceanic tides, whilst phase relationships between the K1 and K2 tides contribute to persistentasymmetry. The use of standard relationships between theM2 andM4 tides as asymmetry indicators is shown tobe invalid for this mixed tidal regime. In this shallow, microtidal system, the impacts of bathymetry on tidalasymmetry within the lagoon are profound, with inlet and channel configurations identified as the mostimportant controlling factors.The results of this study may inform the strategic management of tidal inlets in mixed tidal regimes, suchas the Murray Mouth, that are subject to intermittent or long-term constriction.

The generation of unstructured triangular grids for coastal applications requires extensive manual tunning, in order to improve the stability, accuracy and efficiency of the model simulations. As current grids reach 105-106 nodes, this manual tunning is no longer feasible. This paper presents a new post-processor that aims at optimizing the local distribution of nodes and elements by adding and deleting nodes and by changing the connections between nodes. The algorithms target a smooth transition between elements sizes by making the number of connections of each internal node as close to 6 as possible.An application of the post-processor to various grids shows that the grid roughness is reduced by 10-30%, while decreasing marginally the number of nodes and maintaining the global nodal distribution. To illustrate the benefits of the post-processor, a grid with 130.000 nodes of the maritime zone under Portuguese jurisdiction is used to simulate tides with a good accuracy (root mean square errors below 10 cm) and without numericaloscillations. The model results provide an extensive database of tidal elevations that can feed boundary conditions to local estuarine models.

The Portuguese southern coast national and international appeal turns it into a highly relevant area concerning the country's economy. Vale do Lobo is a resort located in the centre of this coast, where the beach has been suffering from erosion problems for several years now. Local interventions have been executed in order to prevent the erosion of the beach, yet the efficiency of such strategy has not been verified.This study's main purpose is to enable a better understanding of the evolutionary trends of the coastline between Quarteira and Ancão inlet and to analyse the efficiency of the beach nourishment interventions as a protection technique for a coastal environment with the wave energy exposure and geomorphologic characteristics of the present one.The study focussed on a 10-year period, during which, 700x103 and 370x103 m3 of sand with D50=0.76 mm (slightly larger than the D50 of the native beach) were extracted from offshore, and deposited in the foreshore. The wave climate in the study area was processed, analysed and used as input for modelling the nearshore processes. In addition, beach profiles measured alongshore have been analysed to obtain the representative beach profile. Coastlines of different dates have been derived from aerial photographs.The longshore transport model Litdrift and the coastline model Litline were applied to study the sediment dynamics. Litdrift was used to estimate the longshore transport capacity of the beach for the hydrodynamic series considering the representative beach profile previously obtained. These results were then used to calculate the evolution of the coastline due to the incident wave climate with Litline model. Aerial photographs were used to verify the model. The analysis of the two beach nourishments performed allowed to infer on the efficiency of this coastal protection technique to delay the erosion process.

This article addresses the problem of sedimentation at the entrance of a harbour by evaluating and understanding thesediment dynamics in the adjacent beaches. The results of the methodology applied to acknowledge the beaches

In the past decade, two-dimensional (2DH) morphodynamic modeling systems were developed to simulate the morphological changes due to the combined action of waves, tides and winds. In spite of some significantsuccesses, they are unable to predict complex morphological behaviors, such as inlet infillings in highly dynamicenvironments during winter energetic wave conditions. For these reasons, the state of the art in morphodynamic modeling tends to evolve towards three-dimensional (3D) modeling systems. In this context, the present study focuses on the development of an unstructured 3D coupled wave-current model taking into account the verticalstructure of radiation stresses based on recent theoretical developments. The model is applied to the common breakwater test case and succeeds efficiently to reproduce the wave-driven circulation behind the breakwater.The study investigates also the vertical structure of the flow and the wave-induced setup along a cross-shore profile. The undertow is well-predicted by the model in the surf zone and the wave-induced setups predicted by the 3D model are about 30-40% greater than those simulated by a 2DH approach. This important aspect could berelevant in storm surge and inundation studies for which the quality of the predictions could be strongly improved by using a 3D fully coupled wave-current model.

A extracção de sedimentos nas zonas costeiras é uma actividade de importância e prática crescentes há já vários anos e em diversos países. A evolução de uma zona de extracção depende essencialmente do tipo de sedimento e das características hidrodinâmicas do local. No presente trabalho pretendeu-se estudar a evolução morfológica e sedimentar de uma escavação ao largo de Vale do Lobo (Algarve, Portugal) com base em 3 campanhas batimétricas realizadas entre 2006 e 2008, antes e após a extracção, assim como numericamente, através da aplicação de um modelo morfodinâmico

Presently, conceptual and numerical sediment concentration modelling is largely based on the diffusionapproach. However, several works have shown that this approach is, frequently, unsuitable to model the profiledistribution of different grain size particles in the same flow. In order to understand the grain size effects onsuspended sediment concentration profiles under breaking wave conditions, a new data set was collected at threewest coast Portuguese beaches (Almagreira, Caparica and Comporta beaches). As expected, the relativeconcentration for the entire grain-size spectrum shows a systematic decrease with distance to the bed, thoughwith different profile shapes (exponential and power law). The analysis of the relative concentration profiles foreach sediment fraction show similar profile patterns; however, as expected, the decrease in the relativeconcentration with height strongly depends on particle size and assumes a different behaviour at each site. In thiscase, diffusion approach was unable to explain all the observed profile patterns, namely the overlapping ofcoarse sediment profiles and the different profile shapes in the same flow. These deficiencies were overcome bythe use of the convection-diffusion approach.

The estuary of the Tagus river is one of the largest estuaries in Europe covering an area of about 320 km2. It is located in the Portuguese west coast, in the metropolitan area of Lisbon, and due to its social and economic context and environmental characteristics it is the Portuguese most relevant estuary. The estuary comprises along its margins 11 municipalities with about 1.6million inhabitants (Tavares et al., 2015). It hosts the Port of Lisbon, the national leader in the movement of vessels (in number and in GT), and the Tagus Estuary Natural Reserve considered one of the most important sanctuaries for birds in Europe.

Estuaries are highly variable systems and the most productive ecosystems in the world.Phytoplankton is a major contributor to the high productivity, rapidly responding to changes inthe environment

This work evaluates the morphological evolution of the coastal frontage south of Figueira da Foz (west coast of Portugal) after the extension of the north jetty based on the analysis of topo-bathymetric surveys located in twelve equidistant transepts in the study site. The results show that the study site has large inter-annual morphological variations and the complex morphological behaviour shows an erosive tendency of the beach face downdrift of the structures.

Climate change and the predicted increase of human activities in estuaries may increase the hazards inthese systems. Water observatories can support both the daily and the long-term management of estuarineecosystems. Although in the past water observatories were mostly based on observations, these tools haveevolved to account for forecasts, scenarios analysis and indicators

Coastal systems are among the most productive ecosystems in the world, providing multipleresources and guaranteeing the resilience of the coastal communities. Climate change (e.g.,sea level rise) represents a major threat to the world

Climate change, such as sea level rise, represents a major threat to the world

This study aims to investigate the changes in the infragravity wave energy under partialshort-wave breaking conditions induced by a longshore bar. Field observations of near-bottompressure records on a cross-shore array were analysed for such purpose. The bispectrum wasemployed to detect the phase-coupling between short and infragravity wave frequencies. This allowedto separate the infragravity wave energy in bound and free energy components.The bar crest induced a decrease on the short-wave energy due to depth-induced breaking. At thesame location, a damping on the bound infragravity wave energy was observed. This dampingcoincides with a negative value of the short-wave radiation stress cross-shore gradient. This providesevidence that bound infragravity wave energy decreases with a reduction in the forcing.

Resumo: Os processos de evolução costeira em Cabo Verde, resultantes de fatores naturais e deatividades humanas, são ainda pouco conhecidos. Analisa-se neste trabalho a evolução morfológica dabaía do porto da Praia, na ilha de Santiago, com base em levantamentos hidrográficos de 1882 a 2016,fotografia aérea, imagens de satélite e cartografia histórica. Recorre-se também à modelaçãomatemática de processos hidrodinâmicos e morfodinâmicos, considerando a interação ondascorrentes,para interpretar as condições locais. Os elementos analisados sugerem uma tendência deacumulação sedimentar, com uma taxa média de avanço da praia, a longo prazo, da ordem de 1 m/ano.Estima-se que o caudal sólido transportado episodicamente pelas ribeiras afluentes seja uma fontesedimentar importante. Embora a recente expansão do porto tenha diminuído a influência da ação dasondas, as condições mais favoráveis à remobilização e à circulação sedimentar no interior da baíapermanecem associadas aos períodos de agitação marítima mais energética

Evolution of Nazaré beach after the construction of the fishing harbour

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The hydrodynamics and sediment dynamics of a low energy estuarine beach was analysed. The beach is subjected to local wind waves generated in an area of restricted fetch, wake waves generated by catamarans and a semi diurnal meso-tidal regime. Only storm events of short duration modify the beach profile, which, once the normal hydrodynamic conditions are restored, naturally recovers its initial shape. The beach is characterised by having a steep upper slope until mean sea level, followed, seaward, by a low gradient terrace, and a bimodal sediment distribution. To investigate the hydro sedimentologic beach behaviour, wind, topo-hydrographic and sedimentologic data were used as input and validation of process based numerical modelling. Wave generation and transformation in an area of restricted fetch, nearshore circulation, sediment transport and morphological evolution were simulated for average annual conditions and storm conditions. The statistical analysis of a six-year wind data series allowed to derive the average wind regime, based on which, the average annual wave regime and the average annual longshore sediment budget, 14.5x103 m3year-1, were calculated. The contribution of the individual components of the representative wave regime, discretised by directional sector and height class of incidence, was evaluated as well as the spatial distribution of the longshore sediment transport in the active part of the beach profile. The characteristics of the wave groups generated by the passage of catamarans at different speeds were estimated and their action on the beach morphology was simulated. Although when the catamarans travel at 20 knots speed the average annual wake wave energy dissipated at the beach is 2.5 times higher than the average annual wind wave energy, the erosion effect on the beach profile is still not relevant for the present traffic. In opposition, short duration storm events generate the formation of an erosion scarp at the upper part of the beach face. The numerical modelling of this phenomenon allowed to acknowledge on the protective effect that the low gradient terrace has on the beach face.

O objectivo do presente trabalho foi o estabelecimento de um modelo matemático do fenómeno da refracção das ondas de gravidade, apoiado num pro¬grama cálculo automático bastante aperfeiçoado e enquadrado por uma técnica de utilização prática que permitisse a resolução rápida dos problemasinerentes ao cálculo de um conjunto de diagramas de refracção, independentemente do número de ondas monocromáticas a analisar.Numa primeira parte, apresentam-se algumas considerações sumárias so¬bre o método de estabelecimento do programa de cálculo e sobre a necessidade de se dispor de um modelo matemático de refracção. A segunda parte é dedicada ao estudo do fenómeno da refracção das on¬das de gravidade e seu tratamento numérico. No Cap.3 indicam-se, de forma Muito sintética, os fundamentos da teoria das ondas de pequena amplitude sendo deduzidas as principais expressões utilizadas no estudo da refracção. É apresentada a teoria da refracção de uma onda sinusoidal, sendo abordado um vasto leque de problemas tais como os aspectos energético e geométrico da refracção, as soluções analíticas para fundos algébricos, as zonas de convergência e cáusticas, a refracção por efeito de correntes, e as aproximações da teoria da refracção. Por último criticam-se os métodos gráficos habituais de cálculo de planos de ondulação. No Cap. 4 são deduzidas as equações de base do tratamento numérico da refracção das ondas sinusoidais como um problema de valores iniciais. No Cap. 5 são apresentadas as dife¬rentes técnicas de cálculo e de interpolação das principais grandezas di¬rectamente ligadas a obtenção de uma ortogonal e dos sucessivos valores da amplitude relativa da onda. São indicados os métodos numéricos de integração das equações diferenciais do raio de onda e do coeficiente de afasta¬mento de ortogonais. E feita referencia a técnicas de alisamento da batimetria. Em todos os casos são apresentados os métodos utilizados no LNEC as¬sim como outros referidos na bibliografia. No Cap. 6 são indicadas, para os vários programas preparados no LNEC, as técnicas de cálculo e de inter¬polação e os métodos numéricos de integração usados. São apresentadas, de uma forma exaustiva, todas as verificações dos programas levadas a cabo após o seu estabelecimento, designadamente a verificação analítica e a comparação dos resultados obtidos com os métodos numéricos e gráficos para fundos ir¬regulares. No âmbito da verificação dos programas é ainda feita referência a resultados obtidos por outros autores e a ensaios em modelo reduzido. Por último tiram-se conclusões sobre a escolha dos programas a lançar em exploração.A terceira e última parte é consagrada à análise do actual programa de cálculo de diagramas de refracção. Assim, no Cap. 7 indicam-se, em li¬nhas muito gerais, o tipo de dados a fornecer, as hipóteses de exploração do programa e o seu modo de funcionamento; é ainda feita uma análise da estrutura do programa, relativamente pormenorizada. 0 Cap. 8 é consagrado à discrição da forma de utilização prática do programa, sendo discutidas as perspectivas de custo da sua utilização cobrindo todas as hipóteses de exploração do programa, ilustrados com os dados e resultados respectivos. No Cap. 9 apresentam-se as conclusões do trabalho e indicam-se as linhas de orientação a seguir no que respeita ao aperfeiçoamento do modelo matemático da refracção e ao estabelecimento de outros modelos matemáticos dependentes ou não daquele.0 texto principal de dissertação encerra-se com 96 referencias bibliográficas, correspondentes aos principais trabalhos consultados pelo autor, na realização do presente estudo; esta bibliografia refere-se a Abril de 1975. Em Anexo no Apêndice I, apresentam-se os elementos referentes aos programas inicialmente estabelecidos no LNEC e cujo aperfeiçoamento posterior conduziu ao programa actualmente em exploração. São indicados, em linhas gerais, as formas possíveis de exploração daqueles programas, o seu modo de funcionamento e os dados a fornecer. É feita uma análise de pormenor da es¬trutura dos programas, sendo descrita a sua forma de utilização prática, e apresentados vários exemplos de aplicação ilustrados com os dados e resul¬tados respectivos. São indicadas algumas verificações efectuadas a estes programas.

0 caminhamento das areias ao longo das costas marítimas é regulado por leis ainda incompletamente apreendidas, mas cujo conhecimento cada vez mais perfeito se torna indispensável no projecto e ensaio em modelo reduzido de grande parte das obras destinadas a solucionar problemas de hidráulica marítima.Começa-se neste trabalho por caracterizar, sob os pontos de vista hidrodinâmico e de movimentação aluvionar, a orla costeira, zona em que o transporte litoral se processa, abordando-se a seguir o aspecto prático mais importante do fenómeno, ou seja, a previsão dos caudais sólidos a partir das características das ondas e do material móvel que forma a praia.Com este último objectivo analisa-se o conjunto dos dados experimentais disponíveis, segundo uma perspectiva baseada na análise dimensional do fenómeno, para a seguir se proceder a um estudo experimental focado sobre a influência do peso específico e do diâmetro do material móvel.Apresentam-se ainda, em anexo, os conceitos básicos respeitantes às correntes longitudinais, fenómeno que teve também de ser objecto de um estudo aprofundado, por estar intimamente relacionado com o transporte sólido litoral.

Este trabalho constitui um estudo em extensão sobre as característi¬cas mais importantes dos perfis transversais das praias e sobre a evolução resultante da actuação da ondulação. Pretendeu-se assim obter um conhecimento geral sobre este assunto, de modo a permitir, por um lado, o melhor planeamento dos trabalhos marítimos e, por outro, uma melhor interpretação dos modelos reduzidos de fundo móvel.Utiliza-se neste trabalho uma nomenclatura original em língua portuguesa, na tentativa de estabelecer uma equivalência com os termos consagrados na literatura siglo-saxónica.Dentro do esquema geral acima enunciado, são estudadas com maior atenção: o mecanismo da movimentação dos materiais nos fundos; a evolução so¬frida pelos perfis em resultado da actuação das ondas e destas em conjugação com as marés; as características da faixa de rebentação das praias; e as variações da granulometria do material móvel.Quanto à movimentação dos materiais em fundos de maior profundidade, apresenta-se uma interpretação sobre as profundidades a que se inicia o transporte dos sedimentos e o sentido desse transporte.Em relação à evolução dos perfis descrevem-se as suas fases mais significativas, quer para o caso de ondas de período e altura crescentes como decrescentes. Introduzem-se os conceitos de perfis de máxima erosão e máximo enchimento.

O presente trabalho baseia-se num estudo experimental sobre o funcionamento hidráulico de esporões marítimos no caso em que estes limitam troços de praia que se comportam, na sua evolução, como unidades fisiográficamente independentes. Pretende-se, com este estudo, contribuir para o conhecimento do mecanismo de evolução de praias em que são construídos campos de esporões, com vista ao projecto de dispositivos funcionais deste tipo de defesa costeira. Acessoriamente, tirando partido dos esporões como meio de medição do caudal sólido litoral, fa¬zem-se algumas considerações sobre as relações existentes entre o transporte litoral e as características da onda actuante.O relatório é constituído pelas seguintes partes : a Introdução, em que se define o objectivo do estudo e as suas características; o capítulo I, em que se apresentam noções gerais sobre esporões; o Capi¬tulo II, em que se dá conhecimento do estudo experimental realizado, definindo o seu planeamento, a tecnologia experimental, as características dos ensaios realizados, a interpretarão dos resultados obtidos e as conclusões; o Capitulo III, que diz respeito a casos reais de emprego de esporões, em que, após umas generalidades, se apresentam as principais características das obras de defesa da Cova do Vapor - Costa da Caparica, do campo de esporões da praia de Espinho e do esporão da praia do Estoril, finalizando com algumas conclusões; o Capítulo IV em que se apresentam considerações sumárias sobre caudal sólido litoral, as quais compreendem algumas generalidades, considerações teóricas, resultados experimen¬tais, observações na natureza e conclusões; finalmente, as Conclusões Finais, onde se agrupam todas as considerações do estudo que se julgam de primordial interesse.

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