O presente trabalho visa caracterizar, através de experimentos numéricos, a hidrodinâmica e o transporte de sedimentos em suspensão no sistema estuarino de Caravelas e Peruípe sob diferentes condições forçantes. O sistema é formado por canais que estabelecem a conexão entre os rios Caravelas e Peruípe. Dados de nível de água e velocidade de correntes, obtidos em coletas de campo foram utilizados para aplicar e calibrar o modelo numérico MOHID. Diferentes experimentos numéricos, simulando condições de maré de sizígia e de quadratura com diferentes condições de descarga fluvial, foram realizados. A partir destas simulações foram obtidas distribuições espaciais e pontuais da concentração de sedimentos em suspensão e das correntes forçadas pela maré integradas verticalmente. Em condições de sizígia o estuário é caracterizado por correntes mais intensas e assimétricas, com dominância de vazante. As maiores concentrações médias de sedimento em suspensão ocorreram em condições de sizígia e o transporte de sedimentos resultante foi em direção ao oceano, em função do domínio das correntes de maré vazante. Os experimentos numéricos mostram que os canais que conectam os dois estuários têm papel relevante na dinâmica local. Eles possuem influência na dinâmica sedimentar do sistema estuarino. A hidrodinâmica e o balanço sedimentar do sistema são principalmente modulados pela altura da maré, com pouca contribuição do aporte de água doce. / The aim of this work is to characterize, through numerical modeling experiments, the hydrodynamics and suspended sediment transport dynamics in the Caravelas ? Peruípe estuarine system under different forcing conditions. The system comprises channels that connect the Caravelas and Peruípe rivers. Water level and current velocity data obtained through field campaigns were used to apply and calibrate the MOHID numerical model. Different numerical experiments simulating spring and neap tides with different river discharge conditions have been conducted. Based on these simulations, the hydrodynamics and spatial and temporal distributions of suspended sediment concentrations have been analyzed. During spring tide the estuary is characterized by intense and asymmetric currents (ebb dominated). The highest average suspended sediment concentration occurred during spring tide conditions, with net sediment transport being seaward. The numerical experiments show that the connecting channels play a relevant role in the local suspended sediment dynamics. The hydrodynamic and sediment balance in the system are modulated mainly by the tidal range, with little influence from the freshwater supply.

Transport and mixing of momentum and salt in an estuary varies in time and space due to river discharge, changes in tidal amplitude and phase, wind stress, and lateral mixing processes, such as secondary circulation. This dissertation focuses on observing, describing, parameterizing, and quantifying secondary circulation in a sinuous coastal plain estuary using acoustic Doppler current meters. This endeavor is made to improve our general understanding of secondary circulation, to identify its primary driving forces, and to better parameterize key physical processes necessary for further study in current numerical models. Secondary circulation is used to describe several mechanisms whose result is to vertically overturn the water column along the transverse axis of a channel. Secondary circulation is commonly generated by one or more of the following mechanisms: channel curvature, unusual bottom topography or channel geometry, planetary rotation, and/or the differential advection of density. Data for this dissertation was collected in the naturally sinuous Satilla River in southeast Georgia. A shallow coastal plain estuary, the Satilla is a partially-mixed estuary characterized by 2 meter range semidiurnal tides. It has a strong neap-to-spring axial current inequality and strong neap-to-spring vertical salinity differences. The balance of mechanisms responsible for the strength and location of secondary flow in the Satilla River varies with spatial location, phase of the tide, and lateral cross-channel position. A simple steady-state momentum balance between the Coriolis acceleration, centrifugal acceleration, the lateral baroclinic gradient, and bottom stress is sufficient to explain secondary circulation in the Satilla River under a wide variety of conditions. The primary momentum balance for this river is a three-way balance between the centrifugal acceleration, bottom stress, and the lateral baroclinic gradient. The dominant mechanism that drives the local secondary circulation depends on the phase of the tide and the lateral placement of the acoustic current profiler.

O presente trabalho visa caracterizar, através de experimentos numéricos, a hidrodinâmica e o transporte de sedimentos em suspensão no sistema estuarino de Caravelas e Peruípe sob diferentes condições forçantes. O sistema é formado por canais que estabelecem a conexão entre os rios Caravelas e Peruípe. Dados de nível de água e velocidade de correntes, obtidos em coletas de campo foram utilizados para aplicar e calibrar o modelo numérico MOHID. Diferentes experimentos numéricos, simulando condições de maré de sizígia e de quadratura com diferentes condições de descarga fluvial, foram realizados. A partir destas simulações foram obtidas distribuições espaciais e pontuais da concentração de sedimentos em suspensão e das correntes forçadas pela maré integradas verticalmente. Em condições de sizígia o estuário é caracterizado por correntes mais intensas e assimétricas, com dominância de vazante. As maiores concentrações médias de sedimento em suspensão ocorreram em condições de sizígia e o transporte de sedimentos resultante foi em direção ao oceano, em função do domínio das correntes de maré vazante. Os experimentos numéricos mostram que os canais que conectam os dois estuários têm papel relevante na dinâmica local. Eles possuem influência na dinâmica sedimentar do sistema estuarino. A hidrodinâmica e o balanço sedimentar do sistema são principalmente modulados pela altura da maré, com pouca contribuição do aporte de água doce. / The aim of this work is to characterize, through numerical modeling experiments, the hydrodynamics and suspended sediment transport dynamics in the Caravelas ? Peruípe estuarine system under different forcing conditions. The system comprises channels that connect the Caravelas and Peruípe rivers. Water level and current velocity data obtained through field campaigns were used to apply and calibrate the MOHID numerical model. Different numerical experiments simulating spring and neap tides with different river discharge conditions have been conducted. Based on these simulations, the hydrodynamics and spatial and temporal distributions of suspended sediment concentrations have been analyzed. During spring tide the estuary is characterized by intense and asymmetric currents (ebb dominated). The highest average suspended sediment concentration occurred during spring tide conditions, with net sediment transport being seaward. The numerical experiments show that the connecting channels play a relevant role in the local suspended sediment dynamics. The hydrodynamic and sediment balance in the system are modulated mainly by the tidal range, with little influence from the freshwater supply.

Orientador: Roberto Fioravanti Carelli Fontes / Resumo: Estuários são ambientes aquáticos de transição entre o continente e o oceano com características únicas, ecológica e economicamente importantes. São condicionados por diversas forçantes naturais e compartilham contribuições terrestres e marinhas. Os principais métodos para estudo hidrodinâmico desses ambientes baseiam-se na análise dos processos de advecção e de mistura das massas de água, gerados pela dinâmica das marés e das descargas dos rios. O presente estudo visa a caracterização hidrodinâmica do estuário do rio Guaratuba (Bertioga, SP) durante as marés de sizígia e de quadratura, a partir de levantamentos hidrográficos realizados com ADCP e CTD e o desenvolvimento de um modelo hidrodinâmico computacional capaz de explicar e simular os processos oceanográficos deste estuário. Os resultados apontaram que, tanto a maré quanto a descarga fluvial têm a capacidade de alterar as vazões e os padrões de salinidade e temperatura no estuário. Em condições de precipitação médias ou na ausência de precipitações, a maré é a forçante dominante do sistema. Durante os períodos de sizígia ocorrem o aumento da turbulência e da mistura vertical. Nas quadraturas, quando as velocidades de corrente são menores, a estratificação vertical é mais estável, e a água salina incursiona até pontos mais internos do estuário. Precipitações na sub-bacia tem relação direta e imediata com o aumento da vazão, afetando a dinâmica e intensificando a estratificação vertical do estuário. O estuário do rio Gua... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Estuaries are transitional aquatic environments, with unique characteristics, ecologically and economically important. They are conditioned by several natural forcings and share land and marine contributions. The main methods to study these environments are based on the analysis of the water masses advection and mixing processes, that are generated by tides and river discharges. The purposes of this study are the hydrodynamic characterization of the Guaratuba’s estuary (Bertioga, SP) during spring and neap tides, based on ADCP and CTD hydrographic surveys, and the development of a computational hydrodynamic model using Delft-3D software, that helps to explain and simulate the main estuarine oceanographic processes. We observed that both, tide and river discharges, have the capacity to alter water flow, as well as salinity and temperature patterns in the estuary. Under mean precipitation conditions or in its absence, tide forces dominate the system. During the spring tide floods, turbulence and vertical mixing increase. During the neap tide floods, when current speed decreases, vertical stratification remains more stable, and saline water penetrates more along the upper estuary. Precipitation episodes in the sub-basin are direct and immediate related to water flow increase, and affect currents dynamics intensifying vertical stratification in the estuary. The Guaratuba estuary is classified as type A, B or D; depending on tidal and river flow conditions. The models we generated... (Complete abstract click electronic access below) / Mestre

[Truncated abstract] The expansion of human populations in coastal land margins has resulted in major modifcations to estuarine ecosystems. The use of numerical models as predictive tools for assessing remediation strategies is increasing. However, parameterisation of physical processes, developed mainly through field investigations, is necessary for these models to be reliable and effective management tools. The physical processes in micro–tidal diurnal tidal systems are relatively unknown and the current study examines field measurements obtained from the upper Swan River estuary (Western Australia), a diurnal, partially mixed system during the summer when the freshwater discharge is negligible. The aims of the study were to characterise, temporally and spatially, the dominant physical processes and associated sediment resuspension. Variability at three dominant time-scales were examined: 1) sub–tidal oscillations (∼5 to 10 days) resulting from local and remote forcing; 2) tidal (∼ 24 hours) due to astronomical forcing; and 3) intra-tidal (∼2 to 3 hours) resulting from the interaction between tidal constituents. Circulation in estuaries is widely accepted in the literature to be dominated, in varying proportions, by tidal range, freshwater discharge and gravitational circulation. In the upper Swan River estuary sub–tidal oscillations were responsible for the largest upstream displacement of the salt wedge in the absence of freshwater discharge. Moreover, these sub–tidal fluctuations in water level modified the ‘classic’ estuarine circulation. The dynamics of diurnal tides are largely controlled by the tropic month, which oscillates at a slightly different period to the lunar month, resulting in the spring–neap tidal cycle to be sometimes different from syzygy. The phase lag between the diurnal (O1 + K1) and semi-diurnal (M2 + S2) constituents, at the seasonal time scale cause the maximum tidal range to be near the solstice. Over a 24–hour tidal cycle this phase lag is manifested as an intra–tidal oscillation that occurs on the flood tide. Turbidity events that last ∼1 to 2 hours occur during the intra–tidal oscillation, but are not related to maximum shear stress predicted from the mean flow characteristics. The increases in turbidity during the intra–tidal oscillation is, however, correlated with the near–bed Reynolds fluxes. During the intra–tidal oscillation advection opposes the estuarine circulation in the near–bed region, promoting vertical shear that results in destratifcation of the water column. The turbulent mixing generated at the interface and in the near–bed region coincide with resuspension events. Similar turbidity data have often been disregarded and documented as being ‘spikes’ based on the premise that the mean flow was below a critical level to resuspend sediment. Resuspension events were not simply related to mean processes and may be controlled by turbulent instabilities generated when tidal currents reverse during an intra-tidal oscillation