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蔡景華 and King-wah Choi. "Finite difference modelling of estuarine hydrodynamics." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1985. http://hub.hku.hk/bib/B30425153.
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Knock, Clare. "Finite element modelling of estuarine hydrodynamics." Thesis, University of the West of England, Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258716.
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Choi, King-wah. "Finite difference modelling of estuarine hydrodynamics /." [Hong Kong] : University of Hong Kong, 1985. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1232503X.
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Punt, Adrian Gavin. "Measurement and modelling of estuarine chemistry." Thesis, University of Plymouth, 2000. http://hdl.handle.net/10026.1/1720.
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A l-D tidally resolving hydrodynamic model of the Tweed Estuary has been encoded using the Estuarine Contaminant Simulator, ECoS. The model results of axial and time series variations in water elevation, salinity and turbidity are compared to field data recorded during the LOIS survey programme. The organic and inorganic controls on estuarine pH have also been investigated by encoding a new template to predict the effect of changing salinity and temperature on the pH of estuarine water. The template has been coupled to the hydrodynamic model to predict pH variations in the estuary. The model results have shown conservative behaviour of the inorganic carbon system through out the majority of the estuary, but also identified an area of potentially high photosynthetic activity near the limit of saline intrusion during periods of low summer flows. Low (< 2 ^g 1"') concentrations of chlorophyll a in the water column and increases in pH correlated with tidal inundation of the river estuary banks imply that benthic photosynthetic process are important water chemistry in the upper estuary. The effects of salinity, turbidity and pH on Kd(Cd) and K<i(Zn) has been investigated using radiotracer incubation experiments and analytically determined measurements. The results show a reduction in IQ with increased salinity, but that the K<iS determined analytically are an order of magnitude higher than those measured when radiotracers are used. Analytically determined K<iS are reduced with increasing SPM concentration and increased at higher pH. Although no photosynthetically mediated control of radiotracer uptake was identified partitioning was significantly reduced (> 90 %) when a metabolic inhibitor was added. The Kd has been encoded as an exchange transfer and used to predict axial distributions and the flux of these metals from the riverine catchment to the sea. Model results indicate that the partition coefficients determined fi-om the radiotracer studies can not fully account for the analytically determined distribution between phases. It is hypothesised that colloids and Fe-Mn oxides precipitates play a significant role in trace metal transpon in low turbidity, high pH conditions. The results have implications for the measurement and modelling of chemical fluxes in low turbidity systems.
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Bruder, Brittany Lynn. "Assessing hydrokinetic tidal energy extraction for Rose Dhu Island, Georgia: A case study for tidal rivers with marsh environs." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53864.
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Hydrokinetic tidal power is a novel and emergent technology undergoing continuous advancement with much of the progress focused on large utility scale projects. This resource is potentially underutilized because much of the coastal United States, despite having substantial tidal currents, do not have the deep and wide environments required by most of the developing turbine technology. This dissertation includes a detailed characterization of the tidal hydrodynamics for Rose Dhu Island, Georgia used for a tidal energy resource assessment as well as a general feasibility study for tidal estuaries with extensive wetlands.
For predictions and evaluation of the estuarine hydrodynamics, data from an existing numerical model of the estuary encompassing the island is utilized. Field measurements in close proximity to the island are used to calibrate the model as well as characterize local hydrodynamic features. After the model calibration, the simulation data is used to evaluate the hydrodynamics. Wetland dominated estuaries commonly have a high degree of non-linear distortion which govern the relative durations and strengths of the tidal stages and thus the overall hydrodynamics and incoming hydrokinetic energy. The Ogeechee Estuary is characterized as ebb dominant with peak ebb and flood volume fluxes near high tide as a result of the increased storage capacity of the wetlands. Lowering the average wetland elevation in the model decreased ebb dominance and quickened the transition from flood to ebb tide. Increased domain friction in the model removed energy from the system and reduced ebb dominance. Enhanced model marsh friction reduced lateral flooding of the wetlands as well as ebb dominance. Localized measurements surrounding the island are analyzed to determine a location near the southwest coast of the island as a hydrokinetic energy hotspot. A kinematic and dynamic analysis is performed using channel transect measurements to identify key physical processes behind the hotspot formation. The hotspot forms due to sub-critical flow acceleration over a singular bump in the topography. High streamwise momentum is further concentrated at the hotspot due to secondary circulation cells across the channel. Flood tide circulation is characterized by two co-rotating cells induced by channel curvature and delineated by the bump. Ebb circulation consists of two counter-rotating cells from flow confluence of two upstream channels.
Once the hydrodynamics are understood, the theoretical and technical resource assessment of the island is completed. A sensitivity analysis of hydrokinetic energy and tidal distortion is performed on synthetic data. For a principle constituent and its first harmonic, distortion greatly changes as does the distribution of velocities and energy as the relative phase varies. While the theoretical energy remains consistent, the technical energy can greatly vary. This effect is reduced with the addition semi-lunar variation. Using a simplified analytical method, the maximum average channel power is estimated as 8.80 MW. For the hotspot it is estimated that there is 30.3 MWh available to capture yearly with an average power of 3.46 kW for a turbine with an area of 10 square meters. For the same turbine area with conservative efficiencies, the hotspot could provide a yearly technical energy of 10.9 MWh with an average power of 1.25kW for the island. Due to the complex localized hydrodynamics, both the theoretical and technical resource varies greatly across and along the channel. These considerations are more pertinent when performing a hydrokinetic energy resource assessment in a marsh estuary than for large scale bay-ocean exchange environments, the present industry focus.
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Savant, Gaurav. "Prediction of estuarine morphological evolution." Diss., Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-06202008-102016.
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Donald, Ian R. "A preliminary assessment of the hydrodynamics of the Touw River and Wilderness Lakes system with emphasis on the management of the estuary mouth." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/85775.
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Thesis (MEng)--Stellenbosch University, 2013.ENGLISH ABSTRACT: The Touw River estuary and Wilderness coastal lakes is a sensitive system from a flooding and ecological viewpoint and, therefore, careful consideration is placed on the hydrodynamics and salinity levels within the system. The estuary consists of a “temporary open/closed” estuary, where during closed mouth conditions, the sand bar at the estuary mouth is artificially managed in an attempt to reduce flood water levels in the system. The reason behind this management strategy is the construction of residential property along the flood plains of the estuary and coastal lakes, which in the past, had been exposed to regular cycles of inundation during flood events. In an attempt to reduce flood water levels in all water bodies and hence reduce the risk of inundation, a management policy was formulated. The past and present management plan is to maintain the sand bar at Touw estuary mouth, during closed mouth conditions, at an elevation of between +2.1m to +2.4m MSL, based on proposals made by the CSIR in 1981. Recent flood events, after the implementation of the management policy, still occasionally result in significant inundation of residential property, which has raised concern for some interested parties over the effectiveness of the management strategy. Furthermore, a growing concern was also evident over the long term wellbeing of the system from an ecological viewpoint. Historical data shows significant changes in salinity levels since the implementation of the management strategy which could impose negative long term effects on the system. In this study, numerical models were consequently constructed and applied in order to analyse the effectiveness of the current management policy and recalculate flood water levels under a number of proposed scenarios. Long term salinity changes were also analysed in an attempt to better understand salinity propagation throughout the system, using extreme hypothetical cases. Through the analysis of the simulation results, it was concluded that flood water levels in the Touw estuary were almost completely dependent on the size of the Touw River flood and the initial height of the sand bar at the estuary mouth. Whereas, water levels in the coastal lakes are almost entirely dependent on the quantity of runoff into the lakes and their initial water levels. The current management plan, involving only artificial manipulation of the sand bar at the estuary mouth, therefore has a fairly insignificant effect on flood water levels achieved in the coastal lakes. Furthermore, it was concluded that the construction of the preparatory channel is a vitally important aspect of the current management plan and that skimming of the sand bar alone is ineffective to completely mitigate the risk of residential inundation along the banks of the Touw River. The salinity modelling study provided a first indication of the salinity characteristics within the system. It was found that the penetration of seawater into the system was less prominent as the water bodies became further removed from the ocean and that a direct relationship was evident between the volume of direct freshwater inflow to a water body and the degree of salinity variation in that specific water body. In water bodies with high volumes of direct freshwater inflow such as the Touw estuary, a large degree of salinity variation is evident. However, in water bodies with no freshwater inflow, such as Rondevlei, salinity levels remain more stable and are less likely to fluctuate.
AFRIKAANSE OPSOMMING: Uit ‘n vloed- en ekologiese oogpunt is die Touwsriviermonding en Wilderniskusmere ‘n uiters sensitiewe stelsel en daar is dus deeglike oorweging gegee aan die hidrodinamika en soutvlakke in die stelsel. Die monding bestaan uit 'n "tydelike oop / geslote" monding, en tydens geslote mondtoestande word die sandbank by die riviermond kunsmatig beheer in 'n poging om vloedwatervlakke binne die stelsel te verminder. Die rede vir hierdie strategie is omdat baie residensiële eiendomme langs die vloedvlaktes van die monding en kusmere gebou is, wat in die verlede aan 'n gereelde siklus van oorstromings blootgestel is tydens vloede. In 'n poging om vloedwatervlakke in al die watermassas te verminder, en sodoende die risiko van oorstroming te verminder, is 'n bestuursbeleid geformuleer. In beide die vorige en die huidige bestuursplanne is die sandbank in die Touwsriviermond tydens geslote mondtoestande in stand gehou op 'n hoogte van tussen 2,1 m en 2,4 m MSL, gebaseer op die voorstelle wat deur die WNNR in 1981 gemaak is. Onlangse vloede wat plaasgevind het na die implementering van die beleid, het steeds van tyd tot tyd gelei tot noemenswaardige oorstromings van residensiële eiendomme, en kommer is uitgespreek deur 'n paar belanghebbende partye oor die doeltreffendheid van die strategie vir die bestuur. Daar is verder kommer uitgespreek oor die langtermyn welstand van die stelsel uit 'n ekologiese oogpunt. Historiese data toon 'n beduidende verandering in soutvlakke sedert die implementering van die bestuurstrategie met ‘n negatiewe langtermyn uitwerking op die stelsel. In hierdie studie is daar derhalwe numeriese modelle opgestel en toegepas ten einde die doeltreffendheid van die huidige bestuur van die beleid te bepaal, asook om die vloedvlakke te herbereken en te analiseer na aanleiding van 'n aantal voorgestelde scenario's. Langtermyn soutgehalte veranderinge is ook ontleed in 'n poging om die soutgehalte verspreiding deur die hele stelsel beter te verstaan, deur gebruik te maak van uiterste hipotetiese gevalle. Deur die ontleding van die simulasie resultate, is daar tot die gevolgtrekking gekom dat vloedwatervlakke in die Touwsrivier-monding byna heeltemal afhanklik was van die grootte van die Touwsrivier vloed en die aanvanklike hoogte van die sandbank by die riviermond. Watervlakke in die kusmere is egter byna heeltemal afhanklik van die hoeveelheid afloop na die mere en die aanvanklike watervlakke. Die huidige bestuursplan, wat slegs ‘n kunsmatige manipulasie van die sandbank by die riviermond behels, het dus 'n redelik onbeduidend invloed op die vloedwatervlakke wat in die kusmere bereik is. Daar is verder tot die gevolgtrekking gekom dat die konstruksie van die voorbereidende kanaal 'n uiters belangrike aspek van die huidige bestuursplan is, en dat die afskraping van die sandbank alleen oneffektief sou wees om die risiko van residensiële oorstroming langs die oewer van die Touwsrivier uit te skakel. Die soutgehalte modelleringstudie verskaf 'n eerste aanduiding van die soutgehalte eienskappe binne die stelsel. Daar is gevind dat die penetrasie van seewater in die stelsel minder prominent was as in die watermassas verder van die see af, en dat daar 'n duidelike direkte verband is tussen die volume van die varswater wat direk invloei na 'n watermassa en die mate van soutgehalte variasie in daardie spesifieke watermassa. In watermassas waar hoë volumes varswater direk invloei soos die Touwsrivier-monding, is 'n groot mate van soutgehalte variasie sigbaar. In die watermassas waar geen varswater invloei nie, soos die Rondevlei, bly soutvlakke meer stabiel en is minder geneig om te wissel.
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Marvan, Fernando G. "A two-dimensional numerical transport model for organic-rich cohesive sediments in estuarine waters." Thesis, Heriot-Watt University, 2001. http://hdl.handle.net/10399/1212.
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Burgess, Heidi Marie. "The influence of tide, meteorological conditions and hydrodynamics of fine sediment transport in a macro-tidal estuarine lagoon." Thesis, University of Brighton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406820.
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With predicted climate change and sea level rise, the understanding of estuarine systems becomes more critical so as to gain an insight into the stability of the coastal environment both for environmental and economic reasons. The combined influence of tide and meteorological effects on the erosion, transport, deposition, consolidation cycle (ETDC) of intertidal sediment is not well understood. To further the knowledge into this area an intensive data collection program was conducted in the previously hydraulically un-investigated, macro-tidal estuarine lagoon at Pagham Harbour, Sussex. Monitoring of variations in the elevation of the mudflats indicate that generally accretion occurs in the west of harbour, with the east acting as source as well as a temporary storage area for the sediment which is primarily imported from the English Channel during winter storm periods. The redistribution of the sediment is dependant upon exposure to predominant wind direction, wind speed and local channel geomorphology. Monitoring of the water column identified that sediment is moved landward by means of a peak in turbidity which occurs at the beginning of each flood tide. This sediment movement is enhanced by tidal pumping caused by saline stratification which occurs at the onset of each flood tide as a result of a combination of the harbours' geomorphology and of the control of freshwater input. Precipitation during low tide causes eroded sediment to migrate towards the channels of the harbour, and the increase in freshwater discharge moves loosely consolidated sediment seaward. High freshwater events also retard the advancement of the saline water, prolonging the duration of the peak in turbidity. The magnitude of the peak is controlled by tidal range and recent precipitation events. Calibration of an "off the shelf coastal model highlighted the need for more data collection so that the accuracy of the prediction of the tidal curve, which directly influences depth and velocity, can be improved. Changes in climate and sea level are rendering coastal defences unsustainable, with management plans becoming outdated at an accelerating rate. Knowledge gained from these investigations can aid coastal manager to make more informed decisions for future management strategies in Pagham Harbour and at other coastal sites.
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Sloss, Craig R. "Holocene sea-level change and the aminostratigraphy of wave-dominated barriers estuaries on the southeast coast of Australia." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060306.154507/index.html.
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Dlouhy, Brittney, and Brittney Dlouhy. "Thread Drifting by Juvenile Bivalves in the Coos Bay Estuary, Oregon: Species Identification and the Influence of Estuarine Hydrodynamics and Diel Migration." Thesis, University of Oregon, 2012. http://hdl.handle.net/1794/12346.
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From September 2009 to July 2011 I collected vertically stratified zooplankton samples and recorded estuarine water parameters on a monthly basis in the Coos Bay estuary, Oregon during flood and ebb tides. I identified five taxa of juvenile bivalves in the plankton:
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Cahyono, M. "Three-dimensional numerical modelling of sediment transport processes in non-stratified estuarine and coastal waters." Thesis, University of Bradford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520623.
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Details are given herein of the development, refinement and application of a higher-order accurate 3-D finite difference model for non-cohesive suspended sediment transport processes, in non-stratified estuarine and coastal waters. The velocity fields are computed using a 2-D horizontal depth-integrated model, in combination with either an assumed logarithmic velocity profile or a velocity profile obtained from field data. Also, for convenience in handling variable bed topographies and for better vertical resolution, a δ-stretching co-ordinate system has been used. In order to gain insight into the relative merits of various numerical schemes for modelling the convection of high concentration gradients, in terms of both accuracy and efficiency, thirty six existing finite difference schemes and two splitting techniques have been reviewed and compared by applying them to the following cases: i) 1-D and 2-D pure convection, ii) 1-D and 2-D convection and diffusion, and iii) 1-D non-linear Burger's equation. Modifications to some of the considered schemes have also been proposed, together with two new higher-order accurate finite difference schemes for modelling the convection of high concentration gradients. The schemes were derived using a piecewise cubic interpolation and an universal limiter (proposed scheme 1) or a modified form of the TVD filter (proposed scheme 2). The schemes have been tested for: i) 1-D and 2-D pure convection, and ii) 2-D convection and diffusion problems. The schemes have produced accurate, oscillation-free and non-clipped solutions, comparable with the ULTIMATE fifth- and sixth-order schemes. However, the proposed schemes need only three (proposed scheme 1) or five cell stencils. Hence, they are very attractive and can be easily implemented to solve convection dominated problems for complex bathymetries with flooding and drying. The 3-D sediment transport equation was solved using a splitting technique, with two different techniques being considered. With this technique the 3-D convective-diffusion equation for suspended sediment fluxes was split into consecutive 1-D convection, diffusion and convective-diffusion equations. The modified and proposed higher-order accurate finite difference schemes mentioned above were then used to solve the consecutive 1-D equations. The model has been calibrated and verified by applying it to predict the development of suspended sediment concentration profiles under non-equilibrium conditions in three test flumes. The results of numerical predictions were compared with existing analytical solutions and experimental data. The numerical results were in excellent agreement with the analytical solutions and were in reasonable agreement with the experimental data. Finally, the model has also been applied to predict sediment concentration and velocity profiles in the Humber Estuary, UK. Reasonable agreement was obtained between the model predictions and the corresponding field measurements, particularly when considered in the light of usual sediment transport predictions. The model is therefore thought to be a potentially useful tool for hydraulic engineers involved in practical case studies
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Souza, Pricilla. "Evolution and stratigraphic architecture of tidal point bars with and without fluvial input: influence of variable flow regimes on sediment and facies distribution, and lateral accretion." ScholarWorks@UNO, 2019. https://scholarworks.uno.edu/td/2705.
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Tide-influenced point bars represent a significant proportion of shallow-marine deposits, commonly developed along meandering channels in most backbarrier and estuarine systems. However, sedimentological studies to characterize this type of deposit are still emerging. They often present very heterogeneous internal architectures which development is controlled by the complex flow patterns operating in tidal environments. The study of the sedimentological and morphological characteristics of these features provides better understanding of the hydrodynamic processes that shape coastal systems and control their evolution as well as it contributes to better reservoir potential prediction and production strategy optimization, as tidal point bars may represent hydrocarbon reservoirs in subsurface and their heterogeneous characteristics directly impact reservoir quality. In this study, we investigated six modern tidal point bars located along distinct estuarine tidal channels in Georgia. Using core data, 2D shallow seismic data and current measurements and flow velocity profiles, we discussed the main hydrodynamic controls on sediment transport and distribution, and determined how they affect the morphology, the internal architecture and the sediment distribution within these bars. We confirmed that the influence of fluvial input in tidal channels plays an important role on the development of the morphology and the heterogeneous architecture of point bars as it adds more complexity to the system hydrodynamics, promoting more asymmetric variations in water level fluctuations and huge variations of current velocities. We proved that point bars developed in distinct tide-influenced channels and estuaries, although present very different sedimentary facies distribution, may have sedimentary facies in common, which organization is analogous to surface processes operating at each environment. We demonstrated that differences in tidal asymmetries between the ebb and flood channels produce sedimentological differences between the different parts of the bar. This study showed that tidal point bars present distinct heterogeneous sediment distributions, morphologies and internal architectures that do not conform to the existing theoretical models of fluvial point bars and highlighted that, despite the differences in local hydrodynamic conditions, similarities identified between the different bars permitted us to distinguish the sedimentological responses to regional allogenic events, which can be mistakenly interpreted as sedimentological responses to local autogenic events.
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Zhang, Jisheng. "Modelling of astronomical tide and storm surge in estuary." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=26090.
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Becker, May Ling Luettich Richard A. "Hydrodynamic behavior of the Cape Fear River estuarine system, North Carolina." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2006. http://dc.lib.unc.edu/u?/etd,2965.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.Title from electronic title page (viewed Jun. 23, 2010). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Marine Sciences Physical Oceanography." Discipline: Marine Sciences; Department/School: Marine Sciences.
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Turrell, W. R. "Axial fronts and transverse flows in well-mixed estuaries." Thesis, Bangor University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328782.
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Mahamod, Yusuff. "Sedimentary processes in the Dwyryd Estuary." Thesis, Bangor University, 1989. https://research.bangor.ac.uk/portal/en/theses/sedimentary-processes-in-the-dwyryd-estuary(ca0aea23-480c-4032-ba10-12a9adee740c).html.
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This study aims to describe and quantify the important sedimentary processes which control the dispersal and accumulation of sediment in the Dwyryd Estuary, adjacent to Tremadog Bay in West Wales. It is shown that sedimentation in the estuary is dominantly control by fast tidal currents, and in the bay by weak tidal currents. Landward transport of coastal sediments by tidal currents is the residual sediment transport path. The spatial distribution of textural parameters of the estuarine sediments is related to the strength of tidal currents as well as the morphology and bathymetry of the study area. The estuarine sediments, predominantly sand, are very similar in texture and mineralogy to the adjacent beach sediments but markedly different to the river sediments. However, the beach sediments are slightly coarser and more poorly sorted than the estuarine sediments. In contrast, sediment in the deeper parts of Tremadog Bay are finer than both the estuarine and beach sediments due to the presence of substantial admixture of mud. The grain size distributions of most of the sediments are neither lognormal nor log-hyperbolic reflecting the great variability of hydrodynamic conditions in the study area. Using previously published flume data, a new sediment transport rate formula in the form of a power law has been developed for computation of total sediment load from the bed mean grain size and flow parameters: Uc The exponent n varies from 2.7 (for 0.93 mm sand) to 4.18 (for 0.19 mm sand). This is in contrast to the Bagnold (1966) formula which regards the exponent value (equal to 3) as constant for all grain sizes. Sediment transport patterns depend on the asymmetry between flood and ebb tidal currents due to distortion of the tidal wave on entering the estuary. Estimates of sediment budgets from surveyed profiles suggest that large amounts of sand have been transported from coastal areas into the estuary, supporting the mineralogical evidence. The estimates are of the same order of magnitude as estimates using flow velocity data and the above sediment transport formula.
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Gao, Guanghai. "Numerical modelling of hydrodynamic and sediment-bacteria interaction processes in estuarine and coastal waters." Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54738/.
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A study has been undertaken to investigate and improve the representation and modelling of a range of various hydrodynamic, biochemical and sediment transport processes relating to the transport of enteric bacteria organisms in estuarine waters. In this study a relatively simple turbulence model was first further investigated to predict the complex three-dimensional flow structure in a flume with vegetation. The main purpose of this part of the study was to try and acquire accurate velocity profiles of complex flows without the need for a more advanced two-equation turbulence model, requiring values for a number of unknown coefficients and extra computing cost. The results showed that the simple two layer mixing length model was capable of giving more accurate complex velocity profile predictions, with the advantage of requiring limited coefficient data. Formulations developed through earlier studies for dynamic decay rates were then refined and included in the numerical model. The model predictions were tested against field data, with good agreement being obtained. Further refinements to the representation of the transport of bacteria through the flow field were included in the model by the novel addition of the interaction of bacteria with the sediments by partitioning the total bacteria into their free-living and attached phases using a dynamic partitioning ratio. This ratio was related to the suspended sediment concentrations. The novel method used in this study was to include the re-suspension and deposition of the absorbed bacteria with the sediments and this approach has been tested against analytical solutions for steady uniform flow conditions, and published field and experimental data. The model was then applied to the Severn Estuary. After calibration against available data sets the model was then run for different scenarios to investigate the effects of different hydro-environmental conditions on the bacteria distributions in the Severn Estuary. The model was finally used to investigate the impact of the proposed Cardiff-Weston tidal barrage on the hydrodynamic, the sediment transport and bacterial processes within the Severn Estuary. The results showed that the barrage would reduce the currents, as well as significantly reducing the suspended sediment concentrations and bacteria concentration levels in the estuary.
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Fortunato, Andre ́Bustorff. "Three-dimensional modeling of coastal flows using unstructured grids /." Full text open access at:, 1996. http://content.ohsu.edu/u?/etd,203.
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Shirkhani, Hamidreza. "Methodological Developments for an Improved Evaluation of Climate Change Impact on Flow Hydrodynamics in Estuaries." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34351.
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The knowledge of flow hydrodynamics within the next decades is of particular importance in many practical applications. In this study, a methodological improvement has been made to the evaluation of the flow hydrodynamics under climate change. This research, indeed, proposes an approach which includes the methods that can consider the climate change impact on the flow in estuaries, gulfs, etc. It includes downscaling methods to project the required climate variables through the next decades. Here, two statistical downscaling methods, namely, Nearest Neighbouring and Quantile-Quantile techniques, are developed and implemented in order to predict the wind speed over the study area. Wind speed has an essential role in flow field and wave climatology in estuaries and gulfs.
In order to make the proposed methodology computationally efficient, the flow in the estuary is simulated by a large-scale model. The finite volume triangular C-grid is analysed and shown to have advantages over the rectangular (finite difference) one. The dispersion relation analysis is performed for both gravity and Rossby waves that have crucial effects in oceanic models. In order to study the unstructured characteristic of the triangular grids, various isosceles triangles with different vertex angles are considered. Moreover, diverse well-known second-order time stepping techniques such as Leap-Frog, Adams-Bashforth and improved Euler are studied in combination with the C-grid semi discrete method. The fully discrete method is examined through several numerical experiments for both linear and non-linear cases. The results of the large-scale model provide the boundary conditions to the local coastal model.
In order to model the flow over a local coastal area, a well-balanced positivity preserving central-upwind method is developed for the unstructured quadrilateral grids. The quadrilateral grid can effectively simulate complex domains and is shown to have advantages over the triangular grids. The proposed central-upwind scheme is well-balanced and preserve the positivity. Therefore, it is capable of modelling the wetting and drying processes that may be the case in many local coastal areas. It is also confirmed that the proposed method can well resolve complex flow features. The local model incorporates the outputs of the downscaling and large-scale flow models and evaluates the flow hydrodynamics under changing climate.
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Izumi, Vitor Massaki. "Comparação entre as desembocaduras do Complexo Estuarino do Cassurubá (BA): características hidrográficas e hidrodinâmicas." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/21/21132/tde-20042012-154735/.
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Os principais fenômenos físicos que atuam como forçantes de movimento nos estuários são descarga fluvial, maré e vento. As diferentes intensidades com que cada um pode atuar proporcionam uma vasta gama de combinações e condições distintas, às quais estão submetidos os estuários de todo o mundo. O Complexo Estuarino do Cassurubá (CEC) está sujeito a descargas fluviais com vazões da ordem de 101 m3/s, a mesomarés variando entre 2 e 4 m, e a ventos de E/NE de ordem 101 m/s com algumas entradas de S/SO também de ordem 101 m/s. Contudo, seus canais Norte e Sul apresentam diferentes características hidrográficas e hidrodinâmicas. O objetivo deste trabalho foi confirmar e explicar esta distinção, através de dados de velocidade, temperatura, salinidade e profundidade, com suas respectivas variações temporais. Os objetivos específicos foram direcionados para se testar a hipótese de que a pequena diferença entre as vazões dos rios Caravelas e Peruípe (sendo a deste maior) pode criar configurações estruturais distintas e, consequentemente, gerar alterações no transporte de massa e volume. A análise dos dados demonstrou que ambos os canais estuarinos são influenciados principalmente por fenômenos marinhos, neste caso a maré. Os padrões estruturais e a ciclicidade das variações dos parâmetros estudados foram determinados predominantemente pela maré e a velocidade de suas correntes, com leve influência da descarga fluvial nas estruturas termohalina e hidrodinâmica. Como previsto, a pequena diferença observada a favor do rio Peruípe, associada a características geográficas e batimétricas locais, mostraram-se determinantes para os processos físicos que correm no CEC. Síntese dos resultados: Velocidades máximas de 0,5 m/s nas quadraturas e 1 a 1,5 m/s nas sizígias, em ambos os canais. Circulação estuarina clássica observada nitidamente nas quadraturas. Sizígias mostram mesmo sentido ao longo da coluna d\'água. Maior simetria entre correntes de vazante e enchente durante sizígias, menor durante quadraturas. Nova Viçosa com assimetria mais evidente devido à maior descarga fluvial. Salinidades mínimas de 32 em Caravelas e 17 em Nova Viçosa. Salinidades superiores a 36 em toda a coluna d\'água durante fases de sizígia, associadas às temperaturas de 28º, constataxv se a intrusão da Água Tropical em ambos os canais estuarinos. Temperatura passou de 25 ºC no inverno para 28 ºC no verão, em ambos. O canal de Caravelas mostrou-se importador durante três campanhas e exportador em apenas uma, porém com maior intensidade. O canal de Nova Viçosa mostrouse exportador durante as quatro campanhas. Onda de maré comportou-se como progressiva em Caravelas no inverno, e como estacionária no verão. Em Nova Viçosa foi como estacionária o tempo todo. Processos de mistura dominaram na maior parte do tempo. Estratificações formadas mais em quadratura e em torno de estofas. Classificações estação A - transição entre 1a e 2a - colunas bem misturadas, com fraca estratificação vertical; estação C - transição entre 1a, 2a, 1b e 2b - com apreciável estratificação nas quadraturas e colunas bem misturadas nas sizígias. Predomínio da difusão turbulenta no transporte de sal rio acima em A. Em C, boa participação da advecção nas quadraturas.River discharge, tidal currents and wind stress are the main physical phenomena that drive estuarine circulation. Each of these parameters can act in different intensities, resulting in a vast diversity of estuary characteristics. Cassurubá Estuarine Complex (CEC) is influenced by river discharges on the order of 10 m3/s, mesotides ranging between 2 and 4 m, NE wind speeds of around 10 m/s, and occasionally SW winds of around 10 m/s. An interesting feature of the CEC is the distinct hydrographic and hydrodynamic characteristics between its north and south channels. In this way, the objective of this study is to corroborate and explain this dissimilarity, using data of depth, water and wind velocities, water temperature and salinity, as well as their temporal variations. Specific objectives are to test the hypothesis that small differences between Caravelas and Peruípe rivers discharges (where the latter is the largest one) can create different structural configurations of those parameters and, consequently, cause variations in mass and volume transport. Data analysis showed that both channels are mainly influenced by marine phenomenon, in this case tides. Patterns of structural and cyclical variations of studied parameters were determined mainly by tides and speed of their currents, with slight river discharge influence in thermohaline structure and hydrodynamics. As expected, the small difference observed in favor of Peruípe River, associated with local geographic and bathymetric characteristics, proved to be decisive for the physical processes that occur in CEC. Summary of results: maximum speed of 0.5 m/s in neaps and 1 to 1.5 m/s in springs, in both channels. Classical estuarine circulation observed clearly in neaps. Springs show same direction along the water column. Greater symmetry observed between ebb and flood currents during spring. Nova Viçosa showed more evident asymmetry due to higher river discharge. Minimum of salinity was 32 and 17, in Caravelas and Nova Viçosa, respectively. It reached values greater than 36 through water column during springs, associated with 28ºC temperatures, it indicates de intrusion of Tropical Water in both channels. Temperatures varied from 25 º C in winter to 28 º C in summer. Caravelas xvii channel was importer during three campaigns and exporter during one, but this one with greater intensity. Nova Viçosa channel was exporter during four campaigns. Tidal wave behaved as progressive in Caravelas estuary during winter and stationary in summer. Peruípe estuary showed stationary characteristics all campaigns. Mixing processes dominated most of time. Stratifications formed mainly in neap and around tide inversions. Classification station A - between 1a and 2a - well mixed, with weak vertical stratification; station C - between 1a, 2a, 1b, 2b - appreciable stratification in neaps and well mixed in springs. There was predominance of turbulent diffusion in upestuary transport of salt in station A. In station C, a greater role of advection appeared in neaps.
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McArthur, Jennifer. "A comparison of the effects of extreme events on the hydrodynamics in Mersey and Esk estuaries." Thesis, Lancaster University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337547.
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Garcia-Oliva, Miriam. "The impact of tidal stream farms on flood risk in estuaries." Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/22972.
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There is a growing interest in tidal energy, owing to its predictable nature in comparison to other renewable sources. In the case of the UK, its importance also lies on the availability of exploitable areas as well as their total capacity, which is estimated to cover more than 20% of the country demand. However, the level of development of this kind of technology is still far behind other types of renewable energy. However, several studies focused on a variety of individual devices, followed by more recent research on the deployment of large arrays or tidal farms. Potential sites for energy extraction can be found in narrows between islands and the coast or estuaries. The latter present some advantages for the installation and the connection to the grid but estuaries are often prone to flood risk from tides and surges. Therefore, the objective of this thesis is to evaluate the effect that very large groups of turbines could have on peak water levels during flooding events in the case of being deployed in estuarine areas. For that purpose, a new methodology has been developed, which implies the use of a numerical model (MIKE 21 by DHI), and it has been demonstrated against a real case study in the UK: the Solway Firth estuary. Another objective has consisted of integrating in this thesis the results from detailed CFD modelling and optimisation techniques involved in the project. A literature review has been carried out in order to identify the current state of the art for the different subjects considered in the thesis. Different aspects of the numerical model used for this study (MIKE 21) have been presented and the modelling of the turbines within the code has been validated against experimental and CFD data. The procedure to include large numbers of turbines in the code is also developed. An analysis has been done of the different estuaries existing in the UK suitable for tidal energy extraction, identifying their main geometrical features. Based on this, idealised models of estuaries have been used to assess the influence that the channel geometry could have on the impact of tidal farms under extreme water levels. The effect has been measured by comparing the results of the numerical model between the case with and without turbines under different flooding scenarios. Finally, the same methodology has been applied to a real case study selected from the previous group of estuaries namely the Solway Firth. An initial model has been created, according to the available data at the start of the research, which contained some errors related to the water depth at the intertidal areas in the upper estuary. Therefore, when a more realistic dataset became available, an improved model was created. The improved model has been used to assess the effects of tidal farms in the estuary under a coastal flooding event. It is concluded that there is significant influence of the channel geometry over the locations where the maximum changes in water levels due to the tidal farms will happen. Nevertheless, the effects seem to be more relevant in terms of the decrease rather than the increase of peak water levels for all geometries and the maximum changes seem to be in the order of dm. This is in agreement with the results of the Solway Firth models and can be summarised as a positive net effect over flood risk. On the other hand, a concern has been raised about the impact on intertidal areas, which could be the subject of future research.
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Shi, Jie. "Integrated modelling of hydrological and hydrodynamic processes, dynamic bacteria decay with climate change and intensive farming in riverine and estuarine water." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/98617/.
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The water quality deteriorations in river and estuarine waters are a global issue. Particularly, the water quality impairment due to contamination of Faecal Bacteria Indicator, such as E. coli and Faecal Coliform in river channel, estuary bathing and shellfish waters are of special interests due to potential risks to human health. These indicators are important in water quality assessment outlined in both EU Water Framework Directive and US Clear Water Act. The hypothesis of the study is that the global climate change and intensive farming would cause severe deterioration to faecal coliform levels in these water bodies. Approaches to quantify these impacts are carried out with numerically modelling through catchment model Soil and Water Assessment Tool (SWAT) and hydrodynamic model DIVAST with the focus in the coastal catchment of river Frome and Piddle connected to a natural harbour in Dorset, southern England.
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Clasen, Hunter Lee. "Flow and Transport in Low-Gradient Rivers and Estuaries." Scholar Commons, 2018. http://scholarcommons.usf.edu/etd/7134.
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For this dissertation I studied flow and transport in low gradient Florida streams. Chapter 2 is a statewide analysis of long-term variations in stream discharge. The results from Chapter 2 suggest that changes in mean annual stream discharge are controlled by the Atlantic Multi-Decadal Oscillation (AMO). During the warm phase, mean annual discharge decreases in central Florida and increases in north Florida. The opposite is true during the cool phase, with mean annual discharge increasing in central Florida and decreasing in north Florida. This pattern is observed for both components of stream discharge, base flow and runoff.
The following two chapters are part of an analysis of particle transport in low gradient mangrove estuaries. Chapter 3 describes the use of a numerical model to simulate the hydrodynamics of a coastal reach of the Shark River, Florida Everglades and the development of a Lagrangian particle tracking model. The particle tracking model uses the output from the hydrodynamic model to simulate the movement of particles released within the model domain. In Chapter 4, the hydrodynamic and particle tracking models are used to estimate the historical particle residence time in the Shark River Slough Estuary (SRSE) and determine the key factors controlling particle residence time and fate in mangrove estuaries. The mean and median residence times in the model domain are 16 and 8 hours, respectively, and 60% of all particles exit the model domain downstream, towards the Gulf of Mexico. Particle residence time varies greatly depending on the particle release location and timing. The residence time is significantly lower for particles released in the middle of the channel and for particles released during the wet season, spring tides or during upstream flows. Additionally, there is a decreasing trend in mean particle residence time from 1997 through 2017, mirroring an increasing trend in mean annual water levels in the SRSE. The combined results of this dissertation show the impact that a variable climate can have on stream flow and particle transport.
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Silva, Juliana Marques Valentim da. "Hydrodynamic effects in Ria de Aveiro and Tagus estuary salt marshes." Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/9687.
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Mestrado em Ciências do Mar e das Zonas CosteirasEnquanto áreas de transição, os sistemas costeiros apresentam uma enorme variedade e riqueza, proporcionando importantes atividades económicas e sociais. Atualmente, uma das ameaças a estes sistemas é o aumento do nível médio do mar, uma vez que o seu impacto poderá ter efeitos nos seus padrões hidrodinâmicos e, consequentemente, no seu valor ecológico e biológico. O estuário do Tejo e a Ria de Aveiro constituem dois dos sistemas costeiros mais importantes em Portugal. O estuário do Tejo é um dos maiores estuários da europa e é a zona húmida mais extensa do território português. Por sua vez, a Ria de Aveiro, é a mais extensa laguna do país e a mais dinâmica em termos de processos físicos e biogeoquímicos. Ambos apresentam extensas zonas de sapal, os quais representam um dos mais produtivos ecossistemas da biosfera. Os sapais são importantes áreas de interface entre a terra e o mar, fornecendo um habitat único para um vasto número de espécies, o que os torna num elemento fundamental na estrutura ecológica dos sistemas costeiros. No entanto, a interação de alguns aspetos físicos e biológicos bem como os efeitos do aumento do nível do mar, são ainda difíceis de explicar. Um dos objetivos deste estudo foi, recorrendo a um modelo numérico bidimensional, avaliar a influência de certos parâmetros hidrodinâmicos na dinâmica dos sapais do estuário do Tejo e da Ria de Aveiro, nomeadamente nas plantas de sapal, considerando quer o nível médio do mar atual quer um cenário de aumento do nível médio do mar. Os parâmetros hidrodinâmicos estudados foram a circulação residual, a assimetria de maré e a dissipação de energia. Para atingir estes objetivos, além de recorrer a simulações hidrodinâmicas, foi monitorizado um sapal de três em três meses em cada sistema durante um ano e amostras de sedimento e da planta Spartina maritima foram recolhidos para assim determinar a área de cobertura e a biomassa aérea e subterrânea da planta e a matéria orgânica e a humidade relativa do sedimento. Os resultados do modelo indicam que os parâmetros hidrodinâmicos em análise poderão explicar as diferentes características bióticas e abióticas que foram encontradas nos dois sapais, em resposta às diferentes condições hidrodinâmicas. Os resultados indicam ainda que o aumento do nível médio do mar poderá afetar significativamente a hidrodinâmica destes sistemas, mostrando como podem evoluir neste cenário. Adicionalmente, as alterações na hidrodinâmica poderão induzir modificações nos parâmetros bióticos e abióticos que, por sua vez, influenciam os sapais. Deste modo, o atual equilíbrio destes ecossistemas poderá ser afetado.
The importance of the coastal systems such as estuaries and lagoons has been recognized a long time ago. As interface areas, these systems are highly variable and rich, supporting important economic and social activities. The sea level rise impact in coastal systems is an important concern, once it might represent important effects in these systems hydrodynamics and consequently in theirs ecological and biological values. Two of the more important coastal system of Portugal are the Tagus estuary and the Ria de Aveiro lagoon. Tagus estuary is one of the largest estuaries of Europe and is the most extensive wetland area of Portuguese territory. Likewise, Ria de Aveiro lagoon is the most extensive shallow lagoon system in Portugal and the most dynamic in terms of physical and biogeochemical processes. Both systems have extensive intertidal areas, including salt marshes, which are among the most productive ecosystems of the biosphere. Salt marshes are a critical interface between land and sea, providing a unique habitat for a large number of species, being an essential element in coastal systems ecological structure. However, the knowledge of some physical and biological interactions within salt marshes, as well as sea level rise effects in these ecosystems, are still difficult to explain. One of the main goals of this work was to evaluate the influence of the hydrodynamic patterns of Tagus estuary and Ria de Aveiro lagoon in their salt marsh dynamics, namely, in salt marsh plants, considering the actual sea level and also the sea level rise (SLR), through the analysis of a 2D numerical model results. The hydrodynamic features that were considered usefull to this study were the residual circulation, tidal asymmetry and tidal dissipation. To reach these objectives, besides the hydrodynamic simulations, one salt marsh of each system was monitored during one year, and plant and sediment samples of Spartina maritima were colleted quaterly in order to determinate the vegetation coverage, above and belowground biomass, organic matter and sediment moisture. The model results suggest that the studied hydrodynamics parameters might explain the different characteristics of S.maritima found in the salt marshes, as a response to the difference hydrodynamic situations. Through the analysis of the model results, it was also intended to improve the knowledge about those hydrodynamic parameters in both systems and the possible effects of the SLR in their patterns. The SLR results indicate important differences, demonstrating how this estuaries hydrodynamics could evolve in case of sea level rising. Moreover, with the SLR and its effects in the hydrodynamic parameters, some abiotic features could be modified and, once salt marsh plants depend on them, their present status could be affected.
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Bacopoulos, Peter. "ANALYSIS, MODELING, AND SIMULATION OF THE TIDES IN THE LOXAHATCHEE RIVER ESTUARY (SOUTHEASTERN FLORIDA)." Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2584.
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Recent cooperative efforts between the University of Central Florida, the Florida Department of Environmental Protection, and the South Florida Water Management District explore the development of a two-dimensional, depth-integrated tidal model for the Loxahatchee River estuary (Southeastern Florida). Employing a large-domain approach (i.e., the Western North Atlantic Tidal model domain), two-dimensional tidal flows within the Loxahatchee River estuary are reproduced to provide: 1) recommendations for the domain extent of an integrated, surface/groundwater, three-dimensional model; 2) nearshore, harmonically decomposed, tidal elevation boundary conditions. Tidal simulations are performed using a two-dimensional, depth-integrated, finite element-based code for coastal and ocean circulation, ADCIRC-2DDI. Multiple variations of an unstructured, finite element mesh are applied to encompass the Loxahatchee River estuary and different spatial extents of the Atlantic Intracoastal Waterway (AIW). Phase and amplitude errors between model output and historical data are quantified at five locations within the Loxahatchee River estuary to emphasize the importance of including the AIW in the computational domain. In addition, velocity residuals are computed globally to reveal significantly different net circulation patterns within the Loxahatchee River estuary, as depending on the spatial coverage of the AIW.M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil Engineering
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Fiedler, Maria Fernanda Mendes. "Dinâmica estuarina em cenários de aumento do nível do mar: estuário de Santos, SP." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/21/21136/tde-26022016-144937/.
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Este trabalho teve como objetivo analisar os possíveis efeitos de um aumento do nível do mar no padrão de correntes no Sistema Estuarino de Santos (SP), através do uso do modelo hidrodinâmico do Delft3D-FLOW, considerando diferentes taxas de aumento de acordo com o quinto relatório do Intergovernmental Panel on Climate Change (AR5). Os resultados indicam alteração na velocidade da corrente ao longo do domínio implementado, mais evidente durante a sizígia. Observa-se um aumento da magnitude da corrente em praticamente todo o Canal de São Vicente e redução da magnitude nos canais do Porto de Santos, canal de Bertioga e na região interna do Estuário de Santos. Os resultados do modelo numérico foram comparados com diversos dados coletados na região de estudo e verificou-se a correta representação dos padrões de circulação da área. Este estudo comprovou a importância de utilizarmos resultados de um modelo de maior escala (HYCOM) como forçantes, através da condição de fronteira denominada Riemann, permitindo que o modelo represente fenômenos de baixa frequência, que geram circulações e variações do nível do mar com a mesma ordem de grandeza dos efeitos da maré astronômica na área de estudo.This study aimed to analyze the possible effects of a sea level rise in Sistema Estuarino de Santos (SP) circulation pattern, through the use of Delft3D-FLOW Hydrodynamic Model considering different elevation rates according to Intergovernmental Panel on Climate Change fifth report (AR5). The results indicate change in the current\'s magnitude, being more evident during the spring tide. There is an increase in the velocity practically all over São Vicente Channel and the reduction of magnitude in the Porto de Santos and Bertioga channels and in the inner region of the estuary. The numerical model results were compared with several measured data and it was verified that the model correctly representats the circulation patterns of the area. This study proved the importance of using results of a larger scale model (HYCOM), forced through a boundary condition called Riemann, allowing the model to represent low frequency phenomena, which generate sea level variations with the same order of magnitude of the effects of the astronomical tide in the study area.
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Heuner, Maike [Verfasser], Birgit [Akademischer Betreuer] Kleinschmit, Boris [Akademischer Betreuer] Schröder-Esselbach, Stijn [Akademischer Betreuer] Temmerman, and Reinhard [Gutachter] Hinkelmann. "Key ecosystem engineers in estuarine vegetation : their niches, traits, and services for coping with hydrodynamic stress / Maike Heuner ; Gutachter: Reinhard Hinkelmann ; Birgit Kleinschmit, Boris Schröder-Esselbach, Stijn Temmerman." Berlin : Technische Universität Berlin, 2016. http://d-nb.info/1156270472/34.
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Vennin, Arnaud. "Etude de l'interface eau-sédiment dans les géosystèmes estuariens : approche couplée biogéochimie et modélisation par l'évaluation des flux de nutriments (C,N,P)." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMR023/document.
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L’estuaire de Seine est un géosystème macrotidal présentant un hydrodynamisme fort lié à la combinaison des courants fluviatiles et tidaux. Ces phénomènes entrainent l’érosion et le dépôt des sédiments au niveau des vasières intertidales. Au sein des vasières, l’interface eau-sédiment est une zone importante car c’est à cet endroit que se réalise les échanges en nutriment (C, N, P) entre le sédiment et la colonne d’eau. L’objectif de cette thèse est d’évaluer l’impact des forçages hydrodynamiques, physiques et thermiques sur les flux de nutriment à cette interface en utilisant une double approche expérimentale de terrain et de modélisation. Dans ce but, une vasière d’embouchure et une vasière amont de l’estuaire sont échantillonnées au cours des mois de mars-avril 2017. Des échantillonneurs passifs ainsi que des instruments de mesure en continu sont implantés dans le sédiment. Les données obtenues sont ensuite intégrées en entrée dans des modèles de diffusion et d’advection afin d’estimer la contribution relative de la diffusion et des mouvements d’eau dans les flux de nutriment. Les résultats expérimentaux obtenus montrent les différences de fonctionnement hydrodynamiques des deux vasières du fait de leur localisation différente dans l’estuaire. Ils mettent aussi en avant l’hétérogénéité des sédiments des deux vasières d’un point de vue hydrodynamique, physique et biogéochimique. Enfin ils permettent de comprendre la dynamique de la température du sédiment en lien avec le cycle diurne et la marée. La partie modélisation de cette étude est divisée en deux parties distinctes : l’étude de la diffusion et de l’advection à l’interface eau-sédiment. La diffusion est étudiée de façon horizontale et verticale. Le facteur prépondérant de la dynamique de diffusion est la température, celle-ci est modulée par plusieurs paramètres. Les flux potentiels de diffusion sont aussi calculés pour les deux vasières. L’étude de l’advection au sein du sédiment est réalisée à l’aide de deux modèles : le modèle VFLUX et le modèle 1DTempPro. Les vitesses d’écoulement de l’eau interstitielle sont fonction du phasage-déphasage du cycle diurne avec celui de la marée. Ces résultats mettent en avant le rôle prédominant de l’advection par rapport à la diffusion dans la dynamique des flux de nutriment et permettent de proposer un modèle conceptuel des échanges thermiques et de l’advection-diffusion au sein des vasières intertidalesThe Seine estuary is a macrotidal geosystem with a strong hydrodynamism linked to the combination of fluvial and tidal currents. These phenomena cause erosion and sediment deposition on the intertidal mudflats. Within the mudflats, the water-sediment interface is an important area because it is there that nutrient exchanges (C, N, P) take place between the sediment and the water column. The objective of this thesis is to evaluate the impact of hydrodynamic, physical and thermal forcing on nutrient fluxes at this interface using a dual experimental field and modelling approach. For this purpose, a mudflat situated at the mouth of the river and an upstream mudflat of the estuary are sampled during the months of March-April 2017. Passive samplers and continuous measuring instruments are implanted in the sediment. The resulting data are then integrated into diffusion and advection models to estimate the relative contribution of water diffusion and movement in nutrient fluxes.The experimental results show differences in the hydrodynamic functioning of the two mudflats due to their different location in the estuary. They also highlight the heterogeneity of the sediments of the two mudflats from the hydrodynamic, physical and biogeochemical points of view. Finally, they allow us to understand the dynamics of sediment temperature in relation to the diurnal cycle and the tide. The modelling part of this study is divided into two distinct parts: the study of diffusion and advection at the water-sediment interface. The diffusion is studied in a horizontal and vertical direction. The main factor of diffusion dynamics is temperature, which is modulated by several parameters. The potential diffusion fluxes are also calculated for the two mudflats. The study of advection within the sediment is performed using two models: the VFLUX model and the 1DTempPro model. Interstitial water flow velocities are a function of the phase-diphase shift of the diurnal cycle with that of the tide. These results highlight the predominant role of advection compared to diffusion in the dynamics of nutrient flows and allow to propose a conceptual model of heat exchange and advection-diffusion within intertidal mudflats
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Lima, Edgar Barbosa. "Problemas inversos aplicados à identificação de parâmetros hidrodinâmicos de um modelo do estuário do rio Macaé." Universidade do Estado do Rio de Janeiro, 2012. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=3913.
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Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de JaneiroEsta tese tem por objetivo propor uma estratégia de obtenção automática de parâmetros hidrodinâmicos e de transporte através da solução de problemas inversos. A obtenção dos parâmetros de um modelo físico representa um dos principais problemas em sua calibração, e isso se deve em grande parte à dificuldade na medição em campo desses parâmetros. Em particular na modelagem de rios e estuários, a altura da rugosidade e o coeficiente de difusão turbulenta representam dois dos parâmetros com maior dificuldade de medição. Nesta tese é apresentada uma técnica automatizada de estimação desses parâmetros através deum problema inverso aplicado a um modelo do estuário do rio Macaé, localizado no norte do Rio de Janeiro. Para este estudo foi utilizada a plataforma MOHID, desenvolvida na Universidade Técnica de Lisboa, e que tem tido ampla aplicação na simulação de corpos hídricos. Foi realizada uma análise de sensibilidade das respostas do modelo com relação aos parâmetros de interesse. Verificou-se que a salinidade é uma variável sensível a ambos parâmetros. O problema inverso foi então resolvido utilizando vários métodos de otimização através do acoplamento da plataforma MOHID a códigos de otimização implementados em Fortran. O acoplamento foi realizado de forma a não alterar o código fonte do MOHID, possibilitando a utilização da ferramenta computacional aqui desenvolvida em qualquer versão dessa plataforma, bem como a sua alteração para o uso com outros simuladores. Os testes realizados confirmam a eficiência da técnica e apontam as melhores abordagens para uma rápida e precisa estimação dos parâmetros.
This thesis presents a strategy for automatically obtaining hydrodynamic and transport parameters by means of the solution of inverse problems. Obtaining the parameters of a physical model represents a major problem in its calibration, and this is largely due to the difficulty associated to the field measurements of these parameters. In particular by modeling rivers and estuaries, the roughness height and the turbulent diffusion coefficient represent two of the most difficult parameters to measure or estimate. Here, an automated technique for estimation of these parameters through an inverse problem is applied to a model of the Macaé estuary, located in northern Rio de Janeiro. For this investigation, hydrodynamic and transport models were built in the MOHID platform, developed in the Technical University of Lisbon, which has had wide application in simulation of water bodies. A sensitivity analysis was performed regarding the model responses with respect to the parameters of interest. It was verified that salinity is a sensitive variable for both parameters. The inverse problem was then solved using various optimization methods by coupling the MOHID platform to optimization codes implemented in Fortran. The coupling was carried in a way to not change the MOHID source code, allowing the use of the computational tool here developed in any version of this platform, as well as its modification for use with other simulators. The tests confirm the efficiency of the technique and suggest the best approaches for a fast and accurate estimation of the parameters.
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Chagas, Felipe Murai. "Dinâmica de ondas de areia na Baía de São Marcos (Ponta da Madeira/MA): observações e modelagem numérica." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/21/21136/tde-31032014-161956/.
Full textAbstract:
O objetivo deste estudo foi caracterizar a dinâmica das ondas de areia presentes no interior da Baía de São Marcos em São Luís, estado do Maranhão, utilizando dados de campanhas de batimetria bimestral e granulometria, para determinar a geomorfologia de fundo, além de séries temporais eulerianas de velocidade e variação da maré dos anos de 2011 e 2012 para validar um modelo hidrodinâmico local. O posicionamento horizontal e vertical nos conjuntos de dados batimétricos, digitalizados em transectos longitudinais, forneceu corredores de transporte que concordaram com os obtidos por meio do modelo numérico. Foram registradas ondas de areia com comprimento e altura superiores a 342 m e 6 m, respectivamente. A migração horizontal chegou a 1,8 m/dia e as intensidades de corrente a 1.84 m/s sobre o campo de ondas de areia e 2.58 m/s nos canais adjacentes. O Cabeço do Mearim e a Ilha do Medo são os principais responsáveis pela divisão dos regimes hidrodinâmicos locais forçados pela maré, os quais controlam os padrões morfológicos e migratórios das feições de fundo. Os mapas residuais de velocidade aliados aos coeficientes de dominância de maré calculados demonstraram que as principais forçantes do sistema são intensas nos canais e ao sul da Ilha do Medo e menos pronunciadas nas planícies rasas do sistema estuarino. As técnicas utilizadas neste estudo possibilitaram o estabelecimento de um modelo conceitual de corredores de transporte que rege o equilíbrio dinâmico do sistema local. Esses corredores são formados principalmente pelo canal principal da Baía de São Marcos localizado na porção oeste das feições submersas, predominando o transporte das correntes de vazante, pelo Canal do Boqueirão no qual predominam as correntes de maré enchente e pelo canal transversal situado a leste das ondas de areia, responsável por fluxos principalmente de maré enchente que podem transportar sedimentos ou energia para o sistema de canais principais. Este modelo forneceu conhecimento basal para o planejamento de atividades de uso, exploração e conservação dos sedimentos na Baía de São MarcosThe aim of this study was to characterize sand wave dynamics in São Marcos Bay (Maranhão state). Using data obtained from consecutive bathymetry campaigns, bottom sediment distribution, tide level and stationary current meters time series at this site from 2011-2012 years, bed morphology evolution was determined and a process-based hydrodynamic model was validated. Registering consecutive sand wave positioning in longitudinal transects provided bed features migration, generating transport pathways that agreed with model results. Sand waves observed were up to 6 m high and 342 m long and migrate up to 1.8 m/day, under depth-averaged current conditions up to 1.84 m/s above the sand wave field and 2.58 m/s in the adjacent channels. Cabeço do Mearim and Medo Island represents the features responsible for separate both tidal hydrodynamic regimes that control bottom migration and morphologic patterns. Residual current distribution and tide dominance coefficients showed that the controlling hydrodynamic forces of the system are more intense in the main channels and southward Medo Island, while weaken as depth reduces eastward. The methods used in this study provide a reliable conceptual model of transport pathways that control the local dynamic equilibrium, composed by the main channel of Sao Marcos Bay, where ebb dominance occurs, by the Boqueirão Channel strongly dominated by flood currents and by the transversal channel located eastward the bottom features, also flood dominated and responsible for transport sediment and energy to the sand wave field. This approach provided the bases for planning activities regard use, conservation and exploitation of sediments in São Marcos Bay
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Chahboun, Abderrahim. "Les formations sableuses fluviatiles, littorales et eoliennes aux embouchures des oueds tensift, ksob et souss (atlas-atlantique, maroc)." Paris 6, 1988. http://www.theses.fr/1988PA066131.
Full textAbstract:
L'etude des formations sableuses aux embouchures des oueds tensift, ksob et souss de l'atlas-atlantique (maroc) permet de mettre en evidence les processus de leur mise en place, ainsi que l'origine de leur materiel. Les oueds apportent jusqu'a l'ocean des elements terrigenes (quartz, feldspaths et mineraux lourds). Ces elements sont remanies et melanges aux depots marins. Le stock sedimentaire est redistribue par les actions marines, et principalement une forte derive littorale nord-sud. Ainsi, dans le systeme du tensift, le materiel dunaire evolue sous l'influence des alizes et des vents d'ouest, mais l'activite de ces derniers se revele plus efficace. Dans le systeme de ksob, le materiel dunaire evolue sous l'action principale des alizes. Dans le systeme du souss, la dynamique eolienne se fait sous l'action conjuguee des alizes et des vents d'ouest. Ces evolutions sedimentaires se traduisent par une amelioration du tri, une diminution progressive du grain moyen et des teneurs en carbonates et mineraux lourds, ainsi que par une eolisation croissante des grains quartz.
34
Ke, Min-Hsin, and 柯旻欣. "Influence of geomorphic change on hydrodynamics and salt transport in tidal estuarine system." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/362kr8.
Full textAbstract:
碩士國立聯合大學
土木與防災工程學系碩士班
106
Geomorphic change is one of important factors to affect the hydrodynamics in an estuary, and this also affects salt transport and, thereby, the distribution and salt intrusion. The Danshui River passes through the Taipei city, which is the area with high population density and the center of government and economy. Therefore, the water uses and the geomorphic changes of the estuarine system of the Danshui River have been noticed. In this study, a three-dimensional hydrodynamic and salt transport model was used to simulate hydraulic characteristics and salt transport of the estuarine system of Danshui River. After the model calibration and validation, the model was applied to explore the effects of geomorphic change on hydraulic characteristics, e.g., tidal prism, residence time, and plume, in the Danshui River estuarine system in 1981 and 2015, respectively. In terms of calibration and validation of hydrodynamic model, the measured data of the water level, tidal current, and salinity in 2015, 2016, and 2017 were compared with model predictions. The results of the calibration and validation for the water level show that the values of skill score were between 0.830 (excellent) and 0.999 (excellent); besides, the tidal currents illustrate the values of skill score were between 0.341 (good) and 0.957 (excellent), and those for salinity indicate the values of skill score were between 0.313 (good) and 0.955 (excellent). Based on the results of model calibration and validation, the model simulations reproduce the measured data. The validated model was then used to explore the effects of geomorphic change on hydraulic characteristics in the Danshui River estuarine system. The results indicate that the time series of water level, tidal current, and salinity of Danshui River estuarine system in 1981 and 2015 (present), respectively, were affected by geomorphic changes; also, there were time lag and the change of tidal range. Considering the effects of geomorphic changes on salt intrusion, the results reveal that, in Danshui River-Dahan Stream and Hsintien Stream, the distances of salt intrusion in 2015 were shorter than those in 1981, while, in Keelung River, the distance of salt intrusion in 2015 was farther up-river than that in 1981. Concerning the effects of geomorphic changes on tidal prism, the results show that, in the Danshui River estuarine system, the tidal prism in 2015 was less that in 1981. Accordingly, it indicates that Danshui River’s channel was influenced by the geomorphic changes. In the estuary, the volume of outflow during ebb tides in 2015 was less than that in 1981. In terms of the effects of geomorphic changes on residence time, in this study, the residence time of the Danshui River estuarine system was calculated using the theories of Sanford et al. (1992) and Luketina (1998). The results show that the residence time in 2015 was less than that in 1981. Namely, the time that pollutants stayed in the Danshuei River estuarine system in 2015 was shorter than that in 1981. In addition, the model was applied to explore the effects of geomorphic change on the plume of the coast. The results indicate that the plume distance in 2015 was farther than that in 1981; hence, it indicates that, in 2015, the degree of pollution diffusion in the adjacent coastal area of Danshuei River was better.
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Vaz, Leandro Alves. "Optimization of estuarine aquaculture exploitation: modelling approach." Doctoral thesis, 2020. http://hdl.handle.net/10773/30411.
Full textAbstract:
Aquaculture is one of the fastest growing activities worldwide. In 2006, it already
accounted for around 40% of total fish consumption, and since 2012, aquaculture is the main source of marine food supplies. However, this strong and fast
development of the sector tends to be reflected in significant environmental impacts and new challenges in the management and planning of the coastal areas.
In this context, this work intends to contribute to the sustainability of the sector,
by identifying preferential locations to ensure aquaculture expansion and proper
operation in a sustainable manner and with minimal environmental impact under
optimal hydrodynamic and water quality conditions in Ria de Aveiro (Portugal)
and Rias Baixas (Spain). This study is particularly relevant because the mapping
of the most suitable areas for aquaculture exploitation has never been performed
in any of the study areas, proving to be crucial, not only to demonstrate the potential in this commercial activity and to encourage investment by companies, but
mainly to enable an adequate targeting of investments. To achieve this objective,
a multidisciplinary methodology was applied, which comprised the following steps:
1 - characterization of hydrodynamic, physical, chemical and biological variables
governing aquaculture activities; 2 - implementation, calibration, validation and
exploitation of hydrodynamic and water quality models; 3 - development of a habitat model integrating the numerical model results into an exploitation index; 4 -
application of a habitat model and mapping of the suitable and unsuitable areas for
fish and shellfish exploitation in Ria de Aveiro and Rias Baixas. The results show
that 22% of Ria de Aveiro is suitable for fish production (axis of the main channels,
from the inlet to the middle of the channels), while the production of pelagic fish
in the Rias Baixas is not recommended due to vertical gradients of water temperature and dissolved oxygen. Concerning to bivalves, the habitat model predicts
that 31% of Ria de Aveiro is suitable for production. In the Rias Baixas, except
for some marginal areas and upstream areas, the suitability for bivalve production
is almost complete, confirming the high exploitation of the region. The definition
of suitable areas for aquaculture exploitation is highly related with the different
geomorphological, hydrological and biogeochemical processes of Ria de Aveiro and
Rias Baixas, but also with the vertical structure of the estuarine systems: homogeneous water column (Ria de Aveiro) in opposition to a partially mixed estuarine
system (Rias Baixas). Results of Ria de Aveiro indicate that the upstream areas
of the lagoon are the most vulnerable from the water quality point of view, highlighting the importance of the advective processes in the lagoon’s water quality, in
opposition to Rias Baixas dynamics, where stratification is more relevant. In Rias
Baixas, the strong vertical gradient of water temperature and dissolved oxygen
disallows fish from having sustainable growth rates.
The numerical modelling approach combined with a habitat model allowed to
consider a large number of variables, integrating them in order to generate results
that are very useful for coastal managers and investors. Therefore, this work shows
that the methodology developed here is effective for the identification of favorable
areas for the exploitation of species with economic interest, generating a tool
that can be replicated and/or adapted in future studies in other coastal systems.
Finally, this work demonstrated the potential of hydrodynamic and biogeochemical
modelling to support the decision making process in future coastal plans.A aquacultura é uma das atividades económicas com maior taxa de crescimento. Em 2006, já era responsável por cerca de 40% do consumo total de peixe, e em 2012, consolidou-se como a principal fonte de alimentos de origem marinha. Contudo, este forte e rápido desenvolvimento do setor tende a refletir-se em significativos impactos ambientais, e em novos desafios na gestão e planeamento das zonas costeiras. Neste contexto, este trabalho pretende contribuir para a sustentabilidade do sector, identificando locais preferenciais para a exploração aquícola de forma sustentável, com um impacto ambiental mínimo e um custo relativamente baixo, sob condições ideais de hidrodinâmica e qualidade da água na Ria de Aveiro (Portugal) e Rias Baixas (Espanha), os dois sistemas com maior exploração no NW da Península Ibérica. Este estudo torna-se particularmente relevante porque o mapeamento das localizações mais adequadas à exploração aquícola nunca foi efetuado em nenhuma das áreas de estudo, revelando-se fulcral, não só para demonstrar o potencial da atividade comercial e incentivar o investimento das empresas, mas principalmente para permitir um direcionamento adequado dos investimentos, e contribuir para a sustentabilidade do setor. Para alcançar este objetivo foi aplicada uma metodologia multidisciplinar que compreendeu a realização dos seguintes passos: 1 - caracterização das variáveis hidrodinâmicas, físicas, químicas e biológicas importantes para a aquacultura; 2 - implementação, calibração, validação e aplicação de modelos hidrodinâmicos e de qualidade da água; 3 - desenvolvimento de um modelo de habitat, para transformação dos resultados dos modelos numéricos, num índice de exploração; 4 - aplicação do modelo de habitat, e mapeamento das zonas mais adequados à exploração de peixes e bivalves na Ria de Aveiro e Rias Baixas. Os resultados evidenciam que 22% da Ria de Aveiro é adequada para a produção de peixes (eixo dos principais canais, desde a embocadura até à zona intermédia dos canais), enquanto que a produção de peixes pelágicos nas Rias Baixas não é aconselhável, devido aos gradientes verticais de temperatura da água e de oxigénio dissolvido. Relativamente aos bivalves, o modelo de habitat prevê que 31% da Ria de Aveiro é adequada à sua produção. Nas Rias Baixas, exceptuando algumas zonas marginais e perto das cabeceiras, a adequabilidade para a produção de bivalves é quase total, confirmando a elevada exploração que se verifica na região. A definição das áreas propícias para a exploração aquícola está altamente relacionada com os diferentes processos geomorfológicos, hidrológicos e biogeoquímicos que ocorrem na Ria de Aveiro e nas Rias Baixas, mas também com a estrutura vertical dos sistemas estuarinos: uma coluna de água homogénea (Ria de Aveiro) em oposição a um sistema estuarino parcialmente estratificado (Rias Baixas). Os resultados para a Ria de Aveiro indicam que as cabeceiras dos principais canais são as áreas mais vulneráveis do ponto de vista da qualidade da água, evidenciando a importância da adveção nos processos ecológicos, em oposição à dinâmica das Rias Baixas, onde a estratificação adquire maior relevância. Nestes estuários, o forte gradiente vertical da temperatura da água e do oxigénio dissolvido impede que os peixes possuam taxas de crescimento sustentáveis. A abordagem de modelação numérica combinada com um modelo de habitat permitiu considerar um elevado número de variáveis, integrando-as de forma a gerar resultados de grande utilidade para gestores e investidores do setor aquícola. Consequentemente, este trabalho mostra que a metodologia aqui desenvolvida é eficaz para a identificação de locais propícios para a exploração de espécies de interesse económico, gerando uma ferramenta que pode ser replicada e/ou adaptada em estudos futuros a realizar noutros sistemas costeiros. Finalmente, este trabalho demonstrou o potencial da modelação hidrodinâmica e biogeoquímica no suporte ao processo de tomada de decisão em futuros planos de ordenamento das zonas costeiras.
Programa Doutoral em Ciência, Tecnologia e Gestão do Mar
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Jaaback, Kathryn Margaret. "A two-dimensional hydrodynamic model for the St Lucia Estuary mouth." Thesis, 1993. http://hdl.handle.net/10413/5907.
Full textAbstract:
The reduced fresh water input into the St Lucia Estuary combined with the increase
of sediment in the St Lucia Lake System has necessitated the implementation of a
dredging programme. To ensure the effectiveness of the dredging programme, the
behaviour of the sediment under various flow and tidal conditions needs to be
determined.
To establish how sediment will move, it is necessary to understand the hydrodynamics
of the estuary. To achieve this, a hydrodynamic model which can be linked to a
sediment transport model needs to be developed. Various existing types of
hydrodynamic and sediment transport models are reviewed, to determine their
suitability for the above purpose. Results of the analysis indicate that a two-dimensional
hydrodynamic model is required.
The two-dimensional hydrodynamic model developed is based on the momentum and
continuity equations for an unsteady, non-uniform, free-surface flow for an
incompressible fluid. The two dimensions are in the horizontal plane and flow is
averaged over the depth. The equations are non-linear and are not decoupled, thus
a numerical technique was needed to solve them. An Alternating Direction Implicit
technique has been used. Boundary conditions in the modelled region were specified
as flow velocity at the upstream boundary, and water levels, relative to the Mean
Lake Level, at the downstream boundary.
Two short simulations using hypothetical data were run on a 80826 IBM compatible.
Results of the simulation indicate two areas where irregularities in the model output
are a consequence of the use of hypothetical data in defining the boundary conditions.
Recommendations for the collection of data in order to improve and calibrate the
model are discussed.Thesis (M.Sc.)-University of Natal, 1993.
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Tseng, Yao-Pin, and 曾耀彬. "Development and Application of A Hydrodynamic in Estuarine Network System." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/35296608485216776252.
Full textAbstract:
碩士國立臺灣大學
生物環境系統工程學研究所
92
Taiwan is an island surrounded by the ocean. The rivers mostly run down steep slopes with high speed. Most of them flow into the ocean finally. The downstream estuaries or tidal-affected parts of rivers have become an essential passageway for the transmission and interchange of water and substances between rivers and oceans. Thus, multiple pollution problems derived, which have caused serious harm and pollution to the local water quality and ecology. Regarding this phenomenon, it is necessary to understand the hydrodynamic condition in this section of the river and to simulate the transmission and interchange process of polluted substances in the water so that the most appropriate plan and arrangement for estuarine ecological environment can be made. This study mainly aims at the important hydrodynamic phenomena of estuarine areas and to fully understand their hydrodynamic characteristics. The simulation research must be achieved with the aid of a proper hydrodynamic numerical model. Most of the existing numerical models applying estuarine areas are only suitable in situations like single channels, single estuaries, or in simulating the converging and diverging situations of main streams and tributaries. However, they still have slight differences from the natural river network. Therefore, this study chiefly focuses on the expansion and improvement of such deficiencies based on a vertical two-dimensional numerical model to include the capability of simulating diversion as well as confluence. It will be modified to enable simulating multiple estuarine conditions; and this model will become a multi-functional hydrodynamic numerical model for complex river networks. After the expansion of this model, this study has designed a few testing programs to verify the overall rationality and accuracy of the model before and after expansion. It has also further analyzed the flow situation of multi-estuarine river courses to see if it corresponds to the theory. All results of simulation are perfectly reasonable. This research will apply the model to the TanShui River estuarine system and hypothesize its characteristic of multiple estuaries to investigate the influence on the overall flowing situation of river networks after increasing multi-estuarine river courses.
38
Liu, Wen-Cheng, and 柳文成. "Modelung Study on Dynamic Transport of Hydrodynamic and Water Quality in Tidal Estuarine System." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/87675413900581531811.
Full textAbstract:
博士國立臺灣大學
農業工程學研究所
87
The estuary, together with the tidal freshwater river upstream of it, is the pathway for exchange of water and materials between its drainage basin and coastal ocean. To predict the fate and transport of materials from land to ocean, it is essential to understand the hydrodynamic characteristics of this stretch of the river. This study investigates the major components of water movement in the estuarine system : tidal flow, freshwater river flow and estuarine (or residual) circulation. The longitudinal and vertical salinity distributions are also investigated as a forcing function of, as well as a response to, the estuarine circulation. The purposes of this study are to develop a vertical two-dimensional numerical model which includes the capability to model tributaries and to study the hydrodynamic and water quality characteristics of estuarine system. The hydrodynamic model is based on the principles of conservation of volume, momentum and mass, and the water quality model on the conservation of mass alone. The flow conditions at the confluences of mainstem and tributaries are solved by expanded continuity, momentum and mass-balance equations. After model development, the numerical model is applied to investigate the Tanshui River system, the largest estuarine system in Taiwan with drainage basin including the capital city of Taipei. It consists of three major tributaries : the Tahan Stream, Hsintien Stream and Keelung River. The study investigates the hydrodynamic characteristics of the tidal reaches of the river system by means of theoretical analysis and numerical simulation. The model is calibrated and verified with observational field data. The calibrated and verified parameters include Manning* friction coefficient, the coefficients in turbulence diffusion terms and the coefficients of eight-water quality state variables. As examples of model utilities, the calibrated and verified model is used to investigate the tidal flow and salinity conditions in the Tanshui estuarine system and its estuarine wetland under the conditions with and without Kuan-Du dike. The model is also used to compute the salinity distributions and to predict future water quality conditions under several scenarios of wastewater diversion and under various hydrological conditions. The results show that the model has potential for more general diagnostic applications and prediction of pollutant transport and fate. It also can be used as an aid for making waste load allocations, management decisions and environmental impact analyses.
39
Zietsman, Ingrid. "Hydrodynamics of temporary open estuaries, with case studies of Mhlanga and Mdloti." Thesis, 2004. http://hdl.handle.net/10413/4342.
Full textAbstract:
Estuaries are unique coastal bodies of water where water derived from land meets the sea. In order to preserve estuaries and minimise the effects of human interference in these sensitive areas, an understanding of the hydrodynamics is essential. South Africa has 259 estuaries, of which approximately 70% are temporary open. The aim of the project was to provide data to analyse the effect of different flow scenarios on the frequency, timing and duration of mouth closure for temporary open estuaries. To achieve the project aim, two case studies were undertaken, namely Mhlanga and Mdloti Estuaries. Achieving the terms of reference required monitoring of the mouth state, water level, flow rates and developing an understanding of breaching mechanisms. Observations of the mouth were
used to monitor its state and initially photographs were used to monitor the water level within each estuary. During 2003 a continuous water level monitor was developed and placed in each estuary. Velocity readings were taken upstream of the estuaries at discrete time intervals and
converted to flow rates using the velocity area method. A photographic survey of the berm at Mhlanga Estuary was used to observe the effect of beach processes on the mouth area. The survey observed the estuary as it shifted from closed through to open, then partially open and
finally closed again, providing information on mouth mechanisms. The continuous water level monitoring provides useful information for Mhlanga Estuary in terms of breaching patterns, tidal exchange when in the open state and an indication of the time scales involved in mechanisms which change the mouth state. Similar information for Mdloti
Estuary was not available as the estuary did not breach since the installation of the water level monitors, however salinity profiles from 2002 provided qualitative information on the existence of a saline intrusion into the estuary. The relationship between flow and mouth state is complex and relies on other influences such as water level and systems losses. In general estuaries will breach under high flows and remain closed under low flows, however in between these two regimes the estuary mouth state is less predictable based on flow alone. Mhlanga Estuary repeatedly breached at low tide. During the open phase tidal influence was both observed and captured by water level monitors despite the perched nature of the estuary. Closure generally occurred at high tide trapping saline water
within the estuary. The two case studies provided a good basis for exploring the affects of different flow conditions on estuaries, with Mdloti Estuary experiencing the effects of the
Hazelmere Dam and abstractions, while Mhlanga Estuary has increased flow due to the discharge of treated effluent to the system.Thesis (M.Sc.Eng.)-University of Natal, Durban, 2004.
40
Chen, Wei-Bo, and 陳偉柏. "Implementation and Development of Three-dimensional Hydrodynamic and Suspended Sediment Transport Model for Estuarine System and Its Adjacent Coastal Sea." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/87865220710622676271.
Full textAbstract:
博士國立臺灣大學
生物環境系統工程學研究所
100
Estuaries are coastal waters where the mouth of the river meets the ocean and where the freshwater of the river mixes with the saline water from the ocean, and represent the complex nonlinear interaction of tides, current, salt, water and suspended sediment. The primary factors controlling transport processes in estuaries are tides and freshwater from upstream. Hydrodynamic processes in estuaries are generally three-dimensional; hence, implementation of the three-dimensional model for estuarine system is imperative. In the present study, a three-dimensional hydrodynamic model incorporating suspended sediment module was developed and applied to the Danshuei River estuarine system and its adjacent coastal sea. The model was calibrated with measured water surface elevation, tidal current, salinity and suspended sediment concentration (SSC). The overall model simulation results are in qualitative accordance with the available field data. The validated model was then adopted to investigate the physical properties of the Danshuei River estuary. The vertical profiles of salinity, velocity, and eddy diffusivity show a marked asymmetry between the flood and ebb tides; moreover, the tidal currents, turbulent mixing and vertical stratification show large fortnightly fluctuations over the spring-neap cycle. The circulation strengths were stronger during the neap tides than during the spring tides. The Eulerian transport is always seaward, whereas the Stokes transport is the main mechanism driving the up-estuary. According to the numerical experiments, the residence time is less than three days under mean flow conditions and the density-induced circulation play an accelerating role for mass transport. The particle-tracking model indicates that the water ages were approximately 320, 100 and 485 hours at the mouths of the Danshuei River-Tahan Stream, the Hsintien Stream and the Keelung River under the Q60 flow condition. Particles released experiments show that compare to the tidal current, wind influences were insignificant in the river channel. However, particle distribution was affected by density-induced circulation. The trajectories of oil spill were sensitivity to the leaking timing and wind direction, no matter oil spill even occurred in the river channel or harbor, because the oil particles always drift on the water surface. The estuarine turbidity maximum appears around Kuan-Du Bridge, it may be due to the high bottom stress and deeper topography there. The SSC has slight raise with increasing turbulent eddy diffusivities but significant increase with high freshwater discharge. The SSC is over 1.5 times higher at spring tide than that at neap tide. The estuarine turbidity maximum extends its range from 7.0~12.0km to 7.0~16.0km (distance from the Danshuei River mouth) under the condition of bathymetric change.