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This paper investigates the effect of natural and artificial morphological changes in a tidal inlet on the tidal propagation and on the water exchanges with the sea, through data analysis and numerical modeling. Bathymetric and tidal data reveal a strong seasonal signal, as a result of the changes in the relative importance of tidal and wave action: during the maritime winter the M2 tidal amplitude decreases by 50% and flood dominance increases. This trend is reverted during maritime summer, and tidal amplitudes can be further enhanced by dredging of the inlet. Hydrodynamic and residence time (RT) simulations were set up for three different bathymetric configurations of the lower lagoon, representative of distinct situations. Hydrodynamic results confirmed that tidal propagation depends strongly on the bathymetric configuration. At the transitions between channels, tidal energy losses occur and flood dominance increases. Dredging the channels and repositioning the inlet throat improve tidal propagation and promote sediment flushing to the sea. The spatial variability of RTs was evaluated through the integration of individual particle results in morphologically relevant units, while time variability was examined within the tidal and neap/spring cycles. Residence times depend heavily on the morphological changes associated with both dredging operations and inlet migration, and on the particle release time, both within the tidal cycle and within neap/spring cycles. The relative importance of each of these factors depends on the particle location within the lagoon. The upstream regions of the lagoon have very large RTs (years), as a result of the small tidal amplitudes and velocities. In some of these regions, RTs vary by a factor of 4 depending on the bathymetry of the inlet. In the lower lagoon, tidal amplitude also has a significant effect on RTs. Dredging the channels and repositioning the inlet throat from the southern margin to a central position improves the flushing of both southern and northern channels. ****** 917-942 ****** ******

Due to the increasing sand demand for construction and beach nourishment, offshore extraction is being considered as an alternative source. Long term morphological changes caused by such an extraction must be predicted because they can affect the sediments budget and potentially promote coastal erosion. Numerical models are powerful tools that can help in the evaluation of environmental impacts induced by this activity. They should, however, be used with caution, the validation of a particular model being an important task. The objective of this study is to describe the hydrodynamics in the area surrounding a sandpit through the use of numerical models, namely ELCIRC for the tidal flow and SWAN for the waves. The sandpit under study is located offshore Vale do Lobo, an important beach and golf resort located on the Southern Portuguese coast. A wave climate analysis was done in order to assess mean wave conditions and to choose extreme events to propagate with SWAN. Four wave conditions were identified as representative. The numerical results obtained show that the tidal flow and the orbital wave velocities within the pit and neighbouring areas are modified by the presence of the pit. The excavation influences the tidal flow in an area of approximately 3000 * 3000 m2 around it. In this area the maximum velocity increase is of 2%, occurring in the nearby surroundings of the pit, and the maximum decrease is of 16%, in the pit deepest zone. The orbital velocities for the storm wave conditions show a decrease of 15% within the pit and its influence extends up to the 4 m contour, not reaching the shore. 529-533 SI 56

Descreve-se um modelo de transporte para sistemas costeiros, particularmente apropriado em situações de fortes gradientes de concentração. Este modelo baseia-se numa formulação Euleriana-Lagrangiana para malhas não-estruturadas e apresenta as seguintes características: 1) discretização por volumes finitos e tracking de elevada precisão; 2) malhas distintas para o escoamento e transporte; 3) use da técnica de flux-corrected transporte ou de filtro não-linear para remoção de oscilações. Analisam-se as propriedades numéricas através da análise do erro de truncatura e de um teste numérico. A combinação de várias técnicas numéricas permite obter estabilidade incondicional, conservação de massa e elevada precisão, evitando simultaneamente oscilações numéricas. Palavras-Chave: Volumes finitos; métodos Eulerianos-Lagrangianos; oscilações numéricas. ****** 94-101 3/2 ****** ******

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Hydrodynamics, salinity intrusion and stratification in the Guadiana estuary were characterized using two- and three-dimensional models for fresh water flows covering the range of monthly averaged river flows for dry to wet years. Two- and three-dimensional circulation model results were then used to investigate the flushing properties of the lower estuary for passive organisms and for organisms with vertical migration capabilities, respectively. Stratification can occur in the Guadiana estuary for river flows as small as 10 m3 s−1, depending on the tidal amplitude. For homogeneous or weakly stratified conditions, salinity can be found upstream of Alcoutim (km 40) during neap tides, and extends even further for spring tides. For a river flow of 10 m3 s−1, euhaline conditions reach 25 km upstream of the mouth during spring tides. For larger river flows, the region under stratified conditions is located in the downstream 10 km, and its extent depends mainly on the tidal phase. For river flows between 50 and 300 m3 s−1, salinity intrusion does not extend beyond km 20. As the river flow increases, the upper limits of the several haline regions approach one another, creating a lower estuary where salinity conditions have a wide range of horizontal variability. Residence times of passive organisms in the lower Guadiana estuary depend on the magnitude of the river flow, tides and other mechanisms, varying from a few hours to 60 days in the range of river flows considered. The variability of residence times with different environmental conditions is similar for all river flows, the upper limit of residence times being about one order of magnitude larger than the lower limit. For river flows above 200 m3 s−1, both limits of residence times are small (from a few hours to a few days), showing the dominant role of river flow in these conditions. However, active organisms, with vertical migration capabilities, can remain inside the Guadiana estuary under strong river flows, by taking advantage of the phase lag along the vertical profiles of velocity under stratified conditions. Permanence conditions improve for organisms located in the main channel, due to the larger stratification in deeper areas. The tidal amplitude also plays an important role, spring tides being more favourable to permanence than neap tides.

Este registo pertence ao Repositório Científico do LNEC We present an extensive formal and experimental comparison of the accuracy and stability of selected finite-element Eulerian-Lagrangian methods (FE-ELMs) for the solution of the 1D transport equation. The comparison shows that recent FE-ELMs that use the perspective of integration (rather than the more conventional perspective of interpolation) to treat initial conditions at the feet of the characteristic lines have excelent accuracy properties. Although some "integration" FE-ELMs are only conditionally stable, the associated constraints are expected to be minor for most applications of interest. Motivation for the comparison was motivated by the on-going development of a new generation of multi-dimensional Eulerian-Lagrangian water quality models, oriented towards surface water applications, and addressing tracers with increasingly complex chemical and biological pathways. While this motivation may appear remote for a theoretical study of numerical methods, the need for the information now generated is strong, and the practical contributions are significant. Indeed, the need stems from the fear (partly rooted in accummulated experience) that complex water quality models may magnify remaining shortcomings in fundamental aspects of the solution of the transport equation, such as stability, mass conservation, and ability to accurately transport sharp gradients of concentration. Pratical contributions include: * the recommendation to initiate the systematic replacement of "interpolation" FE-ELMs by "integration" FE-ELMs, as the reference strategy to solve for hydraulic transport in the family of ELA water quality models (ELA, ELAcol, ELAsed, ELAmet, etc.); * the development of basic data and understanding necessary for the informed use of "integration" FE-ELMs; an example is the development of basic data necessary to drive the semi-automatic generation of finite element grids taylor-made for the simulation of transport processes by "integration" FE-ELMs. Key Words: Transport equation. Eulerian-Lagrangian methods. Stability analysis. Accuracy analysis. Numerical experimentation. ****** ****** ****** ****** ******

The dynamics of the Aveiro lagoon is assessed through a combination of field data and numerical modeling. An unstructured grid hydrodynamic model is set-up for this system for the first time and its results compare well with data and with a wellestablished model. The model and the data are then used to analyze the propagation of the tide in the lagoon and the variability of tidal asymmetry in the upper and lower lagoon. The lagoon shifts from mild ebb-dominance at the inlet to strong flooddominance in the upper lagoon. This variability may be responsible for the importing capacity suggested by the sediment particle model, estimated at 10% of the littoral drift. On the contrary, a preliminary application of the morphodynamics modeling system MORSYS2D suggests a net export capacity. These opposite results maybe due to the tidal excursion of sediments in the system, which is much larger than the scale of variability of the hydrodynamics.

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Este registo pertence ao Repositório Científico do LNEC Submitted by Mário Jorge Martins Pereira (majo@lnec.pt) on 2010-06-22T14:05:00Z No. of bitstreams: 1 Rel 194_10.pdf: 4514519 bytes, checksum: c3561dc88eace60acd98eb2fd34bd159 (MD5) Made available in DSpace on 2010-06-22T14:05:00Z (GMT). No. of bitstreams: 1 Rel 194_10.pdf: 4514519 bytes, checksum: c3561dc88eace60acd98eb2fd34bd159 (MD5) Previous issue date: 2010-05 Made available in DSpace on 2014-10-20T12:44:38Z (GMT). No. of bitstreams: 2 license.txt: 1843 bytes, checksum: 02b99849d5cb3f58b5fbda0c38678a17 (MD5) Rel 194_10.pdf: 4514519 bytes, checksum: c3561dc88eace60acd98eb2fd34bd159 (MD5) Previous issue date: 2010-05 14 1 27pp Projecto FCT GCAST – G-cast: Application of GRID-computing in a coastal morphodynamics nowcast-forecast system (ref: GRID/GRI/81733/2006) / NÃO CONFIDENCIAL 1945 - arquivado na SE do DHA DHA/NEC

The economical and ecological importance of tidal inlets have fostered the development of empirical tools for inlet management during the last century. This study aims at confronting these empirical theories with recent process-based numerical models. The 2DH process-based morphodynamic modeling system MORSYS2D is applied to an idealized tidal inlet/lagoon system with six different combinations of significant wave height, tidal range and tidal prism. The model predictions are compared to natural morphologies and then to the empirical models of Hayes, O’Brien and FitzGerald. The results present good accordance with observation as well as with some key behaviors predicted with the empirical theories. The predicted morphologies satisfy the relation of O’Brien between the tidal prism and crosssectional area, model results reproduce the conceptual model of sand by-passing of FitzGerald and the energetic classification of Hayes is partly respected. However some inconsistencies between model results and Hayes prediction appears, which highlights the limitations of the classification, that only considers the yearly-averaged significant wave height and tidal range. 22-23 septembre 2009

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This work describes the application of hydrodynamic (ELCIRC) and transport (VELA and VELApart) models to the Ria Formosa lagoon (Portugal) to study the impact of the relocation of the Ancão Inlet. Located in the south of Portugal, this lagoon is a mesotidal barrier island system that communicates with the sea through 6 inlets. The Old Ancão Inlet was artificially closed and the New Ancão Inlet was relocated into a westward position. This work investigates the hydrodynamic patterns and the potential pathways of tracers in Ria Formosa in two distinct configurations: before and after the Ancão Inlet relocation. The hydrodynamic model was successfully calibrated and validated against elevation, velocity and inlet discharges data, accurately reproducing the tidal propagation. The inlet relocation increases the magnitude of tidal currents, residual velocities and the tidal prism across the bar, suggesting a better stability. The tracers transport simulations suggest enhanced water exchanges through the Ancão Inlet and smaller residence times in the western part of Ria Formosa with the present configuration. Overall, it is concluded that the Ancão Inlet relocation had a positive contribution towards increasing the water renewal of the western part of the lagoon, thus decreasing its vulnerability to pollution 711–725 24

A flexible 2D/3D oil spill modeling system addressing the distinct nature of the surface and water column fluids, major oil weathering and improved retention/reposition processes in coastal zones is presented. The system integrates hydrodynamic, transport and oil weathering modules, which can be combined to offer different-complexity descriptions as required by applications across the river-to-ocean continuum. Features include accounting for different composition and reology in the surface and water column mixtures, as well as spreading, evaporation, water-in-oil emulsification, shoreline retention, dispersion and dissolution. The use of unstructured grids provides flexibility and efficiency in handling spills in complex geometries and across scales. The use of high-order Eulerian–Lagrangian methods allows for computational efficiency and for handling key processes in ways consistent with their distinct mathematical nature and time scales. The modeling system is tested through a suite of synthetic, laboratory and realistic- domain benchmarks, which demonstrate robust handling of key processes and of 2D/3D couplings. The application of the modeling system to a spill scenario at the entrance of a port in a coastal lagoon illustrates the power of the approach to represent spills that occur in coastal regions with complex boundaries and bathymetry. 132-147pp Volume 80, Issues 1–2 DHA/NEC Marine Pollution Bulletin

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Like other similar coastal systems, the Albufeira lagoon is artificially opened every year to promote water renewal and closes naturally within a few months. The evolution of the Albufeira Lagoon Inlet from its opening in April 2010 to its closure 8 months later is qualitatively and quantitatively analyzed through a combination of monthly field surveys and the application of a process-based morphodynamic model. Field data alone would not cover the whole space–time domain of the morphology of the inlet during its life time, whereas the morphodynamic model alone cannot reliably simulate the morphological development. Using a nudging technique introduced herein, this problem is overcome and a reliable and complete data set is generated for describing the morphological development of the tidal inlet. The new technique is shown to be a good alternative to extensive model calibration, as it can drastically improve the model performance. Results reveal that the lagoon imported sediments during its life span. However, the whole system (lagoon plus littoral barrier) actually lost sediments to the sea. This behavior is partly attributed to the modulation of tidal asymmetry by the spring–neap cycle, which reduces flood dominance on spring tides. Results also allowed the assessment of the relationship between the spring tidal prism and the cross-section of tidal inlets (the PA relationship). While this relationship is well established from empirical, theoretical and numerical evidences, its validity in inlets that are small or away from equilibrium was unclear. Results for the Albufeira lagoon reveal an excellent match between the new data and the empirical PA relationship derived for larger inlets and equilibrium conditions, supporting the validity of the relationship beyond its original scope.

A flexible 2D/3D oil spill modeling system addressing the distinct nature of the surface and water column fluids, major oil weathering and improved retention/reposition processes in coastal zones is presented. The system integrates hydrodynamic, transport and oil weathering modules, which can be combined to offer different-complexity descriptions as required by applications across the river-to-ocean continuum. Features include accounting for different composition and reology in the surface and water column mixtures, as well as spreading, evaporation, water-in-oil emulsification, shoreline retention, dispersion and dissolution. The use of unstructured grids provides flexibility and efficiency in handling spills in complex geometries and across scales. The use of high-order Eulerian–Lagrangian methods allows for computational efficiency and for handling key processes in ways consistent with their distinct mathematical nature and time scales. The modeling system is tested through a suite of synthetic, laboratory and realistic-domain benchmarks, which demonstrate robust handling of key processes and of 2D/3D couplings. The application of the modeling system to a spill scenario at the entrance of a port in a coastal lagoon illustrates the power of the approach to represent spills that occur in coastal regions with complex boundaries and bathymetry.

The WADI project (Water-tightness Airborne Detection Implementation), integrated within the H2020 initiative, is developing an airborne water leak detection surveillance service, based on manned and unmanned aerial vehicles. This service aims to provide water utilities with adequate information on leaks in large water distribution infrastructures outside urban areas. Given the high cost associated with water infrastructure networks repairs, a reliability layer is necessary to improve the trustworthiness of the WADI leak identification procedure, based on complementary technologies for leak detection. Herein, a methodology based on the combined use of Sentinel remote sensing data and a water leak pathways model is presented, based on data-intensive computing. The resulting water leak detection reliability service, provided to the users through a web interface, targets prompt and cost-effective infrastructure repairs with the required degree of confidence on the detected leaks. The web platform allows for both data analysis and visualization of Sentinel images and relevant leak indicators at the sites selected by the user. The user can also provide aerial imagery inputs, to be processed together with Sentinel remote sensing data at the satellite acquisition dates identified by the user. The platform provides information about the detected leaks location and time evolution, and will be linked in the future with the outputs from water pathway models.

The dynamics of the Aveiro lagoon is assessed through a combination of field data and numerical modeling. An unstructured grid hydrodynamic model is set-up for this system for the first time and its results compare well with data and with a ellestablished model. The model and the data are then used to analyze the propagation of the tide in the lagoon and the variability of tidal asymmetry in the upper and lower lagoon. The lagoon shifts from mild ebb-dominance at the inlet to strong flooddominance in the upper lagoon. This variability may be responsible for the importing capacity suggested by the sediment particle model, estimated at 10% of the littoral drift. On the contrary, a reliminary application of the morphodynamics modeling system MORSYS2D suggests a net export capacity. These opposite results maybe due to the tidal excursion of sediments in the system, which is much larger than the scale of variability of the hydrodynamics. Vol 4. 3282-3294 2006 3-8 de Sept

3 1 485-488pp CTI/NTIEC 2010 24-27 de Maio

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Cet article présente l’approche générale suivie au LNEC pour étudier des problèmes d’estuaires et de zones côtières, du point de vue de leur hydrodynamique, de leur morphodynamique et de la qualité des eaux. Le cadre conceptuel est présenté et permet de définir la problématique et les objectifs à long terme de ce type d’études. Les différents systèmes de modélisation, déjà disponibles ou en cours de développement et d’adaptation, sont ensuite présentés en mettant l’accent sur les aspects computationnels. L’importance de la prise en compte adéquate des processus physiques dans les études de qualité des eaux est enfin illustrée par l’analyse des temps de résidence et de la contamination fécale dans une lagune très dynamique (lagune d’Óbidos, Portugal. 4: 40-46

Morphodynamic modeling systems increasingly appear as valuable tools to understand the dynamics of coastal systems, including mixed-energy tidal inlets, driven by the combined action of tides and waves. This study aims at: 1) applying and validating a morphodynamic modeling system to a rapidly evolving tidal inlet and 2) verifying both qualitatively and quantitavely the ability of the morphodynamic modeling system to simulate the development of the inlet's main features. The MORSYS2D morphodynamic modeling system is applied to the Ancão Inlet (South Portugal), just after its relocation in August 1997. The relocation and the first stages of the inlet development were monitored in the scope of the EU project INDIA, which provided a large database of tidal, wave and bathymetric data. The first step of the present study consists on a fine calibration of the morphodynamic modeling system using the INDIA data. The model/data comparison shows that the modeling system was able to reproduce well wave heights, elevations and current velocities, with root mean square errors of 0.25 m, 0.065 m and 0.12 m/s, respectively. The morphological evolution of Ancão Inlet is then simulated over the period August 1997-January 1999, starting at the inlet relocation. Model predictions were compared to the bathymetric surveys available over the simulated period. Model/data comparison demonstrates that the model is able to reproduce the development of the main features of the Ancão Inlet. From a quantitative viewpoint, the model was also able to reproduce the development of the inlet's cross-section, characterized by faster growths during fair weather conditions. Finally, this study also provides additional insight regarding on the dynamics of mixed-energy (tide, waves) tidal inlets. SI 56

Residence times are a conceptually important indicator of the ecological behavior and self-cleaning capacity of estuaries. However, the quantification of residence times is ambiguous and can be often misleading. Most traditional approaches are integral, providing a "single" characteristic number for the whole system, thus ignoring the strong spatial and temporal variability of residence times in estuaries. In this paper, we propose a new methodology that overcomes these limitations through the diagnostic use of numerical particle tracking for the analysis of residence times in estuaries. Unlike the traditional methods, this approach can also be applied to a wide range of situations that include residence times of pollutants that do not enter the system by the main riverine source (e.g. run-off), or systems without riverine input (lagoons). In spite of their attractive properties, numerical methods have been scarcely used for evaluation of residence times in estuaries. Two different approaches have been applied using particle models and concentration (transport) models. However, past studies using numerical models were focused on localized problems, and detailed, system-wide studies of the spatial and time variability of residence times have not been done yet. The methodology proposed herein is based on very accurate numerical tracking of large number of particles, carefully distributed in the domain and released at several instants in time, which address both the variability within the tidal cycle and with neap/spring tides. The results are then integrated through histogram analysis into detailed, yet condensed descriptions of the space- and time variability of residence times. The first part of this paper describes our particle tracking algorithms, and studies their numerical accuracy as a functions of controlling parameters: machine accuracy and flow characteristics. Numerically very accurate tracking is then used in the second part to diagnostically assess the spatial and temporal characterization of residence times, using two-dimensional, depth-averaged flow simulations in the Tagus estuary (Portugal). Finally, we integrate the results from the spatial and temporal analysis into a single histogram, and compare it with a traditional integral approach to freshwater residence time. At a conceptual level, our results support the use of particle-tracking methods as a basis for the evaluation of residence times in estuaries, and suggest that histograms are a good tool for residence time characterization. However, caution should be used in the application of the concept for practical purposes, since the accuracy of the method is significantly dependent on the quality of the driving flow field. Key Words: Residence Time, Particle methods, Numerical methods, Estuaries Aldama et al. (eds.) Vol. 2, 355-362 ****** ****** ******

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