Papers by Francisco Sancho

Development and validation of a three-dimensional morphodynamic modelling system for non-cohesive sediments
Ocean Modelling, Nov 1, 2012
ABSTRACT a b s t r a c t The morphology of estuaries and rivers changes constantly due to the dyn... more ABSTRACT a b s t r a c t The morphology of estuaries and rivers changes constantly due to the dynamic imbalance between the forcing actions (e.g. river flow, tides, surface waves and wind) and the sedimentary reactions. Under-standing and predicting these changes are very important for an scientific-based, sustained management of these systems. Morphodynamic process-based numerical models can be used for this purpose. The development and validation of a new three-dimensional unstructured grid morphodynamic modelling system, MORSELFE, aiming at simulating short-term morphological evolutions of estuaries and sandy riv-ers (temporal scale of days to month), are presented. MORSELFE couples a three-dimensional hydrody-namic model, with an advection–diffusion transport model for the suspended sediments, an empirical formula for the bed load, and a bed updating module. The model considers the simulation of non-cohe-sive sediment and does not account for wave effects. A new approach is proposed to compute the erosive fluxes, which adapts them to the vertical grid resolution. The use of unstructured grids and the imple-mentation in parallel mode make MORSELFE particularly adapted to engineering applications. The model was assessed and validated against analytical and experimental test cases, also allowing the inference on the optimum choice of the model parameters and variables.

Journal of Marine Science and Engineering
Costa da Caparica beach, in Portugal, has suffered from chronic erosion for the last 50 years, a ... more Costa da Caparica beach, in Portugal, has suffered from chronic erosion for the last 50 years, a phenomenon that has been countered by various management interventions. This study aims at comparing sixteen possible interventions, thus identifying the most effective one(s) in terms of reducing beach erosion or even promoting beach accretion. This exercise is achieved using a one-line shoreline evolution model, calibrated with in situ field data, forced by local wave conditions. The target management period is 25 years. In the calibration phase, it is found that the annual mean alongshore net sediment transport along the 24 km sandy coast is variable in direction and magnitude, but it is mostly smaller than ±50 × 103 m3/year. This net transport results from the imbalance of northward/southward-directed bulk transports of circa tenfold-larger magnitudes. This affects the overall sediment balance at the urban beaches, as well as the effectiveness of the intervention strategies. The resu...
Wave propagation at the entrance of the Tagus estuary
Depth estimation by refraction of swell waves using SAR data Linear dispersion relationship for o... more Depth estimation by refraction of swell waves using SAR data Linear dispersion relationship for ocean surface waves: Two methodologies to retrieve ℎ from 𝑘 and 𝜔: "Ray-Tracing Method" [1] -Instituto Hidrográfico • 𝜔 constant for each wave track • 𝜔 computed offshore using a reference bathymetric model "Fixed Grid Method" [2] -Laboratório Nacional de Engenharia Civil • 𝜔 constant for the entire grid (regular or unstructured) • 𝜔 computed offshore from wave data (buoys or models) Both methods need optimal swell conditions (𝜔 constant)

A wave tracking method to estimate high resolution coastal bathymetry from SAR images will be pre... more A wave tracking method to estimate high resolution coastal bathymetry from SAR images will be presented. The method relies on the mathematical connection between wavelength, retrieved from SAR images using Fast Fourier transformations, and local depth through the linear dispersion relation. Optimal conditions of swell waves and good quality of image acquisition are necessary in order to correctly retrieve the wave parameters from SAR. The wave tracking algorithm also requires a reference bathymetry for a first-guess of the water depth for the farthest offshore point, which marks the limit of deep/intermediate waters. Wave rays are then tracked from this limit to the wave breaking zone (typically at depths of the order of 1 to 10 m). The output of the algorithm consists of the estimated depths interpolated to a uniform rectangular mesh with a horizontal resolution of 150m. This work is a part of a research application developed within the EU H2020 Coastal Waters Research Synergy Fram...
A metodologia AHP para a ponderação de fatores de cálculo das vulnerabilidades O. Antunes, J.L. Craveiro, P. Freire, F. Oliveira & F. Sancho Seminário Final do Projeto FCT Regulações e conflitos ambientais devido à erosão costeira | LNEC, Lisboa | 2013-07-25

The present work focuses on the development of an application within Co-ReSyF (Coastal<br> ... more The present work focuses on the development of an application within Co-ReSyF (Coastal<br> waters Research Synergy Framework) platform, that aims at deriving coastal bathymetries from<br> Synthetic Aperture Radar (SAR) satellite images, with clear swell wave signatures. The method is based<br> on estimating, first, the predominant wavelength at user-defined grid points from the computation of<br> the wavenumber spectra via 2D Fast Fourier Transform (FFT) of overlapping sub-images at each point.<br> The underneath depth is then estimated using the wavenumber dispersion relationship, from<br> intermediate to shallow waters. Results of the estimated depths within a region of the continental shelf<br> off Aveiro is presented, showing reasonable agreement with the reference surveyed bathymetry, in the<br> regions of depth between 10 and 60 metres. The agreement then deteriorates as depth increases until the<br> wave propagation "...
Urban Communities in the Coastal Zone: An AHP (Analytic Hierarchy Process) Multicriteria Methodolog for the construction of a Social Vulnerability Index due the Maritime Action

Rehabilitation and protection of Colwyn Bay beach: A case study
Journal of Coastal Research
Oliveira, F.S.B.F., Freire, P., Sancho, F., Vicente, C.M. and Climaco, C., 2011. Rehabilitation a... more Oliveira, F.S.B.F., Freire, P., Sancho, F., Vicente, C.M. and Climaco, C., 2011. Rehabilitation and protection of Colwyn Bay beach: a case study. Journal of Coastal Research, SI 64 (Proceedings of the 11th International Coastal Symposium), 1272 – 1276. Szczecin, Poland, ISNN 0749-0208 Colwyn Bay beach is undergoing a process of erosion. The present study aims at characterizing the beach dynamics and developing alternative solutions for beach rehabilitation and protection. The method applied to characterize the foreshore morphological evolution was the assessment of the shoreline evolution, the analysis of the foreshore 3D evolution and the analysis of cross-shore profile evolution. The sedimentologic contents of the beach were characterized based on the analysis of superficial samples. The hydrodynamic characterization was based on the analysis of the wave climate at three inshore points in front of the beach and of the tidal and surge levels. These data provided the necessary information for the characterization of the longshore transport and evaluation of the beach active zone. The first part of developing alternative solutions was the definition of the optimum long-term recharged beach profile, which, due to the high tidal range, was calculated based on the 2S-EBP method. The beach berm was designed to avoid direct wave action on the seawall existent at the beach backshore. For that, a morphodynamic model was applied to test the beach retreat under storm events. Finally, alternative long-term solutions based on a nourishment strategy were tested with two shoreline evolution models. Two initial alternative solutions of beach recharge with different grain size sand followed by six alternative solutions of beach recharge with sand retention structures arrangements were tested. The results, here qualitatively and quantitatively compared, point out to a best solution based on shore-normal structures to retain the beach recharge.
A sea wave study at the entrance of the Tagus estuary
Extraction and classification of beach features based on object-oriented analysis from video-images
Determinação de ondas representativas em zonas costeiras aplicação à barra da ria de Aveiro
The Proceedings of the Coastal Sediments 2011, 2011
Large-scale physical model tests are ongoing at CIEM wave flume of the Polytechnic University of ... more Large-scale physical model tests are ongoing at CIEM wave flume of the Polytechnic University of Catalonia. This paper presents some aspects of the study aimed to analyze the effect of wave storm events on dune erosion and overwash processes. Two different regimes of storm attack on the sandy beach/dune system are investigated: a collision regime with swash and run-up to the dune face and an overwash regime with wave run-up overtopping the dune crest (Sallenger et al. 2003). Eight run tests are performed with a combination of four irregular wave conditions and two different water depths. Detailed measurements in time and space of profile evolution, hydrodynamics, sediment concentration, overtopping rate and photogrammetric survey are carried out.
Observation of rip currents by synthetic aperture radar
Proceedings of SEASAR, 2006
Rip currents are near-shore cellular circulations that can be described as narrow, jet-like and s... more Rip currents are near-shore cellular circulations that can be described as narrow, jet-like and seaward directed flows. These flows originate close to the shoreline and may be a result of alongshore variations in the surface wave field. The onshore mass ...
Continental Portuguese coast: case studies on erosion risk, conflicts and Environmental Regulations. Contributions to Environment Sociology and Human Ecology
Modelação física da evolução do perfil de praia a diferentes escalas

Este trabalho tem como principal objetivo verificar se diferentes linhas de costa iniciais,<br... more Este trabalho tem como principal objetivo verificar se diferentes linhas de costa iniciais,<br> extraídas de imagens de satélite e de sensores, influenciam os resultados da modelação da sua evolução<br> a longo prazo. Primeiramente, comparam-se as posições da linha de costa, em instantes próximos.<br> Seguidamente, determina-se em que medida a ordem de grandeza da variação inicial observada<br> influencia a evolução da linha de costa, usando o modelo numérico LITMOD. Verifica-se que as<br> imagens de satélite mais indicadas para a extração da linha de costa são as obtidas pelos sensores NIR<br> e RGB (satélite Sentinel2), concluindo-se que a morfologia da praia poderá influenciar a precisão da<br> extração da linha de costa. Ao usar o modelo LITMOD constata-se que a importância dos desvios<br> iniciais na posição da linha de costa se atenua com o tempo de simulação, embora haja um impacte<br> significativo no cálculo de sedimento...
Apresenta-se uma panorâmica geral sobre a protecção da orla costeira. Referem-se os processos fís... more Apresenta-se uma panorâmica geral sobre a protecção da orla costeira. Referem-se os processos físicos responsáveis pela dinâmica sedimentar, e os principais problemas a ela associados que afectam praias e embocaduras de estuários e lagunas. As soluções mais comuns para este tipo de problemas são depois revistas de forma crítica. Finalmente, três casos de estudo são utilizados para exemplificar problemas e soluções, e, simultaneamente, ilustrar abordagens seguidas em estudos de engenharia: uma praia encaixada em erosão (praia de Hac-Sá, República Popular da China), um sistema composto por três praias, um canal e uma laguna com problemas simultâneos de erosão e assoreamento (praias de Leblon, Ipanema e Arpoador, Brasil) e uma embocadura lagunar com problemas de assoreamento e de estabilidade (Lagoa de Óbidos, Portugal).
Avaliação do risco de galgamento, erosão e inundações costeiras F. Sancho, F. Oliveira, P. Freire & J.L. Craveiro Forum Conselho Científico dos Laboratórios de Estado | LNEC, Lisboa 2013-03-21
Apresenta-se uma panorâmica geral sobre a protecção da orla costeira. Referem-se os processos fís... more Apresenta-se uma panorâmica geral sobre a protecção da orla costeira. Referem-se os processos físicos responsáveis pela dinâmica sedimentar, e os principais problemas a ela associados que afectam praias e embocaduras de estuários e lagunas. As soluções mais comuns para este tipo de problemas são depois revistas de forma crítica. Finalmente, três casos de estudo são utilizados para exemplificar problemas e soluções, e, simultaneamente, ilustrar abordagens seguidas em estudos de engenharia: uma praia encaixada em erosão (praia de Hac-Sá, República Popular da China), um sistema composto por três praias, um canal e uma laguna com problemas simultâneos de erosão e assoreamento (praias de Leblon, Ipanema e Arpoador, Brasil) e uma embocadura lagunar com problemas de assoreamento e de estabilidade (Lagoa de Óbidos, Portugal).
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Papers by Francisco Sancho