Comparison of sediment transport formulae with simulation of several storms on a Mediterranean beach and with in-situ sedimentary flux on a North Sea beach

Water Qualit

Contrasting geomorphological storm response from two adjacent shorefaces.

Shorefaces play a critical role in cross-shore sediment transport between the beach and inner shelf, particularly during storm conditions. A comparison and examination of storm-driven sedimentary changes on two adjacent shorefaces in Northern Ireland, located only 5 km apart, revealed significantly different geomorphological responses. The steeper shoreface at West Strand responded with extensive sediment deposition across almost the entire shoreface, in contrast with the more dissipative and quasi- linear shoreface at Portstewart, which mostly showed nearshore bar changes. Results from the two sites, which have similar wave/wind characteristics and seabed sediments, suggest that: (i) cross-shore morphology, (ii) immediately previous (antecedent) shoreface morphodynamic behaviour and (iii) the presence, or lack of, offshore sand appear to be the primary controls on storm- driven sedimentary changes attributed to the high-energy event

Nearshore Monitoring with X-Band Radar: Maximising Utility in Dynamic and Complex Environments

Coastal management and engineering applications require data that quantify the nature and magnitude of changes in nearshore bathymetry. However, bathymetric surveys are usually infrequent due to high costs and complex logistics. This study demonstrates that ground‐based X‐band radar offers a cost‐effective means to monitor nearshore changes at relatively high frequency and over large areas. A new data quality and processing framework was developed to reduce uncertainties in the estimates of radar‐derived bathymetry and tested using data from an 18‐month installation at Thorpeness (UK). In addition to data calibration and validation, two new elements are integrated to reduce the influence of data scatter and outliers: (a) an automated selection of periods of ‘good data’ and (b) the application of a depth‐memory stabilisation. For conditions when the wave height is >1 m, the accuracy of the radar‐derived depths is shown to be ±0.5 m (95% confidence interval) at 40x40 m spatial resolution. At Thorpeness, radar‐derived bathymetry changes exceeding this error were observed at timescales ranging from three weeks to six months. These data enabled quantification of changes in nearshore sediment volume at frequencies and spatial cover that would be difficult and/or expensive to obtain by other methods. It is shown that the volume of nearshore sediment movement occurring at timescale as short as few weeks are comparable with the annual longshore transport rates reported in this area. The use of radar can provide an early warning of changes in offshore bathymetry likely to impact vulnerable coastal locations

Beaches at risk

No description supplie

La psyché à l'épreuve du scalpel (abords sémiologiques et réflexion éthique)

Ce travail consiste en l étude clinique d un seul patient, qu il nous a été donné de suivre pendant plus de 2 ans. Cet homme, Mr L., a subi en 2003 une amygdalo-hippocampectomie gauche pour le traitement d une épilepsie temporale résistante. Nous l avons rencontré plus de 6 ans après son intervention chirurgicale. Depuis celle-ci, des modifications subjectives sont évidentes. Le tableau clinique, stable depuis deux ans, est caractérisé par un vide émotionnel et affectif. La première partie de notre travail est consacrée à la description du cas. Les trois parties suivantes sont l occasion d une discussion diagnostique. Après avoir passé en revue les complications de la chirurgie de l épilepsie, nous avons discuté le diagnostic de schizophrénie pour Mr L. Nous étudions ensuite l anatomo-physio-pathologie des structures cérébrales réséquées chez notre patient. Nous concluons à une imputabilité certaine du geste neurochirurgical, sans pouvoir porter de diagnostic satisfaisant pour rendre compte du tableau clinique actuel. Au terme de cette discussion, nous proposons l hypothèse que l amygdalo-hippocampectomie constitue un modèle expérimental d apatheia, terme utilisé par les Stoïciens pour désigner l état d impassibilité émotionnelle visée par ces philosophes. Nous introduisons alors le concept de stoïcité émotionnelle . Nous élargissons ensuite notre réflexion, dans les deux dernières parties de ce travail. Après avoir rappelé les éléments de déontologie et de législation concernant l information médicale, nous proposons le cadre de l information à délivrer au patient candidat à une amygdalo-hippocampectomie. Cette information devrait inclure le risque de stoïcité émotionnelle et ses conséquences psychosociales. En guise de conclusion, nous suggérons la réalisation de travaux complémentaires afin de confirmer statistiquement la validité de ce syndrome. Enfin, nous ouvrons la réflexion sur le type d accompagnement à proposer aux patients qui présentent une stoïcité émotionnelle .This work consists in the clinical study of one patient, who we followed for more than 2 years. This man, Mr L., underwent in 2003 a left amygdalo-hippocampectomy to treat a resistant epilepsy. We met him more than 6 years after his operation. Since the neurosurgery, subjective changes are obvious. The clinical record, stable since two years, is caracterized by an emotional and affective void . The first part of our work is devoted to the description of the case. A diagnostic is given based on the three following parts. After reviewing the complications of the epilepsy surgery, we discuss the diagnosis of schizophrenia for Mr L. Then, we made the anatomo-physio-pathological study of the cerebral structures resected in our patient. We conclude on a certain accountability of the neurosurgical gestures, but no acceptable diagnosis able to take into account the clinical symptomatology. At the end of this diagnosis discussion, we make the assumption that the amygdalo-hippocampectomy represents an experimental model of apatheia, a word used by the Stoicists to indicate the emotional impassiveness sought by these philosophers. Then, we introduce the concept of emotional stoicity . In the last two parts of this work we expand our analysis. After having restated the elements of deontology and legislation related to the medical information, we propose the framework of the information to deliver to the patient candidate to amygdalo-hippocampectomy. The information should include the risk of emotional stoicity and its psychosocial consequences. To conclude, we suggest complementary work to be carried out in order to confirm this syndrome s statistic validity. Finally, we open the discussion about the kind of support to give to patients who present an emotional stoicity .AMIENS-BU Santé (800212102) / SudocSudocFranceF

Minutes de bathymétrie et évolution des fonds marins: les abords du port de Calais

The study of the long-term evolution of the seabed requires detailed knowledge of bathymetry. Hydrographic Service field sheets are more precise than navigation charts and reflect the evolution of the seabed's morphology more accurately

Shoreface sand supply and mid- to late Holocene aeolian dune formation on the storm-dominated macrotidal coast of the southern North Sea

Although pulses of coastal dune development in the course of the Holocene have been attributed to variations in the availability of sand, to modulation of sand supply by sea level change, and to changes in wind conditions, identifying the processes driving such pulses has been rather elusive. The shore deposits bordering the tide- and storm wave-dominated southern North Sea evince complex mid- to late Holocene stratigraphy and sediment heterogeneity. These deposits include a unique 7 km-long, 0.3-0.6 km-wide, and up to 7 m-high aeolian sand unit, the Ghyvelde dune, occurring astride the French-Belgian border in an apparently 'anomalous inland location. The dune overlies, and is surrounded by, tidal sandy and muddy deposits incorporating freshwater peat. Data from four mechanical cores and eight auger holes, and three radiocarbon ages and one OSL age suggest that this inland dune was part of an ancestral North Sea sand flat and mudflat environment. Confronting the dune stratigraphy with the prevailing tide- and storm-controlled dynamics of shoreline progradation in this area indicates that dune formation occurred under a pulse of abundant sand supply resulting from the attachment, to a mid-Holocene North Sea tidal-flat shore, of a shoreface tidal bank under repeated storms. This mode of onshore sand supply generates extremely rapid progradation (up to 1 km over a century) of the sand flat shore, the surface of which serves as a large aeolian fetch zone for active backshore dune accumulation, while parts of this surface trap, locally, significant amounts of mud that are subsequently fossilised by aeolian sand. The potential influence of sea level and storminess in modulating the timing of shoreface sand supply and late Holocene coastal dune development in the southern North Sea, reported in studies from other areas, remains to be established

Gouvernance des risques littoraux en Nord-Pas-de-Calais

Programme de recherche Fondation de France: Appel à Projets Fondation de France « Quels littoraux pour demain ? Savoirs, pratiques, vision et représentations de l’avenir ».International audienceDans un contexte de changement climatique, les risques littoraux constituent un enjeu majeur . Face aux atermoiements des politiques publiques, des solutions opérationnelles peuvent être mises en œuvre dans le cadre de la gestion intégrée des zones côtières. La recherche engagée s'est développée sur un espace particulièrement sensible au changement climatique, le Nord Pas de Calais. Le premier défi à relever est celui des connaissances, tant au regard des évolutions naturelles (mouvements des sables côtiers, dunaires) que de l'anthropisation ou des données historiques et de leurs utilisations. De même qu'est posée la question des savoirs au service de la décision publique, de la gouvernance en matière de prévention des risques. Ces données conduisant inéluctablement à renouveler les modalités de la prévention tant en termes de planifications spécifiques des risques, de développement urbain, en particulier des zones littorales que de maîtrise foncière mais aussi au regard des conditions d'édification des bâtiments. Ces évolutions doivent aussi être appréciées dans le cadre des effets du changement climatique sur la biodiversité des zones côtières. Les politiques de prévention conduisent les acteurs littoraux à engager des travaux pour prévenir les submersions. La création d’ouvrages de protection constitue un défi particulier dont le financement peut être diversifié. Enfin l’ensemble de ces évolutions repose sur une expertise dont l’indépendance permettrait de garantir une certaine pertinence

Dynamique non-linéaire des niveaux d’eau modélisés et mesurés dans les ports de Boulogne-sur-Mer, Calais et Dunkerque

International audienc

Nonlinear dynamics of the sea level time series in the eastern English Channel

International audienceAbstract Coastal flooding due to surge events represents natural hazards with huge potential consequences for coastal regions. Sea level time series display variations on a large range of timescales, with a deterministic component associated with tidal variations and a stochastic component primarily associated with meteorological forcing, the non-tidal residual. The deterministic component can be evaluated using a model taking into account astronomical forcing and topographic information. The measured sea level is the sum of a slowly varying mean sea level component, the tidal term and the stochastic term. Here, we consider hourly time series recorded in the ports of Boulogne-sur-Mer, Calais, and Dunkirk, in the eastern English Channel. Measured data and modeled data, both provided by the SHOM (“Service hydrographique et océanographique de la marine,” hydrographic and oceanographic services of the French Navy), are analyzed using Fourier spectral analysis. The statistics of return times of extreme events are also estimated directly from the time series and compared between modeled and measured data. It is found that return times from tidal or measured time series are quite different for large thresholds and that they also have a very different Fourier power spectrum, the measured data having a power-law regime which is not found in the modeled tidal data. It is also shown, using Hilbert–Huang transform, that non-tidal residual time series are intermittent and possess multifractal scaling properties. Finally, water level non-tidal residual relationship is explored, and it is shown that the larger mean values of the surge (negative and positive parts) are obtained for the medium level of the tidal value