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51. Beach recovery from extreme storm activity during the 2013-14 winter along the Atlantic coast of Europe

Author

Dodet, Guillaume, Castelle, Bruno, Masselink, Gerd, Scott, Tim, Davidson, Mark, Floc'H, France, Jackson, Derek, Suanez, Serge, Littoral, Environnement, Télédétection, Géomatique (LETG - Brest), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-Université de Nantes (UN)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), UMR 5805 Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), School of Biological and Marine Sciences, Plymouth University, Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre for Coastal and Marine Research [Coleraine], University of Ulster, Direction Générale de l'Armement (DGA) through PROTEVS (12CR6) project, Observatoire Aquitain des Sciences de l’Univers (OASU), NERC BLUE-coast project (NE/N015525/1), Service National d’Observation (SNO) DYNALIT labelled by CNRS-INSU, ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), ANR-17-CE01-0014,SONO,Marier les objectifs de défense côtière avec ceux de la protection du milieu naturel grâce aux dunes sableuses(2017), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Caen Normandie (UNICAEN), Université de Nantes (UN)-Université de Nantes (UN), Université de Brest (UBO)-Université de Bretagne Sud (UBS)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), and Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)

Subjects
extreme events, [SDE]Environmental Sciences, beach recovery, winter 2013/2014, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Atlantic coast of Europe
Abstract

The storm sequence of the 2013-14 winter left many beaches along the Atlantic coast of Europe in their most eroded state for decades. Understanding how beaches recover from such extreme events is essential for coastal managers, especially in light of potential regional increases in storminess due to climate change. Here we analyse a unique dataset of decadal beach morphological changes along the west coast of Europe to investigate the post-2013-14 winter recovery. We show that the recovery signature is site specific and multi-annual, with one studied beach fully recovered after 2 years, and the others only partially recovered after 4 years. During the recovery phase, winter waves primarily control the timescales of beach recovery, as energetic winter conditions stall the recovery process whereas moderate winter conditions accelerate it. This inter-annual variability is well correlated with climate indices. On exposed beaches, an equilibrium model showed significant skill in reproducing the post-storm recovery and thus can be used to investigate the recovery process in more detail. (c) 2018 John Wiley & Sons, Ltd.

Published
2019

52. THE WEST EUROPE PRESSURE ANOMALY (WEPA): A SIMPLE SEA-LEVEL-PRESSURE BASED CLIMATE INDEX CONTROLLING WINTER WAVE HEIGHTS ALONG THE WESTERN COAST OF EUROPE FROM PORTUGAL TO UK (36-52°N)

Author

Castelle, Bruno, Dodet, Guillaume, Masselink, Gerd, Scott, Tim, Université de Bordeaux (UB), Centre National de la Recherche Scientifique (CNRS), Littoral, Environnement, Télédétection, Géomatique (LETG - Brest), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Caen Normandie (UNICAEN), Université de Nantes (UN)-Université de Nantes (UN), School of Marine Science and Engineering, Université Paris Diderot - Paris 7 (UPD7), DGA PROTEVS (12CR6), NERC BLUE-coast projetc (NE/N015525/1), ANR-14-ASTR-0004,CHIPO,Processus cross-shore et longshore combinés en morphodynamique littorale(2014), ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), Dodet, Guillaume, Accompagnement spécifique des travaux de recherches et d’innovation défense - Processus cross-shore et longshore combinés en morphodynamique littorale - - CHIPO2014 - ANR-14-ASTR-0004 - ASTRID - VALID, and Laboratoires d'excellence - LabexMER Marine Excellence Research: a changing ocean - - LabexMER2010 - ANR-10-LABX-0019 - LABX - OLD

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2017

53. THE ROLE OF MULTI-DECADAL CLIMATE VARIABILITY IN CONTROLLING COASTAL DYNAMICS: RE-INTERPRETATION OF THE ‘LOST VILLAGE OF HALLSANDS’

Author

Wiggins, Mark, Scott, Tim, Masselink, Gerd, Russell, Paul, Castelle, Bruno, Dodet, Guillaume, Dodet, Guillaume, School of Marine Science and Engineering, Université Paris Diderot - Paris 7 (UPD7), Université de Bordeaux (UB), Centre National de la Recherche Scientifique (CNRS), Littoral, Environnement, Télédétection, Géomatique (LETG - Brest), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Caen Normandie (UNICAEN), Université de Nantes (UN)-Université de Nantes (UN), NE/M004996/1, and BLUE-coast project

Subjects
[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, ComputingMilieux_MISCELLANEOUS, [SDU.ENVI] Sciences of the Universe [physics]/Continental interfaces, environment
Abstract

International audience

Published
2017

54. Dynamique pluri-décennale du trait de côte en lien avec les variations des forçages météo-océaniques au nord de la Bretagne (baie de Goulven, France)

Author

Stéphan, Pierre, Dodet, Guillaume, Suanez, Serge, Tardieu, Isabel, David, Laurence, Littoral, Environnement, Télédétection, Géomatique (LETG - Brest), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Caen Normandie (UNICAEN), Université de Nantes (UN)-Université de Nantes (UN), Institut National des Sciences de l'Univers (INSU) - Observatoire marin de l'IUEM, and Direction Générale de l'Armement (DGA) - programme de recherche PROTEVS (12CR6) coordonné par le SHOM-Brest

Subjects
trait de côte, météo-océanique, Bretagne, erosion, Goulven, shoreline, meteo-oceanic, WEPA, runup, Brittany, [SDE]Environmental Sciences, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, surge, ONA, surcote
Abstract

International audience; The link between the shoreline changes and the variation of the meteo-oceanic forcing of the Goulven Bay (north Brittany, France) is analyzed over a period of 70 years (1948-2016). This analysis is based on a study of shoreline changes by photo-interpretation digital processing and a DGPS field measurement conducted in 2016. In parallel, the chronology of extreme water level combining surge and wave conditions at high tide water level, was reconstructed to define the potential erosive phases over the period 1948-2015. The statistical relationship between shoreline changes and these hydrodynamic conditions is evaluated from a confusion matrix that allows to define the probability of relation between the two parameters. 5 potential erosive periods, characterized by a high frequency of extreme water level, are thus identified: 1961-1968, 1978-1980, 1982-1990, 1993-2005, 2013-2016. Morphological analysis shows that the response of the shoreline to these hydrodynamic forcing varies according to the sectors of the studied coastal zone. If the evolution of the Keremma beach shows a high statistical relation with the frequency of extreme water levels, the spits of Pen ar C'hleuz and Kernic, as well as the beaches of Lanévez and Saint-Gouévroc, evolve under the influence of anthropogenic forcing and/or under the influence of local processes related to the morphological context of the shoreface. Finally, this study shows that the WEPA climate index (West Europe Pressure Anomaly) seems more adequate than the NAO index (North Oscillation Atlantic) to characterize the pluriannual variability of meteo-oceanic and hydrodynamic conditions in northern Brittany.; Le lien entre la cinématique du trait de côte et les variations des forçages météo-océaniques de la baie de Goulven (nord Bretagne, France) est analysé sur une période de 70 ans (1948 et 2016). Ce travail repose sur une étude des changements du trait de côte par photo-interprétation auquel s’ajoute un levé de terrain réalisé au DGPS en 2016. En parallèle, la chronologie des niveaux d’eau extrêmes combinant les surcotes et les conditions de houle lors des pleines mers, a été reconstituée afin de définir les phases potentiellement érosives sur la période 1948-2015. La relation statistique entre la cinématique du trait de côte et les conditions hydrodynamiques est évaluée à partir d’une matrice de confusion qui permet de définir des liens probables entre les deux paramètres. Cinq périodes potentiellement érosives, caractérisées par une forte fréquence de niveaux d’eau extrêmes, sont ainsi identifiées : 1961-1968, 1978-1980, 1982-1990, 1993-2005, 2013-2016. L’analyse morphologique montre quant à elle que la réponse du trait de côte à ces forçages hydrodynamiques varie selon les portions du littoral étudié. Si l’évolution de la plage de Keremma présente une bonne relation statistique avec la fréquence des niveaux d’eau extrêmes, les flèches de Pen Ar C’hleuz et du Kernic, comme les plages de Lanévez et de Saint-Gouévroc, semblent quant à elles répondre à l’action de forçages anthropiques et/ou à l’influence de processus locaux liés au contexte morphologique de l’avant plage. Cette étude montre enfin que l’indice climatique WEPA (West Europe Pressure Anomaly) paraît plus approprié que l’indice ONA (Oscillation Nord Atlantique) pour caractériser la variabilité pluriannuelle des conditions météo-océaniques et hydrodynamiques au nord de la Bretagne.

Published
2018

58. Wave Runup Over Steep Rocky Cliffs

Author

Dodet, Guillaume, Leckler, Fabien, Sous, D., Ardhuin, Fabrice, Filipot, Jean-francois, Suanez, S., Dodet, Guillaume, Leckler, Fabien, Sous, D., Ardhuin, Fabrice, Filipot, Jean-francois, and Suanez, S.

Abstract

Wave runup is known to depend on offshore wave conditions and coastal morphology. While most field studies on wave runup have focused on low‐to‐mild‐sloping sandy beaches, runup measurements on steep and irregular rocky cliff profiles are still very scarce. Here we investigate the physical processes controlling wave runup in such environments and the range of applicability of empirical runup formula. This study focuses on the steep rocky cliffs (0.1 < tanβ < 0.4) of Banneg Island, a small island located in the Molène archipelago, Brittany, France, occasionally flooded during extreme water level events. A statistical parameter for extreme runup is derived from the measurements of pressure sensors deployed in the intertidal zone. Deep water wave parameters are used to force a high‐resolution wave model, and nearshore wave parameters and high‐resolution topographic data are analyzed concurrently with runup time series in order to assess the dependence of the runup on hydrodynamic conditions and morphological parameters. The wave runup is shown to be strongly related to the square root of the offshore significant wave height times the offshore wavelength. The measurements also reveal the depth dependence of the runup, which is mainly attributed to the curvature of the foreshore profile. In comparison to empirical relation obtained for a mild‐sloping beach, the present data show a significant reduction in normalized wave runup, that is attributed to enhanced bottom friction over the rocky bottom. Plain Language Summary When waves reach the shores, they travel up and down the beach before being reflected seaward. The maximum vertical excursion of the waterline relative to the still water level, called the wave runup, is a key parameter for the design of coastal structures and the prediction of overtopping volumes during storm events. Most runup studies in natural environments have focused on smooth and mild‐sloping sandy beaches, and empirical formula to predict the wave

Published
2018
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59. Increased Winter-Mean Wave Height, Variability, and Periodicity in the Northeast Atlantic Over 1949-2017

Author

Castelle, Bruno, Dodet, Guillaume, Masselink, Gerhard, Scott, Tim, Castelle, Bruno, Dodet, Guillaume, Masselink, Gerhard, and Scott, Tim

Abstract

A 69-year (1948-2017) numerical weather and wave hindcast is used to investigate the interannual variability and trend of winter wave height along the west coast of Europe. Results show that the winter-mean wave height, variability, and periodicity all increased significantly in the northeast Atlantic over the last seven decades which primarily correlate with changes in the climate indices North Atlantic Oscillation (NAO) and West Europe Pressure Anomaly (WEPA) affecting atmospheric circulation in the North Atlantic. NAO and WEPA primarily explain the increase in winter-mean wave height and periodicity, respectively, while both WEPA and NAO explain the increase in interannual variability. This increase in trend, variability, and periodicity resulted in more frequent high-energy winters with high NAO and/or WEPA over the last decades. The ability of climate models to predict the winter NAO and WEPA indices a few months ahead will be crucial to anticipate coastal hazards in this region. Plain Language Summary We explore the evolution of winter-mean wave height, variability, and periodicity in the northeast Atlantic over 1949-2017 and the links with the primary climate indices explaining winter wave activity, which is critical from the coastal hazard perspective. The climate indices NAO and WEPA primarily drive the increase in winter-mean wave height and periodicity, respectively, while both WEPA and NAO explain the increase in interannual variability, resulting in more frequent high-energy winters over the last seven decades. Extreme winter-mean wave heights become more frequent as WEPA and NAO positivity and variability increase. Predicting WEPA and NAO a few months ahead is crucial to anticipate coastal hazards, which is of interest for coastal and climate communities.

Published
2018
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60. Infragravity waves: from driving mechanisms to impacts

Author

Proceskunde, Coastal dynamics, Fluvial systems and Global change, Bertin, Xavier, de Bakker, A.T.M., van Dongeren, Ap, Coco, Giovanni, Andre, Gael, Ardhuin, F., Bonneton, P., Bouchette, Frederic, Castelle, B., Crawford, Wayne, Davidson, M., Deen, Martha, Dodet, Guillaume, Guerin, Thomas, Inch, Kris, Leckler, Fabien, McCall, Robert, Muller, Heloise, Olabarrieta, Maintane, Roelvink, Dano, Ruessink, B.G., Sous, Damien, Stutzmann, Eleonore, Tissier, M.F.S., Proceskunde, Coastal dynamics, Fluvial systems and Global change, Bertin, Xavier, de Bakker, A.T.M., van Dongeren, Ap, Coco, Giovanni, Andre, Gael, Ardhuin, F., Bonneton, P., Bouchette, Frederic, Castelle, B., Crawford, Wayne, Davidson, M., Deen, Martha, Dodet, Guillaume, Guerin, Thomas, Inch, Kris, Leckler, Fabien, McCall, Robert, Muller, Heloise, Olabarrieta, Maintane, Roelvink, Dano, Ruessink, B.G., Sous, Damien, Stutzmann, Eleonore, and Tissier, M.F.S.

Published
2018

64. A new climate index controlling winter wave activity along the Atlantic coast of Europe: The West Europe Pressure Anomaly

Author

Castelle, Bruno, Dodet, Guillaume, Masselink, Gerd, Scott, Tim, Castelle, Bruno, Dodet, Guillaume, Masselink, Gerd, and Scott, Tim

Abstract

A pioneering and replicable method based on a 66-year numerical weather and wave hindcast is developed to optimize a climate index based on the sea level pressure (SLP) that best explains winter wave height variability along the coast of western Europe, from Portugal to UK (36-52 degrees N). The resulting so-called Western Europe Pressure Anomaly (WEPA) is based on the sea level pressure gradient between the stations Valentia (Ireland) and Santa Cruz de Tenerife (Canary Islands). The WEPA positive phase reflects an intensified and southward shifted SLP difference between the Icelandic low and the Azores high, driving severe storms that funnel high-energy waves toward western Europe southward of 52 degrees N. WEPA outscores by 25-150% the other leading atmospheric modes in explaining winter-averaged significant wave height, and even by a largest amount the winter-averaged extreme wave heights. WEPA is also the only index capturing the 2013/2014 extreme winter that caused widespread coastal erosion and flooding in western Europe.

Published
2017
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65. Multi-scale resolution modeling in WAVEWATCH III with triangle-based meshes : explicit and implicit schemes in versions 4.18 & 5.xx with application to the Iroise sea

Author

Leckler, Fabien, Roland, Aron, Dutour Sikirić, Mathieu, Ardhuin, Fabrice, Michaud, Heloise, Huchet, Marion, Filipot, Jean-Francois, and Dodet, Guillaume

Subjects
unstructured grid, implicit mode, wave model, Physics::Atmospheric and Oceanic Physics
Abstract

With the introduction of unstructured grids, spectral wave models became appropriate tools for the wave sea state modeling in coastal areas. In particular, recent development in WaveWatch III included the wave setup process, wave breaking and triad interactions for better wave modeling in coastal areas. Nevertheless, the increasing need of very high resolution grids brings also the problem of the limited computational resources for many operational applications or are not solvable at all with explicit methodd due to the small time step due to the CFL criteria. Therefore we have introduced in WaveWatch III an implicit solver that works in parallel.

Published
2016

66. Extreme wave activity during 2013/2014 winter and morphological impacts along the Atlantic coast of Europe

Author

Masselink, Gerd, Castelle, Bruno, Scott, Tim, Dodet, Guillaume, Suanez, Serge, Jackson, Derek, Floc'H, France, Plymouth University, Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Littoral, Environnement, Télédétection, Géomatique (LETG - Brest), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Caen Normandie (UNICAEN), Université de Nantes (UN)-Université de Nantes (UN), Centre for Coastal and Marine Research [Coleraine], University of Ulster, Domaines Océaniques (LDO), Centre National de la Recherche Scientifique (CNRS)-Institut d'écologie et environnement-Observatoire des Sciences de l'Univers-Université de Brest (UBO)-Institut national des sciences de l'Univers (INSU - CNRS), UK Natural Environment Research Council (NERC, NE/M004996/1), Direction Générale de l'Armement (DGA) dans le cadre du projet de recherche PROTEVS (12CR6) coordonné par le SHOM, ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), and ANR-14-ASTR-0004,CHIPO,Processus cross-shore et longshore combinés en morphodynamique littorale(2014)

Subjects
Europe, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Atlantic, storms, waves, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, beaches, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment
Abstract

International audience; Studies of coastal vulnerability due to climate change tend to focus on the consequences of sea level rise, rather than the complex coastal responses resulting from changes to the extreme wave climate. Here we investigate the 2013/2014 winter wave conditions that severely impacted the Atlantic coast of Europe and demonstrate that this winter was the most energetic along most of the Atlantic coast of Europe since at least 1948. Along exposed open-coast sites, extensive beach and dune erosion occurred due to offshore sediment transport. More sheltered sites experienced less erosion and one of the sites even experienced accretion due to beach rotation induced by alongshore sediment transport. Storm wave conditions such as were encountered during the 2013/2014 winter have the potential to dramatically change the equilibrium state (beach gradient, coastal alignment, and nearshore bar position) of beaches along the Atlantic coast of Europe.

Published
2016

69. Morphodynamic modelling of a wave-dominated tidal inlet : the Albufeira lagoon

Author

Dodet, Guillaume, LIttoral ENvironnement et Sociétés - UMRi 7266 (LIENSs), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), Université de La Rochelle, André Fortunato, and Xavier Bertin

Subjects
Modèle régional de vagues, Analyse de données, Regional wave modelling, Data analysis, Morphodynamic modelling, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Wave-current interactions, Marge ouest-ibérique, Ephemeral inlet dynamics, North-Atlantic Oscillation, Oscillation Nord-Atlantique, Variabilité du climat de vagues, Dynamique des embouchures tidales éphémères, Modélisation morphodynamique, Western Iberia Margin, Wave climate variability, Interactions vague-courant
Abstract

Wave-dominated tidal inlets are very dynamic coastal systems, whose morphology is continuously shaped by the combined action of the waves and the tides. The rapid morphological changes they experience impact directly their ecological and socio-economic environments. In order to implement adequate regulations for the sustainable management of tidal inlets, systematic environmental studies are necessary. The main objective of this PhD research work is to gain a better understanding of the physical processes that control the morphological evolutions of an ephemeral tidal inlet in Portugal - the Albufeira Lagoon inlet - based on the analysis of hydrodynamic and topographic data and on the results of a newly developed morphodynamic modelling system. The processes that impact the dynamics of the inlet at short time-scales, particularly those related to wave-current interactions, are investigated through the application of the modelling system to the inlet. The seasonal modulations of the wave climate and mean sea level strongly affect the sediment dynamics of the inlet and contribute to the natural closure of the inlet during the winter period. Long-term processes are also investigated based on a 65-year hindcast of mean wave parameters at regional and local scales. The large inter-annual variability of the wave climate and the associated longshore sediment transport – both correlated to the North-Atlantic Oscillation – are proposed to explain the differences in the morphological behaviour of the inlet-lagoon system at pluri-annual time-scales.; Les embouchures tidales dominées par la houle sont des systèmes côtiers particulièrement dynamiques dont la morphologie est continuellement remodelée par l’action des vagues et de la marée. Les rapides évolutions morphologiques auxquelles elles sont sujettes impactent directement leurs environnements écologiques et socio-économiques. Afin de mettre en œuvre des réglementations adaptées à la gestion durable des embouchures tidales, des études environnementales systématiques sont nécessaires. L’objectif principal de cette thèse est de mieux comprendre les processus physiques qui contrôlent les évolutions morphologiques d’une embouchure tidale éphémère au Portugal - l’embouchure de la lagune d’Albufeira – à partir de l’analyse de mesures hydrodynamiques et topographiques et de résultats d’un système de modélisation morphodynamique récemment développé. Les processus qui influent sur la dynamique de l’embouchure tidale à court terme, notamment ceux liés aux interactions vague-courant, ont été étudiés à travers l’application du système de modélisation à l’embouchure. Les modulations saisonnières du climat de vagues et du niveau moyen de la mer affectent fortement la dynamique sédimentaire de l’embouchure et contribuent au comblement naturel de l’embouchure pendant l’hiver. Les processus à long terme ont également été étudiés à partir de simulations rétrospectives de paramètres moyens de vagues pour des échelles régionales et locales sur une période 65 ans. Les fortes variabilités interannuelles du climat de vagues et de la dérive littorale qui lui est associée pourraient expliquer les différences d’évolutions morphologiques du système embouchure-lagune sur des échelles de temps pluri–annuels.

Published
2013

71. Morphological evolution of an ephemeral tidal inlet from opening to closure: The Albufeira inlet, Portugal

Author

Fortunato, André B., primary, Nahon, Alphonse, additional, Dodet, Guillaume, additional, Rita Pires, Ana, additional, Conceição Freitas, Maria, additional, Bruneau, Nicolas, additional, Azevedo, Alberto, additional, Bertin, Xavier, additional, Benevides, Pedro, additional, Andrade, César, additional, and Oliveira, Anabela, additional

Published
2014
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73. Wave-current interactions in a wave-dominated tidal inlet

Author

Dodet, Guillaume, Bertin, Xavier, Bruneau, Nicolas, Fortunato, Andre B., Nahon, Alphonse, Roland, Aron, Dodet, Guillaume, Bertin, Xavier, Bruneau, Nicolas, Fortunato, Andre B., Nahon, Alphonse, and Roland, Aron

Abstract

Wave-current interactions play a major role in the dynamics of shallow tidal inlets. This study investigates these interactions at a natural inlet, with a strong focus on current-induced changes on wave propagation. The analysis of hydrodynamic data collected at the Albufeira lagoon, Portugal, revealed spatiotemporal variations of water levels and wave heights along the inlet, attributed to wave-current interaction processes. We compared the simulations of a coupled wave-circulation modeling system, computed with and without waves, and propagated with and without current feedback. The wave-induced setup inside the lagoon represented 7%-15% of the offshore significant wave height. The accuracy of the wave's predictions improved when current feedback was included. During ebb, the currents increased the wave height at the mouth of the inlet (up to 20%) and decreased the wave height in the inlet (up to 40%), due to current-induced refraction, steepness dissipation, and partial blocking. During flood, the currents decreased the wave height in the inlet (up to 10%) and increased the wave height at the exterior parts of the ebb shoal (up to 10%), due to current-induced refraction. These effects significantly attenuate seaward sediment fluxes during ebb and contribute to the sediment accretion in the inlet.

Published
2013
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74. Historical variation and trends in storminess along the Portuguese South Coast

Author

Almeida, L. P., Ferreira, O., Vousdoukas, M. I., Dodet, Guillaume, Almeida, L. P., Ferreira, O., Vousdoukas, M. I., and Dodet, Guillaume

Abstract

This work investigates historical variation and trends in storm climate for the South Portugal region, using data from wave buoy measurements and from modelling, for the period 1952 to 2009. Several storm parameters (annual number of storms; annual number of days with storms; annual maximum and mean individual storm duration and annual 99.8th percentile of significant wave height) were used to analyse: (1) historical storminess trends; (2) storm parameter variability and relationships; and (3) historical storminess and its relationship to the North Atlantic Oscillation (NAO). No statistically significant linear increase or decrease was found in any of the storm parameters over the period of interest. The main pattern of storm characteristics and extreme wave heights is an oscillatory variability with intensity peaks every 7-8 yr, and the magnitude of recent variations is comparable with that of variations observed in the earlier parts of the record. In addition, the results reveal that the NAO index is able to explain only a small percentage of the variation in storm wave height, suggesting that more local factors may be of importance in controlling storminess in this region.

Published
2011
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79. Effect of Inlet Morphology and Wave Action on Pollutant Pathways and Sediment Dynamics in a Coastal Stream

Author

Oliveira, Anabela, primary, Fortunato, André B., additional, Guerreiro, Martha, additional, Bertin, Xavier, additional, Bruneau, Nicolas, additional, Rodrigues, Marta, additional, Taborda, Rui, additional, Andrade, César, additional, Silva, Ana Maria, additional, Antunes, Carlos, additional, Freire, Paula, additional, Pedro, L. Simões, additional, Dodet, Guillaume, additional, Loureiro, Carlos, additional, and Mendes, Ana, additional

Published
2010
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82. Future evolution of a tidal inlet due to changes in wave climate, Sea level and lagoon morphology (Óbidos lagoon, Portugal)

Author

Bruneau, Nicolas, Fortunato, André B., Dodet, Guillaume, Freire, Paula, Oliveira, Anabela, and Bertin, Xavier

Subjects
*CLIMATOLOGY, *ABSOLUTE sea level change, *LAGOONS, *PREDICTION models, *SEDIMENTATION & deposition
Abstract

Abstract: Tidal inlets are extremely dynamic, as a result of an often delicate balance between the effects of tides, waves and other forcings. Since the morphology of these inlets can affect navigation, water quality and ecosystem dynamics, there is a clear need to anticipate their evolution in order to promote adequate management decisions. Over decadal time scales, the position and size of tidal inlets are expected to evolve with the conditions that affect them, for instance as a result of climate change. A process-based morphodynamic modeling system is validated and used to analyze the effects of sea level rise, an expected shift in the wave direction and the reduction of the upper lagoon surface area by sedimentation on a small tidal inlet (Óbidos lagoon, Portugal). A new approach to define yearly wave regimes is first developed, which includes a seasonal behavior, random inter-annual variability and the possibility to extrapolate trends. Once validated, this approach is used to produce yearly time series of wave spectra for the present and for the end of the 21st century, considering the local rotation trends computed using hindcast results for the past 57 years. Predictions of the mean sea level for 2100 are based on previous studies, while the bathymetry of the upper lagoon for the same year is obtained by extrapolation of past trends. Results show, and data confirm, that the Óbidos lagoon inlet has three stable configurations, largely determined by the inter-annual variations in the wave characteristics. Both sea level rise and the reduction of the lagoon surface area will promote the accretion of the inlet. In contrast, the predicted rotation of the wave regime, within foreseeable limits, will have a negligible impact on the inlet morphology. [Copyright &y& Elsevier]

Published
2011
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83. Wave runup over the steep rocky cliffs of Banneg Island, France

Author

Guillaume Dodet, Fabien Leckler, Fabrice Ardhuin, Serge Suanez, Jean-François Filipot, Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN), Service Hydrographique et Océanographique de la Marine (SHOM), Ministère de la Défense, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), France Energies Marines [Brest], DGA PROTEVS (12CR6), Troels Aagaard, Rolf Deigaard, David Fuhrman, ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), Dodet, Guillaume, Laboratoires d'excellence - LabexMER Marine Excellence Research: a changing ocean - - LabexMER2010 - ANR-10-LABX-0019 - LABX - OLD, and Troels Aagaard, Rolf Deigaard, David Fuhrman

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere, Banneg Island, rocky coasts, steep slopes, pressure sensor measurements, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, wave runup, [SDU.ENVI] Sciences of the Universe [physics]/Continental interfaces, environment
Abstract

International audience; The wave runup is known to depend on the offshore wave conditions and the beach slope. While most field studies on wave runup have focused on low-to-mild sloping sandy beaches, runup measurements on steep and irregular rocky beach profiles are still very sparse. Hence, little is known on the physical processes affecting the wave runup in such environments, and the range of applicability of empirical runup formula requires further investigation. This study focuses on the steep (0.1 < tan β < 0.4) rocky cliffs of Banneg Island, a small island of the Iroise Sea occasionally flooded during extreme water level events. A statistical parameter for extreme runup is derived from the measurements of pressure sensors deployed in the intertidal zone. Deep water wave parameters and highresolution topographic data are analyzed concurrently with runup time-series in order to assess the dependence of the runup on hydrodynamic conditions and foreshore slopes. The wave runup is shown to be strongly related to the surf-similarity parameter times the offshore significant wave height. Given the large topographic variability of the beach profile, the method used to compute the beach slope is shown to strongly affects the results.

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