Publications

2014

• Flow pattern at a river diffluence at the alluvial system of the Paraná River
  
  • Morell M.I.
  • Tassi Pablo
  • Vionnet C.A.
  Journal of Applied Water Engineering and Research, Taylor & Francis Online, 2014, 2 (2), pp.140 - 156. This communication presents field and numerical data depicting the flow pattern formed at a diffluence of the Colastiné River, Argentina, where one branch accesses the local harbour. The harbour has been in decline since the 1970s due to costly maintenance dredging of the access channel. The objective of this work is thus twofold: to show the persistence of the flow pattern developed at the diffluence despite recent morphological changes seen at the site, and to test a possible solution to the access channel sedimentation problem. Knowledge gained during the execution of the study helped to validate a code developed to process field data captured with two acoustic Doppler current profilers (ADCPs). The results confirm that both branches are prone to developing secondary currents. Simulations show that an engineering intervention downstream of the bifurcation can establish a self-dredging flow reversal along the access channel, turning the actual diffluence into a stable confluence. (10.1080/23249676.2014.981371)
  DOI : 10.1080/23249676.2014.981371
• Adaptation of coastal structures to mean sea level rise
  
  • Sergent Philippe
  • Prevot Guirec
  • Mattarolo Giovanni
  • Brossard Jérôme
  • Morel Gilles
  • Mar Fatou
  • Benoit Michel
  • Ropert François
  • Kergadallan Xavier
  • Trichet Jean-Jacques
  • Mallet Pascal
  La Houille Blanche - Revue internationale de l'eau, EDP Sciences, 2014 (6), pp.54-61. (10.1051/lhb/2014063)
  DOI : 10.1051/lhb/2014063
• Integrated urban flood risk management approach in context of uncertainties: case study Ho Chi Minh city
  
  • Ho Long Phi
  • Nguyen Thong
  • Chau Nguyen Xuan Quang
  • Nguyen Kim Dan
  La Houille Blanche - Revue internationale de l'eau, EDP Sciences, 2014 (6), pp.26-33. (10.1051/lhb/2014059)
  DOI : 10.1051/lhb/2014059
• Impact of climate change on Gironde estuary
  
  • Laborie Vanessya
  • Hissel François
  • Sergent Philippe
  La Houille Blanche - Revue internationale de l'eau, EDP Sciences, 2014 (6), pp.34-39. (10.1051/lhb/2014060)
  DOI : 10.1051/lhb/2014060
• Wave climate projections along the French coastline: Dynamical versus statistical downscaling methods
  
  • Laugel Amélie
  • Menendez Melisa
  • Benoit Michel
  • Mattarolo Giovanni
  • Méndez Fernando
  Ocean Modelling, Elsevier, 2014, 84, pp.35-50. (10.1016/j.ocemod.2014.09.002)
  DOI : 10.1016/j.ocemod.2014.09.002
• Modélisation des interactions dans une ferme de systèmes houlomoteurs avec prise en compte de la bathymétrie
  
  • Charrayre François
  • Benoit Michel
  • Peyrard Christophe
  • Babarit Aurélien
  , 2014. Un champ de vagues interagit avec son environnement, qu'il soit naturel (falaise, bathymetrie, ...) ou artificiel (corps ottants, digues, ...). Ainsi, la presence d'une ferme houlomotrice aura un impact sur le champ de houle. A contrario, on peut aussi dire que le rendement des systemes houlomoteurs depend de leurs positions et du champ de vagues incident. Nous proposons ici une methode dont le but est de calculer rapidement ces interactions entre les systemes houlomoteurs, tout en prenant en compte la bathymetrie qui peut avoir un impact non negligeable sur le champ de vagues. Une methodologie de couplage entre un modele local de radiation/ diffraction autour de chaque WEC, et un modele de propagation a fond variable est developpee, puis validee dans un cas a fond plat. Appliquee tout d'abord a une houle incidente monochromatique, cette demarche permet aussi de faire des etudes pour des etats de mer irreguliers multidirectionnels.
• A New Incompressible SPH Model: Towards Industrial Applications
  
  • Leroy Agnès
  , 2014. In this work a numerical model for fluid flow simulation was developed, based on the Smoothed Particle Hydrodynamics (SPH) method. SPH is a meshless Lagrangian Computational Fluid Dynamics (CFD) method that offers some advantages compared to mesh-based Eulerian methods. In particular, it is able to model flows presenting highly distorted free-surfaces or interfaces. This work tackles four issues concerning the SPH method: the imposition of boundary conditions, the accuracy of the pressure prediction, the modelling of buoyancy effects and the reduction of computational time. The aim is to model complex industrial flows with the SPH method, as a complement of what can be done with mesh-based methods. Typically, the targetted problems are 3-D free-surface or confined flows that may interact with moving solids and/or transport scalars, in particular active scalars (e.g. temperature). To achieve this goal, a new incompressible SPH (ISPH) model is proposed, based on semi-analytical boundary conditions. This technique for the representation of boundary conditions in SPH makes it possible to accurately prescribe consistent pressure boundary conditions, contrary to what is done with classical boundary conditions in SPH. A k-epsilon turbulence closure is included in the new ISPH model. A buoyancy model was also added, based on the Boussinesq approximation. The interactions between buoyancy and turbulence are modelled. Finally, a formulation for open boundary conditions is proposed in this framework. The 2-D validation was performed on a set of test-cases that made it possible to assess the prediction capabilities of the new model regarding isothermal and non-isothermal flows, in laminar or turbulent regime. Confined cases are presented, as well as free-surface flows (one of them including a moving rigid body in the flow). The open boundary formulation was tested on a laminar plane Poiseuille flow and on two cases of propagation of a solitary wave. Comparisons with mesh-based methods are provided with, as well as comparisons with a weakly-compressible SPH (WCSPH) model using the same kind of boundary conditions. The results show that the model is able to represent flows in complex boundary geometries, while improving the pressure prediction compared to the WCSPH method. The extension of the model to 3-D was done in a massively parallel code running on a Graphic Processing Unit (GPU). Two validation cases in 3-D are presented, as well as preliminary results on a simple 3-D application case.
• A new incompressible SPH model : towards industrial applications
  
  • Leroy Agnes
  , 2014. In this work a numerical model for fluid flow simulation was developed, based on the Smoothed Particle Hydrodynamics (SPH) method. SPH is a meshless Lagrangian Computational Fluid Dynamics (CFD) method that offers some advantages compared to mesh-based Eulerian methods. In particular, it is able to model flows presenting highly distorted free-surfaces or interfaces. This work tackles four issues concerning the SPH method : the imposition of boundary conditions, the accuracy of the pressure prediction, the modelling of buoyancy effects and the reduction of computational time. The aim is to model complex industrial flows with the SPH method, as a complement of what can be done with mesh-based methods. Typically, the targetted problems are 3-D free-surface or confined flows that may interact with moving solids and/or transport scalars, in particular active scalars (e.g. the temperature). To achieve this goal, a new incompressible SPH (ISPH) model is proposed, based on semi-analytical boundary conditions. This technique for the representation of boundary conditions in SPH makes it possible to accurately prescribe consistent pressure boundary conditions, contrary to what is done with classical boundary conditions in SPH. A k-epsilon turbulence closure is included in the new ISPH model. A buoyancy model was also added, based on the Boussinesq approximation. The interactions between buoyancy and turbulence are modelled. Finally, a formulation for open boundary conditions is proposed in this framework. The 2-D validation was performed on a set of test-cases that made it possible to assess the prediction capabilities of the new model regarding isothermal and non-isothermal flows, in laminar or turbulent regime. Confined cases are presented, as well as free-surface flows (one of them including a moving body in the flow). The open boundary formulation was tested on a laminar plane Poiseuille flow and on two cases of propagation of a solitary wave. Comparisons with mesh-based methods are provided with, as well as comparisons with a weakly-compressible SPH (WCSPH) model using the same kind of boundary conditions. The results show that the model is able to represent flows in complex boundary geometries, while improving the pressure prediction compared to the WCSPH method. The extension of the model to 3-D was done in a massively parallel code running on a Graphic Processing Unit (GPU). Two validation cases in 3-D are presented, as well as preliminary results on a simple 3-D application case (10.70675/6d47acd9z4011z407ez8d82z53bdb8cd2447)
  DOI : 10.70675/6d47acd9z4011z407ez8d82z53bdb8cd2447
• Estimation of Lateral Inflows Using Data Assimilation in the Context of Real-Time Flood Forecasting for the Marne Catchment in France
  
  • Habert Johan
  • Ricci Sophie
  • Piacentini Andrea
  • Jonville Gabriel
  • Le Pape Etienne
  • Thual Olivier
  • Goutal Nicole
  • Zaoui Fabrice
  • Ata Riadh
  , 2014, pp.93-105. The present study describes the assimilation of discharge in situ data for operational flood forecasting. The study was carried out on the Marne River (France) catchment where lateral inflows’ uncertainty is important due to karstic areas. This source of error was partly accounted for using an Extended Kalman Filter (EKF) algorithm built on the top of a mono-dimensional hydraulic model. The lateral inflows were sequentially adjusted over a sliding 48 h time window. The correction leads to a significant improvement in the simulated water level and discharge in re-analysis and forecast modes. These results pave the way for the operational use of the data assimilation (DA) procedure for real-time forecasting at the French flood forecasting service. (10.1007/978-981-4451-42-0_8)
  DOI : 10.1007/978-981-4451-42-0_8
• Analyse régionale des aléas maritimes extrêmes
  
  • Weiss Jérôme
  , 2014. Connaître la probabilité d'occurrence des aléas océano-météorologiques extrêmes est fondamental pour prévenir les risques de submersion marine en zone côtière ou concevoir des aménagements côtiers, portuaires ou des plate-formes offshore. Notamment, le concept de niveau de retour est fréquemment utilisé en ingénierie côtière pour dimensionner des ouvrages de protection. Ces niveaux, dont les périodes de retour d'intérêt se situent généralement entre 100 et 1000 ans, sont habituellement estimés par une analyse statistique locale, à partir de données observées en un site unique. Cependant, la période d'observation est généralement limitée, de sorte que les incertitudes associées aux niveaux de retour élevés sont importantes. L'analyse régionale représente une solution possible pour réduire les incertitudes inhérentes aux analyses locales. Le principe est d'exploiter l'information de sites d'observation provenant d'une région homogène, où les extrêmes sont supposés avoir un comportement probabiliste similaire. L'analyse régionale peut ainsi estimer les niveaux de retour de manière plus fiable qu'une analyse locale. Cependant, son application dans le domaine maritime étant relativement limitée et récente, différentes questions méthodologiques de meurent non-Résolues, comme la formation des régions homogènes ou le traitement de la dépendance entre sites. L'objectif scientifique de la thèse est donc d'approfondir certains points méthodologiques de l'analyse régionale, dans le cadre des aléas maritimes extrêmes. Les points suivants sont abordés en particulier :• Échantillonnage des extrêmes pour l'analyse régionale, à partir des tempêtes détectées via une procédure de declustering spatio-Temporel.• Formation de régions homogènes à partir d'une méthode basée sur l'identification des empreintes typiques des tempêtes.• Prise en compte de la dépendance entre sites d'observation, à travers la construction d'un modèle permettant par exemple d'évaluer la durée effective régionale d'observation ou la période de retour régionale d'une tempête.• Spécification et estimation de la loi régionale, avec incorporation des co-variables influentes, comme la saison d'occurrence ou la direction de provenance pour les vagues.• Comparaison entre analyses locale et régionale, notamment à travers les incertitudes sur les estimations des extrêmes et la capacité à modéliser les horsains présumés.Ces aspects sont illustrés sur des données de hauteurs significatives de vagues et de surcotes de pleine mer, dans la zone Atlantique Nord-Est, Manche et Mer du Nord.Parallèlement, l'objectif applicatif de ces travaux est de contribuer à garantir la sûreté des ouvrages EDF contre le risque de submersion marine. Ceci peut être réalisé grâce à l'exploration de nouvelles techniques d'estimation des aléas maritimes extrêmes telles que l'analyse régionale, qui permet notamment une meilleure prise en compte des horsains. (10.70675/bfc93ae2ze002z4617zbb9ez86d4fe7bc81e)
  DOI : 10.70675/bfc93ae2ze002z4617zbb9ez86d4fe7bc81e
• An investigation of the effects of wind-induced inclination on floating wind turbine dynamics: heave plate excursion
  
  • Antonutti Raffaello
  • Peyrard Christophe
  • Johanning Lars
  • Incecik Atilla
  • Ingram David
  Ocean Engineering, Elsevier, 2014, 91, pp.208-217. (10.1016/j.oceaneng.2014.09.008)
  DOI : 10.1016/j.oceaneng.2014.09.008
• Approaches to evaluate the recent impacts of sea-level rise on shoreline changes
  
  • Le Cozannet Gonéri
  • Garcin Manuel
  • Yates Marissa L.
  • Idier Déborah
  • Meyssignac Benoit
  Earth-Science Reviews, Elsevier, 2014, 138, pp.47-60. While global sea level has risen by 20 cm since the mid-19th century, the role of this process in present-day and past shoreline mobility is still debated. In this paper, we review previous studies that explored the relations between sea-level rise and shoreline changes over the last few decades. Existing methods can be classified into two groups: (1) approaches based on the analysis of trends and variability in shoreline change observations, which investigate whether a correlation with the temporal or spatial patterns sea level changes can be established; and (2) approaches based on the comparison of shoreline observations with a coastal model outcome, which attempt to evaluate the contribution of sea-level rise to shoreline mobility using coastal evolution modeling tools. The existing applications of these methods face two common difficulties: first, shoreline data are often lacking or insufficiently resolved temporally to capture the dynamics of coastlines; and second, relative sea level along the coast is generally only known in a limited number of areas where tide gauges are available. These two challenges can be met, owing to the increasing amount of shoreline change observations and complementary geodetic techniques. The wide range of different interpretations regarding the role of sea-level rise in recent shoreline changes highlights the necessity to conduct specific studies that rely on local observations and models applicable in the local geomorphological context. (10.1016/j.earscirev.2014.08.005)
  DOI : 10.1016/j.earscirev.2014.08.005
• Wake-induced vibrations of an elastically mounted cylinder located downstream of a stationary larger cylinder at low Reynolds numbers
  
  • Wang Huakun
  • Yang Wenyu
  • Nguyen Kim Dan
  • Yu Guoliang
  Journal of Fluids and Structures, Elsevier, 2014, 50 (10), pp.479-496. (10.1016/j.jfluidstructs.2014.07.006)
  DOI : 10.1016/j.jfluidstructs.2014.07.006
• A fast finite volume solver for multi-layered shallow water flows with mass exchange
  
  • Tassi Pablo
  • Audusse Emmanuel
  • Benkhaldoun Fayssal
  • Sari Saida
  • Seaid Mohammed
  Journal of Computational Physics, Elsevier, 2014, 272, pp.23 - 45. (10.1016/j.jcp.2014.04.026)
  DOI : 10.1016/j.jcp.2014.04.026
• Modeling intersite dependence for regional frequency analysis of extreme marine events
  
  • Weiss Jérôme
  • Bernardara Pietro
  • Benoit Michel
  Water Resources Research, American Geophysical Union, 2014, 50 (7). (10.1002/2014WR015391)
  DOI : 10.1002/2014WR015391
• Design and analysis of a Schwarz coupling method for a dimensionally heterogeneous problem
  
  • Tayachi Pigeonnat Manel
  • Rousseau Antoine
  • Blayo Eric
  • Goutal Nicole
  • Martin Véronique
  International Journal for Numerical Methods in Fluids, Wiley, 2014, 75 (6), pp.446-465. In the present work, we study and analyze an efficient iterative coupling method for a dimensionally heterogeneous problem . We consider the case of 2-D Laplace equation with non symmetric boundary conditions with a corresponding 1-D Laplace equation. We will first show how to obtain the 1-D model from the 2-D one by integration along one direction, by analogy with the link between shallow water equations and the Navier-Stokes system. Then, we will focus on the design of an Schwarz-like iterative coupling method. We will discuss the choice of boundary conditions at coupling interfaces. We will prove the convergence of such algorithms and give some theoretical results related to the choice of the location of the coupling interface, and the control of the difference between a global 2-D reference solution and the 2-D coupled one. These theoretical results will be illustrated numerically. (10.1002/fld.3902)
  DOI : 10.1002/fld.3902
• Modelling of wave attenuation induced by multi-purpose floating structures
  
  • Stratigaki V.
  • Troch Peter
  • Stallard T.
  • David Forehand
  • Jens-Peter Kofoed
  • Matt Folley
  • Babarit Aurélien
  • Benoit Michel
  , 2014.
• Data Assimilation with an Ensemble Kalman Filter Algorithm on an Operational Hydraulic Network
  
  • Barthélémy Sébastien
  • Ricci Sophie
  • Goutal Nicole
  • Thual Olivier
  • Le Pape Etienne
  , 2014. This study describes the implementation and the merits of an Ensemble Kalman Filter algorithm (EnKF) on the 1Dshallow water model MASCARET for the representation of the hydrodynamics of the " Adour maritime" river in south west France. The first part of this work is dedicated to a detailed analysis of the background error covariance functions that are stochastically estimated on an ensemble of MASCARET integrations forced by perturbed upstream boundary conditions. It is shown that the geometric characteristics of the network have a significant impact on the shape of these functions and thus on the data assimilation correction. The data assimilation algorithm is validated in the framework of Observating System Simulation Experiment ; it is shown that the assimilation of in-situ water level observations allows to improve water level and discharge over the entire hydraulic network, where no data are available. Finally, the method is applied in the context of real data experiments for recent major flood events of the Adour catchment. The algorithm provides a corrected hydraulic state that can be used as an initial condition for further forecast as well as an input for 1D/ 2D model coupling.
• Coupling 3D Navier-Stokes and 1D shallow water models
  
  • Daou Mehdi Pierre
  • Blayo Eric
  • Rousseau Antoine
  • Bertrand Olivier
  • Tayachi Pigeonnat Manel
  • Coulet Christophe
  • Goutal Nicole
  , 2014. The present work addresses the problem of coupling hydrodynamical models with different spatial dimensions, which can be used in order to reduce the computational cost of river numerical models. We show that this problem can be tackled quite efficiently by designing a simple algorithm using techniques borrowed from domain decomposition theory. This algorithm is non intrusive, i.e. allows using existing numerical models with very few modifications. The method is illustrated on an academic test-case, namely a free surface flow in a bend-shaped channel. A 3-D Navier-Stokes model is coupled with a 1-D shallow water model, and results are compared to those obtained in a fully 3-D case. It is shown that the coupling algorithm provides an accurate solution, which can be improved thanks to an iterative algorithm (Schwarz method). This study is performed using the Mascaret-Telemac system.
• A coupled methodology for wave body interactions at the scale of a farm of wave energy converters including irregular bathymetry
  
  • François Charrayre
  • Peyrard Christophe
  • Benoit Michel
  • Babarit Aurélien
  , 2014. Knowledge of the wave perturbation caused by an array of Wave Energy Converters (WEC) is of great concern, in particular for estimating the interaction effects between the various WECs and determining the modification of the wave field at the scale of the array, as well as possible influence on the hydrody-namic conditions in the surroundings. A better knowledge of these interactions will also allow a more efficient layout for future WEC farms. The present work focuses on the interactions of waves with several WECs in an array. Within linear wave theory and in frequency domain, we propose a methodology based on the use of a BEM (Boundary Element Method) model (namely Aquaplus) to solve the radiation-diffraction problem locally around each WEC, and to combine it with a model based on the mild slope equation at the scale of the array. The latter model (ARTEMIS software) solves the Berkhoff's equation in 2DH domains (2 dimensional code with a z-dependence), considering irregular bathymetries. In fact, the Kochin function (a far field approximation) is used to propagate the perturbations computed by Aquaplus into Artemis, which is well adapted for a circular wave representing the perturbation of an oscillating body. This approximation implies that the method is only suitable for well separated devices. A main advantage of this coupling technique is that Artemis can deal with variable bathymetry. It is important when the wave farm is in shallow water or in nearshore areas. The methodology used for coupling the two models, with the underlying assumptions is detailed first. Validations test-cases are then carried out with simple bodies (namely heaving vertical cylinders) to assess the accuracy and efficiency of the coupling scheme. These tests also allow to analyze and to quantify the magnitude of the interactions between the WECs inside the array. (10.1115/OMAE2014-23457)
  DOI : 10.1115/OMAE2014-23457
• Comparison of fully non linear and weakly nonlinear potential flow solvers for the study of wave energy converters undergoing large amplitude of motions
  
  • Letournel Lucas
  • Harris Jeffrey C.
  • Ferrant Pierre
  • Babarit Aurélien
  • Ducrozet Guillaume
  • Benoit Michel
  • Dombre Emmanuel
  , 2014. We present a comparison between two distinct numerical codes dedicated to the study of wave energy converters. Both are developed by the authors, using a boundary element method with linear triangular elements. One model applies fully nonlin-ear boundary conditions in a numerical wavetank environnment (and thus referred later as NWT), whereas the second relies on a weak-scatterer approach in open-domain and can be considered a weakly nonlinear potential code (referred later as WSC). For the purposes of comparison, we limit our study to the forces on a heaving submerged sphere. Additional results for more realistic problem geometries will be presented at the conference. INTRODUCTION Among the marine renewable energy sources, wave energy is a promising option. Despite the great number of technologies that have been proposed, currently no wave energy converter (WEC) has proven its superiority over others and become a technological solution. Usual numerical tools for modeling and designing WECs are based on boundary elements methods in linear potential theory [1-4]. However WECs efficiency relies on large amplitude motions [5], with a design of their resonance frequencies in the wave excitation. Linear potential theory is thus inadequate to study the behavior of WEC in such configuration. (10.1115/OMAE2014-23912)
  DOI : 10.1115/OMAE2014-23912
• A physical, movable-bed model for non-uniform sediment transport, fluvial erosion and bank failure in rivers
  
  • El Kadi Abderrezzak Kamal
  • Die Moran Andres
  • Mosselman Erik
  • Bouchard Jean Pierre
  • Habersack Helmut
  • Aelbrecht Denis
  Journal of Hydro-environment Research, Elsevier, 2014, 8 (2), pp.95-114. Sediment transport processes in rivers continue to pose a challenge when designing movable-bed physical models, particularly for reproducing the grain sorting and bank erosion (fluvial erosion and mass failure). This paper presents and discusses scale effects of a specific scaling approach for multi-grain size mixtures that preserves similarity of initial motion for each grain size class and of the bank stability coefficient between the model and the prototype, but relaxes strict similarity of the Shields and particle Reynolds numbers. This approach is appropriate when bed load transport near incipient motion conditions is being studied, and allows for larger grain size scales than when full Shields parameter similarity is enforced. As part of an environmental project to rehabilitate sediment transport through bank erosion, this method has been applied to scale a Froude number criterion physical model of a reach of the Old Rhine (France). This has resulted in an undistorted scale of 40, and the use of sand as the model bank material. Each grain size has a different geometrical scale. The time scale for sediment motion is grain size and flow discharge dependent. An average time scale of 6 has therefore been used (four model hours = one prototype day). A strategy devised for the field case consists of two higher, larger island groynes that replace the three existing groynes, producing bank erosion for flow rates below the mean annual flow rate. Extrapolation of model behaviour to the prototype is not a major problem, but the volume of eroded bank material may be underestimated, mainly because of the relaxation of the Shields number similarity and the apparent cohesive properties of the model bank material. (10.1016/j.jher.2013.09.004)
  DOI : 10.1016/j.jher.2013.09.004
• Modelling intersite dependence for regional frequency analysis of extreme marine events
  
  • Weiss Jérôme
  • Bernardara Pietro
  • Benoit Michel
  , 2014. The duration of observation at a site of interest is generally too low to reliably estimate marine extremes. Regional frequency analysis (RFA), by exploiting the similarity between sites, can help to reduce uncertainties inherent to local analyses. Extreme observations in a homogeneous region are especially assumed to follow a common regional distribution, up to a local index. The regional pooling method, by gathering observations from different sites into a regional sample, can be employed to estimate the regional distribution. However, such a procedure may be highly affected by intersite dependence in the regional sample. This paper derives a theoretical model of intersite dependence, dedicated to the regional pooling method in a "peaks over threshold" framework. This model expresses the tendency of sites to display a similar behavior during a storm generating extreme observations, by describing both the storm propagation in the region and the storm intensity. The proposed model allows the assessment of i) the regional effective duration of the regional sample and ii) different regional hazards, e.g., return periods of storms. An application to the estimation of extreme significant wave heights from the numerical sea-state database ANEMOC-2 is provided, where different patterns of regional dependence are highlighted.
• Modelling intersite dependence for regional frequency analysis of extreme marine events
  
  • Weiss Jérôme
  • Bernardara Pietro
  • Benoit Michel
  , 2014. The duration of observation at a site of interest is generally too low to reliably estimate marine extremes. Regional frequency analysis (RFA), by exploiting the similarity between sites, can help to reduce uncertainties inherent to local analyses. Extreme observations in a homogeneous region are especially assumed to follow a common regional distribution, up to a local index. The regional pooling method, by gathering observations from different sites into a regional sample, can be employed to estimate the regional distribution. However, such a procedure may be highly affected by intersite dependence in the regional sample. This paper derives a theoretical model of intersite dependence, dedicated to the regional pooling method in a "peaks over threshold" framework. This model expresses the tendency of sites to display a similar behavior during a storm generating extreme observations, by describing both the storm propagation in the region and the storm intensity. The proposed model allows the assessment of i) the regional effective duration of the regional sample and ii) different regional hazards, e.g., return periods of storms. An application to the estimation of extreme significant wave heights from the numerical sea-state database ANEMOC-2 is provided, where different patterns of regional dependence are highlighted.
• A 2D reconstruction for the transverse coupling of shallow water models
  
  • Goutal Nicole
  • Parisot Martin
  • Zaoui Fabrice
  International Journal for Numerical Methods in Fluids, Wiley, 2014, 75 (11), pp.24. This work is dedicated to the modeling of exchanges between a river and its surrounding floodplains during floods overflowing its bed. Modeling flows in each subdomain, that of the river and that of the floodplain, has been the subject of numerous works for over 50 years and is now well understood. A coupling strategy is considered in order to preserve the advantages of 1D and 2D models in their respective subdomains. In comparison with other transverse coupling strategies already presented in the literature, we introduce a direct method, without overlapping the models or introducing numerical parameters. This strategy is based on the resolution of the Riemann 2D problem at the coupling interface (the bank) and requires the estimation of the transverse velocity close to the interface. We propose a model of transverse velocity using successive resolutions of Riemann problems. Then, we present a numerical resolution of the coupling system, based on a finite volume method for any Riemann solvers. Particular attention was given to the essential properties of the model (conservation of mass, positivity of water depth, and well-balanced scheme). Lastly, the precision and efficiency of the method are illustrated using examples of simulations. (10.1002/fld.3913)
  DOI : 10.1002/fld.3913