Validation of a 1D Simplified Model of Gironde Estuary Based on a Database of TELEMAC Simulations

Hydrodynamic

The hydrodynamic, sea-state and infrastructures platform developed by Saint-Venant Hydraulics Laboratory and Cerema: a special focus on the TELEMAC2D surge levels numerical model of the Atlantic Ocean, the Channel and the North Sea

Water Qualit

Improving simulations of extreme skew surges through wares' contributions

Water Qualit

Quantification d'incertitudes et assimilation de données pour la modélisation hydrodynamique bidimensionnelle : application au modèle de prévision des hautes eaux de l’estuaire de la Gironde

The accuracy of predictions is a major stake of flood forecast. This thesis deals with the development of data assimilation techniques in bidimensional numerical codes based on shallow water equations and, more specifically, the assessment of possible improvements in high water forecasting in the Gironde estuary through the development and use of these methods. The main characteristics of this work concern the unsteadiness of hydrodynamics, linked to both tidal propagation and the hydrometeorological event, and the correlation between the observations of the different available observation stations.The work carried out during the first part of the thesis focused on the proposal of a methodology for the treatment of uncertainties by global sensitivity analysis and variance decomposition for a code fed by time-dependent variables. This methodology made it possible to classify the sources of uncertainty based on a sample of the achievements of the Telemac2D numerical model for forecasting high water levels in the Gironde estuary, in order to prioritize the influence of the model's forcings and parameters.In a second step, in connection with the results of the previous study, a methodology was proposed to develop a simulation chain integrating the numerical code and an ensemblist data assimilation method, based on an Ensemble Kalman Filter, in order to reduce the uncertainties of the model related to its time-dependent forcings and parameterization. First, this methodology was applied to the Telemac2D model of the Gironde estuary with a twin experiment protocol whose objective is, on the one hand, to validate it and, on the other hand, to optimally determine the control vector, the measurement network and the parameters related to the proposed methodology. The gains for the forecast of water levels in the Gironde estuary are then evaluated using the observations available for several real eventsCette thèse s'inscrit dans le cadre du développement de techniques d'assimilation de données dans les codes de calcul bidimensionnels d'hydraulique à surface libre et, plus particulièrement, de l'évaluation des possibilités d'amélioration de la prévision des hautes eaux sur l'estuaire de la Gironde par le développement et l'utilisation de ces méthodes. Les caractéristiques principales de ces travaux concernent le caractère instationnaire de l'hydrodynamique, liée à la fois à la propagation de la marée et à l'événement hydrométéorologique considéré, et la corrélation entre les observations des différentes stations de mesures disponibles. Les travaux réalisés pendant la première partie de la thèse ont porté sur la proposition d'une méthodologie de traitement des incertitudes par analyse globale de sensibilité par décomposition de variance pour un code d'hydrodynamique alimenté par des variables fonctionnelles. Cette méthodologie a permis la classification des sources d'incertitudes à partir d'un échantillon des réalisations du modèle Telemac2D de prévision des hautes eaux de l'estuaire de la Gironde, dans le but de hiérarchiser l'influence des forçages et des paramètres du modèle. Dans un second temps, en lien avec les résultats de l'étude précédente, une méthodologie a été proposée pour développer une chaîne de simulation intégrant le code de calcul étudié et une méthode ensembliste d'assimilation de données fondée sur le Filtre de Kalman d'Ensemble, dans l'objectif de réduire les incertitudes du modèle liées à ses forçages fonctionnels et à sa paramétrisation par l'utilisation d'observations. Dans un premier temps, cette méthodologie a été appliquée au modèle Telemac2D de l'estuaire de la Gironde sous la forme d'un protocole d'expériences jumelles dont l'objectif est, d'une part, de procéder à sa validation et, d'autre part, de déterminer de manière optimale le vecteur de contrôle, le réseau de mesures et les paramètres liés à la méthodologie proposée. Les gains de la méthodologie proposée sont ensuite évalués en utilisant les observations disponibles pour plusieurs événements réel

Uncertainty quantification and data assimilation for bidimensional hydrodynamics : application to the Gironde Estuary high levels forecast numerical model

Cette thèse s'inscrit dans le cadre du développement de techniques d'assimilation de données dans les codes de calcul bidimensionnels d'hydraulique à surface libre et, plus particulièrement, de l'évaluation des possibilités d'amélioration de la prévision des hautes eaux sur l'estuaire de la Gironde par le développement et l'utilisation de ces méthodes. Les caractéristiques principales de ces travaux concernent le caractère instationnaire de l'hydrodynamique, liée à la fois à la propagation de la marée et à l'événement hydrométéorologique considéré, et la corrélation entre les observations des différentes stations de mesures disponibles. Les travaux réalisés pendant la première partie de la thèse ont porté sur la proposition d'une méthodologie de traitement des incertitudes par analyse globale de sensibilité par décomposition de variance pour un code d'hydrodynamique alimenté par des variables fonctionnelles. Cette méthodologie a permis la classification des sources d'incertitudes à partir d'un échantillon des réalisations du modèle Telemac2D de prévision des hautes eaux de l'estuaire de la Gironde, dans le but de hiérarchiser l'influence des forçages et des paramètres du modèle. Dans un second temps, en lien avec les résultats de l'étude précédente, une méthodologie a été proposée pour développer une chaîne de simulation intégrant le code de calcul étudié et une méthode ensembliste d'assimilation de données fondée sur le Filtre de Kalman d'Ensemble, dans l'objectif de réduire les incertitudes du modèle liées à ses forçages fonctionnels et à sa paramétrisation par l'utilisation d'observations. Dans un premier temps, cette méthodologie a été appliquée au modèle Telemac2D de l'estuaire de la Gironde sous la forme d'un protocole d'expériences jumelles dont l'objectif est, d'une part, de procéder à sa validation et, d'autre part, de déterminer de manière optimale le vecteur de contrôle, le réseau de mesures et les paramètres liés à la méthodologie proposée. Les gains de la méthodologie proposée sont ensuite évalués en utilisant les observations disponibles pour plusieurs événements réelsThe accuracy of predictions is a major stake of flood forecast. This thesis deals with the development of data assimilation techniques in bidimensional numerical codes based on shallow water equations and, more specifically, the assessment of possible improvements in high water forecasting in the Gironde estuary through the development and use of these methods. The main characteristics of this work concern the unsteadiness of hydrodynamics, linked to both tidal propagation and the hydrometeorological event, and the correlation between the observations of the different available observation stations.The work carried out during the first part of the thesis focused on the proposal of a methodology for the treatment of uncertainties by global sensitivity analysis and variance decomposition for a code fed by time-dependent variables. This methodology made it possible to classify the sources of uncertainty based on a sample of the achievements of the Telemac2D numerical model for forecasting high water levels in the Gironde estuary, in order to prioritize the influence of the model's forcings and parameters.In a second step, in connection with the results of the previous study, a methodology was proposed to develop a simulation chain integrating the numerical code and an ensemblist data assimilation method, based on an Ensemble Kalman Filter, in order to reduce the uncertainties of the model related to its time-dependent forcings and parameterization. First, this methodology was applied to the Telemac2D model of the Gironde estuary with a twin experiment protocol whose objective is, on the one hand, to validate it and, on the other hand, to optimally determine the control vector, the measurement network and the parameters related to the proposed methodology. The gains for the forecast of water levels in the Gironde estuary are then evaluated using the observations available for several real event

Evolution of surge levels inside of the Seine Bay : interactions between tide and surge levels during Johanna and Xynthia storms

International audienceWithin the Technical Commission for the Study and the Evaluation of Maritime Submersions in the Seine Estuary (CTeeSMES), which aim is to improve the collective knowledge on physical processes related to maritime surge levels, a numerical model of the Atlantic French Coast based on TELEMAC2D was used to study the evolution of surge levels from the ocean to the harbour area of Le Havre and evaluate the interactions between tide and surge levels in the Seine Bay. The numerical model was specifically calibrated on JOHANNA and XYNTHIA storm events, which respectively occurred in March 2008 and in February 2010. To calibrate the global signal (tide + surge levels), measurements available on 18 outputs of the Atlantic coast were used to optimize the coefficient for wind influence and for bottom friction. Maritime boundary conditions were provided by the North East Atlantic Atlas (LEGOS). Winds and pressure fields were CFSR data. Once the numerical model had been calibrated both for tide and surge levels, it has been possible to draw the evolution of surge levels from the ocean to Le Havre (quai Meunier) and then to compare the signal obtained at each point of the Seine Bay with that obtained without taking into consideration tide for each event. That also allowed to evaluate the contribution of interactions between tide and surge levels inside of the Seine Bay for Xynthia and Johanna events, but also for other events in the slice [1979-2010] and considering climate change towards 2100 with IPCC5 scenarios. It appears that instantaneous interactions between tide and surge levels nearly reach 50 % of the global surge levels and can sharply influence the evolution of surge levels in the Seine Bay depending of the moment (high tide or low water) at which the storm occurs

Modélisation et observation de submersion de dunes en Languedoc-Roussillon

The « coastal squeeze », which basically results in less beach area and more concrete, fortunately does not yet concern the entire Mediterranean coast. It is thus important, while there are still coastal barrier islands, to study and understand the overwash phenomenon, in order to help anticipate the hydrodynamic and sedimentary processes that drive the responses of dunes to important meteorological events. This article first defines and describes the overwash processes that affect coastal dune behaviour, and then presents the analysis carried out by the EID Méditerranée on the beach of Villeneuve les Maguelone, located between Sète and Montpellier in the region of Languedoc Roussillon, France. This analysis allowed us to construct a schema of the responses of the barrier island of Villeneuve les Maguelonne to the meteorological conditions present during the storms of December 3rd and 4th, 2003 and February 21st, 2004. A hydrodynamic model that integrates the radiation stresses (Berkhoff equations) into the Saint-Venant equations was then attempted with the help of the ARTEMIS and TELEMAC calculation codes, in order to characterize the hydrodynamic properties of the system. Finally, a critique of the results is offered and suggestions for improvement are proposed

Future extreme water levels and floodplains in Gironde Estuary considering climate change

International audienc

Evolution of Surge Levels Inside Harbour Basins: the Case of Le Havre Harbour

Within the Technical Commission for the Study and the Evaluation of Maritime Submersions in the Seine Estuary (CTeeSMES), whose aim is to improve the collective knowledge on physical processes linked to maritime surge levels, a numerical model of the Seine estuary based on TELEMAC2D has been used to study the evolution of surge levels from the ocean to the harbour area of Le Havre and, in particular, evaluate the amplification of the global signal and the apparition of seiches inside René Coty''s basin. The bathymetry of the model was partially provided by Le Havre and Rouen Harbours for the north-east part of the model. For the rest of the area, EMODNET was used. The numerical model was calibrated on Johanna (March 2008) and Xynthia (February 2010) storm events. The global signal (tide + surge levels) was calibrated using measurements available on seven outputs of the Seine Estuary and provided by ports of Le Havre and Rouen to optimize the friction coefficient and the coefficient for wind influence. Winds and pressure fields came from CFSR data. Once the numerical model of the Seine Bay had been calibrated, it has been possible to draw the evolution of surge levels from the ocean to Le Havre (quai Meunier) and then to compare the signal obtained inside René Coty harbour basin. As shown by measurements, numerical results stress out the apparition of an oscillating signal which is added to the signal at the entry of the Harbour. The process of amplification of seiche inside the port near the René Coty harbour basin is still underestimated by the model and further investigations must be realised.Laborie Vanessya, Sergent Philippe, Hissel François. Evolution of Surge Levels Inside Harbour Basins: the Case of Le Havre Harbour. In: SimHydro 2014. New Trends in Simulation. 11-13 June 2014 Ecole Polytech’ Nice (France) 2014