Sensitivity Analysis of the Mascaret model on the Odet River

Hydrodynamic

Modélisation hydraulique 2D pour l'évaluation des débits et volumes débordés, cotes atteintes lors de la tempête Xynthia du 28 février 2010

2D hydraulic models to estimate discharges and volumes overflowing, and water levels during the storm Xynthia on 28th February 2010. After the storm Xynthia on 28th February 2011, which severely affected the coasts of Loire-Atlantique, Vendée, Charente-Maritime and Gironde, CETMEF has contributed to the assessment of the discharges and volumes overflowing on the levees, the maximal water levels and the dynamics of overflows, at the instance of the services of State. Several sites have been modelled, such as Faute-sur-Mer and Aiguillon communities in Vendée, and Boucholeurs and Port-des-Barques communities in Charente-Maritime. This communication presents in details the hydraulic modelisation and the results obtained on the community of Portdes-Barques in the estuary of Charente river.Suite à la tempête Xynthia du 28 février 2010, qui a gravement touché les côtes de Loire-Atlantique, de Vendée, de Charente-Maritime et de Gironde, le CETMEF a été sollicité par les services de l'État pour évaluer, par modélisation hydraulique, les débits et volumes débordés sur les digues, les cotes d'eau maximales atteintes et la dynamique des débordements constatés. Plusieurs sites ont fait l'objet de modélisation hydraulique, à savoir la Faute-sur-Mer et l'Aiguillon en Vendée, les Bouchôleurs et Port-des-Barques en Charente-Maritime. La présente communication présente plus en détail le travail de modélisation hydraulique et les résultats obtenus sur la commune de Port-des-Barques dans l'estuaire de la Charente.Chassé Patrick, Tiberi-Wadier Anne-Laure. Modélisation hydraulique 2D pour l'évaluation des débits et volumes débordés, cotes atteintes lors de la tempête Xynthia du 28 février 2010. In: Evénements extrêmes fluviaux et maritimes. Leurs variabilités spatiales et chronologiques dans l'ouest de l’Europe. 34èmes journées de l’hydraulique Paris, 1 et 2 février 2012. 2012

Construction of the Numerical Wave Databases Anemoc-2 on the Mediterranean Sea And The Atlantic Ocean Through Hindcast Simulations over the Period 1979-2010

In the 2000s, CEREMA and EDF R& D have been collaborating to build two continuous wave databases through numerical hindcast simulations : one covers the Atlantic Ocean, the other the Mediterranean Sea. These databases are called ANEMOC. Over the last three years, new versions of the two numerical atlases have been created, in collaboration with Saint-Venant Laboratory. Several improvements have been made in the construction of ANEMOC-2 : the Atlantic model covers a larger area, the temporal coverage of the atlases is larger (32 years from 1979 to 2010), direction and frequency discretization is finer, wind forcing is finer both in time (1 h resolution) and space (0.312°) and the computation meshes are refined to reach 800-1000 m along the French coast. The simulations are performed with the numerical wave model TOMAWAC, a third generation spectral model, which is a module of the TELEMACMASCARET open source suite. The databases are calibrated with altimeters measurements, and validated in a second step against uncorrelated buoys measurements. The databases provide several wave parameters : significant wave height, mean, peak and energy period, mean direction, angular wave spreading and wave power. More results regarding calibration and validation are presented for the Mediterranean wave model. Results of both Mediterranean and Atlantic databases are then presented. Their analyses by comparison with altimeter and buoy measurements provide an assessment of many of their characteristics. Finally, ANEMOC-2 ability to reproduce intense wave conditions is highlighted by the study of two storm events.Tiberi-Wadier Anne-Laure, Laugel Amélie, Benoit Michel. Construction of the Numerical Wave Databases Anemoc-2 on the Mediterranean Sea And The Atlantic Ocean Through Hindcast Simulations over the Period 1979-2010. In: SimHydro 2014. New Trends in Simulation. 11-13 June 2014 Ecole Polytech’ Nice (France) 2014

Étude de sensibilité globale du modèle MASCARET de l'Odet

International audienceA Global Sensitivity Analysis (GSA) is carried out on the Mascaret model of the Odet river (France, Brittany) to identify and rank the major sources of uncertainty at observing stations on the network for the simulated water level, considering the upstream and downstream boundary conditions and the area distributed friction coefficients values. Upstream, ensemble hydrologic forcings are forecasted with the rainfall-runoff distributed model MORDOR-TS, using uncertain hydrologic model parameters drawn from uniform distributions. The downstream maritime boundary condition is perturbed taking into account the temporal correlation of the errors in storm surge. The Sobol' indices are computed at Kervir, Moulin-Vert and Justice stations given hypothesis on the statistical distribution of the aleatory variables. The study focuses on the 23 to the 26 December 2013 event. GSA highlights that the simulated water level at the three stations is mainly controlled by the immediate downstream friction coefficient when the boundary conditions are not perturbed. The flood plain friction coefficients only become important around the peak of the event. However, when the boundary conditions are also taken into account, they become predominant for the simulated water level and the value of the friction coefficients has less influence

PRÉVISIONS D’ENSEMBLE HYDROLOGIQUES AU SEIN DU RÉSEAU NATIONAL DE PRÉVISION DES CRUES EN FRANCE « VIGICRUES » : EXPÉRIMENTATIONS AVEC LE POST-TRAITEMENT DES PRÉVISIONS DANS LE BASSIN DE L’ODET

https://www.shf-hydro.org/wp-content/uploads/2023/11/ColloqueSHFPrevi2023_Resumes-5.pdfInternational audienc

Guidelines for Analysing Coastal Flood Protection Systems after a Submersion

Storm Xynthia, which hit the French Atlantic coast on 28 February 2010, flooded vast territories despite coastal defences. This disaster highlighted the need to further study the behaviour of the coastal flood protection systems at an adapted geographical scale by considering the kinematics of the events. This objective has been achieved through a combination of conceptual input on the definition of protection systems, significant breakthroughs in the knowledge of the mechanisms governing the flooding, and via the improvement of strategies and methods dedicated to flood analysis and representation. The developed methodology was successfully tested on four sites submerged during Xynthia (Loix, Les Boucholeurs, and Boyardville, located in Charente-Maritime, and Batz-sur-Mer, located in Loire-Atlantique). This work is intended to guide the diagnosis of sites prone to marine flooding from the first investigations until the delivery of study reports. Beyond the usual focus on hydraulic structures, it provides guidelines to better analyse the interactions with the natural environment (sea, soil, dune, wetlands, etc.) and with the built environment (roads and urban networks, ponds used for fish farming, buildings, etc.). This systemic approach, which is applied to a territory considered as a complex adaptive system, is fundamental to understanding the reaction of a territory during a marine submersion event and subsequently developing adaptation or transformation strategies

Strategies for hydrologic ensemble generation and calibration: On the merits of using model-based predictors

International audienceThis paper investigates the hydrometeorological chain with an ensemble approach. The objective is the generation of Hydrologic Ensemble Forecasts (HEF) on the Odet catchment (France, Brittany), using the Quantile Regression Forest (QRF) method usually applied for the ensemble calibration of meteorological forecats. First, a Global Sensitivity Analysis (GSA) in the distributed MORDOR-TS model is carried out taking into account uncertainty in forecasted rain with AromeEPS-RR1 and in model parameters. GSA highlights the role and importance of the different hydrologic model parameters during rain events and allows to only take into account the most influent parameters for the generation of an Hydrologic Ensemble Forecast (HEF). Three strategies for the generation of HEF are then compared. First (i), a raw ensemble is built with a model-based only approach using the deterministic forecast rainfall Expert-RR3 and perturbed model parameters, without further statistical calibration. Then, the QRF calibration method is used to generate two ensembles of quantiles: (ii) the observation-based approach uses only predictors that are independent from hydrology, whereas (iii) the combined model and observation approach combines these predictors with statistics of the raw hydrologic ensemble (mean, standard deviation). This latter approach was shown to outperfom the previous ones, enhancing the importance of the choice of the predictors in the QRF method. In the prospect of using the hydrologic ensemble as input for hydraulic simulation, the Ensemble Copula Coupling method (ECC) and a trajectory smoothing procedure is then applied on (iii). This step slightly deteriorates the reliability of hourly streamflows, yet Continuous Ranked Probability Score (CRPS) and forecast skills on the cumulated or maximum streamflows are improved

Guidelines for Analysing Coastal Flood Protection Systems after a Submersion

Storm Xynthia, which hit the French Atlantic coast on 28 February 2010, flooded vast territories despite coastal defences. This disaster highlighted the need to further study the behaviour of the coastal flood protection systems at an adapted geographical scale by considering the kinematics of the events. This objective has been achieved through a combination of conceptual input on the definition of protection systems, significant breakthroughs in the knowledge of the mechanisms governing the flooding, and via the improvement of strategies and methods dedicated to flood analysis and representation. The developed methodology was successfully tested on four sites submerged during Xynthia (Loix, Les Boucholeurs, and Boyardville, located in Charente-Maritime, and Batz-sur-Mer, located in Loire-Atlantique). This work is intended to guide the diagnosis of sites prone to marine flooding from the first investigations until the delivery of study reports. Beyond the usual focus on hydraulic structures, it provides guidelines to better analyse the interactions with the natural environment (sea, soil, dune, wetlands, etc.) and with the built environment (roads and urban networks, ponds used for fish farming, buildings, etc.). This systemic approach, which is applied to a territory considered as a complex adaptive system, is fundamental to understanding the reaction of a territory during a marine submersion event and subsequently developing adaptation or transformation strategies

Etude de sensibilité globale comparée des modèles hydrologiques GRP et MORDOR-TS

International audienc

Vers une approche ensembliste de la prévision des crues

International audienceSCHAPI and SPC (i.e. flood forecasting services) use day-to-day deterministic models, while taking into account rain forecasts and running hydrological and hydraulic forecast models. Each modelling step is affected by uncertainties, which impact the reliability of a deterministic forecast. An ensemble approach is an efficient way to understand forecast uncertainties. A PhD currently underway aims at implementing an ensemble prediction chain from rain forecasting to discharge forecasting, using Meteo France AROME ensemble rain forecast.We describe first the main characteristics that an ensemble forecast should verify to be valuable and the associated tools for assessing it. Raw ensembles from weather forecasting models tend to be underdispersive and biased. Thus they must be post-processed before using them as input of a hydrological model. According to Taillardat et al. (2016), four post-processing methods are used: a non-parametric method based on Quantile Regression Forests (QRF), a semi-parametric one (QRF_TAIL) and two parametric methods EMOS (CNORM and CGAMMA). The analysis of the raw ensemble and post-processed ensembles show that the raw ensemble has yet good qualities. The better results are provided by the QRF methods (QRF and QRF_TAIL).Afin de réaliser les cartes de vigilance bi-quotidiennes, le SCHAPI (Service Central d’Hydrométéorologie et d’Appui à la Prévision des Inondations) et les 19 SPC (Services de Prévision des Crues) utilisent entre autres des résultats de modèles numériques généralement lancés de manière déterministe (prévisions de pluie et de débit hydrologique ou hydraulique). Étant donné le niveau d’incertitudes sur les trois modélisations en jeu, une prévision déterministe chaînée des trois modèles est peu fiable. Une thèse actuellement en cours a pour objectif de mettre en place une chaîne de prévision des crues ensembliste en utilisant les prévisions ensemblistes de pluie AROME. Cette approche devrait permettre de mieux appréhender les incertitudes et de fournir une prévision probabiliste à même de les représenter.Les prévisions brutes issues des modèles de prévision du temps étant le plus souvent sous-dispersives et biaisées, il est nécessaire de les post-traiter avant leur utilisation pour la prévision hydrologique. L’article présente les post-traitements effectués sur les PEAROME selon la méthodologie décrite dans Taillardat et al. (2016). Quatre méthodes de post-traitement sont testées : méthode non-paramétrique basée sur les Quantile Regression Forest (QRF), méthode semi-paramétrique (QRF_TAIL) et deux méthodes paramétriques EMOS (CNORM et CGAMMA). L’analyse des différents ensembles obtenus montre que les prévisions brutes présentent de relativement bonnes caractéristiques. Les méthodes de post-traitement qui donnent les meilleurs résultats sont les méthodes dites QRF