Abstract. To withstand coastal flooding, protection of coastal facilities and structures must be designed with the most accurate estimate of extreme storm surge return levels (SSRLs). However, because of the paucity of data, local statistical analyses often lead to poor frequency estimations. The regional frequency analysis (RFA) reduces the uncertainties associated with these estimations by extending the dataset from local (only available data at the target site) to regional (data at all the neighboring sites including the target site) and by assuming, at the scale of a region, a similar extremal behavior. In this work, the empirical spatial extremogram (ESE) approach is used. This is a graph representing all the coefficients of extremal dependence between a given target site and all the other sites in the whole region. It allows quantifying the pairwise closeness between sites based on the extremal dependence. The ESE approach, which should help with have more confidence in the physical homogeneity of the region of interest, is applied on a database of extreme skew storm surges (SSSs) and used to perform a RFA.

Abstract. To resist marine submersion, coastal protection must be designed by taking into account the most accurate estimate of the return levels of extreme events, such as storm surges. However, because of the paucity of data, local statistical analyses often lead to poor frequency estimations. Regional Frequency Analysis (RFA) reduces the uncertainties associated with these estimations, by extending the dataset from local (only available data at the target site) to regional (data at all the neighboring sites including the target site) and by assuming, at the scale of a region, a similar extremal behavior. RFA, based on the index flood method, assumes that, in a homogeneous region, observations at sites, normalized by a local index, follow the same probability distribution. In this work, the spatial extremogram approach is used to form a physically homogeneous region centered on the target site. The approach is applied on a database of extreme skew storm surges and used to carry out a RFA.

We would like to thank you for reviewing our paper and for the constructive comments. We agree with most of the suggestions and the manuscript will, therefore, be modified to consider your comments. In the point-by-point response (supplement to this post), we recall all the comments and we provide an answer to each of them comments. Your comments are constructive and helped us to improve our paper. Yours sincerely, Yasser Hamdi on behalf of the co-authors.Please also note the supplement to this comment: C1 NHESSD Interactive commentPrinter-friendly version Discussion paper https://www.nat-hazards-earth-syst-sci-discuss.net/nhess-2019-277/nhess-2019-277-AC1-supplement.pdf

Edf-R&D-Chatou a accueilli la conférence internationale EVAN (Advances in Extreme Value Analysis and application to Natural Hazard) du 17 au 19 septembre 2019 réunissant chercheurs, ingénieurs, étudiants et universitaires. Cette conférence a été l’occasion pour tous les professionnels présents de partager leurs expériences et leurs idées sur l’étude des variables géophysiques extrêmes (niveau de la mer, vents, vagues, neige, température, précipitations, débits…) et les travaux liés aux risques naturels (inondations, submersion marine, tempêtes de vent, vagues de chaleur, sécheresses, glissements de terrain, orages, érosion, tremblement de terre et tsunami). Le Laboratoire National d'Hydraulique et Environnement (LNHE) d'EDF et le Laboratoire Saint Venant ont organisé cet évènement avec la Société Hydrotechnique de France (SHF). Trois invités d’honneur, qui ont été très appréciées, sont intervenus au cours ces trois journées d’échanges : (1) Taha Ouarda, professeur d’hydrométéorologie et de statistique à l’INRS (Canada) ; (2) Neil Macdonald, professeur de géographie à Université de Liverpool (UK) ; (3) Dario Camuffo, professeur de physique et membre du « National Research Council » (Italie). Ce que l’on retiendra sans doute de particulier est l’importance des évènements historiques extrêmes naturels permettant, d’une part, d’avoir de longues chroniques d’extrêmes (ce qui est toujours mieux pour faire des statistiques) et aussi permettant une approche très prudente quant à la perception de tendances éventuelles à court ou long terme. Par ailleurs, l’organisation générale a été très bien réussie, et l’on doit, d’ailleurs, remercier l’équipe très professionnelle du Campus de Chatou qui est d’une aide précieuse pour le succès de la conférence. Le cycle des conférences EVAN continue car en 2021, cela se déroulera à l’université de Floride et, en 2023, à Venise. Enfin, un « Special Issue » de la revue internationale NHESS va être ouvert aux participants de la conférence EVAN 2019, avec une soumission possible avant le 31 mars 2020.

We would like to thank you for reviewing our paper and for the constructive comments. We agree with most of the suggestions and the manuscript will, therefore, be modified to consider your comments. In the point-by-point response (supplement to this post), we recall all the comments and we provide an answer to each of them comments. Your comments are constructive and helped us to improve our paper. Yours sincerely, Yasser Hamdi on behalf of the co-authors.Please also note the supplement to this comment: C1 NHESSD Interactive commentPrinter-friendly version Discussion paper https://www.nat-hazards-earth-syst-sci-discuss.net/nhess-2019-277/nhess-2019-277-AC2-supplement.pdf