Modelling dependence and coincidence of storm surges and high tide: Methodology and simplified case study in Le Havre (France)

Abstract

Abstract. Coastal facilities such as nuclear power plants (NPPs) have to be designed to withstand extreme weather conditions and must, in particular, be protected against coastal floods because it is the most important source of coastal lowlands inundations. Indeed, considering the combination of tide and extreme storm surges (SSs) is a key issue in the evaluation of the risk associated to coastal flooding hazard. Tide and extreme SSs are considered as independent. While there are several approaches to analyze and characterize coastal flooding hazard with either extreme SSs or sea levels, only few studies propose and compare several approaches combining the tide density with the SS variable. Thus this study aims to develop a method for modelling dependence and coincidence of SSs and high tide. In this work, we have used existing methods for tide and SS combination and tried to improve the results by proposing a new alternative approach while showing the limitations and advantages of each method. The city of Le Havre in France was used as a case study. Overall, the example has shown that the return levels estimates using different combinations are quite different. It has also been suggested that the questions of coincidence and dependency are essential for a combined tide and SS hazard analysis.

Modelling coincidence and dependence of flood hazard phenomena in a Probabilistic Flood Hazard Assessment (PFHA) framework: case study in Le Havre

“…and by considering the combination and the dependence of these phenomena. A Ph.D. research is ongoing in the University of Technol ogy of Compiègne (UTC), with a collaboration with IRSN, to develop a PFHA method that takes into account the combination and the dependence of flood phenomena (Ben Daoued et al 2018). The PFHA should provide, for high return periods (1000 years for example), a total probability (or frequency) of exceeding a certain water depth at the site regardless the flood initiating phenomenon.…”