Development of a target-site-based regional frequency model using historical information

Abstract

Nuclear power plants in France are designed to withstand natural hazards. Nevertheless, some exceptional storm surges, considered as outliers, are not properly addressed by classical statistical models. Local frequency estimations can be obtained with acceptable uncertainties if the data set containing the extreme storm surge levels is sufficiently complete and not characterized by the presence of an outlier. Otherwise, additional information such as regional and historical storm surges may be used to mitigate the lack of data and the influence of the outlier by increasing its representativeness in the sample. The objective of the present work is to develop a regional frequency model (RFM) using historical storm surges. Here we propose a RFM using historical information (HI). The empirical spatial extremogram is used herein to form a homogenous region of interest centered on a target site. A related issue regards the reconstitution, at the target site and from its neighbors, of missed storm surges with a multiple linear regression (MLR). MLR analysis can be considered conclusive if available observations at neighboring sites are informative enough and the reconstitution results meet some criteria during the cross-validation process. A total of 35 harbors located on the French (Atlantic and English Channel) and British coasts are used as a whole region with the La Rochelle site as a target site. The Peaks-Over-Threshold frequency model is used. The results are compared to those of an existing model based on the index flood method. The use of HI in the developed RFM increases the representativeness of the outlier in the sample. Fitting results at the right tail of the distribution appear more adequate and the 100-year return level is about 30 cm higher. The 100-year return level in the initial fitting has a return period of about 30 years in the updated fitting.

Regional frequency analysis of extreme storm surges using the extremogram approach

“…Several ideas and approaches have been proposed in the literature to tackle the issue of the delineation of 320 homogeneous regions which is a main step in a RFA. The present work provides a detailed reasoning for the need to use a more robust and reliable method which allows for the delineation of one homogeneous region centered on a target site, and utilizes a method based on the calculation of pairwise extremal dependence coefficients (the empirical spatial extremogram) introduced by Hamdi et al (2016) and compares the results with those obtained by Weiss et al (2014c).…”

“…To form a physically homogeneous region centered on a target site, Hamdi et al (2016) have proposed an approach using the empirical spatial extremogram (ESE) in which the extremal dependence between two observation series becomes a measure of the neighbourhood between the two corresponding sites. A pairwise distance between sites based 60 on the spatial extremal coefficients is defined herein to carry out a RFA applied on extreme SSSs.…”

The use of historical information for regional frequency analysis of extreme skew surge

“…The use of extraordinary floods events in RFA has already been explored by Nguyen et al (2014) for peak discharges and Hamdi et al (2016) have explored it in the frame of oceanic and meteorological variables.…”

Homogenous regions based on extremogram for regional frequency analysis of extreme skew storm surges

“…To form a physically homogeneous region centered on a target site, Hamdi et al (2016) had recently proposed an approach using the spatial extremal dependence between observations (the spatial extremogram) to measure the neighborhood 35 Nat. Hazards Earth Syst.…”