Extreme Offshore Wave Statistics In
The North Sea
Author(s)
K. Roscoe, S. Caires, F. Diermanse & J. Groeneweg
Abstract
As part of the flood risk assessment in The Netherlands, extreme hydraulic
boundary conditions (HBC) at coastal water defenses are calculated to assess the
safety and sufficiency of the defenses. For this purpose, extreme offshore values
of wave height and wave period with a frequency of occurrence of 1/10,000
years need to be estimated. The estimation is carried out using measurements at
nine offshore locations in the North Sea, with a record length of 30 years.
To estimate extreme wave heights and wave periods, the Generalized Pareto
Distribution (GPD), which follows from extreme value theory, was fitted to
peaks-over-threshold (POT) at each of the nine measurement stations. The fitted
GPD parameters and consequently the extrapolated extreme values are
particularly sensitive to the choice of threshold. A reproducible method was
employed for threshold selection based on the anticipated behavior of the GPD
shape parameter as the threshold approaches the domain of attraction. A
modified regional frequency analysis (MRFA) was subsequently carried out to
spatially smooth the GPD shape parameters. Final GPD fits were made using the
shape-parameter output of the MRFA to produce final extrapolated extreme
value estimates. The extreme values were compared with those resulting from an
operationally-used distribution function in The Netherlands known as the
conditional Weibull distribution.
Keywords: extreme value theory, flood risk, threshold selection, generalized
Pareto distribution, extreme wave parameters.
Keywords
extreme value theory, flood risk, threshold selection, generalizedPareto distribution, extreme wave parameters
Related Book
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