Comparative Analysis of Available Wave Hindcast Models for the North Sea and their Influence on the Design of Offshore Scour Protections

Abstract

Offshore wind structures often use bottom-fixed foundations that are susceptible to scour phenomena. The design of scour protections for such structures requires defining the physical actions that they must be able to withstand during their lifetime. In this context, hindcasts providing estimates of necessary metocean variables can play a key role. However, it is unclear to which extent the selection of hindcast datasets can influence the design of scour protections at a given location. Moreover, defining design actions requires estimating extreme sea states with return periods exceeding the length of hindcast time series using inferential statistical techniques. This introduces additional uncertainty in the modelling process, which is exacerbated by the fact that different statistical models may perform differently when applied to different hindcast datasets. A better understanding of the effects of these modelling choices is therefore necessary for the design and optimization of scour protections. In this context, the present study compares different wave hindcasts for the North Sea and analyses how their selection, as well as the subsequent application of various statistical models, influences the estimated probabilities of failure of the armour layer for bottom-fixed monopile foundations, considering a dynamically stable design criterion. The results show that the hindcast dataset selection significantly affects the estimates of the probabilities of failure for this type of scour protection. (c) 2022 IAHR.