Understanding and Including the Dynamics of Extreme Natural Hazard Event Uncertainty Within the Overall Offshore Wind Farm Project Risk Assessment Using a Causality-Based Graphical Modelling Approach

Offshore wind structures are subject to the combined action of wind and wave loads. A change of these loads may significantly affect the integrity of the structural elements. Increased instabilities in the Earth’s climate system could increase the frequency of extreme events (e.g. rogue waves) well beyond the frequency values currently recommended within structural design standards. Inherent to extreme event modelling is the need to use expert (subjective) judgement and sparse data sets. In this context, a Bayesian Belief Network (BBN) can be applied to describe the effect of these changes on the frequency of rogue waves within wind farms located in shallow water depths of 20–60 meters. This graphical modelling approach provides the structure to effectively communicate, among others, parameter uncertainty, causality across multiple risk factors, quantitative definition of assessment subjectivity or potential impact of a change in rogue wave frequency relative to that described in current design standards.