Influence of nonstationarity and dependence of extreme wave parameters on the reliability assessment of coastal structures-A case study

The current general consensus is that because of global climate change, coastal infrastructures may be subject to more extreme loads in the future than in the past. There has been an increased recognition that more attention should be paid to incorporating nonstationarity within the design process of coastal structures. In this regard, the present study examines the reliability of a conventional rubble mound breakwater using a variety of probabilistic techniques, incorporating ten nonstationary models to study the impacts of nonstationarity, as well as six copula functions to explore the dependence effects of wave extremes. The Gumbel copula most accurately represents the dependence structure of wave heights and periods in the study area. When the dependence of wave parameters is not correctly modeled, the failure probability of the studied structure is significantly underestimated. Assuming the Gumbel copula for modeling dependence of wave parameters, the results indicate that the maximum failure probability of the structure is underestimated by about 33% when a stationary extreme value distribution is fitted to wave height extremes, compared to a nonstationary Generalized Pareto Distribution (GPD). The insights gained from this study suggest that considering nonstationarity in extreme coastal events has more significant impacts on the reliability of coastal structures when the dependence structure of the marine variables is accu-rately modeled.