Environmental contours are commonly applied in design of marine structures to identify extreme environmental conditions that may give rise to extreme loads and responses. Recently, there has been some focus on the fact that different methods exist for establishing such contours, and that in some cases significant differences may be obtained from the different methods.
In this study, we address another uncertainty related to the calculation of environmental contours, namely the uncertainty due to sampling variability when constructing environmental contours based on metocean data of finite sample size. The uncertainty of environmental contours for joint distribution of significant wave height and wave period for different sample sizes (10, 20, 30 and 100 years of data) are investigated considering different underlying datasets. Both cases where samples are drawn from a known joint distribution of wave height and periods and cases where samples are drawn from a real hindcast dataset and fitted to the joint distribution are considered. The uncertainty of the estimated contours is quantified and discussed in light of differences that can be anticipated from the different methods used to calculate the contours.
