Environmental wave contours by inverse FORM and Monte Carlo Simulation with variance reduction techniques

Environmental contours of significant wave height and wave period are established for 10, 25 and 100 year return periods by different approaches. The environmental contours are first derived by Direct sampling and by the Inverse First Order Reliability method (IFORM) using the Rosenblatt transformation. Then, the importance sampling technique is applied at different locations along the environmental contours to reduce the variance of the estimates and, consequently, to increase the accuracy and efficiency of the prediction method. The different environmental contours are derived from a large collection of hindcast wave data from offshore of Canary Islands, which is used as a case study to compare the different approaches.