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.

通过不同的方法，分别确定了10、25和100年回波期的重要波高和波期的环境等值线。首先通过直接采样和使用Rosenblatt变换的逆一阶可靠性方法（IFORM）导出环境轮廓。然后，将重要性采样技术应用于沿环境轮廓线的不同位置，以减少估计值的方差，从而提高预测方法的准确性和效率。不同的环境轮廓来自加纳利群岛近海的大量后向波数据收集，用作案例研究以比较不同的方法。