Effect of threshold values on the predicted extreme waves : a case study for the Arabian Gulf

الملخص EN

-The effect of varying the threshold value on the predicted extreme significant wave height is investigated.

Thirty-eight different locations in the Arabian Gulf are used for this case study.

The threshold value is varied from 0.75 m to 4.5 m with an increment of 0.25 m.

Gumbel and We bull extreme value distributions are used for the extreme wave analysis and the We bull distribution is found to be better for all the locations.

The value of the shape parameter of the We bull distribution is varied from 0.8 to 1.3 with an increment of 0.05 and the best shape parameter is selected (based on the highest coefficient of regression value) and the corresponding location and scale parameters are used for predicting the extreme significant waves of different return periods.

It is found that there is no definite trend in the predicted extreme significant wave height, when the threshold value is varied from 0.75 m to 4.5 m, for different selected locations.

For some locations, the predicted extreme significant wave height is found to be reduced with increased threshold value a for some other locations, the predicted extreme wave height value oscillates when the threshold value is changed from 0.75 to 4.5 m.

It is found that the difference between the maximum and minimum predicted 100-year return period significant wave height value is about 1.8 m for some locations in the Arabian Gulf and for a few other locations, the difference is as small as 0.14 m.

It is, however, to be noted that the 100-year event is predicted based on a 12-year data set, which is uncertain.

This work needs to be repeated with longer period data, when it is available in the future.

A large number of marine projects are in progress and many new projects are planned for the near future in the Arabian Gulf.

The results of the present study will be highly useful for the optimal design of these marine structures.