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Extreme Waves for Different Return Periods in the Arabian Gulf – Effect of Threshold Value in the Peak over Threshold Analysis

Author(s): S. Neelamani

Linked Author(s): Neelamani Subramani

Keywords: Gumbel and Weibull distribution; Significant wave height; Hindcasted wave data; Design wave; Marine structures

Abstract: 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 Weibull extreme value distributions are used for the extreme wave analysis and the Weibull distribution is found to be better for all the locations. The value of the shape parameter of the Weibull 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 parameter 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 reduce with increased threshold value and 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 1.8m for some locations in the Arabian Gulf and for few other locations, the difference is as small as 0.14 m. It is however to be noted that100 year event is predicted based on 12 year data set, which is uncertain. This work needs to be repeated with more 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 optimal design of these marine structures.


Year: 2010

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