A comparison of extreme value estimation methods for the forces in aquaculture net cages

Aquaculture structures are being installed in progressively exposed locations, and reliable estimation of extreme net forces with return periods from 50–10000 years becomes increasingly important. As state-of-the-art methods are complex and computationally time-consuming, a simplified, but efficient method for the calculation of net forces is used. This method is verified against simulations with the SIMA software, which include a state-of-the-art load model. The simplified method, developed for regular waves, is further extended to irregular seas in the present study. Extreme forces in the ropes that support the net and transfer the net forces to the steel structure are estimated using a variety of methods ranging from long-term stochastic methods to the simpler design wave method, which is currently the industry standard. The accuracy of the design wave method is evaluated against the more advanced methods. The study showed that the computation time of the simplified method is approximately 1:30 of the advanced method. • A simplified method estimating the forces in the ropes supporting the aquaculture net under the action of wave and current is generalised to allow for irregular waves. • Comparison of extreme value estimation methods for aquaculture net force. • Long term stochastic analysis, Peak over threshold, block maxima and all sea state method.