A Simplified Approach to Estimate the Probability of Otter Board Hooking at Pipelines

Hooking events, defined as trawling gear becoming firmly “stuck” under a pipeline, rarely occur during bottom-trawling operations. However, hooking events can have detrimental consequences. There is no existing method for quantifying the hooking probability of bottom-trawling operations. In this study, an approach is proposed to quantify the trawl board hooking probability using simulation tools and statistical data. Numerical simulation use the SIMLA code to establish simplified hooking criteria. The criteria link the pipeline data to the fishing activities data, enabling the quantification of hooking probability. First, the numerical simulations of both pull-over and hooking events were compared with small-scale model test results. Reasonable agreement was reached. Based on the simulation results, simplified criteria for trawl board hooking were proposed. Finally, data from the EUROPIPE II pipeline section in the Norwegian sector were used as a case study. Data regarding free span as well as fishing activities in that region were used to obtain the statistical input. The Monte Carlo simulation technique was then used to estimate the hooking probability. Parametric studies were first performed to investigate the effects of important parameters. Then, based on the findings from the parametric studies, the hooking probability with the most reasonable parameters was estimated.