Impact of anchor type distribution on anchor hazard assessment

In various cable routing and burial depth designs use has been made of a series of offshore anchor dragging tests in sandy seabeds in the German Bight that TenneT executed in 2013. The test results were made available in the public domain, but the application of the results was not optimal due to the lack of information about the distribution of types of anchors over different vessel sizes and types. The paper presents the results of an inventory of more than 500 randomly selected ships in the North Sea, Suez Canal and Singapore areas, giving helpful guidance on what type of anchors can be expected. Using this, some of the conservative assumptions in the application of the TenneT test results can be changed to 'best estimate' assumptions, leading to more realistic boundary conditions for a risk-based cable burial design. The effect on the anticipated anchor risk is illustrated in this paper.