Multiple-pit breakwaters

Linearized shallow-water wave theory is used to investigate the interaction of surface waves with multiple rectangular submarine pits in water of otherwise uniform depth. The solution is obtained by a boundary element technique using a two-dimensional Green's function. It is shown that appropriate selection of pit dimensions and placement may lead to a significant reduction in wave heights behind these structures. Numerical results have been presented that illustrate the influence of the various pit characteristics on the diffracted wave field. Two pits can provide a shadow region in which wave heights are reduced to 10-20% of the incident wave height. The shadow region, with wave heights reduced to 30% of the incident wave height, is approximately the width of the pits and five wavelengths long. Guidance is given on how to select pit geometries and placement for optimal breakwater performance. An example is also presented that shows how to select a pit to reduce wave heights in a navigation channel.