WAVE DAMPING IN HARBORS

Abstract

The purpose of harbors is to give the maximum shelter to vessels to prevent damage or allow greatest ease in loading or unloading. Small craft are most effected by short period waves, while commercial craft are more effected by long period waves or surge. Small craft require that the wave action be reduced to about 1 foot or less in height to prevent damage at moorings. To obtain quietness within the harbor, it is essential to prevent energy from entering the harbor, or, by absorbing it, after it enters. Energy can enter through three sources: through the entrance, by overtopping, or by transmission through the structures. The entrance to the harbor should be made as small as possible to reduce the amount of energy entering yet it must be wide enough to provide navigation ease and safety. The optimum width of the entrance depends on the type of harbor, the amount of traffic, size of the vessels, and entrance conditions. Assuming the layout of the harbor structures as being fixed, several methods may be used to obtain maximum quietness. Porous breakwaters may be sealed. If a narrow channel is feasible, flat channel side-slopes protected by a rubble cover layer will dissipate a large portion of the energy. Wave energy reaching the interior may be absorbed by suitably placed stone wave absorbers or dissipators. Discussion of some recent pertinent studies follows.