Editing Breakwater (structure) (section)

==Types ==
Types of breakwaters include vertical wall breakwater, mound breakwater and mound with superstructure or composite breakwater.

A breakwater structure is designed to absorb the energy of the waves that hit it, either by using mass (e.g. with caissons), or by using a [[revetment]] slope (e.g. with rock or concrete armour units).

In [[coastal engineering]], a revetment is a land-backed structure whilst a breakwater is a sea-backed structure (i.e. water on both sides).

=== Rubble ===
Rubble mound breakwaters use structural voids to dissipate the wave energy. Rubble mound breakwaters consist of piles of stones more or less sorted according to their unit weight: smaller stones for the core and larger stones as an armour layer protecting the core from wave attack. Rock or concrete armour units on the outside of the structure absorb most of the energy, while gravels or sands prevent the wave energy's continuing through the breakwater core. The slopes of the revetment are typically between 1:1 and 1:2, depending upon the materials used. In shallow water, revetment breakwaters are usually relatively inexpensive. As water depth increases, the material requirements—and hence costs—increase significantly.<ref>{{Cite journal|last=CIRIA, CUR, CETMEF|date=2007|title=Rock Manual – The use of rock in hydraulic engineering|url=http://rockmanual.dicea.nl|journal=Ciria-CUR}}</ref>

=== Caisson ===
[[Caisson (engineering)|Caisson]] breakwaters typically have vertical sides and are usually erected where it is desirable to [[Berth (moorings)|berth]] one or more vessels on the inner face of the breakwater. They use the mass of the caisson and the fill within it to resist the overturning forces applied by waves hitting them. They are relatively expensive to construct in shallow water, but in deeper sites they can offer a significant saving over revetment breakwaters.

An additional rubble mound is sometimes placed in front of the vertical structure in order to absorb wave energy and thus reduce wave reflection and horizontal wave pressure on the vertical wall. Such a design provides additional protection on the sea side and a quay wall on the inner side of the breakwater, but it can enhance [[wave overtopping]].

=== Wave absorbing caisson ===
A similar but more sophisticated concept is a wave-absorbing caisson, including various types of perforation in the front wall.

Such structures have been used successfully in the offshore oil-industry, but also on coastal projects requiring rather low-crested structures (e.g. on an urban promenade where the sea view is an important aspect, as seen in [[Corniche_Beirut|Beirut]] and [[Land_reclamation_in_Monaco|Monaco]]). In the latter, a project is presently ongoing at the [[Le_Portier|Anse du Portier]] including 18 wave-absorbing {{cvt|27|m}} high caissons.

=== Wave attenuator ===
Wave attenuators consist of concrete elements placed horizontally one foot under the free surface, positioned along a line parallel to the coast. Wave attenuators have four slabs facing the sea, one vertical slab, and two slabs facing the land; each slab is separated from the next by a space of {{convert|200|mm|in}}. The row of four sea-facing and two land-facing slabs reflects offshore wave by the action of the volume of water located under it which, made to oscillate under the effect of the incident wave, creates waves in phase opposition to the incident wave downstream from the slabs.{{technical inline|date=September 2021}}

=== Membrane Breakwaters ===
A submerged flexible mound breakwater can be employed for wave control in shallow water as an advanced alternative to the conventional rigid submerged designs. Further to the fact that, the construction cost of the submerged flexible mound breakwaters is less than that of the conventional submerged breakwaters, ships and marine organisms can pass them, if being deep enough. These marine structures reduce the collided wave energy and prevent the generation of standing waves.<ref>Jafarzadeh, E., Kabiri-Samani, A., Mansourzadeh, S., & Bohluly, A. (2021). Experimental modeling of the interaction between waves and submerged flexible mound breakwaters. Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment, 235(1), 127-141.</ref>