Editing Breakwater (structure) (section)

{{Short description|Coastal defense structure}}
{{not to be confused with|Seawall|Mole (architecture)}}
[[Image:Breakwater break1 new(USGS).jpg|thumb|upright=1.35|The [[Alamitos Bay]], [[California]], entrance channel. Breakwaters create safer harbours, but can also trap sediment moving along the coast.]]
[[File:Vågbrytare - Ystad-2019.jpg|thumb|upright=1.35|Breakwater under construction in [[Ystad]], Sweden (2019)]]
[[File:Breakwater in Haukilahti.jpg|thumb|upright=1.35|A breakwater in [[Haukilahti]], [[Espoo]], [[Finland]]]]

A '''breakwater''' is a permanent structure constructed at a coastal area to protect against tides, currents, waves, and storm surges.  Breakwaters have been built since antiquity  to protect [[anchorage (maritime)|anchorages]], helping isolate vessels from marine hazards such as wind-driven waves.<ref>A. de Graauw (2022) “Ancient Port Structures, Parallels between the ancient and the modern” [https://www.academia.edu/38518614]</ref> A breakwater, also known in some contexts as a [[jetty]] or a [[Mole_(architecture)|mole]], may be connected to land or freestanding, and may contain a walkway or road for vehicle access.

Part of a [[coastal management]] system, breakwaters are installed parallel to the shore to minimize [[erosion]]. On beaches where [[longshore drift]] threatens the erosion of beach material, smaller structures on the beach  may be installed, usually perpendicular to the water's edge. Their action on waves and current is intended to slow the longshore drift and discourage mobilisation of beach material. In this usage they are more usually referred to as [[groyne]]s.