Types of sea defences

A seawall (or sea wall) is a form of coastal defence constructed where the sea, and associated coastal processes, impact directly upon the landforms of the coast. The purpose of a sea wall is to protect areas of human habitation, conservation and leisure activities from the action of tides, waves, or tsunamis. 

Riprap is a formation rocks or other material used to armor shorelines, streambeds, bridge abutments, pilings and other shoreline structures against scour and water or ice erosion. It is made from a variety of rock types, commonly granite or limestone, and occasionally concrete rubble from building and paving demolition. It can be used on any waterway or water containment where there is potential for water erosion. 

A groyne is an active structure extending from shore into sea, most often perpendicularly or slightly obliquely to the shoreline. Adequate supply of sediment and existence of satisfactorily intensive long shore sediment transport are the sine qua non conditions of groynes efficiency. Catching and trapping of a part of sediment moving in a surf zone (mainly in a long shore direction), as well as reduction of the sediment amount transported seawards, are the principle functions of the groyne. 

Revetmentsare always made as sloping structures and are very often constructed as permeable structures using natural stones or concrete blocks, thereby enhancing wave energy absorption and minimizing reflection and wave run-up. However, revetments can also consist of different kinds of concrete slabs, some of them permeable and interlocking. In this way their functionality is increased in terms of absorption and strength. An example of a permeable and interlocking concrete slap is the so-called Flex Slap. Net mesh stone-filled mattresses, such as gabions, are also used; however, they are only recommended for use at fairly protected locations. 

Beach nourishment is the process of dumping or pumping sand from elsewhere onto an eroding shoreline to create a new beach or to widen the existing beach. Beach nourishment does not stop erosion, it simply gives the erosional forces (usually waves) something else to "chew on" for a while.

Breakwaters are structures constructed on coasts as part of coastal defense or to protect an anchorage from the effects of both weather and longshore drift.

A gabion is a basket or container filled with earth, stones, or other material and used in civil engineering works or (formerly) fortifications.