There are many types of material used for seawalls, In the south east region of the U.S the most popular include Concrete pre-stressed panel tongue and groove, Coral Rock, Sheet Piling (vinyl, aluminum or steel) and Riprap rock embankments. The best method or material for a given property is determined by different set of factors unique to that property.
The concrete pre-cast structures are often used in areas with a lot of water activity (strong wakes, currents heavy vessel traffic). It is a series of prefabricated concrete sections that are inserted in place and bound together with a poured in place concrete bulkhead cap to form a structurally continues resilient barrier.
The older method of coral rock structures was popular in the first half of the 20th century when canals were being dredged and the material was available for use the coral rock is a built with mortar and usually is angled towards the land mass as it does not have vertical support pillings.it has a natural look to the seawall but requires more maintenance than the concrete panel walls . It is relatively porous, so it needs to be skim coated with hydraulic concrete periodically, something that is not required with other type of seawalls.
The sheet piling structures are a series of interlocking barrier sheets made of different materials vinyl, aluminum or steel sheets set up in a row and driven into the sediment. Once sheets are secured into the berm there are a few options to anchor the top section either with a supporting frame or ledger beam or a poured-in-place concrete cap to allow structural continuity.
Riprap is actually two distinct styles that go by the same name. It can either refer to rocks being strategically piled in a way to reinforce the existing wall or act as an embankment wall. Or it can refer to bags of concrete that are laid down in a staggered pattern with steel rebar stakes that are then driven into the bags to hold them into place and anchor them into the sediment. Once the concrete cures it becomes a solid wall.
Structures are usually supported with some form of anchoring system like Tie back rods or batter piling or pin pilings. The anchors are there to keep the structure vertically plumb.