Groynes reduce the amount of longshore drift, and help sand to build up in front of the cliff. Ocean groynes commonly run perpendicular to the shore, extending from the upper foreshore or beach into the water. Groynes can be made of wood, concrete, or rock piles, and placed in groups and they are often used in combination with seawalls. All of a groyne may be under water, in which case it is called a submerged groyne. The areas between groups of groynes are groyne fields.
Revetments and boulders stop strong waves hitting the base of the soft cliffs. This reduces the amount of sand, clay and gravel which is eroded. Revetments can be constructed from wood, they can be found in the form of wooden piles, loose-piled boulders or concrete shapes, or more solid banks. Commonly they are sloping structures placed on banks or cliffs in such a way as to absorb the energy of incoming water. Coastal revetments are usually built to preserve the existing uses of the shoreline and to protect the dunes or cliffs behind it from erosion.
Groynes and revetments do not protect the cliff from water which comes from the land, particularly after heavy storms. The water which collects in the clays in the cliff frequently makes them wet and unstable, which makes them collapse. Drainage pipes help drain the water out of the cliff face. This reduces the risk of the cliff collapsing when it is too wet and saturated.
A sea wall acts as a layer between the vulnerable coastline and the ocean. Wave action can beat at the sea wall without eroding the coast, although the sea wall itself will eventually break down and require repair or replacement. Sea walls also help to insulate communities from flooding, although high waves can still breach most sea walls. Sea walls are commonly constructed from reinforced concrete. In some instances several lower barriers may precede the sea wall, to help break up the wave energy before the waves hit the wall. Some sea walls are built in the water right next to a shoreline.
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