At a flat coast or flat shoreline, the land descends gradually into the

sea The sea, connected as the world ocean or simply the ocean, is the body of salty water that covers approximately 71% of the Earth's surface. The word sea is also used to denote second-order sections of the sea, such as the Mediterranean Sea, ...

. Flat coasts can be formed either as a result of the sea advancing into gently-sloping terrain or through the abrasion of loose rock. They may be basically divided into two parallel strips: the shoreface and the

beach A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources, such as mollusc s ...

. Flat coasts consist of loose material such as

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class ...

and

gravel Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone. Gravel is classifi ...

Wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ...

transports finer grains of sand inland over the

dune A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, f ...

s. The sea washes

pebble A pebble is a clast of rock with a particle size of based on the Udden-Wentworth scale of sedimentology. Pebbles are generally considered larger than granules ( in diameter) and smaller than cobbles ( in diameter). A rock made predomina ...

s and sand away from the

coast The coast, also known as the coastline or seashore, is defined as the area where land meets the ocean, or as a line that forms the boundary between the land and the coastline. The Earth has around of coastline. Coasts are important zones in n ...

and dumps it at other locations.

Flat coast littoral series

The typical sequence of landforms created by the sea is described as a "littoral series".

Sandbars, runnels and creeks

The littoral series of a flat coast starts in the permanently flooded shallow water region, or shoreface, with a sand or gravel

reef A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes—deposition of sand, wave erosion planing down rock ...

(also called a

bar Bar or BAR may refer to: Food and drink * Bar (establishment), selling alcoholic beverages * Candy bar * Chocolate bar Science and technology * Bar (river morphology), a deposit of sediment * Bar (tropical cyclone), a layer of cloud * Bar ( ...

). The longshore bar is an elongated ridge of sand found parallel to the shore in the surf zone on many flat coasts. It consists mainly of sand or gravel, depending on the material available along the coast. The sides of the sandbar fall gently away. The basin between a sandbar and the shore zone is called the runnel or swale. The presence of a bar clearly indicates that the movement of waves is transporting and depositing material on the seabed. There may be several bars whose longitudinal axes all run parallel to the beach and which are separated by equally parallel runnels or creeks. The drainage troughs in areas of

tidal flats Mudflats or mud flats, also known as tidal flats or, in Ireland, slob or slobs, are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers. A global analysis published in 2019 suggested that tidal f ...

also run parallel to the coast.

Shoreface and beach

The shoreface (or underwater platform) on flat coasts encompasses in its narrow sense that area which is subject to the constant action of moving water. This means that the landward boundary between shoreface and beach is the line of the average low-water mark. However this definition is not universal and frequently varies from author to author in the literature. Whilst some define the beach as the landward transition to the shoreface that extends from the low-water mark to the highest high-water mark, i.e. the zone that is only periodically or episodically (after a

storm surge A storm surge, storm flood, tidal surge, or storm tide is a coastal flood or tsunami-like phenomenon of rising water commonly associated with low-pressure weather systems, such as cyclones. It is measured as the rise in water level above the ...

) flooded by water; other authors do not use the term "beach" for the landward element of a flat coast at all. They describe the region between the mean low-water mark and the mean high-water mark of the

tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables ...

s as the

intertidal zone The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species ...

foreshore The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various specie ...

and that area above the average high-water mark as the supratidal zone or backshore that is only directly attacked by water during storms. Because the backshore is often considerably flatter in appearance than the foreshore, which slopes clearly down towards the sea, it is also often referred to as a beach platform, which is why this part of the shore can be considered in practice to be the actual beach. The farthest point inland that is reached by storm surges is bounded by a belt of dunes, where floods can form a dune cliff.

Berm

On the beach (the beach platform) there is very often a bank of sand or a gravel ridge parallel to the shoreline and a few tens of centimetres high, known as the

berm A berm is a level space, shelf, or raised barrier (usually made of compacted soil) separating areas in a vertical way, especially partway up a long slope. It can serve as a terrace road, track, path, a fortification line, a border/ separation ...

. On its landward side there is often a shallow runnel. The berm is formed by material transported by the breaking waves that is thrown beyond the average level of the sea. The coarse-grained material that can no longer be washed away by the backwash remains behind. The location and size of the berm is subject to seasonal changes. For example, a winter berm that has been thrown up by storm surges in winter is usually much more prominent and higher up the beach than berms formed by summer high tides. A similar landform is a

beach ridge A beach ridge is a wave-swept or wave-deposited ridge running parallel to a shoreline. It is commonly composed of sand as well as sediment worked from underlying beach material. The movement of sediment by wave action is called ''littoral tran ...

Beach losses and gains

Beaches are usually heavily eroded during

s and the beach profile steepened, whereas normal wave action on flat coasts tends to raise the beach. Not infrequently a whole series of parallel berms is formed, one behind the other. There is a consequent gradual increase in height with the result that, over time, the shoreline advances seawards. A striking example of land-forming system of berms is Skagen Odde on the northern tip of Vendsyssel in the extreme north of

Denmark ) , song = ( en, "King Christian stood by the lofty mast") , song_type = National and royal anthem , image_map = EU-Denmark.svg , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of Denmark , establish ...

. This headland is still growing today as more berms are added.

Coastal defences Coastal management is defence against flooding and erosion, and techniques that stop erosion to claim lands. Protection against rising sea levels in the 21st century is crucial, as sea level rise accelerates due to climate change. Changes in ...

against erosion are

groyne A groyne (in the U.S. groin) is a rigid hydraulic structure built perpendicularly from an ocean shore (in coastal engineering) or a river bank, interrupting water flow and limiting the movement of sediment. It is usually made out of wood, concr ...

stone walls Stone walls are a kind of masonry construction that has been used for thousands of years. The first stone walls were constructed by farmers and primitive people by piling loose field stones into a dry stone wall. Later, mortar and plaster ...

, or

tetrapods Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct therapsi ...

of concrete, which act as breakwaters. The first plants to colonise the dunes include sea buckthorn or

beach grass ''Ammophila'' (synonymous with ''Psamma'' P. Beauv.) is a genus of flowering plants consisting of two or three very similar species of grasses. The common names for these grasses include marram grass, bent grass, and beachgrass. These grasses ar ...

which prevent wind erosion.

References

Literature

* Klaus Duphorn ''et al.'': ''Die deutsche Ostseeküste''. Sammlung geologischer Führer, Vol. 88, 281 p., numerous diagrams and maps, Bornträger, Berlin, 1995 * Heinz Klug, Horst Sterr, Dieter Boedecker: ''Die deutsche Ostseeküste zwischen Kiel und Flensburg. Morphologischer Charakter und rezente Entwicklung''. Geographische Rundschau 5, p. 6–14. Brunswick, 1988 * Harald Zepp: ''Grundriss Allgemeine Geographie – Geomorphologie''. UTB 2008, * Frank Ahnert: ''Einführung in die Geomorphologie''. UTB 2003, {{Coastal geography Geomorphology Hydrology Coastal and oceanic landforms