Regressive delta

A regressive delta is a body of sediment that forms at the landward end of a gut.[1]

In contrast to river deltas, regressive deltas are not caused by fluvial sedimentation but by marine sedimentation. During storm events, sediment-bearing sea water is pressed through the gut into the adjacent lagoon. Sedimentation takes place immediately after the water has passed the gut because the velocity of the current strongly decreases. The surplus water will leave the lagoon at leeward guts.

Well-known regressive deltas on the Baltic Sea coast are those of the Prerower Strom in northeast Germany and the Świna in northwest Poland.[2]

The Świna and its regressive delta
Swinoujscie Landsat.jpeg
The Świna and its regressive delta

References

  1. ^ Neues Tief bei Pillau als Seegatt
  2. ^ landschaften/prerowstrom/prerowstrom.html
Coastal geography

Coastal geography is the study of the constantly changing region between the ocean and the land, incorporating both the physical geography (i.e. coastal geomorphology, geology and oceanography) and the human geography (sociology and history) of the coast. It includes understanding coastal weathering processes, particularly wave action, sediment movement and weather, and the ways in which humans interact with the coast

Gat (landform)

A gat (German: Seegatt, Seegat or diminutive Gatje) is a strait that is constantly eroded by currents flowing back and forth, such as tidal currents. It is usually a relatively narrow but deep, up to 30 m (100 ft) passage between land masses (such as an island and a peninsula) or shallow bars in an area of mudflats. A gat is sometimes a shallower passage on lagoon coasts, including those without any tidal range.

According to Whittow a gat is either an inshore channel or strait dividing offshore islands from the mainland e.g. the Frisian Islands, or it is an opening in a line of sea cliffs allowing access to the coast from inland. It is similar, but not identical, to a gut, which is a narrow river channel or strait prior to joining an open ocean or estuary. Leser restricts its use to deep, but relatively narrow inlets in the Wadden Sea that are scoured out by currents, giving the example of the gap between the Frisian islands of Juist and Nordeney.

Island

An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island in a river or a lake island may be called an eyot or ait, and a small island off the coast may be called a holm. A grouping of geographically or geologically related islands is called an archipelago, such as the Philippines.

An island may be described as such, despite the presence of an artificial land bridge; examples are Singapore and its causeway, and the various Dutch delta islands, such as IJsselmonde. Some places may even retain "island" in their names for historical reasons after being connected to a larger landmass by a land bridge or landfill, such as Coney Island and Coronado Island, though these are, strictly speaking, tied islands. Conversely, when a piece of land is separated from the mainland by a man-made canal, for example the Peloponnese by the Corinth Canal or Marble Hill in northern Manhattan during the time between the building of the United States Ship Canal and the filling-in of the Harlem River which surrounded the area, it is generally not considered an island.

There are two main types of islands in the sea: continental and oceanic. There are also artificial islands.

Mudflat

Mudflats or mud flats, also known as tidal flats, are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers. A recent global analysis suggested they are as extensive globally as mangroves. They are found in sheltered areas such as bays, bayous, lagoons, and estuaries. Mudflats may be viewed geologically as exposed layers of bay mud, resulting from deposition of estuarine silts, clays and marine animal detritus. Most of the sediment within a mudflat is within the intertidal zone, and thus the flat is submerged and exposed approximately twice daily.

In the past tidal flats were considered unhealthy, economically unimportant areas and were often dredged and developed into agricultural land. Several especially shallow mudflat areas, such as the Wadden Sea, are now popular among those practising the sport of mudflat hiking.

On the Baltic Sea coast of Germany in places, mudflats are exposed not by tidal action, but by wind-action driving water away from the shallows into the sea. These wind-affected mudflats are called windwatts in German.

Prerower Strom

The Prerower Strom, Prerow Strom or Prerowstrom is an arm of the Baltic Sea in northeast Germany. It begins near the island of Schmidtbülten in the Bodstedter Bodden and winds its way through the countryside of the peninsula of Fischland-Darß-Zingst, where it separates Darß from the peninsula of Zingst. It ends at the harbour of the village of Prerow that gives it its name. The Prerower Strom is part of the Western Pomerania Lagoon Area National Park.

River delta

A river delta is a landform created by deposition of sediment that is carried by a river as the flow leaves its mouth and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more rarely) another river that cannot carry away the supplied sediment. The size and shape of a delta is controlled by the balance between watershed processes that supply sediment, and receiving basin processes that redistribute, sequester, and export that sediment. The size, geometry, and location of the receiving basin also plays an important role in delta evolution. River deltas are important in human civilization, as they are major agricultural production centers and population centers. They can provide coastline defense and can impact drinking water supply. They are also ecologically important, with different species' assemblages depending on their landscape position.

Surf zone

As ocean surface waves come closer to shore they break, forming the foamy, bubbly surface called surf. The region of breaking waves defines the surf zone. After breaking in the surf zone, the waves (now reduced in height) continue to move in, and they run up onto the sloping front of the beach, forming an uprush of water called swash. The water then runs back again as backswash. The nearshore zone where wave water comes onto the beach is the surf zone. The water in the surf zone, or breaker zone, is shallow, usually between 5 and 10 m (16 and 33 ft) deep; this causes the waves to be unstable.

Świna

The Świna (German: Swine; Pomeranian: Swina) is a river in northwest Poland, between 2 to 4 km from the German border. It flows from Szczecin Lagoon to the Baltic Sea between the islands of Uznam and Wolin. It is a part of the Oder estuary, and carries about 75% of that river's waterflow (of the remainder, Peenestrom carries 15% and Dziwna 10%). It has a length of about 16 km. Świnoujście is a major town on the river.

The German Empire dammed and deepened the river from 1874-1880 to create the Kaiserfahrt (Piast canal). It connects the northern part of the Świna directly with the Szczecin Lagoon and the Pomeranian harbor of Szczecin (Stettin). The river thus gained importance as a direct waterway to the industrial city. The territory along the river's path was transferred from Germany to Poland following World War II.

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