Flat coast
A coastal landform of loose material with shoreface and beach.
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A flat coast, or flat shoreline, is a coastal landform characterized by a gradual descent of the land into the sea. These coasts are composed entirely of loose material, predominantly sand and gravel. Their formation occurs through two primary processes: the sea advancing into terrain that already has a gentle slope, or the continuous abrasion and wearing down of loose rock by wave action. Structurally, a flat coast is fundamentally divided into two parallel zones: the shoreface, which is the underwater platform constantly affected by moving water, and the beach, the landward area that is only periodically flooded.
Sandbars, runnels and creeks
The typical sequence of landforms created by the sea along such a coast is known as a "littoral series." This series begins in the permanently submerged shoreface with a sand or gravel reef, called a longshore bar, which runs parallel to the shore. The basin between this bar and the shore is termed a runnel or swale. Multiple parallel bars and runnels may exist. The beach itself often features a bank of sand or gravel known as a berm, formed when breaking waves deposit coarse material beyond the average sea level, where the backwash cannot remove it.
The location and size of berms change seasonally; winter storm surges create higher, more prominent berms than those formed by summer tides. Beaches are heavily eroded during storm surges, which steepen the profile, while normal wave action tends to raise the beach. A series of parallel berms can cause the shoreline to advance seaward over time.
Beach losses and gains
The landward limit of storm surge influence is marked by a belt of dunes, where floods may carve a dune cliff. Wind transports finer sand grains inland over these dunes, and the sea continually washes pebbles and sand away from one location, depositing it elsewhere. Coastal defences against erosion include groynes, stone walls, and concrete tetrapods that act as breakwaters. The first plants to colonize the dunes, such as sea buckthorn or beach grass, help prevent wind erosion.
Quick Facts
- Type
- Coastal landform
- Composition
- Sand and gravel
- Subdivisions
- Shoreface and beach
- Key features
- Sandbars
- runnels
- berms
- dunes
Facts from the source article.
Lore & Background
Flat coasts consist of loose material such as sand and gravel. Wind transports finer grains of sand inland over the dunes, while the sea washes pebbles and sand away from the coast and deposits them elsewhere.
The typical sequence of landforms created by the sea is described as a 'littoral series', which starts in the permanently flooded shallow water region (shoreface) with a sand or gravel reef called a bar. The longshore bar is an elongated ridge of sand parallel to the shore in the surf zone, and the basin between a sandbar and the shore zone is called a runnel or swale. There may be several bars separated by parallel runnels or creeks.
Reader's Guide
The shoreface on flat coasts encompasses the area subject to constant moving water, with its landward boundary at the average low-water mark, though definitions vary among authors. Some define the beach as extending from low-water mark to highest high-water mark, while others use terms like intertidal zone (foreshore) and supratidal zone (backshore). The backshore, often flatter than the foreshore, is frequently called a beach platform and considered the actual beach. On the beach, a bank of sand or gravel ridge called a berm often forms parallel to the shoreline, created by material thrown beyond the average sea level by breaking waves.
Berms are subject to seasonal changes, with winter berms typically more prominent. Beaches are heavily eroded during storm surges but raised by normal wave action, and a series of parallel berms can cause the shoreline to advance seawards over time. Coastal defenses against erosion include groynes, stone walls, or tetrapods of concrete acting as breakwaters.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Flat coast (CC BY-SA 4.0).
- Word definitions: the Codexery glossary, each quoted from its Wikipedia article.
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