beach

 

a gently sloping zone where deposits of unconsolidated sediments are subject to wave action at the shore of an ocean or lake. Most of the sediment making up a beach is supplied by rivers or by the erosion of highlands adjacent to the coast. Beaches extend from a low waterline landward to a definite change in material or physiographic form, such as the presence of a cliff or dune complex marking a clear demarcation of the edge of a coast. The surf zone is the area between the landward limit of the waves and where the farthest seaward wave breaks. The foreshore, the active portion of the beach, is a seaward-sloping surface extending from the low tide limit of the beach to the crest of a ridge, called the berm, formed by storm waves. Water motion landward and seaward across the foreshore is called swash and backwash, respectively. The foreshore's slope angle is related to the size of the beach material and the vigor of the waves. The backshore extends landward from the berm as a broad terrace or gently landward-sloping surface, often broken by one or more beach ridges. Seaward of the surf zone is the offshore zone, which commonly contains a trough and an offshore bar where the waves begin to break before reforming and dispensing their energy on the beach. Beaches undergo a cyclical migration of sand between the beach and the offshore zone caused by seasonal changes in the supply of sedimentary material and by the changes in intensity and direction of the approaching waves. The action of tides causes daily cycles of cut and fill. Waves approaching the shore obliquely move the sediment along the beach in a zigzag pattern called longshore transport. Along low sandy coasts, such as the Eastern coast of the United States, a long, narrow beach, called a barrier beach, is commonly separated from the coast by a narrow lagoon. Where a beach extends from land and terminates in open water it is called a spit or a hook. Since beaches are mobile deposits, they owe their existence to a constant replenishment of sand. In many coastal areas a deficiency in the supply of sand from human intervention or the natural changes in the coastal environment results in serious erosion problems. Artificial replenishment by pumping sand onto the beach from offshore or halting the moving sand from longshore drift by building breakwaters are two solutions to erosional problems.

Bibliography

See W. Bascom, Waves and Beaches: The Dynamics of the Ocean Surface, (1980).

Ninety Mile Beach Australia.

Lanikai Beach on Oahu. This gently-sloping beach face is topped by a beach crest onto which a salt-tolerant grass (Sporobolus virginicus) is spreading from the incipient dune.

Gay Head Cliffs in Martha's Vineyard

South Beach at Katama, Edgartown, MA. This is an open ocean beach with waves that range from docile to large and dangerous. Spectacular beach, but children must be watched closely because of wave action. Click on photo to enlarge.

Rocky beach

The rocky beach of Newport, Rhode Island.

Looking south along New Smyrna Beach in Florida.

A beach, or strand, is a geological landform consisting of loose rock particles - such as sand, gravel, shingle, pebbles, cobble - or even shell fragments, along the shoreline of a body of water. Beaches occur along coastal areas, where wave or current action deposits and reworks sediments, or at the margin of land along a lake or river subject to erosion caused by rainfall.

Components

Some geologists consider a beach to be merely a shoreline feature of deposited material, but William Bascom (1980) has argued that a beach is the entire system of sand set in motion by waves to a depth of ten meters (30+ feet) or more off ocean coasts. Submerged, longshore bars are therefore also part of the beach, and thus beaches can be viewed as either:

• small systems in which the rock material moves onshore, offshore, or alongshore by the forces of waves and currents; or
• geological units of considerable size.

The former are described in detail below; the larger geological units are discussed elsewhere under bars.

There are several conspicuous parts to a beach, all of which relate to the processes that form and shape it. The part mostly above water (depending upon tide), and more or less actively influenced by the waves at some point in the tide, is termed the beach berm. The berm is the deposit of material comprising the active shoreline. The berm has a crest (top) and a face — the latter being the slope leading down towards the water from the crest. At the very bottom of the face, there may be a trough, and further seaward one or more longshore bars: slightly raised, underwater embankments formed where the waves first start to break.

The sand deposit may extend well inland from the berm crest, where there may be evidence of one or more older crests (the storm beach) resulting from very large storm waves and beyond the influence of the normal waves. At some point the influence of the waves (even storm waves) on the material comprising the beach stops, and if the particles are small enough (sand size or smaller), winds shape the feature. Where wind is the force distributing the grains inland, the deposit behind the beach becomes a dune.

The line between beach and dune is difficult to define in the field. Over any significant period of time, sand is always being exchanged between them. The drift line (the high point of material deposited by waves) is one potential demarcation. This would be the point at which significant wind movement of sand could occur, since the normal waves do not wet the sand beyond this area. However, the drift line is likely to move inland under assault by storm waves.

Beach formation

Beaches are deposition landforms, and are the result of wave action by which waves or currents move sand or other loose sediments of which the beach is made as these particles are held in suspension. Alternatively, sand may be moved by saltation (a bouncing movement of large particles). Beach materials come from erosion of rocks offshore, as well as from headland erosion and slumping producing deposits of scree. Some of the whitest sand in the world, along Florida's Emerald Coast, comes from the erosion of quartz in the Appalachian Mountains. A coral reef offshore is a significant source of sand particles.

The shape of a beach depends on whether or not the waves are constructive or destructive, and whether the material is sand or shingle. Constructive waves move material up the beach while destructive waves move the material down the beach. On sandy beaches, the backwash of the waves removes material forming a gently sloping beach. On shingle beaches the swash is dissipated because the large particle size allows percolation, so the backwash is not very powerful, and the beach remains steep. Cusps and horns form where incoming waves divide, depositing sand as horns and scouring out sand to form cusps. This forms the uneven face on some sand shorelines.

There are several beaches which are claimed to be the "World's longest", including Cox's Bazar, Bangladesh (120kms), Fraser Island beach, 90 Mile Beach in Australia and 90 Mile Beach in New Zealand and Long Beach, Washington (which is about 30km). Wasaga Beach, Ontario on Georgian Bay claims to have the world's longest freshwater beach. But the longest beach in the world is in fact Praia do Cassino, a 240km long beach located in southern Brazil, near the border with Uruguay.

Beaches and recreation

In the Victorian era, many popular beach resorts were equipped with bathing machines because even the all-covering beachwear of the period was considered immodest. This social standard still prevails in many Muslim countries. At the other end of the spectrum are clothing-optional beaches, where swimwear and other forms of clothing are optional.

A walk along the beach is also popular, including a long walk in the case of a long beach, for example from one seaside resort to the next. It is customary for people to walk barefoot to the beach, because of the pleasant feeling of sand on their soles and between their toes. The best beach walking areas typically are near the shoreline, where the sand is wet and more comfortable to walk in. A person will also enjoy walking with their bare feet in the water.

In more than thirty countries in Europe, South Africa, New Zealand, Canada, South America and the Caribbean, the best recreational beaches are awarded Blue Flag status, based on such criteria as water quality and safety provision. Subsequent loss of this status can have a severe effect on tourism revenues.

Due to intense use by the expanding human population, beaches are often dumping grounds for waste and litter, necessitating the use of beach cleaners and other cleanup projects. More significantly, many beaches are a discharge zone for untreated sewage in most underdeveloped countries; even in developed countries beach closure is an occasional circumstance due to sanitary sewer overflow. In these cases of marine discharge, waterborne disease from fecal pathogens and contamination of certain marine species is a frequent outcome.

Artificial beaches

Some beaches are artificial; they are either permanent or temporary (For examples see Monaco, Paris, Rotterdam,Toronto, Hong Kong and Singapore).

The soothing qualities of a beach and the pleasant environment offered to the beachgoer are replicated in artificial beaches, such as "beach style" pools with zero-depth entry and wave pools that recreate the natural waves pounding upon a beach. In a zero-depth entry pool, the bottom surface slopes gradually from above water down to depth. Another approach involves so-called urban beaches, a form of public park becoming common in large cities. Urban beaches attempt to mimic natural beaches with fountains that imitate surf and mask city noises, and in some cases can be used as a play park.

Beach nourishment involves pumping sand onto beaches to improve their health. Beach nourishment is common for major beach cities around the world; however the beaches that have been nourished can still appear quite natural and often many visitors are unaware of the works undertaken to support the health of the beach. Such beaches are often not recognised as artificial. Crabs are also often used to keep beaches free from trees.

A concept of IENCE has been devised to describe investment into the capacity of natural environments. IENCE is Investment to Enhance the Natural Capacity of the Environment and includes things like beach nourishment of natural beaches to enhance recreational enjoyment and snow machines that extend ski seasons for areas with an existing snow economy developed upon a natural snowy mountain. As the name implies IENCE is not quite mainstream natural science as its goal is to artificially invest into an environment's capacity to support anthropogenic economic activity. An artificial reef designed to enhance wave quality for surfing is another example of IENCE. The Surfrider Foundation has debated the merits of artificial reefs with members torn between their desire to support natural coastal environments and opportunities to enhance the quality of surfing waves. Similar debates surround Beach nourishment and Snow cannon in sensitive environments.

Beaches as habitat

A beach is an unstable environment which exposes plants and animals to changeable and potentially harsh conditions. Some small animals burrow into the sand and feed on material deposited by the waves. Crabs, insects and shorebirds feed on these beach dwellers. The endangered Piping Plover and some tern species rely on beaches for nesting. Sea turtles also lay their eggs on ocean beaches. Seagrasses and other beach plants grow on undisturbed areas of the beach and dunes.

Ocean beaches are habitats with organisms adapted to salt spray, tidal overwash, and shifting sands. Some of these organisms are found only on beaches. Examples of these beach organisms in the southeast US include plants like sea oats, sea rocket, beach elder, beach morning glory, and beach peanut, and animals such as mole crabs, coquina clams, ghost crabs, and white beach tiger beetles.^[1]

Notable Beaches

• Bondi Beach - Sydney, New South Wales, Australia
• Miami Beach - Miami, Florida, USA
• West Palm Beach - West Palm Beach, Florida, USA
• Daytona Beach - Daytona, Florida, USA
• Virginia Beach - Virginia Beach, Virginia, USA
• Long Beach - Los Angeles, California, USA
• Redondo Beach Beach - Los Angeles, California, USA
• Copacabana Beach - Rio de Janeiro, Brazil
• Waikiki Beach - Honolulu, Hawaii, USA

Gallery

A surfer carries a surfboard along the beach.

Recreation on a California beach, first decade of the 20th century.

Early morning view of Keansburg Beach in New Jersey.

Beaches at Ocean City, Maryland.

See also

• List of beaches
• Beach cricket
• Beach volleyball
• Coast
• Dune buggy
• Nude beach
• Pier
• Shore
• Surfing
• Urban beach
• Beach evolution

References

Source

• Bascom, W. 1980. Waves and Beaches. Anchor Press/Doubleday, Garden City, New York. 366 p.

External links

• UNESCO Beach erosion & formation
• Beach habitats
• Sea Foam: What Is It? -- Beaufort County Librarynrm:Grève

Donate to Wikimedia