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Beach
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. They occur along coastal
areas where wave or current action deposit and rework sediments, or a
stretch of land residing along a lake or river subject to erosion caused by
rain fall.
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. 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 Muslim
countries. At the other end of the spectrum are clothing-optional beaches,
where swimwear is 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 always 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, 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]
Reference
1. ^ Blair and Dawn Witherington (2007), Florida's Living Beaches, A Guide
for the Curious Beachcomber, (Pineapple Press)
* Bascom, W. 1980. Waves and Beaches. Anchor Press/Doubleday, Garden City,
New York. 366 p.
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