Plaža

Šljunčana plaža u Kuparima

Recreational beaches, such as this one on the Gold Coast of Australia, can be shaped and maintained by beach nourishment projects.

Plaža je deo morske ili slatkovodne obale uređen za kupanje ljudi. The particles composing a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources, such as mollusc shells or coralline algae. Sediments settle in different densities and structures, depending on the local wave action and weather, creating different textures, colors and gradients or layers of material.

Though some beaches form on freshwater locations, most beaches are in coastal areas where wave or current action deposits and reworks sediments. Erosion and changing of beach geologies happens through natural processes, like wave action and extreme weather events. Where wind conditions are correct, beaches can be backed by coastal dunes which offer protection and regeneration for the beach. However, these natural forces have become more extreme due to climate change, permanently altering beaches at very rapid rates. Some estimates describe as much as 50 percent of the earth's sandy beaches disappearing by 2100 due to climate-change driven sea level rise.

Sandy beaches occupy about one third of global coastlines. These beaches are popular for recreation, playing important economic and cultural roles—often driving local tourism industries. To support these uses, some beaches have man-made infrastructure, such as lifeguard posts, changing rooms, showers, shacks and bars. They may also have hospitality venues (such as resorts, camps, hotels, and restaurants) nearby or housing, both for permanent and seasonal residents.

Human forces have significantly changed beaches globally: direct impacts include bad construction practices on dunes and coastlines, while indirect human impacts include water pollution, plastic pollution and coastal erosion from sea level rise and climate change. Some coastal management practices are designed to preserve or restore natural beach processes, while some beaches are actively restored through practices like beach nourishment.

Marine debris on a beach in Hawaii.

Wild beaches, also known as undeveloped or undiscovered beaches, are not developed for tourism or recreation. Preserved beaches are important biomes with important roles in aquatic or marine biodiversity, such as for breeding grounds for sea turtles or nesting areas for seabirds or penguins. Preserved beaches and their associated dune are important for protection from extreme weather for inland ecosystems and human infrastructure.

Lokacija i profil

Beach zones

A berm is a nearly horizontal portion that stays dry except during extremely high tides and storms. The swash zone is alternately covered and exposed by wave run-up. The beach face is the sloping section below the berm that is exposed to the swash of the waves. The wrack line (not shown here) is the highest reach of the daily tide where organic and inorganic debris is deposited by wave action. May have sand dunes.

Although the seashore is most commonly associated with the word beach, beaches are also found by lakes and alongside large rivers.

Beach may refer to:

• small systems where 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 that 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 long shore 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.

Summer versus winter beach

The differences between summer and winter on beaches in areas where the winter conditions are rougher and waves have a shorter wavelength but higher energy. In winter, sand from the beach is stored offshore.

These geomorphic features compose what is called the beach profile. The beach profile changes seasonally due to the change in wave energy experienced during summer and winter months. In temperate areas where summer is characterised by calmer seas and longer periods between breaking wave crests, the beach profile is higher in summer. The gentle wave action during this season tends to transport sediment up the beach towards the berm where it is deposited and remains while the water recedes. Onshore winds carry it further inland forming and enhancing dunes.

Conversely, the beach profile is lower in the storm season (winter in temperate areas) due to the increased wave energy, and the shorter periods between breaking wave crests. Higher energy waves breaking in quick succession tend to mobilise sediment from the shallows, keeping it in suspension where it is prone to be carried along the beach by longshore currents, or carried out to sea to form longshore bars, especially if the longshore current meets an outflow from a river or flooding stream. The removal of sediment from the beach berm and dune thus decreases the beach profile.

If storms coincide with unusually high tides, or with a freak wave event such as a tidal surge or tsunami which causes significant coastal flooding, substantial quantities of material may be eroded from the coastal plain or dunes behind the berm by receding water. This flow may alter the shape of the coastline, enlarge the mouths of rivers and create new deltas at the mouths of streams that had not been powerful enough to overcome longshore movement of sediment.

The line between beach and dune is difficult to define in the field. Over any significant period of time, sediment 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.

Vrste plaža

Plaža Veliki žal kod Dubrovnika

Peščana plaža

Plaža može biti potpuno prirodna, ali i veštački izgrađena površina obale, prilagođena što lakšem pristupu vodenim površinama u svrhu kupanja i osveženja ljudi tokom letnjih meseci.

Prema sastavu tla, plaže mogu biti peščane, šljunčane ili betonske.

Peščana plaža

Peščana plaža je plaža čije su površine obale i morsko dno od peska. Takve plaže obično imaju dugačke plićake i najpogodnije su za porodicu sa malom decom. Boja peska varira od svetlo sive koja je uobičajena u Crnoj Gori do zlatne boje i narandžaste na obalama npr. Jadranskog mora i Sredozemnog mora do bele boje peska koja je karakteristična za toplije i tropske krajeve. Bela boja peska je zastupljena na egzotičnim krajevima, destinacijama kao što su Kuba, Maldivi, Tajland, Bali i ostrva Indonezije, Bora Bora, Mauricijus, Portoriko i druga ostrva u Atlantskom okeanu, Indijskom okeanu i u Polineziji, u Tihom okeanu. Od boje peska i dna kao i vremena, zavisi i boja mora. Najređe boje peska su ružičasta boja i zelena boja. Roza boja peska je posledica prisustva rozenkvarca kamena koji daje svetlo roze boju. Kvarc može dati i pesku i crvenu boju ali veoma retko, dok zelena boja peska je i posledica prisustva zelenih morskih algi, kao i sitnih čestica kamena zelene boje. Pesak je estetski „lepši” od kamena i šljunka i udobniji za hodanje po plaži jer je potpuno mekan i gladak, ali mane peska su što leti kada vetar duva, upada u oči i kosu i lepi se na stopala i noge, i upadaju čestice peska u odeću i u kupaće kostime.

Šljunčana plaža

Plaža čije je tlo sastavljeno od sitnog kamenja, izlokanog vekovnim abrazivnim delovanjima vode, naziva se šljunčana plaža. U Dalmaciji je za takva vrsta plaže se naziva žal ili žalo.

Betonska plaža

Plaža čije su površine izgrađene od betona naziva se betonska plaža. Betonske plaže obično se grade na onom delu na kojem je pristup vodenim površinama otežan zbog stenovite obale.

Sadržaji

Plaže mogu biti u potpunosti bez ikakvih sadržaja. Takve plaže obično se nalaze duž obale van naseljenih mesta i nazivaju se divlje plaže.

Ipak, većina plaža ima sadržaje poput restorana, kafe barova, sanitarnog čvora i tuševa. Moderne plaže opremljene su i sadržajima za sport i rekreaciju poput igrališta za odbojku na pesku, tobogana ili teniskih terena. Na takvim plažama obično postoji mogućnost iznajmljivanja skutera za vodu, gondola, pedalina, opreme i glisera za skijanje na vodi, daske za jedrenje, opreme za ronjenje i ostalog.

Na svakoj boljoj plaži deluje i služba za spasavanje koja je sastavljena od mladića i devojaka sa završenim kursem za spašavanje davljenika i pružanje prve pomoći.

Osim navedenih, postoje i nudističke (FKK) plaže na kojima je uobičajeno kupanje bez kupaćih kostima. Takve plaže su obično smeštene na diskretnim lokacijama te su na taj način manje izložene znatiželjnim pogledima. I nudističe plaže mogu imati potpune sadržaje ali mogu biti i bez sadržaja.

Najuređenije plaže, sa izrazito čistom vodom za kupanje te uređenom i održavanomo okolinom, nosilice su Međunarodne plave zastave, priznanja koje se dodeljuje za ekološku zaštitu okoline.

Literatura

• Bascom, W. 1980. Waves and Beaches. Anchor Press/Doubleday, Garden City, New York. 366 p.
• Schwartz, Maurice L. (1982). The Encyclopedia of Beaches and Coastal Environments: Volume 15 of Encyclopedia of earth sciences. Virginia: Hutchinson Ross Pub. Co. стр. 940. ISBN 0879332131. 
• Edmunds, J. (1978). Sea shells and other molluscs found on West African coast and estuaries. Arakan Press Ltd. Accra. 146pp.
• Gauld, D. T. and Buchanan, J. B. (1959). The principal features of the rock shore fauna in Ghana. Fasc. Oikos 1 (10): 121-132.
• Lamptey, E., Armah,A.K and Allotey, L.C. (2000). Spatial Assemblages of Tropical Intertidal Rocky Shore Communities in Ghana, West Africa. Environmental Science, Engineering and Technology.
• Yankson, K. and Akpabey, F.J. 2001. A preliminary survey of the macro-invertebrate fauna at Iture Rocky Beach, Cape Coast, Ghana. Journal of Natural Sciences, 1: 11-22.
• Yankson, K. and Kendall, M. (2001). A student's Guide to the Fauna of Seashores in West Africa. Darwin Initiative. Newcastle. 132pp.
• Hill, Howard (1980) Freedom to Roam: the struggle for access to Britain's moors and mountains. Ashbourne: Moorland ISBN 978-0-903485-77-7
• Shoard, Marion (1999) A Right to Roam. Oxford University Press ISBN 0-19-288016-0
• Nagelkerken, Ivan, ур. (2009). Ecological Connectivity among Tropical Coastal Ecosystems (на језику: енглески). Dordrecht: Springer Netherlands. ISBN 978-90-481-2405-3. doi:10.1007/978-90-481-2406-0. 
• Nagelkerken, I.; Blaber, S.J.M.; Bouillon, S.; Green, P.; Haywood, M.; Kirton, L.G.; Meynecke, J.-O.; Pawlik, J.; Penrose, H.M.; Sasekumar, A.; Somerfield, P.J. (2008). „The habitat function of mangroves for terrestrial and marine fauna: A review”. Aquatic Botany (на језику: енглески). 89 (2): 155—185. doi:10.1016/j.aquabot.2007.12.007. 
• Waltham, Nathan J.; Elliott, Michael; Lee, Shing Yip; Lovelock, Catherine; Duarte, Carlos M.; Buelow, Christina; Simenstad, Charles; Nagelkerken, Ivan; Claassens, Louw; Wen, Colin K-C; Barletta, Mario (2020). „UN Decade on Ecosystem Restoration 2021–2030—What Chance for Success in Restoring Coastal Ecosystems?”. Frontiers in Marine Science. 7: 71. ISSN 2296-7745. doi:10.3389/fmars.2020.00071 . hdl:2440/123896 . 

Spoljašnje veze

• Coping with beach erosion – UNESCO
• Najlepše plaže sveta Архивирано на сајту Wayback Machine (29. април 2007)
• Plava zastava