KeywordsSurf Zone Beach Ridge Integrate Coastal Zone Management Nearshore Zone Beach Face
In the most rudimentary sense, a beach may be considered a shore (q.v. coast) covered by sand (e.g., Shepard, 1973), gravel (e.g., Carter and Orford, 1984; Jennings and Shulmeister, 2002), or larger rock fragments (but lacking bare rock surfaces). More specifically, Jackson (1997) defines a beach as a relatively thick and transitory accumulation of loose waterborne materials that are mostly well-sorted sand and pebbles, but contains admixtures of mud, cobbles, boulders, smoothed rock, and shell fragments. The term was originally used in a scientific sense to designate loose waterworn shingle or pebbles on English shores (Johnson, 1919). Today, beaches are defined in a wider geomorphological sense as having subaerial and submarine components that are systematically interrelated. The beach system includes the dry (subaerial) beach, the wet beach (swash or intertidal zone), the surf zone, and the nearshore zone lying beyond the breakers (Short, 2006). Mostly the nearshore zone is defined as the area beginning from the low-water line extending seaward. The surf zone is part of the nearshore zone. The subaerial beach has a gentle seaward slope, typically with a concave profile, and extends from the low-water mark landward to a place where there is a change in material or physiography (such as a dune, bluff, or cliff, or even a seawall) or to the line of permanent vegetation marked by the limit of highest storm waves or surge. If the area beginning from the low-water line is regarded, the profile is not concave when looking to a beach with a certain tidal range. The dry beach is concave, but at low water when including the wet beach, the morphology switches from a concave beach (dry part) to a convex beach (wet part). Nearshore bars and troughs (in the subtidal domain) are often present in the surf zone, but are obscured by waves and surf, as is the always submerged nearshore zone (Short, 2006). Beach morphology refers to the shape of the beach, surf, and nearshore zone. The beach per se contains numerous morphological–processual subunits such as berms, storm ridges (e.g., Zenkovich, 1967; Pethick, 1984; Komar, 1998; Davis and FitzGerald, 2004), cusps, beach face, shoreface (e.g., Swift et al., 1985), plunge step (Davis and Fox, 1971), scarp, etc.
Related features include beach plains, beach ridges, and beachrock. Beach plains are level or gently undulating areas formed by closely spaced successive embankments of wave-deposited materials added to a prograding shoreline (Jackson, 1997). Beach ridges are low mounds of beach or beach-and-dune materials (sand, gravel, shingle) accumulated by waves on the backshore beyond the present limit of storm waves or ordinary tides. Beach ridges are roughly parallel to the shoreline and mark prior positions of an advancing shoreline (Jackson, 1997). Beachrock is a friable to well-cemented sedimentary rock formed in the intertidal zone in a tropical or subtropical region. Beachrock formations, which slope gently seaward on the beach face, consist of sand or gravel (detrital and skeletal) cemented with calcium carbonate.
Etymology and Usage
According to Merriam-Webster (1994), the first known use of the term beach was perhaps in 1535. The term beach was used to describe “loose, water-worn pebbles of the seashore,” probably from Old English bæce, bece “stream,” from Proto-Germanic *bakiz. Extended to loose, pebbly shores (1590s), and in dialect around Sussex and Kent, beach still has the meaning “pebbles worn by the waves.” French grève shows the same evolution (http://www.etymonline.com/index.php?term= beach). Thus, early on the term beach did not refer to the expanse of sand normally thought of today. Expansion of term to cover the whole shore in the late sixteenth century may have been related to a popular misunderstanding of the “pebbles” connotation of “beach” in phrases such as “walk on the beach” (http://www.word-detective.com/2007/12/strand-beach/).
Some of the longest beaches in the world include, for example, Brazil’s Praia do Cassino Beach (over 250 km long), India’s Cox’s Bazar (about 240 km long), Texas’ Padre Island (about 210 km long), Australia’s Coorong Beach (194 km), New Zealand’s Ninety Mile Beach (each about 145 km long), Mexico’s Playa Novillero (about 80 km long), and America’s Virginia Beach (about 55 km long).
Grain Size, Shape, Chemical Composition, and Color
Very fine-grained (high percentage of silt and clay) beaches may exceptionally occur under specialized conditions where there is an abundance of fine-grained sediments deposited by wave action as, for example, along the Red Sea and in the vicinity of large deltas and estuaries. A well-known example of a muddy coast with a potential for muddy “beaches” (mud flats) is provided by Anthony et al. (2010) for the 1,500-km-long coast of South America between the Amazon and the Orinoco river mouths. Ephemeral mud “beaches” also occur around mud-lump islands of the Mississippi Delta (Morgan et al. 1963). Similar “beaches” occur along the deltaic plains of the Brazos and Colorado rivers of the Texas coast and the eastern shore of Virginia (Davis, 1978).
Beaches tend to be comprised of well-sorted and generally rounded grains. Exceptions include disk, blade, and roller shapes that are so characteristic of gravel beaches where the larger clasts slide over sand and fine gravel (Pilkey et al., 2011). Biogenic beach gravels are also rather common and may comprise the entire beach sediment, as along coral reef beaches, or may be mixed with sand (cf. Figs. 1 and 2). The abundance of biogenic debris (shell, algae, coral fragments) on beaches reflects the provenance of materials and the processes acting on the beach to produce a range of irregular shapes such as the pure Acropora coral stick beaches (Davis, 1978).
Types of Beaches
Because beaches occur in all climatic zones, there are some obvious morphological differences related to severe conditions. In very high latitudes, for example, the water is frozen but for a few weeks when beaches may be affected by waves (Davis, 1978) and consequently beach morphology and texture is somewhat different from those in low latitudes. Beaches in arid climates depend almost solely on wave action to provide sediment from the bedrock coast to form a beach. The best developed beaches are associated with low-lying coasts where large quantities of sediment are available. Beach development requires an abundant sediment supply to produce characteristic morphologies and environmental zonations (Masselink et al., 2011).
The term beach type refers to the dominant nature of a beach based on tidal, wave, and current regimes, spatiotemporal extent of the nearshore zone, morphodynamics (beach width, shape, and processes) of the surf zone including bars and troughs, and the subaerial beach (Short, 1993). Irrespective of the specific beach type, most beaches contain several morphogenetic zones: (1) the backshore (nearly horizontal to gently landward-sloping area called the berm), (2) inner swash zone (upper limit of swash to the shoreline), (3) surf zone (from the shoreline to where waves break, the breaker zone), (4) nearshore zone (from the breaker zone, commonly with sandbars, to the wave base), and (5) wave base (depth where waves begin to interact with the seabed to transport sand to the beach and seaward to where sand is transported by large waves that cause beach erosion) (Davis, 1978; Short and Woodroffe, 2009). These zones are greatly variable, depending on the processes and materials that affect beach type. In addition to these major zonations of beach environments, there are numerous smaller, but important, morphological features such as the plunge step (Davis and Fox, 1971), which is a small and commonly subtle shore-parallel depression in the foreshore that is caused by the final plunge of waves as they break for the last time before surging up the beach face (Davis, 1978).
Classification of Beaches
Many factors need to be considered in the classification of beaches (e.g., Finkl, 2004) as they are among the most dynamic features on earth, but even so they retain certain overriding characteristics that facilitate generalization and categorization. The overall gradient of the beach and nearshore influences the amount of wave energy that reaches the beach, giving it its configuration. Beach materials, slope, and exposure interact with waves to produce the morphodynamic beach state that is constantly adjusting to new environmental conditions. Although beaches are one of the most dynamic morphosystems on earth (literally changing every day), they exhibit a range of characteristic morphologies that have been intensively studied in Australia. The analysis of Australian beach characteristics and shoreface dynamics (e.g., Short, 1993; Short, 1999) has led to a beach classification system that is now used internationally.
According to the classification scheme for Australian beaches (see discussion in Short and Woodroffe, 2009), there are 15 major beach types that are derived from three major beach systems: wave dominated, tide modified, and tide dominated. An overview of the beaches of Australia, which occupy half the 29,900-km-long coast (including Tasmania), is provided by Short (2006) in his discussion of the roles of waves, sediment, and tide range that contribute to beach type, particularly through the dimensionless fall velocity and relative tide range. Short’s comprehensive study of Australian beach types includes descriptions of their regional distribution, together with the occurrence of rip currents, multibar beach systems, and the influence of geological inheritance and marine biota, a natural progression of comprehensive observational collages and models stemming from seminal works (e.g., Wright and Short, 1984) commonly referred to as the “Australian Beach Model” (Short, 2006).
Recognition of the 15 beach types occurring around the Australian coast provides a basis for identifying similar wave–tide–sediment environments throughout the world and classification of many of the world’s beaches. Although applied internationally, the Australian Beach Model is not universal because it does not include tide-modified beaches exposed to higher ocean swell and storm seas, resulting in similar though higher-energy beaches, gravel, and cobble beaches (few occur in Australia), nor ice-affected beaches (because they do not occur in Australia). Nevertheless, this system finds wide application throughout the world as, for example, in the classification and study of Florida east coast beaches (e.g., Benedet et al., 2004), eastern Brazil (e.g., Klein and Menezes, 2001), India (Saravanan et al., 2011), Portugal (e.g., Coelho, Lopes, and Freitas, 2009), France (Sabatier et al., 2009), and so on.
When beaches erode along developed shorelines, they are often replenished by sand dredged from offshore and pumped back onto the shore as remediation. Efforts are made to ensure that the dredged sediment closely approximates the nature (size, shape, density, durability, composition, and color) of native beach sands onshore (e.g., Finkl and Walker, 2005). Replenished beaches are engineered to approximate natural morphodynamic beach states so that they perform as sacrificial sand deposits over desired time frames. Some artificial beaches may erode very quickly if impacted by storms and thus fall short of the design life, while others, having greater durability, may exceed the design life, as in the case of Miami Beach, Florida, which has the longest half-life of any renourished beach in America (e.g., Finkl and Walker, 2005). The practice of building artificial beaches, as a soft-engineering shore protection measure, is now so widespread worldwide that many renourished beaches are perceived as natural formations. The practice is, however, not without environmental concerns as borrow sources do not always closely match native beach sands to cause unwanted impacts in the coastal zone (e.g., Bonne, 2010).
Beaches occur in all latitudes, from tropical to polar regions, and lie on the interface between land and water to form ocean, bay (sound, estuary), and river beaches. They are mostly composed of sand (silicates and carbonates), but there is great compositional and morphological variation between sites. Beaches have great economic and environmental value, serving as tourist destinations and providing habitat as well as buffering impacts from storm waves and surges. Some beaches are artificial, and although their placement is controversial among certain special interest groups, their benefits generally outweigh disadvantages when properly engineered and placed. The morphodynamic classification of beach state finds global application, provides greater understanding of beach processes (q.v.), and contributes to beach safety education programs and surf life saving to reduce public risk.
- Benedet, L., Finkl, C. W., and Klein, A. H. F., 2004. Morphodynamic classification of beaches on the Atlantic coast of Florida: geographical variability of beach types, beach safety, and Coastal Hazards. Journal of Coastal Research (Special Issue No. 39), 360–365.Google Scholar
- Bird, E. C. F., 1984. Coasts: An Introduction to Coastal Geomorphology. Oxford: Blackwell, 320 p.Google Scholar
- Bird, E. C. F., and Schwartz, M. L. (eds.), 1985. The World’s Coastline. New York: Van Nostrand Reinhold, 1071 p.Google Scholar
- Bonne, W. M. I., 2010. European marine sand and gravel resources: evaluation and environmental impacts of extraction – an introduction. In Lancker, V. V.; Bonne, W., Uriarte, A., and Collins, M (eds.), EUMARSAND: European Marine Sand and Gravel Resources. Journal of Coastal Research, Special Issue #51, i–vi.Google Scholar
- Carter, R. W. G., and Orford, J. D., 1984. Coarse clastic barrier beaches: a discussion of the distinctive dynamic and morphosedimentary characteristics. In Greenwood, B., and Davis, R. A. (eds.), Hydrodynamics and Sedimentation in Wave-Dominated Coastal Environments. Marine Geology, 60, 377–389.Google Scholar
- COE (Corps of Engineers), (1984). Shore Protection Manual. Vicksburg, MS: Coastal Engineering Research Center, 2 Vols. Available in electronic form: http://openlibrary.org/books/OL3001149M/Shore_protection_manual; and as the Coastal Engineering Manual at http://chl.erdc.usace.army.mil/cem
- Coelho, C., Lopes, D., and Freitas, P., 2009. Morphodynamics classification of Areão Beach, Portugal. Journal of Coastal Research, (Special issue No. 56), 34–38.Google Scholar
- Davies, J. L., 1980. Geographical Variation in Coastal Development. London: Longman, 204 p.Google Scholar
- Davis, R. A., and FitzGerald, D. M., 2004. Beaches and Coasts. Malden, MA: Blackwell, 419 p.Google Scholar
- Davis, R. A., and Fox, W. T., 1971. Beach and Nearshore Dynamics in Eastern Lake Michigan. Kalamazoo, MI: Western Michigan University. Technical Report No. 4 (ONR Contract 388–092), 145 p.Google Scholar
- Dolan, R., Hayden, B., Hornberger, G., Zieman, J., and Vincent, M., (1972). Classification of the Coastal Environments of the World. Part I, The Americas. Charlottesville, VA: University of Virginia. Technical Report No. 1 (ONR Contract 389–158), 13 p.Google Scholar
- Finkl, C. W., and Walker, H. J., 2005. Beach nourishment. In Schwartz, M. (ed.), The Encyclopedia of Coastal Science. Dordrecht, The Netherlands: Kluwer Academic (now Springer), pp. 147–161.Google Scholar
- Hardisty, J., 1990. Beaches: Form and Processes. London: Unwin Hyman, 324 p.Google Scholar
- Jackson, J. A., 1997. Glossary of geology. Denver, Colorado: American Geological Institute, 769 p.Google Scholar
- Johnson, D. W., 1919. Shore processes and shoreline development. New York: Wiley, 584 p.Google Scholar
- Klein, A. H. F., and Menezes, J. T., 2001. Beach morphodynamic and profile sequence for a headland bay coast. Journal of Coastal Research, 17, 812–835.Google Scholar
- Komar, P. D., 1998. Beach Processes and Sedimentation. Upper Saddle River, NJ: Prentice Hall.Google Scholar
- Masselink, G., Hughes, M. G., and Knight, J., 2011. Introduction to Coastal Processes and Geomorphology. London: Arnold.Google Scholar
- Merriam-Webster, 1994. Merriam-Webster’s Dictionary of English Usage. Springfield, MA: Merriam-Webster, 989 p.Google Scholar
- Morgan, J. O., Coleman, J. M., and Gagliano, S. W., 1963. Mudlumps at the Mouth of South Pass, Mississippi River; Sedimentology, Paleontology, Structures, Origin and Relation to Deltaic Processes. Baton Rouge, LA: Louisiana State University Studies. Coastal Studies Series No. 10.Google Scholar
- Pethick, J., 1984. An Introduction to Coastal Geomorphology. London: Edward Arnold, 260 p.Google Scholar
- Pilkey, O. H., 2003. A Celebration of the World’s Barrier Islands. New York: Columbia University, 309 p.Google Scholar
- Pilkey, O. H., Neal, W. J., Kelley, J. T., and Cooper, A. G., 2011. The World’s Beaches. Berkeley, CA: University of California Press, 283 p.Google Scholar
- Shepard, F. P., 1973. Submarine Geology. New York: Harper and Row, 517 p.Google Scholar
- Short, A. D., 1993. Beaches of the New South Wales Coast: A Guide to the Nature, Characteristics, Surf and Safety. Sydney, NSW: Australian Beach Safety and Management Program, 358 p.Google Scholar
- Short, A. D., 1999. Handbook of Beach and Shoreface Morphodynamics. Chichester: Wiley, 379 p.Google Scholar
- Short, A. D., and Farmer, B., 2012. 101 Best Australian Beaches. Sydney, NSW: NewSouth Publishing, 222 p.Google Scholar
- Short, A. D., and Woodroffe, C. D., 2009. The Coast of Australia. Cambridge: Cambridge University Press, 288 p.Google Scholar
- van der Maarel, E. (ed.), 1993. Dry Coastal Ecosystems: Polar Regions and Europe. Amsterdam, The Netherlands: Elsevier, Ecosystems of the World, Vol. 2A, 600 p.Google Scholar
- Zenkovich, V. P., 1967. Processes of Coastal Development. Edinburgh: Oliver and Boyd, 73 p.Google Scholar