A harbor ( American English ), or harbour ( Australian English , British English , Canadian English , Irish English , New Zealand English ; see spelling differences ), is a sheltered body of water where ships , boats , and barges can be moored . The term harbor is often used interchangeably with port , which is a man-made facility built for loading and unloading vessels and dropping off and picking up passengers. Harbors usually include one or more ports. Alexandria Port in Egypt, meanwhile, is an example of a port with two harbors.
41-425: Harbors may be natural or artificial. An artificial harbor can have deliberately constructed breakwaters , sea walls , or jetties or they can be constructed by dredging , which requires maintenance by further periodic dredging. An example of an artificial harbor is Long Beach Harbor , California , United States, which was an array of salt marshes and tidal flats too shallow for modern merchant ships before it
82-434: A jetty or a mole , may be connected to land or freestanding, and may contain a walkway or road for vehicle access. Part of a coastal management system, breakwaters are installed parallel to the shore to minimize erosion . On beaches where longshore drift threatens the erosion of beach material, smaller structures on the beach may be installed, usually perpendicular to the water's edge. Their action on waves and current
123-415: A function of the distance the breakwaters are built from the coast, the direction at which the wave hits the breakwater, and the angle at which the breakwater is built (relative to the coast). Of these three, the angle at which the breakwater is built is most important in the engineered formation of salients. The angle at which the breakwater is built determines the new direction of the waves (after they've hit
164-428: A habitat for mobile benthic organisms. These biotic reef types take on additional names depending upon how the reef lies in relation to the land, if any. Reef types include fringing reefs , barrier reefs , and atolls . A fringing reef is a reef that is attached to an island. Whereas, a barrier reef forms a calcareous barrier around an island, resulting in a lagoon between the shore and the reef. Conversely, an atoll
205-442: A significant saving over revetment breakwaters. An additional rubble mound is sometimes placed in front of the vertical structure in order to absorb wave energy and thus reduce wave reflection and horizontal wave pressure on the vertical wall. Such a design provides additional protection on the sea side and a quay wall on the inner side of the breakwater, but it can enhance wave overtopping . A similar but more sophisticated concept
246-668: A skeletal framework. A microbial mound might be built exclusively or primarily by cyanobacteria . Examples of biostromes formed by cyanobacteria occur in the Great Salt Lake in Utah , United States, and in Shark Bay on the coast of Western Australia . Cyanobacteria do not have skeletons, and individual organisms are microscopic. However, they can encourage the precipitation or accumulation of calcium carbonate to produce distinct sediment bodies in composition that have relief on
287-530: Is a ridge or shoal of rock, coral , or similar relatively stable material lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic (non-living) processes such as deposition of sand or wave erosion planning down rock outcrops. However, reefs such as the coral reefs of tropical waters are formed by biotic (living) processes, dominated by corals and coralline algae . Artificial reefs , such as shipwrecks and other man-made underwater structures, may occur intentionally or as
328-470: Is a ring reef with no land present. The reef front, facing the ocean, is a high energy locale. Whereas, the internal lagoon will be at a lower energy with fine grained sediments. Both mounds and reefs are considered to be varieties of organosedimentary buildups, which are sedimentary features, built by the interaction of organisms and their environment. These interactions have a synoptic relief and whose biotic composition differs from that found on and beneath
369-659: Is a wave-absorbing caisson, including various types of perforation in the front wall. Such structures have been used successfully in the offshore oil-industry, but also on coastal projects requiring rather low-crested structures (e.g. on an urban promenade where the sea view is an important aspect, as seen in Beirut and Monaco ). In the latter, a project is presently ongoing at the Anse du Portier including 18 wave-absorbing 27 m (89 ft) high caissons. Wave attenuators consist of concrete elements placed horizontally one foot under
410-518: Is designed to absorb the energy of the waves that hit it, either by using mass (e.g. with caissons), or by using a revetment slope (e.g. with rock or concrete armour units). In coastal engineering , a revetment is a land-backed structure whilst a breakwater is a sea-backed structure (i.e. water on both sides). Rubble mound breakwaters use structural voids to dissipate the wave energy. Rubble mound breakwaters consist of piles of stones more or less sorted according to their unit weight: smaller stones for
451-465: Is intended to slow the longshore drift and discourage mobilisation of beach material. In this usage they are more usually referred to as groynes . Breakwaters reduce the intensity of wave action in inshore waters and thereby provide safe harbourage. Breakwaters may also be small structures designed to protect a gently sloping beach to reduce coastal erosion ; they are placed 100–300 feet (30–90 m) offshore in relatively shallow water. An anchorage
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#1732772611273492-430: Is limited in practice by the natural fracture properties of locally available rock. Shaped concrete armour units (such as Dolos , Xbloc , Tetrapod , etc.) can be provided in up to approximately 40 tonnes (e.g. Jorf Lasfar , Morocco), before they become vulnerable to damage under self weight, wave impact and thermal cracking of the complex shapes during casting/curing. Where the very largest armour units are required for
533-823: Is only safe if ships anchored there are protected from the force of powerful waves by some large structure which they can shelter behind. Natural harbours are formed by such barriers as headlands or reefs . Artificial harbours can be created with the help of breakwaters. Mobile harbours, such as the D-Day Mulberry harbours , were floated into position and acted as breakwaters. Some natural harbours, such as those in Plymouth Sound , Portland Harbour , and Cherbourg , have been enhanced or extended by breakwaters made of rock. Types of breakwaters include vertical wall breakwater, mound breakwater and mound with superstructure or composite breakwater. A breakwater structure
574-667: Is sometimes ice-free, depending on the summertime pack ice conditions. Although the world's busiest port is a contested title, in 2017 the world's busiest harbor by cargo tonnage was the Port of Ningbo-Zhoushan . The following are large natural harbors: Breakwater (structure) A breakwater is a permanent structure constructed at a coastal area to protect against tides, currents, waves, and storm surges. Breakwaters have been built since antiquity to protect anchorages , helping isolate vessels from marine hazards such as wind-driven waves. A breakwater, also known in some contexts as
615-622: The Old Norse word rif, meaning "rib" or "reef". Rif comes from the Proto-Germanic term ribją meaning "rib". Reefs may be classified in terms of their origin, geographical location, depth, and topography . For example a tropical coral fringing reef, or a temperate rocky intertidal reef. A variety of biotic reef types exists, including oyster reefs and sponge reefs , but the most massive and widely distributed are tropical coral reefs . Although corals are major contributors to
656-476: The Rigs-to-Reefs program), scuttling ships , or by deploying rubble or construction debris . Other artificial reefs are purpose built (e.g. the reef balls ) from PVC or concrete. Shipwrecks become artificial reefs on the seafloor. Regardless of construction method, artificial reefs generally provide stable hard surfaces where algae and invertebrates such as barnacles , corals, and oysters attach;
697-471: The Newport breakwater. The dissipation of energy and relative calm water created in the lee of the breakwaters often encourage accretion of sediment (as per the design of the breakwater scheme). However, this can lead to excessive salient build up, resulting in tombolo formation, which reduces longshore drift shoreward of the breakwaters. This trapping of sediment can cause adverse effects down-drift of
738-664: The Red Sea coast, which is at least 4500 years old (ca. 2600–2550 BCE, reign of King Khufu ). The largest artificially created harbor is Jebel Ali in Dubai . Other large and busy artificial harbors include: The Ancient Carthaginians constructed fortified, artificial harbors called cothons . A natural harbor is a landform where a section of a body of water is protected and deep enough to allow anchorage. Many such harbors are rias . Natural harbors have long been of great strategic naval and economic importance, and many great cities of
779-530: The United States Army Corps of Engineers Coastal engineering manual (available for free online) and elsewhere. For detailed design the use of scaled physical hydraulic models remains the most reliable method for predicting real-life behavior of these complex structures. Breakwaters are subject to damage and overtopping in severe storms. Some may also have the effect of creating unique types of waves that attract surfers, such as The Wedge at
820-481: The adjacent unconsolidated surface with varying relief. They can be found in depth ranges from intertidal to deep water and provide a substrate for a large range of sessile benthic organisms, and shelter for a large range of mobile organisms. They are often located in sub-tropical, temperate, and sub-polar latitudes. Ancient reefs buried within stratigraphic sections are of considerable interest to geologists because they provide paleo-environmental information about
861-644: The breakwaters), and in turn the direction that sediment will flow and accumulate over time. The reduced heterogeneity in sea floor landscape introduced by breakwaters can lead to reduced species abundance and diversity in the surrounding ecosystems. As a result of the reduced heterogeneity and decreased depths that breakwaters produce due to sediment build up, the UV exposure and temperature in surrounding waters increase, which may disrupt surrounding ecosystems. There are two main types of offshore breakwater (also called detached breakwater): single and multiple. Single, as
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#1732772611273902-403: The breakwaters, leading to beach sediment starvation and increased coastal erosion . This may then lead to further engineering protection being needed down-drift of the breakwater development. Sediment accumulation in the areas surrounding breakwaters can cause flat areas with reduced depths, which changes the topographic landscape of the seabed. Salient formations as a result of breakwaters are
943-399: The choice depending on tidal range and water depth. They usually consist of large pieces of rock (granite) weighing up to 10–15 tonnes each, or rubble-mound. Their design is influenced by the angle of wave approach and other environmental parameters. Breakwater construction can be either parallel or perpendicular to the coast, depending on the shoreline requirements. Reef A reef
984-465: The collided wave energy and prevent the generation of standing waves. As design wave heights get larger, rubble mound breakwaters require larger armour units to resist the wave forces. These armour units can be formed of concrete or natural rock. The largest standard grading for rock armour units given in CIRIA 683 "The Rock Manual" is 10–15 tonnes. Larger gradings may be available, but the ultimate size
1025-461: The core and larger stones as an armour layer protecting the core from wave attack. Rock or concrete armour units on the outside of the structure absorb most of the energy, while gravels or sands prevent the wave energy's continuing through the breakwater core. The slopes of the revetment are typically between 1:1 and 1:2, depending upon the materials used. In shallow water, revetment breakwaters are usually relatively inexpensive. As water depth increases,
1066-525: The effect of the incident wave, creates waves in phase opposition to the incident wave downstream from the slabs. A submerged flexible mound breakwater can be employed for wave control in shallow water as an advanced alternative to the conventional rigid submerged designs. Further to the fact that, the construction cost of the submerged flexible mound breakwaters is less than that of the conventional submerged breakwaters, ships and marine organisms can pass them, if being deep enough. These marine structures reduce
1107-482: The framework and bulk material comprising a coral reef, the organisms most responsible for reef growth against the constant assault from ocean waves are calcareous algae, especially, although not entirely, coralline algae . Oyster larvae prefer to settle on adult oysters and thereby develop layers building upwards. These eventually form a fairly massive hard stony calcium carbonate structure on which other reef organisms like sponges and seaweeds can grow, and provide
1148-608: The framework builders. The corals which build reefs today, the Scleractinia , arose after the Permian–Triassic extinction event that wiped out the earlier rugose corals (as well as many other groups). They became increasingly important reef builders throughout the Mesozoic Era. They may have arisen from a rugose coral ancestor. Rugose corals built their skeletons of calcite and have a different symmetry from that of
1189-406: The free surface, positioned along a line parallel to the coast. Wave attenuators have four slabs facing the sea, one vertical slab, and two slabs facing the land; each slab is separated from the next by a space of 200 millimetres (7.9 in). The row of four sea-facing and two land-facing slabs reflects offshore wave by the action of the volume of water located under it which, made to oscillate under
1230-674: The location in Earth's history . In addition, reef structures within a sequence of sedimentary rocks provide a discontinuity which may serve as a trap or conduit for fossil fuels or mineralizing fluids to form petroleum or ore deposits . Corals, including some major extinct groups Rugosa and Tabulata , have been important reef builders through much of the Phanerozoic since the Ordovician Period. However, other organism groups, such as calcifying algae, especially members of
1271-450: The material requirements—and hence costs—increase significantly. Caisson breakwaters typically have vertical sides and are usually erected where it is desirable to berth one or more vessels on the inner face of the breakwater. They use the mass of the caisson and the fill within it to resist the overturning forces applied by waves hitting them. They are relatively expensive to construct in shallow water, but in deeper sites they can offer
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1312-638: The most exposed locations in very deep water, armour units are most often formed of concrete cubes, which have been used up to ~ 195 tonnes Archived 2019-05-12 at the Wayback Machine for the tip of the breakwater at Punta Langosteira near La Coruña, Spain. Preliminary design of armour unit size is often undertaken using the Hudson's equation , Van der Meer and more recently Van Gent et al.; these methods are all described in CIRIA 683 "The Rock Manual" and
1353-414: The name suggests, means the breakwater consists of one unbroken barrier, while multiple breakwaters (in numbers anywhere from two to twenty) are positioned with gaps in between (160–980 feet or 50–300 metres). The length of the gap is largely governed by the interacting wavelengths. Breakwaters may be either fixed or floating, and impermeable or permeable to allow sediment transfer shoreward of the structures,
1394-598: The red algae ( Rhodophyta ), and molluscs (especially the rudist bivalves during the Cretaceous Period) have created massive structures at various times. During the Cambrian Period, the conical or tubular skeletons of Archaeocyatha , an extinct group of uncertain affinities (possibly sponges), built reefs. Other groups, such as the Bryozoa, have been important interstitial organisms, living between
1435-549: The result of an accident. These are sometimes designed to increase the physical complexity of featureless sand bottoms to attract a more diverse range of organisms . Reefs are often quite near to the surface, but not all definitions require this. Earth's largest coral reef system is the Great Barrier Reef in Australia, at a length of over 2,300 kilometres (1,400 miles). The word "reef" traces its origins back to
1476-421: The rugosan corals (which disappeared in the late Permian). An artificial reef is a human-created underwater structure, typically built to promote marine life in areas with a generally featureless bottom, to control erosion, block ship passage, block the use of trawling nets, or improve surfing . Many reefs are built using objects that were built for other purposes, for example by sinking oil rigs (through
1517-471: The scleractinian corals, whose skeletons are aragonite . However, there are some unusual examples of well-preserved aragonitic rugose corals in the Late Permian . In addition, calcite has been reported in the initial post-larval calcification in a few scleractinian corals. Nevertheless, scleractinian corals (which arose in the middle Triassic) may have arisen from a non-calcifying ancestor independent of
1558-857: The seafloor. Cyanobacterial mounds were most abundant before the evolution of shelly macroscopic organisms, but they still exist today. Stromatolites , for instance, are microbial mounds with a laminated internal structure. Whereas, bryozoans and crinoids , common contributors to marine sediments during the Mississippian period , produce a different kind of mound. Although bryozoans are small and crinoid skeletons disintegrate, bryozoan and crinoid meadows can persist over time and produce compositionally distinct bodies of sediment with depositional relief. The Proterozoic Belt Supergroup contains evidence of possible microbial mat and dome structures similar to stromatolite and chicken reef complexes. Rocky reefs are underwater outcrops of rock projecting above
1599-431: The surrounding sea floor . However, reefs are held up by a macroscopic skeletal framework, as what is seen on coral reefs. Corals and calcareous algae grow on top of one another, forming a three-dimensional framework that is modified in various ways by other organisms and inorganic processes. Conversely, mounds lack a macroscopic skeletal framework. Instead, they are built by microorganisms or by organisms that also lack
1640-473: The world are located on them. Having a protected harbor reduces or eliminates the need for breakwaters as it will result in calmer waves inside the harbor. Some examples are: For harbors near the North and South poles , being ice-free is an important advantage, especially when it is year-round. Examples of these are: The world's southernmost harbor, located at Antarctica 's Winter Quarters Bay (77° 50′ South),
1681-612: Was first dredged in the early 20th century. In contrast, a natural harbor is surrounded on several sides by land. Examples of natural harbors include Sydney Harbour , New South Wales, Australia, Halifax Harbour in Halifax, Nova Scotia , Canada and Trincomalee Harbour in Sri Lanka. Artificial harbors are frequently built for use as ports. The oldest artificial harbor known is the Ancient Egyptian site at Wadi al-Jarf , on