A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying passengers or goods, or in support of specialized missions, such as defense and fishing. A "ship" was a sailing vessel with at least three square-rigged masts and a full bowsprit. Ships are distinguished from boats, based on size, load capacity, tradition. Ships have been important contributors to human commerce, they have supported the spread of colonization and the slave trade, but have served scientific and humanitarian needs. After the 15th century, new crops that had come from and to the Americas via the European seafarers contributed to the world population growth. Ship transport is responsible for the largest portion of world commerce; as of 2016, there were more than 49,000 merchant ships, totaling 1.8 billion dead weight tons. Of these 28% were oil tankers, 43% were bulk carriers, 13% were container ships. Ships are larger than boats, but there is no universally accepted distinction between the two.
Ships can remain at sea for longer periods of time than boats. A legal definition of ship from Indian case law is a vessel. A common notion is, but not vice versa. A US Navy rule of thumb is that ships heel towards the outside of a sharp turn, whereas boats heel towards the inside because of the relative location of the center of mass versus the center of buoyancy. American and British 19th Century maritime law distinguished "vessels" from other craft. In the Age of Sail, a full-rigged ship was a sailing vessel with at least three square-rigged masts and a full bowsprit. A number of large vessels are referred to as boats. Submarines are a prime example. Other types of large vessel which are traditionally called boats are Great Lakes freighters and ferryboats. Though large enough to carry their own boats and heavy cargoes, these vessels are designed for operation on inland or protected coastal waters. In most maritime traditions ships have individual names, modern ships may belong to a ship class named after its first ship.
In the northern parts of Europe and America a ship is traditionally referred to with a female grammatical gender, represented in English with the pronoun "she" if named after a man. This is not universal usage and some English language journalistic style guides advise using "it" as referring to ships with female pronouns can be seen as offensive and outdated. In many documents the ship name is introduced with a ship prefix being an abbreviation of the ship class, for example "MS" or "SV", making it easier to distinguish a ship name from other individual names in a text; the first known vessels could not be described as ships. The first navigators began to use animal skins or woven fabrics as sails. Affixed to the top of a pole set upright in a boat, these sails gave early ships range; this allowed men to explore allowing for the settlement of Oceania for example. By around 3000 BC, Ancient Egyptians knew, they used woven straps to lash the planks together, reeds or grass stuffed between the planks helped to seal the seams.
The Greek historian and geographer Agatharchides had documented ship-faring among the early Egyptians: "During the prosperous period of the Old Kingdom, between the 30th and 25th centuries BC, the river-routes were kept in order, Egyptian ships sailed the Red Sea as far as the myrrh-country." Sneferu's ancient cedar wood ship Praise of the Two Lands is the first reference recorded to a ship being referred to by name. The ancient Egyptians were at ease building sailboats. A remarkable example of their shipbuilding skills was the Khufu ship, a vessel 143 feet in length entombed at the foot of the Great Pyramid of Giza around 2500 BC and found intact in 1954, it is known that ancient Nubia/Axum traded with India, there is evidence that ships from Northeast Africa may have sailed back and forth between India/Sri Lanka and Nubia trading goods and to Persia and Rome. Aksum was known by the Greeks for having seaports for ships from Yemen. Elsewhere in Northeast Africa, the Periplus of the Red Sea reports that Somalis, through their northern ports such as Zeila and Berbera, were trading frankincense and other items with the inhabitants of the Arabian Peninsula well before the arrival of Islam as well as with Roman-controlled Egypt.
A panel found at Mohenjodaro depicted a sailing craft. Vessels were of many types; this treatise gives a technical exposition on the techniques of shipbuilding. It sets forth minute details about the various types of ships, their sizes, the materials from which they were built; the Yukti Kalpa Taru sums up in a condensed form all the available information. The Yukti Kalpa Taru gives sufficient information and dates to prove that, in ancient times, Indian shipbuilders had a good knowledge of the materials which were used in building ships. In addition to describing the qualities of the different types of wood and their suitability for shipbuilding, the Yukti Kalpa Taru gives an elaborate classification of ships based on their size; the oldest discovered sea faring hulled boat is the Late Bronze Age Uluburun shipwreck off the coast of Turkey, dating back to 1300 BC. The Phoenicians, the first to sail around
Pipeline transport is the long-distance transportation of a liquid or gas through a system of pipes—a pipeline—typically to a market area for consumption. The latest data from 2014 gives a total of less than 2,175,000 miles of pipeline in 120 countries of the world; the United States had 65%, Russia had 8%, Canada had 3%, thus 75% of all pipeline were in these three countries. Pipeline and Gas Journal's worldwide survey figures indicate that 118,623 miles of pipelines are planned and under construction. Of these, 88,976 miles represent projects in the design phase. Liquids and gases are transported in pipelines and any chemically stable substance can be sent through a pipeline. Pipelines exist for the transport of crude and refined petroleum, fuels – such as oil, natural gas and biofuels – and other fluids including sewage, water, hot water or steam for shorter distances. Pipelines are useful for transporting water for drinking or irrigation over long distances when it needs to move over hills, or where canals or channels are poor choices due to considerations of evaporation, pollution, or environmental impact.
Oil pipelines are made from steel or plastic tubes which are buried. The oil is moved through the pipelines by pump stations along the pipeline. Natural gas are pressurised into liquids known as Natural Gas Liquids. Natural gas pipelines are constructed of carbon steel. Hydrogen pipeline transport is the transportation of hydrogen through a pipe. Pipelines conveying flammable or explosive material, such as natural gas or oil, pose special safety concerns and there have been various accidents. Pipelines can be the target of theft, sabotage, or terrorist attacks. In war, pipelines are the target of military attacks, it is uncertain. Credit for the development of pipeline transport is disputed, with competing claims for Vladimir Shukhov and the Branobel company in the late 19th century, the Oil Transport Association, which first constructed a 2-inch wrought iron pipeline over a 6-mile track from an oil field in Pennsylvania to a railroad station in Oil Creek, in the 1860s. Pipelines are the most economical way to transport large quantities of oil, refined oil products or natural gas over land.
For example, in 2014, pipeline transport of crude oil cost about $5 per barrel, while rail transport cost about $10 to $15 per barrel. Trucking has higher costs due to the additional labor required. In Canada for natural gas and petroleum products, 97% are shipped by pipeline. Natural gas are pressurized into liquids known as Natural Gas Liquids. Small NGL processing facilities can be located in oil fields so the butane and propane liquid under light pressure of 125 pounds per square inch, can be shipped by rail, truck or pipeline. Propane can be used as a fuel in oil fields to heat various facilities used by the oil drillers or equipment and trucks used in the oil patch. EG: Propane will convert from a gas to a liquid under light pressure, 100 psi, give or take depending on temperature, is pumped into cars and trucks at less than 125 psi at retail stations. Pipelines and rail cars use about double that pressure to pump at 250 psi; the distance to ship propane to markets is much shorter, as thousands of natural-gas processing plants are located in or near oil fields.
Many Bakken Basin oil companies in North Dakota, Montana and Saskatchewan gas fields separate the NGLs in the field, allowing the drillers to sell propane directly to small wholesalers, eliminating the large refinery control of product and prices for propane or butane. The most recent major pipeline to start operating in North America, is a TransCanada natural gas line going north across the Niagara region bridges with Marcellus shale gas from Pennsylvania and others tied in methane or natural gas sources, into the Canadian province of Ontario as of the fall of 2012, supplying 16 percent of all the natural gas used in Ontario; this new US-supplied natural gas displaces the natural gas shipped to Ontario from western Canada in Alberta and Manitoba, thus dropping the government regulated pipeline shipping charges because of the shorter distance from gas source to consumer. To avoid delays and US government regulation, many small and large oil producers in North Dakota have decided to run an oil pipeline north to Canada to meet up with a Canadian oil pipeline shipping oil from west to east.
This allows the Bakken Basin and Three Forks oil producers to get higher negotiated prices for their oil because they will not be restricted to just one wholesale market in the US. The distance from the biggest oil patch in North Dakota, in Williston, North Dakota, is only about 85 miles or 137 kilometers to the Canada–US border and Manitoba. Mutual funds and joint ventures are big investors in new gas pipelines. In the fall of 2012, the US began exporting propane to Europe, known as LPG, as wholesale prices there are much higher than in North America. Additionally, a pipeline is being constructed from North Dakota to Illinois known as the Dakota Access Pipeline; as more North American pipelines are built more exports of LNG, propane and other natural gas products occur on all three US coasts. To give insight, North Dakota Bakken region's oil production has grown
Rail transport is a means of transferring of passengers and goods on wheeled vehicles running on rails known as tracks. It is commonly referred to as train transport. In contrast to road transport, where vehicles run on a prepared flat surface, rail vehicles are directionally guided by the tracks on which they run. Tracks consist of steel rails, installed on ties and ballast, on which the rolling stock fitted with metal wheels, moves. Other variations are possible, such as slab track, where the rails are fastened to a concrete foundation resting on a prepared subsurface. Rolling stock in a rail transport system encounters lower frictional resistance than road vehicles, so passenger and freight cars can be coupled into longer trains; the operation is carried out by a railway company, providing transport between train stations or freight customer facilities. Power is provided by locomotives which either draw electric power from a railway electrification system or produce their own power by diesel engines.
Most tracks are accompanied by a signalling system. Railways are a safe land transport system. Railway transport is capable of high levels of passenger and cargo utilization and energy efficiency, but is less flexible and more capital-intensive than road transport, when lower traffic levels are considered; the oldest known, man/animal-hauled railways date back to the 6th century BC in Greece. Rail transport commenced in mid 16th century in Germany in the form of horse-powered funiculars and wagonways. Modern rail transport commenced with the British development of the steam locomotives in the early 19th century, thus the railway system in Great Britain is the oldest in the world. Built by George Stephenson and his son Robert's company Robert Stephenson and Company, the Locomotion No. 1 is the first steam locomotive to carry passengers on a public rail line, the Stockton and Darlington Railway in 1825. George Stephenson built the first public inter-city railway line in the world to use only the steam locomotives all the time, the Liverpool and Manchester Railway which opened in 1830.
With steam engines, one could construct mainline railways, which were a key component of the Industrial Revolution. Railways reduced the costs of shipping, allowed for fewer lost goods, compared with water transport, which faced occasional sinking of ships; the change from canals to railways allowed for "national markets" in which prices varied little from city to city. The spread of the railway network and the use of railway timetables, led to the standardisation of time in Britain based on Greenwich Mean Time. Prior to this, major towns and cities varied their local time relative to GMT; the invention and development of the railway in the United Kingdom was one of the most important technological inventions of the 19th century. The world's first underground railway, the Metropolitan Railway, opened in 1863. In the 1880s, electrified trains were introduced, leading to electrification of tramways and rapid transit systems. Starting during the 1940s, the non-electrified railways in most countries had their steam locomotives replaced by diesel-electric locomotives, with the process being complete by the 2000s.
During the 1960s, electrified high-speed railway systems were introduced in Japan and in some other countries. Many countries are in the process of replacing diesel locomotives with electric locomotives due to environmental concerns, a notable example being Switzerland, which has electrified its network. Other forms of guided ground transport outside the traditional railway definitions, such as monorail or maglev, have been tried but have seen limited use. Following a decline after World War II due to competition from cars, rail transport has had a revival in recent decades due to road congestion and rising fuel prices, as well as governments investing in rail as a means of reducing CO2 emissions in the context of concerns about global warming; the history of rail transport began in the 6th century BC in Ancient Greece. It can be divided up into several discrete periods defined by the principal means of track material and motive power used. Evidence indicates that there was 6 to 8.5 km long Diolkos paved trackway, which transported boats across the Isthmus of Corinth in Greece from around 600 BC.
Wheeled vehicles pulled by men and animals ran in grooves in limestone, which provided the track element, preventing the wagons from leaving the intended route. The Diolkos was in use for over 650 years, until at least the 1st century AD; the paved trackways were later built in Roman Egypt. In 1515, Cardinal Matthäus Lang wrote a description of the Reisszug, a funicular railway at the Hohensalzburg Fortress in Austria; the line used wooden rails and a hemp haulage rope and was operated by human or animal power, through a treadwheel. The line still exists and is operational, although in updated form and is the oldest operational railway. Wagonways using wooden rails, hauled by horses, started appearing in the 1550s to facilitate the transport of ore tubs to and from mines, soon became popular in Europe; such an operation was illustrated in Germany in 1556 by Georgius Agricola in his work De re metallica. This line used "Hund" carts with unflanged wheels running on wooden planks and a vertical pin on the truck fitting into the gap between the planks to keep it going the right way.
The miners called the wagons Hunde from the noise. There are many references to their use in central Europe in the 16th century; such a transport system was used by German miners at Cal
A wharf, staith or staithe is a structure on the shore of a harbor or on the bank of a river or canal where ships may dock to load and unload cargo or passengers. Such a structure includes one or more berths, may include piers, warehouses, or other facilities necessary for handling the ships. Wharfs are considered to be a series of docks in which boats are stationed. A wharf comprises a fixed platform on pilings. Commercial ports may have warehouses that serve as interim storage: where it is sufficient a single wharf with a single berth constructed along the land adjacent to the water is used. A pier, raised over the water rather than within it, is used for cases where the weight or volume of cargos will be low. Smaller and more modern wharves are sometimes built on flotation devices to keep them at the same level as the ship during changing tides. In everyday parlance the term quay is common in the United Kingdom, Canada and many other Commonwealth countries, the Republic of Ireland, whereas the term wharf is more common in the United States.
In some contexts wharf and quay may be used to mean berth, or jetty. In old ports such as London many old wharves have been converted to residential or office use. Certain early railways in England referred to goods loading points as "wharves"; the term was carried over from marine usage. The person, resident in charge of the wharf was referred to as a "wharfinger". One explanation is that the word wharf comes from the Old English "warft" or the Old Dutch word "werf", which both evolved to mean "yard", an outdoor place where work is done, like a shipyard or a lumberyard. Werf or werva in Old Dutch referred to inhabited ground, not yet built on, or alternatively to a terp; this could explain the name Ministry Wharf located at Saunderton, just outside High Wycombe, nowhere near any body of water. In support of this explanation is the fact that many places in England with "wharf" in their names are in areas with a high Dutch influence, for example the Norfolk broads. In the northeast and east of England the term staith or staithe is used.
The two terms have had a geographical distinction: those to the north in the Kingdom of Northumbria used the Old English spelling staith, southern sites of the Danelaw took the Danish spelling staithe. Both referred to jetties or wharves. In time, the northern coalfields of Northumbria developed coal staiths for loading coal onto ships and these would adopt the staith spelling as a distinction from simple wharves: for example, Dunston Staiths in Gateshead and Brancaster Staithe in Norfolk. However, the term staith may be used to refer only to loading chutes or ramps used for bulk commodities like coal in loading ships and barges. Quay, on the other hand, has its origin in the Proto-Celtic language. Before it changed to its current form under influence of the modern French quai, its Middle English spelling was key, keye or caye; this in turn came from the Old Norman cai, both meaning "sand bank". The Old French term came from Gaulish caium tracing back to the Proto-Celtic *kagio- "to encompass, enclose".
Modern cognates include Welsh cae "fence, hedge" and Cornish ke "hedge", the Dutch kade. Bollard Canal basin Dock Safeguarded wharf The dictionary definition of wharf at Wiktionary The dictionary definition of quay at Wiktionary
A slipway known as boat ramp or launch or boat deployer, is a ramp on the shore by which ships or boats can be moved to and from the water. They are used for building and repairing ships and boats, for launching and retrieving small boats on trailers towed by automobiles and flying boats on their undercarriage; the nautical terms ways and skids are alternative names for slipway. A ship undergoing construction in a shipyard is said to be on the ways. If a ship is scrapped there, she is said to be broken up in the ways; as the word "slip" implies, the ships or boats are moved over the ramp, by way of crane or fork lift. Prior to the move the vessel's hull is coated with grease, which allows the ship or boat to "slip" off of the ramp and progress safely into the water. Slipways can only dry-dock or repair smaller ships. Pulling large ships against the greased ramp would require too much force. Therefore, for dry-docking large ships, one must use carriages supported by wheels or by roller-pallets; these types of dry-docking installations are called "marine railways".
The words "slip" and "slipway" are used for all dry-docking installations that use a ramp. In its simplest form, a slipway is a plain ramp made of concrete, stone or wood; the height of the tide can limit the usability of a slip: unless the ramp continues well below the low water level it may not be usable at low tide. There is a flat paved area on the landward end; when used for building and repairing boats or small ships, the vessel is moved on a wheeled carriage, run down the ramp until the vessel can float on or off the carriage. Such slipways are used for repair as well as for putting newly built vessels in the water; when used for launching and retrieving small boats, the trailer is placed in the water. The boat may be pulled off; when recovering the boat from the water, it is winched back up the trailer. Whaling ships are equipped with a slipway at the back, to assist in hauling harpooned whales onto the main deck, where they are flensed. To achieve a safe launch of some types of land-based lifeboats in bad weather and difficult sea conditions, the lifeboat and slipway are designed so that the lifeboat slides down a steep steel slip under gravity.
For large ships, slipways are only used in construction of the vessel. They may be arranged perpendicular to the shore line. On launching, the vessel slides down the slipway on the ways; the process of transferring the vessel to the water is known as launching and is a ceremonial and celebratory occasion. It is the point. At this point the hull is complete and the propellers and associated shafting are in place, but dependent on the depth of water and weight the engines might have not been fitted or the superstructure may not be completed. In a perpendicular slipway, the ship is built with its stern facing the water. Modern slipways take the form of a reinforced concrete mat of sufficient strength to support the vessel, with two "barricades" that extend to well below the water level taking into account tidal variations; the barricades support the two launch ways. The vessel is built upon temporary cribbing, arranged to give access to the hull's outer bottom, to allow the launchways to be erected under the complete hull.
When it is time to prepare for launching a pair of standing ways are erected under the hull and out onto the barricades. The surface of these ways are greased. A pair of sliding ways is placed on top, under the hull, a launch cradle with bow and stern poppets is erected on these sliding ways; the weight of the hull is transferred from the build cribbing onto the launch cradle. Provision is made to hold the vessel in place and release it at the appropriate moment in the launching ceremony, these are either a weak link designed to be cut at a signal or a mechanical trigger controlled by a switch from the ceremonial platform; some slipways is launched sideways. This is done where the limitations of the water channel would not allow lengthwise launching, but occupies a much greater length of shore; the Great Eastern built by Brunel was built this way as were many landing craft during World War II. This method requires many more sets of ways to support the weight of the ship. In both cases heavy chains are attached to the ship and the drag effect is used to slow the vessel once afloat until tugboats can move the hull to a jetty for fitting out.
The practice of building on a slipway is dying out with the increasing size of vessels from about the 1970s. Part of the reason is the space requirement for slowing and maneuvering the vessel after it has left the slipway, but the sheer size of the vessel causes design problems, since the hull is supported only at its end points during the launch process and this imposes stresses not met during normal operation. Boat lift Dry dock Ferry slip Harbor Patent slip Port Ship cradle Shiplift
A pier is a raised structure in a body of water supported by well-spaced piles or pillars. Bridges and walkways may all be supported by piers, their open structure allows tides and currents to flow unhindered, whereas the more solid foundations of a quay or the spaced piles of a wharf can act as a breakwater, are more liable to silting. Piers can range in size and complexity from a simple lightweight wooden structure to major structures extended over 1600 metres. In American English, a pier may be synonymous with a dock. Piers have been built for several purposes, because these different purposes have distinct regional variances, the term pier tends to have different nuances of meaning in different parts of the world, thus in North America and Australia, where many ports were, until built on the multiple pier model, the term tends to imply a current or former cargo-handling facility. In Europe in contrast, where ports more use basins and river-side quays than piers, the term is principally associated with the image of a Victorian cast iron pleasure pier.
However, the earliest piers pre-date the Victorian age. Piers can be categorized into different groupings according to the principal purpose. However, there is considerable overlap between these categories. For example, pleasure piers also allow for the docking of pleasure steamers and other similar craft, while working piers have been converted to leisure use after being rendered obsolete by advanced developments in cargo-handling technology. Many piers are floating piers, to ensure that the piers raise and lower with the tide along with the boats tied to them; this prevents a situation where lines become overly loose by rising or lowering tides. An overly taut or loose tie-line can damage boats by pulling them out of the water or allowing them so much leeway that they bang forcefully against the sides of the pier. Working piers were built for the handling of passengers and cargo off ships or canal boats. Working piers themselves fall into two different groups. Longer individual piers are found at ports with large tidal ranges, with the pier stretching far enough off shore to reach deep water at low tide.
Such piers provided an economical alternative to impounded docks where cargo volumes were low, or where specialist bulk cargo was handled, such as at coal piers. The other form of working pier called the finger pier, was built at ports with smaller tidal ranges. Here the principal advantage was to give a greater available quay length for ships to berth against compared to a linear littoral quayside, such piers are much shorter; each pier would carry a single transit shed the length of the pier, with ships berthing bow or stern in to the shore. Some major ports consisted of large numbers of such piers lining the foreshore, classic examples being the Hudson River frontage of New York, or the Embarcadero in San Francisco; the advent of container shipping, with its need for large container handling spaces adjacent to the shipping berths, has made working piers obsolete for the handling of general cargo, although some still survive for the handling of passenger ships or bulk cargos. One example, is in use in Progreso, Yucatán, where a pier extends more than 4 miles into the Gulf of Mexico, making it the longest pier in the world.
The Progreso Pier supplies much of the peninsula with transportation for the fishing and cargo industries and serves as a port for large cruise ships in the area. Many other working piers have been demolished, or remain derelict, but some have been recycled as pleasure piers; the best known example of this is Pier 39 in San Francisco. At Southport and the Tweed River on the Gold Coast in Australia, there are piers that support equipment for a sand bypassing system that maintains the health of sandy beaches and navigation channels. Pleasure piers were first built in Britain during the early 19th century; the earliest structures were Ryde Pier, built in 1813/4, Trinity Chain Pier near Leith, built in 1821, Brighton Chain Pier, built in 1823. Only the oldest of these piers still remains. At that time the introduction of the railways for the first time permitted mass tourism to dedicated seaside resorts; the large tidal ranges at many such resorts meant that for much of the day, the sea was not visible from dry land.
The pleasure pier was the resorts' answer, permitting holidaymakers to promenade over and alongside the sea at all times. The world's longest pleasure pier is at Southend-on-sea and extends 1.3 miles into the Thames estuary. With a length of 2,745 feet, the longest pier on the West Coast of the US is the Santa Cruz Wharf. Providing a walkway out to sea, pleasure piers include amusements and theatres as part of the attraction; such a pier may be open air, closed, or open closed. Sometimes a pier has two decks. Galveston Island Historic Pleasure Pier in Galveston, Texas has 1 roller coaster, 15 rides, carnival games and souvenir shops. Early pleasure piers were of wooden construction, with iron structures being introduced with the construction in 1855 of Margate Jetty, in Margate, England. Margate was never repaired; the longest iron pleasure pier still remaining in Southend-on-Sea,Essex and dates from 1829 - however the world's oldest iron pier dates from 1834 and is in Gravesend, Kent. In a 2006 UK poll, the public voted the seaside pier onto the list of icons of England.
Many piers are built for the purpose of providing boatless anglers access to fishing grounds that are otherwise inaccessible. Many "Free Piers" are available in larger harbors. Free Piers are primarily used for fishing. See the List of piers article for detai
Breakwaters are structures constructed near the coasts as part of coastal management or to protect an anchorage from the effects of both weather and longshore drift. Breakwaters reduce the intensity of wave action in inshore waters and thereby reduce coastal erosion or provide safe harbourage. Breakwaters may be small structures designed to protect a sloping beach and placed 100–300 feet offshore in shallow water. An anchorage is only safe if ships anchored there are protected from the force of high winds and powerful waves by some large underwater barrier which they can shelter behind. Natural harbours are formed by such barriers as 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, Cherbourg, have been enhanced or extended by breakwaters made of rock. The dissipation of energy and relative calm water created in the lee of the breakwaters encourage accretion of sediment.
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 the breakwaters, leading to beach sediment starvation and increased erosion; this may lead to further engineering protection being needed down-drift of the breakwater development. Breakwaters are subject to damage, overtopping in severe storms. Breakwaters can be constructed with one end linked to the shore, otherwise they are positioned offshore 330–1,970 feet from the original shoreline. There are two main types of offshore breakwater and multiple. Length of gap is governed by the interacting wavelengths. Breakwaters may be either fixed or floating, impermeable or permeable to allow sediment transfer shoreward of the structures, the choice depending on tidal range and water depth, they consist of large pieces of rock weighing up to 16 tonnes each, or rubble-mound. Their design is influenced by the angle of other environmental parameters.
Breakwater construction can be either parallel or perpendicular to the coast, depending on the shoreline requirements. Salient formations as a result of breakwaters are a function of the distance the breakwaters are built from the coast, the direction at which the wave hits the breakwater, the angle at which the breakwater is built. 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, in turn the direction that sediment will flow and accumulate over time. A breakwater structure is designed to absorb the energy of the waves that hit it, either by using mass, or by using a revetment slope. In coastal engineering, a revetment is a land backed structure whilst a breakwater is a sea backed structure. 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 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 between 1:1 and 1:2, depending upon the materials used. In shallow water, revetment breakwaters are relatively inexpensive; as water depth increases, the material requirements—and hence costs—increase significantly. Caisson breakwaters have vertical sides and are 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 expensive to construct in shallow water, but in deeper sites they can offer 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 is a wave-absorbing caisson, including various types of perforation in the front wall; such structures have been used in the offshore oil-industry, but on coastal projects requiring rather low-crested structures, e.g. on an urban promenade where the sea view is an important aspect like in Beirut and Monaco. In the latter, a project is presently ongoing at the Anse du Portier including 18 wave-absorbing 27 m high caissons. Wave attenuators consist of concrete elements properly dimensioned placed horizontally just one feet under the free surface, positioned along a line parallel to the coast; the wave attenuator has four sea-side slabs, one vertical slab, two rear-side slabs, each separated from the next by a space of 200 millimetres. This row of 4 front side slabs and two rear side slabs