Breakwaters are structures constructed on coasts as part of coastal defence

Coastal management

In some jurisdictions the terms sea defense and coastal protection are used to mean, respectively, defense against flooding and erosion...

 or to protect an anchorage from the effects of weather

Weather

Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...

 and longshore drift

Longshore drift

Longshore drift consists of the transportation of sediments along a coast at an angle to the shoreline, which is dependent on prevailing wind direction, swash and backwash. This process occurs in the littoral zone, and in or within close proximity to the surf zone...

.

Purposes of breakwaters

Offshore breakwaters, also called bulkheads, reduce the intensity of wave action in inshore waters and thereby reduce coastal erosion

Coastal erosion

Coastal erosion is the wearing away of land and the removal of beach or dune sediments by wave action, tidal currents, wave currents, or drainage...

. They are constructed some distance away from the coast

Coast

A coastline or seashore is the area where land meets the sea or ocean. A precise line that can be called a coastline cannot be determined due to the dynamic nature of tides. The term "coastal zone" can be used instead, which is a spatial zone where interaction of the sea and land processes occurs...

 or built with one end linked to the coast

Coast

A coastline or seashore is the area where land meets the sea or ocean. A precise line that can be called a coastline cannot be determined due to the dynamic nature of tides. The term "coastal zone" can be used instead, which is a spatial zone where interaction of the sea and land processes occurs...

. The breakwaters may be small structures, placed one to three hundred feet offshore in relatively shallow water, designed to protect a gently sloping beach

Beach

A beach is a geological landform along the shoreline of an ocean, sea, lake or river. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles or cobblestones...

. Breakwaters may be either fixed or floating: the choice depends on normal water depth and tidal range. They are made of large pieces of concrete and are spaced about 50m from each other.
Breakwater construction is usually parallel or perpendicular to the coast to maintain tranquility condition in the port. Most of breakwater construction depends upon wave approach and considering some other environmental parameters

When oncoming wave

Ocean surface wave

In fluid dynamics, wind waves or, more precisely, wind-generated waves are surface waves that occur on the free surface of oceans, seas, lakes, rivers, and canals or even on small puddles and ponds. They usually result from the wind blowing over a vast enough stretch of fluid surface. Waves in the...

s hit these breakwaters, their erosive power is concentrated on these structures some distance away from the coast

Coast

A coastline or seashore is the area where land meets the sea or ocean. A precise line that can be called a coastline cannot be determined due to the dynamic nature of tides. The term "coastal zone" can be used instead, which is a spatial zone where interaction of the sea and land processes occurs...

. In this way, there is an area of slack water

Slack water

Slack water, which used to be known as 'The stand of the tide', is a short period in a body of tidal water either side of high water or low water essentially when the water is completely unstressed, and therefore with no rise or fall of the tide and no movement either way in the tidal stream, and...

 behind the breakwaters. Deposition occurring in these waters and beaches can be built up or extended in these waters. However, nearby unprotected sections of the beaches do not receive fresh supplies of sediment

Sediment

Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....

s and may gradually shrink due to erosion

Erosion

Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

, namely longshore drift

Longshore drift

Longshore drift consists of the transportation of sediments along a coast at an angle to the shoreline, which is dependent on prevailing wind direction, swash and backwash. This process occurs in the littoral zone, and in or within close proximity to the surf zone...

.

Breakwaters are subject to damage, and overtopping by big storms can lead to problems of drainage of water that gets behind them. The wall also serves to encourage erosion of beach deposits from the foot of the wall and can increase longshore sediment transport

Sediment transport

Sediment transport is the movement of solid particles , typically due to a combination of the force of gravity acting on the sediment, and/or the movement of the fluid in which the sediment is entrained...

.

Protection of anchorages

An anchorage is only safe when ship

Ship

Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...

s anchored there are protected from the force of high winds and powerful waves by some large underwater

Underwater

Underwater is a term describing the realm below the surface of water where the water exists in a natural feature such as an ocean, sea, lake, pond, or river. Three quarters of the planet Earth is covered by water...

 barrier which they can shelter behind. Natural harbours are formed by natural barriers such as headlands

Headlands and bays

Headlands and bays are two related features of the coastal environment.- Geology and geography :Headlands and bays are often found on the same coastline. A bay is surrounded by land on three sides, whereas a headland is surrounded by water on three sides. Headlands are characterized by high,...

 or reef

Reef

In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....

s. Mobile harbours, such as the D-Day

D-Day

D-Day is a term often used in military parlance to denote the day on which a combat attack or operation is to be initiated. "D-Day" often represents a variable, designating the day upon which some significant event will occur or has occurred; see Military designation of days and hours for similar...

 Mulberry harbour

Mulberry harbour

A Mulberry harbour was a British type of temporary harbour developed in World War II to offload cargo on the beaches during the Allied invasion of Normandy....

s were floated into position and acted as breakwaters. Some natural harbours, such as those in Plymouth Sound

Plymouth Sound

Plymouth Sound, or locally just The Sound, is a bay at Plymouth in England.Its southwest and southeast corners are Penlee Point in Cornwall and Wembury Point on Devon, a distance of about 3 nautical miles . Its northern limit is Plymouth Hoe giving a north-south distance of nearly 3 nautical miles...

, Portland Harbour

Portland Harbour

Portland Harbour is located beside the Isle of Portland, off Dorset, on the south coast of England. It is one of the largest man-made harbours in the world. Grid reference: .-History:...

 and Cherbourg, have been enhanced or extended by breakwaters made of rock.

Types of breakwater structures

A breakwater is constructed some distance away from the coast or built with one end linked to the coast. Breakwaters may be either fixed or floating: the choice depends on normal water depth and tidal range. A breakwater structure is designed to absorb the energy of the waves that hit it. This is done either by using mass (e.g. with caissons) or by using a revetment slope (e.g. with rock or concrete armour units).

Caisson

Caisson (engineering)

In geotechnical engineering, a caisson is a retaining, watertight structure used, for example, to work on the foundations of a bridge pier, for the construction of a concrete dam, or for the repair of ships. These are constructed such that the water can be pumped out, keeping the working...

 breakwaters typically have vertical sides and are usually used where it is desirable to berth

Berth (moorings)

A berth is a location in a port or harbour used specifically for mooring vessels while not at sea.-Locations in a port:Berth is the term used in ports and harbors to define a specific location where a vessel may be berthed, usually for the purposes of loading and unloading.Most berths will be...

 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 a significant saving over revetment breakwaters.

Rubble mound breakwaters use the voids in the structure to dissipate the wave energy. Rock or concrete armour units on the outside of the structure absorb most of the energy, while gravels or sands are used to prevent the wave energy 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 cheap, but as water depth increases, the material requirements, and hence costs, increase significantly.

Advanced Numerical Study

The Maritime Engineering Division of the University of Salerno

University of Salerno

The University of Salerno is a university located in Salerno, Italy. It is organized in 10 Faculties.-History:Salerno, a city in which, as Michelet said, “emperors, kings, popes, and the richest barons all had their own doctor”, developed during the Middle Ages around its prestigious School of...

  (MEDUS) developed a new procedure to study, in greater detail, the interactions between maritime breakwaters (submerged or emerged) and the waves, by an integrated use of CAD

Computer-aided design

Computer-aided design , also known as computer-aided design and drafting , is the use of computer technology for the process of design and design-documentation. Computer Aided Drafting describes the process of drafting with a computer...

 and CFD

Computational fluid dynamics

Computational fluid dynamics, usually abbreviated as CFD, is a branch of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems that involve fluid flows. Computers are used to perform the calculations required to simulate the interaction of liquids and gases with...

 software.

In the numerical simulations the filtration motion of the fluid within the interstices, which normally exist in a breakwater, is estimated by integrating the RANS equations, coupled with a RNG

Random number generation

A random number generator ) is a computational or physical device designed to generate a sequence of numbers or symbols that lack any pattern, i.e. appear random....

 turbulence model, inside the voids, instead of using classical equations for porous

Porosity

Porosity or void fraction is a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0–1, or as a percentage between 0–100%...

 media.

The breakwaters were modelled, as it happens in the full size construction or in physical laboratory tests, by overlapping three-dimensional elements and having the numerical grid thickened in order to have some computational nodes along the flow paths among the breakwater’s blocks.

Also See

• Accropode
• Akmon
  Akmon
  An akmon is a multi-tonne concrete block used for breakwater and seawall armouring. It was originally designed in the Netherlands in the 1960s, as an improvement on the tetrapod.-References:...
  
  
• Artificial reef
  Artificial reef
  An artificial reef is a human-made underwater structure, typically built to promote marine life in areas with a generally featureless bottom, control erosion, block ship passage, or improve surfing....
  
  
• Dolos
  Dolos
  A dolos is a concrete block in a complex geometric shape weighing up to 20 tons, used in great numbers to protect harbour walls from the erosive force of ocean waves...
  
   invented by South African engineer in East London
• Gabion
  Gabion
  Gabions are cages, cylinders, or boxes filled with soil or sand that are used in civil engineering, road building, and military applications. For erosion control caged riprap is used. For dams or foundation construction, cylindrical metal structures are used...
  
  
• Groyne
  Groyne
  A groyne is a rigid hydraulic structure built from an ocean shore or from a bank that interrupts water flow and limits the movement of sediment. In the ocean, groynes create beaches, or avoid having them washed away by longshore drift. In a river, groynes prevent erosion and ice-jamming, which...
  
  
• Jetty
  Jetty
  A jetty is any of a variety of structures used in river, dock, and maritime works that are generally carried out in pairs from river banks, or in continuation of river channels at their outlets into deep water; or out into docks, and outside their entrances; or for forming basins along the...
  
  
• Mole (architecture)
  Mole (architecture)
  A mole is a massive structure, usually of stone, used as a pier, breakwater, or a causeway between places separated by water. The word comes from Middle French mole and ultimately Latin mōlēs meaning a large mass, especially of rock and has the same root as molecule.Historically, the term "mole"...
  
  
• Pier
  Pier
  A pier is a raised structure, including bridge and building supports and walkways, over water, typically supported by widely spread piles or pillars...
  
  
• Port
  Port
  A port is a location on a coast or shore containing one or more harbors where ships can dock and transfer people or cargo to or from land....
  
  
• Seawall
  Seawall
  A seawall is a form of coastal defence constructed where the sea, and associated coastal processes, impact directly upon the landforms of the coast. The purpose of a seawall is to protect areas of human habitation, conservation and leisure activities from the action of tides and waves...
  
  
• IAS TM
• Tetrapod
  Tetrapod (structure)
  In coastal engineering, a Tetrapod is a four-legged concrete structure used as armour unit on breakwaters. The Tetrapod's shape is designed to dissipate the force of incoming waves by allowing water to flow around rather than against it, and to reduce displacement by allowing a random distribution...
  
  
• Xbloc
  Xbloc
  An Xbloc is an interlocking concrete block or armour unit designed to protect shores, harbour walls, seawalls, breakwaters and other coastal structures from the direct impact of incoming waves...
  
  

External links

• USGS Oblique Aerial Photography — Coastal Erosion from El-Niño Winter Storms October, 1997 & April, 1998
• Channel Coastal Observatory — Breakwaters
• Shapes of breakwater armour units and year of their introduction
• SeaBull Marine, Inc. — Shoreline Erosion Reversal Systems
• WaveBrake - Wave attenuation specialists
• IAS Breakwater in Facebook