All Topics  
Breakwater (structure)

 
Breakwater (structure)

 
   Email Print
   Bookmark   Link
 

 

Breakwater (structure)
 
 
  Topics Breakwater (structure) Topic Home

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, defence against flooding and erosion....
 or to protect an anchorage from the effects of weather
Weather

Weather is a set of all the Phenomenon occurring in a given atmosphere at a given time. Weather phenomena lie in the hydrosphere and troposphere....
 and longshore drift
Longshore drift

Longshore drift is a geology process by which sediments such as sand or other materials, move along a beach shore. It uses the process of swash to push the material up the beach and backwash down the beach; until it reaches a groyne or another obstacle....
.

hore 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 or the removal of beach or dune sediments by wave action, Tide, wave currents, or drainage . Waves, generated by storms, wind, or fast moving motor craft, cause coastal erosion, which may take the form of long-term losses of sediment and Rock , or merely the temporary redistribution of coastal sed...
.






Discussion
Ask a question about 'Breakwater (structure)'
Start a new discussion about 'Breakwater (structure)'
Answer questions from other users
Full Discussion Forum



Encyclopedia


Breakwater Break1 New(usgs)
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, defence against flooding and erosion....
 or to protect an anchorage from the effects of weather
Weather

Weather is a set of all the Phenomenon occurring in a given atmosphere at a given time. Weather phenomena lie in the hydrosphere and troposphere....
 and longshore drift
Longshore drift

Longshore drift is a geology process by which sediments such as sand or other materials, move along a beach shore. It uses the process of swash to push the material up the beach and backwash down the beach; until it reaches a groyne or another obstacle....
.

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 or the removal of beach or dune sediments by wave action, Tide, wave currents, or drainage . Waves, generated by storms, wind, or fast moving motor craft, cause coastal erosion, which may take the form of long-term losses of sediment and Rock , or merely the temporary redistribution of coastal sed...
. They are constructed some distance away from the coast
Coast

The coast is defined as that part of the land adjoining or near the ocean or its saltwater arms. A precise line that can be called a coastline cannot be determined due to the process of tides....
 or built with one end linked to the coast
Coast

The coast is defined as that part of the land adjoining or near the ocean or its saltwater arms. A precise line that can be called a coastline cannot be determined due to the process of tides....
. 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

File:MiamiSouthBeachPanoramaEdit.jpgA beach is a geology landform along the shoreline of a body of water. It usually consists of loose particles which are often composed of Rock , such as sand, gravel, shingle beach, pebbles, or cobble....
. Breakwaters may be either fixed or floating: the choice depends on normal water depth and tidal range. Construction Breakwaters 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....
s hit these breakwaters, their erosive power is concentrated on these structures some distance away from the coast
Coast

The coast is defined as that part of the land adjoining or near the ocean or its saltwater arms. A precise line that can be called a coastline cannot be determined due to the process of tides....
. In this way, there is an area of slack water
Slack water

Slack water, or slack tide, is the period during which no appreciable tide current flows in a body of water.Slack water usually happens near high tide and low tide, and occurs when the direction of the tidal current reverses....
 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 eroded sediment
Sediment

Sediment is any particulate matter that can be sediment transport by fluid dynamics, and which eventually is deposited.Sediments are most often transported by water transported by wind and glaciers....
s and may gradually shrink due to erosion
Erosion

For morphological image processing operations, see Erosion 'For use of in dermatopathology, see Erosion Erosion is the removal of solids in the natural environment....
.

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.

Portland Harbour Hood Entrance

Protection of anchorages


An anchorage is only safe when ship
Ship

A ship is a large watercraft that floats on water. Ships are generally distinguished from boats based on size. Ships may be found on lakes, seas, and rivers and they allow for a variety of activities, such as the ferry or cargo ships, fishing, cruise ship, Coast guard, and warship....
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....
 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....
 or reef
Reef

In nautical terminology, a reef is a Rock , bar , or other feature lying beneath the surface of the water .Many reefs result from abiotic processes?deposition of sand, wave erosion planning down rock outcrops, and other natural processes?but the best-known reefs are the coral reefs of tropical waters developed through biotic processes do...
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 terms....
 Mulberry harbour
Mulberry harbour

A Mulberry harbour was a type of temporary harbour developed in World War II to offload cargo on the beaches during the Battle of Normandy.Two prefabricated or artificial military harbours were taken across the English Channel from UK with the invading army in sections and assembled off the coast of Normandy as part of the D-Day invasi...
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 Headlands and bays at Plymouth in England.Its south west and south east corners are Penlee Point, Rame in Cornwall and Wembury Point on Devon, a distance of about 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....
 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 foundation of a bridge pier , for the construction of a concrete dam, or for the repair of ships....
 breakwaters typically have vertical sides and are usually used where it is desirable to berth
Berth

The term berth is used to describe a bed on a boat or train, or a location in a port or harbour used specifically for Mooring vessels while not at sea , or for describing playoff positions for teams with no initial competition in sports, also for a place on the hit television show University Challenge....
 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.

See also

  • 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 ....
  • Dolos
    Dolos

    A dolos is an unusually-shaped concrete block weighing up to 20 tons which is used in great numbers to protect harbour walls from the force of the sea....
     invented by South African engineer in East London
  • 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....
  • Jetty
    Jetty

    Coastal lagoons fronted by barrier spit typically have entrances that migrate through time. Here, the entrance has been fixed by jetty variety of structures used in river, Dock , and Sea works which 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,...
  • Mole (architecture)
    Mole (architecture)

    A mole is a massive structure, usually of Rock , used as a pier, Breakwater , or junction between places separated by water.Historically, the term "mole" was used in the San Francisco Bay Area in California to refer to the combined structure of a causeway and wooden pier or trestle extending out from the eastern shore and utilized by vario...
  • Pier
    Pier

    A pier is a raised walkway over water, supported by widely spread piles or column. The lighter structure of a pier allows tides and currents to flow almost unhindered, whereas the more solid foundations of a quay or the closely-spaced piles of a wharf can act as breakwaters, and are consequently more liable to silting....
  • Port
    Port

    ||-||-|-||-||-||-||-||-||-|}A port is a facility for receiving ships and transferring cargo. They are usually found at the edge of an ocean, sea, river, or lake....
  • Xbloc
    Xbloc

    An Xbloc is an interlocking concrete block or armour unit designed to protect shores, harbour walls, seawalls, Breakwater and other coastal structures from the direct impact of incoming Ocean surface wave....
  • Tetrapod
    Tetrapod (structure)

    In coastal engineering, a Tetrapod is a four-legged concrete structure used as armour unit on breakwater s. 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 of Tetrapods to mutually interlock....
  • Accropode
  • artificial reef
    Artificial reef

    An artificial reef is a man-made, underwater structure, typically built for the purpose of promoting Marine biology#Reefs in areas of generally featureless bottom....


External links

  • Oblique Aerial Photography - Coastal Erosion from El-Niņo Winter Storms October, 1997 & April, 1998