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Coastal Erosion

 
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Coastal erosion
 
 
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Coastal erosion is the wearing away of land or the removal of 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....
 or dune
Dune

In physical geography, a dune is a hill of sand built by aeolian processes. Dunes are subject to different forms and sizes based on their interaction with the wind....
 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 by wave
Wave

A wave is a disturbance that propagates through space and time, usually with transference of energy. While a mechanical wave exists in a medium , waves of electromagnetic radiation can travel through vacuum, that is, without a medium....
 action, tidal currents
Tide

Tides are the rising of Earth's ocean surface caused by the tidal forces of the Moon and the Sun acting on the oceans. Tides cause changes in the depth of the marine and estuary water bodies and produce oscillating currents known as tidal streams, making prediction of tides important for coastal navigation ....
, wave currents, or drainage (see also beach evolution
Beach evolution

The shoreline is where the land meets the sea and it is continually changing. From a risk point of view, coastal erosion is the most widespread and continuous process....
). Waves, generated by storms, wind, or fast moving motor craft, cause coastal 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....
, which may take the form of long-term losses of sediment and rocks
Rock (geology)

In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock....
, or merely the temporary redistribution of coastal sediments; erosion in one location may result in accretion nearby.






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Coastal Erosion Hunstanton Cliffs
Coastal erosion is the wearing away of land or the removal of 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....
 or dune
Dune

In physical geography, a dune is a hill of sand built by aeolian processes. Dunes are subject to different forms and sizes based on their interaction with the wind....
 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 by wave
Wave

A wave is a disturbance that propagates through space and time, usually with transference of energy. While a mechanical wave exists in a medium , waves of electromagnetic radiation can travel through vacuum, that is, without a medium....
 action, tidal currents
Tide

Tides are the rising of Earth's ocean surface caused by the tidal forces of the Moon and the Sun acting on the oceans. Tides cause changes in the depth of the marine and estuary water bodies and produce oscillating currents known as tidal streams, making prediction of tides important for coastal navigation ....
, wave currents, or drainage (see also beach evolution
Beach evolution

The shoreline is where the land meets the sea and it is continually changing. From a risk point of view, coastal erosion is the most widespread and continuous process....
). Waves, generated by storms, wind, or fast moving motor craft, cause coastal 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....
, which may take the form of long-term losses of sediment and rocks
Rock (geology)

In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock....
, or merely the temporary redistribution of coastal sediments; erosion in one location may result in accretion nearby. The study of erosion and sediment redistribution is called 'coastal morphodynamics'. It may be caused by hydraulic action, abrasion, and corrosion.

On rocky coasts, coastal erosion results in dramatic rock formations in areas where the coastline contains rock layers or fracture zones with different resistances to erosion. Softer areas become eroded much faster than harder ones, which typically result in landforms such as tunnels, bridges, columns, and pillars.

On sedimentary coasts, coastal erosion typically poses more of a danger to human settlements than it does to nature itself. Dunwich
Dunwich

Dunwich is a small town in Suffolk, England, within the Suffolk Coast and Heaths AONB.Dunwich was the capital of Kingdom of the East Angles 1,500 years ago and was once a prosperous seaport and centre of the wool trade during the Early Middle Ages, with a natural harbour formed by the mouths of the River Blyth, Suffolk and the River Dunwic...
, the capital of the English
England

native_name =|conventional_long_name = England|common_name = England|image_flag = Flag of England.svg|image_coat = England COA.svg|symbol_type = Royal Coat of Arms...
 medieval wool
Wool

Wool is the fiber derived from the specialized skin cells, called follicles, of animals in the Caprinae family, principally domestic sheep, but the hair of certain species of other Mammalia such as cashmere goat, llamas, rabbits and keeshonds may also be called wool....
 trade, disappeared over the space of a few centuries due to redistribution of sediment by waves. Human interference can also increase coastal erosion: Hallsands in Devon
Devon

Devon is a large Counties of England in South West England. The county is also referred to as Devonshire, but that is an entirely unofficial name, rarely used inside of the county but often indicating a shire....
, England
England

native_name =|conventional_long_name = England|common_name = England|image_flag = Flag of England.svg|image_coat = England COA.svg|symbol_type = Royal Coat of Arms...
, was a coastal village that was washed away overnight, an event possibly exacerbated by dredging of shingle
Shingle

Shingle can refer to:*A flat covering element for a roof, including**Shake **Roof shingle* Shingle beach, especially in Western Europe, a beach composed of pebbles...
 in the bay in front of it.

The California coast, which has soft cliffs of sedimentary rock and is heavily populated, regularly has incidents of housing damage as cliffs erode. Damage in Pacifica
Pacifica, California

Pacifica is a city in San Mateo County, California, on the coast of the Pacific Ocean between San Francisco and Half Moon Bay, California. According to City limits signs in the year 2006, the population was 40,401....
 is shown at left. Devil's Slide
Devil's Slide

Devil's Slide is a coastal promontory in California, USA. It lies on the San Mateo County, California coast between Pacifica, California and Half Moon Bay, California at 37? 34' North, 122? 31' West....
, Santa Barbara
Santa Barbara, California

Santa Barbara is a city in Santa Barbara County, California, United States. Situated on an east-west trending section of coastline, the only such section on the west coast, between the steeply-rising Santa Ynez Mountains and the sea, and having a Mediterranean climate, it is called California's "South Coast", and is also sometimes referred to...
 and Malibu
Malibu, California

Malibu is an incorporated city in western Los Angeles County, California, United States. As of the 2000 census, the city population is 12,575....
 are regularly affected.

The Holderness
Holderness

Holderness is an area of the East Riding of Yorkshire, on the east coast of England. An area of rich agricultural land, Holderness was marshland until it was drained in the Middle Ages....
 coastline on the east coast of England, just north of the Humber Estuary, is the fastest eroding coastline in Europe due to its soft clay cliffs and powerful waves. Groynes and other artificial measure to keep it under control has only sped up the process further down the coast, because longshore drift starves the beaches of sand, leaving them more exposed.

Wave action - basic

The four main types of wave action can be remembered in this simple way; (by the use of the word "HACC")

  • Hydraulic action - occurs when waves striking the cliff face compresses air in cracks on the cliff face. This puts tremendous pressure on the surrounding rock. The air then expands explosively, forcing out pieces of rock. Over time, the cliff face crack grows, sometimes forming a cave. The rock from the cliff face which was removed falls to the bottom of the sea bed and is used for another two wave action.(Attrition and Corrasion (Abrasion)).


  • Attrition - occurs when the sea grinds rocks together, causing them to become smoother and reduced in size. As the sea rocks (scree) from side to side it moves the scree causing pieces of scree to collide with other pieces of scree thus causing them to become reduced in size, smoothed and rounded. As well as colliding with other scree, the scree also collides with the cliff face base causing pieces of rock to break off the base of the cliff face contributing to this wave action and to (Corrasion (Abrasion)).


  • Corrasion (Abrasion) - occurs when the waves break on the cliff face pounding the cliff face and slowly eroding it. As the sea pounds the cliff faces it also uses the scree from other wave actions to batter and break off pieces of rock from higher up the cliff face which can be used for this same wave action and to (Attrition).


  • Corrosion or solution - occurs when the sea's pH (anything below pH 7.0) corrodes the rocks on the cliff face. Usually the cliff faces to be greatly eroded in this manner are limestone cliff faces, which have a high pH. The rocking action of the sea also increases the rate of reaction by removing the reacted material.


Wave action - extra detail

The ability of waves
WAVES

The WAVES were a World War II-era division of the United States Navy that consisted entirely of women. The name of this group is an acronym for "Women Accepted for Volunteer Emergency Service" ; the word "emergency" implied that the acceptance of women was due to the unusual circumstances of the war and that at the end of the war the women...
 to cause 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....
 of the cliff
Cliff

In geography and geology, a cliff is a significant vertical, or near vertical, rock exposure. Cliffs are formed as erosion landforms due to the processes of erosion and weathering that produce them....
 face depends on number of factors, including:

  • The hardness or ‘erodibility’ of the rocks exposed at the base of the cliff
    • The key factors in determining erodibility include the rock
      Rock (geology)

      In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock....
       strength and the presence of fissures, fractures, and beds of non-cohesive materials such as silt
      Silt

      Silt is soil or Rock derived granular material of a Particle size between sand and clay. Silt may occur as a soil or as suspended sediment in a surface water body....
       and fine sand
      Sand

      Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.As the term is used by geologists, sand particles range in diameter from 0.0625 to 2 millimeters....
      .
  • The rate at which cliff fall debris
    Debris

    Debris is a word used to describe the remains of something that has been otherwise destroyed. Debris is pronounced with a silent s and a long e....
     is removed from the foreshore
    • Debris removal from the foreshore is dependent on the power of the waves crossing the 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....
      . This energy
      Energy

      In physics, energy is a scalar physical quantity that describes the amount of Work_ that can be performed by a force. Energy is an attribute of objects and systems that is subject to a conservation law....
       must reach a critical level or to remove material from the debris lobe. On many cliffs debris lobes can be very persistent and may take many years to completely disappear.
  • The presence/absence of a beach at the cliff base.
    • Beaches dissipate wave energy on the foreshore and can provide a measure of protection to the cliff from marine erosion.
  • The stability of the foreshore, or its resistance to lowering
    • Lowering of the beach or shore
      Shore

      A shore or shoreline is the fringe of land at the edge of a large body of water, such as an ocean, sea, or lake.Shores are influenced by the topography of the surrounding landscape, as well as by water induced erosion, such as ocean surface wave....
       platform through wave action is a key factor controlling the rate of cliff recession
      Recession

      In economics, the term recession describes the reduction of a country's gross domestic product for at least two Calendar_year#Quarters. The usual dictionary definition is "a period of reduced economic activity", a business cycle contraction....
      . If the beach is not lowered the foreshore should widen and become more effective at dissipating the wave energy, so that fewer and less powerful waves reach the cliff.
  • The adjacent bathymetry
    Bathymetry

    Bathymetry is the study of underwater depth, of the third dimension of lake or ocean floors. In other words, bathymetry is the underwater equivalent to hypsometry....
    • The nearshore bathymetry controls the wave energy arriving at the coast, and can have an important influence on the rate of cliff erosion.
  • The supply of beach material in the coastal cell from updrift
    • The provision of updrift material coming onto the foreshore beneath the cliff helps ensure a stable beach.

Factors affecting the erosion rate


Second order

  • Weathering and transport slope processes
  • Slope hydrology
  • Vegetation
  • Cliff foot erosion
  • Cliff foot sediment accumulation
  • Resistance of cliff foot sediment to attrition and transport


Third order

  • Resource extraction
  • Coastal management


See also

  • Coastal and oceanic landforms
  • Natural arch
    Natural arch

    A natural arch or natural bridge is a natural formation where a Rock arch forms, with a natural passageway through underneath. Most natural arches form as a narrow ridge, walled by cliffs, become narrower from erosion, with a softer rock stratum under the cliff-forming stratum gradually eroding out until the rock shelters thus forme...
  • Blowhole
  • Bioerosion
    Bioerosion

    Bioerosion describes the erosion of hard Substrate s – and less often terrestrial substrates – by living organisms by a number of mechanisms....
  • Modern recession of beaches
    Modern recession of beaches

    Important segments of low coasts are receding, losing sand and reducing the beaches' dimensions. This loss could occur very rapidly.From more to less natural causes :...
  • Coastal defense
    Coastal defense

    Coastal defense* Coastal Management environmental protection of coastlines* Seacoast Defense historical fortification to protect coastlines...
  • Beach nourishment
    Beach nourishment

    Beach nourishment is a complementary term that describes a process by which sediment lost through longshore drift or erosion is replaced on a beach....
  • Submersion
    Submersion (coastal management)

    Submersion is the sustainable cyclic portion of coastal erosion where coastal sediments move from the visible portion of a beach to the submerged nearshore region, and later return to the original visible portion of the beach....
  • Coastal and Estuarine Research Federation
    Coastal and Estuarine Research Federation

    The Coastal and Estuarine Research Federation is a private, nonprofit organization that was created in 1971. At that time, the members of two regionally-based organizations, the Atlantic Estuarine Research Society and the New England Estuarine Research Society recognized the need for a third estuarine organization that would address nation...
     (CERF)


External links

  • , Woods Hole Oceanographic Institution
    Woods Hole Oceanographic Institution

    The Woods Hole Oceanographic Institution is a private, nonprofit research and higher education facility dedicated to the study of all aspects of marine science and engineering and to the education of marine researchers....
  • NOAA Economics
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