Difference between revisions of "Definitions of coastal terms"

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[[Image:coastal profile.jpg|thumb|center|600px|Fig. 1. Definition of coastal terms, mainly from Shore Protection Manual, 1984.<ref>Coastal engineering Research Center, Department of the Army, Waterways Experiment Station, 1984. "Shore protection manual".</ref>]]
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[[Image:CoastalZonation.jpg|thumb|center|700px|Fig. 1. Definition of coastal sub-zones, adapted from the Shore Protection Manual, 1984<ref>Coastal engineering Research Center, Department of the Army, Waterways Experiment Station, 1984. "Shore protection manual".</ref>]]
  
  
===<div id="Accretion"> Accretion or Aggradation</div>===
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===Accretion or Aggradation===
Growth (vertical and/or horizontal) of morphological features ([[#Beach|beach]], [[#Bar|bar]], [[#Dune|dune]], [[#Sand bank|sand bank]], [[#Tidal flat|tidal flat]], [[#Salt marsh|salt marsh]], [[#Tidal channel|tidal channel]], etc.) by sedimentation.
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Growth (vertical and/or horizontal) of morphological structures ([[#Beach|beach]], [[#Bar|bar]], [[#Dune|dune]], [[#Sand bank|sand bank]], [[#Tidal flat|tidal flat]], [[#Salt marsh|salt marsh]], [[#Tidal channel|tidal channel]], etc.) by sedimentation.
===<div id="Active coastal zone"> Active coastal zone</div>===
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===Active coastal zone===
The [[active coastal zone]] (also called '''active coastal profile''') is the cross-shore coastal zone that is highly dynamic by the action of tides, [[#Wave|waves]] and wind. It extends from the [[#Closure depth|closure depth]] up to a fixed land boundary (rock, cliff, seawall, sea dike). In the case of a dune coast the front [[#Dunes|dune]] is part of the active coastal zone. See: [[Active coastal zone]].   
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The [[active coastal zone]] (also called '''active coastal profile''') is the cross-shore coastal zone that is highly dynamic, with up and down redistribution of sand by the action of tides, [[#Wave|waves]] and wind. It extends from the [[#Closure depth|closure depth]] up to a fixed land boundary (rock, cliff, seawall, sea dike). In the case of a dune coast the front [[#Dunes|dune]] is part of the active coastal zone. See: [[Active coastal zone]].   
===<div id="Angle of incidence"> Angle of incidence </div>===  
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===Angle of incidence===  
The angle between the wave propagation direction and the normal to the coastline or the angle between the wave front and the coastline (often denoted <math>\alpha</math>). When [[#Wave|waves]]  enter shallow water, the wave propagation direction tends to become perpendicular to the depth contours, by [[#Refraction|refraction]].  See: [[Shallow-water wave theory]], [[Wave transformation]]. The [[#Deep water|deep water]] angle of incidence is often denoted <math>\alpha_0</math>.
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The angle between the wave propagation direction and the normal to the coastline or the angle between the wave front and the coastline (often denoted by the symbol <math>\alpha</math> or <math>\theta</math>). When [[#Wave|waves]]  enter shallow water, the wave propagation direction tends to become perpendicular to the depth contours, by [[#Refraction|refraction]].  See: [[Shallow-water wave theory]], [[Wave transformation]]. The [[#Deep water|deep water]] angle of incidence is often denoted <math>\alpha_0</math>.
===<div id="Armouring"> Armouring </div>===  
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===Armouring===  
 
# Manmade structures such as seawalls, revetments, bulkheads, geotubes, etc. intended to prevent damage of properties situated on the coast;
 
# Manmade structures such as seawalls, revetments, bulkheads, geotubes, etc. intended to prevent damage of properties situated on the coast;
 
# The natural process of removing fine sediment from the beach or seabed top layer, leaving coarse material behind, thus leading to a more erosion-resistant residual top layer. This process may occur at places where beach or seabed material is a mixture of fine and coarse sediments (so-called '''graded sediment''').
 
# The natural process of removing fine sediment from the beach or seabed top layer, leaving coarse material behind, thus leading to a more erosion-resistant residual top layer. This process may occur at places where beach or seabed material is a mixture of fine and coarse sediments (so-called '''graded sediment''').
===<div id="Avulsion"> Avulsion</div>===  
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===Astronomical tide===
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The tidal levels and water motion which would result from Earth's rotation and gravitational effects of, in particular, the Earth, Sun and Moon, without any atmospheric influences. See also: [[#Tide|Tide]]
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===Avulsion===  
 
The sudden abandonment of an existing [[#Tidal channel|tidal channel]] in favour of a newly formed channel. Channel avulsion is a common process in tidal [[#Delta|deltas]].
 
The sudden abandonment of an existing [[#Tidal channel|tidal channel]] in favour of a newly formed channel. Channel avulsion is a common process in tidal [[#Delta|deltas]].
===<div id="Backshore">Backshore</div>===
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===Backshore===
The part of the beach lying between the [[#Foreshore or Beach face|foreshore]] and coastline. The backshore is dry under normal conditions; it is generally without vegetation and often characterised by berms. The backshore is only exposed to [[#Wave|waves]]  under extreme events with high tide and [[#Storm surge|storm surge]].   
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The part of the beach lying between the [[#Beach face|beach face]] and coastline. The backshore is dry under normal conditions; it is often characterised by berms. [[Shore protection vegetation|Vegetation]] is generally sparse or absent. The backshore is only exposed to [[#Wave|waves]]  under extreme events with high tide and [[#Storm surge|storm surge]].   
===<div id="Bar"> Bar</div>===
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===Bar===
Elongated sand body created by (tidal) currents or by [[#Wave|waves]] . Bars in [[#Estuary|estuaries]] and [[#Lagoon|tidal lagoons]] develop naturally in flow convergence zones, often in relation with channel [[#Meandering|meandering]]. Estuarine bars also occur where ebb- and flood-dominated [[#Tidal channel|channels]] meet. Bars that partially block the openings to minor streams and lagoons are mainly due to [[#Littoral drift|littoral drift]]; these bars are generally referred to as [[#Spit|spits]]. Wave action is responsible for the development of [[#Breaker bar|breaker bars]], [[#Beach berm|beach berms and swash bars]]. Bars can raise above the high water level, but they are often intratidal or subtidal.  
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Elongated sand body created by (tidal) currents or by [[#Wave|waves]] . Bars in [[#Estuary|estuaries]] and [[#Lagoon|tidal lagoons]] develop naturally in flow convergence zones, often in relation with channel [[#Meandering|meandering]]. Estuarine bars also occur where ebb- and flood-dominated [[#Tidal channel|channels]] meet. Bars that partially block the openings to minor streams and lagoons are mainly due to [[#Littoral drift|littoral drift]]; these bars are generally referred to as [[#Spit|spits]]. Wave action is responsible for the development of [[Nearshore sandbars|breaker bars]], [[#Beach berm|beach berms and swash bars]]. Bars can raise above the high water level, but they are often intratidal or subtidal.  
===<div id="Bathymetry"> Bathymetry</div>===
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===Bathymetry===
Mapping of the seafloor depth with respect to the mean water level. The term is also used for the description of seafloor topography or [[#Coastal morphology|coastal morphology]].   
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Mapping of the seafloor depth with respect to the mean water level. The term is also used for the description of seafloor topography or [[#Coastal morphology|coastal morphology]].  The depths are almost always derived indirectly by measuring the time required for a signal to travel from a transmitter, to the bottom, and back to a receiver.
===<div id="Beach"> Beach or Shore </div>===
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===Beach===
The zone of unconsolidated material that extends from the mean low water line to the place where there is a marked change in material or physiographic form (e.g. dunefoot), or to the line of permanent vegetation (the effective limit of storm [[#Wave|waves]]  and storm surge), i.e. to the [[#Coastline|coastline]]. The beach or shore can be divided in the [[#Foreshore or Beach face|foreshore]] and the [[#Backshore|backshore]]. Often a distinction is made between [[#Dissipative and reflective beaches|dissipative and reflective beaches]].  
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The beach (or '''shore''') zone of unconsolidated material that extends from the mean low water line to the place where there is a marked change in material or physiographic form (e.g. [[#Dunefoot|dunefoot]]), or to the line of permanent [[Shore protection vegetation|vegetation]] (the effective limit of storm [[#Wave|waves]]  and storm surge), i.e. to the [[#Coastline|coastline]]. The beach or shore can be divided in the [[#Beach face|beach face]] and the [[#Backshore|backshore]]. Often a distinction is made between [[#Dissipative and reflective beaches|dissipative and reflective beaches]].  
===<div id="Beach berm"> Beach berms and swash bars </div>===
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===[[Beach berm]]===
A beach berm (or beach ridge) is a nearly horizontal shore parallel ridge formed on the beach due to the landward transport of the coarsest fraction of the beach material by the [[#Swash|wave uprush]]. There may be several beach berms and in some cases no berms. Under normal conditions a beach berm is formed on the upper part of the [[#Foreshore or Beach face|foreshore]], and over the [[#Backshore|backshore]] during severe events.  
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A beach berm is a nearly horizontal shore parallel ridge formed on the beach due to the landward transport of the coarsest fraction of the beach material by the [[#Swash|wave uprush]]. There may be several beach berms and in some cases no berms. Under normal conditions a beach berm is formed on the upper part of the [[#Beach face|beach face]], and over the [[#Backshore|backshore]] during severe events.  
 
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Berms can also form on the higher intertidal zone of a [[#Tidal flat|tidal flat]]; these berms are generally called "swash bars".  
Berms can also form on the higher intertidal zone of a beach or a [[#Tidal flat|tidal flat]]; these berms are generally called "swash bars". They may be related to onshore moving [[#Breaker bar|breaker bars]].  
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Beach berms are sometimes artificially reinforced as coastal protection measure.  
===<div id="Beach cusps"> Beach cusps </div>===
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===[[Beach Cusps|Beach cusps]]===
 
Regularly spaced shoreline structures (spacing typically between a few meters and a few tens of meters) consisting of small embayments between protruding horns. They are a common feature of [[#Dissipative and reflective beaches|reflective beaches]]. See: [[Beach Cusps]].
 
Regularly spaced shoreline structures (spacing typically between a few meters and a few tens of meters) consisting of small embayments between protruding horns. They are a common feature of [[#Dissipative and reflective beaches|reflective beaches]]. See: [[Beach Cusps]].
===<div id="Beach fill"> Beach fill</div>===
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===[[Beach face]]===  
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Beach face (also called '''foreshore''') is the zone between the mean low water (MLW) and the seaward [[#Beach berm|beach berm]], which is equivalent to the upper limit of [[#Wave run-up|wave run-up]] at high tide, see Fig. 1. The beach face is the part of the [[#Beach|shore/beach]] which is wetted due to the varying tide and [[#Swash|swash]] under normal conditions. This means that the beach face in morphological terms extends further up on the beach than the intersection between the mean high water (MHW) and the coastal profile (MHW line). However, for practical reasons the upper delineation of the beach face is often defined as the intersection between the MHW line and the coastal profile, which is identical to the usual definition of the [[#Shoreline|shoreline]]. On the lower part of wide intertidal beaches several intertidal bars (also called beach ridges) can be present, related to onshore moving [[nearshore sandbars]]. The depressions between these intertidal bars are called [[runnel]]s. 
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===Beach fill===
 
The supply of beach sand for the construction of an artificial beach.
 
The supply of beach sand for the construction of an artificial beach.
===<div id="Beach park"> Beach park </div>===
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===Beach nourishment===
A beach park is a scheme which consists of new artificial beaches, stabilising coastal structures and filling/reclamation, which in combination provides new recreational facilities. Artificial beaches will be exposed to wave action and will evolve to a stable plan and profile shape.
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Beach nourishment is the supply of sand to the beach to increase the recreational value and/or to compensate for the effect of shore erosion by feeding sand on the beach.
===<div id="Bed forms"> Bed forms</div>===
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===Bed forms===
 
The seafloor is seldom flat, but generally undulated by the interaction with currents and [[#Wave|waves]] . Undulated bedforms exist over a large range of spatial scales, from centimeters up to kilometers, see: [[Wave ripples]], [[Wave ripple formation]], [[Sand ridges in shelf seas]], [[Stability models]]. The smallest bedforms play an important role in the friction exerted by the seabed on water motion, see [[#Boundary layer|Boundary layer]], [[Bedforms and roughness]], [[Bed roughness and friction factors in estuaries]], [[Wave ripples]], [[Wave ripple formation]].  
 
The seafloor is seldom flat, but generally undulated by the interaction with currents and [[#Wave|waves]] . Undulated bedforms exist over a large range of spatial scales, from centimeters up to kilometers, see: [[Wave ripples]], [[Wave ripple formation]], [[Sand ridges in shelf seas]], [[Stability models]]. The smallest bedforms play an important role in the friction exerted by the seabed on water motion, see [[#Boundary layer|Boundary layer]], [[Bedforms and roughness]], [[Bed roughness and friction factors in estuaries]], [[Wave ripples]], [[Wave ripple formation]].  
===<div id="Benthos">Benthos</div>===
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===Bedload===
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Bedload transport refers to sediment transport by rolling and saltating sediment grains over the seabed. Bedload transport is the dominant sediment transport mode when the flow velocities (currents and wave-orbital velocities) are above the critical velocity for setting bed particles in motion (in the order of 0.2-0.4 m/s for sandy sediments), but insufficient for bringing sediment particles in suspension. Bedload transport occurs for non-cohesive medium-coarse sediments and is associated with the formation of bed ripples and dunes. The migration of these bedforms yields an estimate for the bedload  transport. See: [[Sand transport]].
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===Benthos===
 
Organisms living on or in the seabed, including vegetation.
 
Organisms living on or in the seabed, including vegetation.
===<div id="Boundary layer">Boundary layer (turbulent) and momentum dissipation</div>===
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===Boundary layer (turbulent)===
The fluid layer where momentum and energy are dissipated as a result of friction exerted by the seafloor or a nearby hard boundary. In the boundary layer, momentum is transferred from the large-scale flow pattern in a cascade process to increasingly smaller [[#Turbulence|turbulent]] flow structures. The large-scale flow profile in the turbulent boundary layer has a logarithmic profile. The thickness of the turbulent boundary layer corresponds to the size of the largest turbulent eddies generated by friction at the seafloor. Because the development of the turbulent boundary layer takes time, the boundary layer thickness for slowly varying currents is much greater than for rapidly varying currents. The boundary layer thickness for steady flow and tidal flow is typically of the order of 10-50% of the water depth, whereas the boundary layer thickness for wind-driven [[#Wave|waves]]  is only a few centimeters. Hence, steady flow and tidal flow experience much stronger friction than propagating wind-driven waves. See: [[#Bed forms|Bed forms]], [[Wave ripples]].
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The fluid layer where momentum and energy are dissipated as a result of friction exerted by the seafloor or a nearby hard boundary. In the boundary layer, fluid momentum is dissipated through transfer from the large-scale flow pattern in a cascade process to increasingly smaller [[#Turbulence|turbulent]] flow structures. The large-scale flow profile in the turbulent boundary layer has a logarithmic profile. The thickness of the turbulent boundary layer corresponds to the size of the largest turbulent eddies generated by friction at the seafloor. Because the development of the turbulent boundary layer takes time, the boundary layer thickness for slowly varying currents is much greater than for rapidly varying currents. The boundary layer thickness for steady flow and tidal flow is typically of the order of 10-50% of the water depth, whereas the boundary layer thickness for wind-driven [[#Wave|waves]]  is only a few centimeters. Hence, steady flow and tidal flow experience much stronger friction than propagating wind-driven waves. See: [[#Bed forms|Bed forms]], [[Wave ripples]].
===<div id="Breaker zone">Breaker zone or Surf zone</div>===
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===Breaker zone===
The zone extending seaward from the shoreline that is exposed to depth-limited [[#Wave breaking|breaking waves]]. The outer limit of the breaker zone (or surf zone) is called the '''breaker line'''. However, the instantaneous width of the breaker zone varies with the instantaneous wave conditions and water level. In the general context, the surf zone width is defined in relation to the yearly wave climate defined by the significant wave height <math>H_{s,12h/y}</math>, which is the [[#Wave height|wave height]] exceeded 12 hours per year. The surf zone thus corresponds to the zone where waves of height <math>H_{s,12h/y}</math> break. The surf zone is somewhat narrower than the [[#Shoreface|littoral zone]]. It is estimated that 80 to 90% of the yearly littoral transport takes place within the breaker or surf zone.
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See [[#Surf zone|surf zone]].
===<div id="Breaker bar">Breaker bar</div>===
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===Breaker bar===
A submerged shore parallel embankment of sand or gravel built in the [[#Breaker zone|breaker zone]] due to the action of [[#Wave breaking|breaking waves]] and cross-currents. There can be several rows of bars. Breaker bars are very mobile formations, which tend to be in unstable equilibrium with actual wave and tide conditions, which means that they are constantly changing. The overall tendency is that the bars are moving seawards during storm wave conditions and landwards during conditions dominated by smaller [[#Wave|waves and swell]]. At intervals there are gaps in the breaker bars formed by [[#Rip currents|rip currents]].   
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Breaker bars, also called [[nearshore sandbars]], are elongated (approximately) shore parallel bodies of sand or gravel built in the [[#Surf zone|surf zone]] due to the action of [[#Wave breaking|breaking waves]] and cross-currents. There can be several rows of bars. Breaker bars are very mobile formations, which tend to be in unstable equilibrium with the wave climate and tide conditions, which means that they are constantly changing. The overall tendency is that the bars are moving seawards during storm wave conditions and landwards during conditions dominated by smaller [[#Wave|waves and swell]]. At intervals there are gaps in the breaker bars formed by [[#Rip currents|rip currents]].  See [[Nearshore sandbars]].
===<div id="Breakwater"> Breakwater</div>===
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===[[Breaker index]]===
A structure built for reducing wave activity in the waters at the leeside. It can be linked to the shore or it can be positioned offshore. A common type is the '''detached breakwater'''. This is a structure approximately parallel to the coast, built inside or outside the surf zone. The main purpose of detached breakwaters is either to protect a harbor entrance or a ship wharf from wave action or to reduce wave activity at the beach. See: [[Application of breakwaters]], [[Detached breakwaters]], [[Detached shore parallel breakwaters]], [[Floating breakwaters]].
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The ratio of wave height and still water depth at the shoreface location where incident waves start breaking. See [[Breaker index]].
===<div id="Buoyancy"> Buoyancy</div>===
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===Breakwater===
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A structure built for reducing wave activity in the waters at the leeside. It can be linked to the shore or it can be positioned offshore. A common type is the '''detached breakwater'''. This is a structure approximately parallel to the coast, built inside or outside the surf zone. The main purpose of detached breakwaters is either to protect a harbor entrance or a ship wharf from wave action or to reduce wave activity at the beach. See: [[Application of breakwaters]], [[Detached breakwaters]], [[Detached shore parallel breakwaters]], [[Floating breakwaters]], [[Stability of rubble mound breakwaters and shore revetments]].
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===Buoyancy===
 
Upward force experienced by a body of lower density (water body of lower salinity, higher temperature, for example) than the surrounding fluid.   
 
Upward force experienced by a body of lower density (water body of lower salinity, higher temperature, for example) than the surrounding fluid.   
===<div id="Chenier"> Chenier</div>===
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===Chenier===
An accretionary feature consisting of a long, low lying, narrow strip of gravely sand (typically up to 3 m high and 40 to 400 m wide), often shelly, deposited in the form of wave-built beach ridge on a swampy, deltaic, or alluvial coastal plain of fine sediment.
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An accretionary feature consisting of a long, low lying, narrow strip of (gravelly) sand, typically up to 3 m high and 40 to 400 m wide, often shelly, deposited in the form of wave-built beach ridge on a swampy, deltaic, or alluvial coastal plain of fine sediment.
===<div id="Closure depth"> Closure depth </div>===
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===Closure depth===
The depth beyond which no significant longshore or cross-shore transports take place due to littoral transport processes. The closure depth can thus be defined as the depth at the seaward boundary of the [[#Shoreface|littoral zone]], see: [[Closure depth]].  
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There are two closure depths: (1) the depth <math>h_{out}</math> at the seaward limit of the lower shoreface, beyond which no significant wave-induced sand transport takes place; (2) the depth <math>h_{in}</math> marking the transition between the lower shoreface (wave [[#Shoaling|shoaling]] zone) and upper shoreface (wave breaking zone). See [[Closure depth]], [[#Shoreface|shoreface]] and [[Shoreface profile]].  
===<div id="Coast"> Coast </div>===
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===Coast===
The strip of land that extends from the coastline inland to the first major change in the terrain features, which are not influenced by the coastal processes. The main types of coastal features are dunes, cliffs and low-lying areas, possibly protected by dikes or seawalls.  
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The strip of land that extends from the coastline inland to the first major change in the terrain features, which are not influenced by coastal processes. The main types of coastal features are dunes, cliffs and low-lying areas, possibly protected by dikes or seawalls.  
===<div id="Coastal area"> Coastal area</div>===
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===Coastal area===
 
The land and sea areas bordering the shoreline.
 
The land and sea areas bordering the shoreline.
===<div id="Coastal cell"> Coastal cell</div>===
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===Coastal cell===  
See [[#Sediment cell|sediment cell]].
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A coastal cell (or '''littoral cell''' or '''sediment cell''') is a coastal compartment that contains a closed cycle of sedimentation including sources, transport paths, and sinks. The cell boundaries (often corresponding to headlands or jetties) delineate the geographical area within which the budget of sediment is balanced, providing the framework for the quantitative analysis of coastal erosion and accretion.
===<div id="Coastal development"> Coastal development</div>===
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===Coastal development===
 
Any activity likely to alter the physical nature of the [[#Coastal zone|coastal zone]] in any way, including construction of buildings and works, the deposit of waste or other material from outfalls, vessels or by other means, the removal of sand, sea shells, natural vegetation, sea grass and other substances, dredging and filling, land reclamation and mining or drilling for minerals, but excluding fishing activities.
 
Any activity likely to alter the physical nature of the [[#Coastal zone|coastal zone]] in any way, including construction of buildings and works, the deposit of waste or other material from outfalls, vessels or by other means, the removal of sand, sea shells, natural vegetation, sea grass and other substances, dredging and filling, land reclamation and mining or drilling for minerals, but excluding fishing activities.
===<div id="Coastal erosion"> Coastal erosion</div>===
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===Coastal erosion===
Distinction must be made between incidental coastal erosion and ongoing coastal erosion.  
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Coast erosion is the process of wearing away material from the coastal profile due to imbalance in the supply and export of material from a certain section. Distinction must be made between incidental coastal erosion and ongoing coastal erosion.  
*'''Incidental coastal erosion''' (also called '''temporal coastal erosion''') takes place mainly by cross-shore processes during extreme events (high water levels, high waves), which produce beach lowering or scouring in the foot of the cliffs or in the foot of the dunes (see [[#Wave run-up|wave run-up]] and [[dune erosion]]). For stable coasts, incidental erosion is a reversible process; under average conditions the coastal profile is restored - see: [[Natural causes of coastal erosion]] and [[Active coastal zone]].
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*'''Incidental coastal erosion''' (also called '''temporal coastal erosion''') takes place mainly by cross-shore processes during extreme events (high water levels, high waves), which produce beach lowering or scouring in the foot of the cliffs or in the foot of the dunes (see [[#Wave run-up|wave run-up]] and [[dune erosion]]). For stable coasts, incidental erosion is a reversible process; under average conditions the coastal profile is restored - see: [[Dealing with coastal erosion]], [[Natural causes of coastal erosion]] and [[Active coastal zone]].
*'''Ongoing coastal erosion''' (also called '''structural coastal erosion''' or '''long-term coastal erosion''') is mainly due to a structural imbalance in the supply and export of material from a certain coastal section. Erosion takes place on the [[#Shoreface|shoreface]] and on the beach if the export is greater than the supply of material. The deficit can be due to both cross-shore processes and [[#Littoral drift|longshore processes]]. The main reason for a long-term erosional trend is often a deficit in the littoral drift budget, caused by a down-drift increase of [[#Littoral drift|longshore sediment transport]], see: [[Long-term modelling using 1-line models - GENESIS and new extensions]]. The rate of erosion is expressed in volume/length/time, e.g. in m<sup>3</sup>/m/year, but erosion rate is often used synonymously with coastline retreat, and thus expressed in m/year. See:  [[Natural causes of coastal erosion]], [[Human causes of coastal erosion]], [[Types and background of coastal erosion]], [[Accretion and erosion for different coastal types]], [[Typical examples of structural erosion]], [[Dune erosion]].
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*'''Ongoing coastal erosion''' (also called '''structural coastal erosion''' or '''long-term coastal erosion''') is mainly due to a structural imbalance in the supply and export of material from a certain coastal section. Erosion takes place on the [[#Shoreface|shoreface]] and on the beach if the loss of sediment is greater than the supply. The deficit can be due to both cross-shore processes and [[#Littoral drift|longshore processes]]. The main reason for a long-term erosional trend is often a deficit in the littoral drift budget, caused by a down-drift increase of [[#Littoral drift|longshore sediment transport]], see: [[Littoral drift and shoreline modelling]]. The rate of erosion is expressed in volume/length/time, e.g. in m<sup>3</sup>/m/year, but erosion rate is often used synonymously with coastline retreat, and thus expressed in m/year. See:  [[Natural causes of coastal erosion]], [[Human causes of coastal erosion]], [[Accretion and erosion for different coastal types]], [[Typical examples of structural erosion]], [[Dune erosion]].
===<div id="Coastal hinterland"> Coastal hinterland</div>===
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===Coastal hinterland===
 
The land that extends landward of the coast and which is not influenced by coastal processes.
 
The land that extends landward of the coast and which is not influenced by coastal processes.
===<div id="Coastal morphology"> Coastal morphology</div>===
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===Coastal morphodynamics===
Coastal morphology or coastal geomorphology is the science of natural morphodynamic processes, which are responsible for shaping the [[#Coastal zone|coastal zone]]. The meaning of the Greek word "morphè" is form or shape. These natural processes, which involve wind, tides, currents, waves, biota, [[#Sea-level rise|soil and sea-level changes]], interact with the materials from which the coastal zone is built. Coastal zones around the world are shaped in highly diverse ways. The term coastal morphology is also used for the description of these very diverse coastal forms. See also: [[Coastal zone characteristics]], [[Classification of coastlines]], [[Classification of coastal profiles]].
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The mutual interaction of [[coastal morphology]] with hydrodynamic agents (tides, currents, waves). This interaction takes place through [[sedimentation]], [[erosion]] and [[sediment transport]] processes. [[Tide]]s, [[currents]] and [[waves]] adapt to constraints imposed by the morphology of a coastal system (e.g., [[Definitions of coastal terms#Delta|delta]], [[estuary]], [[beach]], etc.). The [[Coastal morphology|morphology]] of a coastal system adapts to the tides, currents, waves to which it is exposed. This mutual adaptation, which is always highly nonlinear, generates morphological patterns, such as [[Definitions of coastal terms#Meandering|channel meanders]], [[tidal flat]]s, [[Definitions of coastal terms#Delta|ebb tidal deltas]], [[nearshore sandbars]], [[beach berm]]s, [[Sand ridges in shelf seas|sand ridges]], [[Wave ripples|ripples]], etc. As a result, the large-scale coastal morphology develops into a slowly evolving morphodynamic equilibrium state in which smaller morphological patterns evolve in a quasi-cyclical (usually non-deterministic) manner at much smaller timescales.
===<div id="Coastal profile"> Coastal profile</div>===
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===Coastal morphology===
The cross-shore profile of the [[#Active coastal zone|active coastal zone]]. See also: [[Parametric equilibrium models]].
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Coastal morphology (or '''coastal geomorphology''' or '''morphology''') is the (study of the) shape and structure of coastal systems or subsystems. For example: the morphology of a delta, the morphology of an estuary, the morphology of a beach, the morphology of a bedform. The meaning of the Greek word "morphè" is form or shape.
===<div id="Coastal protection"> Coastal protection</div>===
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See also: [[Characteristics of sedimentary shores]], [[Classification of sandy coastlines]], [[Morphology of estuaries]].
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===Coastal profile===
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The cross-shore profile of the [[#Active coastal zone|active coastal zone]]. See also: [[Shoreface profile]].
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===Coastal protection===
 
Three different protection/defence definitions are used as follows:
 
Three different protection/defence definitions are used as follows:
*'''Coastal protection''': Measures aimed at protecting the coast against coastline retreat, thus protecting settlements, infrastructure, the [[#Coast|coast]] and the [[#Coastal hinterland|hinterland]] from erosion often at the expense of losing the beach and the dynamic coastal landscape. Coastal protection often consists of hard structures such as revetments, [[#Breakwater|breakwaters]] or [[#Groyne|groynes]], see also:  [[Protection against coastal erosion]], [[Hard structures and structural erosion]], [[Hard shoreline protection structures]], [[Seawalls and revetments]].
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*'''Coastal protection''': Measures aimed at protecting the coast against coastline retreat, thus protecting settlements, infrastructure, the [[#Coast|coast]] and the [[#Coastal hinterland|hinterland]] from erosion often at the expense of losing the beach and the dynamic coastal landscape. Coastal protection often consists of hard structures such as revetments, [[#Breakwater|breakwaters]] or [[#Groyne|groynes]], see also:  [[Hard coastal protection structures]], [[Seawalls and revetments]].
 
*'''Sea defence''': Measures aiming at protecting low-lying coast and coastal hinterland against flooding caused by the combined effect of storm surge and high astronomical tides. Sea defence often consists of dikes or seawalls of some kind, or artificial [[Dunes|dunes]], see: [[Overtopping resistant dikes]].
 
*'''Sea defence''': Measures aiming at protecting low-lying coast and coastal hinterland against flooding caused by the combined effect of storm surge and high astronomical tides. Sea defence often consists of dikes or seawalls of some kind, or artificial [[Dunes|dunes]], see: [[Overtopping resistant dikes]].
*'''Shore protection''': Measures aiming at protecting, preserving or restoring the shore and the dynamic coastal landscape as well as protecting against coastline retreat to the extent possible. See: [[Soft shoreline protection solutions]], [[Artificial reefs]], [[Natural barriers]], [[Dynamics, threats and management of biogenic reefs]], [[Sand-filled geosystems in coastal engineering]], [[Beach nourishment]], [[Artificial nourishment]], [[Shore nourishment]], [[Beach drainage]], [[Dynamics, threats and management of dunes]].
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*'''Shore protection''': Measures aiming at protecting, preserving or restoring the shore and the dynamic coastal landscape as well as protecting against coastline retreat to the extent possible. See: [[Artificial reefs]], [[Natural shore protecting barriers]], [[Dynamics, threats and management of biogenic reefs]], [[Sand-filled geosystems in coastal engineering]], [[Beach nourishment]], [[Artificial nourishment]], [[Shore nourishment]], [[Beach drainage]], [[Dynamics, threats and management of dunes]].
===<div id="Coastal zone"> Coastal zone</div>===
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===Coastal zone===
General, wide planning-oriented characterisation: The interface between land and sea, delineated as the part of the land affected by its proximity to the sea, and the part of the sea affected by its proximity to the land. See also: [[Coastal zone delimitation]].  
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General, wide planning-oriented characterisation: The interface between land and sea, defined as the part of the land affected by its proximity to the sea (influence of marine processes), and the part of the sea affected by its proximity to the land (influence of terrestrial processes).  
===<div id="Coastal zone management (CZM)"> Coastal zone management (CZM)</div>===
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===Coastal zone management (CZM)===
The aim of coastal zone management is to balance the different interests of coastal areas, which are related to: safety, environment, economy, human activities and esthetic and cultural values, see also: [[Some definitions of Integrated Coastal Zone Management (ICZM)]]. Because of this comprehensive scope the term '''Integrated coastal zone management (ICZM)''' is more widely used than CZM. The dynamic nature of the coastal zone is a highly challenging aspect of coastal zone management. Coastal engineering (hard or soft measures) and coastal area planning are major instruments for coastal zone management. See: [[The Integrated approach to Coastal Zone Management (ICZM)]], [[Spatial Planning and Integrated Coastal Zone Management]], [[Policy instruments for integrated coastal zone management]].
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Coastal zone management is the process aiming to balance the different interests in coastal areas, related to safety, environment, economy, social equity and esthetic and cultural values.
===<div id="Coastline"> Coastline</div>===
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Coastal area planning and coastal engineering (hard or soft measures) are major components of coastal zone management, together with legislation, administration, communication, education, monitoring, research. Because of this comprehensive scope the term '''Integrated coastal zone management (ICZM)''' is more widely used than CZM. The dynamic nature of the coastal zone is a highly challenging aspect of coastal zone management. See also:
Technically the line that forms the boundary between the [[#Coast|coast]] and the [[#Beach|shore]], i.e. the foot of the cliff or the foot of the dunes. Commonly, the line that forms the boundary between the land and the water. See also: [[Classification of coastlines]].
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[[Integrated Coastal Zone Management (ICZM)]],
===<div id="Coastline retreat"> Coastline retreat</div>===
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[[Some definitions of Integrated Coastal Zone Management (ICZM)]],
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[[The Integrated approach to Coastal Zone Management (ICZM)]],
 +
[[Spatial Planning and Integrated Coastal Zone Management]],
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[[Policy instruments for integrated coastal zone management]],
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[[Shoreline management]],
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and other articles in the category [[:Category:Integrated coastal zone management|Integrated coastal zone management]]
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===[[Coastline]]===
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The boundary between land and sea, a proxy of the instantaneous [[shoreline]] for the assessment of erosion or accretion trends. See: [[Coastline]].
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===Coastline retreat===
 
Landward shift of the coastline caused by a long-term erosional trend or by sea-level rise.
 
Landward shift of the coastline caused by a long-term erosional trend or by sea-level rise.
===<div id="Continental shelf"> Continental shelf or Shelf sea</div>===
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===Continental shelf===
Part of a continent that is submerged in relatively shallow sea (water depths typically less than 200 m). The continental shelf extends from the coastline of a continent to a drop-off point called the shelf break. From the break, the shelf descends toward the deep ocean floor in what is called the continental slope. Water motion, water quality and ecosystem of shelf seas are strongly influenced by the adjacent ocean, see [[Shelf sea exchange with the ocean]].  
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The continental shelf (or '''shelf sea''') is the continental border which is submerged in relatively shallow sea (water depths typically less than 200 m). The continental shelf extends from the coastline of a continent to a drop-off point called the shelf break. From the break, the shelf descends toward the deep ocean floor in what is called the continental slope. Water motion, water quality and ecosystem of shelf seas are strongly influenced by the adjacent ocean, see [[Shelf sea exchange with the ocean]], [[Continental shelf habitat]].
  
The legal definition of a continental shelf is different than the geographic one. According to the UN Convention on the Law of the Sea, every nation has a continental shelf extending no more than 200 nautical miles from the nation's coastline. See: [[Legislation for the sea]].  
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The legal definition of a continental shelf is different from the geographic one. According to the UN Convention on the Law of the Sea, every nation has a continental shelf extending no more than 200 nautical miles from the nation's coastline. See: [[Legislation for the sea]].  
===<div id="Coriolis"> Coriolis</div>===
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===Coriolis===
 
The acceleration experienced by a current due to earth rotation, see: [[Coriolis acceleration]].
 
The acceleration experienced by a current due to earth rotation, see: [[Coriolis acceleration]].
===<div id="Creek"> Creek</div>===
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===Deep water===
A [[#Tidal channel|tidal channel]] that drains a [[#Salt marsh|salt marsh]].
 
===<div id="Deep water"> Deep water</div>===
 
 
Water too deep for [[#Wave|waves]]  to be affected by the seafloor; typically taken as half the wavelength, or greater.
 
Water too deep for [[#Wave|waves]]  to be affected by the seafloor; typically taken as half the wavelength, or greater.
===<div id="Delta"> Delta</div>===
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===[[Deltas|Delta]]===
The fan-shaped mouth of a river or a tidal basin, formed by several distributary channels. They are the result of depositional and erosional processes under the influence of currents, waves and tides. Because of their different morphologies, often a distinction is made between river-dominated deltas, wave-dominated deltas and tide-dominated deltas. See: [[Morphology of estuaries]], [[Wave-dominated river deltas]].  
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The fan-shaped mouth of a river or a tidal basin, formed by several distributary channels. River deltas are formed when the supply of sediments to the coast by a river is faster than they are dispersed by waves, tides and the associated currents. They are the result of depositional and erosional processes under the influence of currents, waves and tides. Because of their different morphologies, often a distinction is made between river-dominated deltas, wave-dominated deltas and tide-dominated deltas. See: [[Morphology of estuaries]], [[Wave-dominated river deltas]].  
  
'''Flood deltas''' are sedimentary bodies deposited by flood currents. '''Ebb-tidal deltas''' are sedimentary bodies deposited by ebb currents. Flood deltas and ebb-tidal deltas are generally present at the inshore and offshore sides (respectively) of [[#Tidal inlet|tidal inlets]] of [[#Estuary|estuaries]] and [[#Lagoon|tidal lagoons]].    
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'''Flood tidal deltas''' are sedimentary bodies deposited by flood currents. '''Ebb-tidal deltas''' are sedimentary bodies deposited by ebb currents. Flood deltas and ebb-tidal deltas are generally present at the inshore and offshore sides (respectively) of [[#Tidal inlet|tidal inlets]] of [[#Estuary|estuaries]] and [[#Lagoon|tidal lagoons]].  
===<div id="Dispersion"> Dispersion</div>===
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===[[Diffraction]]===
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Process by which energy of a wave is transmitted, radiated and dissipated laterally when reaching an obstacle such a breakwater and propagates into its sheltered region. 
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===Dispersion===
 
#The passive dispersal of dissolved substances in the marine or estuarine environment. Dispersion is the overall mixing effect of all hydrodynamic processes including turbulence, flow circulations and gradients in current velocity. See: [[Seawater intrusion and mixing in estuaries]], [[Transport and dispersion of pollutants, nutrients, tracers in mixed nearshore water]], [[Shelf sea exchange with the ocean]].
 
#The passive dispersal of dissolved substances in the marine or estuarine environment. Dispersion is the overall mixing effect of all hydrodynamic processes including turbulence, flow circulations and gradients in current velocity. See: [[Seawater intrusion and mixing in estuaries]], [[Transport and dispersion of pollutants, nutrients, tracers in mixed nearshore water]], [[Shelf sea exchange with the ocean]].
# Wave field transformation due to the dependence of propagation speed on wave frequency.
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# Wave field transformation due to the dependence of propagation speed on wave frequency. See [[Dispersion (waves)]], [[Shallow-water wave theory]].
===<div id="Dissipative and reflective beaches"> Dissipative and reflective beaches </div>===
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===Dissipative and reflective beaches===
Dissipative beaches have typically gentle coastal profiles; they are subjected to energetic short-crested [[#Wave|waves]], which are strongly damped in the nearshore zone. Dissipative beaches have medium to large [[#Intertidal zone|intertidal zones]] which consist of fine (sandy or muddy) sediment. Reflective beaches have typically steep slopes and are subjected to low-energy [[#Wave|swell waves]]. An intertidal zone is almost absent and the beach consists mainly of coarse (sandy or gravelly) sediment. Beach types can be characterised by the so-called ' Dean parameter ' <math>\Omega=H_0/(w_s T_p)</math>, where <math>H_0</math> is the deep-water [[#Wave height|wave height]], <math>w_s</math> the mean fall velocity of beach sediment and <math>T_p</math> the peak spectral wave period. Reflective beaches correspond to  <math>\Omega < 1</math> and dissipative beaches to <math>\Omega > 6</math>.  
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Dissipative beaches have typically gentle coastal profiles; they are subjected to energetic short-crested [[#Wave|waves]], which are strongly damped in the nearshore zone. Dissipative beaches have medium to large [[#Intertidal zone|intertidal zones]] which consist of fine (sandy or muddy) sediment. Reflective beaches have typically steep slopes and are subjected to low-energy [[#Wave|swell waves]]. An intertidal zone is almost absent and the beach consists mainly of coarse (sandy or gravelly) sediment. Beach types can be characterised by the so-called ' Dean parameter ' <math>\Omega=H_0/(w_s T_p)</math>, where <math>H_0</math> is the deep-water [[#Wave height|wave height]], <math>w_s</math> the mean fall velocity of beach sediment and <math>T_p</math> the peak spectral wave period. Reflective beaches correspond to  <math>\Omega < 1</math> and dissipative beaches to <math>\Omega > 6</math>. See [[Shoreface profile]] and [[Characteristics of sedimentary shores]].
===<div id="Dunes"> Dunes</div>===
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===Dunes===
 
#The term 'dunes' generally indicates subaerial dunes. These dunes are ridges or moulds of loose, wind-blown sand (fine to medium) forming on the [[#Backshore|backshore]] and forming the coastal features at certain locations. Dunes are more or less vegetated. Dunes are active coastal form elements acting as a flexible sand reservoir. At coasts subject to [[#Coastal erosion|structural coastal erosion]] they are moving backwards in parallel with shoreline retreat. Dunes act as a kind of flexible natural protection against erosion and flooding, see [[Dune erosion]]. If the vegetation is damaged by too much traffic or grazing etc. the integrity of the dunes may be endangered.
 
#The term 'dunes' generally indicates subaerial dunes. These dunes are ridges or moulds of loose, wind-blown sand (fine to medium) forming on the [[#Backshore|backshore]] and forming the coastal features at certain locations. Dunes are more or less vegetated. Dunes are active coastal form elements acting as a flexible sand reservoir. At coasts subject to [[#Coastal erosion|structural coastal erosion]] they are moving backwards in parallel with shoreline retreat. Dunes act as a kind of flexible natural protection against erosion and flooding, see [[Dune erosion]]. If the vegetation is damaged by too much traffic or grazing etc. the integrity of the dunes may be endangered.
#The term 'dunes' is also used for subaqueous dunes, which are frequently called '''sandwaves'''. Subaqueous dunes are [[#Bed forms|bed forms]] induced by the interaction of the seabed with currents. Sandy seabeds are often covered with dune fields in regions where the maximum (tidal) current velocity is in the range 0.5-1.5 m/s. Dune spacing (generally more than 10 m and less than 1000 m) depends mainly on water depth. Dunes can reach a height of 10-50% of the water depth; high dunes present a risk for navigation.  
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#The term 'dunes' is also used for subaqueous dunes, which are usually called '''sandwaves''' in shelf seas. Subaqueous dunes are [[#Bed forms|bed forms]] induced by the interaction of the seabed with (mainly tidal) currents. Sandy seabeds are often covered with dune fields in regions where the maximum tidal current velocity is in the range 0.5-1.5 m/s. Dune spacing (more than 10 m and less than 1000 m) depends mainly on water depth. Dunes can reach a height of 10-50% of the water depth; high dunes present a risk for navigation.  
===<div id=" Environmental impact assessment (EIA)"> Environmental impact assessment (EIA)</div>===
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===Dunefoot===
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Transition between the [[#Backshore|backshore]] beach and the much steeper dune.
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===Ebb and flood tides===
 +
The following two definitions of ebb and flood can be found in the literature:
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#Ebb is the tidal phase during which the tidal current is flowing seaward (ebb current) and flood is the tidal phase during which the tidal current is flowing inland (flood current);
 +
#Ebb is the tidal phase during which the water level is falling and flood the tidal phase during which the water level is rising.
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The two definitions do not coincide. The first definition is more usual for tidal inlet systems: estuaries, tidal lagoons and tidal rivers; the second definition is more usual for the open coast.
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===[[Edge waves|Edge wave]]===
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Obliquely incident waves trapped to the shore by wave refraction and reflection. Non-breaking long-period waves ([[infragravity waves]]) that are not strongly dissipated in the nearshore zone cannot escape to deep water after reflection but continue travelling along the shore.
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===Environmental impact assessment (EIA)===
 
A written analysis of the predicted environmental consequences of a proposed development activity, including  
 
A written analysis of the predicted environmental consequences of a proposed development activity, including  
 
*a description of the avoidable and unavoidable adverse environmental effects (in conjunction with the cumulative effect of other human interventions);
 
*a description of the avoidable and unavoidable adverse environmental effects (in conjunction with the cumulative effect of other human interventions);
 
*a description of alternatives to the activity which might be less harmful to the environment, together with the reasons why such alternatives were rejected;
 
*a description of alternatives to the activity which might be less harmful to the environment, together with the reasons why such alternatives were rejected;
 
*a description of any required irreversible or irretrievable commitments of resources required by the proposed development activity.
 
*a description of any required irreversible or irretrievable commitments of resources required by the proposed development activity.
===<div id="Estuary"> Estuary </div>===  
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===Estuary===  
 
The transition zone between the riverine and the marine environment. A usual definition is: a semi-enclosed coastal body of water, which has a free connection with the open sea, and within which sea water is measurably diluted with freshwater derived from land drainage. Strong tides intrude in general much further upstream than seawater. From a morphological and sedimentary point of view it is therefore more logical to consider as upstream estuarine boundary the location where tidal discharges become much smaller than river discharges, instead of the seawater intrusion limit. See: [[Seawater intrusion and mixing in estuaries]], [[Morphology of estuaries]].
 
The transition zone between the riverine and the marine environment. A usual definition is: a semi-enclosed coastal body of water, which has a free connection with the open sea, and within which sea water is measurably diluted with freshwater derived from land drainage. Strong tides intrude in general much further upstream than seawater. From a morphological and sedimentary point of view it is therefore more logical to consider as upstream estuarine boundary the location where tidal discharges become much smaller than river discharges, instead of the seawater intrusion limit. See: [[Seawater intrusion and mixing in estuaries]], [[Morphology of estuaries]].
===<div id="Estuarine circulation"> Estuarine circulation</div>===  
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===Estuarine circulation===  
 
Residual flow pattern in an estuary driven by density differences between fluvial water and seawater.  
 
Residual flow pattern in an estuary driven by density differences between fluvial water and seawater.  
See: [[Estuarine circulation]], [[Salt wedge estuaries]].   
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See: [[Estuarine circulation]], [[Salt wedge estuaries]].  
===<div id="Fetch"> Fetch</div>===
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===Excavation===
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See [[#Mining|Mining]]  
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===Fetch===
 
Length in the wind direction of the marine area where water waves are generated by wind.  
 
Length in the wind direction of the marine area where water waves are generated by wind.  
===<div id="Friction"> Friction</div>===  
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===Fluid mud===
Shear stresses generated by the seabed and by flow obstacles, causing loss of fluid momentum. The shear stresses are transmitted to the flow via the turbulent [[#Boundary layer|boundary layer]]. See: [[#Bed forms|Bed forms]], [[Bed roughness and friction factors in estuaries]], [[Bedforms and roughness]]
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Fluid mud is a high-concentration colloidal suspension of fine sediment particles (< 63 µm, with often a high percentage of clay < 4 µm). It is formed by settling of mudflocs into a near-bottom suspended layer at a higher rate than the dewatering rate, or by fluidization and/or liquefaction of an underconsolidated mud bottom. See [[Fluid mud]].
===<div id="Foreshore or Beach face"> Foreshore or Beach face </div>===  
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===Friction===  
The zone between mean low water (MLW) and the seaward [[#Beach berm|beach berm]], which is equivalent to the upper limit of [[#Wave run-up|wave run-up]] at high tide. The foreshore is the part of the [[#Beach|shore/beach]] which is wet due to the varying tide and wave run-up under normal conditions, i.e., excluding the impact of extreme storm waves and [[#Storm surge|storm surge]]. This means that the foreshore in morphological terms extends further up on the beach than the intersection between the mean high water (MHW) and the coastal profile (MHW line). However, for practical reasons the administrative upper delineation of the foreshore is often defined as the intersection between the MHW line and the coastal profile, which is identical to the definition of the [[#Shoreline|shoreline]]. 
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Shear stresses generated by the seabed (sediment grains, bedforms) and by flow obstacles, causing loss of fluid momentum. The shear stresses are transmitted to the flow via the turbulent [[#Boundary layer|boundary layer]]. See: [[#Bed forms|Bed forms]], [[Bed roughness and friction factors in estuaries]], [[Bedforms and roughness]]
===<div id="Gravel beach"> Gravel beach</div>===  
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===Foreshore===  
Beach built of granular material with a size larger than 1 mm:  very coarse sand (>1 mm), gravel (2-4 mm), pebbles (4-64 mm) and cobbles (>64 mm). Beach material often originates from erosion of nearby cliffs or is supplied by gravel rivers draining nearby mountains. Gravel beaches have steep slopes and occur on coasts exposed to strong wave action. [[#Beach cusps|Cusp patterns]] are a common beach feature. See: [[Gravel Beaches]].  
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Same as [[#Beach face|beach face]].
===<div id="Groyne"> Groyne or groin</div>===  
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===Graded sediment===
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A sediment bed composed of a mixture of fine and coarse grained sediment particles.  
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===Gravel beach===  
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Beach built of granular material with a size larger than 1 mm:  very coarse sand (>1 mm), gravel (2-4 mm), pebbles (4-64 mm) and cobbles (>64 mm), see [[Coastal and marine sediments]]. Beach material often originates from erosion of nearby cliffs or is supplied by gravel rivers draining nearby mountains. Gravel beaches have steep slopes and occur on coasts exposed to strong wave action. [[#Beach cusps|Cusp patterns]] are a common beach feature. See: [[Gravel Beaches]].  
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===Groyne or groin===  
 
A straight structure perpendicular to the shoreline. Groynes work by blocking (part of) the [[#Littoral drift|littoral drift]]. They trap/maintain sand on their updrift side and cause erosion on the downdrift side. Groynes can have special shapes and they can be emerged, sloping or submerged, they can be single or in groups, the so-called groyne fields. Groynes are normally built as rubble mound structures, but they can also be constructed in other materials, such as concrete units, timber, etc. See: [[Groynes]], [[Groynes as shore protection]], [[Deteriorated groynes]].
 
A straight structure perpendicular to the shoreline. Groynes work by blocking (part of) the [[#Littoral drift|littoral drift]]. They trap/maintain sand on their updrift side and cause erosion on the downdrift side. Groynes can have special shapes and they can be emerged, sloping or submerged, they can be single or in groups, the so-called groyne fields. Groynes are normally built as rubble mound structures, but they can also be constructed in other materials, such as concrete units, timber, etc. See: [[Groynes]], [[Groynes as shore protection]], [[Deteriorated groynes]].
===<div id="Headland"> Headland</div>===  
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===Headland===  
 
Land mass with a considerable elevation that borders beaches. Headlands form the boundaries to [[#Sediment cell|sediment cells]], compartmentalising sand transport along the shore, and reducing sand exchange between adjacent beaches.
 
Land mass with a considerable elevation that borders beaches. Headlands form the boundaries to [[#Sediment cell|sediment cells]], compartmentalising sand transport along the shore, and reducing sand exchange between adjacent beaches.
===<div id="Infragravity waves"> Infragravity waves</div>===  
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Ocean surface waves with a period of typicallly 25-250 s. They arise in particular through non-linear interactions within [[#Wave group|wave groups]]. They play an important role in beach dynamics of [[#Dissipative and reflective beaches|dissipative coasts]] because their amplitude increases shoreward, relative to the breaking short waves. See: [[Infragravity waves]].
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Artificial headlands are smooth structures built from the coastline over the beach and some distance out on the shoreface. They work by blocking (part of) the littoral transport. A headland combines the effects of groynes and detached breakwaters and at the same time, minimises some of the disadvantages of groynes and breakwaters – see [[Detached breakwaters#Modified breakwaters and headlands| Modified breakwaters and headlands]].
===<div id="Internal waves"> Internal waves</div>===  
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===Infragravity waves===  
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Ocean surface waves with a period of typicallly 30-300 s. They arise in particular through non-linear interactions within [[#Wave group|wave groups]] in shallow water. They play an important role in beach dynamics of [[#Dissipative and reflective beaches|dissipative coasts]] because their amplitude increases shoreward, relative to the breaking short waves. See: [[Infragravity waves]].
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===Internal waves===  
 
Waves on the [[#Stratification|interface]] of fluid layers with different densities. Internal waves can be very large when the density difference between the fluid layers is small. Breaking of internal waves contributes to mixing of the layers and destruction of the layer structure.
 
Waves on the [[#Stratification|interface]] of fluid layers with different densities. Internal waves can be very large when the density difference between the fluid layers is small. Breaking of internal waves contributes to mixing of the layers and destruction of the layer structure.
===<div id="Intertidal zone"> Intertidal zone</div>===  
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===Intertidal zone===  
Area which is dry at low water (LW) and submerged at high water (HW), where LW and HW refer to mean [[#Tidal range|spring tide]]. The [[#Foreshore or Beach face|foreshore]], [[#Tidal flat|tidal flats]] and (parts of) [[#Salt marsh|salt marshes]] are intertidal zones.   
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Area which is dry at low water (LW) and submerged at high water (HW), where LW and HW refer to mean [[#Tidal range|spring tide]]. The [[#Beach face|beach face]], [[#Tidal flat|tidal flats]] and (parts of) [[#Salt marsh|salt marshes]] are intertidal zones.   
===<div id="Jetty"> Jetty</div>===  
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===Jetty===  
 
#Breakwater protecting a harbour entrance channel from wave action (also called '''harbour mole''');
 
#Breakwater protecting a harbour entrance channel from wave action (also called '''harbour mole''');
 
#Structure (often a bridge) connecting an offshore ship mooring to the coast.   
 
#Structure (often a bridge) connecting an offshore ship mooring to the coast.   
===<div id="Lagoon"> Lagoon </div>===  
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===Lagoon===  
Area of relatively shallow water situated in a coastal environment, separated from the open marine conditions by a natural barrier (a sandbar, a barrier island or a coral reef), but with an access to the sea. One may distinguish between microtidal and macrotidal lagoons. Examples of microtidal lagoons are Great South Bay and Pamlico Sound at the US Atlantic coast. Examples of macrotidal lagoons (also called '''tidal lagoons''') are the Wadden Sea at the Dutch-German-Danish North Sea coast and the Bassin d'Arcachon at the French Atlantic coast. Tidal lagoons are distinct from microtidal lagoons by the existence of deep [[#Tidal inlet|tidal inlets]] and large [[#Tidal flat|tidal flats]]. See also: [[Morphology of estuaries]].
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Area of relatively shallow water situated in a coastal environment, separated from the open marine conditions by a natural barrier (a [[#sand spit|sand spit]], a barrier island or a coral reef), but with an access to the sea. One may distinguish between microtidal and macrotidal lagoons. Examples of microtidal lagoons are Great South Bay and Pamlico Sound at the US Atlantic coast. Examples of macrotidal lagoons (also called '''tidal lagoons''') are the Wadden Sea at the Dutch-German-Danish North Sea coast and the Bassin d'Arcachon at the French Atlantic coast. Tidal lagoons are distinct from microtidal lagoons by the existence of deep [[#Tidal inlet|tidal inlets]] and large [[#Tidal flat|tidal flats]]. See also: [[Morphology of estuaries]].
===<div id="Littoral drift"> Littoral drift or Longshore sediment transport</div>===  
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===Littoral cell===
Littoral drift is the term used for the longshore transport of non-cohesive sediments, i.e. mainly sand, along the [[#Foreshore or Beach face|foreshore]] and the [[#Shoreface|shoreface]] due to the action of breaking [[#Wave|waves]]  and [[#Longshore current|longshore current]]. The littoral dift is also called longshore sediment transport. Formulas for the longshore sediment transport are given in: [[Long-term modelling using 1-line models - GENESIS and new extensions]].  
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Same as [[#Coastal cell|coastal cell]].
===<div id="Longshore current "> Longshore current </div>===  
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===Littoral drift===  
The longshore current or nearshore current is the dominating current in the [[#Nearshore zone|nearshore zone]] and is running parallel to the shore. The longshore current is generated by the shore-parallel component of the stresses associated with the breaking process for obliquely incoming [[#Wave|waves]] , the so-called radiation stresses, and by the surplus water which is carried across the [[#Breaker zone|breaker zone]] towards the coastline. See: [[Shallow-water wave theory]].
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Littoral drift or '''longshore sediment transport''' is the term used for the longshore transport of non-cohesive sediments, i.e. mainly sand, along the upper [[#Shoreface|shoreface]] due to the action of breaking [[#Wave|waves]]  and [[#Longshore current|longshore current]]s. Formulas for the longshore sediment transport are given in: [[Littoral drift and shoreline modelling]]; see also [[Coastal Hydrodynamics And Transport Processes]].  
===<div id="Management unit (MU)"> Management unit (MU)</div>===  
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===Littoral zone===
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In marine ecosystems the shore area or intertidal zone, where periodic exposure and submersion by tides is normal.
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===Longshore current===  
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The longshore current or nearshore current is the dominating current in the [[#Nearshore zone|nearshore zone]] and is running parallel to the shore. The longshore current is generated by the shore-parallel component of the stresses associated with the breaking process for obliquely incoming [[#Wave|waves]] , the so-called radiation stresses, and by the surplus water which is carried across the [[#Breaker zone|breaker zone]] towards the shoreline. See: [[Shallow-water wave theory]].
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===Longshore sediment transport===
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Same as [[#Littoral drift|Littoral drift]].
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===Management unit (MU)===  
 
A management unit is a coastal stretch with coherent characteristics in terms of both natural coastal processes and land use. The MU is used as boundary for Shoreline Master Plans.
 
A management unit is a coastal stretch with coherent characteristics in terms of both natural coastal processes and land use. The MU is used as boundary for Shoreline Master Plans.
===<div id="Meandering"> Meandering</div>===  
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===Marine regression===
 +
Coastal extension due to a falling relative sea level.
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===Meandering===  
 
Natural propensity of a flow to scour the outer bend of a channel. When a channel meander becomes very large a cutoff channel (a so-called '''channel chute''') is often formed, leading to [[#Avulsion|avulsion]] of the meander.
 
Natural propensity of a flow to scour the outer bend of a channel. When a channel meander becomes very large a cutoff channel (a so-called '''channel chute''') is often formed, leading to [[#Avulsion|avulsion]] of the meander.
===<div id="Mining"> Mining or Excavation</div>===  
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===Mining===  
Mechanical removal of consolidated soil or unconsolidated material (aggregates like sand, gravel, shells) from seabed, beach or dunes.   
+
Mining (or '''excavation''') is the mechanical removal of consolidated soil or unconsolidated material (aggregates like sand, gravel, shells) from seabed, beach or dunes.   
===<div id="Mitigation"> Mitigation</div>===
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===Mitigation===
Action (or series of actions) aimed at (partly) neutralising the adverse impacts of past or planned human interventions.  
+
Measures aimed at countering, alleviating or partially obviating the adverse consequences of threatening developments or events that have a human or natural cause.
===<div id="Model"> Model</div>===
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===Model===
 
Physical or mathematical representation of nature, for studying or predicting coastal behaviour; see [[Modelling coastal hydrodynamics]].  
 
Physical or mathematical representation of nature, for studying or predicting coastal behaviour; see [[Modelling coastal hydrodynamics]].  
* Physical models. These models copy salient features of nature at a reduced scale in a laboratory setting. Scale effects are an important issue for the translation of observed model results to the natural scale. Major scale effects generally arise for the representation of phenomena influenced by [[#Friction|friction]], by [[#Sediment transport|sediment transport]] (including sediment erosion and deposition) and by biota.
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* Physical models. These models copy salient features of nature at a reduced scale in a laboratory setting. Scale effects are an important issue for the translation of observed model results to the natural scale. Major scale effects generally arise for the representation of phenomena influenced by [[#Friction|friction]], by [[#Sediment transport|sediment transport]] (including sediment erosion and deposition) and by biota. See [[Scaling Issues in Hydraulic Modelling]].
* Mathematical models. These models solve in one way or another the governing hydrodynamic (and/or morphodynamic) equations . They exist in many different types, see for example [[Estuarine morphological modelling]].  Most common types are: Analytical models, Numerical process-based models, Behaviour-based models, Stochastic models, Data-driven models, Particle-based models and Cellular models. '''Analytical models''' are based on explicit solutions of the governing equations, which are strongly simplified to retain only those features which are most pertinent to the studied phenomena. '''Numerical process-based''' models describe nature on a discretised grid, retaining all physical features relevant for a reliable and accurate representation of the studied phenomena; the governing equations are solved numerically for successive discrete time steps, see [[Process-based modelling]], [[Process-based morphological models]]. '''Behaviour-based models''' (also called Aggregate-scale models) consider the coastal system as an assembly of interacting subsystems and solve the governing equations numerically for the interactions at system level, whereas empirical relationships are used for representing the dynamics at subscale levels; see: [[Behaviour-based models]]. '''Stochastic models''' are process-based models which use probability distributions for certain input data for taking into account natural fluctuations (wave climate, river discharge, for example) or uncertainty (sea-level projections, model parameters, for example); see [[Stochastic and fractal methods in coastal morphodynamics]]. '''Data-driven models''' are used to make moving forecasts by integrating observed data of the recent history to calibrate uncertain model parameters or uncertain model input data, see: [[Reduction of uncertainties through Data Model Integration (DMI)]]. '''Particle-based models''' describe numerically the motion of discrete fluid parcels taking into account their mutual interaction according to the laws of physics; in the most popular method (called '''Smoothed-particle Hydrodynamics (SPH)''') the fluid is divided into a set of discrete moving parcels with properties which are smoothed over the parcel size according to a prescribed smoothing function. '''Cellular models''' divide the coastal system in fixed discrete cells which behave in a prescribed way according to the evolution of neighbouring cells, taking into account physical conservation laws.  
+
* Mathematical models. These models solve in one way or another the governing hydrodynamic (and/or morphodynamic) equations . They exist in many different types, see for example [[Estuarine morphological modelling]].  Most common types are: Analytical models, Numerical process-based models, Behaviour-based models, Stochastic models, Data-driven models, Particle-based models and Cellular models. '''Analytical models''' are based on explicit solutions of the governing equations, which are strongly simplified to retain only those features which are most pertinent to the studied phenomena. '''Numerical process-based''' models describe nature on a discretised grid, retaining all physical features relevant for a reliable and accurate representation of the studied phenomena; the governing equations are solved numerically for successive discrete time steps, see [[Process-based morphological models]]. '''Behaviour-based models''' (also called Aggregate-scale models) consider the coastal system as an assembly of interacting subsystems and solve the governing equations numerically for the interactions at system level, whereas empirical relationships are used for representing the dynamics at subscale levels; see: [[Behaviour-based models]]. '''Stochastic models''' are process-based models which use probability distributions for certain input data for taking into account natural fluctuations (wave climate, river discharge, for example) or uncertainty (sea-level projections, model parameters, for example); see [[Stochastic and fractal methods in coastal morphodynamics]]. '''Data-driven models''' are used to make moving forecasts by integrating observed data of the recent history to calibrate uncertain model parameters or uncertain model input data, see: [[Reduction of uncertainties through Data Model Integration (DMI)]]. '''Particle-based models''' describe numerically the motion of discrete fluid parcels taking into account their mutual interaction according to the laws of physics; in the most popular method (called '''Smoothed-particle Hydrodynamics (SPH)''') the fluid is divided into a set of discrete moving parcels with properties which are smoothed over the parcel size according to a prescribed smoothing function. '''Computational fluid dynamics (CFD)''' models solve the Navier-Stokes equations for multiphase flows, including the interaction of the fluid (liquids and gases) with surfaces defined by boundary conditions. '''Cellular models''' divide the coastal system in fixed discrete cells which behave in a prescribed way according to the evolution of neighbouring cells, taking into account physical conservation laws.  
 
*Hybrid models combine physical and numerical models.
 
*Hybrid models combine physical and numerical models.
===<div id="Nearshore zone">Nearshore zone</div>===  
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===Morphology===
The zone extending seaward from the low water line well beyond the [[#Breaker zone|breaker zone]]; it defines the area influenced by the nearshore currents. The nearshore zone extends somewhat further seaward than the [[#Shoreface|littoral zone]].
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The (study of the) shape or structure of natural objects, whether living or not. In the coastal context, morphology or geomorphology is generally used for designating the coastal [[#bathymetry|bathymetry]], including its sedimentary composition and structure. See also [[#Coastal morphology|Coastal morphology]].  
===<div id="Nourishment or Sand nourishment">Nourishment or Sand nourishment </div>===  
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===Morphodynamics===
Sand nourishment is a method to neutralize the effect of coastal erosion by maintaining the sand volume of the [[#Active coastal zone|active coastal zone]]. Sand is extracted (generally by dredging) from nearby sources and applied to the beach, the [[#Shoreface|shoreface]] or the dunes. The costs highly depend on the location of available sand sources, which should be situated outside (seaward of) the [[#Active coastal zone|active coastal zone]]. Dune nourishment is usually meant for safety against flooding, beach nourishment for restoration of the beach and shoreface nourishment for stabilizing the shoreline. See: [[Shore nourishment]], [[Artificial nourishment]].
+
See [[#Coastal morphodynamics|Coastal morphodynamics]].   
===<div id="Mud">Mud </div>===  
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===Mud===  
Fine cohesive [[#Sediment|sediment]] deposit containing a high fraction (≥20%) of clay minerals. Fine  sedimentary particles, consisting of clay minerals, but also other particles (silt, fine sand, organic matter), can be glued together by large organic molecules (extracellular polymeric substances, EPS) into large mud flocs. These flocs, with a diameter of  0.1-1 mm, settle much faster than the individual particles and can form a colloidal suspension on the seabed. This so-called '''fluid mud layer''' can move along the seabed (driven by pressure gradients at the interface, by flow entrainment or by bed slope effect) and be a major cause of harbor [[#Siltation|siltation]]. After consolidation, which is often a lengthy process, a mud bed can become highly resistant to erosion by currents. See: [[Dynamics of mud transport ]], [[Sediment deposition and erosion processes]], [[Sediment transport formulas for the coastal environment]], [[Characteristics of muddy coasts]].   
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Fine cohesive [[#Sediment|sediment]] deposit containing a high fraction (≥20%) of clay minerals. Fine  sedimentary particles, consisting of clay minerals, but also other particles (silt, fine sand, organic matter), can be glued together by large organic molecules (extracellular polymeric substances, EPS) into large mud flocs. These flocs, with a diameter of  0.1-1 mm, settle much faster than the individual particles and can form a colloidal suspension on the seabed. This so-called '''[[fluid mud]] layer''' can move along the seabed (driven by pressure gradients at the interface, by flow entrainment or by bed slope effect) and be a major cause of harbor [[#Siltation|siltation]]. After consolidation, which is often a lengthy process of months to years, a mud bed can become highly resistant to erosion by currents. See: [[Mud]], [[Dynamics of mud transport ]], [[Sediment deposition and erosion processes]], [[Coastal and marine sediments]]. 
===<div id="Overwash"> Overwash</div>===  
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===Nearshore zone===
 +
Same as [[#Shoreface|lower shoreface]].
 +
===Nourishment===
 +
Nourishment (or '''sand nourishment''') is a method to neutralize the effect of coastal erosion by maintaining the sand volume of the [[#Active coastal zone|active coastal zone]]. Sand is extracted (generally by dredging) from nearby sources and applied to the beach, the [[#Shoreface|shoreface]] or the dunes. The costs highly depend on the location of available sand sources, which should be situated outside (seaward of) the [[#Active coastal zone|active coastal zone]]. Dune nourishment is usually meant for safety against flooding, beach nourishment for restoration of the beach and shoreface nourishment for stabilizing the shoreline. See: [[Shore nourishment]], [[Artificial nourishment]].
 +
===Overwash===  
 
Wave uprush over a natural or artificial coastal barrier. The term overwash is also used for the resulting sand deposit at the leeside of the barrier.   
 
Wave uprush over a natural or artificial coastal barrier. The term overwash is also used for the resulting sand deposit at the leeside of the barrier.   
===<div id="Offshore zone"> Offshore zone </div>===  
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===Offshore zone===  
The offshore zone is not clearly delimited. In relation to beach terminology, the offshore zone is often defined as the zone off the [[#Nearshore zone|nearshore zone]].
+
Different definitions of the offshore zone can be found in the literature. It can be the zone off the [[shoreface]], off the [[surf zone]] or off the [[littoral zone]]. In the present context, the offshore zone is defined as the zone off the [[shoreface]].  
===<div id="Progradation"> Progradation</div>===  
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===Progradation===  
Coastal extension into the sea due to natural [[#Accretion|aggradation]]. Coastal progradation occurs specifically where rivers supply large amounts of sediment. Coastal extension due to fall of the relative sea level is generally termed '''Marine regression'''.  
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Coastal extension into the sea due to natural [[#Accretion or Aggradation|aggradation]]. Coastal progradation occurs specifically where rivers supply large amounts of sediment.  
===<div id="Propagation speed">Propagation speed</div>===
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===[[Shallow-water wave theory#Radiation Stress (Momentum Flux)|Radiation stress]]===
The speed at which a [[#Wave|wave]] propagates. The speed <math>c</math> of a wave propagating without frictional losses in shallow water is proportional to the square root of the water depth <math>h</math>  (formula: <math>c=\sqrt{gh}</math>). A [[#Wave group|wave group]] propagates at a smaller speed <math>c_g</math> than the constituent short waves. [[#Wave energy|Wave energy]] propagates at the speed of the wave group. See: [[Shallow-water wave theory]].
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The radiation stress is defined as the excess flow of momentum due to wave orbital motions (with units of force/unit length). Gradients in the radiation stress induce an effective momentum transfer from wave motion to steady motion that takes place when the wave amplitude changes along the direction of propagation.
===<div id="Reclamation"> Reclamation</div>===  
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===Reclamation===  
 
The transformation of areas which were formerly part of the marine or estuarine domain into non-floodable land.
 
The transformation of areas which were formerly part of the marine or estuarine domain into non-floodable land.
===<div id= "Reef"> Reef </div>===  
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===[[Reef]]===  
A ridge of material at or near the surface of the ocean. Natural reefs are made of rocks or the skeletons of small animals called corals. Reefs can also be created artificially for several reasons:  
+
A ridge of material at or near the surface of the ocean. Natural reefs are made of rocks or the skeletons of small animals (mainly corals). Reefs can also be created artificially for several reasons:  
 
* Protect coastlines from erosion;
 
* Protect coastlines from erosion;
 
* Promote sea life for recreation and aquaculture;
 
* Promote sea life for recreation and aquaculture;
 
* Create a wave pattern that promotes the sport of surfing.  
 
* Create a wave pattern that promotes the sport of surfing.  
See: [[Natural barriers]], [[Artificial reefs]].
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See: [[Coral reefs]], [[Natural shore protecting barriers]], [[Artificial reefs]].
===<div id="Refraction"> Refraction </div>===  
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===Reflective beaches===
 +
See [[#Dissipative and reflective beaches|Dissipative and reflective beaches]]
 +
===[[Refraction]]===  
 
The propensity of [[#Wave|waves]]  to align the wave front in shallow water with the depth contour, according to Snell's law. Also: Change of wave propagation direction due to the interaction with currents.
 
The propensity of [[#Wave|waves]]  to align the wave front in shallow water with the depth contour, according to Snell's law. Also: Change of wave propagation direction due to the interaction with currents.
===<div id="Rip current"> Rip current </div>===  
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===[[Rip current]]===  
A local current directed away from the shore, bringing the surplus water carried over [[#Breaker bar|breaker bars]] back into deeper water. Rip currents may occur at certain intervals along the shoreline as a result of the interaction between breaking [[#Wave|waves]] and the nearshore bathymetry, see: [[Rhythmic shoreline features]], [[Stability models]]. The rip opening in the [[#Breaker bar|breaker bars]] will often form the lowest section of the coastal profile; a local setback in the shoreline is often seen opposite the rip opening. The rip opening travels slowly downstream. Rip currents are dangerous for swimmers.
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Rip currents are strong offshore directed [[currents]] that occur when high waves break over nearshore sandbars. When breaking, high incident waves raise the water level in the area between the beach and [[nearshore sandbars]]. This elevated water is discharged by rip currents that flow seaward through narrow gaps between the nearshore bars. The corresponding morphological pattern is called "rip cell". It results from the [[Coastal morphodynamics|morphodynamic feedback]] between the [[coastal morphology]] and the incident wave field. A local setback in the shoreline is often seen opposite the rip opening. The rip opening travels slowly downstream. Rip currents are dangerous for swimmers. See [[Rhythmic shoreline features]].
===<div id="Runnel"> Runnel </div>===  
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===[[Revetment]]===
Small beach channel draining a tidal pool left on the beach after high water.
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A revetment is a facing of stone, concrete units or slabs, etc., built to protect a scarp, the foot of a cliff or a dune, a dike or a seawall against erosion by wave action, storm surge and currents. This definition is very similar to the definition of a seawall, however a revetment does not protect against flooding. Furthermore, a revetment is often a supplement to other types of protection such as seawalls and dikes. See [[Revetments]], [[Seawalls and revetments]], [[Stability of rubble mound breakwaters and shore revetments]].
===<div id="Salt marsh"> Salt marsh</div>===  
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===[[Runnel]]===  
A densely vegetated coastal ecosystem situated in the upper coastal [[#Intertidal zone|intertidal zone]] between land and [[#Tidal flat|intertidal mudflats]], or bordering directly open saltwater or brackish water if mudflats are absent. Salt marshes are sometimes referred to as '''schorre''' or '''kwelder'''. The soil may be composed of deep mud and peat. Salt marshes usually form in areas that are well sheltered, such as [[#Lagoon|lagoons]] and [[#Estuary|estuaries]] where fine sediments can be deposited. They also form behind spits and artificial sea defences where tidal waters can flow gently and deposit fine sediments. See also: [[Salt marshes]].
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Depression between intertidal bars or between the dry beach and the upper intertidal bar (beach ridge). After high tide, the depression is filled with water, which is gradually discharged to the sea during falling tide via a channel (a so-called rip channel) that cuts through the beach ridge.
===<div id="Sand bank"> Sand bank</div>===  
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===[[Salt marsh]]===  
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A densely vegetated coastal ecosystem situated in the upper coastal [[#Intertidal zone|intertidal zone]] between land and [[#Tidal flat|intertidal mudflats]], or bordering directly open saltwater or brackish water if mudflats are absent.
 +
*[[Salt marshes]] are a key habitat of transitional waters lying at the interface between the land and the sea, depending on, and periodically covered by tidal sea water.
 +
*Salt marsh vegetation is usually composed of grasses and other low plants, but not trees.
 +
*Water saturation is the dominant factor controlling plant and animal communities and soils.
 +
*The soil may be composed of deep mud and peat.  
 +
*Salt marshes are drained by tidal creeks that form spontaneously depending on local soil characteristics and gradients in the hydraulic head of infiltrated water.
 +
*Salt marshes usually form in sheltered coastal systems, such as [[#Lagoon|lagoons]] and [[#Estuary|estuaries]] where fine sediments can be deposited. Salt marshes can also form behind spits and artificial sea defences where tidal waters can flow gently and deposit fine sediments.
 +
*Salt marshes are sometimes referred to as '''schorre''' or '''kwelder'''.
 +
See: [[Salt marshes]].
 +
===Sand bank===  
 
Popular term for large [[#Bar|bars]] and [[#Tidal ridge|ridges]] in tidal waters, especially in relation to navigation hindrance.
 
Popular term for large [[#Bar|bars]] and [[#Tidal ridge|ridges]] in tidal waters, especially in relation to navigation hindrance.
===<div id="Sand wave"> Sand wave</div>===  
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===Sand nourishment===
 +
See [[#Nourishment|Nourishment]]
 +
===[[Sand spit]]===
 +
A sand spit is an accretionary feature formed by [[#Littoral drift|littoral drift]], consisting of a long narrow accumulation of sand or gravel, lying generally in line with the updrift coast, with one end attached to the land and the other projecting into the sea or across the mouth of an [[#Estuary|estuary]] or [[#Lagoon|lagoon]]. During dry periods, a spit can develop into a '''barrier''' that temporarily blocks the mouth of a lagoon or a small river. See [[Sand spit]].
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===Sandwave===  
 
# A subaqueous [[#Dunes|dune]];
 
# A subaqueous [[#Dunes|dune]];
 
# A shoreline undulation with a wavelength in the range of a few hundred meters to a few kilometers, see: [[Rhythmic shoreline features]].
 
# A shoreline undulation with a wavelength in the range of a few hundred meters to a few kilometers, see: [[Rhythmic shoreline features]].
===<div id="Sea-level rise"> Sea-level rise </div>===  
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===[[Sea level rise]]===  
The so-called greenhouse effect or global warming causes a rise of the mean sea level, which will have a great impact on long-term coastal morphology. The long-term gradual sea-level rise will cause a general [[#Coastline retreat|coastline retreat]] and an increased flooding risk depending on local conditions. Instead of the absolute rise of the mean sea level it is more relevant to consider the '''relative sea-level rise''': the rise relative to vertical land motions that can be positive ('''uplift''') or negative ('''subsidence'''). An estimate of coastline retreat due to relative sea-level rise can be derived from the so-called '''Bruun rule''', which is valid under certain rather restrictive conditions, see: [[Bruun rule]].
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The so-called greenhouse effect or global warming causes a rise of the mean sea level, which will have a great impact on long-term coastal morphology, see [[Sea level rise]]. The long-term gradual sea-level rise will cause a general [[#Coastline retreat|coastline retreat]] and an increased flooding risk depending on local conditions. Instead of the absolute rise of the mean sea level it is more relevant to consider the '''relative sea-level rise''': the rise relative to vertical land motions that can be positive ('''uplift''') or negative ('''subsidence'''). An estimate of coastline retreat due to relative sea-level rise can be derived from the so-called '''Bruun rule''', which is valid under certain rather restrictive conditions, see: [[Bruun rule]].
===<div id="Sediment"> Sediment</div>===  
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===[[Sediment]]===  
Fine-grained loose particles such as gravel, sand, mud. These sediments are produced by chemical or physical weathering of rocks, by seabed erosion and by soil erosion in river basins. They are called clastic sediments and consist of quartz, feldspar, mica and clay minerals. Other particles have a biotic origin, for example shell debris, peat, detritus, fecal pellets and plankton. Sediment particles have widely different grainsizes:  clay (< 0.002 mm), silt  (0.01-0.02 mm), sand (0.1-2 mm), gravel (2-5 mm). The density is of the order of 2.6 times the density of water. Sand or gravel beds occur in zones with strong (tidal) currents and strong wave activity, whereas fine sand, silt and mud cover the seabed in sheltered zones where currents and wave activity are weak. See: [[Sediment deposition and erosion processes]], [[Gravel Beaches]].
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Fine-grained loose particles such as gravel, sand, mud. These sediments are produced by chemical or physical weathering of rocks, by seabed erosion and by soil erosion in river basins. They are called clastic sediments and consist of quartz, feldspar, mica and clay minerals. Other particles have a biotic origin, for example shell debris, peat, detritus, fecal pellets and plankton. Sediment particles have widely different grainsizes:  clay (< 0.002 mm), silt  (0.01-0.02 mm), sand (0.1-2 mm), gravel (2-5 mm). The density is of the order of 2.65 times the density of water. Sand or gravel beds occur in zones with strong (tidal) currents and strong wave activity, whereas fine sand, silt and mud cover the seabed in sheltered zones where currents and wave activity are weak. See: [[Coastal and marine sediments]], [[Sediment deposition and erosion processes]], [[Gravel Beaches]].
===<div id="Sediment cell"> Sediment cell, Littoral cell or Coastal cell</div>===  
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===Sediment cell===
A coastal compartment that contains a complete cycle of sedimentation including sources, transport paths, and sinks. The cell boundaries (often corresponding to headlands or jetties) delineate the geographical area within which the budget of sediment is balanced, providing the framework for the quantitative analysis of coastal erosion and accretion.
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Same as [[#Coastal cell|coastal cell]].
===<div id="Sediment transport"> Sediment transport</div>===  
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===Sediment transport===  
The capacity of currents and [[#Wave|waves]] to move [[#Sediment|sediments]]. Sediment transport is a crucial link in the interaction between coastal morphological evolution and waves, currents and tides. Sedimentation is related to convergence of sediment transport and erosion to divergence of sediment transport. Sediment transport takes place in several ways: Suspended-load transport, Bedload transport and Fluid mud motion. '''Suspended-load transport''' is the transport of sedimentary particles that are suspended in the fluid. '''Bedload transport''' is the transport of sedimentary particles that are rolling or leaping along the seabed. '''Fluid mud transport''' is the motion of a [[#Mud|fluid mud layer]] along the seabed. Formulas for bedload transport are based on empirical relationships involving characteristics of sediment, currents and waves. See: [[Sediment transport formulas for the coastal environment]], [[Sand transport]].   
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The amount of [[#Sediment|sediment]] transported by water motion (currents and /or [[#Wave|waves]]). Sediment transport is a crucial link in the interaction between coastal morphological evolution and waves, currents and tides. Sedimentation is related to convergence of sediment transport and erosion to divergence of sediment transport. Sediment transport takes place in several ways: Suspended-load transport, Bedload transport and Fluid mud motion. '''Suspended-load transport''' is the transport of sedimentary particles that are suspended in the fluid. '''Bedload transport''' is the transport of sedimentary particles that are rolling or leaping along the seabed. '''Fluid mud transport''' is the motion of a [[#Mud|fluid mud layer]] along the seabed. Formulas for bedload transport are based on empirical relationships involving characteristics of sediment, currents and waves. See: [[Sediment transport formulas for the coastal environment]], [[Sand transport]].   
===<div id="Seiche"> Seiche</div>===
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===[[Seiche]]===
Oscillation of a semi-enclosed water body caused by incoming long-period waves (periods typically in the range 200-2000 s). Seiches can be strongly amplified in harbour basins if the period is close to the harbour resonance period, causing damage to ships and moorings.  
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Harbour seiches are resonant (or near-resonant) standing oscillations in a semi-enclosed water body caused by incoming long-period waves (periods typically in the range 200-2000 s).
===<div id="Setback area "> Setback area </div>===  
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Incoming waves can be strongly amplified if the period is close to the harbour resonance period, causing damage to ships and moorings.
A strip along the coastal zone where certain development activities are prohibited or significantly restricted.  
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Long-period waves can be generated by nonlinear interaction of random short waves with a peaked frequency distribution (see [[Infragravity waves]]), generated mainly in shallow water and reflected from adjacent coasts.
===<div id="Shelf sea"> Shelf sea</div>===
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Long-period waves can also be generated by meteorological effects, in particular strong wind speed fluctuations during storms, related to the passage of a cold front.
 +
Other generation mechanisms include deep-sea internal waves, seismic activity, or tsunamis.
 +
Seiches occur also in closed basins, such as lakes, often induced by strong fluctuations in the wind field.
 +
===[[Setback area]]===  
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A strip along the coastal zone where certain development activities are prohibited or significantly restricted. See: [[Setback area]].
 +
===Sheet-flow===
 +
Sheet-flow sediment transport refers to transport of sandy sediments as a fluidized thin surface layer (thickness of ten to several tens grain diameters). This type of sediment transport occurs under strong wave action (wave orbital velocity greater than 1 m/s), where bed ripples are flattened out. In the sheet-flow layer, continuous contacts between sand grains create an intergranular stress. This stress decreases the velocity in *the sheet-flow layer to about one half the velocity in the top layer. The sediment concentration in the sheet-flow layer is in the order of 100 to 1000 kg/m3. See: [[Sediment transport formulas for the coastal environment]].
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===Shelf sea===
 
See [[#Continental shelf|Continental shelf]].
 
See [[#Continental shelf|Continental shelf]].
===<div id="Shoaling"> Shoaling</div>===
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===Shoaling===
Amplification of incident [[#Wave|waves]] in the [[#Nearshore zone|nearshore zone]] before breaking. Amplification is due to (approximate) continuity of the '''wave energy flux''' <math>F=c_g E</math> seaward of the [[#Breaker zone|breaker zone]], where <math>E</math> is the [[#Wave energy|wave energy]] and <math>c_g</math> the [[#Wave group|wave group]] [[#Propagation speed|propagation speed]]. The landward decrease of <math>c_g</math> results in a landward increase of <math>E</math>, thus in a landward increase of [[#Wave height|wave height]] <math>H</math>. See: [[Shallow-water wave theory]].  
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Shoaling is the deformation of incident waves on the lower [[shoreface]] that starts when the water depth becomes less than about half of the [[wavelength]], causing the waves to become steeper: increase in amplitude and decrease in wavelength.  
===<div id=" Shore protection "> Shore protection </div>===  
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*Wave amplification is due to (approximate) continuity of the '''wave energy flux''' <math>F=c_g E</math> seaward of the [[surf zone]], where <math>E = \frac{1}{8} \rho g H^2</math> is the wave energy  and <math>c_g</math> the [[wave group]] propagation speed. The landward decrease of the wave group propagation speed (<math>c_g \approx \sqrt{gh}</math> in shallow water of depth <math>h</math>) results in a landward increase of <math>E</math>, thus in a landward increase of wave height <math>H</math>. See: [[Shallow-water wave theory]] for a more detailed treatment.
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*Wave propagation in the shoaling zone has a strongly non-linear character because the wave height is no longer negligible compared to the water depth. This produces wave asymmetry, with the wave orbital velocity being greater in the onshore than offshore direction and the offshore-to-onshore orbital acceleration being greater than the onshore-to-offshore acceleration.
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*Wave shoaling precedes wave breaking on the upper shoreface when the wave steepness exceeds a critical limit.  
 +
===Shore protection===  
 
See [[#Coastal protection|Coastal protection]].
 
See [[#Coastal protection|Coastal protection]].
===<div id="Shoreface"> Shoreface or Littoral zone</div>===  
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===Shoreface===  
The shoreface or littoral zone is part of the [[#Active coastal zone|active coastal zone]] situated seaward of the low water line. This zone extends seaward from the [[#Foreshore or Beach face|foreshore]] to some distance beyond the [[#Breaker zone|breaker zone]]. The littoral zone is the zone in which littoral morphodynamic processes take place, related mainly to [[#Littoral drift|longshore sediment transport]] and cross-shore sediment transport. The width of the instantaneous littoral zone varies dependent of the wave conditions. In the general context, the littoral zone is defined as the zone corresponding to the yearly wave climate. The width of the littoral zone can thus be defined as the width of the sediment transport zone for the significant [[#Wave height|wave height]], which is exceeded 12 hours per year, <math>H_{s,12h/y}</math>.
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The shoreface is the '''nearshore zone''' of the inner continental shelf that is bounded landward by the mean low-water line and that extends seaward to where the influence of wave action on sediment transport is on average minor compared to other influences. A similar definition is: The shoreface is the zone seaward of the shoreline where offshore generated waves interact with the upward sloping seabed. The shoreface can be divided in two zones, the upper shoreface and the lower shoreface (also called [[#Shoaling|shoaling zone]]). The upper shoreface is the zone where most energy is dissipated by wave overturning and breaking and the lower shoreface the zone where waves shoal. The lower part of the shoreface extends to the so-called outer [[closure depth]] <math>h_{out}</math>; beyond this depth the seabed is hardly influenced by waves and wave-induced sediment transport is (on average) insignificant. The transition between lower and upper shoreface is generally defined by the [[closure depth]] <math>h_{in}</math> related to the significant [[#Wave height|wave height]], which is exceeded 12 hours per year, <math>H_{s,12h/y}</math>. See [[Shoreface profile]].  
===<div id="Shoreline"> Shoreline </div>===  
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===[[Shoreline]]===  
The intersection between the mean high water line and the shore. The line delineating the shoreline on Nautical Charts (Sea Maps) approximates this Mean High Water Line. The shoreline is not easy to identify in the nature in contrast to the coastline, which is based on a clear morphological shift between the shore and the coast.
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The intersection between the water line and the shore. The line delineating the shoreline on Nautical Charts (Sea Maps) approximates the Mean High Water Line. See the article [[Shoreline]] for an overview of shoreline detection techniques.  
===<div id="Shoreline management"> Shoreline management </div>===  
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===Shoreline management===  
The act of dealing – in a planned way – with actual and potential coastal erosion and its relation to planned or existing development activities on the coast. The objectives of Shoreline Management are:  
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The act of dealing – in a planned way – with actual and potential coastal erosion and its relation to planned or existing development activities on the coast, see [[Shoreline management]]. The objectives of Shoreline Management are:  
 
*To ensure the development activities in the coastal area follow an overall land use plan and a general environmental policy;
 
*To ensure the development activities in the coastal area follow an overall land use plan and a general environmental policy;
 
*To ensure the development activities in the coastal area do not cause to or aggravate erosion;
 
*To ensure the development activities in the coastal area do not cause to or aggravate erosion;
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*To ensure that erosion control techniques are cost-effective and socially and environmentally acceptable.
 
*To ensure that erosion control techniques are cost-effective and socially and environmentally acceptable.
 
Shoreline management is typically based on [[#Sediment cell|coastal sediment cells]].  
 
Shoreline management is typically based on [[#Sediment cell|coastal sediment cells]].  
===<div id="Siltation"> Siltation</div>===  
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===Siltation===  
 
Accumulation of fine sediments (sand, silt, mud) in channels, harbors and fairways. See: [[Siltation in harbors and fairways]], [[Dynamics of mud transport ]], [[Sediment deposition and erosion processes]], [[Sediment transport formulas for the coastal environment]].
 
Accumulation of fine sediments (sand, silt, mud) in channels, harbors and fairways. See: [[Siltation in harbors and fairways]], [[Dynamics of mud transport ]], [[Sediment deposition and erosion processes]], [[Sediment transport formulas for the coastal environment]].
===<div id="Slack tide"> Slack tide </div>===  
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===Slack tide===  
Tidal phase at which the current turns from flood to ebb (high-water slack tide) or from ebb to flood (low-water slack tide).
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Tidal phase at which the current turns from flood to ebb (high-water slack tide) or from ebb to flood (low-water slack tide). See [[Definition of ebb and flood (tide)]].
===<div id="Spit"> Spit </div>===  
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===Shore===
An accretionary feature formed by [[#Littoral drift|littoral drift]], consisting of a long narrow accumulation of sand or gravel, lying generally in line with the coast, with one end attached to the land and the other projecting into the sea or across the mouth of an [[#Estuary|estuary]] or [[#Lagoon|lagoon]]. During dry periods, a spit can develop into a '''barrier''' that temporarily blocks the mouth of a lagoon or a small river.
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Usually same as [[#Beach|Beach]].
===<div id="Storm surge"> Storm surge </div>===  
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===Spit===
The rise in water-level on an open coast as a result of the combined impact of the wind stress on the water surface, the atmospheric pressure reduction and local topographic features. The storm surge does not include the effect of the astronomical tide. The storm surge at a location is approximately inversely proportional with the water depth in the [[#Offshore zone|offshore zone]]. This implies that shores out to deep oceans will only be exposed to relatively small surges whereas shores out to shallow seas can be exposed to high surges. See: [[Extreme storms]].
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See [[Sand spit]].  
===<div id="Stratification"> Stratification</div>===
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===Storm surge===  
Less dense water layer overlying a water layer of higher density (related to higher salinity, lower temperature or higher suspended sediment concentration).  Density differences in the vertical inhibit turbulent mixing, which causes the interface of the layer to be sharpened. See: [[Salt wedge estuaries]].  
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The rise in water-level on an open coast as a result of the combined impact of the wind stress on the water surface, the atmospheric pressure reduction and local topographic features. The storm surge does not include the effect of the astronomical tide. The storm at a location is in first approximation inversely proportional with the water depth in the [[#Offshore zone|offshore zone]]. This implies that shores out to deep oceans will only be exposed to relatively small surges whereas shores out to shallow seas can be exposed to high surges. See: [[Extreme storms]].
===<div id="Surf beat"> Surf beat</div>===
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===Stratification===
Oscillation of the [[#Wave set-up|wave set-up]] on the foreshore. The oscillation is related to the breaking of [[#Wave group|wave groups]] in the [[#Breaker zone|surf zone]]. See: [[Shallow-water wave theory]].
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Less dense water layer overlying a water layer of higher density (related to higher salinity, lower temperature or higher suspended sediment concentration).  Density differences in the vertical inhibit turbulent mixing, which causes the interface of the layer to be sharpened. See: [[Seawater density]], [[Salt wedge estuaries]].  
===<div id="Surf zone"> Surf zone </div>===
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===Subsidence===
See [[#Breaker zone|breaker zone]].
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Downward motion of the land surface. It is most often related to soil compaction (underground material movement) caused by the removal of water, oil, natural gas, or mineral resources out of the ground by drainage, pumping, fracking, or mining activities. Subsidence can also be caused by natural events such as earthquakes, glacial isostatic adjustment, erosion, sinkhole formation, sediment loading by river deposites, and adding water to fine soils deposited by wind (a natural process known as loess deposits). See also: [[Coastal cities and sea level rise]].
===<div id="Swash"> Swash </div>===
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===[[Surf beat]]===
Wave propagation on the beach, consisting of a decelerating onshore phase (swash or '''uprush''') and an accelerating offshore phase (backwash or '''downrush'''). On [[#Dissipative and reflective beaches|dissipative coasts]] swash processes are dominated by [[#Infragravity waves|infragravity waves]]. See: [[Swash zone dynamics]].
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Long-periodic oscillation of the water line on the beach. The oscillation is related to [[Infragravity waves]] in the [[surf zone]]. See: [[Infragravity waves]], [[Edge waves]], [[Shallow-water wave theory]].
===<div id="Tidal bore"> Tidal bore</div>===
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===[[Surf similarity parameter]]===
Breaking [[#Tidal wave|tidal flood wave]]. Tidal bores occur in shallow funnel-shaped [[#Estuary|estuaries]] with a large tidal range (generally more than 6 m).   
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The surf similarity parameter is defined as <math>\; \xi = \Large\frac{\tan \beta}{\sqrt{H_s/L}}\normalsize , \;</math> where <math>L=\Large\frac{g T^2}{2 \pi}\normalsize</math> is the wavelength at the seaward boundary of the breaker zone and <math> H_s/L</math> the wave steepness at this location. It compares the wave surface slope to the bed slope in the surf zone and represents important features of the hydrodynamics of the surf zone.
===<div id="Tidal channel"> Tidal channel</div>===
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===[[Surf zone]]===
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The surf zone (or '''breaker zone''') is the zone where waves break as a consequence of depth limitation and surf onshore as wave bores. The width of the surf zone varies depending on the wave conditions and water level. The surf zone is narrow and close to the shoreline in a gentle wave climate and can be very wide under storm conditions, extending from the seaward boundary of the [[#Shoreface|upper shoreface]] to the [[#Dunefoot|dunefoot]]. It is estimated that 80 to 90% of the yearly littoral transport takes place within the breaker or surf zone.
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===[[Swash]]===
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Up and down propagation of bores formed after collapse of waves on the beach. Swash is the decelerating uprush phase and backwash is the accelerating downrush phase. On [[#Dissipative and reflective beaches|dissipative coasts]] swash processes are dominated by [[#Infragravity waves|infragravity waves]]. See: [[Swash zone dynamics]].
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===Swash bar===
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The term "swash bar" usually designates a berm that is formed wave uprush on the higher intertidal zone of a [[#Tidal flat|tidal flat]]. See also [[#Beach berm|Beach berm]]
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===Swash zone===
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Zone where wave bores run up and down the [[#Beach face|beach face]].
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===[[Swell]]===
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Waves generated far offshore in the deep sea that propagate onshore. Ocean swell waves have longer wavelengths than locally generated wind waves. The longest waves in the ocean travel faster and dissipate less energy than the shorter waves generated by the same strong wind event. They therefore can reach distant shores whereas the shorter waves cannot.  See [[Waves]].
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===Tidal asymmetry===
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Difference between the ebb and flood phase of the tide: different duration of ebb and flood flow, different strength of ebb and flood currents, different duration of rising tide and falling tide. Tidal asymmetry is mainly caused by the nonlinear dependence of tide propagation on water level variation in shallow coastal systems with complex geometry (e.g., estuaries, lagoons). Tidal asymmetry can also result from the superposition of certain astronomical tidal constituents in estuaries with strong diurnal tides. Tidal asymmetry can strongly influence sediment transport and is an important morphodynamic feedback mechanism for the morphological development of estuaries. It is also plays an important role in the formation of the estuarine turbidity maximum. See [[Tidal asymmetry and tidal basin morphodynamics]], [[Estuarine turbidity maximum]].
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===Tidal bore===
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Breaking [[#Tidal wave|tidal flood wave]] – the ultimate stage of tidal asymmetry. Tidal bores occur in shallow funnel-shaped [[#Estuary|estuaries]] with a large tidal range (generally more than 6 m).  See [[Tidal bore dynamics]].
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===Tidal channel===
 
Seabed incision concentrating the main tidal flow. Tidal channels form naturally in sedimentary environments where tide-induced water motion is stronger than wave-induced water motion.   
 
Seabed incision concentrating the main tidal flow. Tidal channels form naturally in sedimentary environments where tide-induced water motion is stronger than wave-induced water motion.   
===<div id="Tidal creek"> Tidal creek</div>===
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===Tidal creek===
Drainage channel of a [[#Salt marsh|salt marsh]].
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A [[#Tidal channel|tidal channel]] that drains a [[#Salt marsh|salt marsh]].
===<div id="Tidal flat"> Tidal flat</div>===  
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===[[Tidal flat]]===  
Shallow, sandy or muddy part of the [[#Foreshore or Beach face|foreshore]], which is covered and uncovered by the rise and fall of the tide. Muddy tidal flats are also called '''mud flats''' or '''slikke'''. As a rule of thumb, a tidal flat normally develops when the relative tidal range RTR, defined as the ratio between the mean spring tidal range and the annual average [[#Wave|significant wave height]] <math>H_s</math>, is higher than 15.
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Shallow, sandy or muddy area which is covered and uncovered by the rise and fall of the tide. Muddy tidal flats are also called '''mud flats''' or '''slikke'''. As a rule of thumb, tidal flats generally occur in sheltered coastal areas where the relative tidal range RTR, defined as the ratio between the mean spring tidal range and the annual average [[#Wave|significant wave height]] <math>H_s</math>, is about 15 or higher.
===<div id="Tidal inlet"> Tidal inlet</div>===  
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===Tidal inlet===  
The entrance to estuaries on sandy shores that have formed where sand barriers or spits enclose bays. They comprise a [[#Delta|flood and ebb tidal delta]], and a deep narrow throat through which strong currents flow.
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The connection between the sea and a tidal basin (lagoon) or estuary partially shielded by a barrier island, [[sand spit]] or [[#Headland|headland]]. A tidal inlet consists of a narrow deep channel through which strong currents flow, with [[Deltas|flood and ebb tidal deltas]] at the landward and seaward sides.
===<div id="Tidal prism"> Tidal prism</div>===  
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===Tidal prism===  
Volume of water flowing during flood through a [[#Tidal inlet|tidal inlet]], or through a certain section of an [[#Estuary|estuary]] or a [[#Lagoon|tidal lagoon]].  
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Volume of water flowing during flood through a [[#Tidal inlet|tidal inlet]], or through a cross-section of an [[#Estuary|estuary]] or a [[#Lagoon|tidal lagoon]].  
===<div id="Tidal range"> Tidal range</div>===  
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===Tidal range===  
Water level difference between high water and low water, i.e. twice the '''tidal amplitude'''. The tidal range changes from tide to tide depending on the positions of moon and sun relative to the earth; the most important change is the fortnightly variation from '''spring tide''' to '''neap tide'''.  
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Water level difference between high water and low water, i.e. twice the '''tidal amplitude'''. The tidal range changes from tide to tide depending on the positions of moon and sun relative to the earth; the most important change is the fortnightly variation from '''spring tide''' to '''neap tide'''. See [[Ocean and shelf tides]].  
===<div id="Tidal ridge"> Tidal ridge</div>===  
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===Tidal ridge===  
Sand ridge with a length of several tens of kilometers and height of a few tens of meters, produced by tidal currents on a [[#Continental shelf|shelf sea]]. Sand ridge fields consist of a number of tidal ridges with a spacing of the order of 5 km. See: [[Sand ridges in shelf seas]].
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Submarine sand ridge with a length of several tens of kilometers and height of a few tens of meters, generated by the nonlinear interaction of tidal currents with the seabed on the [[#Continental shelf|shelf sea]]. Sand ridge fields consist of a number of tidal ridges with a spacing of the order of 5 km. See: [[Sand ridges in shelf seas]].
===<div id="Tidal wave"> Tidal wave</div>===  
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===Tidal wave===  
 
The wave associated with tidal motion. The term "tidal wave" is also frequently used as a popular expression for an unusually high and destructive water level along a shore, thus including the combined effect of astronomical and meteorological surges.  
 
The wave associated with tidal motion. The term "tidal wave" is also frequently used as a popular expression for an unusually high and destructive water level along a shore, thus including the combined effect of astronomical and meteorological surges.  
===<div id="Tide or Astronomical tide "> Tide or Astronomical tide </div>===  
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===Tide===  
The astronomical tide is generated by the rotation of the earth in combination with the varying gravitational impact on the ocean of the sun, the moon and the planets. These phenomena cause predictable and regular oscillations in the water level, which is referred to as the tide. The astronomical tide at a specific location can be predicted and is published in Tidal Tables. See: [[Tidal motion in shelf seas]].
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The tide (more precisely, the '''astronomical tide''') is the large-scale water motion generated by the rotation of the earth in combination with the varying gravitational influence on the ocean of celestial bodies, especially the moon and the sun. These phenomena cause predictable and regular oscillations in the water level, which are referred to as the tide. The astronomical tide at a specific location can be predicted and is published in Tidal Tables. See: [[Ocean and shelf tides]], [[Tidal motion in shelf seas]]. The term 'tide' is sometimes used for the combined effect of astronomical tide and wind-driven set-up or set-down of the sea level (including [[#Storm surge|storm surges]]). 
===<div id="Transgression"> Transgression</div>===
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===Transgression===
Flooding of land by the sea related to relative [[#Sea-level rise|sea-level rise]]. Transgression implies [[#Coastline retreat|coastline retreat]].
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Flooding of land by the sea related to relative [[sea level rise]]. Transgression implies [[#Coastline retreat|coastline retreat]].
===<div id="Tsunami"> Tsunami</div>===
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===[[Tsunami]]===
Wave (or group of waves) generated by a subsea earthquake. Tsunamis propagate very fast over the ocean with very few energy loss due to the great ocean depth (see: [[#Propagation speed|propagation speed]]). In nearshore waters the amplitude increases dramatically (up to a factor 10) due to [[#Shoaling|shoaling]].   
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Long waves caused by a strong local disturbance of the water mass. The most important generation mechanisms are subsea earthquakes and subsea slides of unconsolidated seabed slopes. Tsunamis propagate very fast over the ocean with very few energy loss due to the great ocean depth. Tsunamis generally consist of a few successive waves with wavelengths typically much larger than the wavelength of wind-generated waves and much smaller than the wavelength of tidal waves. In nearshore waters the amplitude increases dramatically due to [[shoaling]], see [[Tsunami]].   
===<div id="Turbidity maximum"> Turbidity maximum</div>===
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===[[Estuarine turbidity maximum|Turbidity maximum]]===
Convergence zone of suspended sediment transport in an [[#Estuary|estuary]], where turbidity levels are high due to high suspended sediment concentrations. Upstream (landward) transport of fine suspended sediment in an estuary is possible due to [[#Estuarine circulation|estuarine circulation]] and tidal asymmetry (maximum flood current stronger than maximum ebb current). This produces a maximum in the suspended sediment concentration just downstream of the zone where the influence of river discharge on sediment transport becomes dominant. Fine sediments in the turbidity maximum zone settle to the bed in periods where currents are small (slack tide, neap tide), which may result in the formation of [[#Mud|fluid mud layers]]. High turbidity often causes oxygen depletion and mortality of estuarine organisms. It also enhances sedimentation of [[Tidal flat|tidal flats]] and harbours. See: [[Dynamics of mud transport]].
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Convergence zone of suspended sediment transport in an [[#Estuary|estuary]], where turbidity levels are high due to high suspended sediment concentrations. Upstream (landward) transport of fine suspended sediment in an estuary is possible due to [[estuarine circulation]] and tidal asymmetry (maximum flood current stronger than maximum ebb current). This produces a maximum in the suspended sediment concentration just downstream of the zone where the influence of river discharge on sediment transport becomes dominant. Fine sediments in the turbidity maximum zone settle to the bed in periods where currents are small (slack tide, neap tide), which may result in the formation of [[#Mud|fluid mud layers]]. High turbidity often causes oxygen depletion and mortality of estuarine organisms. It also enhances sedimentation of [[Tidal flat|tidal flats]] and harbours. See: [[Estuarine turbidity maximum]], [[Dynamics of mud transport]].
===<div id="Turbulence"> Turbulence</div>===
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===Turbulence===
 
Irregular flow pattern of individual fluid parcels related to small-scale flow instability, see [[#Boundary layer|Turbulent boundary layer]]. Turbulence plays a major role in mixing processes and in energy dissipation. See: [[Transport and dispersion of pollutants, nutrients, tracers in mixed nearshore water]], [[Currents and turbulence by acoustic methods]].
 
Irregular flow pattern of individual fluid parcels related to small-scale flow instability, see [[#Boundary layer|Turbulent boundary layer]]. Turbulence plays a major role in mixing processes and in energy dissipation. See: [[Transport and dispersion of pollutants, nutrients, tracers in mixed nearshore water]], [[Currents and turbulence by acoustic methods]].
===<div id="Wave"> Wave</div>===
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===[[Waves|Wave]]===
The term "wave" designates in most cases surface water waves generated by wind (other types of waves are explicitly referred to as [[#Tidal wave|tidal wave]], [[#Tsunami|tsunami]] wave, etc.). A wave field is generally a superposition of waves of different height, period and direction that can be described by a '''wave spectrum'''. A unidirectional wave field is often characterised by the '''significant wave height''' <math>H_s</math> (representing approximately the mean [[#Wave height|wave height]] of the highest third of the waves) and the '''spectral peak period''' <math>T_p</math> (wave period with the highest energy).  See: [[Statistical description of wave parameters]]. Coasts situated on the open ocean are mainly subjected to long-period '''swell waves''', which are generated far away at the ocean and propagate to the coast with minor energy losses. Coasts situated on inland seas are mainly subjected to locally generated short-crested waves, also called "sea", see [[Waves]].
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The term "wave" designates in most cases surface water waves generated by wind (other types of waves are explicitly referred to as [[#Tidal wave|tidal wave]], [[#Tsunami|tsunami]] wave, etc.). A wave field is generally a superposition of waves of different height, period and direction that can be described by a '''wave spectrum'''. A unidirectional wave field is often characterised by the '''significant wave height''' <math>H_s</math> (representing approximately the mean [[#Wave height|wave height]] of the highest third of the waves) and the '''spectral peak period''' <math>T_p</math> (wave period with the highest energy).  See: [[Statistical description of wave parameters]]. Coasts situated on the open ocean are mainly subjected to long-period [[swell]] waves. Coasts situated on inland seas are mainly subject to locally generated short-crested waves, also called "sea". See [[Waves]] and [[Shallow-water wave theory]].
===<div id="Wave breaking"> Wave breaking</div>===
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===Wave breaking===
Waves start breaking (by spilling or plunging) when entering shallow water, where the depth is smaller than one or two times the [[#Wave height|wave height]]. Waves may reform in the [[#Breaker zone|surf zone]], but remain depth-limited by spilling or by plunging a second time, until final collapse and [[#Swash|uprush]] on the beach. See: [[Shallow-water wave theory]].  
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Wave breaking is the ultimate stage of wave deformation due to strong nonlinearity of the wave propagation process when waves enter shallow water (water depth less than half the wavelength). Waves start breaking (by surging, collapsing, plunging or spilling) where the still water depth is smaller than one or two times the [[#Wave height|wave height]]. Waves may reform in the [[surf zone]], but remain depth-limited by spilling or by plunging a second time, until final collapse and [[Swash|uprush]] on the beach. See: [[Wave transformation]], [[Shallow-water wave theory]].  
===<div id="Wave energy"> Wave energy</div>===
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===Wave energy===
Energy carried by waves when [[#Propagation speed|propagating]]. The wave energy <math>E</math> is proportional to the square of the [[#Wave height|wave height]] <math>H</math>  (formula: <math>E=g \rho H^2 / 8</math>).
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Energy carried by waves when [[#Propagation speed|propagating]]. The wave energy <math>E</math> is proportional to the square of the [[#Wave height|wave height]] <math>H</math>  (formula: <math>E=g \rho H^2 / 8</math>). For irregular waves, <math>H</math> is the root mean square wave height <math>H_{rms}</math>, see [[Statistical description of wave parameters]].  
===<div id="Wave group"> Wave group</div>===
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===[[Wave group]]===
Incident waves generally arrive in groups, corresponding to the superposition of short-wave trains with slightly differing wave lengths and frequencies. Wave groups generate [[#Infragravity wave|infragravity waves]] with the same group wavelength and period, by non-linear interaction. Wave groups also cause [[#Surf beat|surf beat]]. See: [[Shallow-water wave theory]], [[Infragravity waves]].  
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Incident waves generally arrive in groups, corresponding to the superposition of incident waves with slightly differing wave lengths and frequencies that are present in the wave spectrum. Wave groups generate [[infragravity waves]] with the same group wavelength and period, by non-linear interaction. Wave groups also cause [[surf beat]]. See: [[Shallow-water wave theory]], [[Infragravity waves]].  
===<div id="Wave height"> Wave height</div>===
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===Wave height===
The water level difference between wave trough and wave crest, or twice the wave amplitude.  
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The water level difference between wave trough and wave crest, or twice the wave amplitude. In an irregular wave field, successive incident waves have different amplitudes and phases. In deep water the wave height distribution often follows approximately a Rayleigh distribution. However, this is not the case in the [[surf zone]] where the wave height is limited by the water depth. See [[Statistical description of wave parameters]].
===<div id="Wave run-up"> Wave run-up</div>===
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===[[Wave propagation]]===
The sum of [[#Swash|swash]] and [[#Wave set-up|wave set-up]]. Wave run-up is an important factor in the design of coastal protection structures and is a dominant process leading to the erosion of coastal dunes.
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Progression and transformation of waves in time and space.
===<div id="Wave set-up"> Wave set-up</div>===
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*The speed <math>c</math> of a wave propagating without frictional losses in deep water is given by <math>c \approx \sqrt{g/k} = g/\omega</math> where <math>g</math> is the gravitational acceleration, <math>k=2 \pi / \lambda</math> the wave number, <math>\lambda</math> the wavelength and <math>\omega=kc</math> the angular frequency. Deep water means: still water depth <math>h</math> much larger than <math>1/k</math>. The dependency of the propagation speed on frequency causes [[Dispersion (waves)|wave dispersion]].
Water level elevation at the foreshore related to wave breaking in the surf zone. Wave set-up is proportional to the [[#Wave height|wave height]] at the breaker line. As a rule of thumb, wave set-up is of the order of 20% of the offshore significant wave height. See: [[Shallow-water wave theory]].  
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*In shallow water (depth <math>h</math> much smaller than <math>1/k</math>), the wave propagation speed is proportional to the square root of the water depth <math>h</math>  (formula: <math>c \approx \sqrt{gh}</math>), thus not depending on the wave frequency. 
 +
*In shallow water, wave propagation is a strongly nonlinear process, leading to wave transformation and breaking.
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*A [[Wave group|wave group]] propagates at a smaller speed <math>c_g</math> than the constituent short waves. Wave energy propagates at the speed of the wave group.
 +
See: [[Shallow-water wave theory]].
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===[[Wave run-up]]===
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The maximum onshore elevation reached by a wave running on the beach, relative to the water level in the absence of waves. It is the sum of [[Swash|swash uprush]] and [[#Wave setup|wave set-up]]. Wave run-up is an important factor in the design of coastal protection structures and is a dominant process leading to the erosion of coastal dunes. See also [[Wave run-up]], [[Swash zone dynamics]], [[Tsunami]].
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===[[Wave set-up]]===
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Elevation of the mean water level at the shoreline due to wave breaking in the surf zone. The wave set-up is proportional to the [[wave height]] at the breaker line. As a rule of thumb, the wave setup is of the order of 20% of the offshore significant wave height. See: [[Shallow-water wave theory# Wave set-down and set-up|Wave set-down and set-up]].  
 
   
 
   
  
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[[Category:Theme 5]]
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[[Category:Definitions]]

Revision as of 15:14, 13 June 2021



This article gives an overview of terminology frequently used in the Coastal Wiki. Many definitions are derived from Mangor et al. 2017 [1]. Terms related to the coastal profile are illustrated in the figure below.



Fig. 1. Definition of coastal sub-zones, adapted from the Shore Protection Manual, 1984[2]


Accretion or Aggradation

Growth (vertical and/or horizontal) of morphological structures (beach, bar, dune, sand bank, tidal flat, salt marsh, tidal channel, etc.) by sedimentation.

Active coastal zone

The active coastal zone (also called active coastal profile) is the cross-shore coastal zone that is highly dynamic, with up and down redistribution of sand by the action of tides, waves and wind. It extends from the closure depth up to a fixed land boundary (rock, cliff, seawall, sea dike). In the case of a dune coast the front dune is part of the active coastal zone. See: Active coastal zone.

Angle of incidence

The angle between the wave propagation direction and the normal to the coastline or the angle between the wave front and the coastline (often denoted by the symbol [math]\alpha[/math] or [math]\theta[/math]). When waves enter shallow water, the wave propagation direction tends to become perpendicular to the depth contours, by refraction. See: Shallow-water wave theory, Wave transformation. The deep water angle of incidence is often denoted [math]\alpha_0[/math].

Armouring

  1. Manmade structures such as seawalls, revetments, bulkheads, geotubes, etc. intended to prevent damage of properties situated on the coast;
  2. The natural process of removing fine sediment from the beach or seabed top layer, leaving coarse material behind, thus leading to a more erosion-resistant residual top layer. This process may occur at places where beach or seabed material is a mixture of fine and coarse sediments (so-called graded sediment).

Astronomical tide

The tidal levels and water motion which would result from Earth's rotation and gravitational effects of, in particular, the Earth, Sun and Moon, without any atmospheric influences. See also: Tide

Avulsion

The sudden abandonment of an existing tidal channel in favour of a newly formed channel. Channel avulsion is a common process in tidal deltas.

Backshore

The part of the beach lying between the beach face and coastline. The backshore is dry under normal conditions; it is often characterised by berms. Vegetation is generally sparse or absent. The backshore is only exposed to waves under extreme events with high tide and storm surge.

Bar

Elongated sand body created by (tidal) currents or by waves . Bars in estuaries and tidal lagoons develop naturally in flow convergence zones, often in relation with channel meandering. Estuarine bars also occur where ebb- and flood-dominated channels meet. Bars that partially block the openings to minor streams and lagoons are mainly due to littoral drift; these bars are generally referred to as spits. Wave action is responsible for the development of breaker bars, beach berms and swash bars. Bars can raise above the high water level, but they are often intratidal or subtidal.

Bathymetry

Mapping of the seafloor depth with respect to the mean water level. The term is also used for the description of seafloor topography or coastal morphology. The depths are almost always derived indirectly by measuring the time required for a signal to travel from a transmitter, to the bottom, and back to a receiver.

Beach

The beach (or shore) zone of unconsolidated material that extends from the mean low water line to the place where there is a marked change in material or physiographic form (e.g. dunefoot), or to the line of permanent vegetation (the effective limit of storm waves and storm surge), i.e. to the coastline. The beach or shore can be divided in the beach face and the backshore. Often a distinction is made between dissipative and reflective beaches.

Beach berm

A beach berm is a nearly horizontal shore parallel ridge formed on the beach due to the landward transport of the coarsest fraction of the beach material by the wave uprush. There may be several beach berms and in some cases no berms. Under normal conditions a beach berm is formed on the upper part of the beach face, and over the backshore during severe events. Berms can also form on the higher intertidal zone of a tidal flat; these berms are generally called "swash bars". Beach berms are sometimes artificially reinforced as coastal protection measure.

Beach cusps

Regularly spaced shoreline structures (spacing typically between a few meters and a few tens of meters) consisting of small embayments between protruding horns. They are a common feature of reflective beaches. See: Beach Cusps.

Beach face

Beach face (also called foreshore) is the zone between the mean low water (MLW) and the seaward beach berm, which is equivalent to the upper limit of wave run-up at high tide, see Fig. 1. The beach face is the part of the shore/beach which is wetted due to the varying tide and swash under normal conditions. This means that the beach face in morphological terms extends further up on the beach than the intersection between the mean high water (MHW) and the coastal profile (MHW line). However, for practical reasons the upper delineation of the beach face is often defined as the intersection between the MHW line and the coastal profile, which is identical to the usual definition of the shoreline. On the lower part of wide intertidal beaches several intertidal bars (also called beach ridges) can be present, related to onshore moving nearshore sandbars. The depressions between these intertidal bars are called runnels.

Beach fill

The supply of beach sand for the construction of an artificial beach.

Beach nourishment

Beach nourishment is the supply of sand to the beach to increase the recreational value and/or to compensate for the effect of shore erosion by feeding sand on the beach.

Bed forms

The seafloor is seldom flat, but generally undulated by the interaction with currents and waves . Undulated bedforms exist over a large range of spatial scales, from centimeters up to kilometers, see: Wave ripples, Wave ripple formation, Sand ridges in shelf seas, Stability models. The smallest bedforms play an important role in the friction exerted by the seabed on water motion, see Boundary layer, Bedforms and roughness, Bed roughness and friction factors in estuaries, Wave ripples, Wave ripple formation.

Bedload

Bedload transport refers to sediment transport by rolling and saltating sediment grains over the seabed. Bedload transport is the dominant sediment transport mode when the flow velocities (currents and wave-orbital velocities) are above the critical velocity for setting bed particles in motion (in the order of 0.2-0.4 m/s for sandy sediments), but insufficient for bringing sediment particles in suspension. Bedload transport occurs for non-cohesive medium-coarse sediments and is associated with the formation of bed ripples and dunes. The migration of these bedforms yields an estimate for the bedload transport. See: Sand transport.

Benthos

Organisms living on or in the seabed, including vegetation.

Boundary layer (turbulent)

The fluid layer where momentum and energy are dissipated as a result of friction exerted by the seafloor or a nearby hard boundary. In the boundary layer, fluid momentum is dissipated through transfer from the large-scale flow pattern in a cascade process to increasingly smaller turbulent flow structures. The large-scale flow profile in the turbulent boundary layer has a logarithmic profile. The thickness of the turbulent boundary layer corresponds to the size of the largest turbulent eddies generated by friction at the seafloor. Because the development of the turbulent boundary layer takes time, the boundary layer thickness for slowly varying currents is much greater than for rapidly varying currents. The boundary layer thickness for steady flow and tidal flow is typically of the order of 10-50% of the water depth, whereas the boundary layer thickness for wind-driven waves is only a few centimeters. Hence, steady flow and tidal flow experience much stronger friction than propagating wind-driven waves. See: Bed forms, Wave ripples.

Breaker zone

See surf zone.

Breaker bar

Breaker bars, also called nearshore sandbars, are elongated (approximately) shore parallel bodies of sand or gravel built in the surf zone due to the action of breaking waves and cross-currents. There can be several rows of bars. Breaker bars are very mobile formations, which tend to be in unstable equilibrium with the wave climate and tide conditions, which means that they are constantly changing. The overall tendency is that the bars are moving seawards during storm wave conditions and landwards during conditions dominated by smaller waves and swell. At intervals there are gaps in the breaker bars formed by rip currents. See Nearshore sandbars.

Breaker index

The ratio of wave height and still water depth at the shoreface location where incident waves start breaking. See Breaker index.

Breakwater

A structure built for reducing wave activity in the waters at the leeside. It can be linked to the shore or it can be positioned offshore. A common type is the detached breakwater. This is a structure approximately parallel to the coast, built inside or outside the surf zone. The main purpose of detached breakwaters is either to protect a harbor entrance or a ship wharf from wave action or to reduce wave activity at the beach. See: Application of breakwaters, Detached breakwaters, Detached shore parallel breakwaters, Floating breakwaters, Stability of rubble mound breakwaters and shore revetments.

Buoyancy

Upward force experienced by a body of lower density (water body of lower salinity, higher temperature, for example) than the surrounding fluid.

Chenier

An accretionary feature consisting of a long, low lying, narrow strip of (gravelly) sand, typically up to 3 m high and 40 to 400 m wide, often shelly, deposited in the form of wave-built beach ridge on a swampy, deltaic, or alluvial coastal plain of fine sediment.

Closure depth

There are two closure depths: (1) the depth [math]h_{out}[/math] at the seaward limit of the lower shoreface, beyond which no significant wave-induced sand transport takes place; (2) the depth [math]h_{in}[/math] marking the transition between the lower shoreface (wave shoaling zone) and upper shoreface (wave breaking zone). See Closure depth, shoreface and Shoreface profile.

Coast

The strip of land that extends from the coastline inland to the first major change in the terrain features, which are not influenced by coastal processes. The main types of coastal features are dunes, cliffs and low-lying areas, possibly protected by dikes or seawalls.

Coastal area

The land and sea areas bordering the shoreline.

Coastal cell

A coastal cell (or littoral cell or sediment cell) is a coastal compartment that contains a closed cycle of sedimentation including sources, transport paths, and sinks. The cell boundaries (often corresponding to headlands or jetties) delineate the geographical area within which the budget of sediment is balanced, providing the framework for the quantitative analysis of coastal erosion and accretion.

Coastal development

Any activity likely to alter the physical nature of the coastal zone in any way, including construction of buildings and works, the deposit of waste or other material from outfalls, vessels or by other means, the removal of sand, sea shells, natural vegetation, sea grass and other substances, dredging and filling, land reclamation and mining or drilling for minerals, but excluding fishing activities.

Coastal erosion

Coast erosion is the process of wearing away material from the coastal profile due to imbalance in the supply and export of material from a certain section. Distinction must be made between incidental coastal erosion and ongoing coastal erosion.

Coastal hinterland

The land that extends landward of the coast and which is not influenced by coastal processes.

Coastal morphodynamics

The mutual interaction of coastal morphology with hydrodynamic agents (tides, currents, waves). This interaction takes place through sedimentation, erosion and sediment transport processes. Tides, currents and waves adapt to constraints imposed by the morphology of a coastal system (e.g., delta, estuary, beach, etc.). The morphology of a coastal system adapts to the tides, currents, waves to which it is exposed. This mutual adaptation, which is always highly nonlinear, generates morphological patterns, such as channel meanders, tidal flats, ebb tidal deltas, nearshore sandbars, beach berms, sand ridges, ripples, etc. As a result, the large-scale coastal morphology develops into a slowly evolving morphodynamic equilibrium state in which smaller morphological patterns evolve in a quasi-cyclical (usually non-deterministic) manner at much smaller timescales.

Coastal morphology

Coastal morphology (or coastal geomorphology or morphology) is the (study of the) shape and structure of coastal systems or subsystems. For example: the morphology of a delta, the morphology of an estuary, the morphology of a beach, the morphology of a bedform. The meaning of the Greek word "morphè" is form or shape. See also: Characteristics of sedimentary shores, Classification of sandy coastlines, Morphology of estuaries.

Coastal profile

The cross-shore profile of the active coastal zone. See also: Shoreface profile.

Coastal protection

Three different protection/defence definitions are used as follows:

Coastal zone

General, wide planning-oriented characterisation: The interface between land and sea, defined as the part of the land affected by its proximity to the sea (influence of marine processes), and the part of the sea affected by its proximity to the land (influence of terrestrial processes).

Coastal zone management (CZM)

Coastal zone management is the process aiming to balance the different interests in coastal areas, related to safety, environment, economy, social equity and esthetic and cultural values. Coastal area planning and coastal engineering (hard or soft measures) are major components of coastal zone management, together with legislation, administration, communication, education, monitoring, research. Because of this comprehensive scope the term Integrated coastal zone management (ICZM) is more widely used than CZM. The dynamic nature of the coastal zone is a highly challenging aspect of coastal zone management. See also: Integrated Coastal Zone Management (ICZM), Some definitions of Integrated Coastal Zone Management (ICZM), The Integrated approach to Coastal Zone Management (ICZM), Spatial Planning and Integrated Coastal Zone Management, Policy instruments for integrated coastal zone management, Shoreline management, and other articles in the category Integrated coastal zone management

Coastline

The boundary between land and sea, a proxy of the instantaneous shoreline for the assessment of erosion or accretion trends. See: Coastline.

Coastline retreat

Landward shift of the coastline caused by a long-term erosional trend or by sea-level rise.

Continental shelf

The continental shelf (or shelf sea) is the continental border which is submerged in relatively shallow sea (water depths typically less than 200 m). The continental shelf extends from the coastline of a continent to a drop-off point called the shelf break. From the break, the shelf descends toward the deep ocean floor in what is called the continental slope. Water motion, water quality and ecosystem of shelf seas are strongly influenced by the adjacent ocean, see Shelf sea exchange with the ocean, Continental shelf habitat.

The legal definition of a continental shelf is different from the geographic one. According to the UN Convention on the Law of the Sea, every nation has a continental shelf extending no more than 200 nautical miles from the nation's coastline. See: Legislation for the sea.

Coriolis

The acceleration experienced by a current due to earth rotation, see: Coriolis acceleration.

Deep water

Water too deep for waves to be affected by the seafloor; typically taken as half the wavelength, or greater.

Delta

The fan-shaped mouth of a river or a tidal basin, formed by several distributary channels. River deltas are formed when the supply of sediments to the coast by a river is faster than they are dispersed by waves, tides and the associated currents. They are the result of depositional and erosional processes under the influence of currents, waves and tides. Because of their different morphologies, often a distinction is made between river-dominated deltas, wave-dominated deltas and tide-dominated deltas. See: Morphology of estuaries, Wave-dominated river deltas.

Flood tidal deltas are sedimentary bodies deposited by flood currents. Ebb-tidal deltas are sedimentary bodies deposited by ebb currents. Flood deltas and ebb-tidal deltas are generally present at the inshore and offshore sides (respectively) of tidal inlets of estuaries and tidal lagoons.

Diffraction

Process by which energy of a wave is transmitted, radiated and dissipated laterally when reaching an obstacle such a breakwater and propagates into its sheltered region.

Dispersion

  1. The passive dispersal of dissolved substances in the marine or estuarine environment. Dispersion is the overall mixing effect of all hydrodynamic processes including turbulence, flow circulations and gradients in current velocity. See: Seawater intrusion and mixing in estuaries, Transport and dispersion of pollutants, nutrients, tracers in mixed nearshore water, Shelf sea exchange with the ocean.
  2. Wave field transformation due to the dependence of propagation speed on wave frequency. See Dispersion (waves), Shallow-water wave theory.

Dissipative and reflective beaches

Dissipative beaches have typically gentle coastal profiles; they are subjected to energetic short-crested waves, which are strongly damped in the nearshore zone. Dissipative beaches have medium to large intertidal zones which consist of fine (sandy or muddy) sediment. Reflective beaches have typically steep slopes and are subjected to low-energy swell waves. An intertidal zone is almost absent and the beach consists mainly of coarse (sandy or gravelly) sediment. Beach types can be characterised by the so-called ' Dean parameter ' [math]\Omega=H_0/(w_s T_p)[/math], where [math]H_0[/math] is the deep-water wave height, [math]w_s[/math] the mean fall velocity of beach sediment and [math]T_p[/math] the peak spectral wave period. Reflective beaches correspond to [math]\Omega \lt 1[/math] and dissipative beaches to [math]\Omega \gt 6[/math]. See Shoreface profile and Characteristics of sedimentary shores.

Dunes

  1. The term 'dunes' generally indicates subaerial dunes. These dunes are ridges or moulds of loose, wind-blown sand (fine to medium) forming on the backshore and forming the coastal features at certain locations. Dunes are more or less vegetated. Dunes are active coastal form elements acting as a flexible sand reservoir. At coasts subject to structural coastal erosion they are moving backwards in parallel with shoreline retreat. Dunes act as a kind of flexible natural protection against erosion and flooding, see Dune erosion. If the vegetation is damaged by too much traffic or grazing etc. the integrity of the dunes may be endangered.
  2. The term 'dunes' is also used for subaqueous dunes, which are usually called sandwaves in shelf seas. Subaqueous dunes are bed forms induced by the interaction of the seabed with (mainly tidal) currents. Sandy seabeds are often covered with dune fields in regions where the maximum tidal current velocity is in the range 0.5-1.5 m/s. Dune spacing (more than 10 m and less than 1000 m) depends mainly on water depth. Dunes can reach a height of 10-50% of the water depth; high dunes present a risk for navigation.

Dunefoot

Transition between the backshore beach and the much steeper dune.

Ebb and flood tides

The following two definitions of ebb and flood can be found in the literature:

  1. Ebb is the tidal phase during which the tidal current is flowing seaward (ebb current) and flood is the tidal phase during which the tidal current is flowing inland (flood current);
  2. Ebb is the tidal phase during which the water level is falling and flood the tidal phase during which the water level is rising.

The two definitions do not coincide. The first definition is more usual for tidal inlet systems: estuaries, tidal lagoons and tidal rivers; the second definition is more usual for the open coast.

Edge wave

Obliquely incident waves trapped to the shore by wave refraction and reflection. Non-breaking long-period waves (infragravity waves) that are not strongly dissipated in the nearshore zone cannot escape to deep water after reflection but continue travelling along the shore.

Environmental impact assessment (EIA)

A written analysis of the predicted environmental consequences of a proposed development activity, including

  • a description of the avoidable and unavoidable adverse environmental effects (in conjunction with the cumulative effect of other human interventions);
  • a description of alternatives to the activity which might be less harmful to the environment, together with the reasons why such alternatives were rejected;
  • a description of any required irreversible or irretrievable commitments of resources required by the proposed development activity.

Estuary

The transition zone between the riverine and the marine environment. A usual definition is: a semi-enclosed coastal body of water, which has a free connection with the open sea, and within which sea water is measurably diluted with freshwater derived from land drainage. Strong tides intrude in general much further upstream than seawater. From a morphological and sedimentary point of view it is therefore more logical to consider as upstream estuarine boundary the location where tidal discharges become much smaller than river discharges, instead of the seawater intrusion limit. See: Seawater intrusion and mixing in estuaries, Morphology of estuaries.

Estuarine circulation

Residual flow pattern in an estuary driven by density differences between fluvial water and seawater. See: Estuarine circulation, Salt wedge estuaries.

Excavation

See Mining

Fetch

Length in the wind direction of the marine area where water waves are generated by wind.

Fluid mud

Fluid mud is a high-concentration colloidal suspension of fine sediment particles (< 63 µm, with often a high percentage of clay < 4 µm). It is formed by settling of mudflocs into a near-bottom suspended layer at a higher rate than the dewatering rate, or by fluidization and/or liquefaction of an underconsolidated mud bottom. See Fluid mud.

Friction

Shear stresses generated by the seabed (sediment grains, bedforms) and by flow obstacles, causing loss of fluid momentum. The shear stresses are transmitted to the flow via the turbulent boundary layer. See: Bed forms, Bed roughness and friction factors in estuaries, Bedforms and roughness

Foreshore

Same as beach face.

Graded sediment

A sediment bed composed of a mixture of fine and coarse grained sediment particles.

Gravel beach

Beach built of granular material with a size larger than 1 mm: very coarse sand (>1 mm), gravel (2-4 mm), pebbles (4-64 mm) and cobbles (>64 mm), see Coastal and marine sediments. Beach material often originates from erosion of nearby cliffs or is supplied by gravel rivers draining nearby mountains. Gravel beaches have steep slopes and occur on coasts exposed to strong wave action. Cusp patterns are a common beach feature. See: Gravel Beaches.

Groyne or groin

A straight structure perpendicular to the shoreline. Groynes work by blocking (part of) the littoral drift. They trap/maintain sand on their updrift side and cause erosion on the downdrift side. Groynes can have special shapes and they can be emerged, sloping or submerged, they can be single or in groups, the so-called groyne fields. Groynes are normally built as rubble mound structures, but they can also be constructed in other materials, such as concrete units, timber, etc. See: Groynes, Groynes as shore protection, Deteriorated groynes.

Headland

Land mass with a considerable elevation that borders beaches. Headlands form the boundaries to sediment cells, compartmentalising sand transport along the shore, and reducing sand exchange between adjacent beaches.

Artificial headlands are smooth structures built from the coastline over the beach and some distance out on the shoreface. They work by blocking (part of) the littoral transport. A headland combines the effects of groynes and detached breakwaters and at the same time, minimises some of the disadvantages of groynes and breakwaters – see Modified breakwaters and headlands.

Infragravity waves

Ocean surface waves with a period of typicallly 30-300 s. They arise in particular through non-linear interactions within wave groups in shallow water. They play an important role in beach dynamics of dissipative coasts because their amplitude increases shoreward, relative to the breaking short waves. See: Infragravity waves.

Internal waves

Waves on the interface of fluid layers with different densities. Internal waves can be very large when the density difference between the fluid layers is small. Breaking of internal waves contributes to mixing of the layers and destruction of the layer structure.

Intertidal zone

Area which is dry at low water (LW) and submerged at high water (HW), where LW and HW refer to mean spring tide. The beach face, tidal flats and (parts of) salt marshes are intertidal zones.

Jetty

  1. Breakwater protecting a harbour entrance channel from wave action (also called harbour mole);
  2. Structure (often a bridge) connecting an offshore ship mooring to the coast.

Lagoon

Area of relatively shallow water situated in a coastal environment, separated from the open marine conditions by a natural barrier (a sand spit, a barrier island or a coral reef), but with an access to the sea. One may distinguish between microtidal and macrotidal lagoons. Examples of microtidal lagoons are Great South Bay and Pamlico Sound at the US Atlantic coast. Examples of macrotidal lagoons (also called tidal lagoons) are the Wadden Sea at the Dutch-German-Danish North Sea coast and the Bassin d'Arcachon at the French Atlantic coast. Tidal lagoons are distinct from microtidal lagoons by the existence of deep tidal inlets and large tidal flats. See also: Morphology of estuaries.

Littoral cell

Same as coastal cell.

Littoral drift

Littoral drift or longshore sediment transport is the term used for the longshore transport of non-cohesive sediments, i.e. mainly sand, along the upper shoreface due to the action of breaking waves and longshore currents. Formulas for the longshore sediment transport are given in: Littoral drift and shoreline modelling; see also Coastal Hydrodynamics And Transport Processes.

Littoral zone

In marine ecosystems the shore area or intertidal zone, where periodic exposure and submersion by tides is normal.

Longshore current

The longshore current or nearshore current is the dominating current in the nearshore zone and is running parallel to the shore. The longshore current is generated by the shore-parallel component of the stresses associated with the breaking process for obliquely incoming waves , the so-called radiation stresses, and by the surplus water which is carried across the breaker zone towards the shoreline. See: Shallow-water wave theory.

Longshore sediment transport

Same as Littoral drift.

Management unit (MU)

A management unit is a coastal stretch with coherent characteristics in terms of both natural coastal processes and land use. The MU is used as boundary for Shoreline Master Plans.

Marine regression

Coastal extension due to a falling relative sea level.

Meandering

Natural propensity of a flow to scour the outer bend of a channel. When a channel meander becomes very large a cutoff channel (a so-called channel chute) is often formed, leading to avulsion of the meander.

Mining

Mining (or excavation) is the mechanical removal of consolidated soil or unconsolidated material (aggregates like sand, gravel, shells) from seabed, beach or dunes.

Mitigation

Measures aimed at countering, alleviating or partially obviating the adverse consequences of threatening developments or events that have a human or natural cause.

Model

Physical or mathematical representation of nature, for studying or predicting coastal behaviour; see Modelling coastal hydrodynamics.

  • Physical models. These models copy salient features of nature at a reduced scale in a laboratory setting. Scale effects are an important issue for the translation of observed model results to the natural scale. Major scale effects generally arise for the representation of phenomena influenced by friction, by sediment transport (including sediment erosion and deposition) and by biota. See Scaling Issues in Hydraulic Modelling.
  • Mathematical models. These models solve in one way or another the governing hydrodynamic (and/or morphodynamic) equations . They exist in many different types, see for example Estuarine morphological modelling. Most common types are: Analytical models, Numerical process-based models, Behaviour-based models, Stochastic models, Data-driven models, Particle-based models and Cellular models. Analytical models are based on explicit solutions of the governing equations, which are strongly simplified to retain only those features which are most pertinent to the studied phenomena. Numerical process-based models describe nature on a discretised grid, retaining all physical features relevant for a reliable and accurate representation of the studied phenomena; the governing equations are solved numerically for successive discrete time steps, see Process-based morphological models. Behaviour-based models (also called Aggregate-scale models) consider the coastal system as an assembly of interacting subsystems and solve the governing equations numerically for the interactions at system level, whereas empirical relationships are used for representing the dynamics at subscale levels; see: Behaviour-based models. Stochastic models are process-based models which use probability distributions for certain input data for taking into account natural fluctuations (wave climate, river discharge, for example) or uncertainty (sea-level projections, model parameters, for example); see Stochastic and fractal methods in coastal morphodynamics. Data-driven models are used to make moving forecasts by integrating observed data of the recent history to calibrate uncertain model parameters or uncertain model input data, see: Reduction of uncertainties through Data Model Integration (DMI). Particle-based models describe numerically the motion of discrete fluid parcels taking into account their mutual interaction according to the laws of physics; in the most popular method (called Smoothed-particle Hydrodynamics (SPH)) the fluid is divided into a set of discrete moving parcels with properties which are smoothed over the parcel size according to a prescribed smoothing function. Computational fluid dynamics (CFD) models solve the Navier-Stokes equations for multiphase flows, including the interaction of the fluid (liquids and gases) with surfaces defined by boundary conditions. Cellular models divide the coastal system in fixed discrete cells which behave in a prescribed way according to the evolution of neighbouring cells, taking into account physical conservation laws.
  • Hybrid models combine physical and numerical models.

Morphology

The (study of the) shape or structure of natural objects, whether living or not. In the coastal context, morphology or geomorphology is generally used for designating the coastal bathymetry, including its sedimentary composition and structure. See also Coastal morphology.

Morphodynamics

See Coastal morphodynamics.

Mud

Fine cohesive sediment deposit containing a high fraction (≥20%) of clay minerals. Fine sedimentary particles, consisting of clay minerals, but also other particles (silt, fine sand, organic matter), can be glued together by large organic molecules (extracellular polymeric substances, EPS) into large mud flocs. These flocs, with a diameter of 0.1-1 mm, settle much faster than the individual particles and can form a colloidal suspension on the seabed. This so-called fluid mud layer can move along the seabed (driven by pressure gradients at the interface, by flow entrainment or by bed slope effect) and be a major cause of harbor siltation. After consolidation, which is often a lengthy process of months to years, a mud bed can become highly resistant to erosion by currents. See: Mud, Dynamics of mud transport , Sediment deposition and erosion processes, Coastal and marine sediments.

Nearshore zone

Same as lower shoreface.

Nourishment

Nourishment (or sand nourishment) is a method to neutralize the effect of coastal erosion by maintaining the sand volume of the active coastal zone. Sand is extracted (generally by dredging) from nearby sources and applied to the beach, the shoreface or the dunes. The costs highly depend on the location of available sand sources, which should be situated outside (seaward of) the active coastal zone. Dune nourishment is usually meant for safety against flooding, beach nourishment for restoration of the beach and shoreface nourishment for stabilizing the shoreline. See: Shore nourishment, Artificial nourishment.

Overwash

Wave uprush over a natural or artificial coastal barrier. The term overwash is also used for the resulting sand deposit at the leeside of the barrier.

Offshore zone

Different definitions of the offshore zone can be found in the literature. It can be the zone off the shoreface, off the surf zone or off the littoral zone. In the present context, the offshore zone is defined as the zone off the shoreface.

Progradation

Coastal extension into the sea due to natural aggradation. Coastal progradation occurs specifically where rivers supply large amounts of sediment.

Radiation stress

The radiation stress is defined as the excess flow of momentum due to wave orbital motions (with units of force/unit length). Gradients in the radiation stress induce an effective momentum transfer from wave motion to steady motion that takes place when the wave amplitude changes along the direction of propagation.

Reclamation

The transformation of areas which were formerly part of the marine or estuarine domain into non-floodable land.

Reef

A ridge of material at or near the surface of the ocean. Natural reefs are made of rocks or the skeletons of small animals (mainly corals). Reefs can also be created artificially for several reasons:

  • Protect coastlines from erosion;
  • Promote sea life for recreation and aquaculture;
  • Create a wave pattern that promotes the sport of surfing.

See: Coral reefs, Natural shore protecting barriers, Artificial reefs.

Reflective beaches

See Dissipative and reflective beaches

Refraction

The propensity of waves to align the wave front in shallow water with the depth contour, according to Snell's law. Also: Change of wave propagation direction due to the interaction with currents.

Rip current

Rip currents are strong offshore directed currents that occur when high waves break over nearshore sandbars. When breaking, high incident waves raise the water level in the area between the beach and nearshore sandbars. This elevated water is discharged by rip currents that flow seaward through narrow gaps between the nearshore bars. The corresponding morphological pattern is called "rip cell". It results from the morphodynamic feedback between the coastal morphology and the incident wave field. A local setback in the shoreline is often seen opposite the rip opening. The rip opening travels slowly downstream. Rip currents are dangerous for swimmers. See Rhythmic shoreline features.

Revetment

A revetment is a facing of stone, concrete units or slabs, etc., built to protect a scarp, the foot of a cliff or a dune, a dike or a seawall against erosion by wave action, storm surge and currents. This definition is very similar to the definition of a seawall, however a revetment does not protect against flooding. Furthermore, a revetment is often a supplement to other types of protection such as seawalls and dikes. See Revetments, Seawalls and revetments, Stability of rubble mound breakwaters and shore revetments.

Runnel

Depression between intertidal bars or between the dry beach and the upper intertidal bar (beach ridge). After high tide, the depression is filled with water, which is gradually discharged to the sea during falling tide via a channel (a so-called rip channel) that cuts through the beach ridge.

Salt marsh

A densely vegetated coastal ecosystem situated in the upper coastal intertidal zone between land and intertidal mudflats, or bordering directly open saltwater or brackish water if mudflats are absent.

  • Salt marshes are a key habitat of transitional waters lying at the interface between the land and the sea, depending on, and periodically covered by tidal sea water.
  • Salt marsh vegetation is usually composed of grasses and other low plants, but not trees.
  • Water saturation is the dominant factor controlling plant and animal communities and soils.
  • The soil may be composed of deep mud and peat.
  • Salt marshes are drained by tidal creeks that form spontaneously depending on local soil characteristics and gradients in the hydraulic head of infiltrated water.
  • Salt marshes usually form in sheltered coastal systems, such as lagoons and estuaries where fine sediments can be deposited. Salt marshes can also form behind spits and artificial sea defences where tidal waters can flow gently and deposit fine sediments.
  • Salt marshes are sometimes referred to as schorre or kwelder.

See: Salt marshes.

Sand bank

Popular term for large bars and ridges in tidal waters, especially in relation to navigation hindrance.

Sand nourishment

See Nourishment

Sand spit

A sand spit is an accretionary feature formed by littoral drift, consisting of a long narrow accumulation of sand or gravel, lying generally in line with the updrift coast, with one end attached to the land and the other projecting into the sea or across the mouth of an estuary or lagoon. During dry periods, a spit can develop into a barrier that temporarily blocks the mouth of a lagoon or a small river. See Sand spit.

Sandwave

  1. A subaqueous dune;
  2. A shoreline undulation with a wavelength in the range of a few hundred meters to a few kilometers, see: Rhythmic shoreline features.

Sea level rise

The so-called greenhouse effect or global warming causes a rise of the mean sea level, which will have a great impact on long-term coastal morphology, see Sea level rise. The long-term gradual sea-level rise will cause a general coastline retreat and an increased flooding risk depending on local conditions. Instead of the absolute rise of the mean sea level it is more relevant to consider the relative sea-level rise: the rise relative to vertical land motions that can be positive (uplift) or negative (subsidence). An estimate of coastline retreat due to relative sea-level rise can be derived from the so-called Bruun rule, which is valid under certain rather restrictive conditions, see: Bruun rule.

Sediment

Fine-grained loose particles such as gravel, sand, mud. These sediments are produced by chemical or physical weathering of rocks, by seabed erosion and by soil erosion in river basins. They are called clastic sediments and consist of quartz, feldspar, mica and clay minerals. Other particles have a biotic origin, for example shell debris, peat, detritus, fecal pellets and plankton. Sediment particles have widely different grainsizes: clay (< 0.002 mm), silt (0.01-0.02 mm), sand (0.1-2 mm), gravel (2-5 mm). The density is of the order of 2.65 times the density of water. Sand or gravel beds occur in zones with strong (tidal) currents and strong wave activity, whereas fine sand, silt and mud cover the seabed in sheltered zones where currents and wave activity are weak. See: Coastal and marine sediments, Sediment deposition and erosion processes, Gravel Beaches.

Sediment cell

Same as coastal cell.

Sediment transport

The amount of sediment transported by water motion (currents and /or waves). Sediment transport is a crucial link in the interaction between coastal morphological evolution and waves, currents and tides. Sedimentation is related to convergence of sediment transport and erosion to divergence of sediment transport. Sediment transport takes place in several ways: Suspended-load transport, Bedload transport and Fluid mud motion. Suspended-load transport is the transport of sedimentary particles that are suspended in the fluid. Bedload transport is the transport of sedimentary particles that are rolling or leaping along the seabed. Fluid mud transport is the motion of a fluid mud layer along the seabed. Formulas for bedload transport are based on empirical relationships involving characteristics of sediment, currents and waves. See: Sediment transport formulas for the coastal environment, Sand transport.

Seiche

Harbour seiches are resonant (or near-resonant) standing oscillations in a semi-enclosed water body caused by incoming long-period waves (periods typically in the range 200-2000 s). Incoming waves can be strongly amplified if the period is close to the harbour resonance period, causing damage to ships and moorings. Long-period waves can be generated by nonlinear interaction of random short waves with a peaked frequency distribution (see Infragravity waves), generated mainly in shallow water and reflected from adjacent coasts. Long-period waves can also be generated by meteorological effects, in particular strong wind speed fluctuations during storms, related to the passage of a cold front. Other generation mechanisms include deep-sea internal waves, seismic activity, or tsunamis. Seiches occur also in closed basins, such as lakes, often induced by strong fluctuations in the wind field.

Setback area

A strip along the coastal zone where certain development activities are prohibited or significantly restricted. See: Setback area.

Sheet-flow

Sheet-flow sediment transport refers to transport of sandy sediments as a fluidized thin surface layer (thickness of ten to several tens grain diameters). This type of sediment transport occurs under strong wave action (wave orbital velocity greater than 1 m/s), where bed ripples are flattened out. In the sheet-flow layer, continuous contacts between sand grains create an intergranular stress. This stress decreases the velocity in *the sheet-flow layer to about one half the velocity in the top layer. The sediment concentration in the sheet-flow layer is in the order of 100 to 1000 kg/m3. See: Sediment transport formulas for the coastal environment.

Shelf sea

See Continental shelf.

Shoaling

Shoaling is the deformation of incident waves on the lower shoreface that starts when the water depth becomes less than about half of the wavelength, causing the waves to become steeper: increase in amplitude and decrease in wavelength.

  • Wave amplification is due to (approximate) continuity of the wave energy flux [math]F=c_g E[/math] seaward of the surf zone, where [math]E = \frac{1}{8} \rho g H^2[/math] is the wave energy and [math]c_g[/math] the wave group propagation speed. The landward decrease of the wave group propagation speed ([math]c_g \approx \sqrt{gh}[/math] in shallow water of depth [math]h[/math]) results in a landward increase of [math]E[/math], thus in a landward increase of wave height [math]H[/math]. See: Shallow-water wave theory for a more detailed treatment.
  • Wave propagation in the shoaling zone has a strongly non-linear character because the wave height is no longer negligible compared to the water depth. This produces wave asymmetry, with the wave orbital velocity being greater in the onshore than offshore direction and the offshore-to-onshore orbital acceleration being greater than the onshore-to-offshore acceleration.
  • Wave shoaling precedes wave breaking on the upper shoreface when the wave steepness exceeds a critical limit.

Shore protection

See Coastal protection.

Shoreface

The shoreface is the nearshore zone of the inner continental shelf that is bounded landward by the mean low-water line and that extends seaward to where the influence of wave action on sediment transport is on average minor compared to other influences. A similar definition is: The shoreface is the zone seaward of the shoreline where offshore generated waves interact with the upward sloping seabed. The shoreface can be divided in two zones, the upper shoreface and the lower shoreface (also called shoaling zone). The upper shoreface is the zone where most energy is dissipated by wave overturning and breaking and the lower shoreface the zone where waves shoal. The lower part of the shoreface extends to the so-called outer closure depth [math]h_{out}[/math]; beyond this depth the seabed is hardly influenced by waves and wave-induced sediment transport is (on average) insignificant. The transition between lower and upper shoreface is generally defined by the closure depth [math]h_{in}[/math] related to the significant wave height, which is exceeded 12 hours per year, [math]H_{s,12h/y}[/math]. See Shoreface profile.

Shoreline

The intersection between the water line and the shore. The line delineating the shoreline on Nautical Charts (Sea Maps) approximates the Mean High Water Line. See the article Shoreline for an overview of shoreline detection techniques.

Shoreline management

The act of dealing – in a planned way – with actual and potential coastal erosion and its relation to planned or existing development activities on the coast, see Shoreline management. The objectives of Shoreline Management are:

  • To ensure the development activities in the coastal area follow an overall land use plan and a general environmental policy;
  • To ensure the development activities in the coastal area do not cause to or aggravate erosion;
  • To ensure that development activities do not occur in sensitive areas;
  • To ensure that erosion control techniques are cost-effective and socially and environmentally acceptable.

Shoreline management is typically based on coastal sediment cells.

Siltation

Accumulation of fine sediments (sand, silt, mud) in channels, harbors and fairways. See: Siltation in harbors and fairways, Dynamics of mud transport , Sediment deposition and erosion processes, Sediment transport formulas for the coastal environment.

Slack tide

Tidal phase at which the current turns from flood to ebb (high-water slack tide) or from ebb to flood (low-water slack tide). See Definition of ebb and flood (tide).

Shore

Usually same as Beach.

Spit

See Sand spit.

Storm surge

The rise in water-level on an open coast as a result of the combined impact of the wind stress on the water surface, the atmospheric pressure reduction and local topographic features. The storm surge does not include the effect of the astronomical tide. The storm at a location is in first approximation inversely proportional with the water depth in the offshore zone. This implies that shores out to deep oceans will only be exposed to relatively small surges whereas shores out to shallow seas can be exposed to high surges. See: Extreme storms.

Stratification

Less dense water layer overlying a water layer of higher density (related to higher salinity, lower temperature or higher suspended sediment concentration). Density differences in the vertical inhibit turbulent mixing, which causes the interface of the layer to be sharpened. See: Seawater density, Salt wedge estuaries.

Subsidence

Downward motion of the land surface. It is most often related to soil compaction (underground material movement) caused by the removal of water, oil, natural gas, or mineral resources out of the ground by drainage, pumping, fracking, or mining activities. Subsidence can also be caused by natural events such as earthquakes, glacial isostatic adjustment, erosion, sinkhole formation, sediment loading by river deposites, and adding water to fine soils deposited by wind (a natural process known as loess deposits). See also: Coastal cities and sea level rise.

Surf beat

Long-periodic oscillation of the water line on the beach. The oscillation is related to Infragravity waves in the surf zone. See: Infragravity waves, Edge waves, Shallow-water wave theory.

Surf similarity parameter

The surf similarity parameter is defined as [math]\; \xi = \Large\frac{\tan \beta}{\sqrt{H_s/L}}\normalsize , \;[/math] where [math]L=\Large\frac{g T^2}{2 \pi}\normalsize[/math] is the wavelength at the seaward boundary of the breaker zone and [math] H_s/L[/math] the wave steepness at this location. It compares the wave surface slope to the bed slope in the surf zone and represents important features of the hydrodynamics of the surf zone.

Surf zone

The surf zone (or breaker zone) is the zone where waves break as a consequence of depth limitation and surf onshore as wave bores. The width of the surf zone varies depending on the wave conditions and water level. The surf zone is narrow and close to the shoreline in a gentle wave climate and can be very wide under storm conditions, extending from the seaward boundary of the upper shoreface to the dunefoot. It is estimated that 80 to 90% of the yearly littoral transport takes place within the breaker or surf zone.

Swash

Up and down propagation of bores formed after collapse of waves on the beach. Swash is the decelerating uprush phase and backwash is the accelerating downrush phase. On dissipative coasts swash processes are dominated by infragravity waves. See: Swash zone dynamics.

Swash bar

The term "swash bar" usually designates a berm that is formed wave uprush on the higher intertidal zone of a tidal flat. See also Beach berm

Swash zone

Zone where wave bores run up and down the beach face.

Swell

Waves generated far offshore in the deep sea that propagate onshore. Ocean swell waves have longer wavelengths than locally generated wind waves. The longest waves in the ocean travel faster and dissipate less energy than the shorter waves generated by the same strong wind event. They therefore can reach distant shores whereas the shorter waves cannot. See Waves.

Tidal asymmetry

Difference between the ebb and flood phase of the tide: different duration of ebb and flood flow, different strength of ebb and flood currents, different duration of rising tide and falling tide. Tidal asymmetry is mainly caused by the nonlinear dependence of tide propagation on water level variation in shallow coastal systems with complex geometry (e.g., estuaries, lagoons). Tidal asymmetry can also result from the superposition of certain astronomical tidal constituents in estuaries with strong diurnal tides. Tidal asymmetry can strongly influence sediment transport and is an important morphodynamic feedback mechanism for the morphological development of estuaries. It is also plays an important role in the formation of the estuarine turbidity maximum. See Tidal asymmetry and tidal basin morphodynamics, Estuarine turbidity maximum.

Tidal bore

Breaking tidal flood wave – the ultimate stage of tidal asymmetry. Tidal bores occur in shallow funnel-shaped estuaries with a large tidal range (generally more than 6 m). See Tidal bore dynamics.

Tidal channel

Seabed incision concentrating the main tidal flow. Tidal channels form naturally in sedimentary environments where tide-induced water motion is stronger than wave-induced water motion.

Tidal creek

A tidal channel that drains a salt marsh.

Tidal flat

Shallow, sandy or muddy area which is covered and uncovered by the rise and fall of the tide. Muddy tidal flats are also called mud flats or slikke. As a rule of thumb, tidal flats generally occur in sheltered coastal areas where the relative tidal range RTR, defined as the ratio between the mean spring tidal range and the annual average significant wave height [math]H_s[/math], is about 15 or higher.

Tidal inlet

The connection between the sea and a tidal basin (lagoon) or estuary partially shielded by a barrier island, sand spit or headland. A tidal inlet consists of a narrow deep channel through which strong currents flow, with flood and ebb tidal deltas at the landward and seaward sides.

Tidal prism

Volume of water flowing during flood through a tidal inlet, or through a cross-section of an estuary or a tidal lagoon.

Tidal range

Water level difference between high water and low water, i.e. twice the tidal amplitude. The tidal range changes from tide to tide depending on the positions of moon and sun relative to the earth; the most important change is the fortnightly variation from spring tide to neap tide. See Ocean and shelf tides.

Tidal ridge

Submarine sand ridge with a length of several tens of kilometers and height of a few tens of meters, generated by the nonlinear interaction of tidal currents with the seabed on the shelf sea. Sand ridge fields consist of a number of tidal ridges with a spacing of the order of 5 km. See: Sand ridges in shelf seas.

Tidal wave

The wave associated with tidal motion. The term "tidal wave" is also frequently used as a popular expression for an unusually high and destructive water level along a shore, thus including the combined effect of astronomical and meteorological surges.

Tide

The tide (more precisely, the astronomical tide) is the large-scale water motion generated by the rotation of the earth in combination with the varying gravitational influence on the ocean of celestial bodies, especially the moon and the sun. These phenomena cause predictable and regular oscillations in the water level, which are referred to as the tide. The astronomical tide at a specific location can be predicted and is published in Tidal Tables. See: Ocean and shelf tides, Tidal motion in shelf seas. The term 'tide' is sometimes used for the combined effect of astronomical tide and wind-driven set-up or set-down of the sea level (including storm surges).

Transgression

Flooding of land by the sea related to relative sea level rise. Transgression implies coastline retreat.

Tsunami

Long waves caused by a strong local disturbance of the water mass. The most important generation mechanisms are subsea earthquakes and subsea slides of unconsolidated seabed slopes. Tsunamis propagate very fast over the ocean with very few energy loss due to the great ocean depth. Tsunamis generally consist of a few successive waves with wavelengths typically much larger than the wavelength of wind-generated waves and much smaller than the wavelength of tidal waves. In nearshore waters the amplitude increases dramatically due to shoaling, see Tsunami.

Turbidity maximum

Convergence zone of suspended sediment transport in an estuary, where turbidity levels are high due to high suspended sediment concentrations. Upstream (landward) transport of fine suspended sediment in an estuary is possible due to estuarine circulation and tidal asymmetry (maximum flood current stronger than maximum ebb current). This produces a maximum in the suspended sediment concentration just downstream of the zone where the influence of river discharge on sediment transport becomes dominant. Fine sediments in the turbidity maximum zone settle to the bed in periods where currents are small (slack tide, neap tide), which may result in the formation of fluid mud layers. High turbidity often causes oxygen depletion and mortality of estuarine organisms. It also enhances sedimentation of tidal flats and harbours. See: Estuarine turbidity maximum, Dynamics of mud transport.

Turbulence

Irregular flow pattern of individual fluid parcels related to small-scale flow instability, see Turbulent boundary layer. Turbulence plays a major role in mixing processes and in energy dissipation. See: Transport and dispersion of pollutants, nutrients, tracers in mixed nearshore water, Currents and turbulence by acoustic methods.

Wave

The term "wave" designates in most cases surface water waves generated by wind (other types of waves are explicitly referred to as tidal wave, tsunami wave, etc.). A wave field is generally a superposition of waves of different height, period and direction that can be described by a wave spectrum. A unidirectional wave field is often characterised by the significant wave height [math]H_s[/math] (representing approximately the mean wave height of the highest third of the waves) and the spectral peak period [math]T_p[/math] (wave period with the highest energy). See: Statistical description of wave parameters. Coasts situated on the open ocean are mainly subjected to long-period swell waves. Coasts situated on inland seas are mainly subject to locally generated short-crested waves, also called "sea". See Waves and Shallow-water wave theory.

Wave breaking

Wave breaking is the ultimate stage of wave deformation due to strong nonlinearity of the wave propagation process when waves enter shallow water (water depth less than half the wavelength). Waves start breaking (by surging, collapsing, plunging or spilling) where the still water depth is smaller than one or two times the wave height. Waves may reform in the surf zone, but remain depth-limited by spilling or by plunging a second time, until final collapse and uprush on the beach. See: Wave transformation, Shallow-water wave theory.

Wave energy

Energy carried by waves when propagating. The wave energy [math]E[/math] is proportional to the square of the wave height [math]H[/math] (formula: [math]E=g \rho H^2 / 8[/math]). For irregular waves, [math]H[/math] is the root mean square wave height [math]H_{rms}[/math], see Statistical description of wave parameters.

Wave group

Incident waves generally arrive in groups, corresponding to the superposition of incident waves with slightly differing wave lengths and frequencies that are present in the wave spectrum. Wave groups generate infragravity waves with the same group wavelength and period, by non-linear interaction. Wave groups also cause surf beat. See: Shallow-water wave theory, Infragravity waves.

Wave height

The water level difference between wave trough and wave crest, or twice the wave amplitude. In an irregular wave field, successive incident waves have different amplitudes and phases. In deep water the wave height distribution often follows approximately a Rayleigh distribution. However, this is not the case in the surf zone where the wave height is limited by the water depth. See Statistical description of wave parameters.

Wave propagation

Progression and transformation of waves in time and space.

  • The speed [math]c[/math] of a wave propagating without frictional losses in deep water is given by [math]c \approx \sqrt{g/k} = g/\omega[/math] where [math]g[/math] is the gravitational acceleration, [math]k=2 \pi / \lambda[/math] the wave number, [math]\lambda[/math] the wavelength and [math]\omega=kc[/math] the angular frequency. Deep water means: still water depth [math]h[/math] much larger than [math]1/k[/math]. The dependency of the propagation speed on frequency causes wave dispersion.
  • In shallow water (depth [math]h[/math] much smaller than [math]1/k[/math]), the wave propagation speed is proportional to the square root of the water depth [math]h[/math] (formula: [math]c \approx \sqrt{gh}[/math]), thus not depending on the wave frequency.
  • In shallow water, wave propagation is a strongly nonlinear process, leading to wave transformation and breaking.
  • A wave group propagates at a smaller speed [math]c_g[/math] than the constituent short waves. Wave energy propagates at the speed of the wave group.

See: Shallow-water wave theory.

Wave run-up

The maximum onshore elevation reached by a wave running on the beach, relative to the water level in the absence of waves. It is the sum of swash uprush and wave set-up. Wave run-up is an important factor in the design of coastal protection structures and is a dominant process leading to the erosion of coastal dunes. See also Wave run-up, Swash zone dynamics, Tsunami.

Wave set-up

Elevation of the mean water level at the shoreline due to wave breaking in the surf zone. The wave set-up is proportional to the wave height at the breaker line. As a rule of thumb, the wave setup is of the order of 20% of the offshore significant wave height. See: Wave set-down and set-up.


References

  1. Mangor, K., Drønen, N. K., Kaergaard, K.H. and Kristensen, N.E. 2017. Shoreline management guidelines. DHI https://www.dhigroup.com/marine-water/ebook-shoreline-management-guidelines
  2. Coastal engineering Research Center, Department of the Army, Waterways Experiment Station, 1984. "Shore protection manual".



The main author of this article is Mangor, Karsten
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Citation: Mangor, Karsten (2021): Definitions of coastal terms. Available from http://www.coastalwiki.org/wiki/Definitions_of_coastal_terms [accessed on 28-03-2024]