7.1 Glossary

A Class tide gauge
One of a UK network of tide gauges maintained to the highest and most consistent standards.
Accretion
The accumulation of (beach) sediment, deposited by natural processes.
Apron
Layers of stone, concrete or other material to protect the toe of a structure such as a seawall.
Armour unit
Large quarried stone, or concrete block, used as protection against wave action.
Backshore
Coastal area between the beach head and high water, potentially affected by large waves during high tides.
Barrier beach
A sand or shingle bar above high tide, parallel to the coastline and separated from it by a lagoon.
Bathymetry
Seabed topography.
Beach
A deposit of non-cohesive mobile material (e.g. sand, gravel) situated on the interface between dry land and the sea (or other expanses of water).
Beach face
From the beach crest out to the limit of sediment movement.
Beach head
Ridge, cliff, dune or sea defence forming the landward limit of the potentially active beach
Beach profile
Beach cross-section perpendicular to the shore, which may extend from the backshore, across the foreshore and into the nearshore zone.
Beach recharge
Mechanical addition of imported sediment to a beach, also known as beach replenishment/ nourishment.
Berm
Beach: near horizontal plateau above high water, formed by deposition of beach material by wave action or by mechanical plant as part of a beach recharge scheme. Structure: near horizontal area, often separating the upper part of a seawall or revetment from the lower part.
Binding
Use of chemical glues to create a skin across a sediment surface. Usually applied by spraying.
Blowout
Wind-eroded area within a dune system.
Boulder
A rounded rock on a beach, greater than 250mm in diameter.
Breaching
Failure of the beach head allowing flooding by tidal action.
Breaker zone
The zone within which waves approaching the coastline commence breaking, typically in water depths of between 5 and 10 metres.
Breastwork
Vertically faced or steeply inclined structure built parallel to the shoreline, at or near the crest of the beach, to resist erosion, usually timber.
Breakwater
Large coastal structure designed to protect an area from wave action, either for navigation or coastal defence. Can be connected to or detached from the shoreline.
Bypassing
Moving beach material from the updrift to the downdrift side of an obstruction to longshore drift i.e. harbour breakwater, estuary or river mouth.
Chart datum
The level to which both tidal levels and water depths are reduced – on most UK charts this level is approximately the predicted lowest astronomical tide level (LAT).
Coastal cell
See Sediment cell
Coastal defence
General term used to encompass both coast protection against erosion and sea defence against flooding.
Coast protection
Works or management operations intended to control coastal erosion
Coastal processes
Collective term covering the action of natural forces on the shoreline, and nearshore seabed.
Coastal squeeze
The effect when hard defences (including beaches fixed in position by control structures) interrupt the natural response of the shoreline to sea level rise, restricting landward retreat and resulting in loss of the intertidal habitat.
Cobble
A rounded rock on a beach, with diameter ranging from about 75 to 250mm – see also boulder, gravel, shingle.
Cohesive sediment
Sediment containing significant proportion of clays, the electromagnetic properties of which cause the sediment to bind together.
Community
Plants and/or animals living together under characteristic, recognisable conditions.
Core
An inner, often much less permeable portion of a breakwater, or barrier beach.
Crest
Highest point on a beach face, breakwater or seawall.
Cross-shore
Perpendicular to the shoreline.
Deflation
Erosion of dunes by wind action.
Design wave condition
Usually an extreme wave condition with a specified return period used in the design of coastal works.
Detached breakwater
A breakwater without any constructed connection to the shore.
Diffraction
Process affecting wave propagation, by which wave energy is radiated normal to the direction of wave propagation into the lee of an island or breakwater.
Dominant winds
Winds with greatest effect on shoreline processes.
Downdrift
Direction to which material is being transported in the littoral zone.
Dunes
Accumulations of windblown sand on the backshore, usually in the form of small hills or ridges, stabilised by vegetation or control structures.
Dune face
The seaward face of a dune system where coastal processes may cause erosion or accretion.
Ebb
Period when tide level is falling; often taken to mean the ebb current that occurs during this period.
Embankment
A bank protecting land from flooding.
Estuary
A semi-enclosed coastal body of water within which seawater is measurably diluted with fresh water derived from land drainage.
Extreme
The value expected to be exceeded once, on average, in a given (long) period of time.
Fetch
Distance over which a wind acts to produce waves – also termed fetch length.
Fetch-limited
Situation in which wave energy (or wave height) is limited by the size of the wave generation area (fetch).
Fixed dune
Dune with a surface stabilised by vegetation.
Foredune
Developing dune which lies nearest the sea in a prograding system, also embryo-dune.
Foreshore
Shore between high and low water – see also intertidal.
Freeboard
The height of the crest of a structure above the still water level.
Gabion
Wire mesh baskets filled with rock.
Geotextile
Synthetic or natural fabrics used in engineering to separate layers of granular material.
Gravel
Beach material usually well rounded and between about 2mm and 75mm in diameter – see also shingle.
Grey dune
Well-vegetated fixed dune with mosses, lichens, grasses and herbs.
Groyne
Narrow, shore-normal (approximately) structure built to reduce longshore currents, and/or to trap and retain beach material. Most groynes are of timber or rock, and extend from the beach head across the foreshore.
Groyne bay
The beach compartment between two groynes.
Habitat
The recognisable area or type of environment in which an organism normally lives.
Hard defences
General term applied to impermeable coastal defence structures of concrete, timber, steel, masonry etc, which reflect a high proportion of incident wave energy. cf. Soft defences
Headland
Hard feature ( natural or artificial) forming local limit of longshore extent of a beach.
Intertidal
The zone between high and low tide lines – see also foreshore.
Joint probability
The probability of two (or more) events occurring together.
Leach
The process by which percolating water removes nutrients from the soil
Littoral drift
Movement of beach material in the littoral zone under the influence of waves and currents.
Littoral zone
Zone from the beach head seawards to the limit of wave induced sediment movement.
Longshore drift
Movement of (beach) sediments approximately parallel to the coastline.
Machair
Sandy coastal plain, typically calcareous (as found in northwest Scotland).
Macro-tidal
Tidal range greater than 4m.
Meso-tidal
Tidal range between 2m and 4m.
Micro-tidal
Tidal range less than 2m.
Mud flat
An area of fine silt usually exposed at low tide but covered at high tide, occurring in sheltered estuaries or behind shingle bars or sand spits.
Mulching
Mixing organic material into the sediment surface to reduce erosion, moisten the surface and fertilise the soil.
Natural succession
The process by which one community of organisms gives way to another in an orderly series from colonisers to climax.
Neap tide
Tide of least range in the tidal cycle.
Nearshore
Areas where waves are transformed by interaction with the sea bed.
Numerical modelling
Refers to the analysis or prediction of coastal processes using computational models.
Offshore
The zone beyond the nearshore zone where sediment motion induced by waves alone effectively ceases and where the influence of the sea bed on wave action has become small in comparison with the effect of wind.
Overwash
The effect of waves overtopping a beach, often carrying sediment landwards
Physical modelling
Refers to the investigation of coastal processes using a scaled model.
Pocket beach
A beach located between two headlands.
Prevailing winds
Winds of greatest frequency, often but not always the dominant winds.
Prograding
Developing along the shore or into open water.
Reef
A ridge of rock, or other material, lying seawards of the low water line.
Refraction
Process by which the direction of a wave moving in shallow water at an angle to the bathymetric contours is changed so that the wave crests tend to become more aligned with those contours.
Regrading
The mechanical movement of beach sediment from the lower foreshore to the upper foreshore – see also reprofiling.
Reprofiling
The mechanical movement of beach sediment from downdrift to updrift – see also regrading.
Return period
Average period of time between occurrences of a given probability event.
Revetment
A sloping surface of stone, concrete or other material, used to protect the shoreline against the sea.
Rhizome
Fleshy root-ball of plant from which roots and side shoots develop.
Run-up, Run-down
The upper and lower levels reached by a wave on a beach or coastal structure, relative to still- water level.
Salient
Coastal formation of beach material developed by wave refraction and diffraction and longshore drift comprising a bulge in the coastline towards an offshore island or breakwater, but not connected to it as in the case of a tombolo.
Salt marsh
Intertidal area having characteristic vegetation adapted to saline soils and to periodic submergence in sea water.
Sand
Sediment particles, mainly of quartz, with a diameter of between 0.062mm and 2mm, generally classified as fine, medium, coarse or very coarse
Sea defence
Works or management operations intended to prevent coastal flooding
Seawall
Solid near vertical coastal defence structure built parallel to the coastline, usually of concrete or masonry.
Sediment
Particulate matter derived from rock, minerals or shell debris.
Sediment cell
In the context of a strategic approach to coastal management, a length of coastline confined by natural or artificial barriers around which no sand or shingle can be transported – also know as coastal cell.
Sediment sink
Point or area at which beach material is irretrievably lost from a sediment cell, such as an estuary, or a deep channel in the seabed.
Sediment source
Point or area on a coast from which beach material arises, such as an eroding cliff, or river mouth.
Shingle
Coarse grained beach sediment dominated by gravel but including some sand.
Shoreline
One characteristic of the coast, often poorly defined, but essentially the interface between land and sea.
Shoreline management
The development of strategic, long-term and sustainable coastal defence policy within a sediment cell.
Significant wave height
Measured as the average height of the highest third of the waves in a sea, and is approximately the visually observed wave height (Hs or H).
Sill
Continuous shore parallel structure, submerged at high tide.
Silt
Sediment particles with a grain size between 0.004mm and 0.062mm i.e. coarser than clay particles but finer than sand.
Slack
Area within dune system where the surface is at or near the ground water level.
Soft defences
Usually refers to managed beaches, saltmarshes or mudflats that provide protection to the shoreline, but may also include rock structures which dissipate waves rather than opposing them. cf. Hard defences
Spring tide
Tide of greatest range in a monthly cycle.
Spit
A long, narrow accumulation of sand or shingle, 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.
Strand line
Line of debris formed at the limit of wave run up along the upper foreshore.
Surge
Changes in water level as a result of meteorological forcing (wind, high or low barometric pressure) causing a difference between the recorded water level and that predicted using harmonic analysis; may be positive or negative.
Suspended load
A mode of sediment transport in which the particles are supported, and carried along by water.
Swash zone
The zone of wave action on the beach, which moves as water levels vary, extending from the limit of run-down to the limit of run-up.
Swell (waves)
Remotely wind-generated waves. Swell characteristically exhibits a more regular and longer period and has longer crests than locally generated waves – see also wind sea.
Surf zone
The zone of wave action extending from the water line (which varies with tide, surge, set-up, etc.) out to the most seaward point of the zone (breaker zone) at which waves approaching the coastline commence breaking, typically in water depths of between 5 and 10 metres.
Tidal current
The movement of water associated with the rise and fall of the tides.
Tidal range
Vertical difference in high and low water level once decoupled from the water level residuals.
Tide
The periodic rise and fall in the level of the water in oceans and seas; the result of gravitational attraction of the sun and moon.
Tombolo
Coastal formation of beach material developed by refraction, diffraction and longshore drift to form a ‘neck’ connecting a coast to an offshore island or breakwater - see also salient.
Thatching
Covering of brushwood laid down to protect dune grasses and help trap sand.
Updrift
Direction from which material is being transported in the littoral zone.
Water table
Level below which the soil is waterlogged.
Wave climate
The seasonal and annual distribution of wave height, period and direction.
Wave direction
Mean direction of wave energy propagation relative to true North.
Wave height
Vertical distance from wave trough to crest.
Wave period
Time taken for the passage of successive waves past a point.
Wave spectrum
Distribution of wave energy as a function of wave frequency and direction.
Wave transformation
Change in wave energy due to the action of physical processes.
Wind rose
Diagram showing the long term distribution of wind speed and direction.
Wind sea
Wave conditions directly attributed to recent winds – see also swell.
Wind set-up
Elevation of the water level over an area directly caused by wind stress on the water surface.
Yellow dune
Incompletely vegetated dune with bare sand frequently exposed between plant stems.