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Glossary

Term Description
Accretion The process of sediment accumulating on the sea bed leading to a raising of bed levels
Acoustic provinces Areas of seabed with similar reflective properties for sound waves.
Advection The mixing of different water bodies by horizontal motion; mass transfer of matter
Aggradation Progressive increase in sedimentation (see also accretion).
Aggregates Sand, gravel and crushed rock suitable for use in the construction industry for mixing with a matrix to form concrete, macadam, mortar or plaster, or used alone as in railway ballast, unbound road-stone or graded fill.
Amphidromes Locations where tidal range is zero.
Amplitude Half of the peak-to-trough range (or height) of a waveform.
Antecedent Conditions defined by what went before (e.g. preceding geological epoch)
Anthropogenic Produced or caused by humans.
Armour stone Large quarried stone or specially shaped concrete block used as primary protection against wave action.
Armouring Protection of erodible materials by resistant materials.
Average Hsig Average significant wave height recorded during a storm event (see significant wave height).
Backshore The upper part of the active beach above the normal reach of the tides (high water), but affected by occasional large waves occurring during a high tide/storm surge.
BAP Biodiversity Action Plan
Barrier beach A sand or shingle bar above high tide, parallel to the coastline and separated from it by a lagoon.
Bathymetry Refers to the levels of the seabed and their variability.
Beach A deposit of unconsolidated material (e.g. sand, gravel) situated on the interface between land and the sea (or other large expanse of water) and actively "worked" by present-day hydrodynamic processes (i.e. waves, tides and currents) and occasionally by winds.
Beach crest The point representing the limit of high-tide storm wave run-up.
Beach face From the beach crest to the limit of sediment movement offshore.
Beach nourishment Active replenishment of beach material
Beach profile A cross-section taken perpendicular to a given beach contour. The profile may include the face of a dune or seawall, extend over the backshore, across the foreshore and seaward into the nearshore zone.
Beach recharge Augmenting the natural volume of sediment on a beach, using material from elsewhere - also known as beach replenishment/nourishment/feeding.
Bed shear stress A measure of energy transfer to the seabed from water movements.
Bedforms Features on a seabed or shore (e.g. ripples and sand waves) resulting from the movement of sediment over it.
Bedload Sediment transport mode in which individual particles either roll or slide along the seabed as a shallow, mobile layer a few particle diameters deep.
Bench mark (BM) A fixed physical object or mark used as reference for a vertical datum.
Beneficial use Dredged material used and not disposed of at sea, for example in reclamation, beach recharge, beach nourishment and other uses.
Benthic Of the organisms that live in or on the seafloor
Benthos Organisms living on or in the seafloor
Berm A nearly horizontal plateau on the beach face or backshore.
Bioaccumulation A process by which chemical substances are accumulated by aquatic organisms from water directly or through consumption of food containing the chemicals.
Biogenic Produced by organisms.
Bore A broken swell wave travelling shorewards across the surf zone.
Boulder A rounded rock on a beach, greater than 250 mm in diameter, larger than a cobble (see also gravel, shingle).
Boundary conditions Environmental conditions (e.g. waves, currents, sediment transport, etc) used as boundary input to physical or numerical models.
BP Before present (usually refering to years before present time)
BP Before present
Breaching Failure of the beach barrier allowing flooding by sea to area behind.
Breaker Index The ratio between the height of a wave and the water depth in which the wave breaks.
Breaker Zone That area of coastal waters where shoaling effects cause swell waves to break.
Breaking Waves As waves increase in height through the shoaling process, the crest of the wave tends to speed up relative to the rest of the wave. Waves break when the speed of the crest exceeds the speed of the advance of the wave as a whole. Waves can break in three modes: spilling, surging and plunging.
Capital Dredging The 'first time' creation of new channels or berths as part of a capital programme.
CD Chart Datum
CHaMP Coastal Habitat Management Plan
Chart Datum (CD) The level to which both tidal levels and water depths are reduced - on most UK charts, this level is that of the lowest low tide (LAT). For example, in Southampton CD is 2.74 m below Ordnance Datum Newlyn (ODN).
Clasts Fragmental mineral or rock material (forming sediment).
Clay A fine-grained, plastic, sediment with a typical grain size less than 0.004 mm. Possesses electromagnetic properties that bind the grains together to give a bulk strength or cohesion.
Coastal defence General term used to encompass both coast protection against erosion and sea defence against flooding.
Coastal processes Collective term covering the action of natural forces on the shoreline and nearshore seabed.
Coastal zone Some combination of land and sea area.
Cobble A rounded rock on a beach, with diameter ranging from about 75 to 250 mm (see also boulder, gravel and shingle).
Cohesive sediment Sediment containing significant proportion of clays, the electromagnetic properties of which cause the sediment to bind together giving a bulk strength (see clay).
Concentration The quantifiable amount of a substance in the surrounding air, water, food or sediment.
Consolidation The compacting of sediment/strata of material, as a result of pressure after deposition.
Constituent One of the harmonic elements in a mathematical expression for the tide-producing force and in corresponding formulas for the tide or tidal current. Each constituent represents a variation in the relative positions of the Earth, Moon, and Sun.
Core A cylindrical sample extracted from a beach or seabed to investigate the types and depths of sediment layers.

A inner, often much less permeable, portion of a breakwater or barrier beach.
Correlation Coefficient Measurement (between -1 and 1) of the quality of fit of a line through a set of data points. The closer the number to +-1.0 the better the fit.
Crest Highest point on a beach face, breakwater or seawall.
Cross-shore Perpendicular to the shoreline.
Current Flow of water.
CW Coastal Waters
CWS County Wildlife Sites
D50 Median particle/ grain size in sediments
Deepwater Water sufficiently deep that surface waves are little affected by the ocean bottom. Generally, water deeper than one-half the surface wave length is considered deepwater.
Defra Department for Environment Food and Rural Affairs
DEM Digital Elevation Model
Depth-limited Situation in which wave generation (or wave height) is limited by water depth.
Design Wave Height The wave height adopted for the purposes of designing coastal structures such as breakwaters and seawalls. It is chosen to ensure that the structures are not at undue risk of wave damage.
Detection limit The smallest concentration or amount of a substance that can be reported as present with a specified degree of certainty by a definite, complete analytical procedure.
Diastrophic Movement of the earth’s crust to produce surface irregularities
Diffraction The "spreading" of waves into the lee of obstacles such as breakwaters by the transfer of wave energy along wave crests. Diffracted waves are lower in height than incident waves.
Directional Waverider Buoy A floating device used to measure ocean wave height, period and direction.
Dissolved oxygen The amount of oxygen in solution.
Diurnal Having a period of a 'tidal day' i.e. about 24.8 hours.
Diurnal inequality The difference in height of the two high waters or of the two low waters of each tidal day; also, the difference in speed between the two flood tidal currents or the two ebb currents of each tidal day.
Downdrift In the direction of net longshore transport of beach material.
Dunes Accumulation of windblown sand on the backshore, usually in the form of small hills or ridges.

A type of subaenal bedform indicating significant sediment transport over a sandy beach.
EA Environment Agency
Ebb Period when tide level is falling.
Ebb-tidal delta Sediment deposited on the seaward side of a tidal inlet.
EC European Commission
EEC European Economic Community
EFCI Estuarine Fish Community Index
Effective Record Length Total record length multiplied by the data capture rate.
Effluent A complex waste material (eg liquid industrial discharge or sewage) that may be discharged into the environment.
EGA Expert Geomorphological Assessment
Electromagnetic Current Meter A device which measures current and water pressure variations. If deployed in shallow water current and pressure data can be converted to wave height, period and direction.
Embayment Sea area within a concave shoreline plan shape.
EN English Nature
Epoch A geological time unit.
Equatorial tides Tides occurring semi-monthly as a result of the Moon being over the Equator. At these times the tendency of the Moon to produce a diurnal inequality in the tide is at a minimum.
Equilibrium Balance of forces or state which is maintained over time
Erosion The removal of sediment from the seabed by water movement resulting in a lowering of bed levels The landward retreat of a shoreline due to this process.
Estuaries Semi-enclosed coastal bodies of water which has a free connection to the open sea and where freshwater mixes with saltwater
Estuarine Of estuaries.
Estuary A semi-enclosed coastal body of water which has a free connection to the open sea and where freshwater mixes with saltwater
EU European Union
Eulerian Observation of flow field from a fixed point of reference (e.g. using a fixed position current meter).
Euphotic zone Surface waters to a depth of approximately 80-100 m; the lit region that extends virtually from the water surface to the level at which photosynthesis fails to occur because of reduced light penetration.
Eutrophication Enrichment of waters with nutrients, primarily phosphorus, causing abundant aquatic plant growth. Frequently resulting in oxygen depletion below the surface layer of a water body.
Exponential Mathematical function defined as the limiting value of (1 + 1/m)m as m approaches infinity, e = 2.718.
Extreme The value expected to be exceeded one, on average, in a given (long) period of time.
Extreme high water The highest elevation reached by the sea as recorded by a tide gauge during a given period.
Extreme low water The lowest elevation reached by the sea as recorded by a tide gauge during a given period.
Fauna Animal life
Fetch Distance over which a wind acts to produce waves - also termed 'fetch length'.
Flandrian transgression Rise in sea levels resulting in marine flooding of coastal land during the last 10,000 years.
Flocculation The process by which suspended colloidal or very fine particles coalesce and agglomerate into well-defined hydrated floccules of sufficient size to settle more rapidly.
Flood current (flood) The movement of a tidal current toward the shore or up a tidal river or estuary.
Flora Plant life
Flushing time The time required to remove or reduce (to a permissible concentration) any dissolved or suspended contaminant in an estuary or harbour.
Fluvial Of rivers.
Foreshore Intertidal area below highest and above lowest tide level.
Freshwater Water that contains no salts and is therefore not saline.
Geomorphology Landform processes, origin and history.
GIS Geographical Information System. A database of information which is geographically orientated, usually with an associated visualisation system.
Glacial From a glacier and the formations/sediments they make.
Gravel Beach material, coarser than sand but finer than pebbles (2-4 mm diameter). Note that 'gravel' beaches commonly contain material in range from 2-256mm.
Groyne Narrow, roughly shore-normal structure built to reduce longshore currents and/or to trap and retain beach material. Most groynes are of timber or rock and extend from a seawall or the backshore well onto the foreshore and rarely even further offshore.
Groyne bay The beach compartment between two groynes.
Hrms Root mean square wave height.
Hsig Significant wave height = average height of the waves which comprise the highest 33% of waves in a given sample period (typically 20 to 30 minutes).
ha Hectares (1 ha being equivalent to approximately 2.4 acres).
Habitat The local environment occupied by an organism.
Habitat creation The recreation of a natural habitat by man.
Harmonic Analysis Process of measuring or calculating the relative amplitudes and frequencies of all the significant harmonic components present in a given wave form.
Harmonic constants The amplitudes and epochs of the harmonic constituents of the tide or tidal current at any place.
Harmonic function In its simplest form, a quantity that varies as the cosine of an angle that increases uniformly with time. It may be expressed by the formula: y = A cos at, in which y is a function of time (t), A is a constant coefficient, and a is the rate of change in the angle at.
HAT Highest Astronomical Tide
Head The difference in water level at either end of a strait, channel, inlet, etc.
High water (HW) The maximum height reached by a rising tide.
High water mark A line or mark left upon tide flats, beach, or along shore objects indicating the elevation of the intrusion of high water.
Hindcast The prediction of wave characteristics using meteorological information as opposed to the measurements of these features.
Hinterland The infrastructure and transportation routes associated with the port, used to define the area of land behind a port
Hmax Maximum wave height in a recorded burst of raw data.
Hmean Mean wave height.
HMWBs Heavily Modified Water Bodies
Holocene The last 10,000 years in the geological timescale.
HPLC High Performance Liquid Chromatography
HTA Historical Trends Analysis
HW High Water
HWM High water Mark
Hydrodynamic The processes and science associated with the flow and motion in water produced by applied forces.
Hydrodynamic The flow and motion in water produced by applied forces
IECS Institute of Estuarine and Coastal Studies
Inshore Areas where waves are transformed by interaction with the seabed.
Intertidal The area between the MHWS and MLWN tidal levels in a coastal region
Intertidal zone The zone influenced by tidal action commonly taken between some upper limit such as MHWS and a lower limit such as MLWS.
Inverse barometer effect The inverse response of sea level to changes in atmospheric pressure. A static reduction of 1.005 mb in atmospheric pressure will cause a stationary rise of 1 cm in sea level.
Invertebrates Animals lacking a dorsal column of vertebrae or a notochord.
Ipswichian The last interglacial - A warm geological period of high sea levels about 140,000 years ago.
Isobath Line connecting points of equal depth, a seabed contour.
JNCC Joint Nature Conservation Committee
kgm-3 Kilograms of substance per cubic metre of volume, the mass of unit of a substance is its density.
Lag deposit Residual accumulation of coarse fragments left behind after waves/currents have winnowed and washed away finer material.
Lagrangian An observation that moves with the field of flow (e.g. float tracking).
Lagrangian Observation that moves with the field of flow (e.g. float tracking)
LAT Lowest Astronomical Tide
Leachate Water that has passed through a soil and that contains soluble material removed from that soil.
Leaching The downward movement of a material in solution through soil.
LiDAR Light Detection and Range
Lithology The general character of a rock or sediment expressed in terms of its mineral composition, its texture and grain size and included structures.
Littoral Of, or pertaining to, the shore.
Littoral drift, littoral transport The movement of beach material in the littoral zone by waves and currents. Includes movement parallel (longshore drift) and perpendicular (cross-shore transport) to the shore.
LNR Local Nature Reserve
Locally generated waves Waves generated within the immediate vicinity, say within 50 km, of the point of interest.
Long Wave Waves with periods greater than 30 seconds.
Longshore Parallel and close to the coastline.
Longshore bar Bar running approximately parallel to the shoreline.
Longshore drift Movement of (beach) sediments approximately parallel to the coastline.
Low water (LW) The minimum height reached by a falling tide.
Lunar tide That part of the tide on the Earth due solely to the Moon as distinguished from that part due to the Sun.
LW Low Water
LWM Low Water Mark
m Metre.
m3 Cubic metres.
Macrophyte A member of the macroscopic plant life, especially of a water body.
Macroscopic Large enough to be observed by the naked eye.
Macro-tidal An area with a high tidal range.
Magaripple Underwater sand dunes with a wavelength (spacing) of 3-30 m.
Maintenance dredging Dredging concerned with the preservation of navigational channels and berths.
Mean range of tide (Mn) The difference in height between mean high water and mean low water.
Meteorological tides Tidal constituents having their origin in the daily or seasonal variations in weather conditions which may occur with some degree of periodicity.
mgl-1 Milligrams of substance (dry weight) per litre of water.
MHW Mean High Water
MHWM Mean High Water Mark
MHWN Mean High Water Neaps
MHWS Mean High Water Springs
MHWST Mean High Water Spring Tide
MLR Mean Tidal Range
MLW Mean low water
MLW Mean low water
MLWM Mean Low Water Mark
MLWN Mean Low Water Neaps
MLWS Mean Low Water Springs
mm Millimetres 1,000 mm = 1 m.
Modelling A representation of a real system in terms of the structural organisation and functioning. Numerical models are a specific type of model where the components are capable of being represented mathematically
Morphology The structure and form of the land.
MSL Mean Sea Level
Mudflats Expanses of mud which are periodically exposed at low tide often found adjacent to saltmarshes.
NAO North Atlantic Oscillation
NE Natural England
Neap tide Tides over a 14 day period with lowest tidal range between high and low water
Nearshore The zone that extends from the swash zone to the position marking the start of the offshore zone, typically at water depths of the order of 20 m.
Ness Roughly triangular promontory of land jutting into the sea, often consisting of mobile material, i.e. a beach form.
NNR National Nature Reserve
Numerical modelling Refers to analysis of coastal processes using computational models.
ODN Ordnance Datum Newlyn the standard reference level for OS maps throughout the UK.
Offshore The zone beyond the nearshore zone where sediment motion induced by waves alone effectively ceases.
Order of magnitude Within a factor of ten; 1 x 101 = 10, 1 x 102 = 100, 1 x 103 = 1000
Organism Any living animal or plant; anything capable of carrying on life processes.
OS Ordnance Survey
Osmosis Diffusion of a solution through a semi-permeable membrane into a more concentrated solution, tending to equalise the concentrations on both sides of the membrane.
OSPAR The Convention for the Protection of the Marine Environment of the North-East Atlantic
Overtide A harmonic tidal (or tidal current) constituent with a speed that is an exact multiple of the speed of one of the fundamental constituents derived from the development of the tide-producing force. The presence of overtides is usually attributed to shallow water conditions.
Oxidation The combination of oxygen with a substance, or the removal of hydrogen from it or, more generally, any reaction in which an atom loses electrons.
Oxygenation The process of adding dissolved oxygen to a solution.
Pathogen An organism capable of eliciting disease symptoms in another organism.
PCA Principal Components Analysis
Peak Hmax Highest maximum wave height recorded during a storm event.
Peak Hsig Highest significant wave height recorded during a storm event.
Peak Wave Power Maximum wave power level recorded during a storm event.
Pebbles Beach material usually well-rounded and between about 4 mm to 75 mm in diameter.
Pelagic Term applied to organisms of the plankton and nekton which inhabit the open water of a sea or lake.
Pelagic Animal life that is found in the water column (fish, zooplankton, etc)
Percentage Exceedance Percentage of time that a given value is exceeded.
Percentage Occurrence Percentage of time that given value (or range of values) occurs.
Perigean tides or tidal currents Tides of increased range or tidal currents of increased speed occurring monthly as the result of the Moon being in perigee.
Perigee The point in the orbit of the Moon or man-made satellite nearest to the Earth. The point in the orbit of a satellite nearest to its companion body.
Perihelion The point in the orbit of the Earth (or other planet, etc.) nearest to the Sun.
pH Value taken to represent the acidity or alkalinity of an aqueous solution. It is defined as the negative logarithm of the hydrogen ion acidity of the solution.
Photosynthesis The conversion of carbon dioxide to carbohydrates in the presence of chlorophyll using light energy. General equation:

CO2 + 2H2O => (CH2O) + O2 + H2O
Physical models Refers to the investigation of coastal processes using a scaled model.
PLA Port of London Authority
Pleistocene The geological period extending from around two million years to 10,000 years before present, characterised by glacial and interglacial periods.
Plunging Waves The wave crest breaks suddenly and with tremendous force by curling over a near vertical wave face.
Pocket beach A beach, usually small, between two headlands.
Pressure Sensor A pressure transducer sensing device for water level measurement.
Progradation An extension of a coastal landform by sedimentation.
R&D Research & Development
Range of tide The difference in height between consecutive high and low waters.
RBMPs River Basin Management Plans
Receiving environment Expression used to identify the environment affected by a specific impact. Sometimes also referred to as the “receptor”
Recharge The anthropogenic placement of dredged sediment in intertidal areas
Reclamation An area of land converted from the sea usually involving conversion of intertidal or subtidal areas to supratidal areas.
Reflected Wave That part of an incident wave that is returned seaward when a wave impinges on a steep beach, barrier, or other reflecting surface.
Refraction The tendency of wave crests to become parallel to bottom contours as waves move into shallower waters. This effect is caused by the shoaling process which slows down waves in shallower waters.
Relative mean sea level change A local change in mean sea level relative to the land. May be composed of both an absolute mean sea level change component as well as a vertical land movement change component.
Return Period Expected average interval between the occurrences of events at a particular threshold.
RMS value Root Mean Square value – statistical measure of magnitude of a varying quantity and e.g. also can be used as a measure of error between model and measured values
SAC Special Area of Conservation
Salinity The inorganic ionic solutes (salts) present seawater
Salinity (S) The total amount of solid material in grams contained in 1 kilogram of sea water when all the carbonate has been converted to oxide, the bromine and iodine replaced by chlorine, and all organic matter completely oxidized. S(‰) = 1.806,55 x Cl (‰) Where Cl(‰) is chlorinity in parts per thousand.
Saltmarshes Flat areas of finely deposited silts that are occasionally inundated by seawater  and dominated by salt tolerant (halophytic) communities of plants. Located in the intertidal zone.
SAM Scheduled Ancient Monument
Sea Level Rise The long-term trend in mean sea level
Sea Waves Waves in coastal waters resulting from the interaction of different wave trains and locally generated waves. Typically, sea waves are of short wave length and of disordered appearance
Sediment transport The transportation of sedimentary particles by water or air
Seiche A stationary wave usually caused by strong winds and/or changes in barometric pressure. Found in lakes, semi enclosed bodies of water, and in areas of the open ocean.
Semidiurnal Having a period or cycle of approximately one-half of a day
Shallow water Water of such a depth that surface waves are noticeably affected by bottom topography. Typically a water depth equivalent to less than half the wavelength.
Shingle A loose term for coarse beach material, a mixture of gravel, pebbles and larger material, often well-rounded and of hard rock (e.g. chert, flint, etc) with a modal grain size exceeding 5 mm.
Shoaling The influence of the seabed on wave behaviour resulting in a reduction in wave speed, a shortening in wave length and an increase in wave height.
Shoreline The interface between land and sea.
Shoreline management The development of strategic, long-term and sustainable coastal defence policy. Can also relate to managing the natural environment in terms of it's habitat and biodiversity.
Side-scan sonar A geophysical technique for recording the texture and morphology of the seabed.
Significant wave height The average height of the highest one-third of the waves in a given Sea State.
Silt Sediment particles with a grain size between 0.004 mm and 0.062 mm, i.e. coarser than clay particles but finer than sand.
SINC Sites of Importance for Nature Conservation
Slack water (slack) The period of low or zero current speed near the time of turning of the current between flood and ebb tides.
SLR Sea Level Rise
SMP Shoreline Management Plan
Soft defences Usually refers to beaches (natural or man-made) but may also relate to energy-absorbing beach-control structures, including those constructed of rock, where these are used to control or redirect coastal processes rather than opposing or preventing them. In contrast to hard defences such as concrete sea walls.
Solar tide The part of the tide that is due to the tide-producing force of the Sun.
SPA Special Protection Area
Spatial Variability within space.
Spilling Waves The wave crest breaks gradually as the wave travels to the shore. Characterised by the appearance of white water at the crest.
Spit A narrow accumulation of sand or shingle, lying generally in line with the coast, with one end attached to the land, the other projecting into the sea or across the mouth of an estuary .
Spring tide Tides over a 14 day period with highest tidal range between high and low water
Spring tides or tidal currents Tides of increased range or tidal currents of increased speed occurring semi-monthly as the result of the Moon being new or full.
SSSI Site of Special Scientific Interest
Stand of tide An interval at high or low water when there is no change in the height of the tide (see slack water).
Steady state Condition that is maintained over some time interval even though there are fluctuations taking place over shorter time intervals
Still-water level (SWL) The water level that would exist in the absence of waves.
Storm Event Period of high wave activity.
Storm surge The local change in the elevation of the ocean along a shore due to a storm.  Normally associated with a decrease in atmospheric pressure. It typically has a duration of a few hours.
Stratification Vertical layering or structure of a substance within the water column.
Stratigraphy The study of stratified rocks especially their sequence in time, character of the rocks and the correlation of beds in different localities.
Sublittoral see subtidal.
Sublittoral Along the shore, below the reach of lowest tide and out to the limit of wave activity
Substrate The base on which an organism lives and grows.
Subtidal Depths below the lowest reach of the tide.
Surf Beat Periodic rise and fall in coastal water levels caused by two or more wave trains arriving at the shoreline.
Surf Zone Coastal waters between the breaker zone and the swash zone characterised by broken swell waves moving shorewards in the form of bores. Typically in water depths of 5-10 m.
Surficial Of, or pertaining to, a surface, e.g. of a beach or the seabed.
Surging Waves The wave does not "break" but maintains its basic shape as it moves towards the shore, where it surges up the beach. Very little white water is evident before surging waves reach the shore.
Suspended load A mode of sediment transport in which the particles are supported and carried along by the fluid.
Swash Zone That area of the shoreline characterised by regularly spaced wave crests.
Swell (waves) Remotely wind-generated waves.  Swell characteristically exhibits a more regular and longer period and has longer crests than locally generated waves.
Tsig Significant period = average period of the waves used to define Hsig.
TBT Tributyltin
Temporal Variability with time
Terrestrial Of land
Threshold of motion The point at which the forces imposed on a sediment particle overcome its inertia and it starts to move.
Tidal bore A tidal wave that propagates up a relatively shallow and sloping estuary or river in a solitary wave form.
Tidal characteristics Those features relating to the time, range, and type of tide.
Tidal constants Tidal relations that remain practically constant for any particular locality. Tidal constants are classified as harmonic and non harmonic. The harmonic constants consist of the amplitudes and epochs of the harmonic constituents, and the non harmonic constants include the ranges and intervals derived directly from the high and low water observations.
Tidal current The lateral movement of water associated with the rise and fall of the tides.
Tidal cycle The period when the seawater level rises and falls once
Tidal difference Difference in time or height between a high or low water at a subordinate station and a reference station for which predictions are given in the Tide Tables.
Tidal limit The point to which the tide reaches in an estuary, the end of the saltwater intrusion.
Tidal prism Volume of water entering and leaving an estuary during each tide, i.e. the difference between low water volume and high water volume.
Tidal range Vertical difference in high and low water level.
Tidal wave The rise and fall in water level due to the passage of the tide.
Tide The periodic rise and fall of the water resulting from gravitational interactions between Sun, Moon, and Earth (see also tidal current).
Tide (water level) gauge An instrument for measuring the rise and fall of the tide (water level).
Tide curve A graphical representation of the tidal height over a tidal cycle.
Tide levels (1) High astronomical tide (HAT), lowest astronomical tide (LAT): the highest and lowest tidal levels, respectively, which can be predicted to occur under average meteorological conditions.

(2) Mean high water springs (MHWS): the height of mean high water springs is the average throughout a year of the heights of two successive high waters during those periods of 24 hours (approximately once a fortnight) when the range of the tide is greatest.

(3) Mean low water springs (MLWS): the height of mean low water springs is the average height obtained by the two successive low waters during the same periods.

(4) Mean high water neaps (MHWN): the height of mean high water neaps is the average of the heights throughout the year of two successive high waters during those periods of 24 hours (approximately once a fortnight) when the range of the tide is least.

(5) Mean low water neaps (MLWN): the height of mean low water neaps is the average height obtained by the two successive low waters during the same periods.

(6) Mean high water (MHW), mean low water (MLW): mean high/low water, as shown on Ordnance Survey Maps, is defined as the arithmetic mean of the published values of mean high/low water springs and mean high/low water neaps.
Tide Tables Tables which give daily predictions of the times and heights of high and low waters.
Tide-producing force That part of the gravitational attraction of the Moon and Sun which is effective in producing the tides on the Earth.
Tombolo A narrow sand or shingle bar linking a small island with another island or the mainland.
Topographic Delineation of the natural and artificial features of an area.
TraC Transitional and coastal
Transgression The invasion of large area of land by the sea in a relatively short period of time (geologically).
Tsunami Long period ocean waves generated by geological and tectonic disturbances below sea level.
Turbidity A measure of light obscuration by water. Turbidity increases as the amount of suspended sediments in the water column increase.
TW Transitional Waters
UK United Kingdom
UKHO United Kingdom Hydrographic Office
UKMO United Kingdom Meteorological Office
Updrift The direction opposite to that of the predominant longshore movement of beach material.
Water depth Distance between the seabed and the still-water level.
Water level Elevation of still-water level relative to some datum.
Wave caustic Point or line along which wave energy is focused by refraction.
Wave climate The seasonable and annual distribution of wave height, period and direction.
Wave direction Mean direction of wave energy propagation relative to true north.
Wave directional spectrum Distribution of wave energy as a function of wave frequency and direction.
Wave frequency The inverse of wave period.
Wave frequency spectrum Distribution of wave energy as a function of frequency.
Wave Height The vertical distance between a wave crest and the next trough.
Wave Length The distance between consecutive wave crests or wave troughs.
Wave Period The time taken for consecutive wave crests or wave troughs to pass a given point.
Wave Power The rate at which wave energy is transmitted in the direction of wave propagation. Normally expressed in kilowatts per metre of wave crest length.
Wave rose Diagram showing the long-term distribution of wave height and direction.
Wave Runup The vertical distance above mean water level reached by the uprush of water from waves across a beach or up a structure.
Wave Setup The increase in water level within the surf zone above mean still water level caused by the breaking action of waves.
Wave Train A series of waves originating from the same fetch with similar wave characteristics.
Wave transformation Change in wave energy due to the action of physical processes.
Wave-cut platform A near horizontal layer of solid rock stretching seaward from the toe of a beach.
Waverider Buoy A floating device used to measure water level variations caused by ocean waves.
WFD Water Framework Directive
Wind rose Diagram showing the long-term distribution of wind speed and direction.
Wind Setup The increase in mean sea level caused by the "piling up" of water on the coastline by wind.
Wind stress Tangential wind force on water surface.
Wind Waves The waves initially formed by the action of wind blowing over the sea surface.
µm 1x 106 microns (µm) = 1 m

Glossary index

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Last Modified on: 19 June 2011
Printed from the Estuary Guide on 29/08/2014 17:03:23