Glossary

Accretion
The accumulation of sediment, deposited by tides, waves and wind.

Bathymetry
Spatial variability in the levels of the sea bed

Beach
A deposit of sediment (usually sand and gravel) at the interface between the land and the sea

Beach profile
A cross-section taken perpendicular to a given beach contour, extending from above high tide level down the beach face to low tide level

Boulder
A rounded rock on a beach, with diameter greater than 250mm

Chart datum (CD)
The level to which water depths are reduced on most UK Admiralty Charts; this level is that of the predicted lowest astronomical tide

Clay
A fine-grained, plastic, sediment with a typical grain size less than 0.004mm.

Coastal sediment cell
A coastal system within which the transport of sands and gravels is self-contained.

Coastal defence
General term used to encompass both coast protection against erosion and sea defence against tidal flooding

Coastal processes
A collective term covering the action of natural forces on the shoreline and nearshore sea bed

Coastal protection
Protection of land from erosion and encroachment by the sea

Cobble
A rounded rock on a beach, with diameter ranging from about 75 to 250mm

Cohesive sediment
Sediment containing significant proportion of clays, the electromagnetic properties of which cause the particles to bind together.

Deep water
Water too deep for waves to be affected by the sea bed

Deflation
Erosion of dunes by the wind

Depth-limited
Situation in which wave generation is limited by water depth

Downdrift
In the direction of nett longshore drift of beach material

Dunes
Accumulations of wind-blown sand on the backshore, usually in the form of small mounds or ridges, often stabilised by vegetation

Ebb
Period of time when the tide level is falling

Fetch
Distance over which a wind acts to produce waves

Fetch-limited
Situation in which wave generation is limited by fetch

Foreshore
The inter-tidal area below highest tide level and above lowest tide level

Gravel
Beach material with diameter of 2 - 4mm

Groyne
Narrow, roughly shore-normal structure built to reduce longshore transport and trap and retain beach material

Headland
A hard feature forming a local limit of the longshore extent of the beach

Highest astronomical tide (HAT)
The highest tide that can be expected to occur under the gravitational effects of the sun and the moon

Inter-tidal
The foreshore area below highest tide level and above lowest tide level

Littoral drift or longshore drift
The movement of beach material along the coast by waves and tidal currents

Lowest astronomical tide (LAT)
The lowest tide that can be expected to occur under the gravitational effects of the sun and the moon

Mean sea level
The average level of the sea over a period of about 1 year, taking account of all tidal effects

Mud flat
An area of fine silt usually exposed at low tide but covered at high tide

Nearshore
The zone which extends between the swash zone and the offshore zone, typically to water depths of the order of 20m

Offshore
The zone beyond the nearshore, usually in water depths of the order of 20m and beyond

Overtopping
Water carried over the top of a coastal defence

Pebble
Beach material usually well-rounded and with diameter 4 - 75mm

Revetment
A sloping surface of rock or concrete used to protect a shoreline against erosion

Sand
Sediment particles with a diameter of 0.062 - 2mm

Sea defences
Works to alleviate flooding from the sea

Sea level rise
Long term trend in mean sea level

Seawall
Solid coastal defence build parallel to the coastline

Sediment
Particulate matter derived from rocks, minerals or bioclastic debris

Sediment sink
Point, or area, at which beach material is deposited and lost from the active coastal sediment system. Typically this may be an estuary or sea bed channel.

Sediment source
Point, or area, on a coast from which beach material arises. Typically this may be an eroding cliff or a river mouth

Semi-diurnal
Having a period of half a tidal day, i.e. 12.4 hours

Shingle
A loose term for coarse beach material, a mixture of gravel, pebbles and larger material.

Shoreline
The interface between the land and the sea

Shore normal
A line at right angles to the shoreline

Significant wave height
The average height of the highest one-third of the waves in a given sea state

Silt
Sediment particles with a diameter between 0.004mm and 0.062mm

Spit
A long, narrow accumulation of sand or shingle, generally extending across an inlet or estuary mouth

Strand line
Accumulation of debris (seaweed, driftwood, litter) cast up onto a beach and lying around the limit of wave uprush

Surge
Changes in water level as a result of meteorological forcing

Swash zone
The zone of wave action on the beach

Swell
Remotely-generated waves

Tidal current
The movement of water associated with the rise and fall of the tide

Tidal range
Vertical difference in high and low water

Tide
The periodic rise and fall in the level of the water in oceans and seas as the result of the gravitational attraction of the sun and the moon

Topography
Spatial variability in the levels of the beach

Wave breaking
Reduction in wave energy and height in the surf zone due to limited water depth

Wave climate
The seasonal or annual distribution of wave height, period and direction

Wave diffraction
Process affecting wave propagation by which wave energy is altered due to change in propagation direction induced by a feature such as a headland, island or offshore breakwater

Wave direction
Mean direction of wave energy propagation relative to true North

Wave generation
Growth of a wave by wind

Wave height
The vertical distance between the trough of a wave and its following crest

Wavelength
Distance between two successive waves

Wave period
The time taken for two successive wave crests to pass the same point

Wave reflection
The return of part of an incident wave when it impinges on a reflecting surface, such as a seawall

Wave refraction
Process affecting wave propagation by which the direction of a wave moving in shallow water is affected by the sea bed contours to become more aligned with those contours

Wave shoaling
The transformation of a wave profile as it propagates from deep water to progressively shallower water and the effects of the sea bed start to become felt

Wave transformation
Change in wave energy due to the action of physical processes such as reflection, refraction, diffraction, shoaling and breaking