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ECY - Glossary of Coastal Terminology
Category: Earth and Environment > Coast
Date & country: 13/09/2007, USA
Words: 756


Coastal plain
The plain composed of horizontal or gently sloping strata of clastic material fronting the COAST and generally representing a strip of recently emerged sea bottom that has emerged from the sea in recent geologic times. Also formed by AGGRADATION.

Coastal processes
Collective term covering the action of natural forces on the shoreline, and the nearshore seabed.

Coastal zone
The land-sea-air interface zone around continents and islands extending from the landward edge of a BARRIER BEACH or SHORELINE of coastal bay to the outer extent of the CONTINENTAL SHELF.

Coastline
(1) Technically, the line that forms the boundary between the COAST and the SHORE. (2) Commonly, the line that forms the boundary between land and the water. (3) (SMP) The line where terrestrial processes give way to marine processes, TIDAL CURRENTS, wind waves, etc.

Cobble
Rounded rocks ranging in diameter from approximately 64 to 256 mm.

Colloid
As a size term refers to particles smaller than 0.00024 mm, smaller than CLAY size.

Comber
(1) A deepwater wave whose crest is pushed forward by a strong wind; much larger than a whitecap. (2) A long-period BREAKER.

Compass, surveyor`s
A compass for determining the magnetic azimuth of a line of sight by means of a sighting device, a graduated horizontal circle, and a pivoted magnetic needle.

Confluence
The junction of two or more river reaches or branches (the opposite of a BIFURCATION).

Conservation
The protection of an area, or particular element within an area, accepting the dynamic nature of the environment and therefore allowing change.

Continental shelf
(1) The zone bordering a continent extending from the line of permanent immersion to the DEPTH, usually about 100 m to 200 m, where there is a marked or rather steep descent toward the great depths. (2) The area under active LITTORAL processes during the Holocene period. (3) The region of the oceanic bottom that extends outward from the shoreline with an average slope of less than 1:100, to a line where the GRADIENT begins to exceed 1:40 (the CONTINENTAL SLOPE).

Continental slope
The declivity from the offshore border of the CONTINENTAL SHELF to oceanic depths. It is characterized by a marked increase in slope.

Contour current
A bottom current that flows parallel to the slopes of the continental margin (along the contour rather than down the slope).

Contour line
A line connecting points, on a land surface or sea bottom, which have equal ELEVATION. It is called an ISOBATH when connecting points of equal DEPTH below a DATUM.

Control network
Geodetic control together with the measured or adjusted values of the distances, angels, directions, or heights used in determining the coordinates of the control.

Control, geodetic
A set of control stations established by geodetic methods.

Control, ground
A point or set of points, the coordinates of which have been determined by survey, used for fixing the scale and position of a photogrammetrically determined network.

Control, horizontal
The geometric data relating to the horizontal coordinates of a control station.

Control, photogrammetric
Geodetic or other control established to provide scale, location, and orientation for photogrammetric network.

Control, vertical
The elevations (or approximations thereto) associated with control points.

Controlling depth
The least DEPTH in the navigable parts of a waterway, governing the maximum draft of vessels that can enter.

Coordinate system
A set of rules for specifying how coordinates are to be assigned to points.

Core
(1) A cylindrical sample extracted from a BEACH or seabed to investigate the types and DEPTHS of sediment layers. (2) An inner, often much less permeable portion of a BREAKWATER, or BARRIER BEACH.

Coriolis effect
Force due to the Earth's rotation, capable of generating currents. It causes moving bodies to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. The 'force' is proportional to the speed and latitude of the moving object. It is zero at the equator and maximum at the poles.

Coset
A group of units of CROSS-BEDDING which shows a uniform direction of current flow.

Countercurrent
A secondary current usually setting in a direction opposite to that of a main current.

Cove
A small sheltered recess in a shore or COAST, generally inside a larger EMBAYMENT.

Creek
(1) A stream, less predominant than a river, and generally tributary to a river. (2) A small tidal CHANNEL through a coastal MARSH.

Creep
Very slow, continuous downslope movement of soil or debris.

Crenulate
An indented or wavy shoreline beach form, with the regular seaward- pointing parts rounded rather than sharp, as in the CUSPATE type.

Cross sea
Confused, irregular state of the sea due to different groups of waves from different directions raised by local winds.

Cross-bedding
An arrangement of relatively thin layers of rock inclined at an angle to the more nearly horizontal BEDDING PLANES of the larger rock unit. Also referred to as cross-stratification.

Cross-shore
Perpendicular to the shoreline.

Current
(1) The flowing of water, or other liquid or gas. (2) That portion of a stream of water which is moving with a velocity much greater than the average or in which the progress of the water is principally concentrated. (3) Ocean currents can be classified in a number of different ways. Some important types include the following

Current meter
An instrument for measuring the velocity of a CURRENT. It is traditionally operated by a wheel equipped with vanes of cups which is rotated by the action of the impinging CURRENT. A recording device is provided to indicate the speed of rotation which is correlated with the velocity of the CURRENT.

Cusp
One of a series of short ridges on the FORESHORE separated by crescent-shaped troughs spaced at more or less regular intervals. Between these cusps are hollows. The cusps are spaced at somewhat uniform distances along beaches. They represent a combination of constructive and destructive processes.

Cuspate
Form of BEACH shoreline involving sharp seaward-pointing CUSPS (normally at regular intervals) between which the shoreline follows a smooth arc.

Cuspate foreland
A large, sandy cusp-shaped projection of the COAST. See Figure 5.

Cuspate sandkey
A cusp-shaped sand island.

Cuspate spit
A sandy cusp-shaped projection of the shoreline, found on both sides of some lagoons.

Daily retardation of tides
The amount of time by which corresponding tidal phases grow later day by day (about 50 minutes).

Dam
Structure built in rivers or estuaries, basically to separate water at both sides and/or to retain water at one side.

Datum
Any position or element in relation to which others are determined, as datum point, datum line, DATUM PLANE. See Figure 11.

Datum plane
A horizontal plane used as a reference from which to determine heights or DEPTHS. The plane is called a TIDAL DATUM when defined by a certain phase of the tide. Datum planes are referenced to fixed points known as BENCH MARKS, so that they can be recovered when needed. See also REFERENCE PLANE.

Davidson current
Deep-ocean boundary current off the west coast of the U.S. which brings warmer, saltier, low oxygen, high phosphate equatorial type water from low to high latitudes.

Debris line
A line near the limit of storm wave UPRUSH marking the landward limit of debris deposits.

Decay area
Area of relative CALM through which waves travel after emerging from the GENERATING AREA.

Decay distance
The distance through which waves travel after leaving the GENERATING AREA.

Decay of waves
The change which occurs in waves when they leave a GENERATING AREA and pass through a CALM (or region of lighter winds). In the process of decay the significant wave length increases and the SIGNIFICANT WAVE HEIGHT decreases.

Deep water
In regard to waves, where DEPTH is greater than one-half the WAVE LENGTH. Deep-water conditions are said to exist when the surf waves are not affected by conditions on the bottom.

Deep water waves
A wave in water the DEPTH of which is greater than one-half the WAVE LENGTH.

Deflation
The removal of loose material from a beach or other land surface by wind action.

Degradation
The geologic process by means of which various parts of the surface of the earth are worn away and their general level lowered, by the action of wind and water.

Delta
(1) An ALLUVIAL DEPOSIT, usually triangular, at the mouth of a river of other stream. It is normally built up only where there is no tidal or CURRENT action capable of removing the sediment as fast as it is deposited, and hence the DELTA builds forward from the COASTLINE. (2) A TIDAL DELTA is a similar deposit at the mouth of a tidal INLET, put there by TIDAL CURRENTS. (3) A WAVE DELTA is a deposit made by large waves which run over the top of a SPIT or BAR BEACH and down the landward side.

Density stratification
The lateral expansion of a sediment plume as it moves out of the distributary mouth, where salt and fresh water mix. This is most likely to occur where the speed of the river flow is moderate to low and the distributary mouth is relatively deep.

Density-driven circulation
Variations in salinity create variations in density in estuaries. These variations in density create horizontal pressure gradients, which drive estuarine circulation.

Depression
A general term signifying any depressed or lower area in the ocean floor.

Depth
Vertical distance from still-water level (or DATUM as specified) to the bottom.

Depth, controlling
See CONTROLLING DEPTH.

Design storm
Coastal protection structures will often be designed to withstand wave attack by the extreme DESIGN STORM. The severity of the storm (i.e. return period) is chosen in view of the acceptable level of risk of damage or failure. A DESIGN STORM consists of a DESIGN WAVE condition, a design water level and a DURATION.

Design wave
In the design of HARBORS, harbor works, etc., the type or types of waves selected as having the characteristics against which protection is desired.

Detached breakwater
A BREAKWATER without any constructed connection to the shore.

Detritus
Small fragments of rock which have been worn or broken away from a mass by the action of water or waves.

Diapositive
A positive photograph on a transparent medium.

Differential erosion - weathering
These features develop in rocks which have varying resistance to the agencies of EROSION and/or weathering so that parts of the rock are removed at greater rates than others. A typical example is the removal of soft beds from between harder beds in a series of sedimentary rocks. The term may be applied to any size of feature, from small-scale ‘etching` to the regional development of hills and valleys controlled by hard and soft rocks.

Diffraction
The phenomenon occurring when water waves are propagated into a sheltered region formed by a BREAKWATER or similar barrier that interrupts a portion of the otherwise regular train of waves, resulting in the multi-directional spreading of the waves.

Dike
Sometimes written as dyke; earth structure along a sea or river in order to protect LITTORAL lands from flooding by high water; DIKES along rivers are sometimes called levees.

Direction of current
Direction toward which CURRENT is flowing.

Direction of waves
Direction from which waves are coming.

Direction of wind
Direction from which wind is blowing.

Disperse
(1) To spread or distribute from a fixed or constant source. (2) To cause to become widely separated.

Dispersion
(1) Act of dispersing, or state of being dispersed. (2) The separation of waves by virtue of their differing rates of travel.

Diurnal
Literally of the day, but here meaning having a period or a tidal day, i.e. about 24.84 hours. See Figure 11.

Diurnal current
The type of tidal CURRENT having only one flood and one EBB period in the tidal day. A ROTARY CURRENT is DIURNAL if it changes its direction through all points of the compass once each tidal day. See Figure 11.

Diurnal inequality
The difference in height of the two high waters or of the two low waters of each day. Also, the difference in velocity between the two daily flood or EBB CURRENTS of each day. See Figure 11.

Dock
The slip or waterway between two piers, or cut into the land, for the reception of ships.

Double ebb (tidal)
An EBB CURRENT having two maxima of velocity separated by a smaller EBB velocity.

Double flood (tidal)
A flood CURRENT having two maxima of velocity separated by a smaller flood velocity.

Double tide
A double-headed tide; that is, a high water consisting of two maxima of nearly the same height separated by a relatively small DEPRESSION, or a LOW WATER consisting of two minima separated by a relatively small ELEVATION.

Downdrift
The direction of predominant movement of littoral materials.

Downwelling
A downward movement (sinking) of surface water caused by onshore Ekman transport, converging CURRENTS or when a water mass becomes more dense than the surrounding water.

Drainage basin
Total area drained by a stream and its tributaries.

Dredging
(SMP) Excavation or displacement of the bottom or SHORELINE of a water body. Dredging can be accomplished with mechanical or hydraulic machines. Most is done to maintain channel depths or berths for navigational purposes; other dredging is for shellfish harvesting or for cleanup of polluted sediments.

Drift current
A broad, shallow, slow-moving ocean or lake CURRENT. Opposite of STREAM CURRENT.

Drift sector
(SMP) A particular reach of marine shore in which LITTORAL DRIFT may occur without significant interruption, and which contais any and all natural sources of such drift, and also any accretion shoreforms accreted by such drift.

Drying beach
That part of the BEACH uncovered by water (e.g. at LOW TIDE). Sometimes referred to as subaerial beach.

Dunes
(1) Accumulations of windblown sand on the BACKSHORE, usually in the form of small hills or ridges, stabilized by vegetation or control structures. (2) A type of bed form indicating significant sediment transport over a sandy seabed.

Duration
In forecasting waves, the length of time the wind blows in essentially the same direction over the FETCH (GENERATING AREA).

Duration of ebb
The interval of time in which a tidal current is ebbing, determined from the middle of the slack waters.

Duration of fall
The interval from high water to low water.

Duration of flood
The interval of time in which a tidal current is flooding, determined from the middle of slack waters.

Duration of rise
The interval from LOW WATER to high water.

Duration, minimum
The time necessary for steady-state wave conditions to develop for a given wind velocity over a FETCH.

Dynamic equilibrium
Short term morphological changes that do not affect the morphology over a long period.

Ebb
Period when tide level is falling; often taken to mean the EBB CURRENT which occurs during this period.

Ebb current
The movement of a tidal current away from shore or down a tidal stream. In the semidiurnal type of reversing current, the terms GREATER EBB and LESSER EBB are applied respectively to the ebb currents of greater and lesser velocity of each day. The terms of MAXIMUM EBB and MINIMUM EBB are applied to the maximum and minimum velocities of a continuously running ebb current, the velocity alternately increasing and decreasing without coming to a slack or reversing. The expression MAXIMUM EBB is also …

Ebb interval
The interval between the transit of the moon over the meridian of a place and the time of the following strength of EBB.

Ebb strength
The EBB CURRENT at the time of maximum velocity.

Ebb tidal delta
The bulge of sand formed at the SEAWARD mouth of TIDAL INLETS as a result of interaction between tidal currents and waves. Also called inlet-associated bars and estuary entrance shoals.

Ebb tide
A nontechnical term used for falling tide or EBB CURRENT. The portion of the tidal cycle between high water and the following low water. See Figure 11.