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

Neap tide
Tide of decreased range occurring semimonthly as the result of the moon being in quadrature. The NEAP RANGE of the tide is the average semidiurnal range occurring at the time of neap tides and is most conveniently computed from the harmonic constants. The NEAP RANGE is typically 10 to 30 percent smaller than the mean range where the type of tide is either semidiurnal or mixed and is of no practical significance where the type of tide is DIURNAL. The average height of the high waters of the neap …

Nearshore
(1) In beach terminology an indefinite zone extending seaward from the SHORELINE well beyond the BREAKER ZONE. (2) The zone which 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.

Nearshore circulation
The ocean circulation pattern composed of the NEARSHORE CURRENTS and the COASTAL CURRENTS.

Nearshore current
The current system caused by wave action in and near the BREAKER ZONE, and which consists of four parts the shoreward mass transport of water; longshore currents; rip currents; and the LONGSHORE movement of the expanding heads of rip currents.

Neck
(1) The narrow strip of land which connects a peninsula with the mainland, or connects two ridges. (2) The narrow band (rip) of water flowing seaward through the surf. See also RIP CURRENT. See Figure 7.

Ness
Roughly triangular promontory of land jutting into the sea, often consisting of mobile material, i.e. a beach form.

Network
A set consisting of (a) stations for which geometric relationships have been determined and which are so related that removal of one station from the set will affect the relationships (distances, directions, coordinates, etc.) between the other stations; and (b) lines connecting the stations to show this interdependence.

Nip
The cut made by waves in a shoreline of emergence.

Nodal zone
An area in which the predominant direction of the LONGSHORE TRANSPORT changes.

Nourishment
The process of replenishing a BEACH. It may be brought about naturally, by LONGSHORE TRANSPORT, or artificially by the deposition of dredged materials.

Ocean
The great body of salt water which occupies two-thirds of the surface of the Earth, or one of its major subdivisions.

Ocean current
A nontidal current constituting a part of the general oceanic circulation.

Oceanography
That science treating of the oceans, their forms, physical features and phenomena.

Offshore
(1) In beach terminology, the comparatively flat zone of variable width, extending from the SHOREFACE to the edge of the CONTINENTAL SHELF. It is continually submerged. (2) The direction seaward from the shore. (3) 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 is small in comparison with the effect of wind. (4) The BREAKER ZONE directly seaward of the LOW TIDE line.

Offshore breakwater
A BREAKWATER built towards the seaward limit of the LITTORAL ZONE, parallel (or nearly parallel) to the shore.

Offshore currents
(1) Currents outside the surf zone. (2) Any current flowing away from the shore. See Figure 7.

Offshore wind
A wind blowing seaward from the land in the coastal area.

Onshore
A direction landward from the sea.

Onshore current
Any current flowing towards the shore.

Onshore wind
A wind blowing landward from the sea.

Open sea
Same as HIGH SEAS.

Opposing winds
A wind blowing in the opposite direction to that in which the waves are travelling.

Ordinary high water mark (OHWM)
(SMP) That mark that will be found by examining the bed and banks and ascertaining where the presence and action of waters are so common and usual, and so long continued in all ordinary years, as to mark upon the soil a character distinct from that of the abutting upland, in respect to vegitation as that condition exists on June 1, 1971, as it may naturally change thereafter, or as it may change thereafter in accordance with permits issued by a local government or the department.

Ordinary tide
This expression is not used in a technical sense by the U.S. Coast and Geodetic Survey, but the word 'ordinary' when applied to tides, may be taken as the equivalent of the word 'mean'. Thus 'ordinary HIGH WATER LINE' may be assumed to be the same as 'mean high water line'.

Orthophotograph
A photograph prepared from a perspective photograph by removing distortions and displacements of points caused by tilt, relief, and perspective.

Orthophotomap
A map made by assembling a number of orthophotographs into a single, composite picture.

Oscillation
A periodic motion backward and forward. To vibrate or vary above and below a mean value.

Outcrop
A surface exposure of bare rock, not covered by soil or vegetation.

Outfall
(1) The vent of a river, drain, etc. (2) A structure extending into a body of water for the purpose of discharging sewage, storm runoff or cooling water.

Outflanking
EROSION behind or around the inner end of a GROIN or BULKHEAD, usually causing failure of the structure.

Overfalls
Breaking waves caused by a conflict of currents, or by the wind moving against the current.

Oversplash
The water that splashes over the top of a BREAKWATER, seawall, etc.

Overtopping
Water carried over the top of a COASTAL DEFENSE due to wave run-up or surge action exceeding the crest height.

Overwash
(1) The part of the UPRUSH that runs over the crest of a BERM or structure and does not flow directly back to the ocean or lake. (2) The effect of waves overtopping a COASTAL DEFENSE, often carrying sediment landwards which is then lost to the beach system.

Partially mixed estuary
An ESTUARY that shows a small to moderate salinity change with DEPTH.

Particle size
in dealing with sediments and sedimentary rocks it is necessary that precise dimensions should be applied to such terms as CLAY, sand, pebble, etc. Numerous scales have been suggested, but in this work, the Wentworth-Udden scale is used, as it is widely accepted as an international standard. In the table which follows, particle size limits are shown, but within most groups further subdivision is possible; for example, sand may be described as very fine, medium, coarse, very coarse. particle size…

Peak period
The wave period determined by the inverse of the frequency at which the wave energy spectrum reaches its maximum.

Pebbles
Beach material usually well-rounded and between about 4 mm to 64 mm diameter.

Peninsula
An elongated portion of land nearly surrounded by water and connected to a larger body of land, usually by a NECK or an ISTHMUS.

Perigean range
The average semidiurnal range occurring at the time of the PERIGEAN TIDES and most conveniently computed from the harmonic constants. It is larger than the mean range where the type of tide is either semidiurnal or mixed and is of no practical significance where the type of tide is DIURNAL.

Perigean tidal currents
Tidal currents of increased velocity occurring monthly as the result of the moon being in perigree (i.e., at the point in its orbit nearest the Earth).

Perigean tides
tides of increased range occurring monthly as the result of the moon being in perigree.

Periodic current
A current caused by the tide-producing forces of the Moon and the Sun, a part of the same general movement of the sea that is manifested in the vertical rise and fall of the tides. See FLOOD CURRENT and EBB CURRENT.

Permanent current
A current that runs continuously independent of the tides and temporary cause. Permanent currents include the fresh water discharge of a river and the currents that form the general circulatory systems of the ocean.

Permeability
The property of bulk material (sand, crushed rock, soft rock in situ) which permit movement of water through its pores.

Permeable groin
A GROIN with openings large enough to permit passage of appreciable quantities of LITTORAL DRIFT.

Petrology
That branch of GEOLOGY which treats of the scientific study of rocks.

Photic zone
The zone extending downward from the ocean surface within which the light is sufficient to sustain photosynthesis. The DEPTH of this layer varies with water clarity, time of year and cloud cover, but is about 100 m in the open ocean. It may be considered the DEPTH to which all light is filtered out except for about one percent and may be calculated as about two and one-half times the DEPTH of a SECCHI DISK reading.

Photogrammetry
The science of deducing the physical dimensions of objects from measurements on images (usually photographs) of the objects.

Photomosaic
An assemblage of photographs, each of which shows part of a region, put together in such a way that each point in the region appears once and only once in the assemblage, and scale variation is minimized.

Physical geology
A large division of GEOLOGY concerned with earth materials, changes of the surface and interior of the earth, and the forces that cause those changes.

Pier
A structure, usually of open construction, extending out into the water from the shore, to serve as a landing place, recreational facility, etc., rather than to afford coastal protection.

Pile
A long substantial pole of wood, concrete or metal, driven into the earth or sea bed to serve as a support or protection.

Piling, sheet
Interlocking member of wood, steel, concrete, etc., subject to lateral pressure, driven individually to form an obstruction to percolation, to prevent movement of material for seawalls, stabilization of foundations, etc.

Piping
EROSION of closed flow CHANNELS (tunnels) by the passage of water through soil; flow underneath structures, carrying subsoil particles, may endanger the stability of the structure.

Pixel
An element of surface resulting from subdividing an image into the smallest identically shaped figures that give information about the location, intensity and perhaps color of the source, but such that no smaller subdivision will provide more information.

Placer deposits
MINERAL deposits consisting of dense, resistant and often economically valuable minerals which have been weathered from TERRIGENOUS ROCKS, transported to the sea and concentrated in marine sediments by wave or current action.

Placer mine
Surface mines in which valuable MINERAL grains are extracted from stream bar or beach deposits.

Planform
The outline or shape of a body of water as determined by the stillwater line.

Plateau
(1) (Geographical) an elevated plain, tableland or flat-topped region of considerable extent. (2) (Oceanographical) an ELEVATION from the bottom of the ocean with a more or less flat top and steep sides.

Pleistocene
An epoch of the Quaternary Period characterized by several glacial ages.

Plunge point
(1) For a PLUNGING WAVE, the point at which the wave curls over and breaks. (2) The final breaking point of the waves just before the water rushes up the BEACH.

Pocket beach
A BEACH, usually small, between two headlands.

Point
(1) The extreme end of a CAPE, or the outer end of any land area protruding into the water, usually less prominent than a CAPE. (2) (SMP) A low profile SHORELINE PROMONTORY of more or less triangular shape, the top of which extends SEAWARD.

Point bar
A stream bar deposited on the inside of a curve in the stream, where the water velocity is low.

Port
A place where vessels may discharge or receive cargo.

Preservation
Static protection of an area or element, attempting to perpetuate the existence of a given 'state'.

Profile, beach
See BEACH PROFILE

Progressive wave
A wave which is manifested by the progressive movement of the wave form.

Promontory
A high point of land extending into a body of water; a HEADLAND.

Quaternary
(1) The youngest geologic period; includes the present time. (2) The latest period of time in the stratigraphic column, 0 â€` 2 million years, represented by local accumulations of glacial (Pleistocene) and post-glacial (Holocene) deposits which continue, without change of fauna, from the top of the Pliocene (Tertiary). The QUATERNARY appears to be an artificial division of time to separate pre-human from post-human sedimentation. As thus defined, the QUATERNARY is increasing in duration as man`s …

Radar
An instrument for determining the distance and direction to an object by measuring the time needed for radio signals to travel from the instrument to the object and back, and by measuring the angle through which the instrument`s antenna has traveled.

Raised beach
A wave-cut platform, with or without a covering of beach materials, which is now raised above the present sea-level. See also REJUVENATION.

Random waves
The laboratory simulation of irregular sea states that occur in nature.

Range of tide
The difference in height between consecutive high and low waters. The MEAN RANGE is the difference between MEAN HIGH WATER and MEAN LOW WATER. The GREAT DIURNAL RANGE or DIURNAL RANGE is the difference in height between MEAN HIGHER HIGH WATER (MHHW) and MEAN LOWER LOW WATER (MLLW). Where the type of tide is DIURNAL, the mean range is the same as the DIURNAL range. See Figure 11.

Ravinement
UNCONFORMITIES in a transgressional sequence of deposits which take on a variety of forms based on wave energy and sediment supply.

Reach
(1) An arm of the ocean extending into the land. (2) A straight section of restricted waterway of considerable extent; may be similar to a NARROWS, except much longer in extent.

Recent
(Geological) A synonym of Holocene. See also QUATERNARY.

Recession
(1) A continuing landward movement of the shoreline. (2) A net landward movement of the shoreline over a specified time.

Recharge
The addition of new water to an AQUIFER or to the zone of saturation.

Rectification
The process of producing, from a tilted or oblique photograph, a photograph from which displacement caused by tilt has been removed.

Red tide
Discoloration of surface waters, most frequently in COASTAL ZONES, caused by large concentrations of microorganisms.

Reef
A ridge of rock or other material lying just below the surface of the sea.

Reef breakwater
Rubble mound of single-sized stones with a crest at or below sea level which is allowed to be (re)shaped by the waves.

Reference plane
The plane to which sounding and tidal data are referred.

Reference point
(1) A specified location (in plan elevation) to which measurements are referred. (2) In beach material studies, a specified point within the REFERENCE ZONE.

Reference station
A tide or current station for which tidal or tidal current constants have previously been determined and which is used as a standard for the comparison of simultaneous observations at a second station; also a station for which independent daily predictions are given in the tide or current tables from which corresponding predictions are obtained for other stations by means of differences or factors.

Reference zone
In regard to beach measuring procedure, the part of the FORESHORE subject to wave action (between the LIMIT OF UPRUSH and the LIMIT OF BACKWASH) at mid-tide stage. In areas of great tidal range a more complex definition is needed.

Reflected wave
That part of an INCIDENT WAVE that is returned (reflected) seaward when a wave impinges on a BEACH, seawall or other reflecting surface.

Reflection
The process by which the energy of the wave is returned SEAWARD.

Reflection, seismic
See SEISMIC REFLECTION.

Reflector
A surface, usually a rock or sediment layer, that strongly reflects seismic (sound) waves.

Refraction
The process by which the direction of a wave moving in shallow water at an angle to the bottom contours is changed. The part of the wave moving shoreward in shallower water travels more slowly than that portion in deeper water, causing the wave to turn or bend to become parallel to the contours. See Figure 13.

Regular waves
Waves with a single height, period and direction.

Residual (water level)
The components of water level not attributable to astronomical effects.

Resolution
(1) In general, a measure of the finest detail distinguishable in an object or phenomenon. (2) In particular, a measure of the finest detail distinguishable in an image.

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

Return period
Average period of time between occurrences of a given EVENT.

Reversing tidal current
A tidal current that flows alternately in approximately opposite directions with a SLACK WATER at each reversal of direction. Currents of this type usually occur in rivers and straits where the direction of flow is more or less restricted to certain CHANNELS. When the movement is towards the shore, the current is said to be flooding, and when in the opposite direction it is said to be ebbing.

Revetment
(1) A facing of stone, concrete, etc., to protect an EMBANKMENT, or shore structure, against EROSION by wave action or currents. (2) A retaining wall. (3) (SMP) Facing of stone, concrete, etc., built to protect a SCARP, EMBANKMENT or shore structure against erosion by waves of CURRENTS.