. índice . Prefacio . Preface . . aguas . 1 . 2 . 3 . 4 . 5 . 6 . . contamina 1 . 2 . 3 . 4 . 5 . 6 . . holocausto 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . 9 . 10 . 11 . 12 . 13 . . lineas 1 . 2 . 3 . 4 . . hidrotermias 1 . 2 . 3 . 4 . 5 . 6 . . nuevas 1 . 2 . 3 . . Reconquista 1 . 2 . . hidrogeo 1 . 2 . 3 . 4 . 5 . 6 . . esbozos 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . . corredorcentral 1 . 2 . 3 . 4 . 5 . . cordones 1 . 2 . 3 . 4 . 5 . . epiola 1 . 2 . 3 . 4 . 5 . 6 . . deriva 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . 9 . 10 . 11 . 12 . 13 . 14 . . archivo 1 . 2 . 3 . 4 . . Halcrow 1 . 2 . 3 . 4 . 5 . 6 . . frentehalino 1 . 2 . 3 . 4 . 5 . 6 . 7 . . emicampanaoculto 1 . 2 . 3 . 4 . 5 . 6 . 7 . . Costa del Plata 0 . 1 . 2 . 3 . 4 . 5 . 6 . . Costa del oro 1 . 2 . . IRSA 1 . 2 . 3 . 4 . . flujos . . segmentos . . pendientes 1 . 2 . 3 . 4 . 5 . 6 . . delta 1 . 2 . 3 . 4 . 5 . . propuesta . 1 . 2 . . correconvectivo 1 . 2 . 3 . 4 . 5 . 6 . . plataforma 1 . 2 . . termodinamica 1 . 2 . 3 . . ABL 1 . 2 . . congreso . . girh . . Acumar 1 . 2 . 3 . 4 . . evaluacion 1 . 2 . . BocaRiachuelo 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . 9 . 10 . 11 . 12 . 13 . 14 . 15 . 16 . 17 . 18 . 19 . 20 . . StoDomingo . . urgenciasatadas 1 . 2 . . inundabaires 1 . 2 . 3 . 4 . . sinsustento 1 . 2 . . emisarios 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . 9 . 10 . . UAG 1 . 2 . 3 . . áreas nuevas 1 . 2 . 3 . . acreencias 1 . 2 . 3 . 4 . 5 . . audiencia 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . 9 . . Valls 1 . 2 . . contrastes 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . 9 . 10 . . convexterna . . playas 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . 9 . . Plan Maestro 1 . 2 . 3 . . Parque Norte . 1 . 2 . . ribera . 1 . 2 . 3 . 4 . 5 . . jurisdiccion 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . 9 . 10 . 11 . 12 . . CSJNpisamr 1 . 2 . 3 . 4 . . zonas muertas . . Bermejo 1 . 2 . . Pilcomayo . . Uruguay 1 . 2 . . Parana . . Areco 1 . 2 . . Salado . . Samborombon . . PuntaPiedras . . Tuyú . . PuntaRasa 1 . 2 . . PuntaMedanos . . Mar Chiquita 1 . 2 . 3 . 4 . 5 . . Mar del Plata 1 . 2 . 3 . 4 . 5 . . Necochea . . Colonia . . MartinGarcia 1 . 2 . 3 . . Puertos 1 . 2 . . formula1 . . disocio . . senderos . . bajante . . . . oceano 1 . 2 . 3 . . fitoplancton . . diatomeas . . hidrolinea 1 . 2 . 3 . . sustentable. 1 . 2 . . agua 1 . 2 . 3 . . hielo1300 . . antarticflows . . antarticmelts . . derrame . . luna 1 . 2 . 3 . 4 . 5 . 6 . . Trinidad . . prospectivas . 1 . 2 . 3 . 4 . . SantaCruz . 1 . 2 . 3 . . volcanes . . ley particular . . baires2060 . . aereadores . . Guaire . . marpampeano 1 . 2 . 3 . 4 . 5 . 6 . 7 . . Tamesis . 1 . 2 . . viajesedextra . . arena . . hospedero . 1 . 2 . . index .

An english Preface for these pages mainly devoted to recognize the origin of stranded cuspate bars and litoral drifts; considering in addition the effects of hydrochemical and thermal boundary layers; open doors to renewed understandings.


Fluid Mechanics and their analogies around an "oblique wave", must be our bible?; or ?

paying attention to Heat, Mass Transfer and Thermodynamics could we better and much more easily and precisely explain the formations of strandplains, stranded bars, eolian beach ridges, cheniers, undercuttings, cuspate bars, swash bars, swash channels, litoral drifts, longshore currents, nearshore currents, eddy currents and accretions. See these finely embroideried accretions at the estuary of Caravelas.

On  homopycnal flow they relates the water in the receiving basin, being of the same density or being vertically mixed. But they never talk about hidrochemical parenthoods

or internal convective process. I never heard about a single relation between vertical mixtures and thermodynamical transfer processes; even if I imagine they know perfectly that. Never about a thermal boundary layer or a chemical boundary layer when they talk about hypopycnal flow.

They just appreciatte to recognize hydrodynamical boundaries layers, densities and viscosities; that in fact, in mathematical modelling at INA Instituto Nacional del Agua, seems not to be precisely so important when studying  estuary flows.

When they talk about turbulent flow, easily forget to talk about thermodynamical processes; they just refer, I repeat, to vertical or transversal directions.

Matters around  atmospheric convections seems not to them,  be easily comparable to  water convections. Even if water and air, both are fluids.

And even if they recognize quite well the existence of these matters, they have been captured some centuries ago by the marvellous "oblique wave", that explains everything to everyone in a common language and in the whole world. Look at this artistic levee pretending to force litoral drift, the medioeval comprehention they reach:

Faith on such a religious principles makes quite easy to follow their way; and practically impossible to invite any of the club to see with different instruments.

They recognize the extraordinary energy that moves the Gulf stream, but they don’t like to remember us the extraordinary effect of a thermal boundary layer preserving that energy becoming negative.


Never could they recognize such a boundary layer between the warmer waters flowing from a tributary along the shallow waters of our estuarial border, and the colder water of tidal advections, side by side and just separated by a virtual thermal boundary layer promoving the extraordinary cuspidate or cuspate sedimentation that we call “cordones litorales” and you call in many different ways.

Another question: how can they extrapolate the ratio of the practically null inertial force of waters on a deep sedimented and extremely plain craton, to the viscous force in fluid motion forgetting thermodynamical tools and internal convective processes; much more responsible on estuarial extreme plain surfaces, of these motions?

Remember a simple definiton of VISCOSITY (or internal friction):
that molecular property of a fluid that enables it to support tangential stresses for a finite time and thus to resist deformation. Resistance to flow.

How can they define the word “Estuary” just refering to the part of a river that is affected by tides; or the region near a river mouth in which the fresh water of the river mixes with the salt water of the sea and which received both fluvial and littoral sediment influx; and forgetting that the indoeuropean root *aidh meaning “burn”, will open inmediately their imaginations.

and from here repeat the spanish voices: ”estiaje”: minimal river flow; “estuante”: excesively warm, and also: ”estío”, summer, the same primigenial message.

Even when historical lingüistic gives them a clear help to open sight to thermodynamics, they insist to embrace just the generalities of a fabulous oblique wave.

See practical examples of the worst imaginable solutions at Mar Chiquita, on the Atlantic coast, near Mar del Plata, following the theory of the oblique wave promoving a nearshore current or "litoral drift" that they want with classic tools to kill.

Being in fact this current, if considered with extreme care, the way Nature preserved these beachs for thousand of years.


The same examples at Mar del Plata and Necochea.

I invite you to see these subjects, even if not translated to English, at least fairly well illustrated, in some of the following pages:

around thermodynamical flux corridors;

around the epilog of the oblique wave;

around geological disasters at Sanborombon Bay;

around "cordones litorales".

Sights I debt to my Muse Alflora

Francisco Javier de Amorrortu . 26.7.08


Brief english lexicography on subjects around shore dynamics and hidrology with fluid mechanic's sights.

May be either natural or artificial. Natural accretion is the buildup of land, solely by the action of the forces of nature, on a beach by deposition of water- or airborne material. Artificial accretion is a similar buildup of land by reason of an act of man, such as the accretion formed by a GROIN, BREAKWATER, or beach fill deposited by mechanical means. Also AGGRADATION.

A margin of a continental plate consisting of a continental shelf and slope, and an oceanic trench or basin.

ADVANCE (of a beach)
(1) A continuing seaward movement of the shoreline. (2) A net seaward movement of the shoreline over a specified time. Also PROGRESSION.

A term applied to shelves that presently experience deposition of river-derived sediments. See also DETRITUS.

(1) Rapid EROSION of the shore land by waves during a storm. (2) A sudden cutting off of land by flood, currents or change in course of a body of water.

The longitudinal profile of the water surface in an open channel where the depth of flow has been increased by an obstruction as a weir or a dam across the channel, by increase in channel roughness, by decrease in channel width or by a decrease of the bed gradient

A submerged or emerged embankment of sand, gravel, or other unconsoli­dated material built on the sea floor in shallow water by waves and currents. See BAYMOUTH BAR, CUSPATE BAR.

A bar essentially parallel to the shore, the crest of which is above normal high water level. Also called offshore barrier and BARRIER ISLAND.

The flat area, often marshy and populated with low vegetation, on the bay or lagoon side of a barrier island

The carrying away of beach materials by wave action, tidal currents, littoral currents, or wind.

The bottom of a watercourse, or any body of water.

Any deviation from a flat bed that is readily detectable by eye and higher than the largest sediment size present in the parent bed material; generated on the bed of an alluvial channel by the flow.

Sediment transport mode in which individual particles either roll or slide along the bed as a shallow, mobile layer a few particle diameters deep, the part of the load that is not continuously in suspension.

A nearly horizontal part of the beach or backshore formed by the deposit of material by wave action. Some beaches have no berms, others have one or several. (See Figure IV-1-2.)

(1) On a beach: a nearly horizontal plateau on the beach face or backshore, formed by the deposition of beach material by wave action or by means of a mechanical plant as part of a beach renourishment scheme. Some natural beaches have no berm, others have several. (2) On a structure: a nearly horizontal area, often built to support or key-in an armor layer.


The lower portion of the water flow that experiences frictional retardation based on its proximity to the bed

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

Hydraulic or mechanical movement of sand from the accreting updrift side to the eroding downdrift side of an inlet or harbor entrance. The hydraulic movement may include natural movement as well as movement caused by man.

A long, narrow wooded beach ridge or sandy hummock forming roughly parallel to a prograding shore, usually seaward of marsh and mud-flat deposits (as along the south coast of Louisiana)

A fine grained, plastic, sediment with a typical grain size less than 0.004 mm. Possesses electromagnetic properties which bind the grains together to give a bulk strength or cohesion. See SOIL CLASSIFICATION.

A type of wave in shallow water (i.e., where the depth of water is less than 1/8 to 1/10 the wavelength). The surface profile is expressed in terms of the Jacobian elliptic function cn u; hence the term cnoidal.

(1) A strip of land of indefinite width (may be several kilometers) that extends from the shoreline inland to the first major change in terrain features. (See Figure IV-1-2.) (2) The part of a country regarded as near the coast.

The land and sea area bordering the shoreline. (See Figure IV-1-2.)

(1) Those currents which flow roughly parallel to the shore and constitute a relatively uniform drift in the deeper water adjacent to the surf zone. These currents may be tidal currents, transient, wind-driven currents, or currents associated with the distribution of mass in local waters. (2) For navigational purposes, the term is used to designate a current in coastwise shipping lanes where the tidal current is frequently rotary.

General term used to encompass both coast protection against erosion and sea defense against flooding.

The natural processes which drive coastal hydro- and morphodynamics (e.g.winds, waves, tides, etc).

The plain composed of horizontal or gently sloping strata of clastic materials, generally representing a strip of sea bottom that has emerged from the sea in recent geologic time

Collective term covering the action of natural forces on the shoreline, and near shore seabed

A zone directly adjacent to the waterline, where only coast related activities take place. Usually this is a strip of some 100 m wide. In this strip the coastal defense activities take place. In this strip often there are restrictions to land use.

The transition zone where the land meets water, the region that is directly influenced by marine and lacustrine hydrodynamic processes. Extends offshore to the continental shelf break and onshore to the first major change in topography above the reach of major storm waves. On barrier coasts, includes the bays and lagoons between the barrier and the mainland.

(1) Technically, the line that forms the boundary between the coast and the shore. (2) Commonly, the line that forms the boundary between the land and the water, esp. the water of a sea or ocean.

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

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

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

Very slow, continuous downslope movement of soil or debris.

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

(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: (1) Periodic - due to the effect of the tides; such Currents may be rotating rather than having a simple back and forth motion. The currents accompanying tides are known as tidal currents; (2) Temporary - due to seasonal winds; (3) Permanent or ocean - constitute a part of the general ocean circulation. The term DRIFT CURRENT is often applied to a slow broad movement of the oceanic water; (4) Nearshore - caused principally by waves breaking along a shore.

One of the offshore currents flowing generally parallel to the shoreline in the deeper water beyond and near the surf zone; these are not related genetically to waves and resulting surf, but may be related to tides, winds, or distribution of mass.

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

The tidal current away from shore or down a tidal stream. Usually associated with the decrease in the height of the tide.


Any of the parts of the nearshore current system that flow parallel to shore before converging and forming the neck of the RIP CURRENT.

The tidal current toward shore or up a tidal stream. Usually associated with the increase in the height of the tide.


Any current in the littoral zone caused primarily by wave action; e.g., LONGSHORE CURRENT, RIP CURRENT. See also CURRENT, NEAR­SHORE.

The littoral current in the breaker zone moving essentially parallel to the shore, usually generated by waves breaking at an angle to the shoreline.

A crescent-shaped bar uniting with the shore at each end. It may be formed by a single spit growing from shore and then turning back to again meet the shore, or by two spits growing from the shore and uniting to form a bar of sharply cuspate form.

The spit that forms in the lee of a shoal or offshore feature (BREAKWATER, island, rock outcrop) by waves that are refracted and/or diffracted around the offshore feature. It may eventually grow into a TOMBOLO linking the feature to the mainland.

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.

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

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.

(1) An ALLUVIAL DEPOSIT, usually triangular or semi-circular, at the mouth of a river or stream. The delta is normally built up only where there is no tidal or current action capable of removing the sediment at the same rate 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.

The nearly-level surface composing the landward portion of a large DELTA.

Mass (in kg) per unit of volume of a substance; kg/m3. For pure water, the density is 1000 .kg/m3, for seawater the density is usually more. Density increases with increasing salinity, and decreases with increasing temperature. More information can be found in "properties of seawater". For stone and sand, usually a density of 2600 kg/m3 is assumed. Concrete is less dense, in the order of 2400 kg/m3. Some types of basalt may reach 2800 kg/m3. For sand, including the voids, one may use 1600 kg/m3, while mud often has a density of 1100 - 1200 kg/m3.

Phenomenon of relative flow within water due to difference in density. For example, the salt-water wedge is a density current, as is a volcanic nuée ardente.

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.

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

Earth structure along sea or river in order to protect low lands from flooding by high water; dikes along rivers are sometimes called levees. Sometimes written as DYKE

The direction of predominant movement of littoral materials.

Along coasts with obliquely approaching waves there is a longshore (wave-driven) current. For this current, one can define an upstream and a DOWNSTREAM direction. For example, on a beach with an orientation west-east, the sea is to the north. Suppose the waves come from NW, then the current flows from West to East. Here, UPSTREAM is west of the observer, and east is downstream of the observer.

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.

Total area drained by a stream and its tributaries.

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, for cleanup of polluted sediments, and for placement of sand on beaches.

DRIFT (noun)
(1) Sometimes used as a short form for LITTORAL DRIFT. (2) The speed at which a current runs. (3) Floating material deposited on a beach (driftwood). (4) A deposit of a continental ice sheet; e.g., a DRUMLIN.

A broad, shallow, slow-moving ocean or lake current.

A particular reach of marine shore in which LITTORAL DRIFT may occur without significant interruption, and which contain any and all natural sources of such drift, and also any accretion shore forms accreted by such drift.

A shore with long, narrow channels, implying that subsidence of the coast has transformed the lower portions of river valleys into tidal estuaries.

In fluid dynamics, the ratio between the shear stress acting along any plane between neighboring fluid elements and the rate of deformation of the velocity gradient perpendicular to this plane.

High, landward margin of a flood-tidal shoal that helps divert ebb-tide currents around the shoal.

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.

The living organisms and the nonliving environment interacting in a given area, encompassing the relationships between biological, geochemical, and geophysical systems.

A circular movement of water formed on the side of a main current. Eddies may be created at points where the main stream passes projecting obstructions or where two adjacent currents flow counter to each other.


An ocean wave parallel to a coast, with crests normal to the shoreline. An edge wave may be STANDING or PROGRESSIVE. Its height diminishes rapidly seaward and is negligible at a distance of one wavelength offshore.

Resultant flow at right angles to and to the right of the wind direction (in the northern hemisphere) referred to as UPWELLING and DOWNWELLING.

The process by which a granular material can be sorted into its constituent particle sizes by means of a moving stream of fluid (usually air or water). Elutriators are extensively used in studies of sediments for determining Particle size distribution. Under certain circumstances wind, rivers and streams may act as elutriating agents.

Fill material, usually earth or rock, placed with sloping sides and with a length greater than its height. Usually an embankment is wider than a dike.

An indentation in the shoreline forming an open bay.

(1) The part of a river that is affected by tides. (2) The region near a river mouth in which the fresh water of the river mixes with the salt water of the sea and which received both fluvial and littoral sediment influx.

An artificially widened beach serving to nourish downdrift beaches by natural littoral currents or forces.

The currents which flow parallel to shore before converging and forming the neck of a RIP CURRENT.

The movement of a tidal current toward the shore or up a tidal stream. In the semidiurnal type of reversing current, the terms greater flood and lesser flood are applied respectively to the flood currents of greater and lesser velocity each day. The terms maximum flood and minimum flood are applied to the maximum and minimum velocities of a flood current the velocity of which alternately increases and decreases without coming to slack or reversing. The expression maximum flood is also applicable to any flood current at the time of greatest velocity.

1) A flat tract of land bordering a river, mainly in its lower reaches, and consisting of ALLUVIUM deposited by the river. It is formed by the sweeping of the meander belts downstream, thus widening the valley, the sides of which may become some kilometers apart. In time of flood, when the river overflows its banks, sediment is deposited along the valley banks and plains. (2) Synonymous with 100-year floodplain. The land area susceptible to being inundated by stream derived waters with a 1 percent chance of being equaled or exceeded in any given year.

Seaward-dipping sand platform dominated by flood-tidal currents, located on ebb-tidal shoal near the opening to the inlet.

The determination of the attenuating effect of storage on a river-flood passing through a valley by reason of a feature acting as control (e.g. a reservoir with a spillway capacity less than the flood inflow, or the widening or narrowing of a valley).

The bulge of sand formed at the landward mouth of TIDAL INLETS as a result of flow expansion.

The period of tide between low water and the succeeding high water; a rising tide. (See Figure II-5-16.)

Wall, retired from the seaward edge of the seawall crest, to prevent water from flowing onto the land behind.

An epoch of the QUATERNARY period, from the end of the PLEISTOCENE, about 8,000 years ago, to the present time. Syn: Recent.

A condition in which the outflow jet from a river or coastal inlet and the water in the receiving basin are of the same density or are vertically mixed.

HYDRAULICALLY EQUIVALENT GRAINS Sedimentary particles that settle at the same rate under the same conditions.

(1) The description and study of seas, lakes, rivers and other waters. (2) The science of locating aids and dangers to navigation. (3) The description of physical properties of the waters of a region.

Outflow from a river or coastal inlet in which a wedge of less dense water flows over the denser sea water.

(1) A short, narrow waterway connecting a bay, lagoon, or similar body of water with a large parent body of water. (2) An arm of the sea (or other body of water) that is long compared to its width and may extend a considerable distance inland. See also TIDAL INLET.

Generally, the deepest region of an inlet channel.

In beach terminology, the zone of variable width extending from the low water line through the breaker zone. Also SHOREFACE. (See Figure IV-1-2.)

Any current in or landward of the breaker zone.

Waves that occur within a fluid whose density changes with depth, either abruptly at a sharp surface of discontinuity (an interface), or gradually. Their amplitude is greatest at the density discontinuity or, in the case of a gradual density change, somewhere in the interior of the fluid and not at the free upper surface where the surface waves have their maximum amplitude.

A wave with fluid particles that do not revolve around an axis through their centers, although the particles themselves may travel in circular or nearly circular orbits. Irrotational waves may be PROGRESSIVE, STANDING, OSCILLATORY, or TRANSLATORY. For example, the Airy, Stokes, cnoidal, and solitary wave theories describe irrotational waves. Compare TROCHOIDAL WAVE.

A theoretical, progressive oscillatory wave first proposed by Gerstner in 1802 to describe the surface profile and particle orbits of finite amplitude, nonsinusoidal waves. The wave form is that of a prolate cycloid or trochoid, and the fluid particle motion is rotational as opposed to the usual irrotational particle motion for waves generated by normal forces. Compare IRROTATIONAL WAVE

Line connecting points on the seabed with an equal depth of sediment.

(1) (United States usage) On open seacoasts, a structure extending into a body of water, which is designed to prevent shoaling of a channel by littoral materials and to direct and confine the stream or tidal flow. Jetties are built at the mouths of rivers or tidal inlets to help deepen and stabilize a channel. (2) (British usage) WHARF or PIER. See TRAINING WALL.

The probability of two (or more) things occurring together.

Function specifying the joint distribution of two (or more) variables.

Average period of time between occurrences of a given joint probability event.

The dynamic viscosity divided by the fluid density.

Slow, smooth flow, with each drop of water traveling a smooth path parallel to its neighboring drops. Laminar flow is characteristic of low velocities, and particles of sediment in the flow zones are moved by rolling or SALTATION.

The direction toward which the wind is blowing; the direction toward which waves are traveling.

(1) A ridge or EMBANKMENT of sand and silt, built up by a stream on its flood plain along both banks of its channel. (2) A large DIKE or artificial EMBANKMENT, often having an access road along the top, which is designed as part of a system to protect land from floods.

A reach of the coast that is isolated sedimentologically from adjacent coastal reaches and that features its own sources and sinks. Isolation is typically caused by protruding headlands, submarine canyons, inlets, and some river mouths that prevent littoral sediment from one cell to pass into the next. Cells may range in size from a multi-hundred meter POCKET BEACH in a rocky coast to a BARRIER ISLAND many tens of kilometers long.


Deposits of littoral drift.

The movement of beach material in the littoral zone by waves and currents. Includes movement parallel (long shore drift) and sometimes also perpendicular (cross-shore transport) to the shore.

Rate of transport of sedimentary material parallel or perpendicular to the shore in the littoral zone. Usually expressed in cubic meters (cubic yards) per year. Commonly synonymous with LONGSHORE TRANSPORT RATE.

In beach terminology, an indefinite zone extending seaward from the shoreline to just beyond the breaker zone.

Parallel to and near the shoreline; ALONGSHORE.

A sand ridge or ridges, running roughly parallel to the shoreline and extending along the shore outside the trough, that may be exposed at low tide or may occur below the water level in the offshore.


Movement of (beach) sediments approximately parallel to the coastline.


An elongate DEPRESSION or series of depressions extending along the lower BEACH or in the offshore zone inside the BREAKERS.

(1) A tract of soft, wet land, usually vegetated by reeds, grasses and occasionally small shrubs. (2) Soft, wet area periodically or continuously flooded to a shallow depth, usually characterized by a particular subclass of grasses, cattails and other low plants.

A former salt marsh which has been protected by a DIKE.

MARSH, SALT  A marsh periodically flooded by salt water.

A single channel having a pattern of successive deviations in alignment which results in a more or less sinusoidal course.

Tidal range less than 2 m.

(1) The mutual interaction and adjustment of the seafloor topography and fluid dynamics involving the motion of sediment. (2) The coupled suite of mutually interdependent hydrodynamic processes, seafloor morphologies, and sequences of change.

A fluid-to-plastic mixture of finely divided particles of solid material and water.

A level area of fine silt and clay along a shore alternately covered or uncovered by the tide or covered by shallow water.

(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.

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

The current system caused primarily by wave action in and near the breaker zone, and which consists of four parts: the shoreward mass transport of water; longshore currents; seaward return flow, including rip currents; and the longshore movement of the expanding heads of rip currents. See also NEARSHORE CIRCULATION.

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

That part of a STANDING WAVE where the vertical motion is least and the horizontal velocities are greatest. Nodes are associated with CLAPOTIS and with SEICHE action resulting from wave reflections. Compare LOOP.

The process by which water flows through the interstices of a sediment. Specifically, in wave phenomena, the process by which wave action forces water through the interstices of the bottom sediment and which tends to reduce wave heights.

A GROIN with openings or voids large enough to permit passage of appreciable quantities of LITTORAL DRIFT through the structure.

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

(1) The youngest geologic period; includes the present time. (2) The latest period of time in the stratigraphic column, 0 B 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 ancestry becomes better understood.

(1) An arm of the ocean extending into the land, e.g., an ESTUARY. (2) A straight section of restricted waterway that is uniform with respect to discharge, slope, and cross-section.

(Geological) A synonym of HOLOCENE. See also QUATERNARY.

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

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

The process by which the energy of the wave is returned seaward.

REFRACTION (of water waves)
(1) The process by which the direction of a wave moving in shallow water at an angle to the contours is changed: the part of the wave advancing in shallower water moves more slowly than that part still advancing in deeper water, causing the wave crest to bend toward alinement with the underwater contours. (2) The bending of wave crests by currents. (See Figure II-6-11.)

The square root of the ratio of the distance between adjacent orthogonals in deep water to their distance apart in shallow water at a selected point. When multiplied by the SHOALING FACTOR and a factor for friction and percolation, this becomes the WAVE HEIGHT COEFFICIENT or the ratio of the refracted wave height at any point to the deepwater wave height. Also, the square root of the ENERGY COEFFICIENT.

A drawing showing positions of wave crests and/or orthogonals in a given area for a specific deepwater wave period and direction. (See Figure II-6-11.)

The dimensionless ratio of the inertial force to the viscous force in fluid motion, Re = LV_? where L is a characteristic length, ? the kinematic viscosity, and V a characteristic velocity. The Reynolds number is of importance in the theory of hydrodynamic stability and the origin of turbulence.

A long, narrow inlet, with depth gradually diminishing inward. Shorter and shallower than a FJORD.

A nearly continuous mound of beach material that has been shaped by wave or other action. Ridges may occur singly or as a series of approximately parallel deposits.

(1) Pertaining to the banks of a body of water. (2) Of, on or pertaining to the banks of a river.

A tidal current that flows continually with the direction of flow changing through all points of the compass during the tidal period. Rotary currents are usually found offshore where the direction of flow is not restricted by any barriers. The tendency for the rotation in direction has its origin in the deflecting force of the earth=s rotation and, unless modified by local conditions, the change is clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. The velocity of the current usually varies throughout the tidal cycle, passing through two maxima in approximately opposite directions and two minima with the direction of the current at approximately ninety degrees from the direction at the time of maximum velocity.

A marsh periodically flooded by salt water (also tidal marsh; sea marsh).

In this circulation type, the density-driven component dominates and two well-mixed layers are separated by a sharp HALOCLINE. The seawater entering the channel appears as a tongue or wedge.

That method of sand movement in a fluid in which individual particles leave the bed by bounding nearly vertically and, because the motion of the fluid is not strong or turbulent enough to retain them in suspension, return to the bed at some distance downstream. The travel path of the particles is a series of hops and bounds.

Sediment particles, often largely composed of quartz, with a diameter of between 0.062 mm and 2 mm, generally classified as fine, medium, coarse or very coarse. Beach sand may sometimes be composed of organic sediments such as calcareous reef debris or shell fragments.

(1) See BAR. (2) In a river, a ridge of sand built to or near the surface by river currents.

(1) Loose, fragments of rocks, minerals or organic material which are transported from their source for varying distances and deposited by air, wind, ice and water. Other sediments are precipitated from the overlying water or form chemically, in place. Sediment includes all the unconsolidated materials on the sea floor. (2) The fine grained material deposited by water or wind.

In the context of a strategic approach to coastal management, a length of coastline in which interruptions to the movement of sand or shingle along the beaches or near shore sea bed do not significantly affect beaches in the adjacent lengths of coastline.

Point or area at which beach material is irretrievably lost from a coastal cell, such as an estuary, or a deep channel in the seabed.

Point or area on a coast from which beach material is supplied, such as an eroding cliff, or river mouth.

The main agencies by which sedimentary materials are moved are: gravity (gravity transport); running water (rivers and streams); ice (glaciers); wind; the sea (currents and LONGSHORE DRIFT). Running water and wind are the most widespread transporting agents. In both cases, three mechanisms operate, although the particle size of the transported material involved is very different, owing to the differences in density and viscosity of air and water. The three processes are: rolling or traction, in which the particle moves along the bed but is too heavy to be lifted from it; SALTATION; and suspension, in which particles remain permanently above the bed, sustained there by the turbulent flow of the air or water.

The routes along which net sediment movement occurs.

The movement of water through small cracks, pores, interstices, out of a body of surface of subsurface water. The loss of water by infiltration from a canal, reservoir or other body of water or from a field. It is generally expressed as flow volume per unit of time.

SELECTIVE SORTING A process occurring during sediment transport that tends to separate particles according to their size, density, and shape. A well-sorted distribution contains a limited range of grain sizes and usually indicates that the depositional environment contains a narrow range of sediment sizes or a narrow band of depositional energy. A poorly-sorted distribution contains a wide range of grain sizes indicating multiple sources of sediment or a wide range of deposition energies.

(1) Commonly, water of such a depth that surface waves are noticeably affected by bottom topography. It is customary to consider water of depths less than one-half the surface wavelength as shallow water. See TRANSITIONAL ZONE and DEEP WATER. (2) More strictly, in hydrodynamics

(1) (noun) A detached area of any material except rock or coral. The depths over it are a danger to surface navigation. Similar continental or insular shelf features of greater depths are usually termed BANKS. (2) (verb) To become shallow gradually. (3) To cause to become shallow. (4) To proceed from a greater to a lesser depth of water.

Decrease in water depth. The transformation of wave profile as they propagate inshore.

The narrow strip of land in immediate contact with the sea, including the zone between high and low water lines. A shore of unconsolidated material is usually called a BEACH. (See Figure IV-1-2.). Also used in a general sense to mean the coastal area (e.g., to live at the shore).
The intersection of a specified plane of water with the shore or beach (e.g., the high water shoreline would be the intersection of the plane of mean high water with the shore or beach). The line delineating the shoreline on National Ocean Service nautical charts and surveys approximates the mean high water line.

(1) A submerged structure across a river to control the water level upstream. (2) The crest of a spillway.

Sediment particles with a grain size between 0.004 mm and 0.062 mm, i.e. coarser than clay particles but finer than sand. See SOIL CLASSIFICATION.

A small muddy marshland or tidal waterway which usually connects other tidal areas. See BAYOU.

A structure containing a gate to control the flow of water from one area to another.

SLUMP In mass wasting, movement along a curved surface in which the upper part moves vertically downward while the lower part moves outward.

Usually refers to beaches (natural or designed) 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.

A layer of weathered, unconsolidated material on top of bed rock; in geologic usage, usually defined as containing organic matter and being capable of supporting plant growth.

An arbitrary division of a continuous scale of grain sizes such that each scale unit or grade may serve as a convenient class interval for conducting the analysis or for expressing the results of an analysis. There are many classifications used (see Table III-1-2).

Linguoid, bar-like feature formed by ebb tidal current flow over a low area of an ebb shield.

(1) The shore or beach of the ocean or a large lake. The land bordering any large body of water, especially a sea or an arm of the ocean. (2) WHARF, QUAY, or roadway along a water body, esp. in a city.

A prograded shore built seawards by waves and currents.

A wave-cut platform; an elevated wave-cut terrace

The running aground of a ship upon a STRAND, ROCK, or bottom so that it is fast for a time.

An accumulation of debris (e.g. seaweed, driftwood and litter) cast up onto a beach, and lying along the limit of wave up rush. A shoreline above the present water level

(1) The study of stratified rocks (sediments and volcanics) especially their sequence in time. (2) The character of the rocks and the correlation of beds in different localities.

(1) A course of water flowing along a bed in the Earth. (2) A current in the sea formed by wind action, water density differences, etc.; e.g. the Gulf Stream. See also CURRENT, STREAM.

A narrow, deep and swift ocean current, such as the Gulf Stream. Opposite of DRIFT CURRENT.

Flow for which the Froude number is less than unity; surface disturbances can travel upstream.

Sinking or downwarping of a part of the earth=s surface.

Below the low-water datum; thus permanently .

Flow for which the Froude number is greater than unity; surface disturbances will not travel upstream.

(1) The material moving in suspension in a fluid, kept up by the upward components of the turbulent currents or by colloidal suspension. (2) The material collected in or computed from samples collected with a SUSPENDED LOAD SAMPLER. Where it is necessary to distinguish between the two meanings given above, the first one may be called the "true suspended load."

A sampler which attempts to secure a sample of the water with its sediment load without separating the sediment from the water.

The rush of water up onto the beach face following the breaking of a wave. Also UPRUSH, RUNUP.

Low broad sandy bars formed by sediment in the surf and swash zones, separated by linear depressions, or RUNNELS, running parallel to the shore. Sand bodies that form and migrate across ebb-tidal shoals because of currents generated by breaking waves.

(1) On the open shore, a channel cut by flowing water in its return to the present body (e.g., a rip channel). (2) A secondary channel passing through or shoreward of an inlet or river bar.

The thin wavy line of fine sand, mica scales, bits of seaweed, etc., left by the uprush when it recedes from its upward limit of movement on the beach face.

Sand sheet located between the main ebb channel of a coastal inlet and an adjacent barrier island.

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.

A horizontal or nearly horizontal natural or artificial topographic feature interrupting a steeper slope, sometimes occurring in a series.

Literally >land-formed= sediment that has found its way to the sea floor. The term is applied (a) to sediments formed and deposited on land (e.g., soils, sand DUNES), and (b) to material derived from the land when mixed in with purely marine material (e.g., sand or clay in a shelly limestone).

In hydraulics, the line joining the deepest points of an inlet or stream channel.

The point at which the forces imposed on a sediment particle overcome its inertia and it starts to move.

The maximum orbital velocity at which the sediment on the BED begins to move as waves approach shallow water.

(1) Marshy or muddy areas covered and uncovered by the rise and fall of the tide. A TIDAL MARSH. (2) Marshy or muddy areas of the seabed which are covered and uncovered by the rise and fall of tidal water.

(1) A natural inlet maintained by tidal flow. (2) Loosely, any inlet in which the tide ebbs and flows. Also TIDAL OUTLET.


That part of a river where the water level is influenced by the tide.

Shoals that accumulate near inlets due to the transport of sediments by tidal currents associated with the inlet.

The movement of fresh water and seawater that are mixed by the sloshing back and forth of the ESTUARY in response to ocean tides.

The periodic rising and falling of the water that results from gravitational attraction of the Moon and Sun and other astronomical bodies acting upon the rotating Earth. Although the accompanying horizontal movement of the water resulting from the same cause is also sometimes called the tide, it is preferable to designate the latter as TIDAL CURRENT, reserving the name TIDE for the vertical movement.

A wall or jetty to direct current flow.


The invasion of a large area of land by the sea in a relatively short space of time (geologically speaking). Although the observable result of a marine transgression may suggest an almost >instantaneous= process, it is probable that the time taken is in reality is thousands or millions of years. The plane of marine transgression is a plane of UNCONFORMITY.

In regard to progressive gravity waves, water whose depth is less than 2 but more than 1/25 the wavelength. Often called shallow water.

A theoretical, progressive oscillatory wave first proposed by Gerstner in 1802 to describe the surface profile and particle orbits of finite amplitude, nonsinusoidal waves. The wave form is that of a prolate cycloid or trochoid, and the fluid particle motion is rotational as opposed to the usual irrotational particle motion for waves generated by normal forces. Compare IRROTATIONAL WAVE

A condition of a liquid due to fine visible material in suspension, which may not be of sufficient size to be seen as individual particles by the naked eye but which prevents the passage of light through the liquid. (2) A measure of fine suspended matter in liquids.

A flowing mass of sediment-laden water that is heavier than clear water and therefore flows downslope along the bottom of the sea or a lake.

Any flow which is not LAMINAR, i.e., the stream lines of the fluid, instead of remaining parallel, become confused and intermingled.

Erosion of material at the foot of a Cliff or bank, e.g., a sea cliff, or river bank on the outside of a meander. Ultimately, the overhang collapses, and the process is repeated.

(1) A current below water surface flowing seaward; the receding water below the surface from waves breaking on a shelving beach. (2) Actually undertow is largely mythical. As the BACKWASH of each wave flows down the BEACH, a current is formed which flows seaward. However, it is a periodic phenomenon. The most common phenomena expressed as Aundertow@ are actually RIP CURRENTS.

The slope of the sea bottom. See SLOPE.

Along coasts with obliquely approaching waves there is a longshore (wave-driven) current. For this current one can define an upstream and a DOWNSTREAM direction. For example, on a beach with an orientation west-east with the sea to the north, the waves come from NW. Then the current flows from West to East. Here, upstream is West of the observer, and East is DOWNSTREAM of the observer.

The process by which water rises from a deeper to a shallower depth, usually as a result of offshore surface water flow. It is most prominent where persistent wind blows parallel to a coastline so that the resultant Ekman transport moves surface water away from the coast.

The velocity gradient within the BOTTOM BOUNDARY LAYER, displayed as a graph of height above the bed against the velocity of the flow.

VISCOSITY (or internal friction)
That molecular property of a fluid that enables it to support tangential stresses for a finite time and thus to resist deformation. Resistance to flow.

Part of the suspended load with particle sizes smaller than found in the bed; it is in near-permanent suspension and transported without deposition; the amount of wash load transported through a reach does not depend on the transport capacity of the flow; the load is expressed in mass or volume per unit of time.

Sediment deposited inland of a beach by overwash processes.

A low dam or wall across a stream to raise the upstream water level. Termed fixed crest weir when uncontrolled.

A jetty with a low section or weir over which littoral drift moves into a predredged deposition basin which is then dredged periodically.

Lands whose saturation with water is the dominant factor determining the nature of soil development and the types of plant and animal communities that live in the soil and on its surface (e.g. Mangrove forests).

The direction from which the wind is blowing.