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


Rill marks
Small drainage CHANNELS forming in the lower portion of a BEACH at LOW TIDE.

Rip Channel
A CHANNEL cut by seaward flow of RIP CURRENT, usually crosses a LONGSHORE BAR.

Rip current
A strong surface current of short duration flowing seaward from the shore. It usually appears as a visible band of agitated water and is the return movement of water piled up on the shore by incoming waves and wind. A rip current consists of three parts the FEEDER CURRENT flowing parallel to the shore inside the BREAKERS; the NECK, where the FEEDER CURRENTS converge and flow through the breakers in a narrow band or 'rip'; and the HEAD, where the current widens and slackens outside the breaker li…

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

Ripple
(1) The light fretting or ruffling on the surface of the water caused by a breeze. (2) The smallest class of waves and one in which the force of restoration is, to a significant degree, both surface tension and gravity.

Ripple marks
Undulations produced by fluid movement over sediments. Oscillatory currents produce symmetric ripples whereas a well-defined current direction produces asymmetrical ripples. The crest line of ripples may be straight or sinuous. The characteristic features of ripples depend upon current velocity, particle size, persistence of current direction and whether the fluid is air or water. Sand DUNES may be regarded as a special kind of ‘super`-ripple.

Riprap
(1) Broken stones used for revetment, toe protection for BLUFFS, or structures exposed to wave action, foundations, etc. (2) Foundation of wall or stones placed together irregularly. (3) (SMP) A layer, facing or protective mound of stones placed to prevent EROSION, scour or sloughing of a structure or EMBANKMENT; also the stone so used.

Rips
Agitation of water caused by the meeting of currents or by rapid current setting over an irregular bottom.

Risk analysis
Assessment of the total risk due to all possible environmental inputs and all possible mechanisms.

River
A natural stream of water larger than a brook or CREEK.

Rocks
An aggregate of one or more minerals rather large in area. The three classes of rocks are the following (1) Igneous rock â€` crystalline rocks formed from molten material. Examples are granite and basalt. (2) Sedimentary rock â€` A rock resulting from the consolidatrion of loose sediment that has accumulated in layers. Examples are sandstone, shale and limestone. (3) Metamorphic rock â€` Rock that has formed from preexisting rock as a result of heat or pressure.

Roller
(1) An indefinite term, sometimes considered to denote one of a series of long-crested waves which roll in upon a COAST, as after a storm. (2) Long, high SWELL, also called a GROUND SWELL.

Rotary current, tidal
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…

Run-up
the rush of water up a structure or BEACH on the breaking of a wave. The amount of run-up is the vertical height above stillwater level that the rush of water reaches.

Runnel
A corrugation or trough formed in the foreshore or in the bottom just offshore by waves or tidal currents.

Salient
Coastal formation of beach material developed by wave refraction and DIFFRACTION and longshore drift comprising of a bulge in the COASTLINE towards an offshore island or BREAKWATER, but not connected to it as in the case of a tombolo. See also ness, CUSP.

Salinity
Number of grams of salt per thousand grams of sea water, usually expressed in parts per thousand.

Salinity gradient
Change in salinity with DEPTH, expressed in parts per thousand per foot.

Salt-wedge estuary
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.

Saltation
A term used to describe the movement of a particle being transported by wind or water which is too heavy to remain in suspension. The particle is rolled forward by the current, generates lift and rises, loses the forward momentum supplying the lift and settles to the floor, where the process is repeated. The size of the particles which can be saltated depends upon the velocity of the current and its density, e.g., water will saltate larger particles than air at the same velocity.

Sand
An unconsolidated (geologically) mixture of inorganic soil (that may include disintegrated shells and coral) consisting of small but easily distinguishable grains ranging in size from about .062 mm to 2.0 mm.

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

Sand dune
A DUNE formed of sand.

Sand spit
A narrow sand EMBANKMENT, created by an excess of deposition at its seaward terminus, with its distal end (the end away from the point of origin) terminating in open water.

Sand waves
(1) Longshore sand waves are large-scale features that maintain form while migrating along the shore with speeds on the order of kilometers per year. (2) Large-scale asymmetrical bedforms in sandy river beds having high length to height ratios and continuous crestlines.

Scarp
See ESCARPMENT.

Scour protection
Protection against EROSION of the seabed in front of the toe.

Sea
(1) See OCEAN. (2) A large body of salt water, second in rank to an ocean, more or less LANDLOCKED and generally part of, or connected with, an ocean or a larger sea. (3) Waves caused by wind at the place and time of observation. (4) State of the ocean or lake surface, in regard to waves.

Sea breeze
A breeze that blows from the sea toward the land caused by unequal heating of land and water masses.

Sea cliff
A CLIFF situated at the seaward edge of the coast. See Figure 2.

Sea defenses
Works to prevent or alleviate flooding by the sea.

Sea grass
Members of marine seed plants that grow chiefly on sand or sand-mud bottom. They are most abundant in water less than 9 m deep. The common types are Eel grass (Zostera), Turtle grass (Thallasia) and Manatee grass (Syringodium).

Sea level rise
The long-term trend in MEAN SEA LEVEL.

Sea puss
A dangerous LONGSHORE CURRENT; a rip current caused by return flow; loosely, the submerged CHANNEL or INLET through a BAR caused by those currents.

Seacoast
The coast adjacent to the sea or ocean.

Seamount
Conical mountain rising 1000 m or more above the sea floor.

Seashore
(1) (Law) All ground between the ordinary high-water and low-water mark. (2) The SHORE of the SEA or OCEAN.

Seawall
(1) A structure built along a portion of a coast primarily to prevent EROSION and other damage by wave action. It retains earth against its shoreward face. (2) (SMP) A structure separating land and water areas primarily to prevent EROSION and other damage by wave action. Generally more massive and capable of resisting greater wave forces than a BULKHEAD.

Sechhi disk
Visibility disk used to measure the transparency of the water column.

Sediment
(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) (SMP) The fine grained material deposited by water or wind.

Sediment cell
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 nearshore sea bed do not significantly affect beaches in the adjacent lengths of COASTLINE. See LITTORAL CELL.

Sediment sink
A 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. See Figure 8.

Sediment source
A point or area on a COAST from which beach material arises, such as an eroding CLIFF, or river mouth. See Figure 8.

Sediment transport
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 wh…

Sediment transport paths
The routes along which net sediment movement occurs.

Seismic reflection
The return of part of the energy of seismic waves to the earth`s surface after the waves bounce off a rock boundary.

Seismic refraction
The bending of seismic waves as they pass from one material to another.

Seismic waves
A long-period wave caused by an underwater seismic disturbance or volcanic eruption.

Semidiurnal
Having a period or cycle of approximately one-half of a tidal day (12.4 hours). The predominating type of tide throughout the world is semidiurnal, with two high waterS and two low waters each tidal day. The tidal current is said to be semidiurnal when there are two flood and two EBB periods each day. See Figure 11.

Semidiurnal tide
Tides occurring twice daily. There are two high and two lows per tidal day. See Figure12.

Sensing, remote
The response of an instrument or organism to stimuli from a distant source.

Set (of current)
The direction towards which a current flows.

Setback
(SMP) A required open space, specified in shoreline master programs, measured horizontally upland from an perpendicualr to the ordinary high water mark.

Shallow water
Water of such DEPTH that surface waves are noticeably affected by bottom topography. Typically this implies a water DEPTH equivalent to less than half the wave length.

Shallow water wave
A PROGRESSIVE GRAVITY WAVE which is in water less than 1/25 the wave length in DEPTH.

Sheet erosion
The removal of a thin layer of surface material, usually topsoil, by a flowing sheet of water.

Sheet flow
Sediment grains under high sheer stress moving as a layer that extends from the bed surface to some distance below (on the order of a few cm). Grains are transported in the direction of fluid flow.

Sheet, smooth
A sheet on which field control and hydrographic data such as soundings, depth curves, and regions surveyed with a wire drag are finally plotted before being used in making a final chart.

Shelf, continental
See CONTINENTAL SHELF.

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.

Shoal
(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.

Shore
That strip of ground bordering any body of water which is alternately exposed, or covered by tides and/or waves. A SHORE of unconsolidated material is usually called a BEACH.

Shore terrace
A terrace made along a COAST by the action of waves and shore currents; it may become land by the uplifting of the shore or the lowering of the water.

Shoreface
The narrow zone seaward from the LOW TIDE SHORELINE permanently covered by water, over which the beach sands and GRAVELS actively oscillate with changing wave conditions.

Shoreline
(1) The intersection of a specified plane of water with the shore. (2) (SMP) All of the water areas of the state, including reservoirs and their associated uplands, together with the lands underlying them, except those areas excluded under RCW 90.58.030(2)(d).

Shoreline management
The development of strategic, long-term and sustainable COASTAL DEFENSE and land-use policy within a sediment cell.

Short-crested wave
A WAVE, the CREST LENGTH of which is of the same order of magnitude as the WAVE LENGTH. A system of SHORT-CRESTED WAVES has the appearance of hills being separated by troughs.

Significant wave
A statistical term relating to the one-third highest waves of a given wave group and defined by the average of their heights and periods.

Significant wave height
Average height of the highest one-third of the waves for a stated interval of time.

Significant wave period
Average period of the highest one-third of the waves for a stated interval of time.

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.

Slack water (slack tide)
The state of a tidal current when its velocity is near zero, especially the moment when a reversing current changes its direction and its velocity is zero. The term is also applied to the entire period of low velocity near the time of turning of the current when it is too weak to be of any practical importance in navigation. The relation of the time of slack water to the tidal phases varies in different localities. In some places slack water occurs near the times of high and low water, while in …

Slide
In mass wasting, movement of a descending mass along a plane approximately parallel to the slope of the surface.

Slip face
The steep, downwind slope of a dune; formed from loose, cascading sand that generally keeps the slope at the ANGLE OF REPOSE (about 34 degrees).

Slope
The degree of inclination to the horizontal. Usually expressed as a ratio, such as 1:25, indicating one unit rise in 25 units of horizontal distance; or in a decimal fraction (0.04). Also called GRADIENT.

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

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

Small diurnal range
Difference in height between MEAN LOWER LOW WATER (MLLW) and MEAN HIGHER HIGH WATER (MHHW). Applicable only when the type of tide is either SEMIDIURNAL or MIXED.

Soft defenses
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.

Soil
A layer of weathered, unconsolidated material on top of bed rock; often also defined as containing organic matter and being capable of supporting plant growth.

Soil horizons
Layers of soil that are distinguishable by characteristic physical or chemical properties.

Solitary wave
A wave consisting of a single ELEVATION (above the water surface) of height not necessarily small compared to the DEPTH, and neither followed or preceded by another ELEVATION or DEPRESSION of the water surface.

Sorting
Process of selection and separation of sediment grains according to their grain size (or grain shape or specific gravity).

Sound
(1) (noun) a relatively long arm of the sea or ocean forming a CHANNEL between an island and a mainland or connecting two larger bodies, as a sea and the ocean, or two parts of the same body; usually wider and more extensive than a STRAIT. (2) (verb) To measure the DEPTH of the water.

Sounding
A measured DEPTH of water. On hydrographic charts the soundings are adjusted to a specific plane of reference (SOUNDING DATUM).

Sounding datum
The plane to which SOUNDINGS are referred. See CHART DATUM.

Sounding line
A line, wire or cord used in SOUNDING. It is weighted at one end with a plummet.

Spit
(1) A long 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. See also ness. (2) (SMP) An accretion shoreform which extends seaward from and parallel to the SHORELINE. See Figure 5.

Spring range
The average SEMIDIURNAL RANGE occurring at the time of SPRING 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.

Spring tidal currents
Tidal currents of increased velocity occurring semi-monthly as the result of the moon being new or full.

Spring tide
A tide that occurs at or near the time of new or full moon, and which rises highest and falls lowest from the MEAN SEA LEVEL (MSL).

Stand of tide
An interval at high or LOW WATER when there is no discernable change in the height of the tide. The water level is stationary at high and LOW WATER for only an instant, but the change in level near these times is so slow that it is not usually perceptible. See SLACK TIDE.

Standing wave
(1) A type of wave in which the surface of the water oscillates vertically between fixed nodes without progressing. (2) A wave of essentially stable form which does not move with respect to a selected reference point.

Station, control
A point on the ground whose horizontal or vertical location is used as a basis for obtaining locations of other points.

Step
The nearly horizontal section which more or less divides the BEACH from the SHOREFACE. See Figure 3.

Stillwater level (SWL)
The surface of the water if all wave and wind action were to cease. In DEEP WATER this level approximates the midpoint of the wave height. In shallow water it is nearer to the trough than the crest. Also called the UNDISTURBED WATER LEVEL.

Stone
Quarried or artificially broken rock for use in construction.

Storm surge
A rise or piling-up of water against shore, produced by strong winds blowing ONSHORE. A storm surge is most severe when it occurs in conjunction with a high tide. See Figure 10.

Strait
A relatively narrow waterway between two larger bodies of water. See SOUND.

Strand
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.