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

Strand line
An accumulation of debris (e.g. seaweed, driftwood and litter) cast up onto a BEACH, and lying along the limit of wave up rush.

Stratigraphy
(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.

Stream
(1) Any flow of water; a current. (2) A course of water flowing along a bed in the earth.

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

Structural geology
The branch of GEOLOGY concerned with the internal structure of bed rock and the shapes, arrangement, and interrelationships of rock units.

Sub-aerial beach
That part of the BEACH which is uncovered by water (e.g. at LOW TIDE sometimes referred to as DRYING BEACH).

Sub-tidal beach
The part or the BEACH (where it exists) which extends from LOW WATER out to the approximate limit of storm EROSION. The latter is typically located at a maximum water DEPTH of 8 to 10 m for moderate wave environments and is often identifiable on surveys by a break in the slope of the BED.

Subduction zone
Elongate region in which the sea floor slides beneath a continent or island arc.

Submarine canyon
V-shaped valleys that run across the CONTINENTAL SHELF and down the CONTINENTAL SLOPE. See Figure 8.

Submergent coast
A COAST in which formerly dry land has been recently drowned, either by land subsidence or a rise in seal level.

Subordinate station
A tide or current station at which a short series of observations has been obtained, which is to be reduced by comparison with simultaneous observations at another station having well-determined tidal or current constants.

Subsidence
Sinking or downwarping of a part of the earth`s surface.

Surf
(1) Collective term for BREAKERS. (2) The wave activity in the area between the SHORELINE and the outermost limit of breakers. (3) The term surf in literature usually refers to the breaking waves on shore and on reefs when accompanied by a roaring noise caused by the larger waves breaking.

Surf beat
irregular oscillations of water level within the SURF ZONE with periods in the order of several minutes.

Surf zone
The nearshore zone along which the waves become BREAKERS as they approach the shore. See Figure 6.

Surf zone
The zone of wave action extending from the water line (which varies with tide, surge, set-up, etc.) out to the most seaward point of the zone (BREAKER ZONE) at which waves approaching the COASTLINE commence breaking, typically in water DEPTHS of between 5 m and 10 m. See Figure 6.

Surface gravity wave (progressive)
(1) this is the term which applies to the WIND WAVES and SWELL of lakes and oceans, also called SURFACE WATER WAVE, SURFACE WAVE or DEEP WATER WAVE, (2) a progressive GRAVITY WAVE in which the disturbance is confined to the upper limits of a body of water. Strictly speaking this term applies to those progressive GRAVITY WAVES whose celerity depends only upon the wave length. See Figure 10.

Surface water wave
see SURFACE GRAVITY WAVE (PROGRESSIVE).

Surface wave
see SURFACE GRAVITY WAVE (PROGRESSIVE). See Figure 10.

Surge
(1) Long-interval variations in velocity and pressure in fluid flow, not necessarily periodic, perhaps even transient in nature. (2) The name applied to wave motion with a period intermediate between that of an ordinary wind wave and that of the tide. (3) Changes in water level as a result of meteorological forcing (wind, high or low barometric pressure) causing a difference between the recorded water level and that predicted using harmonic analysis, may be positive or negative.

Survey, control
A survey that provides coordinates (horizontal or vertical) of points to which supplementary surveys are adjusted.

Survey, hydrographic
A survey that has as its principal purpose the determination of geometric and dynamic characteristics of bodies of water.

Survey, photogrammetric
A survey in which monuments are placed at points that have been determined photogrammetrically.

Survey, topographic
A survey which has, for its major purpose, the determination of the configuration (relief) of the surface of the land and the location of natural and artificial objects thereon.

Suspended load
The finest of the beach sediments, light enough in weight to remain lifted indefinitely above the bottom by water turbulence.

Swash
(1) Same as UPRUSH. (2) A body of dashing, splashing water. (3) A BAR over which the ocean washes.

Swash bars
Low broad sandy BARS formed by sediment in the surf and swash zones, separated by linear depressions, or RUNNELS, running parallel to the SHORE.

Swash channel
A narrow sound or CHANNEL of water lying within a sandbank, or between a sandbank and a shore.

Swash mark
The thin wavy line of fine sand left by the UPRUSH when it recedes from its upward limit of movement on the BEACH FACE.

Swash zone
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. See Figure 6.

Swell
Waves that have traveled a long distance from their GENERATING AREA and have been sorted out by travel into LONG WAVES of the same approximate period.

Tectonic forces
Forces generated from within the earth that result in uplift, movement, or deformation of part of the earth`s crust.

Tectonics
The study of the major structural features of the Earth`s crust or the broad structure of a region.

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

Terrigenous sediments
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).

Thalweg
The line down the center of the main CHANNEL of a stream.

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

Tidal current
The alternating horizontal movement of water associated with the rise and fall of the tide caused by ASTRONOMICAL TIDE-producing forces.

Tidal datum
See REFERENCE PLANE.

Tidal day
See LUNAR DAY.

Tidal delta
See DELTA.

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

Tidal marsh
Same as TIDAL FLATS.

Tidal period
The interval of time between two consecutive like phases of the tide or tidal current. See Figure 11.

Tidal pool
A pool of water remaining on a BEACH or REEF after recession of the tide.

Tidal prism
(1) The total amount of water that flows into a HARBOR or out again with movement of the tide, excluding any fresh water flow. (2) (SMP) The volume of water present between MEAN LOW and MEAN HIGH TIDE.

Tidal range
See RANGE OF TIDE.

Tidal rise
The height of tide as referred to the DATUM of a chart. See Figure 11.

Tidal stand
An interval at high or LOW WATER when there is no observable 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.

Tidal wave
(1) A wave, in the oceans and seas, produced by tides and tidal currents. (2) Non-technical term in popular usage for an unusually high and destructive water level along a shore. It usually refers to STORM SURGE or TSUNAMI.

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

Tide
The periodic rising and falling of the water that results from gravitational attraction of the moon and sun 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. See Figure 11.

Tide gage
A device for measuring the rise and fall, and the current height of the tide.

Tide level
The height of the tide above a specified level.

Tide staff
A tide gage consisting of a vertical graduated staff from which the height of the tide can be read directly. It is called a fixed staff when it is secured in place so that it cannot be easily removed. A portable staff is one that is designed for removal from the water when not in use.

Tide station
The geographic location at which tidal observations are made. It is called a primary tide station when continuous observations are to be taken over a number of years to obtain basic tidal data for the locality. A secondary tide station is one operated over a short period of time to obtain data for a specific purpose.

Tide tables
Tables which give daily predictions of the times and heights of the tide. These predictions are usually supplemented by tidal differences and constants by means of which additional predictions can be obtained for numerous other places.

Tide, astronomic
The periodic change in magnitude and direction of gravity as caused by attraction of the Sun, Moon, and other members of the Solar system.

Tide, diurnal
See DIURNAL.

Tide, Ebb
See EBB TIDE.

Tide, flood
See FLOOD TIDE.

Tide, mixed
See MIXED TIDES.

Tide, neap
See NEAP TIDES.

Tide, semidiurnal
See SEMIDIURNAL, SEMIDIURNAL TIDE.

Tide, slack
See SLACK WATER.

Tide, spring
See SPRING TIDES.

Tide, wind
See WIND TIDE.

Tides, rip
See RIP.

Tides, types of
The characteristic form of the tide with special reference to the relation of the DIURNAL and semidiurnal waves. Tides are sometimes classified as DIURNAL, SEMIDIURNAL and MIXED, but there are no sharply defined limits separating the groups. The tide is said to be DIURNAL when the diurnal wave predominated and only a single high and single LOW WATER occur each day during the greater part of the month. The tide is SEMIDIURNAL when the semidiurnal wave predominates and two high and two low waters …

Toe
(1) Lowest part of sea- and portside breakwater slope, generally forming the transition to the seabed. (2) The point of break in slope between a dune and a beach face.

Tombolo
(1) Coastal formation of beach material developed by refraction, DIFFRACTION and LONGSHORE DRIFT to form a 'neck' connecting a COAST to an offshore island or BREAKWATER (see also salient). (2) (SMP) A causeway-like ACCRETION SPIT that connects an offshore rock or island to the main shore, or to another island. See Figure 5.

Tongue
A long narrow strip of land, projecting into a body of water.

Topographic map
A map on which elevations are shown by means of CONTOUR LINES.

Topography
The form of the features of the actual surface of the Earth in a particular region considered collectively.

Training wall
A wall or JETTY to direct current flow.

Transgression, marine
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 to be measured in millions of years. The plane of marine transgression is a plane of UNCONFORMITY. The reverse of a transgression is a REGRESSION.

Transitional water (zone)
In regard to PROGRESSIVE GRAVITY WAVES, water whose DEPTH is less than one-half, but more than 1/25, the wave length, also called a SHALLOW WATER WAVE.

Transverse bar
A BAR which extends approximately right angles to SHORELINES.

Travel time
The time necessary for waves to travel a given distance from the GENERATING AREA.

Trench
A long narrow submarine DEPRESSION with relatively steep sides.

Trough
A long and broad submarine DEPRESSION with gently sloping sides.

Trough, wave
See WAVE TROUGH.

Truncated landform
A landform cut off, especially by EROSION, and forming a steep side or CLIFF.

Tsunami
A large, high-velocity wave generated by displacement of the sea floor (such as sudden faulting, landsliding, or volcanic activity); also called seismic sea wave. Commonly misnamed TIDAL WAVE. See Figure 10.

Turbidity
(1) 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.

Turbidity current
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.

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

Unconformity
A surface that represents a break in the geologic record, with the rock unit immediately above it being considerably younger than the rock beneath. There are three major aspects to consider (1) Time. An unconformity develops during a period of time in which no sediment is deposited. This concept equates deposition and time, and an unconformity represents unrecorded time. (2) Deposition. Any interruption of deposition, whether large or small in extent, is an unconformity. This aspect of unconform…

Unconsolidated
In referring to sediment grains, loose, separate, or unattached to one another.

Undercutting
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.

Undertow
(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 undertow are actually RIP CURRENTS.

Underwater gradient
The slope of the sea bottom. See SLOPE.

Undisturbed water level
Same as STILL WATER LEVEL.

Updrift
The direction to which the predominant longshore movement of beach material approaches.

Upland
(SMP) Generally described as the dry land area above and landward of the ORDINARY HIGH WATER MARK (OHWM).

Uprush
The rush of water up the FORESHORE following the breaking of a wave, also called SWASH or RUNUP.

Upwelling
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. See Figure5.

Valley
An elongated DEPRESSION, usually with an outlet, between BLUFFS or between ranges of hills or mountains.

Variability of waves
(1) The variation of heights and periods between individual waves within a wave train. (2) The variation in direction of propagation of waves leaving the GENERATING AREA. (3) The variation in height along the crest, usually called 'variation along the wave'.

Velocity profile
The velocity gradient within the BOTTOM BOUNDARY LAYER, displayed as a graph of height above the BED against the velocity of the flow. See Figure 14.