A
ABRASION
The mechanical wearing away by rock material transported
by wind or water
ABRASION PLATFORM
A rock or clay platform which has been worn by the processes
of abrasion.
ACCELEROMETER
A device used in wave buoys for measuring acceleration.
ACCRETION
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.
ACTIVE MARGIN
A margin of a continental plate consisting of a continental
shelf and slope, and an oceanic trench or basin.
ADJUSTABLE GROIN
A GROIN whose permeability can be changed, usually with
gates or removable sections.
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.
AEOLIAN
See EOLIAN.
AGE, WAVE
The ratio of wave velocity to wind velocity (in wave forecasting
theory).
AGGRADATION
See ACCRETION.
ALIGNMENT
The course along which the center line of a channel, canal
or drain is located.
ALLOCHTONOUS
A term applied to shelves that presently experience deposition
of river-derived sediments. See also DETRITUS.
ALLUVIAL DEPOSITS
Detrital material which is transported by a river and
deposited B usually temporarily B at points along the
flood plain of a river. Commonly composed of sands and
gravels.
ALLUVIAL PLANE
A plain bordering a river, formed by the deposition of
material eroded from areas of higher elevation.
ALLUVIUM
Soil (sand, mud, or similar detrital material) deposited
by streams, or the deposits formed.
ALONGSHORE
Parallel to and near the shoreline; LONGSHORE.
ALTIMETER
An instrument that determines its distance above a particular
surface.
ALTIMETER, LASER
An instrument that determines altitude by measuring the
length of time needed for a pulse of coherent light to
travel from the instrument to the surface and back, and
multiplies half this time by the speed of light to get
the straight-line distance to the surface.
ALTIMETER, LIDAR
See ALTIMETER, LASER.
AMPLITUDE, WAVE
(1) The magnitude of the displacement of a wave from a
mean value. An ocean wave has an amplitude equal to the
vertical distance from still-water level to wave crest.
For a sinusoidal wave, the amplitude is one-half the wave
height. (2) The semirange of a constituent tide.
ANCHOR ICE
Spongy underwater ice formed on a submerged object or
attached to the bottom of a shallow body of water which
is itself not frozen; syn. bottom ice
ANGLE OF REPOSE
The maximum slope (measured from the horizontal) at which
soils and loose materials on the banks of canals, rivers
or embankments will stay stable.
ANISOTROPIC
Having properties that change with changing directions.
ANOXIC
Refers to an environment that contain little or no dissolved
oxygen and hence little or no benthic marine life. These
conditions arise in some basins or fjords where physical
circulation of seawater is limited.
ANTIDUNES
BED FORMS that occur in trains and are in phase with,
and strongly interact with, gravity water-surface waves.
ANTINODE
See LOOP.
APRON
Layer of stone, concrete or other material to protect
the toe of a structure.
AQUIFER
A geologic formation that is water-bearing, and which
transmits water from one point in the formation to another.
ARCHIPELAGO
A sea that contains numerous islands; also the island
group itself.
ARMOR LAYER
Protective layer on a BREAKWATER or SEAWALL composed of
armor units.
ARMOR UNIT
A relatively large quarrystone or concrete shape that
is selected to fit specified geometric characteristics
and density. It is usually of nearly uniform size and
usually large enough to require individual placement.
In normal cases it is used as primary wave protection
and is placed in thicknesses of at least two units.
ARTIFICIAL NOURISHMENT
The process of replenishing a beach with material (usually
sand) obtained from another location.
ASPERITIES
The three-dimensional irregularities forming the surface
of an irregular stone (or rock) subject to wear and rounding
during abrasion.
ASTRONOMICAL TIDE
The tidal levels and character which would result from
gravitational effects, e.g. of the Earth, Sun and Moon,
without any atmospheric influences.
ATOLL
A ring-shaped coral REEF, often carrying low sand islands,
enclosing a shallow LAGOON. The reef is surrounded by
deep water of the open sea.
ATTENUATION
(1) A lessening of the amplitude of a wave with distance
from the origin. (2) The decrease of water-particle motion
with increasing depth. Particle motion resulting from
surface oscillatory waves attenuates rapidly with depth,
and practically disappears at a depth equal to a surface
wavelength.
AUTOCHTHONOUS
A term applied to shelves on which older shelf sediments
are primarily being reworked by modern shelf processes.
AUTOMATIC TIDE GAGE
An instrument that automatically registers the rise and
fall of the tide. In some instruments, the registration
is accomplished by printing the heights at regular intervals,
in others by a continuous graph in which the height of
the tide is represented by the ordinates of the curve
and the corresponding time by the abscissae.
AVULSION
(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.
AWASH
Situated so that the top is intermittently washed by waves
or tidal action. Condition of being exposed or just bare
at any stage of the tide between high water and chart
datum.
B
BACK BARRIER
Pertaining to the lagoon-marsh-tidal creek complex in
the lee of a coastal barrier island, barrier spit, or
baymouth barrier.
BACKBEACH
See BACKSHORE.
BACKRUSH
The seaward return of the water following the uprush of
the waves. For any given tide stage the point of farthest
return seaward of the backrush is known as the Limit of
backrush or limit backwash.
BACKSHORE
That zone of the shore or beach lying between the foreshore
and the coastline comprising the BERM or BERMS and acted
upon by waves only during severe storms, especially when
combined with exceptionally high water. Also BACKBEACH.
(See Figure IV-1-2.)
BACKWASH
(1) See BACKRUSH. (2) Water or waves thrown back by an
obstruction such as a ship, BREAKWATER, or cliff.
BACKWASH RIPPLES
Low amplitude ripple marks formed on fine sand beaches
by the Backwash of the waves.
BACKWATER CURVE
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
BANK
(1) The rising ground bordering a lake, river, or sea;
or of a river or channel, for which it is designated as
right or left as the observer is facing downstream. (2)
An elevation of the sea floor or large area, located on
a continental (or island) shelf and over which the depth
is relatively shallow but sufficient for safe surface
navigation (e.g., Georges Bank); a group of shoals. (3)
In its secondary sense, used only with a qualifying word
such as "sandbank" or "gravelbank,"
a shallow area consisting of shifting forms of silt, sand,
mud, and gravel.
BAR
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.
BARRIER BEACH
A bar essentially parallel to the shore, the crest of
which is above normal high water level. Also called offshore
barrier and BARRIER ISLAND.
BARRIER FLAT
The flat area, often marshy and populated with low vegetation,
on the bay or lagoon side of a barrier island
BARRIER ISLAND
A detached portion of a barrier beach between two inlets.
It commonly had DUNES, vegetated areas, and swampy terranes
(see BARRIER FLAT) extending from the beach into the lagoon.
Example: Outer Banks, North Carolina.
BARRIER LAGOON
A bay roughly parallel to the coast and separated from
the open ocean by barrier islands. Also, the body of water
encircled by coral islands and REEFS, in which case it
may be called an ATOLL lagoon.
BARRIER REEF
A coral REEF parallel to and separated from the coast
by a lagoon that is too deep for coral growth. Generally,
barrier reefs follow the coasts for long distances and
are cut through at irregular intervals by channels or
passes. Example: Great Barrier Reef, Queensland, Australia.
BARRIER SPIT
Similar to a barrier island, but connected to the mainland.
BASIN
A depressed area with no surface outlet, such as a lake
basin or an enclosed sea.
BASIN, BOAT
A naturally or artificially enclosed or nearly enclosed
harbor area for small craft.
BASTION
A massive groin, or projecting section of seawall normally
constructed with its crest above water level.
BATHMETRIC CHART
A topographic map of the bed of the ocean, with depths
indicated by contours (isobaths) drawn at regular intervals.
BATHYMETRY
The measurement of depths of water in oceans, seas, and
lakes; also information derived from such measurements.
BAY
A recess in the shore or an inlet of a sea between two
capes or headlands, not so large as a gulf but larger
than a cove. See also BIGHT, EMBAYMENT.
BAYMOUTH BAR
A bar extending partly or entirely across the mouth of
a bay .
BAYOU
A minor sluggish waterway or estuarial creek, tributary
to, or connecting, other streams or bodies of water, whose
course is usually through lowlands or swamps. Sometimes
called SLOUGH. Term is commonly used in the southern United
States.
BEACH
The zone of unconsolidated material that extends landward
from the low water line to the place where there is marked
change in material or physiographic form, or to the
line of permanent vegetation (usually the effective limit
of storm waves). The seaward limit of a beach--unless
otherwise specified--is the mean low water line.
A beach includes foreshore and backshore. (See Figure
IV-1-2.) See also SHORE, SUSTAINABLE BEACH, AND SELF-SUSTAINING
BEACH.
BEACH ACCRETION
See ACCRETION.
BEACH BERM
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.)
BEACH CREST
The point representing the limit of normal high tide wave
run-up (see BERM CREST)
BEACH CUSP
See CUSP.
BEACH EROSION
The carrying away of beach materials by wave action, tidal
currents, littoral currents, or wind.
BEACH FACE
The section of the beach normally exposed to the action
of the wave uprush. The FORESHORE of a BEACH. (Not synonymous
with SHOREFACE.)
BEACH FILL
Material placed on a beach to renourish eroding shores.
BEACH HEAD
The cliff, dune or sea wall looming above the land ward
limit of the active beach
BEACH MATERIAL
Granular sediments, usually sand or shingle moved by the
sea.
BEACH PLAN SHAPE
The shape of the beach in plan; usually shown as a contour
line, combination of contour lines or recognizable features
such as beach crest and/or the still water line
BEACH PROFILE
A cross-section taken perpendicular to a given beach contour;
the profile may include the face of a dune or sea wall,
extend over the backshore, across the foreshore, and seaward
underwater into the nearshore zone.
BEACH RIDGE
See RIDGE, BEACH.
BEACH SCARP
See SCARP, BEACH.
BEACH WIDTH
The horizontal dimension of the beach measured normal
to the shoreline and landward of the higher-high tide
line (on oceanic coasts) or from the still water level
(on lake coasts)
BEAUFORT SCALE
Table A-1
Beaufort Wind Scale
Beaufort Number Wind Speed (knots) WMO Description 1
0 < 1 Calm
1 1 - 3 Light air
2 4 - 6 Light breeze
3 7 - 10 Gentle breeze
4 11 - 16 Moderate breeze
5 17 - 21 Fresh breeze
6 22 - 27 Strong breeze
7 28 - 33 Near gale
8 34 - 40 Gale
9 41 - 47 Strong Gale
10 48 - 55 Storm
11 56 - 63 Violent storm
12 $ 64 Hurricane
1 World Meteorological Organization, from http://www.crh.noaa.gov/lot/webpage/beaufort/
(28 Aug. 2001)
Classification of the force of the winds in accordance
with a scale established by Rear-Admiral, Sir Francis
Beaufort in which the range of intensity varies from 0
to 12, of integers (0 to 12) with a description of the
state and behavior of a "well-conditioned man-of-war."
BED
The bottom of a watercourse, or any body of water.
BED FORMS
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.
BED LOAD
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.
BED PROTECTION
A (rock) structure on the bed in order to protect the
underlying bed against erosion due to current and/or wave
action.
BED SHEAR STRESS
The way in which waves (or currents) transfer energy to
the sea bed.
BEDDING PLANE
A surface parallel to the surface of deposition, which
may or may not have a physical expression. The original
attitude of a bedding plane should not be assumed to have
been horizontal.
BEDROCK
The solid rock that underlies gravel, soil, and other
superficial material. Bedrock may be exposed at the surface
(an outcrop) or it may br buried under a few centimeters
to thousands of meters of unconsolidated material.
BENCH
(1) A level or gently sloping erosion plane inclined seaward.
(2) A nearly horizontal area at about the level of maximum
high water on the sea side of a dike.
BENCH MARK, TIDAL
A bench mark whose elevation has been determined with
respect to mean sea level at a nearby tide gauge; the
tidal bench mark is used as reference for that tide gauge.
BENCH MARK
A permanently fixed point of known elevation. A primary
bench mark is one close to a tide station to which the
tide staff and tidal datum originally are referenced.
BENEFITS
The asset value of a scheme, usually measured in terms
of the cost of damages avoided by the scheme, or the valuation
of perceived amenity or environmental improvements
BENTHIC
Pertaining to the sub-aquatic bottom.
BENTHOS
Those animals who live on the sediments of the sea floor,
including both mobile and non-mobile forms.
BERM
(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.
BERM, BEACH
See BEACH BERM.
BERM BREAKWATER
Rubble mound structure with horizontal berm of armor stones
at about sea level, which is allowed to be (re)shaped
by the waves.
BERM CREST
The seaward limit of a BERM. Also called BERM EDGE. (See
Figure IV-1-2.)
BIFURCATION
Location where a river separates in two or more reaches
or branches (the opposite of a confluence).
BIGHT
A bend in a coastline forming an open bay. A bay formed
by such a bend.
BIOTURBATION
The disturbance of sediment bedding by the activities
of burrowing organisms.
BIRDFOOT DELTA
A river delta formed by many levee-bordered distributaries
extending seaward and resembling in plan the outstretched
claws of a bird. Example: Mississippi River delta.
BLANKET (FOUNDATION or BEDDING)
A layer or layers of graded fine stones underlying a BREAKWATER,
GROIN or rock embankment to prevent the natural bed material
from being washed away.
BLOWN SANDS See EOLIAN SANDS.
BLOWOUT
A depression on the land surface caused by wind erosion.
BLUFF
A high, steep bank or cliff.
BOG
A wet, spongy, poorly drained area which is usually rich
in very specialized plants, contains a high percentage
of organic remnants and residues and frequently is associated
with a spring, seepage area, or other subsurface water
source. A bog sometimes represents the final stage of
the natural processes of eutrophication by which lakes
and other bodies of water are very slowly transformed
into land areas.
BOIL
An upward flow of water in a sandy formation due to an
unbalanced hydrostatic pressure resulting from a rise
in a nearby stream, or from removing the overburden in
making excavations.
BOLD COAST
A prominent landmass that rises steeply from the sea.
BORE
A very rapid rise of the tide in which the advancing water
presents an abrupt front of considerable height. In shallow
estuaries where the range of tide is large, the high water
is propagated inward faster than the low water because
of the greater depth at high water. If the high water
overtakes the low water, an abrupt front is presented,
with the high-water crest finally falling forward as the
tide continues to advance. Also EAGER.
BOTTOM (nature of)
The composition or character of the bed of an ocean or
other body of water (e.g., clay, coral, gravel, mud, ooze,
pebbles, rock, shell, shingle, hard, or soft). (See Figure
IV-1-2.)
BOTTOM BOUNDARY LAYER
The lower portion of the water flow that experiences frictional
retardation based on its proximity to the bed.
BOTTOMSET
One of the horizontal or gently inclined sediment layers
deposited in front of the advancing forest beds of a delta.
BOULDER
A rounded rock more than 256 mm (10 inch) in diameter;
larger than a cobblestone. See SOIL CLASSIFICATION.
BOUNDARY CONDITIONS
Environmental conditions, e.g. waves, currents, drifts,
etc. used as boundary input to physical or numerical models
BOX GAGE
A tide gage that is operated by a float in a long vertical
box to which the tide is admitted through an opening in
the bottom. In the original type of box gage the float
supported a graduated rod which rose and fell with the
tide.
BRAIDED RIVER
A river type with multiple channels separated by shoals,
bars and islands
BREACHING
Failure of the beach head or a dike allowing flooding
by tidal action
BREAKER
A wave breaking on a shore, over a REEF, etc. Breakers
may be classified into four types (See Figure II-4-1):
COLLAPSING--breaking occurs over lower half of wave, with
minimal air pocket and usually no splash-up. Bubbles and
foam present. PLUNGING--crest curls over air pocket; breaking
is usually with a crash. Smooth splash-up usually follows.
SPILLING--bubbles and turbulent water spill down front
face of wave. The upper 25 percent of the front face may
become vertical before breaking. Breaking generally occurs
over quite a distance.
SURGING--wave peaks up, but bottom rushes forward from
under wave, and wave slides up beach face with little
or no bubble production. Water surface remains almost
plane except where ripples may be produced on the beachface
during runback.
BREAKER DEPTH
The still-water depth at the point where a wave breaks.
Also called BREAKING DEPTH.
BREAKER
Ratio of breaking wave height to deepwater wave height
BREAKER ZONE
The zone within which waves approaching the coastline
commence breaking, typically in water depths of between
5 and 10 meters
BREAKING
Reduction in wave energy and height in the surf zone due
to limited water depth
BREAKWATER
A structure protecting a shore area, harbor, anchorage,
or basin from waves.
BREASTWORK
Vertically-faced or steeply inclined structure usually
built with timber and parallel to the shoreline, at or
near the beach crest, to resist erosion or mitigate against
flooding.
BUFFER AREA
A parcel or strip of land that is designed and designated
to permanently remain vegetated in an undisturbed and
natural condition to protect an adjacent aquatic or wetland
site from upland impacts, to provide habitat for wildlife
and to afford limited public access.
BULKHEAD
A structure or partition to retain or prevent sliding
of the land. A secondary purpose is to protect the upland
against damage from wave action.
BULL NOSE
Substantial lip or protuberance at the top of the seaward
face of a wall, to deflect waves seaward.
BUOY
A float; especially a floating object moored to the bottom,
to mark a channel, anchor, shoal rock, etc. Some common
types include: a nun or nut buoy is conical in shape;
a can buoy is squat and cylindrical above water and conical
below water; a spar buoy is a vertical, slender spar anchored
at one end; a bell buoy, bearing a bell, runs mechanically
or by the action of waves, usually marks shoals or rocks;
a whistling buoy, similarly operated, marks shoals or
channel entrances; a dan buoy carries a pole with a flag
or light on it.
BUOYANCY
The resultant of upward forces, exerted by the water on
a submerged or floating body, equal to the weight of the
water displaced by this body.
BYPASSING, SAND
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.
C
CAISSON
Concrete box-type structure.
CALIFORNIA CURRENT
A deep-ocean boundary current that flows south-southeasterly
along the U.S. west coast. The current is shallow, broad
and slow moving carrying cold, nutrient poor waters toward
the equator.
CALCAREOUS
Containing calcium carbonate (CaCO3), chiefly as the minerals
calcite and aragonite. When applied to rock, it implies
that as much as 50 percent of the rock is carbonate (e.g.,
calcareous sand).
CALM
The condition of the water surface when there is no wind
waves or swell.
CANAL
An artificial watercourse cut through a land area for
such uses as navigation and irrigation.
CANYON
A relatively narrow, deep depression with steep slopes,
the bottom of which grades continuously downward. May
be underwater (submarine) or on land (SUBAERIAL).
CAPE
A land area jutting seaward from a continent or large
island which prominently marks a change in, or interrupts
notably, the coastal trend; a prominent feature. Examples:
Cape Cod, Massachusetts; Cape Hatteras, North Carolina.
CAPILLARY WAVE
A wave whose velocity of propagation is controlled primarily
by the surface tension of the liquid in which the wave
is traveling. Water waves of length less than about 1
inch are considered capillary waves. Waves longer than
1 inch and shorter than 2 inches are in an indeterminate
zone between capillary and gravity waves. See RIPPLE.
CARTOGRAPHY
The science and art of making maps.
CATCHMENT AREA
The area which drains naturally to a particular point
on a river, thus contributing to its natural discharge.
CAUSEWAY
A raised road across wet or marshy ground, or across water.
CAUSTIC
In refraction of waves, the name given to the curve to
which adjacent orthogonals of waves refracted by a bottom
whose contour lines are curved, are tangents. The occurrence
of a caustic always marks a region of crossed orthogonals
and high wave convergence.
CAY
See KEY.
CELERITY
Wave speed.
CENTRAL PRESSURE (CPI)
The estimated minimum barometric pressure in the eye (approximate
center) of a particular hurricane. The CPI is considered
the most stable to intensity of hurricane wind velocities
in the periphery of the storm; the highest wind speeds
are associated with storms having the lowest CPI.
CHANNEL (1) A natural or artificial waterway of perceptible
extent which either periodically or continuously contains
moving water, or which forms a connecting link between
two bodies of water. (2) The part of a body of water deep
enough to be used for navigation through an area otherwise
too shallow for navigation. (3) A large strait, as the
English Channel. (4) The deepest part of a stream, bay,
or strait through which the main volume or current of
water flows.
CHANNEL CAPACITY
The maximum flow which a channel is capable of transmitting
without its banks being overtopped.
CHANNEL-MOUTH BAR
A bar built where a stream enters a body of standing water,
resulting from decreased flow velocity.
CHARACTERISTIC WAVE HEIGHT
See SIGNIFICANT WAVE HEIGHT.
CHART
A special-purpose map, esp. one designed for navigation
such as a bathymetric chart.
CHART DATUM
The plane or level to which soundings (or elevations)
or tide heights are referenced (usually LOW WATER DATUM).
The surface is called a tidal datum when referred to a
certain phase of tide. To provide a safety factor for
navigation, some level lower than MEAN SEA LEVEL is generally
selected for hydrographic charts, such as MEAN LOW WATER
or MEAN LOWER LOW WATER. See DATUM PLANE.
CHEMICAL WEATHERING
Disintegration of rocks and sediments by chemical alteration
of the constituent minerals or of the cementing matrix.
It is caused by exposure, oxidation, temperature changes,
and biological processes.
CHENIER
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)
CHOP
The short-crested waves that may spring up quickly in
a moderate breeze, and which break easily at the crest.
Also WIND CHOP.
CHOPPY SEA
Short, rough waves tumbling with a short and quick motion.
Short-crested waves that may spring up quickly in a moderate
breeze, and break easily at the crest.
CLAPOTIS
The French equivalent for a type of STANDING WAVE. In
American usage it is usually associated with the standing
wave phenomenon caused by the reflection of a nonbreaking
wave train from a structure with a face that is vertical
or nearly vertical. Full clapotis is one with 100 percent
reflection of the incident wave; partial clapotis is one
with less than 100 percent reflection.
CLASTIC ROCKS
Rocks built up of fragments which have been produced by
weathering and erosion of pre-existing rocks and minerals
and, typically, transported mechanically to their point
of deposition.
CLAY
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.
CLIFF
A high, steep face of rock; a precipice. See also SEA
CLIFF.
CLIMATE
The characteristic weather of a region, particularly regarding
temperature and precipitation, averaged over some significant
internal of time (years).
CLOSURE DEPTH
The water depth beyond which repetitive profile surveys
(collected over several years) do not detect vertical
sea bed changes, generally considered the seaward limit
of littoral transport. The depth can be determined from
repeated cross-shore profile surveys or estimated using
formulas based on wave statistics. Note that this does
not imply the lack of sediment motion beyond this depth.
CNOIDAL WAVE
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.
CO-TIDAL LINES
Lines which link all the points where the tide is at the
same stage (or phase) of its cycle.
COAST
(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.
COASTAL AREA
The land and sea area bordering the shoreline. (See Figure
IV-1-2.)
COASTAL CURRENTS
(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.
COASTAL DEFENSE
General term used to encompass both coast protection against
erosion and sea defense against flooding.
COASTAL FORCING
The natural processes which drive coastal hydro- and morphodynamics
(e.g.winds, waves, tides, etc).
COASTAL PLAIN
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
COASTAL PROCESSES
Collective term covering the action of natural forces
on the shoreline, and near shore seabed
COASTAL STRIP
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.
COASTAL ZONE
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.
COASTAL ZONE MANAGEMENT
The integrated and general development of the coastal
zone. Coastal Zone Management is not restricted to coastal
defense works, but includes also a development in economical,
ecological and social terms. Coastline Management is a
part of Coastal Zone Management.
COASTLINE
(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.
COBBLE (COBBLESTONE)
A rock fragment between 64 and 256 mm in diameter, usually
rounded. See SOIL CLASSIFICATION.
COFFERDAM
A temporary watertight structure enclosing all or part
of the construction area so that construction can proceed
in the dry.
COHESIVE SEDIMENT
Sediment containing significant proportion of clays, the
electromagnetic properties of which cause the sediment
to bind together
COLLOID
As a size term refers to particles smaller than 0.00024
mm, smaller than clay size.
COMBER
(1) A deepwater wave whose crest is pushed forward by
a strong wind; much larger than a whitecap. (2) A long-period
breaker.
COMPETENCE
The ability of a wind or water current to transport detritus,
in terms of particle size rather than amount, measured
as the diameter of the largest particles.
COMPLEX SPIT
A large RECURVED SPIT with secondary spits developed at
its end. Example: Sandy Hook, New Jersey.
CONFLUENCE
The junction of two or more river reaches or branches
(the opposite of a bifurcation) .
CONSOLIDATION
The gradual, slow compression of a cohesive soil due to
weight acting on it, which occurs as water is driven out
of the voids in the soil. Consolidation only occurs in
clays or other soils of low permeability.
CONTINENTAL SHELF
(1) The zone bordering a continent extending from the
line of permanent immersion to the depth, usually about
100 m to 200 m, where there is a marked or rather steep
descent toward the great depths of the ocean. (2) The
area under active littoral processes during the HOLOCENE
period. (3) The region of the oceanic bottom that extends
outward from the shoreline with an average slope of less
than 1:100, to a line where the gradient begins to exceed
1:40 (the CONTINENTAL SLOPE).
CONTINENTAL SLOPE
The declivity from the offshore border of the CONTINENTAL
SHELF to oceanic depths. It is characterized by a marked
increase in slope.
CONTOUR
A line on a map or chart representing points of equal
elevation with relation to a DATUM. It is called an ISOBATH
when connecting points of equal depth below a datum. Also
called DEPTH CONTOUR.
CONTROLLING DEPTH
The least depth in the navigable parts of a waterway,
governing the maximum draft of vessels that can enter.
CONVERGENCE
(1) In refraction phenomena, the decreasing of the distance
between orthogonals in the direction of wave travel. Denotes
an area of increasing wave height and energy concentration.
(2) In wind-setup phenomena, the increase in setup observed
over that which would occur in an equivalent rectangular
basin of uniform depth, caused by changes in planform
or depth; also the decrease in basin width or depth causing
such increase in setup.
CORAL
(1) (Biology) Marine coelenterates (Madreporaria), solitary
or colonial, which form a hard external covering of calcium
compounds or other materials. The corals which form large
REEFS are limited to warm, shallow waters, while those
forming solitary, minute growths may be found in colder
waters to great depths. (2) (Geology) The concretion of
coral polyps, composed almost wholly of calcium carbonate,
forming reefs and tree-like and globular masses. May also
include calcareous algae and other organisms producing
calcareous secretions, such as bryozoans and hydrozoans.
CORAL REEF
A coral-algal mound or ridge of in-place coral colonies
and skeletal fragments, carbonate sand, and organically-secreted
calcium carbonate. A coral reef is built up around a wave-resistant
framework, usually of older coral colonies.
CORE
(1) A cylindrical sample extracted from a beach or seabed
to investigate the types and depths of sediment layers.
(2) An inner, often much less permeable portion of a BREAKWATER
or BARRIER BEACH
CORIOLIS EFFECT
Force due to the Earth's rotation, capable of generating
currents. It causes moving bodies to be deflected to the
right in the Northern Hemisphere and to the left in the
Southern Hemisphere. The "force" is proportional
to the speed and latitude of the moving object. It is
zero at the equator and maximum at the poles.
COSET
A group of units of CROSS-BEDDING which shows a uniform
direction of current flow.
COVE
A small, sheltered recess in a coast, often inside a larger
embayment.
COVER LAYER
The outer layer used in a rubble system as protection
against external hydraulic loads
CREEK
(1) A stream, less predominant than a river, and generally
tributary to a river. (2) A small tidal Channel through
a coastal MARSH.
CREEP
Very slow, continuous downslope movement of soil or debris.
CRENULATE
An indented or wavy shoreline beach form, with the regular
seaward- pointing parts rounded rather than sharp, as
in the cuspate type.
CREST
Highest point on a beach face, BREAKWATER, or sea wall.
CREST LENGTH, WAVE
The length of a wave along its crest. Sometimes called
CREST WIDTH.
CREST OF WAVE
(1) the highest part of a wave. (2) That part of the wave
above still-water level. (See Figure II-1-4.)
CREST OF BERM
The seaward limit of a berm. Also called BERM EDGE. (See
Figure IV-1-2.)
CREST WIDTH, WAVE
See CREST LENGTH, WAVE.
CROSS-BEDDING
An arrangement of relatively thin layers of rock inclined
at an angle to the more nearly horizontal BEDDING PLANES
of the larger rock unit. Also referred to as cross-stratification.
CROSS-SHORE Perpendicular to the shoreline.
CROWN WALL
Concrete superstructure on a rubble mound.
CURRENT
(1) The flowing of water, or other liquid or gas. (2)
That portion of a stream of water which is moving with
a velocity much greater than the average or in which the
progress of the water is principally concentrated. (3)
Ocean currents can be classified in a number of different
ways. Some important types include the following: (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.
CURRENT, COASTAL
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.
CURRENT, DRIFT
A broad, shallow, slow-moving ocean or lake current. Opposite
of CURRENT, STREAM.
CURRENT, EBB
The tidal current away from shore or down a tidal stream.
Usually associated with the decrease in the height of
the tide.
CURRENT, EDDY
See EDDY.
CURRENT, FEEDER
Any of the parts of the nearshore current system that
flow parallel to shore before converging and forming the
neck of the RIP CURRENT.
CURRENT, FLOOD
The tidal current toward shore or up a tidal stream. Usually
associated with the increase in the height of the tide.
CURRENT, INSHORE
See INSHORE CURRENT.
CURRENT, LITTORAL
Any current in the littoral zone caused primarily by wave
action; e.g., LONGSHORE CURRENT, RIP CURRENT. See also
CURRENT, NEARSHORE.
CURRENT, LONGSHORE
The littoral current in the breaker zone moving essentially
parallel to the shore, usually generated by waves breaking
at an angle to the shoreline.
CURRENT METER
An instrument for measuring the velocity of a current
CURRENT, NEARSHORE
A current in the NEARSHORE ZONE. (See Figure IV-1-2.)
CURRENT, OFFSHORE
See OFFSHORE CURRENT.
CURRENT, PERIODIC
See CURRENT, TIDAL.
CURRENT, PERMANENT
See PERMANENT CURRENT.
CURRENT, RIP
See RIP CURRENT.
CURRENT, STREAM
A narrow, deep, and swift ocean current, as the Gulf Stream.
CURRENT, DRIFT.
CURRENT SYSTEM, NEARSHORE
See NEARSHORE CURRENT SYSTEM.
CURRENT, TIDAL
The alternating horizontal movement of water associated
with the rise and fall of the tide caused by the astronomical
tide-producing forces. Also CURRENT, PERIODIC. See also
CURRENT, FLOOD and CURRENT, EBB.
CURRENT-REFRACTION
Process by which wave velocity, height, and direction
are affected by a current
CUSP
One of a series of short ridges on the FORESHORE separated
by crescent-shaped troughs spaced at more or less regular
intervals. Between these cusps are hollows. The cusps
are spaced at somewhat uniform distances along beaches.
They represent a combination of constructive and destructive
processes. Also BEACH CUSP. (See Figure III-2-23.)
CUSPATE BAR
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.
CUSPATE SPIT
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.
CYCLOIDAL WAVE
A steep, symmetrical wave whose crest forms an angle of
120 degrees and whose form is that of a cycloid. A trochoidal
wave of maximum steepness. See also TROCHOIDAL WAVE.
CYCLONE
A system of winds that rotates about a center of low atmospheric
pressure. Rotation is clockwise in the Southern Hemisphere
and anti-clockwise in the Northern Hemisphere. In the
Indian Ocean, the term refers to the powerful storms called
HURRICANES in the Atlantic.
D
DAM
Structure built in rivers or estuaries, basically to separate
water at both sides and/or to retain water at one side.
DATUM
Any permanent line, plane or surface used as a reference
datum to which elevations are referred.
DATUM, CHART
See CHART DATUM.
DATUM, PLANE
The horizontal plane to which soundings, ground elevations,
or water surface elevations are referred. Also REFERENCE
PLANE. The plane is called a TIDAL DATUM when defined
by a certain phase of the tide. The following datums are
ordinarily used on hydrographic charts:
MEAN LOW WATER--Atlantic coast (U. S.), Argentina, Sweden,
and Norway.
MEAN LOWER LOW WATER--Pacific coast (U. S.).
MEAN LOW WATER SPRINGS--United Kingdom, Germany, Italy,
Brazil, and Chile.
LOW WATER DATUM--Great Lakes (U. S. and Canada).
LOWEST LOW WATER SPRINGS--Portugal.
LOW WATER INDIAN SPRINGS--India and Japan (See INDIAN
TIDE PLANE).
LOWEST LOW WATER--France, Spain, and Greece.
A common datum used on United States topographic maps
is MEAN SEA LEVEL. See also BENCH MARK.
DAVIDSON CURRENT
Deep-ocean boundary current off the west coast of the
U.S. which brings warmer, saltier, low oxygen, high phosphate
equatorial type water from low to high latitudes.
DEBRIS LINE
A line near the limit of storm wave uprush marking the
landward limit of debris deposits.
DECAY AREA
Area of relative CALM through which waves travel after
emerging from the generating area.
DECAY DISTANCE
The distance waves travel after leaving the generating
area (FETCH).
DECAY OF WAVES
The change waves undergo after they leave a generating
area (FETCH) and pass through a calm, or region of lighter
winds. In the process of decay, the significant wave height
decreases and the significant wavelength increases.
DEEP WATER
Water so deep that surface waves are little affected by
the ocean bottom. Generally, water deeper than one-half
the surface wavelength is considered deep water. Compare
SHALLOW WATER.
DEEP WATER WAVES
A wave in water the depth of which is greater than one-half
the WAVE LENGTH.
DEFLATION
The removal of loose material from a beach or other land
surface by wind action.
DEGRADATION
The geologic process by means of which various parts of
the surface of the earth are worn away and their general
level lowered, by the action of wind and water.
DELTA
(1) An ALLUVIAL DEPOSIT, usually triangular 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.
DELTA PLAIN
The nearly-level surface composing the landward portion
of a large DELTA.
DENSITY
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.
DENSITY CURRENT
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.
DENSITY STRATIFICATION
The lateral expansion of a sediment plume as it moves
out of the distributary mouth, where salt and fresh water
mix. This is most likely to occur where the speed of the
river flow is moderate to low and the distributary mouth
is relatively deep.
DENSITY-DRIVEN CIRCULATION
Variations in salinity create variations in density in
estuaries. These variations in density create horizontal
pressure gradients, which drive estuarine circulation.
DEPRESSION
A general term signifying any depressed or lower area
in the ocean floor.
DEPTH
The vertical distance from a specified datum to the sea
floor.
DEPTH CONTOUR
See CONTOUR., also isobath.
DEPTH, CONTROLLING
See CONTROLLING DEPTH.
DEPTH FACTOR
See SHOALING COEFFICIENT.
DEPTH OF BREAKING
The still-water depth at the point where the wave breaks.
Also BREAKER DEPTH.
DERRICK STONE
See STONE, DERRICK.
DESIGN HURRICANE
See HYPOTHETICAL HURRICANE.
DESIGN STORM
A hypothetical extreme storm whose waves coastal protection
structures will often be designed to withstand. The severity
of the storm (i.e. return period) is chosen in view of
the acceptable level of risk of damage or failure. A DESIGN
STORM consists of a DESIGN WAVE condition, a design water
level and a duration.
DESIGN WAVE
In the design of HARBORS, harbor works, etc., the type
or types of waves selected as having the characteristics
against which protection is desired.
DESIGN WAVE CONDITION
Usually an extreme wave condition with a specified return
period used in the design of coastal works.
DETACHED BREAKWATER
A BREAKWATER without any SUBAERIAL connection to the shore.
DETRITUS
Small fragments of rock which have been worn or broken
away from a mass by the action of water or waves.
DIFFERENTIAL EROSION / WEATHERING
These features develop in rocks which have varying resistance
to the agencies of erosion and/or weathering so that parts
of the rock are removed at greater rates than others.
A typical example is the removal of soft beds from between
harder beds in a series of sedimentary rocks. The term
may be applied to any size of feature, from small-scale
>etching= to the regional development of hills and
valleys controlled by hard and soft rocks.
DIFFRACTION (of water waves)
The phenomenon by which energy is transmitted laterally
along a wave crest. When a part of a train of waves is
interrupted by a barrier, such as a BREAKWATER, the
effect of diffraction is manifested by propagation of
waves into the sheltered region within the barrier's geometric
shadow. (See Figure II-7-2)
DIFFRACTION COEFFICIENT
Ratio of diffracted wave height to deep water wave height.
DIKE
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
DISCHARGE
The volume of water per unit of time flowing along a pipe
or channel.
DITCH
A channel to convey water for irrigation or drainage.
DIURNAL
Having a period or cycle of approximately one TIDAL DAY.
DIURNAL CURRENT
The type of tidal current having only one flood and one
ebb period in the tidal day. A ROTARY CURRENT is diurnal
if it changes its direction through all points of the
compass once each tidal day.
DIURNAL INEQUALITY
The difference in height of the two high waters or of
the two low waters of each day. Also, the difference in
velocity between the two daily flood or EBB CURRENTS of
each day.
DIURNAL TIDE
A tide with one high water and one low water in a tidal
day. (See Figure II-5-16)
DIVERGENCE
(1) In refraction phenomena, the increasing of distance
between orthogonals in the direction of wave travel. Denotes
an area of decreasing wave height and energy concentration.
(2) In wind-setup phenomena, the decrease in setup observed
under that which would occur in an equivalent rectangular
basin of uniform depth, caused by changes in planform
or depth. Also the increase in basin width or depth causing
such decrease in setup.
DIVERGING WAVE
Waves that move obliquely out from a vessel=s sailing
line. (See Figure II-7-40)
DIVERSION CHANNEL
A waterway used to divert water from its natural course.
The term is generally applied to a temporary arrangement
e.g. to by-pass water around a dam site during construction.
DOCK
The slip or waterway between two piers, or cut into the
land, for the reception of ships.
DOLPHIN
A cluster of piles.
DOWNDRIFT
The direction of predominant movement of littoral materials.
DOWNSTREAM
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.
DOWNWELLING
A downward movement (sinking) of surface water caused
by onshore Ekman transport, converging CURRENTS, or when
a water mass becomes more dense than the surrounding water.
DRAINAGE BASIN
Total area drained by a stream and its tributaries.
DREDGING
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.
DRIFT CURRENT
A broad, shallow, slow-moving ocean or lake current.
DRIFT SECTOR
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.
DROMOND
A large medieval fast-sailing galley or cutter.
DROWNED COAST
A shore with long, narrow channels, implying that subsidence
of the coast has transformed the lower portions of river
valleys into tidal estuaries.
DRUMLIN
A low, smoothly-rounded, elongate hill of compact glacial
till built under the margin of the ice and shaped by its
flow.
DRYING BEACH
That part of the beach which is uncovered by water (e.g.
at low tide). Sometimes referred to as 'SUBAERIAL' beach.
DUNES
(1) Ridges or mounds of loose, wind-blown material, usually
sand. (See Figure IV-2-11.) (2) Bed forms smaller than
bars but larger than ripples that are out of phase with
any water-surface gravity waves associated with them.
DURABILITY
The ability of a rock to retain its physical and mechanical
properties (i.e. resist degradation) in engineering service.
DURATION
In wave forecasting, the length of time the wind blows
in nearly the same direction over the FETCH (generating
area).
DURATION, MINIMUM
The time necessary for steady-state wave conditions to
develop for a given wind velocity over a given fetch length.
DURATION OF EBB
The interval of time in which a tidal current is ebbing,
determined from the middle of the slack waters.
DURATION OF FALL
The interval from high water to low water.
DURATION OF FLOOD
The interval of time in which a tidal current is flooding,
determined from the middle of slack waters.
DURATION OF RISE
The interval from low water to high water.
DYNAMIC EQUILIBRIUM
Short term morphological changes that do not affect the
morphology over a long period.
DYNAMIC VISCOSITY
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.
E
EAGER
See BORE.
EBB
Period when tide level is falling; often taken to mean
the ebb current which occurs during this period.
EBB CURRENT
The movement of a tidal current away from shore or down
a tidal stream. In the semidiurnal type of reversing current,
the terms greater ebb and lesser ebb are applied respectively
to the ebb currents of greater and lesser velocity of
each day. The terms of maximum ebb and minimum ebb are
applied to the maximum and minimum velocities of a continuously
running ebb current, the velocity alternately increasing
and decreasing without coming to a slack or reversing.
The expression maximum ebb is also applicable to any ebb
current at the time of greatest velocity.
EBB INTERVAL
The interval between the transit of the moon over the
meridian of a place and the time of the following strength
of ebb.
EBB SHIELD
High, landward margin of a flood-tidal shoal that helps
divert ebb-tide currents around the shoal.
EBB STRENGTH
The EBB CURRENT at the time of maximum velocity.
EBB TIDAL DELTA
The bulge of sand formed at the seaward mouth of TIDAL
INLETS as a result of interaction between tidal currents
and waves. Also called inlet-associated bars and estuary
entrance shoals.
EBB TIDE
The period of tide between high water and the succeeding
low water; a falling tide. (See Figure II-5-16.)
ECHO SOUNDER
An electronic instrument used to determine the depth of
water by measuring the time interval between the emission
of a sonic or ultrasonic signal and the return of its
echo from the bottom.
ECOSYSTEM
The living organisms and the nonliving environment interacting
in a given area, encompassing the relationships between
biological, geochemical, and geophysical systems.
EDDY
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.
EDDY CURRENT
See EDDY.
EDGE WAVE
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.
EKMAN TRANSPORT
Resultant flow at right angles to and to the right of
the wind direction (in the northern hemisphere) referred
to as UPWELLING and DOWNWELLING.
ELEVATION
The vertical distance from mean sea level or other established
datum plane to a point on the earth=s surface; height
above sea level. Although sea floor elevation below msl
should be marked as a negative value, many charts show
positive numerals for water depth.
EL NIÑO
Warm equatorial water which flows southward along the
coast of Peru and Ecuador during February and March of
certain years. It is caused by poleward motions of air
and unusual water temperature patterns in the Pacific
Ocean, which cause coastal downwelling, leading to the
reversal in the normal north-flowing cold coastal currents.
During many El Niño years, storms, rainfall, and
other meteorological phenomena in the Western Hemisphere
are measurably different than during non-El Niño
years.
ELUTRIATION
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.
EMBANKMENT
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.
EMBAYMENT
An indentation in the shoreline forming an open bay.
EMERGENT COAST
A coast in which land formerly under water has recently
been exposed above sea level, either by uplift of the
land or by a drop in sea level.
ENDEMIC
Native or confined to a specific geographic area.
ENERGY COEFFICIENT
The ratio of the energy in a wave per unit crest length
transmitted forward with the wave at a point in shallow
water to the energy in a wave per unit crest length transmitted
forward with the wave in deep water. On refraction diagrams
this is equal to the ratio of the distance between a pair
of orthogonals at a selected shallow-water point to the
distance between the same pair of orthogonals in deep
water. Also the square of the REFRACTION COEFFICIENT.
ENTRANCE
The avenue of access or opening to a navigable channel
or inlet.
EOLIAN (also AEOLIAN)
Pertaining to the wind, esp. used with deposits such as
loess and dune sand, and sedimentary structures like wind-formed
ripple marks.
EOLIAN SANDS
Sediments of sand size or smaller which have been transported
by winds. They may be recognized in marine deposits off
desert coasts by the greater angularity of the grains
compared with waterborne particles.
EQUATORIAL CURRENTS
(1) Ocean currents flowing westerly near the equator.
There are two such currents in both the Atlantic and Pacific
Oceans. The one to the north of the equator is called
the North Equatorial Current and the one to the south
is called the South Equatorial Current. Between these
two currents there is an easterly flowing stream known
as the Equatorial Countercurrent. (2) Tidal currents occurring
semimonthly as a result of the moon being over the equator.
At these times the tendency of the moon to produce DIURNAL
INEQUALITY in the current is at a minimum.
EQUATORIAL TIDES
Tides occurring semimonthly as the result of the moon
being over the equator. At these times the tendency of
the moon to produce a DIURNAL INEQUALITY in the tide is
at a minimum.
EROSION
The wearing away of land by the action of natural forces.
On a beach, the carrying away of beach material by wave
action, tidal currents, littoral currents, or by deflation.
ESCARPMENT
A more or less continuous line of cliffs or steep slopes
facing in one general direction which are caused by erosion
or faulting. Also SCARP. (See Figure IV-1-2.)
ESTUARY
(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.
EUSTATIC SEA LEVEL CHANGE
Change in the relative volume of the world=s ocean basins
and the total amount of ocean water.
EYE
In meteorology, usually the "eye of the storm"
(hurricane): the roughly circular area of comparatively
light winds and fair weather found at the center of a
severe tropical cyclone.
F
FAIRWAY
The parts of a waterway that are open and unobstructed
for navigation. The main traveled part of a waterway;
a marine thoroughfare.
FAR-INFRAGRAVITY
The frequency band (nominally 0.001 - 0.02 Hz) occupied
by SHEAR INSTABILITIES of the longshore current. This
band falls both below and in the lower part of the Infragravity
band occupied by Infragravity waves.
FATHOM
A unit of measurement used for soundings equal to 1.83
meters (6 feet).
FATHOMETER
The copyrighted trademark for a type of ECHO SOUNDER.
FAULT
A fracture in rock along which there has been an observable
amount of displacement. Faults are rarely single planar
units; normally they occur as parallel to sub-parallel
sets of planes along which movement has taken place to
a greater or lesser extent. Such sets are called fault
or fracture-zones.
FAUNA
The entire group of animals found in an area.
FEEDER BEACH
An artificially widened beach serving to nourish downdrift
beaches by natural littoral currents or forces.
FEEDER CURRENT
The currents which flow parallel to shore before converging
and forming the neck of a RIP CURRENT.
FEEDER CURRENT
See CURRENT, FEEDER.
FEELING BOTTOM
The initial action of a deepwater wave, in response to
the bottom, upon running into shoal water.
FETCH
The area in which SEAS are generated by a wind having
a fairly constant direction and speed. Sometimes used
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