 |
Ads |
|
| |
|
Sponsored Links |
|
| |
|
Fluid Indication and Control |
|
|
|
| Coastal
Terminology |
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
synonymously with FETCH LENGTH. Also GENERATING AREA.
FETCH LENGTH
The horizontal distance (in the direction of the wind)
over which a wind generates seas or creates a WIND SETUP.
FETCH-LIMITED
Situation in which wave energy (or wave height) is limited
by the size of the wave generation area (fetch).
FILTER
Intermediate layer, preventing fine materials of an underlayer
from being washed through the voids of an upper layer.
FIORD (FJORD)
A narrow, deep, steep-walled inlet of the sea, usually
formed by entrance of the sea into a deep glacial trough.
FIRTH
A narrow arm of the sea; also, the opening of a river
into the sea.
FLOOD (1) Period when tide level is rising; often taken
to mean the flood current which occurs during this period
(2) A flow beyond the carrying capacity of a channel.
FLOOD CHANNEL
Channel located on ebb-tidal shoal that carries the flood
tide over the tidal flat into the back bay or lagoon.
FLOOD 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.
FLOOD GATE
A gravity outlet fitted with vertically-hinged doors,
opening if the inner water level is higher than the outer
water level, so that drainage takes place during low water.
FLOOD INTERVAL
The interval between the transit of the moon over the
meridian of a place and the time of the following flood.
FLOOD MARK
Proof of any kind on the shoreline, or on structures like
bridge abutments, used to determine the highest level
attained by the water surface during the flood (note:
the height of the flood mark usually includes the wave
run-up).
FLOOD PLAIN
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.
FLOOD RAMP
Seaward-dipping sand platform dominated by flood-tidal
currents, located on ebb-tidal shoal near the opening
to the inlet.
FLOOD ROUTING
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).
FLOOD TIDAL DELTA
The bulge of sand formed at the landward mouth of TIDAL
INLETS as a result of flow expansion.
FLOOD TIDE
The period of tide between low water and the succeeding
high water; a rising tide. (See Figure II-5-16.)
FLOOD WALL, SPLASH WALL
Wall, retired from the seaward edge of the seawall crest,
to prevent water from flowing onto the land behind.
FLORA
The entire group of plants found in an area.
FLUVIAL
Of or pertaining to rivers; produced by the action of
a river or stream (e.g., fluvial sediment).
FLUSHING TIME
The time required to replace all the water in an ESTUARY,
HARBOR, etc., by action of current and tide.
FOAM LINE (1) The front of a wave as it advances shoreward,
after it has broken. (2) Lines of foam such as those which
move around the head of a RIP.
FOLLOWING WIND
Generally, the same as a tailwind; in wave forecasting,
wind blowing in the direction of ocean-wave advance.
FOREDUNE
The front DUNE immediately behind the backshore.
FORERUNNER
Low, long-period ocean SWELL which commonly precedes the
main swell from a distant storm, especially a tropical
cyclone.
FORESHORE
The part of the shore, lying between the crest of the
seaward berm (or upper limit of wave wash at high tide)
and the ordinary low-water mark, that is ordinarily traversed
by the uprush and backrush of the waves as the tides rise
and fall. See BEACH FACE. (See Figure IV-1-2.)
FORE REEF
The seaward side of a REEF (usually coral); in places
a steep slope covered with reef talus.
FORWARD SPEED (hurricane)
Rate of movement (propagation) of the hurricane eye in
meters per second, knots, or miles per hour.
FREEBOARD
At a given time, the vertical distance between the water
level and the top of the structure. On a ship, the distance
from the waterline to main deck or gunwale.
FRINGING REEF
A coral REEF attached directly to an insular or continental
shore. There may be a shallow channel or lagoon between
the reef and the adjacent mainland.
FRONT OF THE FETCH
In wave forecasting, the end of the generating area toward
which the wind is blowing.
FROUDE NUMBER
The dimensionless ratio of the inertial force to the force
of gravity for a given fluid flow. It may be given as
Fr = V /Lg where V is a characteristic velocity, L is
a characteristic length, and g the acceleration of gravity
- or as the square root of this number.
FULLY-DEVELOPED SEA
The waves that form when wind blows for a sufficient period
of time across the open ocean. The waves of a fully developed
sea have the maximum height possible for a given wind
speed, FETCH and duration of wind.
G
GABION
(1) Steel wire-mesh basket to hold stones or crushed rock
to protect a bank or bottom from erosion. (2) Structures
composed of masses of rocks, rubble or masonry held tightly
together usually by wire mesh so as to form blocks or
walls. Sometimes used on heavy erosion areas to retard
wave action or as a foundation for BREAKWATERS or JETTIES.
GALE
A wind between a strong breeze and a storm. A continuous
wind blowing in degrees of moderate, fresh, strong, or
whole gale and varying in velocity from 28 to 47 nautical
miles per hour (see BEAUFORT SCALE).
GAUGE (GAGE)
Instrument for measuring the water level relative to a
datum.
GENERATING AREA
In wave forecasting, the continuous area of water surface
over which the wind blows in nearly a constant direction.
Sometimes used synonymously with FETCH LENGTH. Also FETCH.
GEOGRAPHICAL INFORMATION SYSTEM (GIS)
Database of information which is geographically referenced,
usually with an associated visualization system.
GEOMETRIC MEAN DIAMETER
The diameter equivalent of the arithmetic mean of the
logarithmic frequency distribution. In the analysis of
beach sands, it is taken as that grain diameter determined
graphically by the intersection of a straight line
through selected boundary sizes, (generally points on
the distribution curve where 16 and 84 percent of the
sample is coarser by weight) and a vertical line through
the median diameter of the sample.
GEOMETRIC SHADOW
In wave diffraction theory, the area outlined by drawing
straight lines paralleling the direction of wave approach
through the extremities of a protective structure. It
differs from the actual protected area to the extent that
the diffraction and refraction effects modify the wave
pattern.
GEOMORPHOLOGY
(1) That branch of physical geography which deals with
the form of the Earth, the general configuration of its
surface, the distribution of the land, water, etc. (2)
The investigation of the history of geologic changes through
the interpretation of topographic forms.
GEOPHYSICS
The study of the physical characteristics and properties
of the earth, usually employing quantitative physical
methods.
GEOTEXTILE
A synthetic fabric which may be woven or non-woven used
as a filter.
GLACIER
A large body of ice moving slowly down a slope of valley
or spreading outward on a land surface (e.g., Greenland,
Antarctica) and surviving from year to year.
GLACIO-ISOSTACY
The state of hydrostatic equilibrium of the earth=s crust
as influenced by the weight of glacier ice.
GLOBAL POSITIONING SYSTEM (GPS)
A navigational and positioning system developed by the
U.S. Department of Defense, by which the location of a
position on or above the Earth can be determined by a
special receiver at that point interpreting signals received
simultaneously from several of a constellation of special
satellites.
GORGE
(1) The deepest portion of an inlet, the THROAT. (2) A
narrow, deep valley with nearly vertical rock walls.
GRADED BEDDING
An arrangement of particle sizes within a single bed,
with coarse grains at the bottom of the bed and progressively
finer grains toward the top of the bed.
GRADIENT
(1) A measure of slope (soil- or water-surface) in meters
of rise or fall per meter of horizontal distance. (2)
More general, a change of a value per unit of distance,
e.g. the gradient in longshore transport causes erosion
or accretion. (3) With reference to winds or currents,
the rate of increase or decrease in speed, usually in
the vertical; or the curve that represents this rate.
GRADING
Distribution, with regard to size or weight, of individual
stones within a bulk volume; heavy, light and fine grading
are distinguished.
GRADUAL CLOSURE METHOD
Method in which the final closure gap in a dam is closed
gradually either by the vertical or horizontal closure
method; this in contradiction with a sudden closure.
GRANULAR FILTER
Band of granular material which is incorporated in an
embankment, dam, dike, or bottom protection and is graded
so as to allow seepage to flow across or down the filter
zone without causing the migration of the material adjacent
to the filter.
GRAVEL
Unconsolidated natural accumulation of rounded rock fragments
coarser than sand but finer than pebbles (2-4 mm diameter).
GRAVITY WAVE
A wave whose velocity of propagation is controlled primarily
by gravity. Water waves more than 5 cm long are considered
gravity waves. Waves longer than 2.5 cm and shorter than
5 cm are in an indeterminate zone between CAPILLARY and
GRAVITY WAVES. See RIPPLE.
GROIN (British, GROYNE)
Narrow, roughly shore-normal structure built to reduce
longshore currents, and/or to trap and retain littoral
material. Most groins are of timber or rock and extend
from a SEAWALL, or the backshore, well onto the foreshore
and rarely even further offshore. See T-GROIN, PERMEABLE
GROIN, IMPERMEABLE GROIN.
GROIN BAY
The beach compartment between two groins.
GROIN SYSTEM
A series of groins acting together to protect a section
of beach. Commonly called a GROIN field.
GULF
A relatively large portion of the ocean or sea extending
far into land; the largest of various forms of inlets
of the sea (e.g., Gulf of Mexico, Gulf of Aqaba).
GUT
A tidal stream connecting two larger waterways.
H
HALCOCLINE
A zone in which salinity changes rapidly.
HALF-TIDE LEVEL
A plane midway between MEAN HIGH WATER and MEAN LOW WATER,
also called MEAN TIDE LEVEL.
HARBOR (British, HARBOUR)
Any protected water area affording a place of safety for
vessels. See also PORT.
HARBOR OSCILLATION (HARBOR SURGING)
The nontidal vertical water movement in a harbor or bay.
Usually the vertical motions are low; but when oscillations
are excited by a tsunami or storm surge, they may be quite
large. Variable winds, air oscillations, or surf beat
also may cause oscillations. See SEICHE.
HARD DEFENSES
General term applied to impermeable coastal defense structures
of concrete, timber, steel, masonry, etc, which reflect
a high proportion of incident wave energy.
HEAD OF RIP
The part of a rip current that has widened out seaward
of the breakers. See also CURRENT, RIP; CURRENT, FEEDER;
and NECK (RIP).
HEADLAND (HEAD)
(1) A comparatively high promontory with either a CLIFF
or steep face extending out into a body of water, such
as a sea or lake. An unnamed HEAD is usually called a
headland. (2) The section of RIP CURRENT which has widened
out seaward of the BREAKERS, also called HEAD OF RIP.
(3) Seaward end of BREAKWATER or dam.
HEADWATER LEVEL
The level of water in the reservoir.
HEAVE
(1) The vertical rise or fall of the waves or the sea.
(2) The translational movement of a craft parallel to
its vertical axis. (3) The net transport of a floating
body resulting from wave action.
HIGH SEAS
This term, in municipal and international law, denotes
the continuous body of salt water in the world that is
navigable in its character and that lies outside territorial
waters and maritime belts of the various countries.
HIGH TIDE, HIGH WATER (HW)
The maximum elevation reached by each rising tide. See
TIDE. (See Figure II-5-16.)
HIGH WATER (HW)
Maximum height reached by a rising tide. The height may
be solely due to the periodic tidal forces or it may have
superimposed upon it the effects of prevailing meteorological
conditions. Nontechnically, also called the HIGH TIDE.
HIGH WATER LINE
In strictness, the intersection of the plane of mean high
water with the shore. The shoreline delineated on the
nautical charts of the National Ocean Service is an approximation
of the high water line. For specific occurrences, the
highest elevation on the shore reached during a storm
or rising tide, including meteorological effects.
HIGH WATER MARK
A reference mark on a structure or natural object, indicating
the maximum stage of tide or flood.
HIGH WATER OF ORDINARY SPRING TIDES (HWOST)
A tidal datum appearing in some British publications,
based on high water of ordinary spring tides.
HIGHER HIGH WATER (HHW)
The higher of the two high waters of any tidal day. The
single high water occurring daily during periods when
the tide is diurnal is considered to be a higher high
water. (See Figure II-5-16.)
HIGHER LOW WATER (HLW)
The higher of two low waters of any tidal day. (See Figure
II-5-16.)
HINDCASTING
In wave prediction, the retrospective forecasting of waves
using measured wind information.
HINTERLAND
The region lying inland from the coast. Also the inland
area served by a port.
HISTORIC EVENT ANALYSIS
Extreme analysis based on hindcasting typically ten events
over a period of 100 years.
HOLOCENE
An epoch of the QUATERNARY period, from the end of the
PLEISTOCENE, about 8,000 years ago, to the present time.
Syn: Recent.
HOMOPYCNAL FLOW
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.
HOOK
A spit or narrow cape of sand or gravel which turns landward
at the outer end; a RECURVED SPIT.
HORIZONTAL CLOSURE METHOD
Construction of a dam by dumping the materials from one
or both banks, thus constricting the channel progressively
laterally until the dam is closed. This method is also
known as end dumping and point tipping
HURRICANE
An intense tropical cyclone in which winds tend to spiral
inward toward a core of low pressure, with maximum surface
wind velocities that equal or exceed 33.5 m/sec (75 mph
or 65 knots) for several minutes or longer at some points.
TROPICAL STORM is the term applied if maximum winds are
less than 33.5 m/sec but greater than a whole gale (63
mph or 55 knots). Term is used in the Atlantic, Gulf of
Mexico, and eastern Pacific.
HURRICANE PATH or TRACK
Line of movement (propagation) of the eye through an area.
HURRICANE STAGE HYDROGRAPH
A continuous graph representing water level stages that
would be recorded in a gage well located at a specified
point of interest during the passage of a particular hurricane,
assuming that effects of relatively short-period waves
are eliminated from the record by damping features of
the gage well. Unless specifically excluded and separately
accounted for, hurricane surge hydrographs are assumed
to include effects of astronomical tides, barometric pressure
differences, and all other factors that influence water
level stages within a properly designed gage well located
at a specified point.
HURRICANE WIND PATTERN or ISOVEL PATTERN
An actual or graphical representation of near-surface
wind velocities covering the entire area of a hurricane
at a particular instant. Isovels are lines connecting
points of simultaneous equal wind velocities, usually
referenced 9 meters (30 feet) above the surface, in meters
per second, knots, or meters per hour; wind directions
at various points are indicated by arrows or deflection
angles on the isovel charts. Isovel charts are usually
prepared at each hour during a hurricane, but for each
half hour during critical periods.
HYDRAULIC RADIUS
Quotient of the wetted cross-sectional area and the wetted
perimeter.
HYDRAULICALLY EQUIVALENT GRAINS Sedimentary particles
that settle at the same rate under the same conditions.
HYDROGRAPHY
(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.
HYDROGRAPHIC PRESSURE
The pressure exerted by water at any given point in a
body of water at rest.
HYPOPYCNAL FLOW
Outflow from a river or coastal inlet in which a wedge
of less dense water flows over the denser sea water.
HYPOTHETICAL HURRICANE ("HYPOHURRICANE")
A representation of a hurricane, with specified characteristics,
that is assumed to occur in a particular study area, following
a specified path and timing sequence.
TRANSPOSED--A hypohurricane based on the storm transposition
principle, assumed to have wind patterns and other characteristics
basically comparable to a specified hurricane of
record, but transposed to follow a new path to serve as
a basis for computing a hurricane surge hydrograph that
would be expected at a selected point. Moderate adjustments
in timing or rate of forward movement may also be made,
if these are compatible with meteorological considerations
and study objectives.
HYPOHURRICANE BASED ON GENERALIZED PARAMETERS--Hypohurricane
estimates based on various logical combinations of hurricane
characteristics used in estimating hurricane surge magnitudes
corresponding to a range of probabilities and potentialities.
The STANDARD PROJECT HURRICANE is most commonly used for
this purpose, but estimates corresponding to more severe
or less severe assumptions are important in some project
investigations.
STANDARD PROJECT HURRICANE (SPH)--A hypothetical hurricane
intended to represent the most severe combination of hurricane
parameters that is reasonably characteristic of a specified
region, excluding extremely rare combinations. It is further
assumed that the SPH would approach a given project site
from such direction, and at such rate of movement, to
produce the highest HURRICANE SURGE HYDROGRAPH, considering
pertinent hydraulic characteristics of the area. Based
on this concept, and on extensive meteorological
studies and probability analyses, a tabulation of "Standard
Project Hurricane Characteristics" mutually agreed
upon by representatives of the U. S. Weather Service
and the Corps of Engineers, is available.
PROBABLE MAXIMUM HURRICANE--A hypohurricane that might
result from the most severe combination of hurricane parameters
that is considered reasonably possible in the region involved,
if the hurricane should approach the point under study
along a critical path and at optimum rate of movement.
This estimate is substantially more severe than the SPH
criteria.
DESIGN HURRICANE--A representation of a hurricane with
specified characteristics that would produce HURRICANE
SURGE HYDROGRAPHS and coincident wave effects at various
key locations along a proposed project alinement.
It governs the project design after economics and other
factors have been duly considered. The design hurricane
may be more or less severe than the SPH, depending on
economics, risk, and local considerations.
I
ICE AGE
A loosely-used synonym of glacial epoch, or time of extensive
glacial activity; specif. of the latest period of widespread
continental glaciers, the PLEISTOCENE Epoch.
ICE FRONT
The floating vertical cliff forming the seaward edge of
an ICE SHELF or other glacier that enters the sea.
ICE SHELF
A extensive sheet of ice which is attached to the land
along one side but most of which is afloat and bounded
on the seaward side by a steep cliff (ICE FRONT) rising
2 tp 50+ m above sea level. Common along polar coasts
(Antarctica, Greenland), and generally of great breadth
and sometimes extending tens or hundreds of km seaward
from the continental coastline.
IMPERMEABLE GROIN
A GROIN constructed such that sand cannot pass through
the structure (but sand may still move over or around
it).
INCIDENT WAVE
Wave moving landward.
INDIAN SPRING LOW WATER
The approximate level of the mean of lower low waters
at spring tides, used principally in the Indian Ocean
and along the east coast of Asia. Also INDIAN TIDE PLANE.
INDIAN TIDE PLANE
The datum of INDIAN SPRING LOW WATER.
INFRAGRAVITY WAVE
Long waves with periods of 30 seconds to several minutes.
INLET
(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.
INLET GORGE
Generally, the deepest region of an inlet channel.
INSHORE (ZONE)
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.)
INSHORE CURRENT
Any current in or landward of the breaker zone.
INSULAR SHELF
The zone surrounding an island extending from the low
water line to the depth (usually about 183 m; 100 fathoms)
where there is a marked or rather steep descent toward
the great depths.
INTERNAL WAVES
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.
INTERTIDAL
The zone between the high and low water tides.
IRREGULAR WAVES
Waves with random wave periods (and in practice, also
heights), which are typical for natural wind-induced waves.
IRROTATIONAL WAVE
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.
ISOBATH
A contour line connecting points of equal water depths
on a chart.
ISOPACHYTE
Line connecting points on the seabed with an equal depth
of sediment.
ISOVEL PATTERN
See HURRICANE WIND PATTERN.
ISTHMUS
A narrow strip of land, bordered on both sides by water,
that connects two larger bodies of land.
J
JET
To place (a pile, slab, or pipe) in the ground by means
of a jet of water acting at the lower end.
JETTY
(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.
JOINT PROBABILITY
The probability of two (or more) things occurring together.
JOINT PROBABILITY DENSITY
Function specifying the joint distribution of two (or
more) variables.
JOINT RETURN PERIOD
Average period of time between occurrences of a given
joint probability event.
JONSWAP SPECTRUM
Wave spectrum typical of growing deep water waves developed
from field experiments and measurements of waves and wave
spectra in the Joint North Sea Wave Peoject
K
KATABATIC WIND
Wind caused by cold air flowing down slopes due to gravitational
acceleration.
KEY
A cay, esp. one of the low, insular banks of sand, coral,
and limestone off the southern coast of Florida.
KINEMATIC VISCOSITY
The dynamic viscosity divided by the fluid density.
KINETIC ENERGY (OF WAVES)
In a progressive oscillatory wave, a summation of the
energy of motion of the particles within the wave.
KNOLL
A submerged elevation of rounded shape rising less than
1000 meters from the ocean floor and of limited extent
across the summit. Compare SEAMOUNT.
KNOT
The unit of speed used in navigation equal to 1 nautical
mile (6,076.115 ft or 1,852 m) per hour.
L
LAGGING OF TIDE
The periodic retardation in the time of occurrence of
high and low water due to changes in the relative positions
of the moon and sun.
LAGOON
A shallow body of water, like a pond or sound, partly
or completely separated from the sea by a barrier island
or REEF. Sometimes connected to the sea via an INLET.
(See Figure IV-1-6.)
LAMINAR FLOW
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.
LAND BREEZE
A light wind blowing from the land to the sea, caused
by unequal cooling of land and water masses.
LAND-SEA BREEZE
The combination of a land breeze and a sea breeze as a
diurnal phenomenon.
LANDLOCKED
Enclosed, or nearly enclosed, by land--thus protected
from the sea, as a bay or a harbor.
LANDMARK
A conspicuous object, natural or artificial, located near
or on land, which aids in fixing the position of an observer.
LEAD LINE
A line, wire, or cord used in sounding (to obtain water
depth). It is weighted at one end with a plummet (sounding
lead). Also SOUNDING LINE.
LEDGE
A rocky formation forming a ridge or REEF, especially
one underwater or near shore
LEE
(1) Shelter, or the part or side sheltered or turned away
from the wind or waves. (2) (Chiefly nautical) The quarter
or region toward which the wind blows.
LEEWARD
The direction toward which the wind is blowing; the direction
toward which waves are traveling.
LENGTH OF WAVE
The horizontal distance between similar points on two
successive waves measured perpendicularly to the crest.
LEVEE
(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.
LIGHT BREEZE
A wind with velocity from 4 to 6 KNOTS.
LIMIT OF BACKRUSH (LIMIT OF BACKWASH)
See BACKRUSH, BACKWASH.
LITTORAL
Of or pertaining to a shore, especially of the sea.
LITTORAL CELL
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.
LITTORAL CURRENT
See CURRENT, LITTORAL.
LITTORAL DEPOSITS
Deposits of littoral drift.
LITTORAL DRIFT, LITTORAL TRANSPORT
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.
LITTORAL TRANSPORT RATE
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.
LITTORAL ZONE
In beach terminology, an indefinite zone extending seaward
from the shoreline to just beyond the breaker zone.
LOAD
The quantity of sediment transported by a current. It
includes the suspended load of small particles and the
bedload of large particles that move along the bottom.
LONG WAVES
Waves with periods above about 30 seconds; can be generated
by wave groups breaking in the surf zone. See also INFRAGRAVITY
WAVES.
LONGSHORE
Parallel to and near the shoreline; ALONGSHORE.
LONGSHORE BAR
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.
LONGSHORE CURRENT
See CURRENT, LONGSHORE.
LONGSHORE DRIFT
Movement of (beach) sediments approximately parallel to
the coastline.
LONGSHORE TRANSPORT RATE
See LITTORAL TRANSPORT RATE.
LONGSHORE TROUGH
An elongate DEPRESSION or series of depressions extending
along the lower BEACH or in the offshore zone inside the
BREAKERS.
LOOP
That part of a STANDING WAVE where the vertical motion
is greatest and the horizontal velocities are least. Loops
(sometimes called ANTINODES) are associated with CLAPOTIS
and with SEICHE action resulting from wave reflections.
Compare NODE.
LOW TIDE (LOW WATER, LW)
The minimum elevation reached by each falling tide. See
TIDE. (See Figure II-5-16.)
LOW TIDE TERRACE
A flat zone of the beach near the low water level.
LOW WATER (LW)
The minimum height reached by each falling tide. Nontechnically,
also called LOW TIDE.
LOW WATER DATUM
An approximation to the plane of mean low water that has
been adopted as a standard reference plane. See also DATUM,
PLANE and CHART DATUM.
LOW WATER LINE
The line where the established LOW WATER DATUM intersects
the shore. The plane of reference that constitutes the
LOW WATER DATUM differs in different regions.
LOW WATER OF ORDINARY SPRING TIDES (LWOST)
A tidal datum appearing in some British publications,
based on low water of ordinary spring tides.
LOWER HIGH WATER (LHW)
The lower of the two high waters of any tidal day. (See
Figure II-5-16.)
LOWER LOW WATER DATUM
An approximation to the plane of MEAN LOWER LOW WATER
that has been adopted as a standard reference plane for
a limited area and is retained for an indefinite period
regardless of the fact that it may differ slightly from
a better determination of MEAN LOWER LOW WATER from a
subsequent series of observations.
LOWER LOW WATER (LLW)
The lower of the two low waters of any tidal day. The
single low water occurring daily during periods when the
tide is diurnal is considered to be a lower low water.
(See Figure II-5-16.)
LUNAR DAY
The time of rotation of the Earth with respect to the
moon, or the interval between two successive upper transits
of the moon over the meridian of a place. The mean lunar
day is approximately 24.84 solar hours in length, or 1.035
times as great as the mean solar day. Also called TIDAL
DAY.
LUNAR TIDE
The portion of the tide that can be attributed directly
to attraction to the moon.
M
MACH-STEM WAVE
Higher-than-normal wave generated when waves strike a
structure at an oblique angle.
MACRO-TIDAL
Tidal range greater than 4 m.
MANAGED RETREAT
The deliberate setting back (moving landward) of the existing
line of sea defense in order to obtain engineering or
environmental advantages - also referred to as managed
landward realignment. Sometimes refers to moving roads
and utilities landward in the face of shore retreat.
MANGROVE
A tropical tree with interlacing prop roots, confined
to low-lying brackish areas.
MARGIN, CONTINENTAL
A zone separating a continent from the deep-sea bottom.
MARGINAL PROBABILITY
The probability of a single variable in the context of
a joint probability analysis.
MARGINAL RETURN PERIOD
The return period of a single variable in the context
of a joint probability analysis.
MARIGRAM
A graphic record of the rise and fall of the tide. The
record is in the form of a curve in which time is represented
by abscissas and the height of the tide by ordinates.
MARKER, REFERENCE
A mark of permanent character close to a survey station,
to which it is related by an accurately measured distance
and azimuth (or bearing).
MARKER, SURVEY
An object placed at the site of a station to identify
the surveyed location of that station.
MARSH
(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.
MARSH, DIKED
A former salt marsh which has been protected by a DIKE.
MARSH, SALT
A marsh periodically flooded by salt water.
MASS TRANSPORT, SHOREWARD
The movement of water due to wave motion, which carries
water through the BREAKER ZONE in the direction of wave
propagation. Part of the NEARSHORE CURRENT SYSTEM.
MATTRESS
A blanket of brushwood or bamboo, poles, geotextile and
reed lashed together to protect a shoreline, embankment
or river/sea bed against erosion. Sometimes placed on
the sea bed during JETTY construction to prevent stone
from settling into soft bottom.
MEAN DEPTH
The average DEPTH of the water area between the still
water level and the SHOREFACE profile from the waterline
to any chosen distance seaward.
MEAN DIAMETER, GEOMETRIC
See GEOMETRIC MEAN DIAMETER.
MEAN HIGH WATER SPRINGS (MHWS)
The average height of the high water occurring at the
time of spring tides.
MEAN HIGH WATER (MHW)
The average height of the high waters over a 19-year period.
For shorter periods of observations, corrections are applied
to eliminate known variations and reduce the results to
the equivalent of a mean 19-year value. All high water
heights are included in the average where the type of
tide is either semidiurnal or mixed. Only the higher high
water heights are included in the average where the type
of tide is diurnal. So determined, mean high water in
the latter case is the same as mean higher high water.
MEAN HIGHER HIGH WATER (MHHW)
The average height of the higher high waters over a 19-year
period. For shorter periods of observation, corrections
are applied to eliminate known variations and reduce the
result to the equivalent of a mean 19-year value.
MEAN LOW WATER (MLW)
The average height of the low waters over a 19-year period.
For shorter periods of observations, corrections are applied
to eliminate known variations and reduce the results to
the equivalent of a mean 19-year value. All low water
heights are included in the average where the type of
tide is either semidiurnal or mixed. Only lower low water
heights are included in the average where the type of
tide is diurnal. So determined, mean low water in the
latter case is the same as mean lower low water.
MEAN LOW WATER SPRINGS
The average height of low waters occurring at the time
of the spring tides. It is usually derived by taking a
plane depressed below the half-tide level by an amount
equal to one-half the spring range of tide, necessary
corrections being applied to reduce the result to a mean
value. This plane is used to a considerable extent for
hydrographic work outside of the United States and is
the plane of reference for the Pacific approaches to the
Panama Canal. Frequently abbreviated to LOW WATER SPRINGS.
MEAN LOWER LOW WATER (MLLW)
The average height of the lower low waters over a 19-year
period. For shorter periods of observations, corrections
are applied to eliminate known variations and reduce the
results to the equivalent of a mean 19-year value. Frequently
abbreviated to LOWER LOW WATER.
MEAN RANGE OF TIDE
The difference in height between MEAN HIGH WATER and MEAN
LOW WATER.
MEAN RISE OF THE TIDE
The height of MEAN HIGH WATER above the plane of reference
or DATUM of chart.
MEAN SEA LEVEL
The average height of the surface of the sea for all stages
of the tide over a 19-year period, usually determined
from hourly height readings. Not necessarily equal to
MEAN TIDE LEVEL.
MEAN STEEPNESS
The ratio of the MEAN DEPTH to the horizontal distance
over which the MEAN DEPTH was determined.
MEAN TIDE LEVEL
A plane midway between MEAN HIGH WATER and MEAN LOW WATER.
Not necessarily equal to MEAN SEA LEVEL. Also HALF-TIDE
LEVEL.
MEAN WATER LEVEL
The mean surface level as determined by averaging the
heights of the water at equal intervals of time, usually
at hourly intervals.
MEAN WAVE HEIGHT
The mean of all individual waves in an observation interval
of approximately half an hour. In case of a Rayleigh-distribution
63% of the significant wave height.
MEANDERING
A single channel having a pattern of successive deviations
in alignment which results in a more or less sinusoidal
course.
MEDIAN DIAMETER
The diameter which marks the division of a given sand
sample into two equal parts by weight, one part containing
all grains larger than that diameter and the other part
containing all grains smaller.
MEGARIPPLE
See SAND WAVE.
MESO-TIDAL
Tidal range between 2 m and 4 m.
METEOROLOGICAL TIDES
Tidal constituents having their origin in the daily or
seasonal variation in weather conditions which may occur
with some degree of periodicity.
MICRO-TIDAL
Tidal range less than 2 m.
MID-EXTREME TIDE
A plane midway between the extreme high water and the
extreme LOW WATER occurring in any locality.
MIDDLE-GROUND SHOAL
A shoal formed by ebb and flood tides in the middle of
the channel of the LAGOON or estuary end of an inlet.
MINERAL
A naturally occurring, inorganic, crystalline solid that
has a definite chemical composition and possesses characteristic
physical properties.
MINIMUM DURATION
See DURATION, MINIMUM.
MINIMUM FETCH
The least distance in which steady-state wave conditions
will develop for a wind of given speed blowing a given
duration of time.
MIST
Water vapor suspended in the air in very small drops finer
than rain, larger than fog.
MIXED CURRENT
Type of tidal current characterized by a conspicious velocity
difference between the two floods or two ebbs usually
occurring each tidal day.
MIXED TIDE
A type of tide in which the presence of a diurnal wave
is conspicuous by a large inequality in either the high
or low water heights, with two high waters and two low
waters usually occurring each tidal day. In strictness,
all tides are mixed, but the name is usually applied without
definite limits to the tide intermediate to those predominantly
semidiurnal and those predominantly diurnal. (See Figure
II-5-16.)
MOLE
In coastal terminology, a massive land-connected, solid-fill
structure of earth (generally revetted), masonry, or large
stone, which may serve as a breakwater or pier.
MONOCHROMATIC WAVES
A series of waves generated in a laboratory, each of which
has the same length and period.
MONOLITHIC
Like a single stone or block. In coastal structures, the
type of construction in which the structure's component
parts are bound together to act as one.
MORAINE
An accumulation of earth, stones, etc., deposited by a
glacier, usually in the form of a mound, ridge or other
prominence on the terrain.
MORPHODYNAMICS
(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.
MORPHOLOGICALLY AVERAGED
Single wave condition producing the same net longshore
drift as a given proportion of the annual wave climate.
MORPHOLOGY
River/estuary/lake/seabed form and its change with time.
MUD
A fluid-to-plastic mixture of finely divided particles
of solid material and water.
MUD FLAT
A level area of fine silt and clay along a shore alternately
covered or uncovered by the tide or covered by shallow
water.
N
NATIONAL TIDAL DATUM EPOCH (NTDE)
A period of 19 years adopted by the National Ocean Service
as the period over which observations of tides are to
be taken and reduced to average values for tidal datums.
NATURAL TRACER
A component of a sediment deposit that is unique to a
particular source and can be used to identify the source
and transport routes to a place of deposition.
NAUTICAL MILE
The length of a minute of arc, 1/21,600 of an average
great circle of the Earth. Generally one minute of latitude
is considered equal to one nautical mile. The accepted
United States value as of 1 July 1959 is 1,852 meters
(6,076.115 feet), approximately 1.15 times as long as
the U.S. statute mile of 5,280 feet. Also geographical
mile.
NEAP HIGH WATER
See NEAP TIDE.
NEAP LOW WATER
See NEAP TIDE.
NEAP RANGE
See NEAP TIDE.
NEAP TIDAL CURRENT
Tidal current of decreased velocity occurring semimonthly
as the result of the moon being in quadrature.
NEAP TIDE
Tide of decreased range occurring semimonthly as the result
of the moon being in quadrature. The NEAP RANGE of the
tide is the average semidiurnal range occurring at the
time of neap tides and is most conveniently computed from
the harmonic constants. The NEAP RANGE is typically 10
to 30 percent smaller than the mean range where the type
of tide is either semidiurnal or mixed and is of no practical
significance where the type of tide is DIURNAL. The average
height of the high waters of the neap tide is called NEAP
HIGH WATER or HIGH WATER NEAPS (MHWN), and the average
height of the corresponding LOW WATER is called NEAP LOW
WATER or LOW WATER NEAPS (MLWN).
NEARSHORE
(1) In beach terminology an indefinite zone extending
seaward from the SHORELINE well beyond the BREAKER ZONE.
(2) The zone which extends from the swash zone to the
position marking the start of the offshore zone, typically
at water depths of the order of 20 m.
NEARSHORE CIRCULATION
The ocean circulation pattern composed of the NEARSHORE
CURRENTS and the COASTAL CURRENTS.
NEARSHORE CURRENT SYSTEM
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.
NECK
(1) The narrow strip of land which connects a peninsula
with the mainland, or connects two ridges. (2) The narrow
band (rip) of water flowing seaward through the surf.
See also RIP CURRENT.
NESS
Roughly triangular promontory of land jutting into the
sea, often consisting of mobile material, i.e. a beach
form.
NETWORK
A set consisting of: (a) stations for which geometric
relationships have been determined and which are so related
that removal of one station from the set will affect the
relationships (distances, directions, coordinates, etc.)
between the other stations; and (b) lines connecting the
stations to show this interdependence.
NIP
The cut made by waves in a shoreline of emergence.
NODAL ZONE
An area in which the predominant direction of the LONGSHORE
TRANSPORT changes.
NODE
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.
NOURISHMENT
The process of replenishing a beach. It may occur naturally
by longshore transport, or be brought about artificially
by the deposition of dredged materials or of materials
trucked in from upland sites.
NUMERICAL MODELING
Refers to analysis of coastal processes using computational
models.
O
OCEANOGRAPHY
The study of the sea, embracing and indicating all knowledge
pertaining to the sea's physical boundaries, the chemistry
and physics of seawater, marine biology, and marine geology.
OFFSHORE
(1) In beach terminology, the comparatively flat zone
of variable width, extending from the SHOREFACE to the
edge of the CONTINENTAL SHELF. It is continually submerged.
(2) The direction seaward from the shore. (3) The zone
beyond the nearshore zone where sediment motion induced
by waves alone effectively ceases and where the influence
of the sea bed on wave action is small in comparison with
the effect of wind. (4) The breaker zone directly seaward
of the low tide line. (See Figure IV-1-2.)
OFFSHORE BARRIER
See BARRIER BEACH.
OFFSHORE BREAKWATER
A BREAKWATER built towards the seaward limit of the littoral
zone, parallel (or nearly parallel) to the shore.
OFFSHORE CURRENT
(1) Any current in the offshore zone. (2) Any current
flowing away from shore.
OFFSHORE WIND
A wind blowing seaward from the land in the coastal area.
ONSHORE
A direction landward from the sea.
ONSHORE WIND
A wind blowing landward from the sea in the coastal area.
OPPOSING WIND
In wave forecasting, a wind blowing in a direction opposite
to the ocean-wave advance; generally, a headwind.
ORBIT
In water waves, the path of a water particle affected
by the wave motion. In deepwater waves the orbit is nearly
circular, and in shallow-water waves the orbit is nearly
elliptical. In general, the orbits are slightly open in
the direction of wave motion, giving rise to MASS TRANSPORT.
(See Figure II-1-4.)
ORBITAL CURRENT
The flow of water accompanying the orbital movement of
the water particles in a wave. Not to be confused with
wave-generated LITTORAL CURRENTS. (See Figure II-1-4.)
ORDINARY HIGH WATER MARK (OHWM)
That mark that will be found by examining the bed and
banks and ascertaining where the presence and action of
waters are so common and usual, and so long continued
in all ordinary years, as to mark upon the soil a character
distinct from that of the abutting upland, in respect
to vegetation as that condition exists on June 1, 1971,
as it may naturally change thereafter, or as it may change
thereafter in accordance with permits issued by a local
government. Also defined as MEAN HIGH WATER LINE (Shalowitz
1962).
ORDINARY TIDE
This expression is not used in a technical sense by the
U.S. Coast and Geodetic Survey, but the word "ordinary"
when applied to tides, may be taken as the equivalent
of the word "mean". Thus "ordinary HIGH
WATER LINE" may be assumed to be the same as "mean
high water line".
ORTHOGONAL
On a wave-refraction diagram, a line drawn perpendicularly
to the wave crests. Also called WAVE RAY. (See Figure
II-3-4)
OSCILLATION
(1) A periodic motion backward and forward. (2) Vibration
or variance above and below a mean value.
OSCILLATORY WAVE
A wave in which each individual particle oscillates about
a point with little or no permanent change in mean position.
The term is commonly applied to progressive oscillatory
waves in which only the form advances, the individual
particles moving in closed or nearly closed orbits. Compare
WAVE OF TRANSLATION. See also ORBIT.
OUTCROP
A surface exposure of bare rock, not covered by soil or
vegetation.
OUTFALL
A structure extending into a body of water for the purpose
of discharging sewage, storm runoff, or cooling water.
OUTFLANKING
EROSION behind or around the land-based end of a GROIN,
JETTY, or BREAKWATER or the terminus of a BULKHEAD, REVETMENT,
or SEAWALL, usually causing failure of the structure or
its function
OVERSPLASH
The water that splashes over the top of a BREAKWATER,
SEAWALL, etc.
OVERTOPPING
Passing of water over the top of a structure as a result
of wave runup or surge action.
OVERWASH
(1) The part of the UPRUSH that runs over the crest of
a BERM or structure and does not flow directly back to
the ocean or lake. (2) The effect of waves overtopping
a COASTAL DEFENSE, often carrying sediment landwards which
is then lost to the beach system.
P
PARAPET
A low wall built along the edge of a structure such as
a SEAWALL or QUAY.
PARTICLE VELOCITY
The velocity induced by wave motion with which a specific
water particle moves within a wave.
PATCH REEF
A moundlike or flat-topped organic REEF, generally less
than 1 km across, frequently forming part of a larger
reef complex.
PASS
In hydrographic usage, a navigable channel through a bar,
REEF, or shoal, or between closely adjacent islands. On
the Gulf of Mexico coast, inlets are often known as passes
(e.g., Sabine Pass).
PEAK PERIOD
The wave period determined by the inverse of the frequency
at which the wave energy spectrum reaches its maximum.
PEBBLES
Beach material usually well-rounded and between about
4 mm to 64 mm diameter. See SOIL CLASSIFICATION.
PENINSULA
An elongated body of land nearly surrounded by water and
connected to a larger body of land by a neck or isthmus.
PERCHED BEACH
A beach or fillet of sand retained above the otherwise
normal profile level by a submerged dike.
PERCOLATION
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.
PERIGEAN RANGE
The average semidiurnal range occurring at the time of
the PERIGEAN TIDES and most conveniently computed from
the harmonic constants. It is larger than the mean range
where the type of tide is either semidiurnal or mixed
and is of no practical significance where the type of
tide is diurnal.
PERIGEAN TIDAL CURRENTS
Tidal currents of increased velocity occurring monthly
as the result of the moon being in perigee (i.e., at the
point in its orbit nearest the Earth).
PERIGEAN TIDES
Tides of increased range occurring monthly as the result
of the moon being in perigee.
PERIODIC CURRENT
A current caused by the tide-producing forces of the moon
and the sun; a part of the same general movement of the
sea that is manifested in the vertical rise and fall of
the tides. See also CURRENT, FLOOD and CURRENT, EBB.
PERMANENT CURRENT
A current that runs continuously, independent of the tides
and temporary causes. Permanent currents include the freshwater
discharge of a river and the currents that form the general
circulatory systems of the oceans.
PERMEABILITY
The property of bulk material (sand, crushed rock, soft
rock in situ) which permit movement of water through its
pores.
PERMEABLE GROIN
A GROIN with openings or voids large enough to permit
passage of appreciable quantities of LITTORAL DRIFT through
the structure.
PETROGRAPHY
The systematic description and classification of rocks.
PETROLOGY
That branch of geology which treats the scientific study
of rocks.
PHASE
In surface wave motion, a point in the period to which
the wave motion has advanced with respect to a given initial
reference point.
PHASE INEQUALITY
Variations in the tides or tidal currents associated with
changes in the phase of the Moon in relation to the Sun.
PHASE VELOCITY
Propagation velocity of an individual wave as opposed
to the velocity of a wave group.
PHI GRADE SCALE
A logarithmic transformation of the Wentworth grade scale
for size classifications of sediment grains based on the
negative logarithm to the base 2 of the particle diameter:
= -log2d. See SOIL CLASSIFICATION.
PHOTIC ZONE
The zone extending downward from the ocean surface within
which the light is sufficient to sustain photosynthesis.
The depth of this layer varies with water clarity, time
of year and cloud cover, but is about 100 m in the open
ocean. It may be considered the Depth to which all light
is filtered out except for about one percent and may be
calculated as about two and one-half times the depth of
a SECCHI DISK reading.
PHOTOGRAMMETRY
The science of deducing the physical dimensions of objects
from measurements on images (usually photographs) of the
objects.
PHOTOMOSAIC
An assemblage of photographs, each of which shows part
of a region, put together in such a way that each point
in the region appears once and only once in the assemblage,
and scale variation is minimized.
PHREATIC LEVEL
Upper surface of an unconfined aquifer (e.g. the top sand
layer in a dike) at which the pressure in the groundwater
is equal to atmospheric pressure.
PHYSICAL GEOLOGY
A large division of Geology concerned with earth materials,
changes of the surface and interior of the earth, and
the forces that cause those changes.
PHYSICAL MODELING
Refers to the investigation of coastal or riverine processes
using a scaled model.
PIER
A structure, usually of open construction, extending out
into the water from the shore, to serve as a landing place,
recreational facility, etc., rather than to afford coastal
protection. In the Great Lakes, a term sometimes improperly
applied to jetties.
PIERSON-MOSKOWITZ SPECTRUM
Wave spectrum typical of fully-developed deep water waves.
PIEZOMETRIC SURFACE The level at which the hydrostatic
water pressure in an aquifer will stand if it is free
to seek equilibrium with the atmosphere. For artesian
wells, this is above the ground surface.
PILE
A long, heavy timber or section of concrete or metal that
is driven or jetted into the earth or seabed to serve
as a support or protection.
PILING
A group of piles.
PIPING
Erosion of closed flow channels (tunnels) by the passage
of water through soil; flow underneath structures, carrying
away particles, may endanger the stability of the structure.
PLACER DEPOSITS
Mineral deposits consisting of dense, resistant and often
economically valuable minerals which have been weathered
from TERRIGENOUS rocks, transported to the sea and concentrated
in marine sediments by wave or current action.
PLACER MINE
Surface mines in which valuable mineral grains are extracted
from stream bar or beach deposits.
PLAIN, COASTAL
See COASTAL PLAIN.
PLANFORM
The outline or shape of a body of water as determined
by the still-water line.
PLATEAU
A land area (usually extensive) having a relatively level
surface raised sharply above adjacent land on at least
one side; table land. A similar undersea feature.
PLEISTOCENE
An epoch of the Quaternary Period characterized by several
glacial ages.
PLUNGE POINT
(1) For a plunging wave, the point at which the wave curls
over and falls. (2) The final breaking point of the waves
just before they rush up on the beach. (See Figure IV-1-2.)
PLUNGING BREAKER
See BREAKER.
POCKET BEACH
A beach, usually small, in a coastal reentrant or between
two littoral barriers.
POINT
(1) The extreme end of a CAPE, or the outer end of any
land area protruding into the water, usually less prominent
than a CAPE. (2) A low profile shoreline promontory of
more or less triangular shape, the top of which extends
seaward.
POORLY-SORTED (POORLY-GRADED)
Said of a clastic sediment or rock that consists of particles
of many sizes mixed together in an unsystematic manner
so that no one size class predominates.
PORE PRESSURE
The interstitial pressure of water within a mass of soil
or rock.
POROSITY
Percentage of the total volume of a soil not occupied
by solid particles but by air and water.
PORT
A place where vessels may discharge or receive cargo;
it may be the entire harbor including its approaches and
anchorages, or only the commercial part of a harbor where
the QUAYS, WHARVES, facilities for transfer of cargo,
docks, and repair shops are situated.
POTENTIAL ENERGY OF WAVES
In a progressive oscillatory wave, the energy resulting
from the elevation or depression of the water surface
from the undisturbed level.
PRISM
See TIDAL PRISM.
PROBABILITY
The chance that a prescribed event will occur, represented
by a number (p) in the range 0 - 1. It can be estimated
empirically from the relative frequency (i.e. the number
of times the particular event occurs, divided by the total
count of all events in the class considered).
PROBABILITY DENSITY
Function specifying the distribution of a variable.
PROBABLE MAXIMUM WATER LEVEL
A hypothetical water level (exclusive of wave runup from
normal wind-generated waves) that might result from the
most severe combination of hydrometeorological, geoseismic,
and other geophysical factors and that is considered
reasonably possible in the region involved, with each
of these factors considered as affecting the locality
in a maximum manner.
This level represents the physical response of a body
of water to maximum applied phenomena such as hurricanes,
moving squall lines, other cyclonic meteorological events,
tsunamis, and astronomical tide combined with maximum
probable ambient hydrological conditions such as wave
setup, rainfall, runoff, and river flow. It is a water
level with virtually no risk of being exceeded.
PRODELTA
The part of a DELTA that is below the effective depth
of wave erosion, lying beyond the delta front and sloping
down into the basin into which the delta is advancing.
PROFILE, BEACH
The intersection of the ground surface with a vertical
plane; may extend from the behind the DUNE line or the
top of a bluff to well seaward of the breaker zone.
(See Figure IV-1-2.)
PROGRESSION (of a beach)
See ADVANCE.
PROGRESSIVE WAVE
A wave that moves relative to a fixed coordinate system
in a fluid. The direction in which it moves is termed
the direction of wave propagation.
PROMONTORY
A high point of land projecting into a body of water;
a HEADLAND.
PROPAGATION OF WAVES
The transmission of waves through water.
PROTOTYPE
In laboratory usage, the full-scale structure, concept,
or phenomenon used as a basis for constructing a scale
model or copy.
Q
QUARRY RUN
Waste of generally small material, in a quarry, left after
selection of larger grading.
QUARRYSTONE
Any stone processed from a quarry.
QUATERNARY
(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.
QUAY (pronounced KEY)
A stretch of paved bank, or a solid artificial landing
place parallel to the navigable waterway, for use in loading
and unloading vessels.
QUICKSAND
Loose, yielding, wet sand which offers no support to heavy
objects. The upward flow of the water has a velocity that
eliminates contact pressures between the sand grains and
causes the sand-water mass to behave like a fluid that
yields easily to pressure and tends to suck down heavy
objects.
R
RADAR
An instrument for determining the distance and direction
to an object by measuring the time needed for radio signals
to travel from the instrument to the object and back,
and by measuring the angle through which the instrument=s
antenna has traveled.
RADIOACTIVE DATING (RADIOMETRIC DATING)
Calculating an age in years for geologic materials by
measuring the presence of a short-life radioactive element
(e.g., carbon-14) or a long-life element (e.g., potassium-40/argon-40).
The term applies to all methods of age determination based
on nuclear decay of naturally-occurring radioactive isotopes.
Carbon-14 methods are often used to determine the age
of peat or wood found in BARRIER ISLANDS.
RADIUS OF MAXIMUM WINDS
Distance from the eye of a hurricane, where surface and
wind velocities are zero, to the place where surface windspeeds
are maximum.
RAISED BEACH
A wave-cut platform, with or without a covering of beach
materials, which is now raised above the present sea-level.
RANDOM WAVES
The laboratory simulation of irregular sea states that
occur in nature.
RANGE OF TIDE
The difference in height between consecutive high and
low waters. The MEAN RANGE is the difference between MEAN
HIGH WATER and MEAN LOW WATER. The GREAT DIURNAL RANGE
or DIURNAL RANGE is the difference in height between MEAN
HIGHER HIGH WATER (MHHW) and MEAN LOWER LOW WATER (MLLW).
Where the type of tide is diurnal, the mean range is the
same as the diurnal range.
RAY, WAVE
See ORTHOGONAL.
RAYLEIGH DISTRIBUTION
A model probability distribution, commonly used in analysis
of waves.
REACH
(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.
RECENT
(Geological) A synonym of HOLOCENE. See also QUATERNARY.
RECESSION
(1) A continuing landward movement of the shoreline. (2)
A net landward movement of the shoreline over a specified
time.
RECHARGE
The addition of new water to an AQUIFER or to the zone
of saturation.
RECTIFICATION
The process of producing, from a tilted or oblique photograph,
a photograph from which displacement caused by tilt has
been removed.
RECURVED SPIT
A spit whose outer end in turned landward by current deflection,
by the opposing action of two or more currents, or by
WAVE REFRACTION; a HOOK.
RED TIDE Discoloration of surface waters, most frequently
in COASTAL ZONES, caused by large concentrations of microorganisms.
REEF
An offshore consolidated rock hazard to navigation, with
a least depth of about 20 meters (10 fathoms) or less.
Often refers to coral FRINGING REEFS in tropical waters.
REEF, ATOLL
See ATOLL.
REEF, BARRIER
See BARRIER REEF.
REEF BREAKWATER
Rubble mound of single-sized stones with a crest at or
below sea level which is allowed to be (re)shaped by the
waves.
REEF, FRINGING
See FRINGING REEF.
REFERENCE PLANE
The plane to which sounding and tidal data are referred.
See DATUM PLANE.
REFERENCE POINT
(1) A specified location (in plan elevation) to which
measurements are referred. (2) In beach material studies,
a specified point within the REFERENCE ZONE.
REFERENCE STATION
A place for which tidal constants have previously been
determined and which is used as a standard for the comparison
of simultaneous observations at a second station. Also,
a station for which independent daily predictions are
given in the tide or current tables from which corresponding
predictions are obtained for other stations by means of
differences or factors.
REFERENCE ZONE
In regard to beach measuring procedure, the part of the
FORESHORE subject to wave action (between the Limit of
UPRUSH and the Limit of BACKWASH) at mid-tide stage. In
areas of great tidal range a more complex definition is
needed.
REFLECTED WAVE
That part of an incident wave that is returned seaward
when a wave impinges on a steep beach, barrier, or other
reflecting surface.
REFLECTION
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.)
REFRACTION COEFFICIENT
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.
REFRACTION DIAGRAM
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.)
REGULAR WAVES
Waves with a single height, period, and direction.
RESERVOIR
An artificial lake, basin or tank in which a large quantity
of water can be stored.
RESIDUAL (WATER LEVEL)
The components of water level not attributable to astronomical
effects.
RESONANCE
The phenomenon of amplification of a free wave or oscillation
of a system by a forced wave or oscillation of exactly
equal period. The forced wave may arise from an impressed
force upon the system or from a boundary condition.
RETARDATION
The amount of time by which corresponding tidal phases
grow later day by day (about 50 minutes).
RETROGRESSION (of a beach)
See RECESSION.
RETURN PERIOD
Average period of time between occurrences of a given
event.
REVERSING TIDAL CURRENT
A tidal current that flows alternately in approximately
opposite directions with a SLACK WATER at each reversal
of direction. Currents of this type usually occur in rivers
and straits where the direction of flow is more or less
restricted to certain channels. When the movement is towards
the shore, the current is said to be flooding, and when
in the opposite direction it is said to be ebbing.
REVETMENT
(1) A facing of stone, concrete, etc., to protect an EMBANKMENT,
or shore structure, against erosion by wave action or
currents. (2) A retaining wall. (3) Facing of stone, concrete,
etc., built to protect a SCARP, EMBANKMENT or shore structure
against erosion by waves of currents.
REYNOLDS NUMBER
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.
RIA
A long, narrow inlet, with depth gradually diminishing
inward. Shorter and shallower than a FJORD.
RIDGE AND RUNNEL
Beach topography consisting of sand bars that have welded
to the shore during the recovery stage after a storm.
At low tide, water ponds in the runnels and flows seaward
through gaps in the ridge (see Figure IV-2-31).
RIDGE, BEACH
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.
RILL MARKS
Tiny drainage channels in a beach caused by the flow seaward
of water left in the sands of the upper part of the beach
after the retreat of the tide or after the dying down
of storm waves.
RIP
A body of water made rough by waves meeting an opposing
current, particularly a tidal current; often found where
tidal currents are converging and sinking.
RIP CHANNEL
A channel cut by seaward flow of RIP CURRENT, usually
crosses a LONGSHORE BAR.
RIP CURRENT
A strong surface current 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. With the seaward movement
concentrated in a limited band its velocity is somewhat
accentuated. A rip consists of three parts: the FEEDER
CURRENTS 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 OF RIP, where the current widens and slackens
outside the breaker line. A rip current is often miscalled
a rip tide. Also called RIP SURF.
RIP SURF
See RIP CURRENT.
RIP TIDE
Incorrect term for RIP CURRENT.
RIPARIAN
(1) Pertaining to the banks of a body of water. (2) Of,
on or pertaining to the banks of a river.
RIPPLE
(1) The ruffling of the surface of water; hence, a little
curling wave or undulation. (2) A wave less than 0.05
meter (2 inches) long controlled to a significant degree
by both surface tension and gravity. See CAPILLARY WAVE
and GRAVITY WAVE.
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.
RIPPLES (bed forms)
Small bed forms with wavelengths less than 0.3 m (1 foot)
and heights less than 0.03 m (0.1 foot).
RIPRAP
A protective layer or facing of quarrystone, usually well
graded within wide size limit, randomly placed to prevent
erosion, scour, or sloughing of an embankment or bluff;
also the stone so used. The quarrystone is placed in a
layer at least twice the thickness of the 50 percent size,
or 1.25 times the thickness of the largest size stone
in the gradation.
RISK ANALYSIS
Assessment of the total risk due to all possible environmental
inputs and all possible mechanisms.
ROCK WEATHERING
Physical and mineralogical decay processes in rock brought
about by exposure to climatic conditions either at the
present time or in the geological past.
ROCK
(1) An aggregate of one or more minerals; or a body of
undifferentiated mineral matter (e.g., obsidian). The
three classes of rocks are: (a) Igneous B crystalline
rocks formed from molten material. Examples are granite
and basalt. (b) Sedimentary B resulting from the consolidation
of loose sediment that has accumulated in layers. Examples
are sandstone, shale and limestone. (c) Metamorphic B
formed from preexisting rock as a result of burial, heat,
and pressure. (2) A rocky mass lying at or near the surface
of the water or along a jagged coastline, especially where
dangerous to shipping.
ROLLER
An indefinite term, sometimes considered to denote one
of a series of long-crested, large waves which roll in
on a shore, as after a storm.
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 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.
RUBBLE
(1) Loose angular waterworn stones along a beach. (2)
Rough, irregular fragments of broken rock.
RUBBLE-MOUND STRUCTURE
A mound of random-shaped and random-placed stones protected
with a cover layer of selected stones or specially shaped
concrete armor units. (Armor units in a primary cover
layer may be placed in an orderly manner or dumped at
random.)
RUN-UP, RUN-DOWN
The upper and lower levels reached by a wave on a beach
or coastal structure, relative to still-water level.
RUNNEL
A corrugation or trough formed in the foreshore or in
the bottom just offshore by waves or tidal currents.
S
S-SLOPE BREAKWATER
Rubble mound with gentle slope around still-water level
and steeper slopes above and below.
SALIENT
Coastal formation of beach material developed by WAVE
REFRACTION and diffraction and long shore 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 and Cusp.
SALINITY
Number of grams of salt per thousand grams of sea water,
usually expressed in parts per thousand (symbol: l).
SALINITY GRADIENT
Change in salinity with expressed in parts per thousand
per foot.
SALT MARSH
A marsh periodically flooded by salt water (also tidal
marsh; sea marsh).
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
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.
SAND
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.
SAND BAR
(1) See BAR. (2) In a river, a ridge of sand built to
or near the surface by river currents.
SAND BYPASSING
See BYPASSING, SAND.
SAND DUNE
A DUNE formed of sand.
SAND REEF
See BAR.
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, BEACH
An almost vertical slope along the beach caused by erosion
by wave action. It may vary in height from a few cm to
a meter or so, depending on wave action and the nature
and composition of the beach. (See Figure IV-1-2.) See
also ESCARPMENT.
SCATTER DIAGRAM
A two-dimensional histogram showing the joint probability
density of two variables within a data sample.
SCOUR
Removal of underwater material by waves and currents,
especially at the base or toe of a shore structure.
SCOUR PROTECTION
Protection against erosion of the seabed in front of the
toe.
SEA
(1) 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. Examples: Mediterranean
Sea; South China Sea. (2) Waves caused by wind at the
place and time of observation. (3) State of the ocean
or lake surface, in regard to waves.
SEA BREEZE
A light wind blowing from the sea toward the land caused
by unequal heating of land and water masses.
SEA CHANGE
(1) A change wrought by the sea. (2) A marked transformation.
SEA CLIFF
A cliff situated at the seaward edge of the coast.
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
See MEAN SEA LEVEL.
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.
SEA STATE
Description of the sea surface with regard to wave action.
Also called state of sea.
SEACOAST
The coast adjacent to the sea or ocean.
SEAMOUNT
An elevation rising more than 1000 meters above the ocean
floor, and of limited extent across the summit. Compare
KNOLL.
SEAS
Waves caused by wind at the place and time of observation.
SEASHORE
(1) (Law) All ground between the ordinary high-water and
low-water mark. (2) The shore of the sea or ocean, often
used in a general sense (e.g., to visit the seashore).
SEAWALL
(1) A structure, often concrete or stone, built along
a portion of a coast to prevent erosion and other damage
by wave action. Often it retains earth against its shoreward
face. (2) A structure separating land and water areas
to alleviate the risk of flooding by the sea. Generally
shore-parallel, although some reclamation SEAWALLS may
include lengths that are normal or oblique to the (original)
shoreline. A SEAWALL is typically more massive and capable
of resisting greater wave forces than a BULKHEAD.
SECHHI DISK
Visibility disk (white and black, 30 cm diameter) used
to measure the transparency of the water
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) 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 near shore sea
bed do not significantly affect beaches in the adjacent
lengths of coastline.
SEDIMENT SINK
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.
SEDIMENT SOURCE
Point or area on a coast from which beach material is
supplied, such as an eroding cliff, or river mouth.
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 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.
SEDIMENT TRANSPORT PATHS
The routes along which net sediment movement occurs.
SEEPAGE
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.
SEICHE
(1) A standing wave oscillation of an enclosed waterbody
that continues, pendulum fashion, after the cessation
of the originating force, which may have been either seismic
or atmospheric. (2) An oscillation of a fluid body in
response to a disturbing force having the same frequency
as the natural frequency of the fluid system. Tides are
now considered to be seiches induced primarily by the
periodic forces caused by the Sun and Moon. (3) In the
Great Lakes area, any sudden rise in the water of a harbor
or a lake whether or not it is oscillatory (although inaccurate
in a strict sense, this usage is well established in the
Great Lakes area).
SEISMIC REFLECTION
The return of part of the energy of seismic waves to the
earth=s surface after the waves bounce off an acoustic
boundary (typically rock or material of different density).
SEISMIC REFRACTION
The bending of seismic waves as they pass from one material
to another.
SEISMIC SEA WAVE
See TSUNAMI.
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.
SELF-SUSTAINING BEACH
A BEACH that has either natural or engineered sand retention
and that can be stable through the continued supply of
natural sediment sources, without any mechanical nourishment
over a long period. Subsets include:
Natural or Geomorphically Self-sustaining Beaches: self-sustaining
naturally without the construction of retaining structures
and with no continued mechanical sand nourishment.
Anthropogenically Self-sustaining Beaches: self-sustaining
by the construction of retaining structure(s) with or
without initial beach fill but with no continued mechanical
sand nourishment.
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.
SENSING, REMOTE
The response of an instrument or organism to stimuli from
a distant source.
SETBACK
A required open space, specified in shoreline master programs,
measured horizontally upland from an perpendicular to
the ordinary high water mark.
SETUP, WAVE
Superelevation of the water surface over normal surge
elevation due to onshore mass transport of the water by
wave action alone.
SETUP, WIND
See WIND SETUP.
SHALLOW WATER
(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 with regard
to progressive gravity waves, water in which the depth
is less than 1/25 the wavelength.
SHALLOW WATER WAVE
A PROGRESSIVE WAVE which is in water less than 1/25 the
wave length in depth.
SHEAR INSTABILITIES
Instabilities of the surf zone longshore current commonly
found on beaches with barred depth profiles. These instabilities
are vertical motions with little surface elevation expression.
Conservation of vorticity is the restoring mechanism.
SHEAR WAVES
See SHEAR INSTABILITIES
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 PILE See PILE, SHEET.
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.
SHELF, INSULAR
See INSULAR SHELF.
SHINGLE
(1) Loosely and commonly, any beach material coarser than
ordinary gravel, especially any having flat or flattish
pebbles. (2) Strictly and accurately, beach material of
smooth, well-rounded pebbles that are roughly the same
size. The spaces between pebbles are not filled with finer
materials. Shingle often gives out a musical sound when
stepped on. The term is more widely used in Great Britain
than in the U.S.
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.
SHOALING
Decrease in water depth. The transformation of wave profile
as they propagate inshore.
SHOALING COEFFICIENT
The ratio of the height of a wave in water of any depth
to its height in deep water with the effects of refraction,
friction, and percolation eliminated. Sometimes SHOALING
FACTOR or DEPTH FACTOR. See also ENERGY COEFFICIENT and
REFRACTION COEFFICIENT.
SHOALING FACTOR
See SHOALING COEFFICIENT.
SHORE
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).
SHORE NORMAL
A line at right-angles to the contours in the surf zone.
SHORE TERRACE
A terrace made along a COAST by the action of waves and
shore currents; it may become dry land by the uplifting
of the shore or the lowering of the water. Also known
as shore platform or wave-cut platform.
SHOREFACE
The narrow zone seaward from the low tide SHORELINE, covered
by water, over which the beach sands and gravels actively
oscillate with changing wave conditions. See INSHORE (ZONE).
( See Figure IV-1-2.)
SHORELINE
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.
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. The composition of the higher waves
depends upon the extent to which the lower waves are considered.
Experience indicates that a careful observer who attempts
to establish the character of the higher waves will record
values which approximately fit the definition of the significant
wave.
SIGNIFICANT WAVE HEIGHT
The average height of the one-third highest waves of a
given wave group. Note that the composition of the highest
waves depends upon the extent to which the lower waves
are considered. In wave record analysis, the average height
of the highest one-third of a selected number of waves,
this number being determined by dividing the time of record
by the significant period. Also CHARACTERISTIC WAVE HEIGHT.
SIGNIFICANT WAVE PERIOD
An arbitrary period generally taken as the period of the
one-third highest waves within a given group. Note that
the composition of the highest waves depends upon the
extent to which the lower waves are considered. In wave
record analysis, this is determined as the average period
of the most frequently recurring of the larger well-defined
waves in the record under study.
SILL
(1) A submerged structure across a river to control the
water level upstream. (2) The crest of a spillway.
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. See SOIL CLASSIFICATION.
SINUSOIDAL WAVE
An oscillatory wave having the form of a sinusoid.
SLACK TIDE (SLACK WATER)
The state of a tidal current when its velocity is near
zero, especially the moment when a reversing current changes
direction and its velocity is zero. Sometimes considered
the intermediate period between ebb and flood currents
during which the velocity of the currents is less than
0.05 meter per second (0.1 knot). See STAND OF TIDE.
SLIDE
In mass wasting, movement of a descending mass along a
plane approximately parallel to the slope of the surface.
SLIP
A berthing space between two piers.
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 deg.).
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. See BAYOU.
SLUICE
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.
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; in geologic usage, usually defined as containing
organic matter and being capable of supporting plant growth.
SOIL CLASSIFICATION (size)
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).
SOLITARY WAVE
A wave consisting of a single elevation (above the original
water surface), whose height is not necessarily small
compared to the depth, and neither followed nor preceded
by another elevation or depression of the water surfaces.
SORTING
Process of selection and separation of sediment grains
according to their grain size (or grain shape or specific
gravity).
SORTING COEFFICIENT
A coefficient used in describing the distribution of grain
sizes in a sample of unconsolidated material. It is defined
as So = Q1/Q3 , where Q1 is the diameter (in millimeters)
which has 75 percent of the cumulative size-frequency
(by weight) distribution smaller than itself and 25 percent
larger than itself, and Q3 is that diameter having 25
percent smaller and 75 percent larger than itself.
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. Example: Long Island Sound. (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 also CHART
DATUM.
SOUNDING LINE
A line, wire, or cord used in sounding, which is weighted
at one end with a plummet (sounding lead). Also LEAD LINE.
SPILLING BREAKER
See BREAKER.
SPILLOVER LOBE
Linguoid, bar-like feature formed by ebb tidal current
flow over a low area of an ebb shield.
SPILLWAY
A structure over or through a dam for discharging flood
flows.
SPIT
A small point of land or a narrow shoal projecting into
a body of water from the shore. (See Figure IV-1-6.)
SPOIL
Overburden or other waste material removed in mining,
dredging, and quarrying.
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 (SYZYGY) and which rises highest and falls lowest
from the mean sea level.
SPUR-DIKE
See GROIN.
STACK
An isolated, pillar-like rocky island isolated from a
nearby headland by wave erosion; a needle or chimney rock.
STAND OF TIDE
A interval at high or low water when there is no sensible
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.
STANDARD PROJECT HURRICANE
See HYPOTHETICAL HURRICANE.
STANDING WAVE
A type of wave in which the surface of the water oscillates
vertically between fixed points, called nodes, without
progression. The points of maximum vertical rise and fall
are called antinodes or loops. At the nodes, the underlying
water particles exhibit no vertical motion, but maximum
horizontal motion. At the antinodes, the underlying water
particles have no horizontal motion, but maximum vertical
motion. They may be the result of two equal progressive
wave trains traveling through each other in opposite directions.
Sometimes called CLAPOTIS or STATIONARY WAVE.
STATION, CONTROL
A point on the ground whose horizontal or vertical location
is used as a basis for obtaining locations of other points.
STATIONARY WAVE
A wave of essentially stable form which does not move
with respect to a selected reference point; a fixed swelling.
Sometimes called STANDING WAVE.
STEP
The nearly horizontal section which more or less divides
the BEACH from the SHOREFACE.
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.
STOCHASTIC
Having random variation in statistics.
STOCKPILE
Sand piled on a beach foreshore to nourish downdrift beaches
by natural littoral currents or forces. See FEEDER BEACH.
STONE
Quarried or artificially-broken rock for use in construction,
either as aggregate or cut into shaped blocks as dimension
stone.
STONE, DERRICK
Stone heavy enough to require handling individual pieces
by mechanical means, generally weighing 900 kg (1 ton)
and up.
STORM SURGE
A rise above normal water level on the open coast due
to the action of wind stress on the water surface. Storm
surge resulting from a hurricane also includes that rise
in level due to atmospheric pressure reduction as well
as that due to wind stress. See WIND SETUP.
STORM TIDE
See STORM SURGE.
STRAIT
A relatively narrow waterway between two larger bodies
of water (e.g., Strait of Gibraltar). See also SOUND.
STRAND
(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.
STRAND PLAIN
A prograded shore built seawards by waves and currents.
STRANDFLAT
A wave-cut platform; an elevated wave-cut terrace
STRANDING
The running aground of a ship upon a STRAND, ROCK, or
bottom so that it is fast for a time.
STRANDLINE
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
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) 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.
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.
SUBAERIAL
Situated or occurring on or adjacent to the surface of
the earth, usually meaning above the water surface.
SUBAERIAL BEACH
That part of the beach which is uncovered by water (e.g.
at low tide sometimes referred to as drying beach).
SUBAQUEOUS Existing, formed, or taking place under water;
submerged
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 meters and is often identifiable on surveys
by a break in the slope of the bed.
SUBCRITICAL FLOW
Flow for which the Froude number is less than unity; surface
disturbances can travel upstream.
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.
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.
SUBTIDAL
Below the low-water datum; thus permanently .
SUPER-CRITICAL FLOW
Flow for which the Froude number is greater than unity;
surface disturbances will not travel upstream.
SURF
(1) Collective term for BREAKERS. (2) The wave activity
in the area between the shoreline and the outermost limit
of breakers. (3) In literature, the term surf 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 the nearshore water level with
periods on the order of several minutes.
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 to 10 meters.
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.
SURFACE WATER WAVE
See SURFACE GRAVITY WAVE (PROGRESSIVE).
SURGE
(1) The name applied to wave motion with a period intermediate
between that of the ordinary wind wave and that of the
tide, say from 2 to 60 min. It is low height, usually
less than 0.9 m (3 ft). See also SEICHE. (2) In fluid
flow, long interval variations in velocity and pressure,
not necessarily periodic, perhaps even transient in nature.
(3) see STORM SURGE.
SURGING BREAKER
See BREAKER.
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
(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."
SUSPENDED LOAD SAMPLER
A sampler which attempts to secure a sample of the water
with its sediment load without separating the sediment
from the water.
SUSTAINABLE BEACH
A beach area that is now and will continue to receive
sufficient sediment input over a long period (years or
decades) to remain stable. Such sediment input can be
through either natural supplies of sediment or various
forms of mechanical beach nourishment (placement by hydraulic
dredge, land haul of material, nearshore deposition, etc.)
SWALE
The depression between two beach ridges.
SWASH
The rush of water up onto the beach face following the
breaking of a wave. Also UPRUSH, RUNUP.
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. Sand bodies that form and
migrate across ebb-tidal shoals because of currents generated
by breaking waves.
SWASH CHANNEL
(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.
SWASH MARK
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.
SWASH PLATFORM
Sand sheet located between the main ebb channel of a coastal
inlet and an adjacent barrier island.
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.
SWELL
Wind-generated waves that have traveled out of their generating
area. Swell characteristically exhibits a more regular
and longer period and has flatter crests than waves within
their fetch (SEAS).
SYNOPTIC CHART
A chart showing the distribution of meteorological conditions
over a given area at a given time. Popularly called a
weather map.
SYZYGY
The two points in the Moon's orbit when the Moon is in
conjunction or opposition to the Sun relative to the Earth;
time of new or full Moon in the cycle of phases.
T
T-GROIN
A GROIN built in the shape of a letter AT@ with the trunk
section connected to land.
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.
TERMINAL GROIN
A GROIN, often at the end of a barrier spit, intended
to prevent sediment passage into the channel beyond.
TERRACE
A horizontal or nearly horizontal natural or artificial
topographic feature interrupting a steeper slope, 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
In hydraulics, the line joining the deepest points of
an inlet or stream channel.
THRESHOLD OF MOTION
The point at which the forces imposed on a sediment particle
overcome its inertia and it starts to move.
THRESHOLD VELOCITY
The maximum orbital velocity at which the sediment on
the BED begins to move as waves approach shallow water.
TIDAL CREEK
A creek draining back-barrier areas with a current generated
by the rise and fall of the tide.
TIDAL CURRENT
See CURRENT, TIDAL.
TIDAL DATUM
See CHART DATUM and DATUM PLANE.
TIDAL DAY
The time of the rotation of the Earth with respect to
the Moon, or the interval between two successive upper
transits of the Moon over the meridian of a place, approximately
24.84 solar hours (24 hours and 50 minutes) or 1.035 times
the mean solar day. (See Figure II-5-16.) Also called
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) Marshy or
muddy areas of the seabed which are covered and uncovered
by the rise and fall of tidal water.
TIDAL INLET
(1) A natural inlet maintained by tidal flow. (2) Loosely,
any inlet in which the tide ebbs and flows. Also TIDAL
OUTLET.
TIDAL MARSH
Same as TIDAL FLATS.
TIDAL PERIOD
The interval of time between two consecutive, like phases
of the tide. (See Figure II-5-16.)
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) The volume of water present between
MEAN LOW and MEAN HIGH TIDE.
TIDAL RANGE
The difference in height between consecutive high and
low (or higher high and lower low) waters. (See Figure
II-5-16.)
TIDAL RISE
The height of tide as referred to the datum of a chart.
(See Figure II-5-16.)
TIDAL RIVER
That part of a river where the water level is influenced
by the tide.
TIDAL SHOALS
Shoals that accumulate near inlets due to the transport
of sediments by tidal currents associated with the inlet.
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) The wave motion of the tides. (2) In popular usage,
any 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 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.
TIDE, DAILY RETARDATION OF
The amount of time by which corresponding tides grow later
day by day (about 50 minutes). Also LAGGING.
TIDE, DIURNAL
A tide with one high water and one low water in a day.
(See Figure II-5-16)
TIDE, EBB
See EBB TIDE.
TIDE, FLOOD
See FLOOD TIDE.
TIDE, MIXED See MIXED TIDE.
TIDE, NEAP
See NEAP TIDE.
TIDE, SEMIDIURNAL
See SEMIDIURNAL TIDE.
TIDE, SLACK
See SLACK TIDE.
TIDE, SPRING
See SPRING TIDE.
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
designed for removal from the water when not in use.
TIDE STATION
A place at which tide observations are being taken. 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, STORM
See STORM SURGE.
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, WIND
See WIND TIDE.
TIDES, RIP
See RIP.
TOE
Lowest part of sea- and portside BREAKWATER slope, generally
forming the transition to the seabed..
TOMBOLO
A bar or spit that connects or "ties" an island
to the mainland or to another island. See CUSPATE SPIT.
(See Figure IV-1-6.). Also applied to sand accumulation
between land and a DETACHED BREAKWATER.
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 configuration of a surface, including its relief and
the positions of its streams, roads, building, etc.
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
is thousands or millions of years. The plane of marine
transgression is a plane of UNCONFORMITY.
TRANSITIONAL ZONE (TRANSITIONAL WATER)
In regard to progressive gravity waves, water whose depth
is less than 2 but more than 1/25 the wavelength. Often
called shallow water.
TRANSLATORY WAVE
See WAVE OF TRANSLATION.
TRANSPOSED HURRICANE
See HYPOTHETICAL HURRICANE.
TRANSVERSE BAR
A bar which extends approximately right angles to shorelines.
TRANSVERSE WAVE
Waves that propagate along a sailing line of a vessel.
(See Figure II-7-40)
TRENCH
A long narrow submarine depression with relatively steep
sides.
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
TROPICAL CYCLONE
See HURRICANE
TROPICAL STORM
A tropical cyclone with maximum winds less than 34 m/sec
(75 mile per hour). Compare with HURRICANE or TYPHOON
(winds greater than 34 m/sec).
TROUGH
A long and broad submarine DEPRESSION with gently sloping
sides.
TROUGH OF WAVE
The lowest part of a waveform between successive crests.
Also, that part of a wave below still-water level.
TRUNCATED LANDFORM
A landform cut off, especially by EROSION, and forming
a steep side or CLIFF.
TSUNAMI
A long-period wave caused by an underwater disturbance
such as a volcanic eruption or earthquake. Also SEISMIC
SEA WAVE. Commonly miscalled "tidal wave."
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.
TYPHOON
See HURRICANE. The term typhoon is applied to tropical
cyclones in the western Pacific Ocean.
U
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 unconformity pre-supposes
a standard >scale= of deposition which is complete.
Major breaks in sedimentation can usually be demonstrated
easily, but minor breaks may go unrecorded until highly
detailed investigations are made. (3) Structure. Structurally,
unconformity may be regarded as planar structures separating
older rocks below from younger rocks above, representing
the >break= as defined in (1) and (2) above. A plane
of unconformity may be a surface of weathering, Erosion
or denudation, or a surface of non-deposition, or possibly
some combination of these factors. It may be parallel
to the upper strata, make an angle with the upper strata,
or be irregular. Subsequent Earth movements may have folded
or faulted it.
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 Aundertow@
are actually RIP CURRENTS.
UNDERWATER GRADIENT
The slope of the sea bottom. See SLOPE.
UNDISTURBED WATER LEVEL
Same as STILL WATER LEVEL.
UNDULATION
A continuously propagated motion to and fro, in any fluid
or elastic medium, with no permanent translation of the
particles themselves.
UPCOAST
In United States usage, the coastal direction generally
trending toward the north.
UPDRIFT
The direction opposite that of the predominant movement
of littoral materials.
UPLAND
Dry land area above and landward of the ORDINARY HIGH
WATER MARK (OHWM). Often used as a general term to mean
high land far from the COAST and in the interior of the
country.
UPLIFT
The upward water pressure on the base of a structure or
pavement.
UPRUSH
The rush of water up the FORESHORE following the breaking
of a wave, also called SWASH or RUNUP.
UPSTREAM
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.
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.
V
VALLEY
An elongated depression, usually with an outlet, between
BLUFFS or between ranges of hills or mountains.
VALLEY, SEA
A submarine depression of broad valley form without the
steep side slopes which characterize a canyon.
VALLEY, SUBMARINE
A prolongation of a land valley into or across a continental
or insular shelf, which generally gives evidence of having
been formed by stream erosion.
VELOCITY OF WAVES
The speed at which an individual wave advances. See WAVE
CELERITY.
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.
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.
W
WASH LOAD
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.
WASHOVER
Sediment deposited inland of a beach by overwash processes.
WATER DEPTH
Distance between the seabed and the still water level.
WATER LEVEL
Elevation of still water level relative to some datum.
WATERLINE
A juncture of land and sea. This line migrates, changing
with the tide or other fluctuation in the water level.
Where waves are present on the beach, this line is also
known as the limit of backrush (approximately, the intersection
of the land with the still-water level.)
WAVE
A ridge, deformation, or undulation of the surface of
a liquid.
WAVE AGE
The ratio of wave speed to wind speed.
WAVE, CAPILLARY
See CAPILLARY WAVE.
WAVE CELERITY
The speed of wave propagation.
WAVE CLIMATE
The seasonal and annual distribution of wave height, period
and direction.
WAVE CLIMATE ATLAS
Series of maps showing the variability of wave conditions
over a long coastline.
WAVE CREST
See CREST OF WAVE.
WAVE CREST LENGTH
See CREST LENGTH, WAVE.
WAVE, CYCLOIDAL
See CYCLOIDAL WAVE.
WAVE DECAY
See DECAY OF WAVES.
WAVE DIRECTION
The direction from which a wave approaches.
WAVE DIRECTIONAL SPECTRUM
Distribution of wave energy as a function of wave frequency
and direction.
WAVE FORECASTING
The theoretical determination of future wave characteristics,
usually from observed or predicted meteorological phenomena.
WAVE FREQUENCY
The inverse of wave period.
WAVE FREQUENCY SPECTRUM
Distribution of wave energy as a function of frequency.
WAVE, GRAVITY
See GRAVITY WAVE.
WAVE GROUP
A series of waves in which the wave direction, wavelength,
and wave height vary only slightly. See also GROUP VELOCITY.
WAVE HEIGHT
The vertical distance between a crest and the preceding
trough. See also SIGNIFICANT WAVE HEIGHT.
WAVE HEIGHT COEFFICIENT
The ratio of the wave height at a selected point to the
deepwater wave height. The REFRACTION COEFFICIENT multiplied
by the shoaling factor.
WAVE HINDCASTING
See HINDCASTING, WAVE.
WAVE, INFRAGRAVITY
See INFRAGRAVITY WAVE.
WAVE, IRROTATIONAL
See IRROTATIONAL WAVE.
WAVE, MONOCHROMATIC
See MONOCHROMATIC WAVES.
WAVE OF TRANSLATION
A wave in which the water particles are permanently displaced
to a significant degree in the direction of wave travel.
Distinguished from an OSCILLATORY WAVE.
WAVE, OSCILLATORY
See OSCILLATORY WAVE.
WAVE PEAK FREQUENCY
The inverse of wave peak period.
WAVE PERIOD
The time for a wave crest to traverse a distance equal
to one wavelength. The time for two successive wave crests
to pass a fixed point. See also SIGNIFICANT WAVE PERIOD.
WAVE, PROGRESSIVE
See PROGRESSIVE WAVE.
WAVE PROPAGATION
The transmission of waves through water.
WAVE RAY See ORTHOGONAL.
WAVE, REFLECTED
That part of an incident wave that is returned seaward
when a wave impinges on a steep beach, barrier, or other
reflecting surface.
WAVE REFRACTION
See REFRACTION (of water waves).
WAVE ROSE
Diagram showing the long-term distribution of wave height
and direction.
WAVE SETDOWN
Drop in water level outside of the breaker zone to conserve
momentum as wave particle velocities and pressures change
prior to wave breaking.
WAVE SETUP
See SETUP, WAVE.
WAVE, SINUSOIDAL
An oscillatory wave having the form of a sinusoid.
WAVE, SOLITARY
See SOLITARY WAVE.
WAVE SPECTRUM
In ocean wave studies, a graph, table, or mathematical
equation showing the distribution of wave energy as a
function of wave frequency. The spectrum may be based
on observations or theoretical considerations. Several
forms of graphical display are widely used.
WAVE, STANDING
See STANDING WAVE.
WAVE STEEPNESS
The ratio or wave height to wavelength also known as sea
steepness.
WAVE TRAIN
A series of waves from the same direction.
WAVE TRANSFORMATION
Change in wave energy due to the action of physical processes.
WAVE, TROCHOIDAL
See TROCHOIDAL WAVE.
WAVE TROUGH
The lowest part of a wave form between successive crests.
Also that part of a wave below still-water level.
WAVE VELOCITY
The speed at which an individual wave advances.
WAVE, WIND
See WIND WAVES.
WAVELENGTH
The horizontal distance between similar points on two
successive waves measured perpendicular to the crest.
WAVES, INTERNAL
See INTERNAL WAVES.
WEIBULL DISTRIBUTION
A model probability distribution, commonly used in wave
analysis.
WEIR
A low dam or wall across a stream to raise the upstream
water level. Termed fixed crest weir when uncontrolled.
WEIR JETTY
A jetty with a low section or weir over which littoral
drift moves into a predredged deposition basin which is
then dredged periodically.
WETLANDS
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).
WELL-SORTED
Clastic sediment or rock that consists of particles all
having approximately the same size. Example: sand dunes.
WHARF
A structure built on the shore of a harbor, river, or
canal, so that vessels may lie alongside to receive and
discharge cargo and passengers.
WHITECAP
On the crest of a wave, the white froth caused by wind.
WICKER FAGGOT
Bundles of twigs or sticks, often willow, used in building
earthworks or levees (traditional practice in Holland
and China.). Alternate term: fascine
WIND CHOP
See CHOP.
WIND, FOLLOWING
See FOLLOWING WIND.
WIND, KATABATIC
See KATABATIC WIND
WIND, OFFSHORE
A wind blowing seaward from the land in a coastal area.
WIND, ONSHORE
A wind blowing landward from the sea in a coastal area.
WIND, OPPOSING
See OPPOSING WIND.
WIND ROSE
Diagram showing the long-term distribution of wind speed
and direction.
WIND SEA
Wave conditions directly attributable to recent winds,
as opposed to swell.
WIND SETDOWN
Drop in water level below the still water level on the
windward ends of enclosed bodies of water and semi- enclosed
bays.
WIND SETUP
On reservoirs and smaller bodies of water (1) the vertical
rise in the still-water level on the leeward side of a
body of water caused by wind stresses on the surface of
the water; (2) the difference in still-water levels on
the windward and the leeward sides of a body of water
caused by wind stresses on the surface of the water. STORM
SURGE (usually reserved for use on the ocean and large
bodies of water).
WIND STRESS
The way in which wind transfers energy to the sea surface.
WIND TIDE
See WIND SETUP, STORM SURGE.
WIND WAVES
(1) Waves being formed and built up by the wind. (2) Loosely,
any wave generated by wind.
WINDWARD
The direction from which the wind is blowing.
|
|
|
Types of Flowmeters |
|
|
|
|
|
