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

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.

Impermeable groin
A GROIN through which sand can not pass.

Incident wave
Wave moving landward.

Infragravity waves
Waves with periods above about 30 seconds generated by wave groups breaking in the surf zone. See LONG WAVES.

Inlet
(1) A narrow strip of water running into the land or between islands. (2) An arm of the sea (or other body of water) that is long compared to its width, and that may extend a considerable distance inland.

Inlet gorge
Generally, the deepest region of an INLET.

Inshore
(1) The region where waves are transformed by interaction with the sea bed. (2) In beach terminology, the zone of variable width extending from the LOW WATER LINE through the BREAKER ZONE.

Inshore current
Any current inside the SURF ZONE.

Intertidal
The zone between the high and LOW WATER marks.

Irregular waves
Waves with random wave periods (and in practice, also heights), which are typical for natural wind-induced waves.

Isobath
Line connecting points of equal water DEPTH on a chart; a seabed contour.

Isostasy
The tendency of the Earth`s crust to maintain a state of near equilibrium, i.e., if anything occurs to modify the existing state, a compensation change will occur to maintain a balance.

Isotope
An atom with a specified number of protons and a specified number of neutrons.

Jetty
(1) On open seacoasts, a structure extending into a body of water to direct and confine the stream or tidal flow to a selected CHANNEL, or to prevent shoaling. Jetties are built at the mouth of a river or ENTRANCE to a BAY to help deepen and stabilize a CHANNEL and facilitate navigation. (2) (SMP) A structure usually projecting out into the SEA at the mouth of a river for the purpose of protecting a navigational channel, a harbor or to influence water currents.

Key
A low, insular BANK of sand, coral, etc., as one of the islets off the southern coast of Florida.

Knot
The unit of speed used in navigation. It is equal to one nautical mile (6076.115 feet or 1852 meters) per hour.

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. See DAILY RETARDATION OF TIDES.

Lagoon
A shallow body of water, as a pond or lake, which usually has a shallow restricted INLET from the sea. See Figure 5.

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.

Landlocked
Enclosed by land, or nearly enclosed, as a HARBOR.

Landmark
A conspicious object, natural or man-made, located near or on land, which aids in fixing the position of an observer.

Leadline
A line, wire or cord used in sounding. It is weighted at one end with a plummet (sounding lead). See also SOUNDING LINE.

Ledge
A rocky formation continuous with and fringing the shore.

Leeward
The direction toward which the prevailing wind is blowing; the direction toward which waves are travelling.

Levee
(1) An EMBANKMENT to prevent inundation. (2) (SMP) A large DIKE or 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 nautical miles per hour.

Limit of backwash
The seaward limit of the BACKWASH at any given tide stage.

Limit of uprush
The landward limit of UPRUSH at any given tide stage.

Littoral
(1) Of, or pertaining to, a shore, especially a seashore. (2) (SMP) Living on, or occurring on, the SHORE.

Littoral currents
A current running parallel to the BEACH and generally caused by waves striking the shore at an angle.

Littoral deposits
Deposits of LITTORAL DRIFT.

Littoral drift
(1) The sedimentary material moved in the LITTORAL ZONE under the influence of waves and currents. (2) (SMP) The mud, SAND, or GRAVEL material moved parallel to the SHORELINE in the NEARSHORE ZONE by waves and CURRENTS.

Littoral transport
The movement of LITTORAL DRIFT 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
The rate of transport of sedimentary material parallel to or perpendicular to the shore in the LITTORAL ZONE. Usually expressed in cubic meters (yards) per year. Commonly used as synonymous with LONGSHORE TRANSPORT RATE.

Littoral zone
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 in the water, and the bedload of large particles that move along the bottom.

Locally generated waves
Waves generated within the immediate vicinity, within approximately 50 km, of the point of interest.

Long waves
Waves with periods above about 30 seconds; can be generated by wave groups breaking in the surf zone. See also INFRAGRAVITY WAVES.

Longcrested waves
A wave, the crest length of which is long compared to the wave length.

Longshore
Parallel and close to the COASTLINE.

Longshore bar
A sand ridge or ridges, 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 drift
Movement of sediments approximately parallel to the COASTLINE.

Longshore transport rate
Rate of transport of sedimentary material parallel to the shore. Usually expressed in cubic meters (yards) per year. Commonly used as synonymous with 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.

Low tide
See LOW WATER

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 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.

Lower High Water (LHW)
The lower of the two high waters of any tidal day. See Figure 11.

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 LLW. See Figure 11.

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. See Figure 11.

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.

Macro-tidal
Tidal range greater than 4 m.

Managed retreat
The deliberate setting back of the existing line of defense in order to obtain engineering and/or environmental advantages.

Margin, continental
A zone separating a continent from the deep-sea bottom.

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) (SMP) 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. See Figure 7.

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 high water (MHW)
The average ELEVATION of all high waters recorded at a particular point or station over a considerable period of time, usually 19 years. 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. 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 d…

Mean high water springs (MHWS)
The average height of the high water occurring at the time of spring tides.

Mean higher high water (MHHW)
The arithmetic average of the elevations of the higher high waters of a mixed tide over a specific 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 interval.

Mean low water (MLW)
The average height of the low 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 springs (MLWS)
The average height of the low waters occurring at the time of the spring tides.

Mean lower low water (MLLW)
The average height of the lower low 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 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 (see sea level datums).

Mean steepness
The ratio of the MEAN DEPTH to the horizontal distance over which the MEAN DEPTH was determined.

Mean tide level
Same as 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 period
The mean of all individual waves in an observation interval of approximately half an hour.

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.

Middleground 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 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. See also MIXED TIDE.

Mixed tide
Type of tide which the presence of a DIURNAL wave is conspicious 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.

Mole
In coastal terminology, a massive solid-filled structure (generally revetted) of earth, masonry or large stone.

Monochromatic waves
A series of waves generated in a laboratory, each of which has the same length and period.

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 morph-ologies and sequences of change.

Morphology
River/ESTUARY/lake/seabed form and its change with time.

Mud flat
A muddy, low-lying strip of ground by the shore, or an island, usually submerged more or less completely by the rise of the tide.

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.

Nautical mile
Also known as GEOGRAPHICAL MILE, its length is 1852 meters (6076.115 feet), approximately 1.15 times as long as the statute mile of 5280 feet.

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.