Glossary of Coastal Terminology: H - M

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H

HABITAT: The place where an organism lives.

HALF-TIDE LEVEL: A plane midway between MEAN HIGH WATER and MEAN LOW WATER, also called MEAN TIDE LEVEL.

HALCOCLINE: A zone in which SALINITY changes rapidly.

HARBOR: A water area nearly surrounded by land, SEAWALLS, BREAKWATERS, or artificial DIKES, forming a safe anchorage for ships.

HARD DEFENSES: A general term applied to impermeable COASTAL DEFENSE structures of concrete, timber, steel, masonry, etc, which reflect a high proportion of INCIDENT WAVE energy.

HEAD: (1) A comparatively high PROMONTORY with either a CLIFF or steep face. It extends into a large 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.

HEADLAND: A land mass having a considerable ELEVATION. See Figure 13.

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.

HEAVY SEA: A SEA in which the WAVES run high.

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 HIGHER HIGH WATER. See Figure 11.

HIGHER LOW WATER (HLW): The higher of the two low waters of any TIDAL DAY. See Figure 11.

HIGH SEAS: This term, in municipal and international law, denotes all that 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, also called OPEN SEA.

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: The intersection of MEAN HIGH WATER with the SHORE. The SHORELINE delineated on the nautical charts of the U.S. Coast and Geodetic Survey is an approximation of the mean high water line.

HIGH WATER MARK: A reference mark on a structure or natural object, indicating the maximum stage of TIDE or flood.

HINDCASTING: In WAVE prediction, the retrospective forecasting of WAVES using measured wind information. See also WAVE HINDCASTING.

HINTERLAND: The region lying inland from the COAST.

HISTORIC EVENT ANALYSIS: Extreme analysis based on HINDCASTING typically ten EVENTS over a period of 100 years.

HOOK: A SPIT or narrow CAPE, turned landward at the outer end, resembling a hook in form.

HORIZON: (1) The line or circle which forms the apparent boundary between Earth and sky. (2) (Geological) A plane in rock strata characterized by particular features, as occurrence of distinctive fossil species. One of the series of distinctive layers found in a vertical cross-section of any well-developed SOIL.

HURRICANE: A cyclonic storm, usually of tropic origin, covering an extensive area, and containing winds in excess of 75 miles per hour.

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.


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I

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.


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J

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.


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K

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.


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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. 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.

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 CURRENT: A current located in the SURF ZONE, moving generally parallel to the SHORELINE, generated by WAVES breaking at an angle with the SHORELINE, also called the ALONGSHORE CURRENT. See also NEARSHORE CURRENT SYSTEM). See Figure 6.

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.

LONG WAVES: WAVES with periods above about 30 seconds; can be generated by WAVE GROUPS breaking in the SURF ZONE. See also INFRAGRAVITY WAVES.

LOOP: That part of a STANDING WAVE where the vertical motion is greatest and the horizontal velocities are least.

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.

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.

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.


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M

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.

MARKER, SURVEY: An object placed at the site of a station to identify the surveyed location of that station.

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).

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.

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 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 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 determined, mean high water in the latter case is the same as MEAN HIGHER HIGH WATER.

MEAN HIGH WATER SPRINGS (MHWS): The average height of the HIGH WATER occurring at the time of 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 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 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.

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.

MID-EXTREME TIDE: A plane midway between the extreme HIGH WATER and the extreme LOW WATER occurring in any locality.

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 morphologies 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.


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Ecology - SEA Program | USGS - Coastal & Marine Geology

This is http://www.ecy.wa.gov/programs/sea/swces/products/glossary/H_M.htm
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Address questions and comments to George Kaminsky
Modified 22 Mar 2012