Glossary of Coastal Terminology: U - Z

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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 undertow are actually RIP CURRENTS.

UNDERWATER GRADIENT: The SLOPE of the sea bottom. See SLOPE.

UNDISTURBED WATER LEVEL: Same as STILL WATER LEVEL.

UPDRIFT: The direction to which the predominant LONGSHORE movement of BEACH material approaches.

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

UPRUSH: The rush of water up the FORESHORE following the breaking of a WAVE, also called SWASH or RUN-UP.

UPWELLING: The process by which water rises from a deeper to a shallower DEPTH, usually as a result of OFFSHORE surface water flow. It is most prominent where persistent wind blows parallel to a COASTLINE so that the resultant EKMAN TRANSPORT moves surface water away from the COAST. See Figure 5.


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V

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

VARIABILITY OF WAVES: (1) The variation of heights and periods between individual WAVES within a WAVE TRAIN. (2) The variation in direction of propagation of WAVES leaving the GENERATING AREA. (3) The variation in height along the crest, usually called "variation along the WAVE".

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

VISCOSITY: Resistance to flow.


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W

WATER DEPTH: Distance between the seabed and the STILL WATER LEVEL.

WATER LEVEL: The ELEVATION of a particular point or small patch on the surface of a body of water above a specific point or surface, averaged over a period of time sufficiently long to remove the effects of short period disturbances.

WATER LINE: (1) The juncture of land and SEA. This line migrates, changing with the TIDE or other variation of the WATER LEVEL. Where WAVES are present on the BEACH, this line is also known as the LIMIT OF BACKRUSH. (2) The common boundary between the water surface and any immersed structure.

WATER MARK: A line or mark left on the SHORES of a body of water by the water as an indication of the water's former ELEVATION.

WATER, NAVIGABLE: The waters which are or can be used as water highways for commerce.

WATER TABLE: The upper surface of a zone of saturation, where the body of groundwater is not confined by an overlying impermeable formation. Where an overlying confining formation exists, the AQUIFER in question has no water table.

WATER TYPE: A water having well-defined temperature, SALINITY and nutrient characteristics.

WAVE: (1) An oscillatory movement in a body of water manifested by an alternate rise and fall of the surface. (2) A disturbance of the surface of a liquid body, as the OCEAN, in the form of a ridge, SWELL or hump. (3) The term wave by itself usually refers to the term SURFACE GRAVITY WAVE (PROGRESSIVE). See also CAPILLARY WAVE, GRAVITY WAVE, PROGRESSIVE WAVE, STANDING WAVE, TIDE WAVE, TSUNAMI. See Figure 10.

WAVE AGE: The ratio of WAVE VELOCITY to wind velocity.

WAVE BASE: The plane or DEPTH to which WAVES may erode the bottom in SHALLOW WATER.

WAVE CLIMATE: Average condition of the WAVES at a place, over a period of years, as shown by height, period, direction, etc.

WAVE CLIMATE ATLAS: Series of maps showing the variability of WAVE conditions over a long COASTLINE.

WAVE CREST: (1) The highest part of the WAVE. (2) That part of the WAVE above STILL WATER LEVEL.

WAVE-CUT PLATFORM: A horizontal bench of rock formed beneath the SURF ZONE as a COAST retreats because of wave erosion.

WAVE DELTA: See DELTA.

WAVE DIRECTION: The direction from which the WAVES are coming.

WAVE DRIFT: The small net forward displacement of water in the direction of the WAVE travel, particularly in WAVES of large AMPLITUDE, so that the orbits are not quite closed, and the water, while in the crests, moves slightly further forward than it moves backward while in the TROUGHS. See also MASS TRANSPORT, SHOREWARD.

WAVE GENERATION: Growth of WAVE energy by wind.

WAVE GROUP: A series of WAVES in which the distance between crests, and the AMPLITUDE, vary only slightly.

WAVE HEIGHT: The vertical distance between the crest (the high point of a WAVE) and the TROUGH (the low point). See Figure 12.

WAVE HINDCAST: The calculation from historic synoptic weather charts of the WAVE characteristics that probably occurred at some past time.

WAVE HOLLOW: See WAVE TROUGH.

WAVE LENGTH: The distance, in meters, between equivalent points (CRESTS or TROUGHS) on WAVES. See Figure 12.

WAVE PERIOD: (1) The time required for two successive WAVE CRESTS to pass a fixed point. (2) The time, in seconds, required for a WAVE CREST to traverse a distance equal to one WAVE LENGTH.

WAVE PROPAGATION: The transmission of WAVES through water.

WAVE RECORDER: A meter which records either the surface time history of GRAVITY WAVES, or the subsurface pressure time history due to these WAVES.

WAVE REFRACTION: See REFRACTION.

WAVE ROSE: Diagram showing the long-term distribution of WAVE HEIGHT and DIRECTION.

WAVE SET-UP: ELEVATION of the still-water level due to breaking WAVES.

WAVE STAFF: An instrument consisting of a graduated vertical pole for measuring WAVE HEIGHTS, and, by introducing a timing device, WAVE PERIODS. The staff may support a strip or series of electrical contacts for activating a recorder.

WAVE STEEPNESS: The ratio of WAVE HEIGHT to its length. Not the same thing as the SLOPE between a WAVE CREST and its adjacent TROUGH. See Figure 12.

WAVE TRAIN: A series of WAVES from the same direction.

WAVE TRANSFORMATION: Change in WAVE energy due to the action of physical processes.

WAVE TROUGH: The lowest part of the WAVE form between CRESTS. Also that part of a WAVE below STILL WATER LEVEL. See Figure 12.

WAVE VARIABILITY: (1) The variation of heights and periods between individual WAVES within a WAVE TRAIN. WAVE TRAINS are not composed of WAVES of equal heights and periods, but rather of heights and periods which vary in a statistical manner. (2) The variability in direction of WAVE travel when leaving the GENERATING AREA. (3) The variation in height along the crest.

WAVE VELOCITY: Speed at which the individual WAVE form advances, defined as the WAVE LENGTH divided by the WAVE PERIOD (in meters per second). See CELERITY. See Figure 14.

WAVE WASH: The erosive action on SHORES or EMBANKMENTS caused by the lapping or breaking of WAVES.

WEATHER SHORE: The land lying in the direction from which the wind is coming. The WINDWARD side.

WEIR: A low DAM or wall across a STREAM to raise the upstream WATER LEVEL. Termed fixed crest weir when uncontrolled.

WELL: A hole, generally cylindrical and usually walled or lined with pipe, that is dug or drilled into the ground to penetrate an AQUIFER below the zone of saturation.

WELL MIXED ESTUARY: In this circulation type, tidal fluctuations dominate, and the water column is mixed vertically.

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.

WHITECAP: The white froth on CRESTS of WAVES in a wind (caused by the wind blowing the crest forward and over).

WIND CURRENT: A current created by the action of the wind. From theoretical considerations, currents produced by winds in the OPEN SEA will set to the right of the direction towards which the wind is blowing if in the Northern Hemisphere and to the left of this direction if in the Southern Hemisphere.

WIND RIPPLE: Small, low ridge of SAND produced by the SALTATION of windblown SAND.

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 SETUP: (1) The vertical rise in the STILLWATER LEVEL on the LEEWARD side of a body of water caused by WIND STRESSES on the surface of the water. (2) The difference in STILLWATER LEVES on the WINDWARD and the LEEWARD sides of a body of water caused by WIND STRESSES on the surface of the water. (3) synonymous with WIND TIDE and STORM SURGE. STORM SURGE is usually reserved for use on the OCEAN and large bodies of water. Wind setup is usually reserved for use on reservoirs and smaller bodies of water.

WIND STRESS: The way in which wind transfers energy to the SEA surface.

WIND TIDE: The deviation from a still-water level surface ELEVATION caused by the transport of surface water by winds.

WINDWARD: The direction from which the wind is blowing.

WIND WAVES: (1) WAVES formed and growing in height under the influence of wind. (2) Loosely, any WAVE generated by wind. See Figure 10.

WITNESS MARK: A material mark placed at a known distance and direction from a property corner, an instrument station or a survey station, as an aid in its recovery and identification.

WITNESS POST: See WITNESS MARK.


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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Ecology - SEA Program | USGS - Coastal & Marine Geology

This is http://www.ecy.wa.gov/programs/sea/swces/products/glossary/U_Z.htm
Maintained by CMAP, Washington Department of Ecology
Address questions and comments to George Kaminsky
Modified 22 Mar 2012