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Management Measures for Hydromodification - V. GlosssaryAccretion: 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 waterborne or airborne material. Artificial accretion is a similar buildup of land by reason of an act of humans, such as the accretion formed by a groin, breakwater, or beach fill deposited by mechanical means. Also known as aggradation. (USACE, 1984) Alongshore: Parallel to and near the shoreline; longshore (USACE, 1984). Armor unit: A relatively large quarrystone or concrete shape that is selected to fit specified geometric characteristics and density. Armor units are usually uniform in size and usually large enough to require individual placement. In normal cases armor units are used as primary wave protection and are placed in thicknesses of at least two units. (USACE, 1984) Artificial nourishment: The process of replenishing a beach with material (usually sand) obtained from another location (USACE, 1984). 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 (USACE, 1984). 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; 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. (USACE, 1984) 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 (USACE, 1984). Barrier beach: A bar essentially parallel to the shore, the crest of which is above normal high water level (USACE, 1984). Basin, boat: A naturally or artificially enclosed or nearly enclosed harbor area for small craft (USACE, 1984). Bathymetry: The measurement of depths of water in oceans, seas, and lakes; also information derived from such measurements (USACE, 1984). 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 (USACE, 1984). Bayou: A minor sluggish waterway or estuarine creek, tributary to, or connecting, other stream or bodies of water, whose course is usually through lowlands or swamps (USACE, 1984). 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 also shore. (USACE, 1984) Beach planting: The placement of vegetation in the zone of sedimentary material that extends landward from the low water line to the place where there is marked change in material or form, or to the line of permanent vegetation. Beach accretion: See accretion (USACE, 1984). 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. (USACE, 1984) Beach erosion: The carrying away of beach materials by wave action, tidal currents, littoral currents, or wind (USACE, 1984). 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). (USACE, 1984) Beach fill: Material placed on a beach to renourish eroding shores (USACE, 1984). Beach width: The horizontal dimension of the beach measured normal to the shoreline (USACE, 1984). 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. (USACE, 1984) Bluff: A high, steep bank or cliff (USACE, 1984). Bottom: The ground or bed under any body of water; the bottom of the sea (USACE, 1984). 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) (USACE, 1984). Boulder: A rounded rock more than 10 inches in diameter; larger than a cobblestone. See soil classification. (USACE, 1984) Breakwater: 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. (USACE, 1984) 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. (USACE, 1984) 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 humans. (USACE, 1984) Canal: An artificial watercourse cut through a land area for such uses as navigation and irrigation (USACE, 1984). Cape: A relatively extensive land area jutting seaward from a continent or large island that prominently marks a change in, or interrupts notably, the coastal trend; a prominent feature (USACE, 1984). Channel: (1) A natural or artificial waterway or perceptible extent that either periodically or continuously contains moving water, or that 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. (USACE, 1984) Channelization and channel modification: River and stream channel engineering for the purpose of flood control, navigation, drainage improvement, and reduction of channel migration potential; activities include the straightening, widening, deepening, or relocation of existing stream channels, clearing or snagging operations, the excavation of borrow pits, underwater mining, and other practices that change the depth, width, or location of waterways or embayments in coastal areas. Clay: See soil classification (USACE, 1984). Cliff: A high, steep face of rock; a precipice (USACE, 1984). Coast: 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 (USACE, 1984). Coastal area: The land and sea area bordering the shoreline (USACE, 1984). Coastal plain: The plain composed of horizontal or gently sloping strata of clastic materials fronting the coast, and generally representing a strip of sea bottom that has emerged from the sea in recent geologic time (USACE, 1984). 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. (USACE, 1984) Cobble (cobblestone): See soil classification (USACE, 1984). Continental shelf: The zone bordering a continent and extending from the low water line to the depth (usually about 180 meters) where there is a marked or rather steep descent toward a greater depth. Contour: A line on a map or chart representing points of equal elevation with relation to a datum. It is called an isobath when it connects points of equal depth below a datum. Also called depth contour. (USACE, 1984) Controlling depth: The least depth in the navigable parts of a waterway, governing the maximum draft of vessels that can enter (USACE, 1984). 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 plainform or depth; also the decrease in basin width or depth causing such an increase in setup (USACE, 1984). Cove: A small, sheltered recess in a coast, often inside a larger embayment. (USACE, 1984) Current: A flow of water (USACE, 1984). Current, coastal: One of the offshore currents flowing generally parallel to the shoreline in the deeper water beyond and near the surf zone. Such currents are not related genetically to waves and resulting surf, but may be related to tides, winds, or distribution of mass. (USACE, 1984) Current, drift: A broad, shallow, slow-moving ocean or lake current. Opposite of current, stream. (USACE, 1984) Current, ebb: The tidal current away from shore or down a tidal stream. Usually associated with the decrease in the height of the tide. (USACE, 1984) Current, flood: The tidal current toward shore or up a tidal stream. Usually associated with the increase in the height of the tide. (USACE, 1984) Current, littoral: Any current in the littoral zone caused primarily by wave action; e.g., longshore current, rip current. See also current, nearshore. (USACE, 1984) 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 (USACE, 1984). Current, nearshore: A current in the nearshore zone (USACE, 1984). Current, offshore: See offshore current (USACE, 1984). 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. (USACE, 1984) Cutoff: Wall, collar, or other structure, such as a trench, filled with relatively impervious material intended to reduce seepage of water through porous strata; in river hydraulics, the new and shorter channel formed either naturally or artificially when a stream cuts through the neck of a band. 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. (USACE, 1984) Delta: An alluvial deposit, roughly triangular or digitate in shape, formed at a river mouth (USACE, 1984). Depth: The vertical distance from a specified tidal datum to the sea floor (USACE, 1984). Depth of breaking: The still-water depth at the point where the wave breaks (USACE, 1984). Detritus: Loose material worn or broken away from a mass, as by the action of water, usually carried from inland sources by streams (USACE, 1981a). Dike (dyke): A channel stabilization structure sited in a river or stream perpendicular to the bank. Downdrift: The direction of predominant movement of littoral materials (USACE, 1984). 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. (USACE, 1984) Dunes: (1) Ridges or mounds of loose, wind-blown material, usually sand. (2) Bed forms smaller than bars but larger than ripples that are out of phase with any water-surface gravity waves associated with them (USACE, 1984). Ebb tide: The period of tide between high water and the succeeding low water; a falling tide (USACE, 1984). Embankment: An artificial bank such as a mound or dike, generally built to hold back water or to carry a roadway (USACE, 1984). Embayment: An indentation in the shoreline forming an open bay (USACE, 1984). Ephemeral: Lasting for a brief time; short-lived; transitory (Morris, 1978). 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 (USACE, 1984). Estuary: (1) The part of the river that is affected by tides. (2) The region near a river mouth in which the fresh water in the river mixes with the salt water of the sea (USACE, 1984). Eutrophication: The alteration of lake ecology through excessive nutrient input, characterized by excessive growth of aquatic plants and algae and low levels of dissolved oxygen (USEPA, 1992). Fastland: Land near the shoreline that is safely above the erosive zone of waves and tides. The area landward of the bank. Fetch: The area in which seas are generated by a wind having a fairly constant direction and speed. Sometimes used synonymously with fetch length (USACE, 1984). Flood tide: The period of tide between low water and the succeeding high water; a rising tide (USACE, 1984). Flow alteration: A category of hydromodification activities that results in either an increase or a decrease in the usual supply of fresh water to a stream, river, or estuary. 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 back rush of the waves as the tides rise and fall. See beach face. (USACE, 1984) Freeboard: The additional height of a structure above design high-water level to prevent overflow. Also, 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 (USACE, 1984). 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. (USACE, 1984) Gabion: A rectangular basket or mattress made of galvanized, and sometimes PVC-coated, steel wire in a hexagonal mesh. Gabions are generally subdivided into equal-sized cells that are wired together and filled with 4- to 8-inch-diameter stone, forming a large, heavy mass that can be used as a shore-protection device. (USACE, 1990) Generation of waves: (1) The creation of waves by natural or mechanical means. (2) The creation and growth of waves caused by a wind blowing over a water surface for a certain period of time (USACE, 1984). Geomorphology: That branch of both physiography and geology that deals with the form of the Earth, the general configuration of its surface, and the changes that take place in the evolution of landform (USACE, 1984). Grade stabilization structure: A structure used to control the grade and head cutting in natural or artificial channels (USDA-SCS, 1988). Gradient (grade): See slope. 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 (USACE, 1984). Gravel: See soil classification (USACE, 1984). Groin: A shore protection structure built (usually perpendicular to the shoreline) to trap littoral drift or retard erosion of the shore (USACE, 1984). Groin system: A series of groins acting together to protect a section of beach. Commonly called a groin field. (USACE, 1984) Ground water: Subsurface water occupying the zone of saturation. In a strict sense, the term is applied only to water below the water table (USACE, 1984). Habitat: The place where an organism naturally lives or grows. Harbor: Any protected water area affording a place of safety for vessels. See also port. (USACE, 1984) Headland breakwater: A shore-connected breakwater (USACE, 1990). Headland (head): A high, steep-faced promontory extending into the sea (USACE, 1984). Height of wave: See wave height (USACE, 1984). High tide, high water: The maximum elevation reached by each rising tide (USACE, 1984). High water line: 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 (USACE, 1984). 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 meters per second (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 meters per second. (USACE, 1984) Hydrography: (1) A configuration of an underwater surface including its relief, bottom materials, coastal structures, etc. (2) The description and study of seas, lakes, rivers, and other waters (USACE, 1984). Hydrologic modification: The alteration of the natural circulation or distribution of water by the placement of structures or other activities (USEPA, 1992). Hydromodification: Alteration of the hydrologic characteristics of coastal and noncoastal waters, which in turn could cause degradation of water resources. Impoundment: The collection and confinement of water as in a reservoir or dam. 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. (USACE, 1984) Inshore (zone): In beach terminology, the zone of variable width extending from the low water line through the breaker zone. See also shoreface. (USACE, 1984) Jetty: (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. (USACE, 1984) Lagoon: A shallow body of water, like a pond or lake, usually connected to the sea (USACE, 1984). Levee: An embankment or shaped mound for flood control or hurricane protection (USACE, 1981a). Littoral: Of or pertaining to a shore, especially of the sea (USACE, 1984). Littoral current: See current, littoral (USACE, 1984). Littoral drift: The sedimentary material moved in the littoral zone under the influence of waves and currents (USACE, 1984). Littoral transport: The movement of littoral drift in the littoral zone by waves and currents. Includes movement parallel (longshore transport) and perpendicular (on-offshore transport) to the shore (USACE, 1984). Littoral zone: In beach terminology, an indefinite zone extending seaward from the shoreline to just beyond the breaker zone (USACE, 1984). 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. (USACE, 1984) Longshore: Parallel to and near the shoreline; alongshore (USACE, 1984). Longshore current: See current, longshore. Longshore transport rate: Rate of transport of sedimentary material parallel to the shore. Usually expressed in cubic meters (cubic yards) per year. Commonly synonymous with littoral transport rate. (USACE, 1984) Low tide, low water: The minimum elevation reached by each falling tide. See tide. (USACE, 1984) Low water datum: An approximation to the plane of mean low water that has been adopted as a standard reference plane (USACE, 1984). Mangrove: A tropical tree with interlacing prop roots, confined to low-lying brackish areas (USACE, 1984). Marsh: An area of soft, wet, or periodically inundated land, generally treeless and usually characterized by grasses and other low growth (USACE, 1984). Marsh, salt: A marsh periodically flooded by salt water (USACE, 1984). Marsh vegetation: Plants that grow naturally in a marsh. Mean high water: 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 low-water heights are included in the average where the type of field 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 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. (USACE, 1984) Mean tide level: A plane midway between mean high water and mean low water. Not necessarily equal to mean sea level. (USACE, 1984) Meander: A bend in a river. Mud: A fluid-to-plastic mixture of finely divided particles of solid material and water (USACE, 1984). Nearshore (zone): In beach terminology an indefinite zone extending seaward from the shoreline well beyond the breaker zone. It defines the area of nearshore currents. (USACE, 1984) Nearshore current system: The current system that is caused primarily by wave action in and near the breaker zone and consists of four parts: the shoreward mass transport of water; longshore currents; the seaward return flow, including rip currents; and the longshore movement of the expanding heads of rip currents (USACE, 1984). Nourishment: The process of replenishing a beach. It may be brought about naturally by longshore transport or artificially by the deposition of dredged materials. (USACE, 1984) Oceanography: The study of the sea, embracing and indicating all knowledge pertaining to the sea's physical boundaries, the chemistry and physics of seawater, and marine biology (USACE, 1984). Offshore: (1) In beach terminology, the comparatively flat zone of variable width, extending from the breaker zone to the seaward edge of the Continental Shelf. (2) A direction seaward from the shore. (USACE, 1984) Offshore current: (1) Any current in the offshore zone. (2) Any current flowing away from shore. (USACE, 1984) Onshore: A direction landward from the sea (USACE, 1984). Overtopping: Passing of water over the top of a structure as a result of wave runup or surge action (USACE, 1984). Overwash: That portion of the uprush that carries over the crest of a berm or of a structure (USACE, 1984). Oxbow: An isolated lake formed by a bend in a river that becomes disconnected from the river channel. Parapet: A low wall built along the edge of a structure such as a seawall or quay (USACE, 1984). Peninsula: An elongated body of land nearly surrounded by water and connected to a large body of land (USACE, 1984). 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. (USACE, 1984) 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. (USACE, 1984) Pile: A long, heavy timber or section of concrete or metal to be driven or jetted into the earth or seabed to serve as a support or protection (USACE, 1984). Pile, sheet: A pile with a generally slender flat cross section to be driven into the ground or seabed and meshed or interlocked with like members to form a diaphragm, wall, or bulkhead (USACE, 1984). Piling: A group of piles (USACE, 1984). Plain, coastal: See coastal plain (USACE, 1984). Plainform: The outline or shape of a body of water as determined by the stillwater line (USACE, 1984). Point: The extreme end of a cape; the outer end of any land area protruding into the water, usually less prominent than a cape (USACE, 1984). 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 quays, wharves, facilities for transfer of cargo, docks, and repair shops are situated (USACE, 1984). Preexisting: Existing before a specified time or event (Morris, 1978). Profile, beach: The intersection of the ground surface with a vertical plane; may extend from the top of the dune line to the seaward limit of sand movement (USACE, 1984). Quarrystone: Any stone processed from a quarry (USACE, 1984). Recession (of a beach): (1) A continuing landward movement of the shoreline. (2) A net landward movement of the shoreline over a specified time (USACE, 1984). 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 (USACE, 1984). 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 alignment with the underwater contours. (2) The bending of wave crests by currents. (USACE, 1984) Retreat: To move in a landward direction away from an eroding streambank or shoreline. Revetment: A facing of stone, concrete, etc., built to protect a scarp, embankment, or shore structure against erosion by wave action or currents (USACE, 1984). Riparian: Pertaining to the banks of a body of water (USACE, 1984). Riparian area: Vegetated ecosystems along a waterbody through which energy, materials, and water pass. Riparian areas characteristically have a high water table and are subject to periodic flooding and influence from the adjacent waterbody. These systems encompass wetlands, uplands, or some combination of these two land forms; they will not in all cases have all of the characteristics necessary for them to be classified as wetlands. (Mitsch and Gosselink, 1986; Lowrance et al., 1988) 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 of 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. Rubble: (1) Loose, angular, waterworn stones along a beach. (2) Rough, irregular fragments of broken rock. (USACE, 1984) Rubble-mound structure: A mound of randomly-shaped and randomly-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.) (USACE, 1984) Run-of-the-river dam: Usually a low dam with small hydraulic head, limited storage area, short detention time, and no positive control over lake storage. Runup: The rush of water up a structure or beach on the breaking of a wave. Also uprush, swash. The amount of runup is the vertical height above still-water level to which the rush of water reaches. (USACE, 1984) Salt marsh: A marsh periodically flooded by salt water (USACE, 1984). Sand: See soil classification (USACE, 1984). Sandbar: (1) See bar. (2) In a river, a ridge of sand built up to or near the surface by river currents. (USACE, 1984) Sand bypassing: See bypassing, sand (USACE, 1984). Scour: Removal of underwater material by waves and currents, especially at the base or toe of a shore structure (USACE, 1984). Seawall: A structure separating land and water areas, primarily designed to prevent erosion and other damage due to wave action (USACE, 1984). Shoal (noun): A detached elevation of the sea bottom, composed of any material except rock or coral, which may endanger surface navigation (USACE, 1984). Shoal (verb): (1) To become shallow gradually. (2) To cause to become shallow. (3) To proceed from a greater to a lesser depth of water. (USACE, 1984) 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. (USACE, 1984) 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 (USACE, 1984). 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 shore or beach). The line delineating the shoreline on National Ocean Service nautical charts and surveys approximates the mean high water line. (USACE, 1984) Silt: See soil classification (USACE, 1984). Slip: A berthing space between two piers (USACE, 2984). Slope: The degree of inclination to the horizontal. Usually expressed as a ratio, such as 1:25 or 1 on 25, indicating 1 unit vertical rise in 25 units of horizontal distance, or in a decimal fraction (0.04); degrees (2ø 18 ), or percent (4 percent). (USACE, 1984) 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 (USACE, 1984). Spit: A small point of land or a narrow shoal projecting into a body of water from the shore (USACE, 1984). Splash zone: Area along the shoreline above the zone of influence of waves and tides that is still wetted by the spray from breaking waves. Storage dam: Typically a high dam with large hydraulic head, long detention time, and positive control over the volume of water released from the impoundment. 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. (USACE, 1984) 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." (USACE, 1984) Tailwater: Channel or stream below a dam (Walberg et al., 1981). Tidal flats: Marshy or muddy land areas that are covered and uncovered by the rise and fall of the tide (USACE, 1984). Tidal inlet: (1) A natural inlet maintained by tidal flow. (2) Loosely, an inlet in which the tide ebbs and flows. Also tidal outlet. (USACE, 1984) Tidal period: The interval of time between two consecutive, like phases of the tide (USACE, 1984). Tidal range: The difference in height between consecutive high and low (or higher high and lower low) waters (USACE, 1984). 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. (USACE, 1984) Topography: The configuration of a surface, including its relief and the positions of its streams, roads, building, etc. (USACE, 1984). Tropical storm: A tropical cyclone with maximum winds of less than 34 meters per second (75 miles per hour). Compare hurricane. (USACE, 1984) Updrift: The direction opposite that of the predominant movement of littoral materials (USACE, 1984). Upland: Ground elevated above the lowlands along rivers or between hills (Merriam-Webster, 1991). 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.) (USACE, 1984) Wave: A ridge, deformation, or undulation of the surface of a liquid (USACE, 1984). Wave height: The vertical distance between a crest and the preceding trough (USACE, 1984). Wave period: The time required for a wave crest to traverse a distance equal to one wavelength. The time required for two successive wave crests to pass a fixed point. (USACE, 1984) 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 (USACE, 1984). Wetlands: Those areas that are inundated or saturated by surface water or ground water at a frequency and duration to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions; wetlands generally include swamps, marshes, bogs, and similar areas. (This definition is consistent with the Federal definition at 40 CFR 230.3, promulgated December 24, 1980. As amendments are made to the wetland definition, they will be considered applicable to this guidance.) Wind waves: (1) Waves being formed and built up by the wind. (2) Loosely, any waves generated by wind. (USACE, 1984) Return to the Table of Contents
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