Beach Nourishment - Coastal Geology

Beach Nourishment: A Guide for Local Government Officials

Glossary

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

A

Active profile zone - The nearshore zone across which the dominant sediment motion occurs.

B

Barrier island - A sand body that is essentially parallel to the shore, the crest of which is above normal high water level.

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.

Beach profile - The intersection of the ground surface with a vertical plane; may extend from behind the dune line or the top of a bluff to seaward of the breaker zone.

Beach renourishment - Pumping sand onto the beach and building up former dunes and upper beach after construction of an initial nourishment.

Benthic community - Organisms that live on the sub-aquatic bottom.

Biogenically derived sediments - Biogenous sediments consist of the remains of either marine plant or animal skeletons, either coarse grained as found in shallow coastal waters, or fine grained as found in deeper waters.

Borrow site - A term used to describe the site identified for, or remaining after, borrow material has been removed for placement onto a beach. In upland areas, the site frequently becomes a body of water. In marine areas, the site becomes a hole in a bay or nearshore area.

C

Carbonate platform - A large and thick accumulation of carbonate strata that it typically isolated from other land masses.

Carbonate sediments - Sediment formed by the organic or inorganic precipitation from aqueous solution of carbonates of calcium, magnesium, or iron.

Closure depth - The depth of water beyond which sediments are not normally affected by waves.

Coastal geology - Origin, structure, and characteristics of the sediments that make up the coastal region, from the uplands to the nearshore region. Sediments can vary from small particles of silt or sand to larger particles of gravel and cobble, to formations of consolidated sediments and rock.

Coastal plain - A broad, low relief region 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.

Coastal sediment budget - The identification of sediment sources and sinks, and the quantification of the amounts and rates of sediment transport, erosion, and deposition within a defined region.

Compatibility analysis - Methods used to evaluate the suitability of the sediments in a borrow area for beach nourishment purposes based on the characteristics of the native beach material and / or the profile shape of the constructed beach.

Continental shelf - 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.

Cross-shore direction - Perpendicular to the shoreline.

Cross-shore transport - A wave and / or tide-generated movement of shallow-water coastal sediments toward or away from the shoreline.

D

Drowned barrier island - A long, narrow coastal sandy body, representing a broadened barrier beach that was above high tide and parallel to the shore in prior sea level conditions and is now underwater.

Dune - A ridge or mound of loose, wind-blown material, usually sand.

E

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.

Equilibrium beach profile - The slightly concave slope of the floor of a sea or lake, taken in a vertical plane and extending away from and transverse to the shoreline, being steepest near the shore, and having a gradient such that the amount of sediment deposited by waves and currents is balanced by the amount removed by them; the transverse slope of a graded shoreline. The profile is easily disturbed by strong winds, large waves, and exceptional high tides.

Erosion cold spot - Beach segment that is accretional, often due to a convergence of refracted wave energy or where submerged features dissipate wave energy and result in sediment gains.

Estuary - (1) A coastal embayment where there is freshwater input that is influenced by tides. (2) The part of a river that is affected by tides. (3) The region near a river mouth in which the fresh water of the river mixes with the salt water of the sea.

F

Flood tidal-delta - The bulge of sand formed at the landward mouth of tidal inlets as a result of flow expansion.

G

Gross sediment transport - The sum of the sediment transport magnitudes in the dominant and secondary directions. The gross sediment transport does not have a direction or sign.

H

Hot spot - Shoreline segment characterized by erosion rates that are significantly greater than adjacent shoreline segments.

Hydraulic sand placement - Sediment (sand) moved using water and centrifugal pumps mounted on a barge or large seagoing vessel (hydraulic dredging), usually moving sediment originating from an offshore site.

Hydrographic surveys - 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.

I

Inlet improvement - Modifications to an existing inlet, usually for purposes of navigation, which may include channel deepening and/or jetty construction. Other reasons for inlet improvement may include positional stabilization and improved flushing of the bay served by the inlet.

Inlet positional stability - A type of stability related to the orientation of the inlet's tidal jet.

Intertidal Zone - The zone between spring high tide and spring low tide.

J

Jet-probe - A long pipe into which water under high pressure is pumped in order to penetrate into unconsolidated sediment.

L

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 from passing into the next.

Littoral zone - In beach terminology, an indefinite zone extending seaward from the shoreline to just beyond the breaker zone.

Longshore bar - A sand bar that extends roughly parallel to the shoreline.

Longshore direction - Parallel to and near the shoreline, alongshore.

Longshore sand bars - 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 transport - A wave- and/or tide-generated movement of shallow-water coastal sediments parallel to the shoreline.

Low energy environments - Coastlines where wave and tidal forces are typically relatively small due to the climate, the location of the site and / or due to nearshore submerged features that function to reduce incoming wave energy.

M

Magnetometer survey - A geophysical test to determine the ferrous returns for subsurface materials such as shipwrecks, debris and other anomalies located within a borrow site. Such materials must be located to avoid damage to dredge equipment or to determine the precise location of historic relics, shipwrecks, or other artifacts.

Marsh - An area of soft, wet, or periodically inundated land, generally treeless and characterized by grasses.

Miocene Epoch - The period of geologic time that extends from 24 million years to 5 million years before the present.

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.

N

Nearshore - In beach terminology, an indefinite zone extending seaward from the shoreline well beyond the breaker zone.

Nearshore zone - In beach terminology, the zone that extends seaward from the low tide line including the bar and trough topography that commonly extends well beyond the breaker zone.

Net sediment transport - The difference between the sediment transport magnitude in the dominant direction and the transport magnitude in the secondary direction. Sediment transport is usually considered to be positive to the right as an observer looks seaward. The net sediment transport can be positive, negative, or zero.

O

Oblique sand ridge - A generic name for any low ridge of sand formed at some distance from the shore, either submerged or emergent at an angle to the shoreline.

P

Planform - The outline or shape of a body of water as determined by the still-water line, that is, a map.

Planform evolution - The morphodynamic changes that take place over time on a particular geographic entity.

Profile equilibration - The process of adjustment of a beach profile from one shape to one which is in more of an equilibrium condition with the waves and tides. Occurs after placement of nourishment materials at a slope steeper than equilibrium.

Q

Quartz sediment - Sediment formed by solid fragmental material that originates from the weathering of quartz rocks and comprises most sediment along the Atlantic Coast.

R

Reconnaissance level sand source investigations - Broad scale field investigation to provide sediment stratagraphy and particle size information to identify prospective candidate sand source and to provide information for the preparation of preliminary project design and cost estimates.

Regional sand management - Management of sediment resources based on broad geographic considerations.

Relict - Remnant left after decay, disintegration, or disappearance.

S

Sediment budget - The mass balance between inputs and outputs of sediment within a defined coastal environment.

Sediment characteristics - Physical attributes of a sediment sample measured by the statisitical variations in particle size, chemical composition, density, moisture content, and color. Sediment is a solid fragmental material that originates from weathering of rocks and is transported or deposited by air, water, or ice, or that accumulates by other natural agents, such as chemical precipitation from solution or secretion by organisms (biological origin), and that forms in layers on the Earth's crust or surface at ordinary temperatures in a loose, unconsolidated form (for example, sand, gravel, silt, mud).

Sediment composites - A particle size distribution that represents the overall average of all sediment strata within a borrow site, usually based on multiple sediment grain size distributions weighted accordingly.

Sediment pathways - The routes along which sediment movement occurs.

Shore-parallel structures - Structures that are constructed onshore and parallel to the beach, including seawalls and revetments designed to protect the land and buildings located immediately landward. Shore-parallel structures also include breakwaters and submerged sills located in nearshore waters which act to intercept and reduce the energy of approaching waves.

Shore-perpendicular structures - Structures such as groins and jetties that are constructed perpendicular to the beach and extend out into the water. These types of structures are designed to retard or interrupt the longshore movement of sand and accumulate sand on the beach updrift of the structure.

Shoreline stabilization - Measures to retard erosion to protect upland property. Recognized erosion control measures include seawalls, revetments, jetties, groins, breakwaters, and beach nourishment.

Siliciclastic sediment - Sediment that is composed primarily of fragments of silicate minerals or rock fragments, most commonly quartz.

Stillstand (sea level) - A period of time (centuries or millennia) during which there is little or no change in sea level.

Storm tide - 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.

T

Tidal delta - An alluvial deposit, usually triangular or semi-circular, at the mouth of a tidal inlet that accumulates as the result of the combination of wave processes and tidal currents.

Tidal flat - Unvegetated sandy or muddy land area that is covered and uncovered by the rise and fall of the tide.

Tombolo - A bar or spit of sand that connects or "ties" an island to the mainland or to another island.

Trough sand accumulation - Where sand accumulates in a long and broad bathymetric low between adjacent sand bars or reefs.

W

Washover fan - Sediment deposited inland of a beach by overwash processes associated with storms where elevated water level and large waves transport sediment across the beach.

Wetland - Land 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.

Coastal Services Center

National Oceanic and Atmospheric Administration

Glossary

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