Tidal Inlet Terminology
A
Accretion - Accumulation of sand due to natural action of waves, currents and wind. A buildup of the beach or dune.
Alongshore - Parallel to and near the shoreline.
B
Backshore – The part of the shoreline between the berm crest and the toe of the dunes or beach cliff. The backshore is often wider than the foreshore and slopes landward. Waves only reach the backshore during storms.
Bar - Fully or partly submerged mound of sand, built on the bottom in shallow water by waves and currents.
Barrier Island - A long, narrow, sandy island, representing a beach that is above high tide and parallel to the shore, commonly including dunes, grasslands with shrub zones, and marshes within the lagoon.
Barrier Spit – A narrow beach connected to the mainland or to a barrier island at one end, usually composed of sand deposited by the alongshore current.
Bathymetry - The science of measuring ocean depths and charting the topography of the ocean floor.
Beach - A mobile deposit of sand extending from the toe of the dunes, from approximately 6 to 10 feet above mean sea level, seaward to water depths of minus-25 to minus-30 feet. The shapes of both the above- and below-water portions constantly adjust due to changing energy conditions.
Beachfill - Sand placed on a beach by mechanical methods.
Berm - A nearly horizontal part of the beach formed at or above the high-water line by waves depositing material. Some beaches have no berms; others have one or several.
Breakwater - Artificial or natural structure aligned parallel to the shoreline, sometimes shore-connected, that provides protection from waves.
C
Channel margin linear bars - Levee-like sand deposits built by the interaction of the ebb-tidal and flood-tidal currents with wave-generated currents. These bars flank the ebb channel.
Current, Longshore - Current in the breaker zone moving essentially parallel to shore, usually caused by waves breaking at an angle to shore. Also called alongshore current.
D
Downdrift - Direction of net alongshore movement of littoral or sedimentary materials.
E
Ebb channel - The main and deeper tidal channel dominated by ebb-tidal currents (outgoing tide). Usually the channel is positioned closer to one of the adjacent barrier islands and its seaward extension is oriented at an angle to the adjacent shoreline. The seaward extension of the ebb channel is termed the outer-bar channel.
Ebb Shield – A high rim around the flood-tidal delta, protecting it from currents.
Ebb surge – The storm surge flowing from the sound to the ocean, typically caused by a hurricane moving inland or an inland hurricane moving offshore. The seaward-directed flow usually occupies low areas along the barriers and often results in development of inlets and temporary sluices or water channels in the islands’ surface. The return flow commonly enlarges existing inlets by eroding the adjacent shorelines. Sediments eroded from the island and inlets are deposited offshore some distance from land.
Ebb-tidal delta - A deposit of sand just seaward of a tidal inlet posing a hazard to navigation, but often protecting adjacent beaches from severe erosion through its breakwater effect.
Ebb-tidal delta breaching – the repositioning of the main channel across the ebb-tidal delta and the resulting movement of large sandbars to the landward regions of the shoals and the adjacent shorelines.
Equilibrium - State of balance of opposing forces.
Erosion - The wearing away of land by natural forces such as waves and wind.
F
Flood-tidal delta - A body of sediment sand found landward of a tidal inlet. Many marshes are formed on old flood-tidal delta deposits.
Flood ramp - Sloping sand on the flood-tidal delta where the incoming flood-tidal current diverges into several distinct flows.
Foreshore - The part of the shoreline between the crest of the seaward berm, or upper limit of wave wash, and the low-water line. The foreshore is ordinarily traversed by the run-up and backwash of the waves.
G
Groin - A low, narrow jetty-like feature constructed of a variety of materials, usually extending roughly perpendicular to the shoreline, designed to protect the beach from erosion or to trap sand for the purpose of building up a beach.
H
High tide - Maximum still-water level reached by the rising tide, not including wave run-up.
High-water line - Intersection of the level of mean high water with the shoreline. Shorelines on navigation charts are approximations of the high-water line.
I
Inlet - A short, narrow waterway between islands, connecting a lagoon with the sea. Provides an exchange of water, nutrients and sediment.
Intertidal zone - Land area alternately inundated and uncovered by tides. Usually considered to extend from the mean low-water line to the mean high-water line.
J
Jetty – A sxstructure extending into the ocean near an inlet, designed to prevent littoral materials from shoaling the inlet. Built to deepen and stabilize an inlet.
L
Lee - Sheltered part facing away from waves.
Littoral drift - Sedimentary material moved along the shoreline under the influence of waves and currents. Same as alongshore or longshore drift.
Littoral transport - Movement of sediment along the shoreline by waves and currents.
Longshore - Parallel to and near the shoreline.
Longshore transport rate - Rate of movement of littoral material parallel to shore. Expressed in cubic yards per year or cubic meters per year.
Low-water line - Intersection of the low-tide level with the shoreline.
LeezMarginal flood channel - Tidal channel dominated by flood (incoming tide) currents, located between the swash bar and adjacent updrift or downdrift beaches.
M
Microtidal - Coastal setting where the tide rises and falls through a distance of less than 2 meters.
Morphology - The shape of the barrier island's surface and arrangement of land features shaped by water or wind.
N
Nourishment - The process of replenishing a beach. Replenishment may take place naturally or artificially, by the deposition of dredged materials.
O
Outer bar - An extensive sand deposit formed at the seaward end of an inlet’s ebb channel.
Overtopping - The cresting of water over a barrier island or spit as a result of wave run-up or storm surge.
Overwash – The movement of water and sometimes sediment in the wave action that crests the berm and dunes during storms.
P
Profile (beach) - Intersection of the ground surface with a vertical plane that may extend from the crest of the dune line to the seaward limit of sand movement.
Progradation - The building outward toward the sea of a shoreline by sediments deposited by waves or currents.
R
Recreational beach - The zone of sedimentary material extending landward from the low-water line to the place where there is marked change in form, or to the line of stable dune vegetation (usually the effective limit of storm waves). A beach includes foreshore and backshore.
Refraction – Bending of waves due to the effects of different water depths. The part of the wave advancing in shallow water moves more slowly than the part in deeper water.
S
Shoal - Rise in the sea floor or estuary from an accumulation of sand.
Shoreline - Intersection of a specified plane of water with the beach. The delineation of the shoreline on National Ocean Survey nautical charts and surveys approximates the mean high-water line.
Shore-normal - An inlet position that is perpendicular to the shoreline.
Shore-parallel - An inlet position that is parallel to the shoreline.
Swash bar - A small, transitory sandbar built above the still-water level by wave action.
T
Tidal range - Difference in height between consecutive high and low tides. The mean range is the difference in height between the mean high-water line and the mean low-water line.
Tidal Prism – The total volume of water that flows into and out of an estuary or lagoon with the movement of the tide. The tidal prism is a function of lagoon size, tidal range and channel characteristics.
Topography - The configuration of a landmass’s surface, including relief.
U
Updrift - Direction opposite the net movement of littoral materials.
W
Washover - Material deposited by the action of overwash; specifically, an accumulation of sand on the landward side of a barrier island, produced by storm waves breaking over low parts of the island and depositing sediment in the lagoon or on the landward shore.