Glossary of Coastal Geology Terms

Accretion - Accumulation of sand or other material at a point due to natural action of waves, currents and wind. A build-up of the beach or dune.

Alongshore - Parallel to and near the shoreline; same as longshore.

Bar - Fully or partly submerged mound of sand, built on the bottom in shallow water by waves and currents.

Barrier - A long, narrow sandy island or spit, representing a barrier beach that is above high tide and parallel to the shore, and that commonly has dunes, shrubby zones, and marshes within the lagoon.

Bathymetry - The science of measuring ocean depths and the charting of the topography of the ocean floor.

Beach - A mobile deposit of sand that extends from the toe of the dunes, at approximately 7 to 8 feet above MSL, seaward to water depths of 25 to 30 feet. The shape of both the above and below water portions of the deposit is constantly adjusting due to changing energy conditions.

Beach fill - 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 sands and gravels. Some beaches have no berms, others have one or several.

Breakwater - Artificial or natural structure aligned parallel to shore, sometimes shore-connected, that provides protection from waves.

Channel margin linear bars - Levee-like sand deposits built by the interaction of the ebb and flood tidal currents with wave generated currents. These bars flank the ebb channel.

Current, alongshore - Current in the breaker zone moving essentially parallel to shore and usually caused by waves breaking at an angle to shore. Also called alongshore current.

Downdrift - Direction of net alongshore movement of littoral materials.

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 angle to the adjacent shoreline. The seaward extension of the ebb channel is termed the outer-bar channel.

Ebb delta breaching - Repositioning of the main channel across the ebb delta and the resulting movement of large sand bars to the landward regions of the shoals and the adjacent shoreline.

Ebb-tidal delta - A delta-like deposit of sand just seaward of a tidal inlet posing a hazard to navigation, but often protecting adjacent beaches from severe erosion by their breakwater effect. Also commonly referred to as the outer bar (shoal)

Equilibrium - State of balance of opposing forces.

Erosion - The wearing away of land by natural forces such as waves and wind.

Foreshore - The part of the shore lying between the crest of the seaward berm (or upper limit of wave wash) and the water’s edge at low water. The foreshore is ordinarily traversed by the runup and backwash of the waves.

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.

High tide - Maximum elevation reached by the rising tide.

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 (HWL).

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 mean low water to mean high water.

Lee - Sheltered part facing away from waves.

Littoral drift - The sedimentary material moved along the shoreline under the influence of waves and currents.

Littoral transport - Movement of littoral drift along the shoreline by waves and currents. Includes movement parallel (longshore transport) and perpendicular (on-offshore transport) to the shore.

Longshore - Parallel to and near the shoreline.

Longshore transport rate - Rate of transport of littoral material parallel to shore. Usually expressed in cubic yards per year or cubic meters per year.

Low water line - Intersection of the low tide level with shoreline (LWL).

Marginal flood channel - Tidal channel, dominated by flood (incoming tidal currents) currents that occur between the swash platform and adjacent updrift and downdrift beaches. One of these channels is commonly better developed.

Microtidal – A 0-2m tidal range.

Morphology - The shape of the barrier's surface and arrangement of landform units.

Nourishment - The process of replenishing a beach. Replenishment may be brought about naturally, or artificially, by the deposition of dredged materials.

Outer bar - An extensive sand bar formed at the seaward end of an ebb channel of an inlet.

Overtopping - The passing of water over the top of a barrier island or spit as a result of wave runup or storm surge.

Overwash - A mass of water and sometimes sediment representing the part of the uprush that runs over the berm crest and the dunes during storms.

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.

sediments by waves or currents.

Recreational beach - The zone of sedimentary material that extends landward from the low water line to the place where there is marked change in form, or to the line of permanent vegetation (usually the effective limit of storm waves). A beach includes foreshore and backshore.

Refraction - Process by which the direction of a wave moving in shallow water at an angle to the contours is changed. Part of the wave advancing in shallower water moves more slowly than the part still advancing in deeper water.

Shoal - Rise of the sea floor or estuary from an accumulation of sand.

Shoreline - Intersection of a specified plane of water with the beach. The line delineating the shoreline on National Ocean Survey nautical charts and surveys approximates the mean high water line. In this study the shoreline refers to the HWL (wet/dry line).

Swash bar - A small, transitory sand bar built above the stillwater level by wave action.

Tidal range - Difference in height between consecutive high and low tides. The mean range is the difference in height between mean high water and mean low water.

Tidal Prism – The total amount of water that flows into a harbor or estuary or out again with movement of the tide, excluding freshwater flow.

Topography - Configuration of a surface including relief.

Updrift - Direction opposite the net movement of littoral materials in longshore transport.

Washover - Material deposited by the action of overwash; specifically an accumulation built on the landward side of a barrier island, produced by storm waves breaking over low parts of the barrier and depositing sediment in the lagoon or on the landward side of the island.