Coastal Processes and Sea Level Dynamics

Vocabulary flashcards covering wave mechanics, tidal variations, coastal geomorphology, relative and eustatic sea-level changes, and coastal erosion control structures.

Wave Base

The maximum water depth at which orbital wave motion is felt, beneath which water motion becomes negligible; typically equal to approximately $\frac{1}{2}$ of the wavelength.

Breaker

A collapsing ocean wave formed as waves enter shallow water where friction slows the wave base, resulting in reduced wavelength, reduced velocity, and an increase in wave height until it breaks.

Absolute (Eustatic) Sea Level Change

Global changes in ocean height driven primarily by fluctuations in glacier/ice sheet volume, thermal expansion or contraction of seawater, or variations in the volume and shape of ocean basins due to tectonic plate movements.

Relative Sea Level Change

A localized or regional rise or fall in sea level measured relative to land elevation, predominantly influenced by regional tectonic uplift or subsidence.

Spring Tide

A tide of maximum range occurring when the Earth, Moon, and Sun are aligned, resulting in the highest tides.

Neap Tide

A tide of minimum range occurring when the Moon and Sun are positioned at right angles to each other relative to Earth, resulting in the lowest high tides.

Submergent Coastline

A coastal setting where sea level rises relative to land elevation due to global eustatic rise, subsidence, or tectonic movement, typically characterized by drowned river valleys and estuaries.

Emergent Coastline

A coastal setting where sea level drops relative to land elevation, commonly caused by tectonic uplift of the continental plate, often developing distinctive wave-cut platforms.

Wave-Cut Platform

A level or gently sloping bench-like rock terrace carved by wave erosion at the base of sea cliffs that becomes exposed following coastal uplift or a drop in relative sea level.

Estuary

A tidally controlled coastal body of water open to the sea where freshwater runoff from land mixes with seawater to create brackish conditions.

Headland

A point of high coastal land that juts out into the surf zone, focusing incoming wave energy and increasing local susceptibility to wave erosion.

Wave Refraction

The bending of incoming wave crests as they reach shallow water near shorelines or headlands, caused when segments of the wave touch bottom first and decelerate relative to deeper portions.

Longshore Current

A water current that moves parallel along the shoreline within the surf zone, generated when incoming waves approach the beach at an angle.

Littoral Drift

The net transport of sand along a beach face in the direction of the longshore current, caused by waves washing sand up at an angle and receding down along the slope of gravity.

Groin

A coastal engineering structure built perpendicular to the shoreline designed to trap sediment transported by littoral drift, commonly causing sand starvation and accelerated erosion down-current.

Breakwater

A protective barrier constructed offshore to dissipate wave energy and reduce erosion immediately behind it, which may channel longshore currents to either side and accelerate flank erosion.

Beach Nourishment

A soft coastal management strategy involving the placement of sand pumped from offshore back onto an eroding beach, requiring matching grain size to remain in dynamic equilibrium with local waves.

Barrier Island

A long, narrow, low-lying offshore ridge of sand running parallel to a passive margin coastline, providing wave and storm protection to back-barrier bays, lagoons, and salt marshes.