Swash Zone

The zone of wave action on the beach, which moves as water levels vary, extending from the limit of run-down to the limit of run-up.

Glossary of Terms

Seawall

A structure, often concrete or stone, built along a portion of a coast to prevent erosion and other damage by wave action. Often it retains earth against its shoreward face.

A structure separating land and water areas to alleviate the risk of flooding by the sea. Generally shore-parallel, although some reclamation seawalls may include lenghts that are nromal or oblique to the (original) shoreline.
A vertical or near-vertical type of shoreline armouring characterised by a smooth surface.

Overtopping

Passing of water over the top of a structure as a result of wave run-up or surge action.

Nearshore Current System

The current system characterised primarily by wave action in and near the breaker zone, and which consists of four parts: the shoreward mass transport of water; longshore currents; seaward return flow, including rip currents; and the longshore movement of the expanding heads of rip currents. See also nearshore circulation.

Rip Current

A strong surface current flowing seaward from the shore. It usually appears as a visible band of agitated water and is the return movement of water piled up on the shore by incoming waves and winds. With the seaward movement concentrated in a limited band its velocity is somewhat accumulated. A rip consists of three parts: the feeder currents flowing parallel to the shore inside the breakers; the neck, there the feeder currents converge and flow through the breakers in a narrow band or "rip"; and the head of rip, where the current widens and slackens outside of the breaker line. A rip current is often miscalled a rip tide.

Photic Zone

The zone extending downward from the ocean surface within which the light is sufficient to sustain photosynthesis. The depth of this layer varies with water clarity, time of year and cloud clover, but is about 100m in the open ocean.

It may be considered the depth to which all light is filtered out except for about one percent and may be calculated as about two and a half-times the depth of a secchi disk reading.

Beach Nourishment

The technique of placing sand fill along the shoreline to widen the beach.

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Swash Zone