Glossary of Terms

An offshore consolidated rock hazard to navigation, with a least depth of about 20 metres (10 fathoms) or less. Often refers to coral fringing reefs in tropical waters.

Rubble mound of single-sized stones with a crest at or below sea level which is allowed to be (re)shaped by the waves.

A place for which tidal constants have previously been determined and which is used as a standard for the comparison observations at a second station.

• A station for which independent daily predictions are given in the tide or current tables from which corresponding predictions are obtained for other stations by means of differences or factors.

In regard to beach measuring procedure, the part of the foreshore subject to wave action (between the limit of uprush and the limit of backwash) at mid-tide stage.

The process by which the energy of the wave is returned seaward.

The process by which the direction of a wave moving in shallow water at an angle to the contours is changed: the part of the wave advancing in shallower water moves more slowly than that part still advancing in deeper water, causing the wave crest to bend toward alignment with the underwater contours.

• The bending of wave crests by currents.

Average period of time between occurrences of a given event.

A sloping type of shoreline armouring often constructed from large interlocking boulders. Revetments tend to have a rougher (less reflective) surface than seawalls.

Beach topography consisting of sand bars that have welded to the shore during the recovery stage after a storm. At low tide, water ponds in the runnels and flows seaward through gaps in the ridge.

A nearly continuous mound of beach material that has been shaped by wave or other action. Ridges may occur singly or as a series of approximately parallel deposits.

Tiny drainage channels in a beach caused by the flow seaward of water left in the sands of the upper part of the beach after the retreat of the tide or after the dying down of storm waves.

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.

A protective layer or facing of quarry stone, usually well graded within wide size limit, randomly placed to prevent erosion, scour, or sloughing of an embankment or bluff; also the stone so used. The quarry tone is placed in a layer at least twice the thickness of the 50 percent size, or 1.25 times the thickness of the largest size stone in the gradation.

Assessment of the total risk due to all possible environmental inputs and all possible mechanisms.

An aggregate of one or more minerals; or a body of undifferentiated mineral matter. The three classes of rocks are: (a) igneous - crystalline rocks formed from molten material (e.g. granite and basalt); (b) sedimentary - resulting from the consolidation of loose sediment that has accumulated in layers (e.g. sandstone, shale and limestone); (c) metamorphic - formed from pre-exisiting rock as a result of burial, heat and pressure.

Loose angular water worn stones along a beach. Rough, irregular fragments of broken rock.

A mound of random-shaped and random-placed stones protected with a cover layer of selected stones or specially shaped concrete armour units. (Armour units in a primary cover layer may be placed in an orderly manner or dumped at random.)

A corrugation or trough formed in the foreshore or in the bottom just offshore by waves or tidal currents (see ridge and runnel).

The upper and lower levels reached by a wave on a beach or coastal structure, relative to still-water level.