Datum (vertical)

 For marine applications, a base elevation used as a reference from which to reckon heights or depths.  It is called a tidal datum when defined in terms of tidal phenomena and is based on a 19-year tide cycle (in the USA)- the datum is referenced to a fixed point typically known as a bench mark.

Decision maker

 The person or organizational unit that decides on a course of action in relation to the safety of a dam on the basis of a range of considerations which may include a risk assessment.


 A lowering of the beach profile.

Delphi method

 A technique for obtaining subjective judgmental values through iterative estimations by a group of experts


Where a river reaches the sea and splits up into many channels, depositing large quantities of mud over a wide area. These areas are usually very wet or swampy.


When mud, sand or pebbles are dropped by the sea.

Detached Breakwater

  A breakwater without any coastal connection to the shore.


The particulate, organic remains and waste of organisms. It constitutes a major food source in marine ecosystems

Dikes and Levees

  Dikes are typically earth structures (dams) that keep elevated water levels from flooding interior lowlands.


 A serious disruption of the functioning of a community or a society causing widespread human, material, economic or environmental losses which exceed the ability of the affected community or society to cope using its own resources.

Dissolved Oxygen (DO)

 The quantity of oxygen dissolved in a unit volume of water; expressed as milligrams per liter (mg/L) or parts per million (ppm).


A stretch of coast with specially built sea walls and deep water so that ships can come in to load and unload.


Oval or circular mounds that generally lack a slipface. Dome dunes are rare and occur at the far upwind margins of sand seas.


Flow in the direction of net long shore sediment transport


 The excavation of sediments and other material from aquatic areas for the purpose of maintaining adequate depths in navigation channels and berthing areas, as well as for other purposes.


Any deliberate disposal at sea of wastes or other matter, or any deliberate disposal of vessels or other man-made structures 


A bank of sand piled up by the wind. The sand usually blows off a beach so dunes are often found behind a beach.

Dune Restoration

The technique of rebuilding an eroded or degraded dune through one or more various methods (sand fill, drift fencing, revegetation, etc.).

Dune face

 The seaward face of a dune system where coastal processes may cause erosion or accretion.


 Accumulations of sand in ridges or mounds landward of the beach berm formed by natural processes and usually parallel to the shoreline.


Something that is changing with time. The sea slowly wears away the coast and so the coast changes - it is dynamic.