deadman— The buried object to which bulkhead or seawall tiebacks are attached. An anchor 

 pile may be used in lieu of a deadman. 



deep water— Water so deep that surface waves are little affected by the ocean bottom. 

 Generally, water deeper than one-half the surface wavelength is considered deep water. 



delta— An alluvial deposit, usually triangular or digitate in shape, formed at a river mouth. 



diaphragm breakwater— A comparatively thin, impervious wall, membrane, or structure 

 designed to resist wave penetration, usually a secondary defense structure. 



diffraction diagram— A diagram showing lines of equal wave height (and sometimes 

 successive crest positions) after a wave of given characteristics has undergone diffraction 

 about the end of a breakwater or through a gap. 



dock— A fixed or floating decked structure against which a boat may be berthed either 

 temporarily or indefinitely. 



dolphins— A cluster of battered pilings joined at the top. 



downdrift— The direction of predominant movement of littoral materials. 



ebbtide— The period of tide between high water and the succeeding low water; a falling tide. 



ecological preservation— Maintaining the natural balance or pattern in the relationship 

 between marine or near -water organisms and their environment. 



eddy current— A circular movement of water formed on the side of a main current. Eddies 

 may be created at points where the main stream passes projecting obstructions or where 

 two adjacent currents flow counter to each other. 



estuary— (1) The part of a river that is affected by tides. (2) The region near a river mouth in 

 which the freshwater of the river mixes with the saltwater of the sea. 



exchange of water— The flushing or replacement of water in a basin area, usually that 

 required to combat pollution or to ensure good water quality. 



fairway— The parts of a waterway that are open and unobstructed for navigation. 



fendering system— A protective bumper system designed to prevent damage to either boats 

 or docks whenever they come in contact. 



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