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OSCILLATORY WAVE - A wave in which each individual particle oscillates 

 about a point with little or no permanent change in mean position. 

 The term is commonly applied to progressive oscillatory waves in 

 which only the form advances, the individual particles moving in 

 closed or nearly closed orbits. Distinguished from a WAVE OF 

 TRANSLATION. See also ORBIT. 



OUTFALL - A structure extending into a body of water for the purpose of 

 discharging sewage, storm runoff, or cooling water. 



OVERTOPPING - Passing of water over the top of a structure as a result 

 of wave runup or surge action. 



OVERWASH - That portion of the uprush that carries over the crest of a 

 berm or of a structure. 



PARAPET - A low wall built along the edge of a structure as on a seawall 

 or quay . 



PARTICLE VELOCITY - The velocity induced by wave motion with which a 

 specific water particle moves within a wave. 



PASS - In hydrographic usage, a navigable channel through a bar, reef, 

 or shoal, or between closely adjacent islands. 



PEBBLES - See SOIL CLASSIFICATION. 



PENINSULA - An elongated body of land nearly surrounded by water, and 

 connected to a larger body of land. 



PERCHED BEACH - A beach or fillet of sand retained above the otherwise 

 normal profile level by a submerged dike. 



PERCOLATION - The process by which water flows through the interstices of 

 a sediment. Specifically, in wave phenomena, the process by which 

 wave action forces water through the interstices of the bottom 

 sediment. Tends to reduce wave heights. 



PERIODIC CURRENT - A current caused by the tide-producing forces of the 



moon and the sun, a part of the same general movement of the sea that 

 is manifested in the vertical rise and fall of the tides. See also 

 CURRENT, FLOOD and CURRENT, EBB. 



PERMANENT CURRENT - A current that runs continuously, independent of the 

 tides and temporary causes . Permanent currents include the fresh- 

 water discharge of a river and the currents that form the general 

 circulatory systems of the oceans. 



PERMEABLE GROIN - A groin with openings large enough to permit passage of 

 appreciable quantities of littoral drift. 



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