PORT - A place where vessels may discharge or receive cargo; may be the 



entire harbor including its approaches and anchorages, or may be the 

 commercial part of a harbor where the quays, wharves, facilities for 

 transfer of cargo, docks, and repair shops are situated. 



POTENTIAL ENERGY OF WAVES - In a progressive oscillatory wave, the energy 

 resulting from the elevation or depression of the water surface from 

 the undisturbed level. 



PRISM - See TIDAL PRISM. 



PROBABLE MAXIMUM WATER LEVEL - A hypothetical water level (exclusive of 

 wave runup from normal wind-generated waves) that might result from 

 the most severe combination of hydrometeorological , geoseismic and 

 other geophysical factors that is considered reasonably possible in 

 the region involved, with each of these factors considered as affect- 

 ing the locality in a maximum manner. 



This level represents the physical response of a body of water 

 to maximum applied phenomena such as hurricanes, moving squall lines, 

 other cyclonic meteorological events, tsunamis, and astronomical tide 

 combined with maximum probable ambient hydro logical conditions such 

 as wave setup, rainfall, runoff, and river flow. It is a water level 

 with virtually no risk of being exceeded. 



PROFILE, BEACH - Tlie intersection of the ground surface with a vertical 



plane; may extend from the top of the dune line to the seaward limit 

 of sand movement. (See Figure A-1.) 



PROGRESSION (of a beach) - See ADVANCE. 



PROGRESSIVE WAVE - A wave that moves relative to a fixed coordinate system 

 in a fluid. The direction in which it moves is termed the direction 

 of wave propagation. 



PROMONTORY - A high point of land projecting into a body of water; a 

 HEADLAND . 



PROPAGATION OF WAVES - The transmission of waves through water. 



PROTOTYPE - In laboratory usage, the full-scale structure, concept, or 

 phenomenon used as a basis for constructing a scale model or copy. 



QUAY (Pronounced KEY) - A stretch of paved bank, or a solid artificial 



landing place parallel to the navigable waterway, for use in loading 

 and unloading vessels. 



QUICKSAND - Loose, yielding, wet sand which offers no support to heavy 



objects. The upward flow of the water has a velocity that eliminates 

 contact pressures between the sand grains, and causes the sand-water 

 mass to behave like a fluid. 



A-27 



