SHOHE FACE - The narrow zone seaward from the low tide SHORELINE per- 

 manently covered by vrater, over which the beach sands and gravels 

 actively oscillate with changing wave conditions. 



SHORE LINE - The intersection of a specified plane of water with the 

 shore or beach, (e.g. the high water shore line would be the 

 intersection of the plane of mean high water witli tha shore or 

 beach). The line delineating the shore 1 ins on 5J, 3, Coast and 

 Geodetic Survey nautical charts and surveys approximates the mean 

 high water line. 



SIGNIFICANT WAVE - A statistical term denoting waves with the average 

 height and period of the one-third highest waves of a given wave 

 group. The composition of the higher 'Ma ves depends upon the ex- 

 tent to whicli the lower waves are considered. Experience so far 

 indicates that a careful observer who attempts to establish the 

 character of the higher waves will record values which approximately 

 fit the definition, A wave of significant wave period and signifi- 

 cant wave height, 



SIGNIFICANT WAVE HEIGHT - The average height of the one- third highest 



waves of a given wave group. Note that the composition of the highest 

 waves depends upon tiie extent to which the lower waves are con- 

 sidered. In wave record analysis., the average height of the 

 highest 1/3 of a selected number of waves, this number being 

 determined by dividing the time of record by the sigra-ficant period. 

 Also CHARACTERISTIC V/AVE HEIGHT o 



SIGNIFICANT kAVE PERIOD - An arbitrary period generally taken as the 

 period of the I/3 highest waves within a, given group. Note that 

 the composition of the highest waves depends upon the extent to w hich 

 the lovrer waves are considered. In wave record analysis^, tiiis is 

 detennined as the average period of the most frequently recurring 

 of the larger well-defined waves in the record under study. 



SILT - See SOIL CLASSIFICATION, 



SLACK TIDE (SLACK WATER) - The state of a tidal current when its velocity 

 is near zero^ especially the moment when a reversing current changes 

 direction and its velocity is zero. Sometimes considered the 

 intermediate period between ebb and flood currents during which the 

 velocity of the currents is less than 0,1 knot. See TIDAL STANDo 



SLIP - A space between two piers, wharves, etc. for the berthing of 

 vessels. 



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