UPLIFT - The upward water pressure on the base of a structure or 

 pavement . 



UPRUSH - The rush of water up onto the beach following the breaking of 

 a wave. Also SWASH, RUNUP. (See Figure A-2.) 



VALLEY, SEA - A submarine depression of broad valley form without the 

 steep side slopes which characterize a canyon. 



VALLEY, SUBMARINE - A prolongation of a land valley into or across a 

 continental or insular shelf, which generally gives evidence of 

 having been formed by stream erosion. 



VARIABILITY OF WAVES - (1) The variation of heights and periods be- 

 tween individual waves within a wave train. (Wave trains are not 

 composed of waves of equal height and period, but rather of 

 heights and periods which vary in a statistical manner.) (2) The 

 variation in direction of propagation of waves leaving the gen- 

 erating area. (3) The variation in height along the crest, 

 usually called "variation along the wave". 



VELOCITY OF WAVES - The speed at which an individual wave advances. 

 See WAVE CELERITY. 



VISCOSITY - (or internal friction) - That molecular property of a 

 fluid that enables it to support tangential stresses for a 

 finite time and thus to resist deformation. 



WATERLINE - A juncture of land and sea. This line migrates, changing 

 with the tide or other fluctuation in the water level. Where 

 waves are present on the beach, this line is also known as the 

 limit of backrush. (Approximately the intersection of the land 

 with the Stillwater level.) 



WAVE - A ridge, deformation, or undulation of the surface of a liquid. 



WAVE AGE - The ratio of wave speed to wind speed. 



WAVE, CAPILLARY - See CAPILLARY WAVE. 



WAVE CELERITY - Wave speed. 



WAVE CREST - See CREST OF WAVE. 



WAVE CREST LENGTH - See CREST LENGTH, WAVE. 



WAVE, CYCLOIDAL - See CYCLOIDAL WAVE. 



WAVE DECAY - See DECAY OF WAVES. 



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