TIDEj MIXED - A type of tide in which the presence of a diurnal wave is 

 conspicuous by a large inequality in either the high or low water 

 heights with two high waters and two low waters usually occurring 

 each tidal day» In strictness all tides are mixed but the name is 

 usually applied without definite limits to the tides intermediate 

 to those predominantly semidiurnal and those predom.inantly diurnal, 

 (See Fig\ire A-10) , 



TIDE. NEAP - A tide occurring near the time of quadrature of the moon. 

 The neap tidal range is usually 10 to 30 percent less than the mean 

 tidal r ange . 



TIDE J SEMIDIURNAL - A tide with two high and two low waters in a tidal 



day J, with comparatively little diurnal inequality. (See Figure A-IO) 



TIDEj bXACK - The state of a tidal cui-rent when its velocity is near zero, 

 especially the moment when a reversing current changes direction and 

 its velocity is zeroo 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 STAND. Also SLACK WATER. 



TIDE^ SPRING " A tide that occurs at or near the time of new and full 

 moon and which rises highest and falls lowest from the mean level. 



TIDE, ST0Ri4 - The rise of vjater accompanying a storm caused by wind 

 stresses on the water surface. See also SET-UP, Wli'fD. 



TOMBOLO - An area of unconsolidated material^ deposited by wave action 

 or currentSj that connects a rock^ or island, etc. to the mainland 

 or to another island. (See Figure A-9) 



TOPOGRAPHY - The configuration of a surface including its relief, the 

 position of its streatis, roads^ buildings, etc, 



TRAINING WALL = A wall or jetty to direct cuirrent flow. 



TRANSITIONAL Z0I\fE 



TRANSITIONAL WATER - In regard to progressive gravity waves^ water whose 



depth is less than 1/2 but not more than 1/25 the wave length =, Often 



called SHALLOW WATER. 



IROCHOIDAIi WAVE - A progressive oscillatory wave whose form is that of a 

 prolat^e cycloid or trochoid. It is approximated by wax^es of small 

 amplitude. See also WAVEj CYGLOIDAL,. 



TROUGH OF WAVE - The lowest part of a wave form between successive crests. 

 jU.so that part of a wave below still water level. (See Figure A-3) . 



TSUNAMI - A generally long period wave caused by londerwater seismic 



disturbance or volcanic eruption. Commonly misnamed "tidal wave", 



A- 36 



