IV-39 



published for each day of each year for each major port of the 

 world. Such predictions are valuable both to the captain trying 

 to dock a large oil tanker and to the fisherman who is trying to 

 find where the big ones are biting. 



Perhaps because tides are so easily understood and predicted, 

 and are so easily observable everywhere, their importance in 

 the estuarine zone has been largely overlooked. 



Table IV. 1.4 gives typical tidal characteristics in several estua- 

 ries of the United States. It is immediately apparent that tides 

 on each coast of the United States are different. Along the 

 Atlantic and Pacific coasts there are semidiurnal tides, 1 .e . , 

 two complete tides in a little over one day, but the Atlantic 

 tides are equal and the Pacific tides are unequal. In the Gulf 

 of Mexico most places have one tide a day, 1 .e . , diurnal, but 

 some places such as Tampa Bay exhibit both kinds of tides at 

 different times of the month. 



Tide ranges, i .e . , the difference between high water and low 

 water, are not so uniform. These are largely a matter of shape, 

 size, and bottom material in individual estuarine areas. Ranges 

 vary from the barely noticeable rises and falls of some lagoons 

 along the Gulf of Mexico to the tremendous 28-foot range in 

 Alaska's Cook Inlet.* 



*A tidal bore, a single breaking wave bringing in the flood tide, 

 is characteristic of Turnagain Arm of Cook Inlet at certain times, 

 This is the only tidal bore in the United States. 



