DECEMBER 1970 

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LOS ANGELES 

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Figure 8. Typical curves of the predicted daily tide during December 1970 for 

 stations on the Atlantic, Gulf of Mexico, and Pacific coasts of the United 

 States (Emery and Uchupi 1972). 



for a particular marsh area by using 

 a measured tidal record as short as 

 15 days (Palmer et al. 1980). 



Despite our long-standing ability 

 to predict the tides with reasonable 

 accuracy (except when winds, baro- 

 metric pressure, or fresh water 

 influences dominate), it is difficult 

 to predict water level in a salt 

 marsh or other coastal embayment 

 because water level results from a 

 set of interactions. Water 

 especially as affected by 

 has traditionally been 

 the major influence in 

 marsh ecology. Water 

 has been used often for 

 wetlands in inventories 



13 



complex 



level, 



tides, 



considered 



determining 



level also 



classifying 



and in legal descriptions protecting 

 or regulating various portions of 

 the coastal environment, particularly 

 descriptions of wetlands (Kavenagh 

 1980). There may be good ecological 

 reasons, however, for doubting that 

 marsh vegetation is finely tuned to 

 the tides and water levels (Lagna 

 1975) because concepts like mean sea 

 level, mean high water, and mean low 

 water are arbitrary simplifications 

 that depend on the time interval 

 chosen. The relative position of 

 the land-water-air interface over a 

 defined time interval is a physical 

 reality; it can be readily measured, 

 and its importance in the marsh 

 has been a central theme in coastal 

 ecology for at least 50 years. 



