PORTLAND, ME 

 FMAMJJASOND 

 -I — I — I — I — I — r 



HAMPTON ROADS, VA 

 FMAMJJASONDJ 



T 



MIAMI BEACH. FL A 

 JFMAMJJASONDJ 



-i I I 1_1 I L. 



Figure 6. Departure from the annual mean of average monthly sea level, water 

 density, temperature, and salinity at three primary tide stations (Emery and 

 Uchupi 1972). Departures from the monthly mean for nearby river discharge 

 (bottom line) are given for comparison. 



In a detailed study of sedimentation 

 on a Louisiana marsh, Baumann (1980) 

 found that sediment deposition was not 

 correlated with mean sea level or 

 duration of submergence, but with the 

 concentration of sediment in the 

 flooding water. It is likely that 

 many marsh-water interactions are 

 variable and complicated, and that the 

 strength of any particular coupling 

 may not be a simple function of the 

 duration of submergence. 



Tides 



In 

 changes 

 caused 

 regular 

 thought 



contrast to water level 



discussed earlier, variations 



by the tides are remarkably 



and their influences are 

 to be "the most significant 



11 



environmental factors responsible 

 for the segregation of salt-marsh 

 vegetation" (Redfield 1972). Tides 

 along the Atlantic coast of the United 

 States are semidiurnal and symmetrical 

 with a period of 12 hr 25 min, in 

 marked contrast to those of the Gulf 

 of Mexico and Pacific coasts (Figure 

 8). The tides along the northeast and 

 much of the southeast coast are also 

 of considerably greater range (1 to 

 3 m or 3.3 to 10 ft) than those along 

 the Gulf of Mexico coast (Figure 9). 

 There is a substantial and regular 

 variation in the tidal range, not only 

 with the lunar cycle as shown in 

 Figure 8, but over the annual cycle as 

 well. While the tidal range is 

 greatest during full and new moon, the 

 highest and lowest tides occur nearest 



