Although most of the marsh in this area is flooded twice daily, the upper limit of salt-tolerant 

 species is considerably above mean high water. Because of the lunar cycle and other astronomic 

 or climatic events, higher tides than average occur periodically. Spring tides occur approximately 

 fortnightly in conjunction with the new and full moons. The statistical average of these, referred 

 to as mean high water spring, has an elevation of 1.0 m (3.1 ft) above mean sea level in Charleston 

 (U.S. Department of Commerce 1981). 



Less frequent tidal flooding occurs annually at even higher elevations ranging upwards of 

 1.5 m (5.0 ft) above mean sea level. In a South Carolina marsh near the case study area, the flood- 

 ing of marginal highland occurred at elevations of 1.5-2 m above mean sea level (approximately 

 80 cm above normal). The peak astronomic tide that was responsible for the flooding included an 

 estimated wind setup of 15-20 cm (0.5-1.0 ft) under 7-9 m/s (13-17 mph) northeast winds. 



FIGURE 2-1 



CHARLESTON STUDY AREA 



GULF OF MEXICO 



40 



