3.2. Seasonal Beach Change and Variability 



Beaches and dunes are dynamic morphologic features that experience substantial seasonal 

 fluctuations and spatial variability in elevation, width, and shape. In winter, beaches commonly 

 have low relief because energetic waves and currents remove sand from the beach face and 

 transport it offshore. Conversely, in summer, beaches typically display constructive features 

 formed from sand deposited on the foreshore. Typical winter and summer beach profiles are 

 depicted schematically in Figure 3-1. In regions with relatively low rates of long-term shoreline 

 recession, seasonal changes in shoreline position can exceed the annual recession rate by many 

 times. Consequently, accurate representation of average beach change depends on consistent 

 seasonal comparisons to reduce inter-annual variations. For Brevard County, inter-annual 

 variation in shoreline position associated with seasonal change is estimated to reach ±30 ft by 

 examination of FDEP beach-profile surveys. 



Summer profile 



/— Berm crest 

 / s— MHW Shoreline (Summer) 



MHW 



MHW Shoreline 

 (Winter) 



Storm (Winter) 

 Profile — 



Figure 3-1 . Schematic showing typical winter and summer beach profile shapes. 



Another factor influencing shoreline position as determined from beach-profile survey data is 

 the uncertainty associated with interpolating between FDEP lines (R-monuments) that are spaced 

 approximately 800 to 1,000 ft apart. This uncertainty is of particular concern at the study site, 

 which has mixed nourished beach and natural beach together with coastal structures. Depending 

 on natural variation in beach and dune morphology along a coast and the influence of structures 

 (e.g., seawalls, bulkheads, and rubble), variability in shoreline position is estimated to be as 



16 



Comparison of profile shape at R-7 and R-44 (Figures 4-5 and 4-11) for winter (January 1985) and summer (August 

 1985) shows a 30-ft maximum seasonal change in contour position. 



3-4 Chapter 3 Assessment of Coastal Change 



