parallel criterion depths were larger. Along-coast trends obvious in 

 the seaward-limit depth using the shoreface-ramp criterion were not as 

 obvious when using the shore-parallel contour criterion (Table 2). 



In the western part of the gulf, many contours were shore-parallel 

 past the end of the profiles (30.5 kilometers). A problem in using the 

 shore-parallel contour criterion was created because some of the depths 

 beyond which the contours are shore-parallel, exceeded 55 meters (180 

 feet). This is probably well below the depth of significant sediment 

 transport. In other areas, contour shore-parallelism was lost because 

 of shore-connected shoals. The shoals angle away from the coast, and 

 often begin in quite shallow depths. In most cases, they are probably 

 still part of the active profile. On profile lines 29, 30, and 31 where 

 a shoreface is absent, shore-parallel contours do not exist. No signifi- 

 cant offshore sediment transport is suggested in this region of the 

 Florida coast. 



The rms depth criterion is a quantitative measure to describe the 

 shore-parallelism of contours. It proved least consistent of any method. 

 It is less subjective than the shore-parallel contour method, but directed 

 at the same boundary; i.e., the transition between shore-parallel and 

 irregular contours. The rms criterion also becomes less useful when the 

 contours are parallel, but oriented at a slight angle relative to the 

 coast. 



Results of this study indicate the shoreface-ramp criterion is more 

 consistent in an alongshore direction than the shore-parallel contour 

 criterion. The shoreface-ramp method is also more objective when calcu- 

 lated as discussed in this report. The limiting depth obtained by either 

 method is the depth of the change in shape or smoothness of the Inner 

 Continental Shelf. It may or may not be indicative of the seaward limit 

 of sediment transport to or from the beach. 



VII. SUMMARY 



1. The Inner Continental Shelf profile along the U.S. Atlantic and 

 Gulf of Mexico coasts exhibits a two-sector shape. Near the coast the 

 shoreface sector is steep and concave-up. Farther seaward, the ramp 

 sector is planar with a gradual slope away from the coast. The steepest 

 slope is near the shore. The largest concavity is near the shoreface- 

 ramp boundary. 



2. In most cases, no relationship was found between the geometric 

 characteristics of the shoreface and those of the ramp (Table 1). 

 Likewise, no relationship was evident in the along-coast trend of the 

 geometric characteristics on the shoreface and those on the ramp. This 

 lack of correlation suggests different origins for these sectors. The 

 shoreface today may be in, or approaching, some form of equilibrium with 

 the existing wave climate, shelf currents, available sediment supply, 

 sea level changes, and other factors; the large-scale ramp bathymetry is 



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