narrows from north to south along eastern Florida, the slope increases 

 from about zero to 0.00098 (profile lines 23 to 26). From east Texas to 

 west Texas (profile lines 39 to 49), the ramp slope progressively in- 

 creases from 0.00011 to 0.00107 (Fig. 7). Little difference was found 

 when the ramp slope normal to the shelf break was calculated. 



b. Ramp Intercept Depth . Alongshore trends in the intercept depth 

 of the ramp at the shoreline, b, are evident in Table 1. From Cape 

 Hatteras to Georgia (profile lines 13 to 21) the depth of the ramp when 

 extended to the shoreline decreases fourfold from 14.3 to 4.3 meters 

 (47 to 14 feet) (Fig. 8). Along the Florida coast the intercept depth 

 decreases from 19.8 to 5.5 meters (65 to 18 feet) in a southerly direc- 

 tion (profile lines 23 to 26). Along the western and northwestern coast 

 of Florida the intercept depth is almost zero. This region, which has 

 little wave activity, is where the shoreface is absent or very narrow and 

 the ramp extends nearly to the shoreline. Along the Texas coast (profile 

 lines 40 to 49), the intercept depth varies randomly between 7.3 and 13.4 

 meters (24 to 44 feet), averaging 10.4 meters (34 feet). The ramp slope 

 along the same coast increases sixfold to the southwest, suggesting 



the shelf surface slope and present shoreline position are probably not 

 genetically related. 



c. Shoref ace-Ramp Boundary . An accurate distance to the shoreface- 

 ramp boundary, 3c, is difficult to determine because the sectors appear 

 to join asymptotically, and on a very gradual slope (App. C) . A further 

 complication in determining the distance exists because the lower shore- 

 face is not always smooth (Fig. 4). There was no significant shoreface 

 on 3 profiles (profile lines 29, 30, and 31); 19 profiles exhibited a 

 smooth lower shoreface; 13 were depressed types; and 14 were elevated. 



The depth at the shoreface-ramp boundary, g (Table 1), displays a 

 greater profile-to-profile similarity, or progressive alongshore change, 

 than does the distance to the. boundary. For example, between profile line 

 10 and profile line 21, the boundary depth progressively decreased from 

 19.5 to 4.7 meters (64 to 15 feet) (Fig. 8); the distance to the boundary 

 did not exhibit as significant a trend. Because the shoreface and ramp 

 appear genetically different, at least in some areas, the boundary loca- 

 tion is important. It may designate the cutoff region of significant 

 active modification of the profile by present wave and current processes. 

 It may also delimit the zone seaward, where man-caused or natural profile 

 changes will not produce a sympathetic effect on the coastal beaches. 



d. Shoreface Concavity . Concavity, f (Table 1), indicates the 

 deviation of the shoreface slope from planar. A highly concave-up 

 (depressed) shoreface is represented by a low concavity value (Fig. 9). 

 An elevated shoreface will exhibit a larger concavity value. A con- 

 cavity value above f = 1.87 represents a convex shoreface slope, but 



no such case occurred in the profiles. Along the Texas coast concavity 

 values are near constant (0.8) and twice as large as the Atlantic 

 coast values. Concavity is to some extent dependent on the energy 

 distribution of waves acting upon the profile. 



22 



