Longitude of the shoreline intercept of the line were recorded to one 

 one-hundredths of a minute (see App. A). Four additional profile lines 

 spaced at 1.5 kilometers (5,000 feet) were drawn upcoast and four were 

 drawn downcoast parallel to the centerline (App. B) . This resulted in 

 a set of nine profile lines at equal spacing along 12 kilometers of 

 coast. Each profile line was extended seaward 30.5 kilometers (19 miles) 

 from the mean low water (MLW) shoreline. Depths were obtained from the 

 charts using an acetate overlay on which marks were scribed at 30 sta- 

 tions, graduated in increasing distance intervals from the zero-depth 

 position (App. B) . Higher resolution was used near the shore because 

 wave action tends to create greater slopes there. Selection of the 

 station intervals was also based on the typical frequency distribution 

 of depth variations on the charts between stations away from the coast. 

 Figure 2 is an example of the profile line spacing and bathymetry on a 

 1200 series chart. At each locality an arithmetic mean depth was de- 

 rived for each of the 30 distance stations by averaging depth values 

 from all 9 profiles. The resultant mean profile constituted the basic 

 data used in the study. These profiles are in Appendix C. Unless 

 otherwise stated, further references to profiles in this report refer 

 to the average of nine profiles. 



2. Shore- Parallel Contours . 



For comparison with the location of the shoreface-ramp boundary 

 obtained using the profiles, the seaward limit of shore-parallel 

 contours was measured at the center of each of the 49 localities where 

 depth-distance data were averaged. The seaward limit was defined as 

 the transition depth where bathymetric contours changed from smooth and 

 shore-parallel to irregular or no longer shore-parallel. All seaward- 

 limit values were obtained using the same 1200 series charts used in 

 selecting depth-distance pairs. Figure 2 illustrates a shelf location 

 with an abrupt transition from shore-parallel to irregular contour; 

 a smooth, shore-parallel contour is shown in Figure 3. 



At 31 of the 49 localities the root mean square (rms) (standard 

 deviation) of the nine depth values for each of the 30 distance stations 

 was also computed. This was done to determine if there was a less sub- 

 jective way than that previously described to determine where contour 

 irregularity replaces shore-parallelism. The thesis was that the devia- 

 tion about the mean of depths obtained at constant distances from shore 

 would reflect the change from the shore profile to the region of offshore 

 (ramp) irregularity. 



IV. RESULTS 



1 . Shoreface Types . 



Three types of shoreface profile predominated (Fig. 4), but the ramp 

 shape (planar, seaward-dipping) was similar on all profiles. The shore- 

 face varied about a profile which smoothly coupled with the ramp as shown 

 for profile line 15. Two extreme cases of shoreface-ramp coupling are alsc 



12 



