2. Shoref ace-Ramp Boundary . 



Irregularities common in the lower part of the shoreface (Fig. 4) 

 limit its use in determining where the ramp and shoreface merge. The 

 landward limit of shoreface irregularities was near the first station 

 with a slope less than three times the mean ramp slope, a, or less 

 than 0.0006. Consequently, this was arbitrarily selected as the defini- 

 tion of the boundary between the lower and upper shoreface. Use of the 

 0.0006 value is necessary because 12 percent of the offshore gradients 

 were less than 0.0002 (Table 1), and exclusive use of the ramp slope 

 criterion would result, at times, in defining the upper shoreface within 

 an irregular region. The distance, c, from the shoreline to the upper 

 and lower shoreface boundary is as shown in Figure 5. 



The shoreface and ramp intersect asymptotically making the location 

 of the coupling difficult to determine. The distance 3c approximated 

 the location such that the calculated ramp depth was within 3 percent of 

 the actual depth. 



3. Shoreface Term . 



The shoreface slope, steepest near the shoreline, usually exhibited 

 maximum concavity near the ramp (Fig. 5). The shoreface shape may be 

 approximated by an exponential curve of the form. 



dz 



= -k,z, (D-3) 



dx 1 



in which k^ is the constant, and Zg is the depth to the shoreface 

 profile. An exponential fitting method was selected because wave energy 

 available at the bottom, which partially molds the profile shape, de- 

 creases exponentially with depth. Equation (D-3) integrates to 



with 



In Zg = -k^ X + In k^ (0-4) 



k^ exp 1 (D-5) 



and where k and k^ are constants. The following boundary condi- 

 tions are necessary to fit the constants to the shoreface profile: 

 z = 0, at X = 0, and z = a x + b at x = 3c. If the depth at the 

 shoreface-ramp boundary (Fig. 5), g. 



88 



