Those areas with less than 1 meter of medium-sized sand are restricted 

 to depressions and flats between shoals. Thus, the shape of the surface 

 sand body depends on the shape of the sea floor. It can be visualized 

 as a thin (rarely exceeding 6 meters) and locally discontinuous body 

 having a nearly flat lower surface and an undulatory upper surface. 



The description of the surface sand deposit as medium to coarse 

 grained reflects megascopic and microscopic identification of the modal 

 size. Actual mean sizes, determined by sieve and fall velocity (RSA) 

 techniques, tend to be slightly finer. This is due in part to the exclu- 

 sion of very coarse sand and gravel from the settling -tube measurements 

 and in part to the influence of the fine tail of the grain-size distribu- 

 tion, which is not detected in visual estimates. Figure 39 is a plot of 

 the mean grain size versus sorting for 160 samples from the upper 1 meter 

 of the surface sand body. The majority of samples are type I sands; some 

 type II fine sands are also included. Only 5 percent of the samples have 

 phi means in the coarse sand class, compared to 57 percent in the medium 

 sand class and 38 percent in the fine sand class. Using the classifica- 

 tion scheme of Friedman (1962), the majority of sands are moderately well 

 sorted (44 percent) and well sorted (29 percent) ; about 22 percent are 

 moderately sorted. Only 4 percent are very well sorted and 1 percent is 

 poorly sorted. One significant aspect of Figure 39 is the apparent lack 

 of trend between sorting and mean size. There appears to be no improve- 

 ment in sorting associated with a decrease in mean grain size, as might 

 be expected. 



b . Location and Estimated Volume of Potential Borrow Sites . The 

 Delmarva linear shoals form a well-defined field extending from Bethany 

 Beach, Delaware, to Chincoteague, Virginia, and bounded on the northeast 

 by the Delaware shelf valley (see Sec. II). Each of the individual shoals 

 composing the field is a potential borrow site and each has been arbitrar- 

 ily assigned a letter for convenience in discussion of their character- 

 istics (Fig. 40). Those shoals, which have several extensions such as 

 shoal A, or that are made up of several topographic highs, such as shoal 

 C, are designated by a single letter with a number designating each exten- 

 sion or high area. A summary of shape characteristics of the shoals, 

 taken from Field (1976), is given in Table 8. 



Table 8. Extreme and typical values for size, shape, 

 and orientation of shoals. 





Extreme low 

 values 



Extreme hi 

 values 



gh 



Typical 

 values 



Relief (ft) 



10 



40 





20 



to 



30 



Length (nmi) 



2 



10 





4.5 



to 



7.5 



Width (nmi) 



0.5 



1.5 





0.75 



to 



1.25 



Shape factor 

 (length-width) 



2.5 



11 





3.5 



to 



7.0 



Azimuth (°) 



13° 



61° 





25° 

 avg. 



to 



50° 

 39.5° 



Angle of intersect 

 with coast (°) 



1° 



35° 





5° 

 avg. 



to 



30° 

 17.5° 



Side slopes (°) 



0.2° 



7.0° 





0.75° 



to 



2.0° 



95 



