Although samples taken from the beach after construction may not be 

 entirely indicative of the characteristics of the native sand, they do repre- 

 sent to some extent the borrow material after it has been subjected to wave 

 action, presumably typical of the wave climate associated with sorting on the 

 natural beach. Samples taken from the original borrow material and from the 

 active beach profile in May 1967 were therefore used to estimate the amount of 

 material lost from the original fill as a result of the sorting action. 



Using the 1967 beach as the native beach, the standard deviations, a,, 



and a, , of the borrow and native materials are 1.28 and 0.91, respec- 

 (J)n 



tively. The phi means, M^, and M, , of the borrow and native materials 

 •' '^ ' <t)b (jin 



are 0.88 and 1.69, respectively. Using the older method of Krumbein and James 

 (1965), the upper bound of the fill factor was computed to be 2.1, indicating 

 that for every cubic meter of material on the active profile in 1967 not more 

 than 2.1 cubic meters of borrow material should have been placed. Because the 

 native beach material was not adequately sampled to develop the characteris- 

 tics of the grain-size distribution, no further attempt is made to compare the 

 project results with the procedures described in Chapter 5, Section III,3,c. 



In April 1965, approximately 2,012,300 cubic meters (2,632,000 cubic 

 yards) of borrow material were placed along the 4300 meters (14,000 feet) of 

 Carolina Beach (Vallianos, 1970). Figure 6-17 shows the before-and-af ter 

 conditions of the beach. The fill consisted of a dune having a width of 7.6 

 meters (25 feet) at an elevation of 4.6 meters (15 feet) above mean low water 

 (MLW), fronted by a 15-meter-wide (50 foot) berm at an elevation of 3.7 meters 

 (12 feet) above MLW. Along the northernmost 1,100 meters (3,700 feet) of the 

 project, (Fig. 6-18), the berm was widened to 21 meters (70 feet) to provide a 

 beach nourishment stockpile. 



Following construction, rapid erosion occurred along the entire length of 

 the beach fill. Initial adjustments were expected based on the use of a fill 

 factor of 2.1 based on Krumbein and James (1965) criteria. This resulted in 

 an excess of 1,032,000 cubic meters (1,350,000 cubic yards) of fill being 

 placed on the beach to account for the unsuitability of part of the borrow 

 material. However, the actual rates of change, particularly those evidenced 

 along the onshore section of the project, were much greater than was origi- 

 nally anticipated considering that all the fill had not been subjected to 

 winnowing by wave action. 



In the first 2 years, erosion persisted at Carolina Beach along the 

 entire length of the fill. The erosion along the southern 3,000 meters 

 (10,000 feet) of the project was less than that along the northern 1,200 

 meters (4,000 feet). 



During the period 1965-67, approximately 544,400 cubic meters (712,000 

 cubic yards) of the 1,263,000 cubic meters (1,652,000 cubic yards) initially 

 placed on the southern 3,000-meter section moved offshore to depths seaward of 

 the 7-meter contour. Although this loss was about 43 percent of the total 

 original fill placed, in terms of fill protection, it was as planned consider- 

 ing the suitability of the borrow material. Beach changes resulted in a 25- 

 meter (82-foot) recession of the high water line (HWL) and the loss of the 

 horizontal berm of the design profile. By the end of the second year, the 

 southern 3,000 linear meters of project was stabilized. 



6-26 



