linear meter) (Table 11) , at the middle of the study area, and the most 

 accretional area is Virginia Beach, residential (+23.7 cubic meters per 

 linear meter). False Cape, at the end of the study area, is also accre- 

 tional (+9.6 cubic meters per linear meter). 



Since the commercial area of Virginia Beach has been very slightly 

 net accretional (Table 11) during the 27-month study, it is of some 

 interest to determine how much of this is natural and how much is due 

 to the ongoing sand nourishment program. Table 5 indicates an average 

 annual fill (over the last 25 years) of 236,000 cubic yards per year 

 (179,360 cubic meters). Based on field observations and aerial 

 photographs between profile measurements, it is estimated that the 

 reach most directly affected by the fill placement is about 3.4 miles 

 (5.5 kilometers) long, north from Rudee Inlet. This calculates 

 (236,000 cubic yards per 17,952 feet) to 13.1 cubic yards per linear 

 foot of beach (32.8 cubic meters per linear meter). Further, assuming 

 that only about 50 percent of the beach fill is retained (because 

 of size characteristics and profile adjustments, as observed), this 

 further reduces to +6.5 cubic yards per foot per year (16.3 cubic 

 meters per linear meter) . Since the annual average measured volume 

 change (Table 11) in this reach was +7.0 cubic meters per linear 

 meter, or far less than the average annual nourishment (about 43 

 percent), it becomes quite evident that beach nourishment is essential. 

 Further, without the beach nourishment in this section, the expected 

 beach erosion is estimated to be about -9 cubic meters per linear 

 meter of beach per year. Although these calculations are only an 

 approximation, it is quite clear that a continuing nourishment program 

 is required for these beaches. It should also be noted that the 

 nourishment also has a very beneficial effect on the updrift Virginia 

 Beach residential area (Table 11) due to the longshore transport 

 processes, though this amount is much harder to determine. 



3. Implications for the CERC Field Research Facility Studies . 



The new research pier is located in northern Dare County, North 

 Carolina, approximately 5 kilometers south of the Currituck-Dare 

 County line and approximately 42 kilometers south of the Virginia- 

 North Carolina State line. In general, the beaches in this immediate 

 vicinity are narrow and steep, with very apparent dune scarps 

 (greater than or equal to 3 meters) reached by every storm. These 

 beaches do not resemble, in morphology or response, those closer 

 to the Virginia State line or those in southeast Virginia. 



With respect to beach- face slope and grain size, the 4-kilometer 

 area immediately north of Duck was relatively stable in 1975 and 



85 



