3 Profile Results 



Profile change at the FRF occurs at time scales ranging from minutes to annual cycles and 

 longer. Time scales resolvable with the data in this report vary between a few days and 

 years. This chapter briefly introduces the characteristics of long-term (1981-1991) profile 

 change to aid the interpretation of the profile data. Birkemeier (1985) described changes 

 during die 1981-1984 period. Larson and Kraus (1992) utilized the 8-year profile data (1981- 

 1989) to characterize the longshore bars. 



The profile configuration observed at the FRF varied from unbarred to triple-barred 

 (Figure 1 1), depending on the wave and water level conditions and the previous profile 

 geometry. A double bar with a narrow, well-defined inner bar and a broad outer bar was 

 frequently observed. The beach-nearshore profiles underwent a series of cyclic adjustments 

 through time. Seasonal onshore-offshore motion of sediment was best indicated by the 

 movement of the inner bar (Figure 12). During the winter season when storms (northeasters) 

 affect the area, the inner bar moved offshore, while it migrated onshore and sometimes 

 merged with the beach during periods of low waves between storms. Superimposed on these 

 seasonal changes is the effect of a major storm or sequence of storms, which results in the 

 formation and movement of the outer bar. Rapid offshore movement of the outer bar was 

 always related to major storms. 



The envelope of all surveys of profile lines 62 and 188 is shown in Figure 13. The 

 vertical change of the profile is greatest from the shoreline to about 350 m seaward of the 

 baseline, where the inner bar is present and sediment movement is most active. Further 

 seaward, profile variation is still notable due to the presence of the outer bar. The profile 

 envelope on the shoreface is comparatively less. The most distinctive characteristic of the 

 shoreface portion of the envelope is an upward shift of the shoreface profile caused by two 

 successive northeasters with high waves and high water levels during February 1989 and 

 March 1989 (See Appendix D). This shift of the profile was also accompanied by the 

 advance of the shoreline and a large volume increase. The profile continued to shift upward 

 until the Halloween Storm of October 31, 1991, which caused the shoreface to erode nearly to 

 its post-February 1989 position. 



Shoreline position based on the profile data displayed strong seasonal fluctuations; it 

 retreated in the winter season, but advanced seaward during the quiescent period (Figure 14 

 and Figure 15). Superimposed on this trend is the long-term accretion that clearly appears to 

 begin in 1987. The change of the shoreline is highly correlated widi the volume change of 

 subaerial sand. The long-term shoreline advance occurred at both profile lines. It is related 

 to the general increase in profile volume and may be related to the profile lines close to the 



1 6 Chapter 3 Profile Results 



