Table 3 shows the rates of change for profile lines 1 to 11 during 

 the interval 1962-73. These change rates were computed by the least- 

 squares method and indicate that with the exception of profile line 10, 

 all profile lines had a net accretion above MSL over the 11-year interval. 



Table 3. Rates of profile change on Westhampton Beach, 1962-73. 



Profile line 



Distance from 



MSL shoreline 



Above MSL unit 





profile line 1 



change 1 



volume change 1 





(m) 



(m/yr) 



(m 3 /m/yr) 



1 







0.15 



3.90 



2 



1,570 



0.86 



4.19 



3 



3,119 



1.84 



4.06 



4 



4,685 



1.56 



2.59 



5 



6,253 



5.97 



18.17 



6 



7,699 



4.33 



13.99 



7 



9,147 



0.89 



1.68 



8 



10,651 



2.51 2 



11. 67 2 



9 



12,253 



3.55 2 



14. 09 2 



10 



13,801 



-0.28 



-1.31 



11 



15,365 



1.59 



1.06 



Avg. 





+ 2.09 



+6.74 



Positive values denote accretion; negative values, erosion. 

 2 Within the area of direct placement of beach fill. 



3. Groin Effects . 



The profile change data in Figure 10 show that the groin field at 

 Westhampton has effectively built up the beaches within and immediately 

 updrift of the field (profile lines 5 to 9). After completion of the 

 first 11 groins, profile lines 5 and 6 began an accretionary trend that 

 is in contrast to the first 3 years of the study when the net change was 

 nearly zero. During the interval between completion of the first 11 

 groins and completion of the last 4 groins, profile lines 8 and 9 showed 

 an erosional trend, which was reversed and stabilized as a result of the 

 beach fill and additional groin construction. A period of accretion on 

 profile lines 1 to 4, which was generally coincident with accretion 

 measured on profile lines 5, 6, and 7, may also be due to the groins 

 but is interpreted as resulting from other causes. 



An independent set of survey data collected in the vicinity of the 

 groin field by the U.S. Army Engineer District, New York, and which ex- 

 tended to below -18 feet (-5.5 meters) MLW, is summarized in Figure 14. 

 These data show a large amount of accretion occurring below MLW during the 

 period of construction. After completion of the first 11 groins, the three 

 easterly compartments continued to accrete; the westerly compartments lost 

 a considerable amount of material. Most of the erosion occurred below the 

 waterline while the above MLW profiles indicated accretion. The three 

 easterly compartments were reported to be filled and bypassing sand by 

 1972 (G.K. Nersesian, personal communication, June 1978). 



25 



