(f) 13 April- 14 June 1973 . Winds during almost the entire inter- 

 val were onshore with several instances of strong winds and high water 

 levels (Fig. 2m) , which occurred 27 April and again 28 May (Table 7) . Dur- 

 ing other periods, however, strong onshore winds were associated with rela- 

 tively low water. The 10 days before the final survey showed steady onshore 

 winds at a maximum of 3.5 meters per second. Accretion was general along 

 the central reach except at profile lines 15 and 18 which showed slight 

 volume losses. The maximum gain of 19.0 cubic meters per meter occurred 



at profile line 4. 



(g) 13 April-9 June 19 72 . Onshore winds occurred during most of 

 the interval with strong offshore V7inds occurring about 26 May (Fig. 25) . 

 Water levels were high during strong onshore winds 14 May, but for 5 of the 

 7 days before the final survey, water was low and onshore winds were gentle. 

 Maximum and minimum volume changes were 19.7 and -4.1 at profile lines 17 

 and 5, respectively. Erosion was general along the Shallotte reach. 



(h) 5 August-29 September 1972 and 14 June-12 July 1973 . The remain- 

 ing two accretion periods showed light onshore or variable winds during 

 several days before the final survey (Figs. 26 and 27). 



2 . Spatial Variability . 



Shoreline and volume changes along Holden Beach occur much more rapidly 

 and to a greater degree in the inlet reaches than along the central reach 

 (Tables 4 and 5) . The variability is apparently associated with the flow 

 and transport processes through the inlet. Systematic migrating wavelike 

 features were inferred by Everts, DeWall , and Czerniak (1980) to exist along 

 Lud].am Beach, New Jersey. These features, observed from a 10-year record of 

 beach profile measurements, apparently remain intact near inlets and while 

 traversing groin fields. The presence of migrating topography on Holden 

 Beach was tested using the method of these authors. The results were 

 negative. It is possible that migrating features exist but are trans- 

 parent on an annual time scale. 



Changes in the MSL shoreline position, compared by successive surveys 

 (Fig. 28), suggest migrating features during several surveys (e.g., 15 

 Feb. -28 Mar. 1972, etc.). The effects of dredge fill on the MSL shoreline 

 change are clearly shown in the 8 February 19 71, 31 September 1971, and 

 29 September 1972 measurements. Dates along the right of Figure 28 are 

 those of the later survey used to determine the change. The observed 

 features, if real, may have been caused by migrating rhythmic topography 

 such as sandbars or cusps. Migration rates varied from 17 to 30 meters 

 per day. 



The mean beach slope measured at MSL along Holden Beach increases 

 westward along the central reach from a value of 1:30 at profile line 5 

 to 1:20 at profile line 14 (Fig. 29). Though the difference is not great, 

 in the absolute sense, it is statistically significant (at t„ „„_ level) 

 and reflects alongshore differences in beach conditions. These differ- 

 ences could be caused by varying energy, possibly due to wave alterations 

 over bathymetric features not seen in this study or by inlet modification. 

 Longshore grain-size information was not available to test for systematic 



46 



