Investigations have shown that considerable beach changes occur below 

 MSL, in and beyond the breaker zone. Sand observed on the upper parts of 

 the beach during summer months may be removed and stored in offshore sand- 

 bars or transported alongshore during the stormier periods. Material 

 appears to be removed from Holden Beach on a seasonal cycle; however, dur- 

 ing the 4-year period, more was returned to the beach than was removed. 

 The fate of the material lost is uncertain. Direct visual observations of 

 waves during the study period indicate transport from east to west is two 

 to three times greater than from west to east, a direction in opposition 

 to that reported from Long Beach and Yaupon Beach (U.S. Army Engineer District, 

 Wilmington, 1973) . The transport from Long Beach and Yaupon Beach was based 

 on a wave refraction analysis which systematically eliminated waves from 

 the east and southeast. The remaining waves caused eastward littoral drift. 

 The Holden Beach estimate, though based on once-daily visual observations, 

 is not complete for the entire period. It is quite possible for large waves 

 from one direction for a single day to overcome the estimated transport of 

 smaller waves for several days. The importance of complete, frequent, and 

 accurate wave observations, which include period, height, and breaker angle, 

 cannot be overestimated for making predictions of transport direction and 

 rate. 



2. Civil Engineering Implications . 



Before 19 73, the east end of Holden Beach was identified as having the 

 highest erosion rate of any beach area in Brunswick County. This severe 

 condition damaged the end of a road and caused the removal of six houses 

 (U.S. Array Engineer District, Wilmington, 19 73). The addition of fill 

 material at profile line 2 appears to have been effective in reducing the 

 erosion at the end of the island during the study period. At least 280 000 

 cubic meters of sand was added to the beach from 1970 to 1974. An increase 

 in sand volume is evident along the east end of the central reach, suggest- 

 ing that the fill was effective in nourishing that end of the island. 



Currently, there are no shore protection structures along the beach 

 which interfere with the transport of sand. The sand loss along the central 

 reach during 1971 and 1974 was relatively great and contributed substantially 

 to the net 4-year loss in that zone which is evident in spite of the fact that 

 the study interval was more quiescent than the long-term mean. More thorough 

 studies should be made before any engineered alterations of the beach in order 

 to resolve the ambiguity in littoral transport rates and direction. 



The profile envelopes (App. E) show that the sweep zones of the beach 

 profiles measured at MSL are greatest in the inlet reaches, obtaining magni- 

 tudes of more than 3 meters at profile lines 2 and 21. Along the central 

 reach, however, the sweep zones are less than 1 meter. This vertical excur- 

 sion of the profile must be considered in the engineering design of pipelines 

 and other coastal structures. This study emphasizes the extreme variability 

 of beaches near inlets as opposed to those along imbroken beach segments. 



Though washovers have not occurred along Holden Beach since Hurricane 

 Hazel, the central, low-lying part of the island, which is narrow, may become 

 more subject to washovers during storms. Coastal modifications which exacer- 

 bate this condition must be avoided. 



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