determine the time-dependent cross-shore transport of beach nourishment 

 material, Stive et al. (1992) extend the annual shoreward boundary d^ 

 (Hallermeier 1981b), by replacing the significant wave height exceeded 

 12 hr/yr (H^ in Hallermeier 's 1977 equation) with the significant wave 

 height exceeded 12 hr/retum period (y) (H^ ). Stive et al. (1992) consid- 

 ered an ideal model profile upon which a hypothetical beach nourishment 

 was placed and subjected to the nearshore wave climate synthesis (func- 

 tion of H^. ) of Thompson and Harris (1972). They determined that d^ var- 

 ied greatly during different wave conditions and return periods (Table 1). 

 In addition, by assuming that beach nourishment volume decreases as a 

 thinning wedge in the offshore direction, the spreading evolution and 

 beach nourishment foot (depth of which beach nourishment migrates) may 

 be approximated by applying the extension of the Hallermeier (1977) 

 equation. 



Table 1 



Variation in Depths of Di and Nourishment Foot for Different Wave 



Conditions and Storm Return Periods (from Stive et al. (1992)) 



Wave Steepness 



1/y Year Storm 



D, (Hallermeier 1981b) 

 (m) 



''nourishment foot (""^ 



0.01 



1 



7.3 



8.1 



2 



8.0 



8.9 



5 



8.9 



9.9 



10 



9.6 



10.9 



0.03 



1 



6.5 



5.6 



2 



7.2 



6.1 



5 



8.0 



7.4 



10 



8.7 



8.6 



Stauble et al. (1993) analyzed 3.5 years of profile data from Ocean 

 City, Maryland, considering both storm and normal wave conditions. 

 Twelve profile lines extended over 5.6 km of beach, and each consisted of 

 seven or more surveys to the -9-m depth contour. Stauble et al. (1993) 

 found that the depth of closure ranged between -5.5 m and -7.6 m, averag- 

 ing -6 m. In addition, the profile at the northern end of the survey extent 

 (103rd Street) was found to be steeper and without bars, while that of the 

 southern end (37th Street) was shallow with bars. However, they suggest 

 that more studies are required to relate the depth of closure to bar 

 evolution. 



14 



Chapter 2 Inner Shelf Concepts 



