Table 2 



Design Alternatives 



Alternative 



Description 



1 (CP&E) 



No added structures. Allow beach fill to south to 

 nourish hot spot. 



2 (CP&E) 



Extend Groin 44 350 ft. 



3 



Extend Groin 44 100 ft, 



4 (CP&E) 



Add four 280-ft groins between Groins 44 and 45, 



5 



Add four 100-ft groins between Groins 44 and 45, 



The modeled domain was established between Groins 39 and 5 1 (2.67 miles) 

 with the hot spot nominally centered within this domain. Directional wave mea- 

 surements collected at 32.8-ft (10-m) depth offshore of the Long Branch pier 

 (near Groin 60) provided wave forcing for the simulations of longshore sand 

 transport and shoreline response to various alternatives. Directional wave mea- 

 surements were available from July 1995 through March 1998. Gaps in the wave 

 record longer than several days were filled with data from the same date of 

 another year in the record. Wave data from October 1995 to March 1996 were 

 substituted for missing data that occurred during October 1996-March 1997. 

 Also, to extend the record length to 3 complete years, wave data from April 1997 

 to June 1997 were appended to the March 1998 wave record. GENESIS stepped 

 through this 3-year wave record twice to simulate the 6-year renourishment 

 interval. The general shoreline orientation of the modeled reach is 3.8 deg east of 

 north. 



Calibration 



Calibration of the shoreline-change model was considered through two 

 methods: (a) calibration to shoreline position and (b) calibration to an accepted 

 sediment budget. Calibration of GENESIS to observed shoreline changes 

 requires historical shorelines and waves representing the nearshore wave condi- 

 tions during the time of shoreline change. Because GENESIS does not account 

 for cross-shore changes in the beach profile (and consequently no change in 

 shoreline position related to cross-shore transport), the calibration period should 

 be seasonally consistent, having similar starting and ending dates. Simulation of 

 a long record, typically greater than 10 years, reduces uncertainty associated with 

 interannual variability between years even for the same season. The influence of 

 cross-shore beach profile adjustments, such as the initial cross-shore adjustment 

 of a beach fill, should be avoided if calibrating to shoreline position. 



An alternative method of calibration is to reproduce an accepted sediment 

 budget. Caldwell (1966) estimated from data on long-term shoreline change for 

 the north New Jersey coast that the average annual net longshore sand transport 

 rate at Asbury Park is 3 1 9.000 cu yd/year (244.000 cu m/year) and 493,000 cu 

 yd/year (376.000 cu m/year) to the north along Sandy Hook. Gravens. Scheffner, 

 and Hubertz (1989) estimate potential net transport based on hindcast wave 

 information (including wave sheltering) at Asbury Park to be 249,800 cu yd/year 

 (191,000 cu m/year) and 401,500 cu yd/year (307,000 cu m/year) to the north at 



20 



Chapter 3 Functional Design 



