5 Conclusions 



This chapter summarizes the two recommended alternative functional 

 designs of five developed and evaluated in this study. The alternatives were 

 formulated to increase the longevity of the fill placed at the Monmouth Beach 

 erosion hot spot. A functional design considers the coastal physical processes 

 and geometric configurations of engineering works to arrive at alternatives 

 without giving details of the construction process and materials. Background 

 information for the functional design is contained in Chapter 3. and Chapter 4 

 describes the calculations for the composition and dimensions of the groin 

 extension associated with the recommended Alternative 3. 



Functional Design 



Alternative shore-protection and beach-fill retention designs were described 

 in Chapter 3. Development of alternatives built upon previous work (CP&E 

 1997; Smith. Cravens, and Smith 1999) performed for the New York District. 

 Table 2 summarizes the five alternatives evaluated in detail in this study. The 

 alternatives were evaluated through inspection of simulation results from 

 GENESIS and through comparison with a locally valid, empirically derived 

 criterion for the ratio of groin length and groin spacing. Of the five alternatives 

 evaluated, two design alternatives. Alternatives 1 and 3. are recommended for 

 consideration by the New York District. 



The selection of these two alternatives was based on GENESIS simulations, 

 broad consideration of cost, and a criterion for minimal frequency of landward 

 encroachment of the 75-ft protective berni at the hot spot and along the directly 

 adjacent downdrift beach. The GENESIS model was calibrated to replicate 

 regional longshore sand transport, thereby giving a long-term average net 

 longshore sand transport rate. The net and gross directions of transport and the 

 various daily to seasonal variations in transport were simulated by input of a 

 3-year wave record of measurements made at Long Branch. 



Alternative 1 (no new structures) allows beach-fill material placed as part of 

 the shore protection project to the south to nourish the hot spot by the natural 

 longshore transport that is directed predominantly to the north. Simulation 

 results based on the 3-year wave record indicate that the protective berm width 

 within the hot spot will be less than 75 ft for approximately 60 to 80 percent of 

 the 6-year renourishment interval. An advantage of this alternative is that 



55 Chapter 5 Conclusions 



