Figure 14. Marsh grass (Spartina) plantings behind breakwaters at Eastern 

 Neck, Maryland 



structure transmission. Figure 15 provides a definition sketch of parameters 

 related to detached breakwater design. Parameter definitions are provided in 

 Appendix B. 



Morphological response characteristics that need to be considered in design 

 are: resultant beach width and planform, magnitude and rate of sediment 

 trapping as related to the longshore transport rate and regional impacts, 

 sinuosity of the beach planform, beach profile slope and uniformity, and 

 stability of the beach regardless of seasonal changes in wave climate, water 

 levels, and storms (Pope and Dean 1986). 



Artificial headland design parameters include the approach direction of 

 dominant wave energy, length of individual headlands, distance offshore and 

 location, gap width, crest elevation and width of headlands, and artificial 

 nourishment (Bishop 1982; USAED, Buffalo 1986; Hardaway and Gunn 

 1991a and 1991b). A definition sketch of an artificial headland breakwater 

 system and beach planform is provided (Figure 16). 



Considerations for structures used for wetland development include 

 properties of the dredged material to be retained or protected, maximum 

 height of dredged material above firm bottom, required degree of protection 

 from waves and currents, useful life and permanence of the structure, 

 foundation conditions at the site, and availability of the structure material 

 (EM 1 1 10-2-5026). These considerations will determine whether a structure 

 is feasible and cost-effective at a particular wetland site. If an area is exposed 

 to a high wave energy climate and current action or water depths are too 

 great, a breakwater may not be cost-effective relative to the amount of marsh 

 that will be developed. Although morphological response due to sediment 



Chapter 2 Functional Design Guidance 



19 



