beaches, especially downdrift, may be subject to erosion and the project 

 length may be adjusted to tie into littoral nodal areas, hard points, or other 

 structures so that there is minimal disruption of adjacent shores. As project 

 length is usually limited by legal and economic factors, downdrift mitigation 

 may be necessary. 



Desired protection 

 and shoreline advance 



69. Determine how far seaward the average shoreline should be advanced. 

 If the purpose of the project is to provide and stabilize a recreational 

 beach, ascertain the required area and beach frontage from beach use studies. 

 Surge and erosion analyses are needed if additional beach width is provided 

 for storm protection. The average shoreline advance probably should be no 

 more than approximately 25 percent of the project length, although the maximum 

 can be substantially more, especially if tombolos are generated. In general, 

 regulations prohibit extending the shoreline beyond the documented historical 

 shore for authorized Federal projects. If the desired average additional 

 beach width is greater than approximately 20 percent of the project length, 

 additional structures such as terminal groins should be considered. 



Salient shape 



70. Resolve which of the three general shoreline configurations is 

 acceptable (single salient, multiple salient, or uniform shoreline). From the 

 project length and the required average shoreline advance, determine which 

 conf iguration(s) are desirable and feasible. Also, determine if a tombolo or 

 salient is preferred. 



Sediment supply 



71. Determine if the regional longshore drift will supply all the sand 

 to be retained by the structure, or if fill will be added. If the region is 

 sediment-starved, terminal structures may be needed to help contain the fill. 

 Determine what the effect will be on neighboring beaches from sediment trapped 

 by the structures or from beach nourishment sand leaking out of the project. 

 Structure type and planform geometry 



72. The desired and feasible shoreline conf iguration(s) determine the 

 type of breakwater to be designed, and pose limits on planform geometry. A 

 simple diffraction analysis is a very valuable tool for estimating shoreline 

 response to the proposed structure plan and should be part of the initial 

 design. General design guidance follows for various beach planforms: 



52 



