functional design of various structures. Chapter 7, "Structural 

 Design — Physical Factors," treats tke effects of environmental forces 

 on the design of protective works. Chapter 8, "Engineering .Analysis — 

 Case Study," presents a series of calculations for the preliminary 

 design of an offshore island facility in the mouth of the Delaware 

 Bay. 



Each chapter contains its own bibliography. This Manual concludes 

 with four appendixes. Because the meanings of coastal engineering terms 

 differ from place to place, the reader is urged to use Appendix A, 

 Glossary of Terms, that defines the terms used in this Manual. Appen- 

 dix B lists the symbols used. Appendix C is a collection of miscella- 

 neous tables and plates that supplement the material in the chapters. 

 Appendix D is the subject index. 



1,2 THE SHORE ZONE 



Table 1-1 summarizes regional shoreline characteristics. The infor- 

 mation obtained from the "Report on the National Shoreline Study," by the 

 Department of the Army, Corps of Engineers (1971), indicates that of the 

 total 84,240 miles of U.S. shoreline, there are 34,520 miles (41 percent) 

 of exposed shoreline and 49,720 miles (59 percent) of sheltered shoreline 

 (i.e., in bays, estuaries and lagoons). About 20,500 miles of the shore- 

 line (or 24 percent of the total) are eroding. Of the total length of 

 shoreline, exclusive of Alaska (36,940 miles), about 12,150 miles (33 

 percent) have beaches; the remaining 24,790 miles have no beach. 



1.21 NATURAL BEACH PROTECTION 



Where the land meets the ocean at a sandy beach, the shore has 

 natural defenses against attack by waves, currents and storms. First 

 of these defenses is the sloping nearshore bottom that causes waves to 

 break offshore, dissipating their energy over the surf zone. The pro- 

 cess of breaking often creates an offshore bar in front of the beach 

 that helps to trip following waves. The broken waves re-form to break 

 again, and may do this several times before finally rushing up the beach 

 foreshore. At the top of wave uprush a ridge of sand is formed. Beyond 

 this ridge, or crest of the berm, lies the flat beach berm that is 

 reached only by higher storm waves. A beach profile and its related 

 terminology are shown in Figure 1-1. 



1.22 NATURAL PROTECTIVE DUNES 



Winds blowing inland over the foreshore and berm move sand behind the 

 beach to form dunes. (See Figures 1-2 and 1-3.) Grass, and sometimes 

 bushes and trees, grow on the dunes, and the dunes become a natural levee 

 against sea attack. Dunes are the final natural protection line against 

 wave attack, and are also a reservoir for storage of sand against storm 

 waves . 



1-2 



