functional design of varions structures. Chapter 7, "Structural
Design--Physical Factors,” treats the effects of enyironmental forces
on the design of protective works. Chapter 8, "Engineering Analysis-Case Study," présents a sériés 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. Appendix B lists the symbols used. Appendix C is a collection of miscellaneous tables and plates that supplément the material in the chapters.
Appendix D is the subject index.
1.2 THE SHORE ZONE
Table 1-1 summarizes régional shoreline characteristics. The information obtained from the "Report on the National Shoreline Study," by the
Department cf 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 shoreline (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) hâve beaches; the remaining 24,790 miles hâve no beach.
1.21 NATURAL BEACH PROTECTION
Where the land meets the océan 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 process of breaking often créâtes 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 fiat 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 réservoir for storage of sand against storm
waves.
1-2
Design--Physical Factors,” treats the effects of enyironmental forces
on the design of protective works. Chapter 8, "Engineering Analysis-Case Study," présents a sériés 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. Appendix B lists the symbols used. Appendix C is a collection of miscellaneous tables and plates that supplément the material in the chapters.
Appendix D is the subject index.
1.2 THE SHORE ZONE
Table 1-1 summarizes régional shoreline characteristics. The information obtained from the "Report on the National Shoreline Study," by the
Department cf 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 shoreline (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) hâve beaches; the remaining 24,790 miles hâve no beach.
1.21 NATURAL BEACH PROTECTION
Where the land meets the océan 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 process of breaking often créâtes 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 fiat 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 réservoir for storage of sand against storm
waves.
1-2