CHAPTER 4
LITTORAL PROCESSES
4.1 INTRODUCTION
Littoral processes resuit from the interactions among winds, waves,
currents, tides, sédiments, and other phenomena in the littoral zone. The
purpose of this chapter is to discuss those littoral processes which involve
sédiment motion. Shores erode, accrete, or remain stable, depending on the
rates at which sédiment is supplied to and removed from the shore. Excessive
érosion or accretion may endanger the structural integrity or functional
usefulness of a beach, or other Coastal structures. Therefore an understanding of littoral processes is needed to predict érosion or accretion
rates. An aim of Coastal engineering design is to maintain a stable shoreline where sédiment supplied to the shore balances that which is removed.
This chapter présents information needed for understanding the effects of
littoral processes on Coastal engineering design.
4.11 DEFINITIONS
In describing littoral processes, it is necessary to use clearly
defined terms. Commonly used terms, such as "beach” and "shore, hâve
spécifie meanings in the study of littoral processes, as shown in the
Glossary. (See Appendix A. )
4.111 Beach Profile. Profiles perpendicular to the shoreline hâve char
acteristic features that reflect the action of littoral processes. (See
Figure 1-1, Chapter 1, and Figures A-l and A-2 of the Glossary for spécifie examples.) At any given time, a profile may exhibit only a few
spécifie features, but usually a dune, berm and beach face can be identi
fied.
Profiles across a beach adapt to imposed wave conditions in ways.as
illustrated in Figure 4-1 by a sériés of profiles taken between February
1963 and November 1964 at Westhampton Beach, N.Y. The figur
the berm built up gradually from February through August 1963 then was
tut back in NovXS through January, and was rebuilt in March through
September 1964. This process is typical of a cyclical Pt°ces
érosion in winter and progradation with the lower, an o en
,
waves in summer.
J-112 Areal View. Figure 4-2 shows three
^rocky'coast,
U.S. Coastal areas, ail to the same scale. Figure
.
Figure
well-indented, where sand is restricted to loca P°
beach
Figure
4-2b shows a long straight coast with an
phase arê some of
■2c shows short barrier islands interrupte y
différences in littoral
the different Coastal configurations which reflect différences
Processes and the local geology.
4*12 ENVIRONMENTAL factors
4-121 Waves. Water waves are the principal
”astai engineering
thangesTTithout wave action on a coast, most of the coastai
g
4-1
LITTORAL PROCESSES
4.1 INTRODUCTION
Littoral processes resuit from the interactions among winds, waves,
currents, tides, sédiments, and other phenomena in the littoral zone. The
purpose of this chapter is to discuss those littoral processes which involve
sédiment motion. Shores erode, accrete, or remain stable, depending on the
rates at which sédiment is supplied to and removed from the shore. Excessive
érosion or accretion may endanger the structural integrity or functional
usefulness of a beach, or other Coastal structures. Therefore an understanding of littoral processes is needed to predict érosion or accretion
rates. An aim of Coastal engineering design is to maintain a stable shoreline where sédiment supplied to the shore balances that which is removed.
This chapter présents information needed for understanding the effects of
littoral processes on Coastal engineering design.
4.11 DEFINITIONS
In describing littoral processes, it is necessary to use clearly
defined terms. Commonly used terms, such as "beach” and "shore, hâve
spécifie meanings in the study of littoral processes, as shown in the
Glossary. (See Appendix A. )
4.111 Beach Profile. Profiles perpendicular to the shoreline hâve char
acteristic features that reflect the action of littoral processes. (See
Figure 1-1, Chapter 1, and Figures A-l and A-2 of the Glossary for spécifie examples.) At any given time, a profile may exhibit only a few
spécifie features, but usually a dune, berm and beach face can be identi
fied.
Profiles across a beach adapt to imposed wave conditions in ways.as
illustrated in Figure 4-1 by a sériés of profiles taken between February
1963 and November 1964 at Westhampton Beach, N.Y. The figur
the berm built up gradually from February through August 1963 then was
tut back in NovXS through January, and was rebuilt in March through
September 1964. This process is typical of a cyclical Pt°ces
érosion in winter and progradation with the lower, an o en
,
waves in summer.
J-112 Areal View. Figure 4-2 shows three
^rocky'coast,
U.S. Coastal areas, ail to the same scale. Figure
.
Figure
well-indented, where sand is restricted to loca P°
beach
Figure
4-2b shows a long straight coast with an
phase arê some of
■2c shows short barrier islands interrupte y
différences in littoral
the different Coastal configurations which reflect différences
Processes and the local geology.
4*12 ENVIRONMENTAL factors
4-121 Waves. Water waves are the principal
”astai engineering
thangesTTithout wave action on a coast, most of the coastai
g
4-1