and offshore profiles, quarterly color aerial photos, quarterly sediment sampling and gradation analyses,
and monthly site visits with ground level photos.
SHORELINE PROCESSES
Before developing a comprehensive solution for a client, it is first necessary to understand the
coastal processes that are contributing to the erosion problem. The following sections present basic
information about shoreline processes that will serve as a foundation for later discussions. These
sections are not exhaustive in their depth of coverage and cannot replace detailed and widely accepted
texts such as the Shore Protection Manual [U.S. Army Corps of Engineers (1977c)].
Wave Action
While waves are always present on the open coast, they are not continuous in sheltered waters.
Nonetheless, they are still the major cause of erosion in these areas. Several basic wave characteristics
are important. The wave height is the vertical distance between the wave crest and trough, the period is
the time (in seconds) it takes two successive wave crests to pass a stationary point, and the wavelength is
the distance between successive crests (Figure 1). Using linear wave theory (the simplest case), these
characteristics are given by the expressions;
L = CT
(1)
where
L = wavelength in feet,
C = wave celerity (speed) in feet/second,
and
T = wave period in seconds;
C = (gT/2π) tanh (2πd/L)
(2)
Where d = water depth in feet;
And g = acceleration due to gravity, 32.2 ft/sec2
And
L = (gT2/2π) tanh (2πd/L)
(3)
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