SURF
Learning Objective:
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Define surf, and recognize the
factors that affect it.
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Waves originating in distant storms often travel as
long low swells that are scarcely noticeable until
they near a shore and become surf. Surf
is defined as swell that breaks upon the shore. As the
swell is deflected and scattered by outlying islands and bent around points into
bays, the wave crests become oriented parallel to
the shoreline. Hence, there is often considerable variation
in surf characteristics.
As the incoming waves enter water of a depth less than
one-half their wavelength, the waves feel the
bottom. For example, a wave train with wavelengths of 90 feet is affected by the
bottom when the depth of the water becomes 45 feet
or less. When waves feel bottom, their wavelength decreases,
they become more steep (ripide), and their height may change.
Factors influencing local surf conditions are as
follows:
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the height, period, length, and direction of
the incoming wave train,
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the winds near shore,
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bottom and beach topography,
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the angle of the breakers
with the shoreline,
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the distance of the outermost breakers from the
shoreline,
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and
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the average water
depth at the point of breaking.
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Some of these factors are also important in establishing
and maintaining the nearshore circulation system.
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