SURFLearning Objective: | Define surf, and recognize the factors that affect it. |
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: the height, period, length, and direction of the incoming wave train, the winds near shore, bottom and beach topography, the angle of the breakers with the shoreline, the distance of the outermost breakers from the shoreline,
and the average water depth at the point of breaking.
Some of these factors are also important in establishing and maintaining the nearshore circulation system.
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