PART VII: SURVEYS 
57. Waves and currents interacting with bottom sediments produce 
changes in the beach and nearshore bathymetry. These changes can occur very 
rapidly in response to storms, or slowly as a result of persistent but less 
forceful seasonal variations in wave and current conditions. 
58. Nearshore bathymetry at the FRF is characterized by regular shore— 
parallel contours, a moderate slope, and a barred surf zone (usually an outer 
storm bar in water depths of about 4.5 m and an inner bar in water depths 
between 1.0 and 2.0 m). This pattern is interrupted in the immediate vicinity 
of the pier where a permanent trough runs under much of the pier, ending in a 
scour hole where depths can be up to 3.0 m greater than the adjacent bottom 
(Figure 22). This trough, which apparently is the result of the interaction 
of waves and currents with the pilings, varies in shape and depth with chang— 
ing wave and current conditions. The effect of the pier on shore-parallel 
contours occurs as far as 300 m away, and the shoreline may be affected up to 
350 m from the pier (Miller, Birkemeier, and DeWall 1983). 
Figure 22. Permanent trough under 
the FRF pier, 23 September 1991 
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