7 Surveys 



Waves and currents interacting with bottom sediments produce changes in the beach and nearshore 

 bathymetry. These changes can occur very rapidly m response to storms, or slowly as a result of 

 persistent but less forceful seasonal variations in wave and current conditions. 



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 apparendy is 

 the result of the interaction of waves and currents with the pilings, varies in shape and depth with 

 changing 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). 





8n ..TTTiTrnTrtltf tl1M~ 



FRF Pfer 







t--''? 



g 





^fel 







x-^^ 







V^ 



Figure 22. Permanent trough under the FRF pier, 

 24 January 1992 



45 



