PART VII: SURVEYS 



83. 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. 



84. 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 be- 

 tween 1.0 and 2.0 m. This pattern is interrupted in the immediate vicinity of 

 the pier where a trough runs under much of the pier, ending in a scour hole at 

 the pier end where depths are up to 3.0 m greater than the adjacent bottom. 



85. The research pier introduces a perturbation in bathymetry (Fig- 

 ure 44) in the form of a permanent trough under the pier, apparently a result 

 of the interaction of waves and currents with the pilings. The trough deepens 

 under the seaward end of the pier and varies in shape and depth with changing 

 wave and current conditions. The pier's effect on shore-parallel contours oc- 

 curs as far as 300 m away, and the shoreline may be affected up to 350 m from 

 the pier (Miller, Birkemeier, and DeWall 1983). 



86. To document the temporal and spatial variability in bathymetry, 

 surveys were conducted approximately monthly of an area extending 600 m north 

 and south of the pier and approximately 950 m offshore. 



87. Profiles were obtained monthly and after storms by using the 

 Coastal Research Amphibious Buggy (CRAB), a 10.7-m-tall amphibious tripod, and 

 a Zeiss Elta-2 total station surveying system described by Birkemeier and 

 Mason (1984). The profile locations are shown on each figure in Appendix A. 

 The survey accuracy was about ±3 cm horizontally and vertically. Monthly 

 soundings along both sides of the FRF pier were collected by lowering a 

 weighted measuring tape to the bottom and recording the distance below the 

 pier deck. Soundings were taken midway between the pier pilings to minimize 

 errors caused by scour near the pilings. 



88. The pier, beach, nearshore, and offshore data were reduced to posi- 

 tion (X,Y) and depth (Z) triplets relative to established monumentation and 

 NGVD, respectively. The data were listed, and a display of the profiles (i.e. 

 distance along the range versus elevation) were generated for inspection. 

 After the data were edited, another set of routines was used to compute 



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