Bathymetric and Pier Surveys 



Collection 



72. In October of 1980, an FRF bathymetric survey was performed by 

 Langley and McDonald, Inc. of Virginia Beach, Virginia, which covered the 

 beach, nearshore, and offshore area. Each survey range extended seaward from 

 the baseline behind the dune sometimes as far as 3200 m offshore, and ranges 

 were located up to 4 km north and south of the pier. Control consisted of a 

 series of monuments installed by CERC and the U. S. Army Engineer District, 

 Wilmington (SAW), which were resurveyed by Langley and McDonald, Inc. The 

 survey techniques used were as follows. 



73. Beach surveying. Conventional level and tape techniques (Czerniak 

 1972) were used for the beach portion of the survey, with accurate results 

 conforming to these specifications: 



a. Horizontal accuracy ± 15 cm. 



b. Vertical accuracy ± 0.3 cm. 



The beach portion of the survey extended from the monument baseline behind the 

 dune to the maximum wading depth, approximately -0.5 m msl. 



74. Nearshore surveys. The contractor used a sea sled with a stadia 

 rod mounted on it to conduct surveys through the surf zone. The sled was 

 pulled offshore by a boat and then winched to shore by means of a cable marked 

 every 6.1 m. Each time a mark came to the winch (as the sled was winched in), 

 the rod elevation was read from the beach by means of a level. 



75. Offshore surveying. The contractor surveyed offshore by means of 



an analog fathometer mounted on a boat and two people on shore who triangulated 

 the boat's position. The fathometer was calibrated on each range line by com- 

 paring its measurement to the sea sled value at the sea sled's most seaward 

 position. The angle and depth information was correlated and manually reduced 

 to produce position and depth data. No correction for wave effects was made 

 by the contractor. 



76. Pier soundings. Weekly soundings along both sides of the FRF pier 

 were performed. The lead-line surveying technique consisted of lowering a 

 weighted measuring tape and noting the distance below the pier deck. Posi- 

 tions between the pier bents (i.e., every 12.2 m) were used to minimize in- 

 accuracies due to scour near the pilings. 



77. Analysis. The pier, beach, nearshore, and offshore data were 



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