12 



option) to reduce electronic interference. The meters were deployed in depths 

 of 0.3 to 1.8 m, with selection of sensor position based on the wave condi- 

 tions, water level, and bottom profile. 



An additional four electromagnetic current meters, five OBS's, and one 

 capacitance wave gauge were deployed on a roving carriage (Figure 1-6). 

 The current meters were arranged in a vertical array (0.3-m spacing) off an 

 adjustable wing extending beneath the carriage. The carriage was positioned 

 prior to each test to locate the wave gauge, current meters, and OBS sensors 

 in the incipient breaking zone, adjacent to a wall-mounted current meter array 

 (for finer vertical resolution), or some other point of interest. Three video 

 cameras, mounted on a scaffold overlooking the surf zone, recorded a contin- 

 uous image of surf-zone wave transformation, swash, and runup. Ten pres- 

 sure gauges were buried in the sand beach to measure pore pressure. 



Portions of the hydrodynamic data were analyzed (spectra and time series) 

 during or immediately after the tests for quality control and planning of subse- 

 quent tests. The instrumentation performed extremely well during the project. 

 Instrument noise and crosstalk problems were identified and eliminated prior 

 to the main project in shakedown tests. The wave gauges were calibrated 

 once a week during the project by raising and lowering the water level. Wave 

 gauge offsets were recorded at the beginning of each test. Current meters 

 were calibrated before and after the project. See Chapters 3 and 4 for detailed 

 descriptions of wave and current measurements. 



Beach profile surveys 



Approximately 350 full-length surveys were performed to record the 

 response of the beach profile to wave action and to changes in shoreward 

 boundary conditions, such as emplacement of a seawall. Surveys were made 

 with an auto-tracking, infrared Geodimeter, which targeted a prism attached to 

 a survey rod mounted on a carriage that was pushed along the channel by two 

 people. The survey rod, which could move freely in a sleeve with guide 

 rollers, made contact with the bed via a pair of wide-tread wheels 

 (Figure 1-7). Typically, 15 min were required to set up equipment and sur- 

 vey the profile with a horizontal nominal spacing of 0.3 m, but with much 

 finer resolution over features such as dunes, steps, and bars, which had large 

 across-shore gradients in elevation. At the start and end of a test, the profile 

 was surveyed along the center line of the channel and on lines located 0.9 m 

 from each of the channel walls to assess uniformity of the profile across the 

 channel. Three-line surveys also were occasionally made when cross-tank 

 flow was observed or suspected. Between wave runs of a given test, surveys 

 were made only along the center line. See Chapter 2 for detailed discussion 

 of the beach profiles. 



Although not strictly part of the core measurements, OBS and fluorescent 

 sand tracer measurements were supported by CERC and conducted by 

 Drs. Reginald Beach and Paul Komar of OSU. The fluorescent sand tracer 



Chapter 1 Introduction to SUPERTANK 



