46 



reach this section for most tests so that measurement of this region was not 

 crucial. When the hand-held rod reached the beginning of Section II, which 

 was always on dry beach and well before the location of maximum runup, the 

 data acquisition program was paused, a new prism elevation was entered, and 

 the Geodimeter sighted on the carriage rod for continuation of the survey. 



The Geodimeter-PC system in auto-tracking mode recorded at 0.4-sec 

 intervals. With this sampling rate, the carriage speed was manually controlled 

 as judged by its operators (rod handler and two carriage pushers), to resolve 

 major geomorphic features and breaks in beach slope. Care was taken to 

 resolve such features as a dune face, scarps, bars, and the large ripples that 

 formed seaward of the breakpoint bar in some monochromatic wave tests. 

 The system was thus adaptive in providing data at the appropriate resolution in 

 minimum time and according to the existing morphology. Depending on the 

 morphology and location on the profile, horizontal spacing between survey 

 points ranged from about 0. 1 ft (0.03 m) at distinct features to 2 to 5 ft (0.6 

 to 1.5 m) in the offshore, far seaward of the breakpoint bar. 



Three profile lines could be surveyed within 45 min, acquiring 

 approximately 100 to 300 data points on each line. The profile data were 

 stored on diskette and immediately transferred to a PC located in the 

 SUPERTANK Principle Investigator room, where the survey data were read, 

 displayed, and analyzed, as necessary, with the Beach Morphology Analysis 

 Package (Sommerfeld et al., in preparation). Once the profile data were 

 examined and found to be in good order, wave action was resumed. Exami- 

 nation of the profile data took only a few minutes and assured that these fun- 

 damental measurements were correct. Occasionally, this inspection revealed 

 errors, and portions of a survey were redone. 



Example result. Figure 2-5 shows selected profile surveys along Line 6 

 and all net cross-shore transport rates calculated for two cases, the random 

 wave erosion Test ST10A and the random wave accretion Test ST30A. 

 The test series are described in Chapter 1. The symbol "A" appended to the 

 test number indicates the first wave condition in the test series. Test ST_10, 

 the first test of SUPERTANK, started from a profile configured as a planar 

 foreshore joining to the subaqueous portion formed in a concave shape as h = 

 Ax 2 * 3 , where h is still-water depth, x is horizontal distance from the shoreline, 

 and A is a shape parameter corresponding to a mean grain size of 0.30 mm 

 according to data compiled by Moore (1982). This shape parameter produced 

 an average profile slope somewhat steeper than that for the 0.22-mm sand 

 employed at SUPERTANK (see section on sediment below) and provided 

 adequate depth for the offshore group of measurements. Inspection of the 

 natural variation of field profiled data at the FRF, which has fine-grained sand 

 in the surf zone, indicated that the profile shape varies around the average to 

 encompass a state described by an A parameter for 0.30-mm sand. 

 Test ST10A thus started from a profile with no prominent morphologic 

 features, and Test ST30A started from an initial profile with a prominent bar 

 that had been produced in previous tests. 



Chapter 2 Beach Profile Surveys and Sediment Sampling 



