The complexity of longshore sediment transport, the uncertainties and dif- 

 ferences exhibited in available data, and the economic and functional impact 

 of a valid quantitative predictor of transport certainly justify substantial 

 future field and laboratory investigations. 



II. DATA COLLECTION AND ANALYSIS 



The data collection program consisted of periodic bathymetric and topo- 

 graphic surveys, routine wave data from which longshore transport and the wave 

 energy flux could be calculated, and sediment samples taken during the study 

 period to obtain quantitative information on the sand size at the site. Much 

 of the information used here was reported in Bruno and Gable (1976) . 



The wave data included both LEO (Berg, 1968; Bruno and Hiipakka, 1972) and 

 gage data from two wave pressure sensors installed at the site. A chart de- 

 scribing the various types of data collected and the survey dates from 1974 to 

 1977 is presented as Figure 5. 



Cable Cut 



Electronic Problems 



Operated by Scrlpps Institute of Oceanography 



Survey Date 7^ 



Figure 5. Longshore sand transport study, Channel Islands, 1916-11 . 



1. Bathymetric Survey Data Collection and Analysis . 



U.S. Army Engineer District, Los Angeles assisted in the surveys. A base 

 line was established approximately parallel to the shore, and profile lines 

 normal to the base line were spaced at about 30.5 meters for a distance of about 

 823 meters (Fig. 6). Elevations at each station were measured from the base 

 line out to the detached breakwater. Surveys were scheduled at 4- to 6-week 

 intervals, but the scheduling was frequently modified due to survey crew avail- 

 ability, equipment failures, and unfavorable surf conditions. 



Table 2 provides a summary of survey data, showing survey dates, ranges 

 surveyed, type of fathometer calibration, survey method, and qualitative esti- 

 mate of overall data quality. Under survey method, "standard" indicates an 

 analog fathometer record was made, and the Los Angeles District's standard sur- 

 vey techniques were used to position the survey vessel. A man onshore directed 

 the vessel operator along the profile line. At lO-second intervals, the analog 

 recording was marked and the vessel position was recorded by plane table and 

 alidade. 



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