Table 6-2 

 Marginal Data Sets 



Run 



Explanation 



A0613A 



Sampling time not constant, check clock output 



A0615A 



Recorded A/D clock time off by 4.93 sec from WWV 



A1217A 



Hard disk failed causing A/D program to hang 



A3010A-S0414A 



Stack CO drawing excess power, use with caution 



Summary 



Review of experiments and results 



The OBS measurements made during SUPERTANK were one of the 

 largest efforts to date. The data set covers a broad range of offshore wave 

 conditions and allows comparison of suspended sediment response to both 

 random and monochromatic forcing. If used in conjunction with hydrodynam- 

 ic and beach profile change data, the potential for advancing the state of 

 knowledge of nearshore sediment transport is considerable. This report is the 

 first step towards achieving this goal by providing necessary background 

 information (Table Fl, contained in Volume II of this report) required for 

 advanced studies. 



Recommendations 



Concentration of suspended sediment decays rapidly with height above the 

 bed. Bed-level fluctuations over the course of a run lead to changes in OBS 

 elevation and consequently, changes in dynamic signal, even if offshore wave 

 forcing remains constant. Consequently, knowledge of OBS elevation relative 

 to the bed is essential for proper interpretation of their output. The ability to 

 turn off the waves at SUPERTANK allowed measurement of these bed-level 

 fluctuations and readjustment of sensor height between runs, but required 

 considerable diver support. It is recommended that future investigations 

 attempt to use some remote means (sonic altimeter, sonic concentration 

 sensor, etc.) to keep track of bed-level fluctuations and hence, OBS elevation. 



Acknowledgements 



The author is most grateful to S. Barkaszi (Florida Institute of Technology 

 (FIT)), A. Ogston (University of Washington), and J. Smith (Coastal 

 Engineering Research Center (CERC)) whose tireless dedication (well, okay, 



118 



Chapter 6 Suspended Sediment Concentration 



