Recommendations 



Sand concentration data from the carriage should be subjected to both sta- 

 tistical and spectral analyses. Up/do wncrossing analysis would be meaningful 

 for records that displayed an oscillatory behavior (i.e., outside the turbulent 

 zone), whereas threshold-crossing/duration techniques should be used to char- 

 acterize suspension events inside the surf zone. Attempts to correlate total 

 suspended load with breaking wave parameters such as breaker height or 

 Irribarren Number should also be attempted. 



In future laboratory investigations, it is recommended that some means of 

 measuring the local near-bed turbulence be incorporated. This was the one 

 important parameter that was not measured during SUPERTANK. Use of a 

 laser-Doppler or hot-film velocimeter should be explored. It is also 

 recommended that the mobile array be used to traverse the entire surf zone, 

 collecting data at high cross-shore resolution to better distinguish zones of 

 high suspended load. Including a sonic concentration profiler on the carriage 

 would also be extremely useful for side-by-side comparison and augmentation 

 of the OBS data, especially in regions of low aeration. 



Acknowledgements 



The authors greatly appreciate the advice of, and collaboration with, 

 Dr. Reginald A. Beach, Oregon State University, and Dr. David L. Kriebel, 

 U.S. Naval Academy. The assistance of Messrs. Terry Dibble and Bill 

 Hollings, and the efforts of the entire staff of the O.H. Hinsdale Wave 

 Research Laboratory are gratefully acknowledged. This study was financially 

 supported by the U.S. Army Engineer Waterways Experiment Station, Coastal 

 Engineering Research Center (Contract DACW399-91-K-0011). 



References 



Beach, R. A. (1989). "Suspended sediment transport in the surf zone," Ph.D. 

 diss., Univ. of Washington, Seattle, WA. 



Beach, R. A., and Sternberg, R. W. (1988). "Suspended sediment transport in 

 the surf zone: Response to cross-shore infragravity motion," Marine Geol- 

 ogy 80, 61-79. 



Coakley, J. P., Savile, H. A., Pedrosa, M., and Larocque, M. (1978). "Sled 

 system for profiling suspended littoral drift." Proc. 16th Coastal Engrg. 

 Conf. ASCE, New York, NY, 1764-75. 



Downing, J. P., Sternberg, R.W., and Lister, C.R.B. (1981). "New instru- 

 mentation for the investigation of sediment suspension processes in the 

 shallow marine environment," Marine Geology 42, 19-34. 



Chapter 7 Sediment Suspension Measurements from a Platform 



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