6 Suspended Sediment 

 Concentration 

 Measurements at 

 SUPERTANK 1 



Introduction 



Background 



Early work on suspended sediment transport measurement in the surf zone 

 attempted to characterize the mean suspended sediment profile as a function of 

 cross-shore position, beach slope, and incident wave characteristics (Watts 

 1953, Fairchild 1972, Thornton and Morris 1977, Inman 1978, Kana 1979). 

 The resultant mean profile was either generated from a pump sample (Watts 

 1953, Fairchild 1972, Thornton and Morris 1977) or from averaging a large 

 number of instantaneous samples (Kana 1979, Zampol and Inman 1989). 

 These investigations firmly established that suspended sediment concentrations 

 decrease rapidly with height above the bed and that mean concentration varies 

 between and 20 git near the bed to less than 1 git at 60 cm. Physical 

 processes that apparently govern the variation of the mean suspended sediment 

 profile are: (a) breaker type, with plunging waves suspending more than 

 spilling waves (Kana 1979); (b) position relative to the breakpoint, where 

 concentration reaches a maximum shoreward of the breakpoint (Kana 1979); 

 and (c) cross-shore position, where maximum concentrations are found near 

 the breakpoint and in the inner surf zone close to the swash (Kana 1979). 

 Although these observations provide a general understanding of the spatial 

 distribution of suspended sediment, the first attempts at characterizing the 

 temporal variation of suspended sediment on time periods short relative to the 

 wave period were made by Brenninkmeyer (1975, 1976a,b) and Thornton and 

 Morris (1977). These investigators utilized forward-scattering optical devices 

 to monitor changes in turbidity; Brenninkmeyer used an "almometer," capable 

 of simultaneously monitoring conditions at many elevations above the bed, 



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'Written by Reginald A. Beach, Oregon State University. 



Chapter 6 Suspended Sediment Concentration 



