4> s = angle of repose for a given sediment grain, degrees 



7 = specific weight of fluid, lb f /ft 3 



7 S = specific weight of sediment, lb f /ft 3 



V s = volume of a sediment grain, ft 3 



A s = projected area of a sediment grain, ft 2 



A = orbital diameter of wave motion, ft 



w = terminal fall velocity of sediment, ft/sec 



u* = shear velocity = (r/p) 1/2 , ft/sec 



Ujj,.^ = near bottom maximum horizontal orbital velocity, ft/sec 



p s = sediment density, lb m /ft 3 



p = fluid density, lb m /ft 3 



g = acceleration due to gravity, ft/sec 2 



The relationships of Komar and Miller are shown graphically in Figure 3 below. 

 Their findings, based solely on laboratory data, essentially state that the 

 threshold of sediment movement for median grain diameter d and density p s can 

 be specified by a wave period and a near-bed orbital velocity (u^^) . Use of 

 the Komar and Miller relationships should be tempered by the lack of prototype 

 data used to verify them. 



Particle diameter, in 



Figure 3. Komar and Miller (1974) plots of near-bottom orbital 



velocity for threshold of sediment movement under oscillatory 



waves (extracted from Hales (1980)) 



13 



