Sand Transport Rates 



Longshore sand transport 



110. The empirical predictive formula for the longshore sand transport 

 rate used in GENESIS is 



Q - (H 2 C g ) b [a x sin20 bs - a 2 cos* bs -f^ 



(2) 



where 



H = wave height 

 C g = wave group speed given by linear wave theory 



b = subscript denoting wave breaking condition 

 6 bs = angle of breaking waves to the local shoreline 

 The nondimensional parameters a 1 and a 2 are given by 



l6( Ps /p - 1)(1 - p)(1.416) 5/2 

 and (3) 



8( Ps /p - 1)(1 - p)tan£(1.416) 7/2 



where 



K lt K 2 = empirical coefficient, treated as a calibration parameter 



p s = density of sand (taken to be 2.65 10 3 kg/m 3 for quartz sand) 



p - density of water (1.03 10 3 kg/m 3 for seawater) 



p =■ porosity of sand on the bed (taken to be 0.4) 



tan/3 = average bottom slope from the shoreline to the depth of active 

 longshore sand transport 



The factors involving 1.416 are used to convert from significant wave height, 

 the statistical wave height required by GENESIS, to root-mean- square (rms) 

 wave height. 



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