Equation 78 has the same functional form as Equation 4-50b of the Shore 

 Protection Manual (SPM) (1984) if the group velocity at breaking is 

 approximated by solitary wave theory and the units are converted as follows; 



*1 = 



0.00642 IT 2 



1/2 



pgH -Jgh (1 + y) sin 9 cos 9 



(79) 



The sediment concentration C can be obtained by equating Equations 78 and 

 79. That is, 



C = 



0.0008 pg 



\ / B 

 tan g \/A + 1 



3 P + 2 



(80) 



In computing C , the following relation for (tan 3/cj is used: 



tan 6 1.38 



(1 - 2.5 Pg) 



1 1 



2 + nr 



2 1 



/P 2 -l 



, P 1" P 



(81) 



(1 + Y) 



1/2 



Since for a particular wave condition H. and x^ are known from the wave 

 model, C is known for the surf zone. 

 Transport beyond the surf zone 



60. Beyond the surf zone, waves are not breaking. Currents (tidal, 

 littoral, rip) still transport sediment, but the sediment load is much smaller 

 than the load in the surf zone. Waves still assist in providing power to sup- 

 port sand in a dispersed state. However, there is little turbulent energy 

 dissipation, and frictional energy dissipated on the bottom represents most of 

 the energy dissipation. Bed load is the primary mode of sediment transport 

 beyond the surf zone according to Thornton (1972). 



61. Since beyond the surf zone it is the tractive forces of currents 

 (including wave orbital velocity currents) that produce sediment movement, a 

 sediment transport by currents approach is taken. Again, since the complete 

 physics of the problem is not completely understood, a semiempirical approach 

 must be taken. In this study, the approach of Ackers and White (1973) is 

 followed after appropriate modification for the influence of waves. 



62. Ackers and White (1973) studied sediment transport due to currents. 

 They used the results of 925 individual sediment transport experiments to 



49 



