Theoretical works on statistical distribution of hydrodynamic 

 forces on small structures in waves and currents are Tung and Huang 

 (1973a, 1973b, 1974, 1976), Tung (197i), Moe and Crandall (1978), Hedges, 

 Burrows, and Mason (1979), Vinje (1980), and Burrows, Hedges, and Mason 

 (1981). These all start with unidirectional waves and currents, make 

 certain statistical assumptions, and assume that a wave spectrum 

 propagates from still water onto the current. Burrows, Hedges, and 

 Mason (1981) point out that some earlier spectral studies did not use 

 the Itoppler-shifted frequency. 



Sekita (1975) measured forces on a model of a deep-sea platform, 

 both with waves and in waves and currents. The current was obtained by 

 moving the model with uniform velocity. Sekita found that there is 

 appreciable sheltering of structural members by other upstream members 

 in both waves and currents, leading to relatively smaller drag coeffi- 

 cients for the whole structure. There is no discussion of wave-current 

 interaction in this paper. 



Kruijt and van Oorschot (1979) report experiments in a large wave 

 basin with both waves and currents incident on a model of concrete 

 supports for a storm surge barrier. The wave direction, relative to 

 both the current and the structure, was varied. The authors conclude 

 from their force measurements that interactions between waves and 

 currents must be taken into account. Longitudinal force components are 

 reasonably well predicted if the Doppler effect on the waves' frequency 

 is taken into account. However, Doppler effects do not explain measured 

 transverse forces. Forces resulting from the wave-current interaction 

 are greater, and moments about a vertical axis have larger fluctuations 

 than those due to current alone. The increased fluctuations are 

 attributed to the effect of currents in exaggerating the phase 

 difference between wave crests on either side of the structure. 



Dalrymple (1975) gives a report of the analysis of measurements 

 taken on an instrumented platform in 30 meters of water during Hurricane 

 Carla in 1963. He discusses the interpretation in terms of waves and 

 currents, and concludes that drag coefficients which had been obtained 

 from the same data without considering the presence of a current are too 

 large. The data cannot be interpreted as due to one wave train and a 

 uniform current. More than one wave train was present, with different 

 directions of propagation, and the current could have varied with depth. 

 Force direction did vary with depth. 



3. Sediment Transport. 



Sediment transport due to the action of a current alone is 

 reasonably well documented. Although detailed mechanisms are not fully 

 understood, reasonable estimates can be made. Transport by waves is 

 more difficult to estimate. 



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