sediment transport. Bowen's model has not been developed further than the 

 initial formulation. Bailard (1985) states that the performance of his model 

 was "disappointing" in a comparison of predicted and measured profile change. 

 Bailard's work is described in the next subsection. Dally and Dean (1982) 

 developed a beach profile numerical model by assuming mean wave-induced flows 

 are responsible for the sediment transport. Only suspended load was 

 considered. Leont'ev (1985) uses an energetics-based approach and assumes 

 bed-load transport is directed solely onshore; whereas suspended load is 

 directed solely offshore. Mean flows are calculated. Yang's (1981) model 

 employs both mean and fluctuating currents, and the suspended load (no bed 

 load is included) is assumed to be transported only offshore. Moore (1982) 

 uses an equilibrium profile-based transport model plus a surf zone wave 

 model . 



57. It is remarkable that despite quite different assumptions, all of 

 the above mentioned models were demonstrated by the authors to represent 

 beach profile change to some extent. Notably, in the development of the 

 cited models, little discussion was given to the onshore and offshore 

 boundary conditions and to the approach to equilibrium. Also, only very 

 limited verification data were employed. In particular, no comparison was 

 made to data on the sediment transport rate but only to profile change. In 

 order to further explore these models, it is useful to examine one of them, 

 Bailard's sediment transport model, in detail. 



Sediment transport model of Bailard 



58. Bailard (1981) derived equations for both longshore and cross- 

 shore sediment transport on an assumed idealized beach of constant slope. 



The model is based on the energetics approach of Bagnold (1963, 1966). Bowen 

 (1980) presented a similar model. Since the model of Bailard has undergone 

 refinement and testing (Bailard 1982, 1983, and 1985), Bailard's work was 

 selected for closer examination, and discussion will be limited to the cross- 

 shore component. It should be mentioned that Bailard's work mainly concerns 

 the theoretical derivation and interpretation of a general sediment transport 

 rate equation, although the transport rate formulas were applied in a 

 "2-line" numerical model (Bailard 1985) in which the profile is characterized 

 by two contours. 



59. The transport model of Bailard (1981) generalized Bagnold's 

 steady-state energetics-based stream model to account for time-varying flow 



30 



