measured wave kinematics on armor layers and the resulting forces, including Mizutani 

 et al. (1992), Torum and Van Gent (1992), Torum (1994), and Comett and Mansard 

 (1994), there have been few observations of incipient movement of armor units 

 discussed in the literature. As such, the relationships between incipient motion, wave 

 kinematics, and forces on armor units are still unknown. 



Melby (1987) and McDougal et al. (1988) discussed a model for predicting 

 the wave forces on dolos concrete armor units and the resulting incipient motion of a 

 lone dolos in one of two orientations. Their model utilized linear wave theory and 

 Morison forcing (Morison et al. 1950) with added mass coefficients for wave slamming 

 from Kaplan and Silbert (1976) and Kaplan (1979). Kobayashi et al. (1990) presented a 

 numerical model for predicting the displacement of armor on a traditional rubble 

 mound. The shallow water wave model interacted with a permeable flow model and 

 hydrodynamic drag, inertia, and lift forces were computed using a Morison formulation. 

 The model was limited to forces parallel to the structure because only depth-averaged 

 velocities were predicted by this one-dimensional model. Torum and Van Gent (1992) 

 discussed a similar wave model and compared it to velocity measurements above a berm 

 breakwater. Torum (1994) discussed the measurements further. Although two- 

 dimensional velocities were measured, vertical flow in the breaking wave was not 

 modeled numerically. In addition, Torum noted that the inertial force was not well 

 defined by the traditional inertia term of the Morison equation. Comett and Mansard 

 (1994) described an experiment where forces were measured on a panel of stones. This 



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