probably not be accurately known, so that use of a schematic 

 profile is convenient. On the other hand, beach erosion is 

 expected to be sensitive to the initial profile configuration, 

 including the presence of a bar. 



e_. The onshore boundary condition is based on simple geometrical 

 considerations. It does not accurately reproduce poststorm 

 profile shapes. A more sophisticated onshore boundary 

 condition is desirable. 



f_. A highly schematic but very reasonable expression is used to 

 model the cross-shore sediment transport rate. Although not 

 based on fundamental physical principles, it appears to be 

 well suited for engineering applications. The sediment 

 continuity equation is used to calculate profile change and 

 dune erosion. It is limited to cross-shore transport, and the 

 only major features modeled are dune and berm erosion and 

 change of an assumed equilibrium-shaped profile. 



g_. The model time-steps through the storm hydrograph toward an 

 equilibrium form. This time-dependent capability is an 

 important property of the model since it allows both long and 

 short duration storms to be modeled. 



h. The model has been demonstrated to give reasonable results in 

 a limited number of comparisons to measured dune erosion 

 volumes. A more detailed discussion of this point is given in 

 Part V. 



82. The Kriebel model is judged to provide a reasonable means to 

 estimate dune erosion which is compatible with the expected quality of the 

 input data. The model requires as input the beach grain size; an initial 

 profile if available or, instead, an assumed schematic profile; the surge 

 hydrograph; and the deepwater wave height. The model does not allow for bar 

 formation; therefore, the recovery process is not well described. Similarly, 

 sediment transport seaward of the breaker line is not taken into account. 



83. Although not discussed in detail here, the Kriebel model could be 

 modified to allow for inundation. In principle, the model could also be 

 extended to describe erosion of seawall-backed dunes. Such a model is 

 currently undergoing testing at CERC and is found to perform favorably. 



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