of beach erosion. In this manner, an efficient yet economically feasible 
beachfill program can be evaluated and realized. 
Beach Erosion Numerical Model 
Background 
130. A numerical modeling scheme for beach and dune erosion developed 
at the University of Delaware and the University of Florida was selected for 
modification and enhancement to include the capability of simulating vertical 
seawalls. The background and application of this model have been reported by 
Kriebel (1982; 1984a,b), and Kriebel and Dean (1985a,b). A quantitative com- 
parison of this model, referred to as the "Kriebel" model, was made to various 
existing dune and berm erosion models by Birkemeier et al. (1987). 
131. The comparison concluded that the Kriebel model was conceptually 
superior to other existing models, although, with proper calibration and 
"tuning," each was capable of predicting approximately similar results with 
respect to erosion volumes. This is not unexpected since all presently avail- 
able coastal zone erosion models are empirical in their formulation. It was 
found, however, that the Kriebel model was less susceptible to user manipula- 
tion and yielded realistic results without having to alter coefficients. This 
is due, in part, to the following desirable features of the model which are 
not shared by the other investigated models: 
a. The model does not require detailed knowledge of the berm or 
dune geometry or the offshore bathymetry. 
In 
The model relates the computed offshore sediment transport 
rate (which is used to compute dune or berm erosion) to 
several wave and storm parameters. Although the model is 
still empirical, this feature is viewed as advantageous. 
Models which neglect this coupling are rendered site specific 
in that they must be calibrated for each new application. 
10 
The model is easy and economical to apply. This feature 
permits the simulation of multiple storm events required for 
the computation of the final berm (or dune) recession and 
erosion volume versus recurrence interval plots. 
Basic Theory 
132. The objective of the beach erosion model is to determine both the 
volume of material which will be eroded during a specific storm event and the 
corresponding amount of berm recession which can be expected to occur. These 
quantities are a function of the existing (pre-storm) berm and subaqueous 
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