allows the post-storm wave runup to build a berm. In the model, berm forma- 

 tion and growth is largely controlled by the elevation reached by wave runup 

 (Larson 1988, Larson and Kraus 1989), which is reduced on steeper slopes. 

 Eroded Volume and Grain Size 



Figs. 12 and 13 plot eroded volume at the end of the storm (prior to 

 recovery wave action) as a function of the grain size of the fill. As previ- 

 ously mentioned, the native beach grain size was set at 0.2 mm, and the area 

 in which the fill was placed was assigned the grain size of the fill. This 

 procedure does not allow tracking of movement of the different grain sizes. 

 However, since surf zone sediments are usually sorted with coarser material 

 located higher on the active profile, this simple procedure is considered to 

 provide a reasonable first approximation of the response of a natural beach of 

 varying grain size. 



Figs. 12 and 13 show a relatively steep decrease in eroded volume as grain 

 size increases through the range of 0.2 mm to 0.4 mm, with a gentle decrease 

 thereafter. This behavior follows from the property of the empirically 

 determined functional dependence of the wave energy dissipation needed to 

 generate an equilibrium profile of given grain size. This property is shown 

 by computed dissipation rates which rise steeply in the range of 0.1 to 0.4 

 mm, and then increases at a lower rate with increasing grain size (Moore 

 1982). Since the rate of decrease in erosion is small beyond 0.4 mm, and the 

 cost of beach fill typically increases substantially for larger size material, 

 calculations such as those illustrated in Figs. 12 and 13 allow an evaluation 

 to be made of initial fill and subsequent fill maintenance costs. 



CONCLUSIONS 



Main findings and recommendations from this study are: 



1. Storm- induced beach and dune erosion cannot be uniquely specified 

 through a single storm-related parameter such as the maximum stage. 

 This result demonstrates the limited usefulness of the design storm 

 approach. 



2. The 1-m contour is a useful datum to which to refer storm-eroded 

 volume and beach recession, in addition to the shoreline or 0-depth 

 (MSL) datum. 



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