PART VI: A SYSTEMATIC APPROACH TO V-ZONE DETERMINATION 



108. This section describes a methodology for inclusion of the erosion 

 process in V-zone determination which combines use of the Kriebel and 

 Vellinga models with field measurements, interpretation of historic data, and 

 engineering judgments. If correctly implemented, the described procedure 

 should result in rational and consistent V-zone widths. Areas for which the 

 procedure is most applicable are also identified. 



109. It is worthwhile to note that the recommendations to be made 

 here, though independently determined, are similar to procedures currently 

 implemented by the State of Florida in establishing a Coastal Construction 

 Control Line which is based on the storm surge, waves, and erosion caused by 

 a 100-year storm (Chiu and Dean 1984). The use of a highly simplified ver- 

 sion of the Kriebel model is augmented by an extensive program of field data 

 collection which includes beach and nearshore surveys around the state. Data 

 collected as part of this program are used to further verify and improve 

 erosion predictions. A number of major storms have already been documented 

 and are reported by Chiu (1977) and Balsillie (1985c, 1985d). 



Use of the Model 



110. We recommend a straightforward application of the Kriebel model, 

 as specified in the appropriate references. Refinements discussed by Kriebel 

 (1986), though not tested here, should be included. The Vellinga model will 

 probably not be as widely applicable in its present form as the Kriebel model 

 but may be useful in some areas. Use of the MSBWT model is not yet recom- 

 mended because of its lack of independent verification. The easily computed 

 erosion estimates given by Equation 13 may, however, be useful as an 

 independent check on above-MSL erosion estimates. Further evaluation of the 

 MSBWT model is suggested particularly with respect to its simulation of such 

 features as bar formation and overwash. 



111. Actual beach survey data are used to define the slopes and berm 

 features. The equilibrium slope equation of the offshore, based preferably 

 on actual surveys or grain size (see Balsillie 1982), is determined. Then 

 the Kriebel model is run using the 100-year surge level (including the tide) 

 and duration. FEMA currently computes both the surge level and hydrograph 



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