APPENDIX E. Water Levels and Waves 



This appendix contains time series of the water levels and waves of the three storms selected 

 to simulate storm-induced beach erosion at the properties of the two test plaintiffs and the 

 extreme water levels measured at the Fernandina and Mayport stations. The calculations are 

 described in Section 3.4 of the main text. 



E.1. Storms 



The wave data were taken from the Wave Information Study (WIS) Atlantic Hindcast 

 (Hubertz et al. 1993), Station 18, which is located in 22-m (72.2-ft) depth seaward of the Cape 

 Canaveral Shoal. The significant wave height and corresponding peak period at this depth are 

 shown in the plots. Hourly water-level data as provided by National Ocean Service (NOS) and 

 hindcast wave data at 3-hr intervals comprised the oceanic forcing for the dune erosion modeling. 

 Prior to modeling of dune erosion, the wave data time series at the 22-m depth were transformed 

 to the 10-m (33-ft) depth, corresponding to the nominal depth at the seaward ends of the 

 available profile survey data, to account for directional wave spreading and energy losses. 



Plots of water level given in this report are referenced to mean tide level (MTL), whereas, in 

 principle, water-level data input to the SBEACH model should be referenced to the National 

 Geodetic Vertical Datum (NGVD). This suggests that some adjustment of the water-level data 

 would be required to convert those elevations to the NGVD datum. Water-level data sets 

 obtained from NOS are referenced to the gauge-specific MTL elevation. The relationship 

 between MTL datum and NGVD datum is not fixed, but varies according to the location of the 

 site in question. For the historic tide gauge at Port Canaveral, NOS has estimated that MTL is 

 0.19 ft higher than NGVD, as illustrated in Figure 2-7. In comparison, estimated differences 

 between MTL and NGVD at Fernandina, Mayport, and St. Augustine are 0.28, 0.31, and 0.17 ft, 

 respectively; therefore, the differences in conversion values for all four sites was relatively small 

 (within about 0.1 ft). It should also be noted that there are some inherent uncertainties between 

 reference datums, such as the fact that they do not include contributions from relative sea-level 

 rise between the tidal datum epoch (1960-1978) used in their calculation and the present time. 

 For these reasons, it was assumed that the MTL elevations at the tide gauges listed in Table 3-4 

 are equivalent to the NGVD elevation at Brevard County. Therefore, no MTL-to-NGVD 

 conversion was required for the water-level data input to SBEACH. 



Appendix E Water Levels and Waves ■ £.-j 



