resulting from the stairstep portrayal of the coast boundary are 

 shown through the comparison of Figures 78 and 79. The curvilinear 

 model shows the maximum coastal water level at the time of landfall 

 of approximately 3 meters while the Cartesian system predicts 4 

 meters. Furthermore, the peak surge of 4.5 meters in the Cartesian 

 system occurred at the corner point (22, 19) over 2 hours after 

 storm landfall. 



The water velocity, V , from the curvilinear system is presented 

 in Figure 80. The figure also shows the development of a cyclonic 

 current in the region from Cape Romain to Cape Fear resulting from 

 the curved coastline and the extensive Frying Pan Shoals off Cape 

 Fear. A similar current pattern is not observed in the rectilinear 

 system. 



The computed high water envelopes from both grids are shown in 

 Figure 81. The stairstep rectilinear coastline is projected upon the 

 curvilinear coastline providing a common basis for the comparison. 

 Both systems predict a maximum surge comparable to that of the near- 

 est observed high water mark. The effect of the rectilinear coast- 

 line on the surge envelope is seen in the figure by the relative 

 water level maximums at the interior corner grid points. The pri- 

 mary contrast of the coastal envelope of computed surges in the two 

 different grid systems is the greater variability of that from the 

 rectangular grid. This leads to spurious results as can be seen 

 particular for Savannah River. 



127 



