reach D , the height of waves which propagate from the open ocean was set to 

 zero. There were two justifications for this adjustment. First, due to the 

 orientation of the wall, there is no opportunity for these waves to attack 

 the wall from any but very oblique angles. Second, reach D would be partially 

 sheltered from waves from these oblique angles by the tip of Roughans Point 

 and by Simpson's Pier. At reaches A and C, waves from the open ocean were re- 

 uced by 50 percent. As at reach D, these waves would approach from an oblique 

 angle; however, refraction would turn these waves more normal to reaches A and 

 C than at reach D. Since the physical modeling assumed a wave direction nor- 

 mal to the structure, using the full wave height for these waves would result 

 in the overprediction of overtopping rates. The locally generated waves were 

 reduced by 15 percent for all three north wall sections. This can "also be 

 justified by the fact that these waves do not always approach normal to the 

 wall sections. 



81. The above adjustments were made to the overtopping calculation and 

 flood routing computer codes to match calculated values of interior stage to 

 those observed during the February 1978 storm. The February 1972 storm was 

 then simulated to verify the revised procedure. The results of these two 

 simulations are compared to estimates of actual flooding in Table 9. 



Table 9 

 Comparison of Calculated to Observed Flood Stage 







Calculated 



Observed 



Storm 



ft, NGVD 



ft, NGVD 



1978 



11.9 



11.8-12.0 



1972 



9.6 



8.8-9.0 



82. The results of this calibration and verification were judged to be 

 acceptable. The 0.6-ft difference between observed and calculated water 

 levels for the 1972 storm seems reasonable when considering that the calcula- 

 tions were based upon a stage-volume relationship determined from 2-ft contour 

 intervals. 



Simulation of the Event Ensemble by the Flood Routing Model 



83. Following calibration and verification of the flood routing model, 



63 



