APPENDIX G 

 Method Usea in Obtaining Most-Frequent 

 Combinations of Deep-¥ater Height, Period, 

 And Direction of Waves Capable of Striking Virginia Beach 

 A rough estimate of the 15 most-frequent combinations of wave height, 

 period, and direction of deep-water waves capable of striking Virginia Beach 

 is gained by an analysis of five representative years of wave observations 

 at the Chesapeake Lightship (fig. l) . Results of the analysis appear in 

 table Gl and indicate that only six combinations of period and direction are 

 involved in the 15 combinations. These six combinations are rough approxima- 

 tions for input data, not only because of the crude methods involved in wave 

 observation and recording, but also because it is assumed that one can pre- 

 serve wave-direction angles for the waves observed at Chesapeake Lightship 

 when searching for deep-water origin points that will yield rays capable of 

 striking the target area. This is in error for some of the U-second and 

 all of the 6-second waves because they have already undergone refraction by 

 the time they have reached Chesapeake Lightship; it is, therefore, invalid 

 to select deep-water starting points for most waves by assuming that deep- 

 water wave directions in water deptHs greater than 6h feet (Lightship water 

 depth) are parallel to those observed at the Lightship. 



The h and 6-second waves that dominate the Lightship observations 

 of table Gl are a product of the convention used here in interpreting the 

 Ship's International Code. The convention is based upon an analysis of 

 wave gage records that indicate a dominant U-second period (table G2) at 

 a wave recording point off Cape Henry (fig. Gl) . (The Cape Henry wave 

 gage was operated by the U. S. Wavy between 1951 and. 1956. It consisted 



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