east, southeast, and south), with the wave statistics from the inter- 

 mediate directions (north-northeast, east-northeast, etc.) being incor- 

 porated proportionately into the four primary directions. Figure 33 

 shows these approach angles relative to the shoreline orientation. 



The distribution of wave height waf converted to an equivalent 

 distribution of wave energy (wave height squared) and divided into three 

 ranges. The wave height corresponding to each of the midrange values of 

 wave energy was then determined. The offshore wave height and approach 

 angle corresponding to each of the three nearshore wave heights were 

 calculated for each period and nearshore angle condition. Both the 

 offshore wave direction and refraction coefficients were determined by 

 using Snell's Law, and the shoaling coefficients were calculated by the 

 ratio of nearshore and offshore depths. The offshore wave heights cor- 

 responding to each of the three nearshore wave heights were calculated 

 by dividing the nearshore height by the product of the refraction, 

 shoaling, and friction coefficients. Explanation of the development of 

 the friction coefficient is detailed later in Section (c). The three 

 offshore wave heights used in the analysis were 0.52, 1.40, and 

 2.47 meters. 



The probability of occurrence (expressed as a percentage) of a wave 

 approaching the study area from each of the four directions, with a wave 

 height and period falling within one of the three height ranges and six 

 period ranges (i.e., 72 different cases), was calculated from the data 

 sets for each season; i.e., winter (December, January, and February), 

 spring (March, April, and May), summer (June, July, and August), and 

 fall (September, October, and November). This information is presented 

 in Table 13. 



The percentage of occurrence of many of the wave height-period- 

 direction combinations is less than one. To reduce excessive and 

 unnecessary analysis costs, it was decided that satisfactory results 

 could be achieved by using only enough wave combinations so that, for 

 each season, 95 percent of occurrence by wave energy of all possible 

 combinations of height, period, and direction was modeled. Selection of 

 seasonal wave types was based on the summation of percentage of 

 occurrence by wave energy of those wave conditions with the highest 

 percentage until the 95-percent criterion was satisfied. Summation to 

 95 percent by wave energy resulted in a representation of the wave 

 climate by approximately 98 percent of the observed wave types. Table 14 

 shows the offshore wave climate chosen to represent the average seasonal 

 conditions measured along the study area. The average annual climate is 

 represented by the arithmetic average of the seasonal values for each 

 combination of wave height, period, and direction. 



The final step in the selection of the wave climate data was a 

 calibration check using the wave refraction model. The annual wave 

 climate sets were refracted toward shore and combined according to their 

 percentage of occurrence (see Section V, 3). The directional 

 distribution of the wave energy at Wrightsville Beach was compared to 



63 



