The example in Table 3 and an inspection of Appendixes A, B, and C sug- 

 gest the following general rules when predicting nearshore wave height from 

 deepwater conditions: 



(a) Water depth becomes an increasingly important factor for 

 predictions of wave height in shallower water where (d/H^ < 1) . 



(b) Deepwater wave height is not important to predictions of 

 nearshore wave height where d/H^ < 1, but it is more important in 

 deeper water where d/H^ > 1. 



(c) Substantial errors in wave period produce underestimates 

 or overestimates of wave height where d/H^ > 1, but are less im- 

 portant when d/H^ < 1 . 



(d) Refraction and directional spreading of wave energy are not 

 important variables in shallow areas where d/H^ < 1 because refrac- 

 tion and breaking effects tend to cancel one another; i.e., at a 

 given depth, less refraction is associated with more wave breaking 

 and more refraction means less breaking. Large errors in deepwater 

 wave angle will have a pronounced effect where d/H^ > 1 or for 

 large wave angles. 



(e) In shallow water where d/H^ < 1, much of the information 

 about deepwater conditions is lost due to wave breaking and refrac- 

 tion effects. 



V. ANALYSIS OF NEARSHORE WAVE HEIGHT CHANGES 

 AT THE CERC FIELD RESEARCH FACILITY 



The usefulness of the nearshore wave prediction methods presented in Sec- 

 tions II and III is illustrated by comparing observed and predicted nearshore 

 wave heights measured at points along the 580-meter-long pier at the CERC 

 Field Research Facility (FRF) . Note that this is by no means a definitive 

 test of the prediction methods for several reasons. First (as discussed in 

 Section (IV) , some input parameters are more important than others and in the 

 case of the FRF data the accuracy of the input information is unknown. Since 

 water depth was shown to be especially important in Section IV, profiles were 

 taken on either side of the pier and tides were estimated hourly. The pres- 

 ence of bars or scour holes under the pier near the gages is not known. Sec- 

 ond, the effects of reflection, wave direction, runup, and spray from the 

 pier piles on the observed wave records at each of the gages are unknown. 

 However, a comparison of observed and predicted wave heights measured at the 

 pier is considered useful. 



Since extreme conditions are generally of the most interest to designers, 

 waves produced by two storms are examined. The first storm (18 to 23 December 

 1977) had a relatively long duration, produced a storm surge of approximately 

 0.3 meter, and had maximum significant wave, heights of 3.5 meters at the end 

 of pier. A second storm of shorter duration and less wave activity occurred on 

 13 September 1978 with maximum significant wave heights of approximately 2 

 meters off the end of the pier. 



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