154 



be stowed in the DUKW cargo compartment without difficulty. 



The disadvantages of faking cable in the cargo compartment are that (1) 

 there is always a possibility of the cable becoming tangled and a danger to any- 

 one attempting to free such tangles, (2) there is no simple way to hold tension 

 on the cable being laid and the cable tends to uncoil too rapidly and (3) consider- 

 able work is involved in unspooling and recoiling the heavy armored cable. 



ANALYSIS OF WAVE RECORDS 



Analysis of Wave Records for Wave Height - If individuals are asked to observe 

 ocean waves and to estimate their height, they will usually report that the waves 

 have an "average height" of, for example, 4 feet and that there are occasionally 

 "maximum" waves 6 feet in height. The estimate for average wave height of 

 several observers is reasonably consistent, providing a frame of reference is 

 supplied against which the waves can be compared. The actual meaning of 

 "average wave height" is of primary importance; it represents what individuals 

 see when observing the random fluctuations of the water surface. 



Experiments were conducted by the University of California during World 

 War II to determine the meaning of "average height" as reported by untrained 

 personnel. Waves were observed by several persons for a given time interval 

 and each individual estimated the average wave height for that period. During 

 this time period a surface record was made of the height of the individual waves. 

 A comparison of the data indicated that the estimated "average height" was ap- 

 proximately the average height of the highest l/3 of the waves, rather than the 

 average height of all waves. 



The average height of the highest 1/3 of the waves (HW3) is used to de- 

 scribe the height of the waves. This height is know as the "significant wave 

 height". The average height of the highest l/lO of the waves (Hi/iq) has been 

 used to represent the height of "occasional high waves" as reported by observ- 

 ers. The height of the highest wave (Hmax) during a given interval of time has 

 been reported by some experimenters, while the average height of all waves 

 (Have) ^^^ been reported by others. 



The ratios between various combinations of Have* H1/3, Hj/jO' ^"^ 

 Hmax have been determined by several investigators. The agreement of daily 

 values to the average values of these ratios and the agreement among values de- 

 termined at widely separated stations indicated that a definite statistical group- 

 ing of waves is generated by wind. 



Evidence to further substantiate this theory is found in the results of a 

 statistical analysis conducted by R.R. Putz (Putz, 1950) at the University of 

 California, Berkeley. Analysis was made of 25 wave records selected from 

 various localities and made at various times of the year to obtain good sampling. 

 Putz found that the statistical frequency distribution of observed wave height in 

 a 20-minute interval is approximately constant in form and, for a first approxi- 

 mation, requires for its complete description only the determination of a typical 

 height, such as the "characteristic wave height". The wave height distribu- 

 tions of all 25 pressure records matched, with reasonable accuracy, a Pearson 

 Type III frequency function with a 0,8 positive skewness and exhibited proportion- 

 ality between the mean and the standard deviations. 



Utilizing this mathematical model, Putz computed values for ratios re- 

 ported. The value of maximum wave height determined from the model was 

 taken as the probable maximum wave in two 20-minute intervals as used by 

 Wiegel in determining his daily maximum wave height. Excellent agreement 



