Table 2 (Concluded) 











Incidence 







Mean 





Start 





Peak 



to Beach 





Shoreline 



Longshore 





Time 



Hmo 



Freq. 



Normal 



Irribarren 



Beach 



Current 



Day 



(EST) 



(m) 



(Hz) 



(deg) 



Number 



Slope 



(m/s) 



17 Oct 90 



710 



0.92 



0.113 



-22 



1.41 



0.113 



-0.20 



17 Oct 90 



919 



0.88 



0.103 



-18 



1.23 



0.099 



-0.35 



17 Oct 90 



1129 



0.88 



0.103 



-18 



0.87 



0.074 



-0.35 



17 Oct 90 



1338 



0.90 



0.103 



-20 



1.12 



0.097 



-0.44 



17 Oct 90 



1550 



0.87 



0.103 



-22 



1.30 



0.101 



-0.35 



18 Oct 90 



700 



0.97 



0.191 



-32 



1.83 



0.094 



-0.33 



18 Oct 90 



1116 



0.99 



0.181 



^8 



1.96 



0.102 



-0.63 



18 Oct 90 



1311 



1.04 



0.171 



-18 



1.69 



0.097 



-0.65 



19 Oct 90 



710 



1.15 



0.152 



34 



1.76 



0.098 



0.29 



19 Oct 90 



919 



1.19 



0.132 



6 



0.75 



0.085 



0.30 



19 Oct 90 



1213 



1.10 



0.142 



10 



0.71 



0.085 



0.10 



190ct 90 



1423 



1.10 



0.142 



10 



0.76 



0.090 



0.17 



10 s 









irP 









^» 



S 101 









S 1<j2 





.-*'! *' ' 







JO 



1 



52 10' 



o 

 ■o 









c 

 • .0 



2 , 



0. io' 



3 

 C 

 3 



K 











6 10° 

 m 





'-" 1* 





<2 10" 











10"' 

 1 



O 1 



10* 



10» 



10' 



10* 



10 3 







Swell Variance 







Swell Variance 







Figure 1 8. Correlation between incident swell variance and infragravity variance at 8-m 

 depth (left) and in the runup (right). Variance units are in cm 2 



Analysis of k-f spectra in infragravity energy measured at 8-m water depth 

 during this time fount the infragravity band (0.02 - 0.04 Hz) typically dominated 

 by trapped edge waves, comprising approximately 80 percent of the total 

 infragravity energy, with the remaining energy consisting primarily of leaky 

 waves. Bound waves generally contributed about 4 percent of the infragravity 

 variance, but as much as 16 percent has been observed. With a high content of 

 trapped edge waves, which have a maximum amplitude at the shoreline and 

 exponentially decay offshore, an amplification of infragravity variance is 

 expected between 8-m depth and in the runup. The average amplification was 35 

 and ranged from about 10 to over 100 (Table 3). 



38 



Chapter 4 Field Observations 



