A tenfold increase in infragravity variance is predicted between the 8-m depth 

 and the shoreline for edge wave modes through 8 in the 0.02- to 0.04-Hz band. 

 Numerical calculations for this prediction were assuming equal shoreline 

 elevation amplitude for modes through 8 (i.e., a "white" spectrum assumption). 

 The average measured amplification of 35 suggests the assumption of equal 

 shoreline elevation for the trapped modes may not be reasonable. The 

 underprediction of the model indicates that low-mode (e.g., 0-3) edge waves, 

 trapped shoreward of the 8-m array, may have had larger shoreline amplitudes 

 than the higher modes (4-8). Thus, it is conceivable that preferential trapping of 

 the lower modes may have occurred, such that modes matching resonant 

 conditions of the beach and bar-trough topography were selectively amplified. 



Table 3 



Infragravity (0.02-0.04 Hz) Wave Climate at the Shoreline and 800 m Offshore 



Day 



Start Time 

 (EST) 



800 m 

 Variance 

 (cm 2 ) 



Swash 

 Variance 

 (cm 2 ) 



Swash/ 

 800 m 

 Variance 



800 m 



% 



Trapped 



800 m 



% 



Leaky 



800 m 



% 



Forced 



04 Oct 90 

 04 Oct 90 

 04 Oct 90 



820 

 1132 

 1608 



.63 

 .48 

 .57 



24.00 

 12.20 

 31.70 



37.84 

 25.34 

 55.47 



66.89 

 66.50 

 73.94 



29.16 

 25.25 

 21.15 



3.95 

 8.25 

 4.91 



05 Oct 90 

 05 Oct 90 



824 

 1300 



.41 

 .32 



57.40 

 12.30 



141.44 

 38.45 



67.77 

 61.88 



27.66 

 27.75 



4.57 

 10.37 



06 Oct 90 

 06 Oct 90 

 06 Oct 90 



713 

 917 

 1235 



.56 

 .65 

 .49 



52.30 

 66.40 

 34.60 



93.88 

 102.28 

 70.87 



74.09 

 72.74 

 58.40 



19.30 

 22.37 

 34.54 



6.61 

 4.89 

 7.06 



07 Oct 90 

 07 Oct 90 

 07 Oct 90 



728 

 930 

 1357 



2.07 

 1.92 

 1.02 



83.00 

 172.00 

 72.00 



40.11 

 89.56 

 70.36 



81.00 

 80.66 

 60.40 



16.54 

 15.58 

 33.46 



2.46 

 3.76 

 6.15 



08 Oct 90 

 08 Oct 90 

 08 Oct 90 

 08 Oct 90 



813 

 1023 

 1330 

 1532 



4.41 

 4.39 

 3.51 

 2.91 



101.00 

 189.00 

 115.00 

 165.00 



22.90 

 43.01 

 32.75 

 56.64 



85.75 

 78.47 

 74.33 

 71.18 



12.06 

 19.31 

 20.54 

 24.03 



2.19 

 2.22 

 5.13 

 4.79 



09 Oct 90 

 09 Oct 90 



900 

 1330 



7.13 

 5.62 



201.00 

 233.00 



28.19 

 41.48 



82.43 

 78.52 



13.87 

 16.70 



3.71 

 4.78 



10 Oct 90 

 10 Oct 90 

 10 Oct 90 

 10 Oct 90 



537 

 723 

 954 

 1213 



5.71 

 7.19 

 6.64 



7.37 



135.00 

 113.00 

 344.00 

 206.00 



23.64 

 15.72 

 51.80 

 27.95 



79.19 

 76.47 

 80.94 

 84.36 



17.04 

 19.19 

 15.64 

 11.94 



3.77 

 4.33 

 3.42 

 3.70 



1 1 Oct 90 

 1 1 Oct 90 

 1 1 Oct 90 

 1 1 Oct 90 



630 

 847 

 1055 

 1305 



16.33 

 15.39 

 12.52 



12.43 



182.00 

 294.00 

 341.00 

 276.00 



11.14 

 19.10 

 27.23 

 22.20 



70.00 

 73.72 

 72.97 

 80.61 



19.37 

 17.50 

 17.87 

 13.64 



10.63 

 8.78 

 9.16 



5.75 



12 Oct 90 

 12 Oct 90 

 12 Oct 90 



719 

 1226 



1538 



7.09 

 7.91 

 15.68 



298.00 

 309.00 

 767.00 



42.04 

 39.06 

 48.93 



71.44 

 73.46 

 69.09 



20.76 

 20.83 

 25.91 



7.80 

 5.71 

 5.00 



Note: Percent trapped, leaky and forced wave estimates are from k-f spectral analysis at the 800 m array. 



(Continued) 



Chapter 4 Field Observations 



39 



