Table 3 (Concluded) 



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 



13 Oct 90 

 13 Oct 90 

 13 Oct 90 

 13 Oct 90 

 13 Oct 90 



645 

 901 

 1116 

 1339 

 1554 



43.14 

 32.53 

 28.04 

 21.85 

 20.05 



583.00 

 526.00 

 539.00 

 400.00 

 402.00 



13.51 

 16.17 

 19.22 

 18.31 

 20.05 



61.36 

 58.03 

 45.16 

 67.32 

 70.76 



29.89 

 27.97 

 38.35 

 22.99 

 23.64 



8.75 

 14.00 

 16.49 

 9.69 

 5.60 



14 Oct 90 

 14 Oct 90 

 14 Oct 90 

 14 Oct 90 



800 

 1011 

 1330 

 1545 



5.96 

 5.94 

 9.20 

 13.28 



174.00 

 231.00 

 383.00 

 319.00 



29.20 

 38.91 

 41.61 

 24.02 



69.54 

 68.82 

 76.97 

 71.96 



23.28 

 23.01 

 17.98 

 22.87 



7.18 

 8.17 

 5.05 

 5.17 



15 Oct 90 

 15 Oct 90 

 15 Oct 90 



712 

 1141 

 1351 



7.79 

 6.53 

 7.24 



421.00 

 212.00 

 346.00 



54.05 

 32.48 

 47.80 



75.84 

 71.88 

 74.23 



18.37 

 20.58 

 20.08 



5.79 

 7.53 



5.69 



16 Oct 90 

 16 Oct 90 

 16 Oct 90 

 16 Oct 90 



728 

 937 

 1414 

 1606 



4.05 

 4.00 

 3.99 

 3.84 



216.00 

 183.00 

 225.00 

 203.00 



53.33 

 45.73 

 56.37 

 52.84 



79.88 

 75.02 

 69.39 

 72.63 



15.35 

 19.37 

 25.28 

 24.16 



4.77 

 5.61 

 5.33 

 3.21 



17 Oct 90 

 17 Oct 90 

 17 Oct 90 

 17 Oct 90 



710 

 919 

 1338 

 1550 



2.98 

 2.64 

 2.56 

 2.42 



182.00 

 86.30 

 82.50 

 92.20 



60.98 

 32.74 

 32.20 

 38.15 



76.85 

 72.70 

 74.50 

 69.16 



18.78 

 21.66 

 19.73 

 26.07 



4.36 

 5.64 

 5.77 

 4.78 



18 Oct 90 

 18 Oct 90 

 18 Oct 90 



700 

 1116 

 1311 



2.24 

 2.11 

 2.12 



104.00 

 83.80 

 90.10 



46.51 

 39.77 

 42.52 



69.63 

 70.68 

 62.11 



25.59 

 22.41 

 29.06 



4.78 

 6.91 

 8.83 



19 Oct 90 



710 



2.18 



75.50 



34.68 



70.80 



23.15 



6.05 



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



Another explanation for the observed large shoreline variances is that 

 nonlinear amplification of the swash could have occurred. A recent study by 

 Holland et. al. (1995) suggested that nonlinear amplification of swash variance 

 happens when the wave field is primarily standing. Using measurements of 

 runup from video and above-bed resistance wires and wave measurements from 

 pressure sensors located at various cross-shore positions, swash variance 

 amplification was found to be as much as four times the variance of the standing 

 wave profile. If this type of amplification occurred at the FRF site, it could 

 account for the unexpected large runup variance. Thus, the assumption of equal 

 shoreline amplitudes for each edge wave mode may be valid. Additional work is 

 required to resolve the relative contributions from nonlinear amplification effects 

 and selective trapping of modes with a bar/trough morphology. 



40 



Chapter 4 Field Observations 



