Guza, and Thornton 1981). The first in a series of such arrays was part of 

 the Nearshore Sediment Transport Study (NSTS) at Torrey Pines beach, 

 San Diego, in 1978. Two-dimensional f-k spectra for 2 consecutive days showed 

 a lower limit of 30 ± 15 percent of the energy in the longshore current fre- 

 quency band (0.006 to 0.023 Hz) to lie either on the mode or 1 edge wave 

 dispersion curves (Equation 2). The cross-shore current, while also contain- 

 ing low-mode edge waves, had spectra that had leaky and/or high-mode edge 

 waves, often masking the low modes. 



19. Oltman-Shay and Guza (1987) analyzed longshore array data from both 

 the Torrey Pines 1978 and Santa Barbara 1980 NSTS field sites. Surf-zone 

 infragravity energy on a total of 15 days studied at both beaches was always 

 found to contain edge waves. Again, f-k spectra (Figure 4) were used to dem- 

 onstrate the concentration of energy along the edge wave dispersion curves 

 (Equation 2). Longshore current energy was observed to consist of 70- to 90- 

 percent low-mode edge waves. Cross-shore currents also contained low-mode 

 edge waves (i.e., 20 percent), but spectra were often dominated by low wave 

 number energy that probably consisted of a combination of unresolvable high- 

 mode edge waves and/or leaky waves. Another complication in resolving long 

 waves in the cross-shore current may be partial phase locking (Huntley, Guza, 

 and Thornton 1981). However the observation of high modes in the cross-shore 

 current does not contradict the dominance of low modes in the longshore cur- 

 rent because high-mode and leaky wave velocities have their largest component 

 in the cross-shore current direction at the arrays. These data demonstrated 

 that the nearshore infragravity field contains significant amounts of low-mode 

 edge waves in the nearshore current and elevation field. 



20. It is generally accepted that bounded long waves propagate from 

 deep water with the incident wave groups. Huntley and Kim (1984) and List 

 (1987) have demonstrated that significant amounts of the total variance (i.e., 

 25 percent) in the infragravity band outside the surf zone come from bounded 

 long waves. Free long wave (edge and leaky) energy is generated in shallow 

 water by Gallagher's (1971) or Symonds , Huntley, and Bowen's (1982) mechanism, 

 the latter occurring only within the surf zone. The mechanisms of Gallagher 

 and Symonds, Huntley, and Bowen can generate both leaky and edge waves (the 

 Symonds generation model is presented in two dimensions and thus can generate 

 only normally incident leaky waves; however, the extension to three dimensions 

 is clear). Although it is possible that free leaky waves can propagate from 



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