saturated region of the run-up energy spectra. In contrast, Huntley, Guza , 



-4 

 and Bowen (1977) observed roll-off slopes of frequency . Guza and Thornton 



concluded that there does not appear to be a 'universal' run-up spectra as 



Huntley, Guza, and Bowen postulated. It should be noted that this experiment 



was performed with a wide range of incident wave heights, a single beach 



slope, and a narrow range of peak incident wave frequencies. 



Guza, R. T., and Thornton, E. B. 1985. "Observations of Surf 

 Beat," Journal of Geophysical Research, Vol 90, No. C2, 

 pp 3161-3172. 



Cross-shore velocities and elevation oscillations were analyzed from 

 three different experiments. At surf-beat frequencies these motions were sig- 

 nificantly correlated with the significant heights of the incident waves. The 

 measured cross-shore velocity variance at surf-beat frequencies was between 10 

 and 100 times larger than the variance at 5-m depth. Numerical integration of 

 the shallow-water wave equations for standing waves on a beach was used to 

 model infragravity waves in the nearshore. Measured surf-beat run-up spectra 

 was coupled with these numerically integrated equations to predict the energy 

 spectrum at offshore locations and the coherence and phase between a run-up 

 meter and the predicted offshore data. A qualitatively good agreement was 

 found between the observations and the standing wave solutions. 



Holman, R. A. 1981. "Infragravity Energy in the Surf Zone," 

 Journal of Geophysical Research, Vol 86, No. C7, pp 6442-6450. 



This article is an excellent introduction for describing the infragrav- 

 ity motions on real beaches, as well as for summarizing previous work of other 

 investigators. A theoretical section was included describing edge wave kine- 

 matics and dynamics which presented pertinent equations for the infragravity 

 motions but omitted the detailed derivations. An interesting result was found 

 in the response of the infragravity motions to changes in the incident wave 

 field. Theoretical arguments predicted that the infragravity amplitudes 

 should vary linearly with the incident wave amplitudes. Field data collected 

 during low- and high-energy periods supported this dependence. However, 

 energy in the incident wave band was limited in the surf zone as a result of 

 wave breaking. This indicated that infragravity energy will dominate the surf 

 zone during storms. Spectral transformations were used for generating a spec- 

 trum at a particular offshore location given a white shoreline spectrum with 

 unit energy density. Cross-shore (onshore) velocity spectra exhibited signif- 

 icant structure in the infragravity band. However, the transformation showed 

 that most of the structure was a result of instrument position and did not 

 represent frequency selection. This indicated the importance of instrument 

 location for measuring infragravity motions. In addition, it was noted that 

 an increase in the directional spread of the incident waves would tend to gen- 

 erate edge waves of many modes. Thus, it may be easier to measure edge waves 

 on the Pacific coast, as opposed to the Atlantic coast, where there is often 

 narrow band incident swell which should produce only a few low-mode edge 

 waves. 



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