From equation (211) , 



fd l/2 _ d l/2) 



T-ii-2 ^— . n= 1, 2, 3, . . . 



n S 2 gl'* 



„, 8 C60 1/2 - 30 1/2 ) 5,800 



T = = ,n=l, 2, 3, . • • 



n 0.001 (9.807) 1/2 n 



T = 5,800 seconds (96.7 minutes), n = 1 



T 2 = 2,900 seconds (48.3 minutes), n = 2 



T. = 1,933 seconds (32.2 minutes), n = 3 



T = 1,450 seconds (24.2 minutes), n = 4 

 etc. 



************************************* 



Nagaoka (1901) considered the possibility of currents parallel to the 

 coast acting as boundaries which would reflect waves. He speculated that 

 the currents would act as quasi-elastic boundaries. In this case waves 

 generated near a shoreline could be trapped between the shoreline and an 

 offshore current, creating a resonant condition between two boundaries. 



4. Edge Waves . 



The impulse of incident waves reflecting from the shoreline may 

 generate edge waves in the longshore direction. These edge waves, the 

 trapped mode of longshore wave motion, have wave periods which will be 

 longer than the incident wave periods; standing edge waves will have 

 peaks and nodes at points along the shoreline, although edge waves may 

 be either standing or progressive waves. Guza and Bowen (1975) indicate 

 that experimental results confirm the work of Galvin (1965) and Bowen 

 and Inman (1971) which show that incident waves that are not strongly 

 reflected will not excite edge waves visible at the shoreline. 



Guza and Inman (1975) have defined the water surface profile of edge 

 waves in the seaward direction using the dimensionless wave amplitude, 

 U, and a dimensionless distance, x> i- n tne seaward direction given as 



(212) 



g tan 3 



where ui is the radian frequency (2ir/T) of the edge wave, x the dis- 

 tance measured from the shoreline in the seaward direction, and 3 the 

 angle of the nearshore slope (tan g = S) . The water surface profile is 

 given in Figure 34 which shows that higher modes of standing edge waves 



101 



