is S 2 = 0.003. The angle between the reflected wave ray and the 

 orthogonal to the shoreline o^ = 45°. 



FIND : 



(a) The minimum shelf slope required for trapped waves to exist, 



(b) the radius, r„, defining the outer limit of the trapped wave 

 zone where aj = 45°, and 



(c) the minimum period of waves trapped by refraction, where oj = 45' 

 SOLUTION : 



(a) From equation (288) , for wave trapping to exist 

 d* 



S R* 

 2 s 



S > 2 — = 2(50) = 0.0006 



L R* 100,000 



s 



(b) The shelf parameter is 



d * 30 30 



0.1 



S R* 0.003(100,000) 300 



From Figure 38, for a, = 45°, the minimum wave period is at 



where 



2tt d* n 



— - = 0.068 



gT 2 



n 2 dj 



5 = 0.71 

 R* 

 s 



2 n -, R s _ _. 100,000 -,_ 



d* 30 



s 



and 



n- = 48.65 



R* 



— = 0.93 

 r* 



P 



129 



