58 



eH eh 0-75 

 ^ = 0.126 (^) 



U U 



(5.11) 



It follows that 



|g = (0.126)(0.75) (^) 



= 0.75ii 



(5.12) 



and it is clear that wave height will increase with water depth. Wave 

 period follows an expression similar to Eq. 5.10 



gT 



27rU 



1.20 tanh[ 0.833 (^) 

 U 



0.375 



] tanh - 



0.077 (^) 

 U 



0.25 



.gh 



0.375 



L tanh[0.833 (^) ] J 



U 



(5.13) 



which in shallow water becomes 



27rU ''2'' 



(5.14) 



so that 



3T 



ah 



(27r)(0.375) 

 U 



(^] 



-0.625 



T 



,375 i 



n 



(5.15) 



and it is apparent that waves become longer as sea level rises . 



After a wave leaves the storm area where it was generated, bottom 

 friction will drain energy and reduce its height, but should not alter wave 

 period. The losses due to friction can be expressed by the equation 



