that the reflection will be defined by 



(?) 



H 



(182) 



H. 



(?) 



where c^ is a coefficient of roughness and permeability which has a 

 value of c^ = 0.8 for a smooth impervious beach. Various values of c^> 

 were defined for rough slopes for short -period waves. However, the 

 effect of the slope roughness on longer period waves has not been 

 adequately determined. 



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



EXAMPLE PROBLEM H************* 



GIVEN : A tsunami has a height of 0.5 meter and a period of 4 minutes 

 in a 1,000-meter water depth. The nearshore slope S3 = 0.01 (3 = 0.01 

 radians), and the slope is smooth and impervious. 



FIND: The coefficient of reflection H/H- at the shoreline. 



SOLUTION : In the deeper water, the wave celerity, C, is 



C = v^gd = /9.807 x 1,000 = 99 meters per second ' 



L = CT = 99 x 4 x 60 = 23,800 meters (14.8 miles) 



- = °- 5 - 2 10 x lO" 5 

 L 23,800 " 2 - 10 1U 



From equation (179), where $ is given in radians, 



/H \ = /2j\ 1/2 sin 2 g = / 2 x 0.01 \ 1/2 sin^(Q.Ol) 



VL/^Vtt/ TT \ IT / IT 



2.54 x 10 -6 



(?) 



H /H\ 

 L > V L A 



(?1 



H v _ w c _ 2.54 x 10-6 



7T- = c /u . = 0.8 :■=■ = 0.097 



H i r(V\ 2.10 x 10" 5 



(?) 



which indicates a low-reflected wave height where the shoreline has 

 a very gradual slope. 

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



90 



