to 0.6 has been recommended for rough slopes and step-faced structures 

 The second factor 



X2 is given by 



01 o 



01 o 



(2-86a) 



'\L 



(2-86b) 



where (n^/Lo^rnax 



'o I \ o /max 



is constant for a particular beach slope and is given by 



H, 



(2-87) 



in which 3 is the angle the beach makes with the horizontal (tan B = 

 beach slope) , and Hq/^q is the incident wave steepness in deep water. 

 ^^o/^o^max '-^^ ^® considered a cut-off steepness; waves steeper than 

 (H^/L^^max will be only partially reflected while waves with a steepness 

 less than (Mo/^o^max "iH ^e almost totally reflected. Equation 2-87 is 

 given in graphical form in Figure 2-62, and Equation 2-86 is shown in 

 Figure 2-63. These equations and figures are valid for impervious beaches 

 with waves approaching at a right angle to the beach. 



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



EXAMPLE PROBLEM 



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



GIVEN : A wave with a period of T = 10 second, and a deepwater height of 

 Hq = 5 feet impinges on an impermeable revetment with a slope of tan 3 

 = 0.20. 



FIND : 



(a) Determine the reflection coefficient x. 



(h) What will be the steepest incident wave almost totally reflected 

 from the given revetment? 



SOLUTION. Calculate: 



512 feet. 



512 



« 0.01 



2-118 



