D / u 1 \ R /H' (rough slope) 

 R (rough slope) _ o ^ ^ 



R (smooth slope) 



(7-7) 



R/H' (smooth slope) 



Table 7-2 indicated the range of values of r for various slope character- 

 istics. 



This roughness and porosity correction factor is also considered 

 applicable, as a first approximation, in the analysis of wave runup on slopes 

 having surface materials with two or more different roughness values, r . 

 Until more detailed guidance is available, it is suggested that the percentage 

 of the total slope length, £ , subjected to wave runup of each roughness 

 value be used to develop an adjusted roughness correction value. This is 

 expressed by the equation 



*1 ^2 ^3 

 r (adjusted) = ~ ^i + ~ ^2"*" I~ "^3"^ " 



(7-8) 



where Z is the total slope length, I is the length of slope where the 

 roughness value T2 applies, £„ is the length of slope where the roughness 

 value Tj applies, and so on. This procedure has obvious deficiencies as it 

 does not account for location of the roughness on the structure and the vary- 

 ing interaction of slope roughness characteristics to the depth of water jet 

 running up the structure slope. 



Table 7-2. 



Value of 

 1974). 



r for various slope characteristics (after Battjes, 



The use of the figures to estimate wave runup is illustrated by the 

 following example. 



7-32 



