0.1 0.2 0.3 0.4 0.6 0.8 I 2 3 4 6 8 10 20 30 40 60 80100 



Structure Slope (Cot 9) 



Figure 7. Relative runup for smooth slopes on a 1 on 10 bottom; 

 2,/L > 0.5; d s /H£ = 1.0 (from Stoa, 1978). 



1.0 



1.0 



H s 0.40 + (H s /L ) 1/2 cot 6 0.40 + (1.08/39.01) (1.5) 

 and the maximum runup is 



• 5 > - (M(fe) 



= 1.54 



= R s (1. 



(1.5) = (1.08)(1.54)(1.5) 



= 2.49 meters (8.17 feet). 



Computations shown above were performed for the other slopes and are tabu- 

 lated in Table 6. Table 6 also shows some additional data (e.g., the length 

 of the revetment) to provide information for comparing the advantages of the 

 various slopes. The length of the revetment is the slant length distance 

 from the toe to the top of the riprap as determined by the chosen value of 

 RmaxJ i.e., length of revetment = (d s + Rm ax ) (1 + cot 2 G) 1 /2. 



Table 6 shows that the 1 on 1.5 slope has the shortest length and re- 

 quires the smallest quantity of armor per meter. The length for each slope 

 was calculated using Rmax as estimated by the method of this report. The 

 weight of stone per meter is the product of r min , the slope length, the 

 unit weight, and 1.0 minus the porosity. The unit weight is 2,644 kilograms' 

 per cubic meter and the porosity is assumed to be 0.40. Since the 1 on 1.5 

 slope needs the least armor stone per meter it may have the lowest first 

 costs; however, in some locations it might be cheaper to purchase smaller 

 stone for a flatter slope. Problems with the 1 on 1.5 slope include the 



27 



