Table 10. Values of r for quarrystone riprap, 

 1 on 1.5 slope (armor layer three 

 stones thick on impermeable base) 

 (after Saville, 1962) . 



d s /H' 



H^/k r 



Slope (cot 9) 



r 



5.0 



3.0 



1.5 



*0.6 



8.0 



1.9 



1.5 



«0.625 



Hudson and Jackson (1962) tested riprap at small scales (Fig. 33) 

 using two structure slopes, 1 on 2 and 1 on 3, both on a horizontal 

 tank bottom. Although wave conditions were somewhat limited, a range 

 of armor and underlayer stone sizes were tested. Runup curves based 

 on these tests are given in Figure 34. The curve shapes are similar 

 to those of the smooth-slope curves and to the rubble-mound curves. 



Analysis of smooth-slope scale effects (see Sec. VI) indicates that 

 scale effects between the various small-scale tests conducted by Hudson 

 and Jackson (1962) would be negligible. Accordingly, the data were 

 evaluated for stone-size effects combining all data from the various 

 model scales. No clearly discernible trend in effects of stone size 

 was found for the 1 on 2 slope; an r value of approximately 0.625 

 appears appropriate (Fig. 35) for the various H^/k r values. However, 

 the 1 on 3 slope shows increasing r values with increasing H^/kj, 

 values (Fig. 35) . The lines through the data in the figure are some- 

 what arbitrary, but the trends seem consistent with those in Figures 

 31 and 32. 



Palmer and Walker (1970) tested runup on a 1 on 1.5 rubble slope on 

 a 1 on 50 beach (Fig. 33) , and gave their results in a set of curves 

 using different variables than those in this study. Conversion of their 

 results for selected data sets gives the points shown in Figure 36. 

 Smooth-slope runup data for similar conditions are not available for 

 comparisons. However, for larger dg/H^ values, runup values for a 

 structure on a flat beach would be expected to be comparable to runup 

 on the same structure sited on a 1 on 50 beach. Comparisons between 

 Palmer and Walker's values and values for smooth structure slopes 

 fronted by a horizontal beach give extremely low r values for the 

 larger d s /H£ values (r « 0.38 for dg/H^ = 3.0, H^/k^ w 1.5 and 

 r «0.26 for d s /H^ = 5.0, H^/k^, = 0.9). It is unclear why the values 

 are so low, but part of the reason may be in the difficulty of measur- 

 ing runup on a slope with relatively large stones (H^/k^, small). Palmer 

 and Walker's runup values for dg/H^ = 1.5, when compared with runup 

 values for a smooth structure slope fronted by a 1 on 10 beach, gave a 

 value of r «0.5 for dg/Hi = 1.5 and H£/k r « 2.9. 



A useful aspect of Palmer and Walker's curves is that breaking con- 

 ditions are given, where breaking is the depth-controlled condition; 

 i.e., waves are breaking at or seaward of the toe of the structure. 



76 



