H^/kj, values were close and would be expected to have only negligible 

 effect on comparison of the two experiments. The data of Hudson and 

 Jackson and of Ahrens can be compared for cot 9 = 2.5 or 3, as these 

 conditions overlap, when values are interpolated between experimental 

 conditions. For dg/H^ = 5.0, Ahrens* runup data, for both cot 6=3 and 2 

 (as extrapolated), are slightly lower than that by Hudson and Jackson. 

 Since Hudson and Jackson had the smaller H^/k^ value which represents 

 a larger roughness, the results are not quite as expected and the com- 

 parison is inconclusive regarding scale effects. The runup results of 

 Ahrens should be considered as of prototype scale and used without further 

 correction. 



Saville (1962) tested a 1 on 1.5 slope with three layers of riprap 

 at a large scale (dg = 4.57 meters (discussed previously in Sec. V,2,a)). 

 There are apparently no small-scale riprap test results that are com- 

 parable to Saville 's tests. His results are given in this study as 'r' 

 values from which approximate runup on riprap can be determined using 

 the smooth-slope curves (Sec. V,l,b). Since no small-scale tests are 

 available for comparison of scale effects, Saville's results would be 

 applicable as large-scale values. 



In summary, the runup scale-effect correction factor, k, for 

 rubble-mound structures of the type tested by Hudson (1958) (low core 

 height) is given in Table 22; i.e., k « 1.06 for steep structure slopes 

 tested at Rg = 1.33 x 10 6 , and applies to Figures 25, 26, and 27 derived 

 from Hudson's data. For Rg = 4.69 x 10 5 , k as 1.10 for steep structure 

 slopes. These factors are also recommended for quarrystone rubble-mound 

 structures with core heights at or above SWL, such as tested by Jackson 

 (1968) . 



Rubble-mound structures armored with concrete armor units of a 

 highly permeable design would be expected to have a runup scale effect 

 similar to that for quadripods (Table 23). A value of k * 1.03 would 

 apply to the appropriate tests by Jackson (1968) (see test results in 

 Table 11). 



Scale-effect results for quarrystone riprap slopes are inconclusive; 

 however, several sets of large-scale test data are available and should 

 be used directly, if possible (Saville, 1962; Ahrens, 1975a). The tests 

 of Hudson and Jackson (1962), when compared to large-scale tests, indi- 

 cate that little, if any, scale correction is required for runup results 

 derived from small-scale riprap (Rg > 4.7 x 10 5 ) ; however, comparable 

 wave conditions and structure designs are not available over the full 

 range of small- and large-scale tests. 



Runup scale effects on rubble structures fronted by a sloping beach 

 are not available. Until further studies are conducted, the values 

 given above are recommended for application to tests of small-scale 

 structures fronted by sloping beaches. 



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