runup and the r value determined for a particular relative roughness. 

 Since any one value of r, as given in this study, is an average, 

 uncertainties in the prediction are expected to be generally ±10 per- 

 cent but may be as high as 25 to 30 percent. 



Runup on rough slopes in cases where waves are breaking near the 

 structure toe (low dg/H^ values) is a common design situation for 

 which few experiments are availahle. The tests by Raichlen and Hammack 

 (1974) and Palmer and Walker (1970) both indicated a value of r * 0.5 

 for H^/k r % 2.0 and for 1 on 1.5 or 1 on 2 structure slopes fronted by 

 gently sloping bottoms. This value of r is equal to or less than that 

 determined for riprap slopes with thicker armor layers and with larger 

 d s /H^ values, for which waves did not break in front of the structure. 

 The result suggests that the available r values determined for larger 

 dg/H^ values are applicable, although possibly high, to estimates of 

 rough-slope runup for slopes and relative depths not tested but for 

 which smooth-slope results are available. Further testing is necessary 

 to clarify the relationships. 



Scale effects were investigated, but the number of large-scale test 

 results is limited. A correction curve for smooth slopes is given in 

 Figure 50. Data for analyzing rough-slope effects are even more limited 

 than for smooth slope. Tables 22 and 23 (both for cot 8 = 1.5) give 

 suggested values for quarrystone and quadripod rubble-mound structures. 

 Scale corrections for both steeper and gentler slopes would be expected 

 to be lower. Large-scale test results are available for riprap slopes 

 (Figs. 40, 41, and 42) and, if applicable, are recommended for use 

 without correction. 



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