Values of r used in Table 16 are averages for several wave steep- 

 nesses. In tests of structures sited on flat bottoms, the r value 

 does not seem significantly influenced by varying wave steepness values. 

 Saville's (1955) data (Table 16) show high r values for steep waves 

 (H^/gT 2 « 0.006 and greater); individual r values were as high as 0.93. 

 These high r values may be a result of the measurement of maximum values 

 of runup or an expression of the lesser importance of roughness when waves 

 break seaward of the structure toe. 



Jachowski (1964) and Nussbaum and Colley (1971) tested stepped slopes 

 sited on flat bottoms. Both tested 1 on 2 and 1 on 3 structure slopes 

 using vertical-faced steps with sharp edges. Jachowski also tested inter- 

 locking blocks with inclined risers (upper edge seaward of lower edge). 

 Nussbaum and Colley also tested steps with rounded edges which would 

 represent eroded or worn conditions for the soil-cement steps. Selected 

 data of Jachowski and of Nussbaum (personal communication, 1975) were 

 reviewed and compared to smooth-slope runup values. 



Table 18 indicates r values of approximately 0.70 for vertical- 

 faced steps, although the 1 on 2 slope appears to have slightly higher 

 values. The rounded-step slopes have significantly higher r values, 

 as would be expected, and have values of r %0.85. 



4. Estimation of Rough-Slope Runup . 



Most runup tests have been conducted for restricted conditions. Some 

 structure configurations or wave conditions have not been tested or have 

 been tested only rarely. Few runup data are available, for example, 

 for a rubble structure fronted by a sloping beach and for which waves are 

 breaking at the structure toe. Actual runup tests for design conditions 

 are the most desirable means of estimating runup under prototype condi- 

 tions. In lieu of test results, some method of estimation is necessary. 



This study has presented rough-slope runup data in terms of the fac- 

 tor r, which is the ratio of rough-slope runup to smooth-slope runup 

 for the same conditions. Such a factor was suggested by Hunt (1959), 

 the U.S. Army, Corps of Engineers, Coastal Engineering Research Center 

 (1966), and the Technical Advisory Committee on Protection Against 

 Inundation (1974). This factor, as envisioned, would vary simply as a 

 function of the structure's armor layer construction. It would be 

 applied to known smooth-slope runup values to estimate rough-slope 

 runup for conditions not tested. Actually, the factor r appears to 

 be as highly dependent on the several wave and structure conditions as 

 relative runup, R/H^. For example, the range of individual r values 

 for quarrystone riprap slopes was, for 4 < dg/H^ < 10 and 1.5 < H^/k^ < 5 

 and the slopes noted: 1 on 1.5, 0.53 < r < 0.68; 1 on 2.5, 0.51 < r < 0.69: 

 1 on 3.5, 0.43 < r < 0.67; 1 on 5, 0.44 < r < 0.79. Thus, any one value 

 of r does not seem applicable for all wave conditions for a given armor 

 unit; however, values of r are still useful as estimators of runup on 

 rough slopes when smooth-slope data are available and rough-slope data 

 are lacking. 



100 



