preferably range from 0.08 (deep water) to values in the shallow-water 

 range (d s /gT 2 < 0.0016); dg/H^ should range from a large value (such 

 as 15) to as small a value as possible. The range of dg/H^ selected 

 should be low enough to include, on sloping bottoms, waves which are 

 breaking seaward of the structure toe. (Note that wave steepness is 

 determined when dg/gT 2 and dg/H^ are specified.) Waves incident to 

 a structure sited on a horizontal bottom should be of the maximum wave 

 steepness possible. 



(b) Auxiliary data to be obtained include the observation of 

 whether or not a wave is breaking for the specific incident wave con- 

 ditions. The location of breaking (even when the wave breaks at a 

 point over the structure slope) should be noted, and the breaking wave 

 height should be determined. 



(c) Tests of runup on structures fronted by gentle bottom slopes, 

 e.g., 1 on 20 to 1 on 50 or flatter, are desirable. A large amount of 

 runup data has been obtained for smooth slopes fronted by 1 on 10 bottom 

 slopes, but such a steep bottom slope is unrealistic for most applica- 

 tions. Emphasis should be given to the range 1 < dg/H^ < 3, for which 

 waves would be expected to break near the structure toe, and where maxi- 

 mum runup would be expected. For such tests, measurement of the break- 

 ing wave height, along with runup, would be extremely useful, since, in 

 conjunction with the corresponding wave height in deeper water, a breaker 

 height index (H^/H^) could be developed. This index would then be 

 applicable for waves approaching a structure. Breaker height index 

 curves in the SPM are derived from tests conducted on uniform slopes 

 which extend from above water level to the maximum depth. Jackson 

 (1968b) reported test results of maximum breaking and nonbreaking wave 

 heights incident to a rubble-mound structure sited on sloping and on 

 horizontal bottoms. The breaker heights observed by Jackson are lower 

 than calculated from the design curves; however, calculation of the 

 deepwater variables (and thus the breaker height index) from the avail- 

 able data is not possible. 



(d) Testing of runup on rubble-mound and riprap structures sited 

 on sloping bottoms has been limited; however, this arrangement, in 

 conjunction with waves breaking at the structure toe, is the design 

 condition in many instances. Additional testing is required. A range 

 of bottom slopes and structure slopes is desirable, and a rather steep 

 rubble-mound slope (e.g., cot = 1.5) should be included. Low dg/H^ 

 values (1 < dg/H^ < 3) would ensure that data are acquired for waves 

 which are breaking at or in front of the structure toe. 



(e) Testing the effect of beach-slope length is recommended, but 

 the importance of the length is expected to diminish with gentler bottom 

 slopes. Such testing could be accomplished by holding conditions con- 

 stant at the structure toe (e.g., constant d g , dg/H^, and H^/gT 2 ) and 

 varying the length of beach slope (i.e., varying the depth, d, at the 



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