wave length of the incident wave period, and the slope of the seaward face. 

 Values of a and b have been derived by Seelig (1980a) from monochromatic 

 laboratory data for riprap revetments (graded quarrystone) on an impermeable 

 surface, uniform quarrystone on both highly permeable and conventional multi- 

 layered breakwaters, and for dolosse on conventional multilayered breakwaters. 

 From experiments with conventional multilayered breakwaters, additional values 

 have been fit for this report to monochromatic runup data taken by Jackson 

 (1968b). The values of these runup coefficients are presented below in Ta- 

 ble 5 along with the linear correlation coefficient r to the data from which 



Table 5 

 Runup Coefficients 



Armor Unit 



a 



b 



r 



Data Source 



Riprap 



(revetments) 



0.956 



0.398 



Ahrens and McCartney (1975), 

 impermeable base 



Quarrystone 

 (breakwaters) 



0.692 



0.504 



— 



Hudson (1958), 



highly permeable core 



Quarrystone 

 (breakwaters) 



0.775 



0.361 



-- 



Gunbak (1976), 

 multilayered 



Modified Cubes 

 (breakwaters) 



0.95 



0.69 



0.91 



Jackson (1968a), 

 multilayered 



Tetrapods 



(breakwaters) 



1.01 



0.91 



0.76 



Jackson ( 1968a), 

 multilayered 



Quadripods 

 (breakwaters) 



0.59 



0.35 



0.83 



Jackson (1968a), 

 multilayered 



Hexapods 



(breakwaters) 



0.82 



0.63 



0.78 



Jackson ( 1968a) , 

 multilayered 



Tribars 



(breakwaters) 



1.81 



1.57 



0.78 



Jackson (1968a), 

 multilayered 



Dolosse 



(breakwaters) 



0.988 



0.703 



— 



Bottin, Chatham, and Carver (1976), 

 multilayered 



they were derived. The relation of the runup predicted using these units as a 

 function of ^ is illustrated in Figure 12. An important feature to note is 

 that some armor unit types may have runup advantages over other types in that 

 they can be more efficient energy dissipaters with respect to runup. Some of 

 this effect may be due to variations in underlayer material size and porosity 

 that are functions of the primary armor unit weight as well as the total depth 

 of the primary armor. This means that breakwaters built with certain heavier 



48 



