The estimated rough-slope relative runup is then 



h) - Ah) 



° I rough \ o / smooth 



° trough 



= (0.52)(3.6) 

 1.87. 



The estimated runup is 



R rough 1 H' W-b' 



\ ° I rough 



'rough 



= (1.87) (2.2) 



^rough = ^-l meters (13.5 feet). 



Evaluation of possible scale effects is discussed in Section VI, 4. 

 ************************************ 



VI. SCALE EFFECTS 



1. General . 



The study of scale effects in runup has been limited. The SPM con- 

 tains runup corrections for smooth slopes based on work by Saville (1958) 

 Dai and Kamel (1969) studied scale effects on rubble-mound structures 

 sited on flat beaches, both for stability of armor units and for runup. 

 These studies incorporated tests from near-prototype conditions where 

 water depths at the structure toe were on the order of 3.0 to 4.6 meters 

 (10.0 to 15.0 feet). Other runup studies, while designed for a partic- 

 ular model-to-prototype scale, have implicit scale-effect data, in that 

 water depths at the structure toe were varied but wave conditions were 

 identical as measured by dimensionless variables. However, the model 

 scales usually vary only by a factor of two or so, and the effect is not 

 differentiable from variance in runup values for specified conditions. 

 Examples are given in Saville (1955, 1956). Hudson, Jackson, and 

 Cuckler (1957) used model scales differing by a factor of approximately 

 two in different wave tanks for a 1 on 6 smooth slope. Dai and Jackson 

 (1966) tested a rubble-mound structure with 1 on 2 slope on a beach of 

 ■1 on 30 slope at the structure and 1 on 370 farther seaward; model-to- 

 prototype scales of 1:50 and 1:100 were used. Their observations had a 

 great deal of scatter, and neither model scale showed consistently 

 higher nor lower relative runup values. Hudson and Jackson (1962) 

 studied riprap on slopes of 1 on 2 and 1 on 3 for two prototype depths, 

 two model scales, and differing prototype rock sizes. Ahrens (1975a) 

 tested riprap slopes at near-prototype scale. 



03 



