ESTIMATION OF WAVE TRANSMISSION COEFFICIENTS 

 FOR OVERTOPPING OF IMPERMEABLE BREAKWATERS 



by 

 Willicm N. Seelig 



1. INTRODUCTION 



When a wave strikes an Impermeable breakwater, some of the water may over- 

 top the breakwater and produce regenerated waves. Section 7.233 of the Shore 

 Protection Manual (SPM) (U.S. Army, Corps of Engineers, Coastal Engineering 

 Research Center, 1977) and Seelig (1976) give a method for estimating trans- 

 mission by overtopping coefficients for smooth, vertical -faced breakwaters 

 overtopped by monochromatic waves. Wave period effects are not considered. 

 This report presents a more general method of predicting transmission by over- 

 topping coefficients that includes the influence of structure slope (nonvertical 

 as well as vertical), crest width, roughness, wave period, and wave type (ir- 

 regular and monochromatic waves) . The method is based on laboratory tests for 

 d/gT^ < 0.03, where d is the water depth, g is the acceleration due to 

 gravity, and T is the wave period. Figure 1 shows the case of transmission 

 for an impermeable breakwater and illustrates some of the terms used. Methods 

 described in this report apply to breakwaters xd.th an impermeable surface, an 

 impermeable core, or an impeinneable diaphragm to prevent wave transmission 

 through the structure. 



Kto =h- 



1i 



Figure 1. Wave transmission by overtopping of an impermeable breakwater. 



II. ESTIMATION OF TRANSMISSION COEFFICIENTS 



Laboratory data show that the coefficient of wave transmission by over- 

 topping for an impermeable breakwater, Ktq, can be predicted using (Seelig, 

 1980). 



To Hi \ R 



(1) 



where F/R is the ratio of the breakwater freeboard to wave runup suggested 

 by Cross and Sollitt (1971) , and C is the empirical given by 



