The empirical coefficients, a and g, are determined from labora- 

 tory experiments for the three breakwater types for water depth to wave- 

 length (d/L) ratios of 0.14 <_ d/L < 0.5. The definition of terms and 

 symbols is shown in Figure 1. Note that the crest width, B, is approx- 

 imately zero for the thin-wall breakwater, and B is approximately equal 

 to the water depth for the other breakwaters . 



In most design situations the general incident wind-wave conditions 

 are known and the desired wave conditions in the protected area are 

 established; therefore the height of a structure of given form can be 

 calculated. Rearranging equation (1) gives: 



(h - d,) 



201 , ■ / , 

 — Arcsm 1 



^Ht 



(2) 



which has been used to develop the design curves. Figures 2 and 3 are 

 dimensionless plots of [h - dg)/!^^ versus H^/H^ ; Figures 4 to 8 are plots 

 of equation (2) in English units. 



These curves can be used in several ways. If the incident height and 

 transmitted lieight are given, the crest height can be determined. If the 

 crest height is given and the incident height is known, transmitted height 

 can be approximated. 



III. SAMPLE DESIGN PROBLEMS 



The following examples demonstrate the use of the techniques presented. 

 Refer to the SPM (U.S. Army, Corps of Engineers, Coastal Engineering 

 Research Center, 1975)^ for useful information in a total design problem 

 (e.g., wave theory, a discussion of tides, storm surges, wave breaking). 



************** EXAMPLE PROBLEM i************** 



GIVEN : H^ = 5.0 feet, T = 4.5 seconds, and dg = 12.0 feet. 



FIND : The freeboard, (h - dg), of a vertical thin-wall breakwater with 

 H^ = 1.5 feet. 



SOLUTION : The design techniques in this memorandum apply to waves of 

 0.14 £ d/L £ 0.5; first, check the value of d/L as explained in the 

 SPM, Section 2.231, and using the tables in Volume III (U.S. Army, Corps 

 of Engineers, Coastal Engineering Research Center, 1975)^. In this 

 problem: 



d/Lo = 12.0/(5.12 X (4.5)2) ^ 0.II6 



lu.S. ARMY, CORPS OF ENGINEERS, COASTAL ENGINEERING RESEARCH CENTER, 

 op. cit . , p. 5. 



