VII. SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS 



The primary conclusions from the tests of wave transmission and reflection 

 of laboratory breakwaters conducted for this study are: 



1. A simple formula for predicting wave transmission by overtopping 

 coefficients together with the model of Madsen and White (1976) for trans- 

 mission through permeable structures can be used to obtain estimates of wave 

 transmission coefficients. 



2. Limited tests with breaking waves suggest that the methods can be 

 used for breaking or nonbreaking conditions. 



3. Tests with irregular waves show that the transmission coefficient for 

 irregular waves is approximately the same as for a similar monochromatic wave 

 test. The mean wave height and period of peak energy density are the param- 

 eters recommended to describe irregular waves. 



4. Irregular wave tests indicate that for permeable or submerged break- 

 waters the incident and transmitted wave height distributions have similar 

 shape. However, smooth impermeable subaerial breakwaters have height distri- 

 butions biased toward the larger heights for irregular waves because large 

 waves transmit more efficiently than small waves. 



5. Transmitted and reflected spectra for irregular waves generally have 

 equal or higher spectral peakedness than incident spectra. 



6. Joint wave height-period distributions have similar dimensionless 

 shapes for incident and transmitted wave records. 



7. There is a tendancy for wave heights to be less grouped after they 

 have transmitted past a breakwater. 



8. Transmitted wave energy may appear at higher order harmonics of the 

 incident waves for monochromatic wave tests. However, the tendancy for energy 

 shifts decreases as the wave transmission coefficient increases. 



9. Additional work is necessary to develop generalized models for predict- 

 ing wave reflection coefficients and wave transmission through the crests of 

 breakwaters armored with relatively porous materials, such as concrete armor 

 units . 



The recommended steps for design of a breakwater for wave transmission are: 



1. Use the computer programs MADSEN and OVER to estimate transmission 

 coefficients for preliminary breakwater design. Alternative designs can be 

 tested by varying parameters such as: 



(a) structure height 



(b) crest width 



(c) seaward and landward breakwater slopes 



(d) water depth 



(e) number, thickness, location, and diameter of materials 



(f) porosity 



(g) permeability 

 (h) wave height 

 (i) wave period 



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