34. DELAGE, G., "L'Utilisation d'un Brise-Lames Pour La Defence d'Une 

 Plage" (Breakwaters Used for Beach Protection) , Proceedings of the 

 Fifth Conference on Coastal Engineering, American Society of Civil 

 Engineers, 1954, pp. 479-494 (in French). 



Keywords: Accretion, Currents, Detached breakwater, Hydraulic model 



(two-dimensional). Hydraulic model (three-dimensional). Lit- 

 toral transport, Submerged breakwater, Wave attenuation. Wave 

 transmission 



This study consists of two parts. The first part discusses the 

 effect of the presence of a breakwater on the profile of a beach. The 

 tests were preceded by a study of the kind of disturbance arising behind 

 a breakwater, which causes the occurrence of harmonics of the incident 

 wave. The different types of breaking over the structure resulting from 

 the characteristics of the incident wave and the layout of the structure 

 were also observed; three typical types were noted: a horizontal jet of 

 water, a descending jet, and partial breaking. 



The second part discusses the layout of an immersed breakwater in- 

 tended for local beach protection. The characteristics of the protection 

 were studied to find the most favorable compromise between the protection 

 desired and the danger of erosion. The influence of the duration of wave 

 action from different directions plays an important part in determining 

 the characteristics of the structure. 



35. DICK, T.M., and BREBNER, A,, "Solid and Submerged Breakwaters," 

 Proceedings of ths 11th Conference on Coastal Engineering , American 

 Society of Civil Engineers, Vol. II, 1968, pp. 1141-1158. 



Keywords: Hydraulic model (two-dimensional), Impermeable breakwater, 



Permeable breakwater. Submerged breakwater. Wave reflection. 

 Wave transmission 



This paper reexamines the behavior of thin and rectangular solid 

 submerged breakwaters. Dean's theory is found to be correct for a thin 

 barrier in infinitely deep water. An empirical and theoretical relation- 

 ship for the reflection coefficient of a thin breakwater across the wave 

 number spectrum is proposed. Rectangular solid breakwaters have a maxi- 

 mum reflection when the incident wave has the same period as a standing 

 wave on top of the breakwater and with a wavelength equal to the crest 

 width. A submerged permeable breakwater for depths of submergence great- 

 er than 5 percent of the total depth transmits less wave energy than the 

 solid over a certain frequency range. The minimum is transmitted when 

 the criterion above for solid breakwaters is also met. Both permeable 

 and solid rectangular breakwaters cause a substantial loss in wave energy 

 and at least 50 percent of the incident energy is lost to turbulence. A 

 substantial proportion, 30 to 60 percent, of the energy transmitted is 

 transferred to higher frequencies than the incident wave. 



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