estimated by an examination of past weather charts (in the case of the sea 

 coast) or from wind records (for a lake or bay) „ The principles of re- 

 fraction and diffraction permit a designer to determine the characteristics 

 of these same waves at any other point after they have moved shoreward „ 

 That location where a structure will receive the most favorable protection 

 from wave action, therefore,, can be selected with confidence,, 



It should be recognized that maximum stresses are developed when 

 waves break directly on a structure „ Even though wave heights at a 

 structure may be less than the offshore waves , as a result of refraction 

 or diffraction , the breaking of these waves may induce relatively high 

 stresses i consequently, the expected point at which waves will break 

 should be considered in the final analysis of a design „ In some cases it 

 is possible to avoid excessive stresses induced by breaking waves, by 

 orienting the structure such that much of the wave energy is reflected by 

 the structure itself, or much of the wave energy may be dissipated by 

 forcing the wave to break before it reaches the structure 



As previously mentioned, wind generated waves usually are the most 

 important to consider in harbor design „ However, in areas subject to long- 

 period ground swell, surging often becomes a serious problem because the 

 period of the ground swell may be close to the fundamental, or first, or 

 second harmonic of the natural period of oscillation of the body of water 

 within the harbor „ In many instances the natural period of a basin and, 

 therefore the possibility of surging, can be determined by simple com- 

 putation from the dimensions of the body of water,, In harbors of re- 

 latively complicated dimensions, however, a resort to model studies may 

 be necessary to completely solve the problem of surging,, 



Acknowledgment 



Yfith the exception of the v\ave forecasting method which was develop- 

 ed at the Scripps Institution of Oceanography, La Jolla, the various 

 developments described above resulted from investif ations made at the 

 University of California by the Department of Engineering, Berkeley 

 This work was sponsored by the Bureau of Ships and the Office of Naval 

 Research, 



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