RECENT CONTRIBUTIONS OF WAVE RESEARCH 

 TO HARBOR ENGINEERING 



The following article was first published in limited 

 issue as Technical Report HE-116-267, Fluid Mechanics 

 Laboratory^ University of California „ It is re- 

 produced here to disseminate valuable wave concept 

 principles among coastal engineers and other persons 

 having an interest in the action of waves and surf , 

 The paper was prepared by Mr D J. W J6hnson 3 Univer- 

 sity of California s July 1948 = 



The planning and execution of the extensive amphibious operations dur- 

 ing the recent war stimulated extensive research in the problems of waves, 

 surf 5 and related phenomena „ The results of some of these investigations 

 have definite peacetime application to harbor engineerings and a review of 

 these developments to acquaint engineers with the methods appears desirable 

 at this time The principal problems that are discussed pertain primarily 

 to the compilation of basic design data and the use of these data in the 

 design,, constructions and operation of engineering structures exposed to 

 wave action o This discussion is confined to a consideration of waves 

 caused by wind Other waves, such as surging in harbors or seismic sea 

 waves are relatively less important in most engineering investigations „ 

 Only the broad aspects of the problem of wave action are presented; however , 

 sufficient references are given to permit the interested reader to study 

 further into the details of the techniques of application „ The principles 

 apply equally well to wave action either on the ocean or on lakes and pro- 

 tected baySo 



The Characteristics of Waves 



The waves under consideration in this paper are those generated by 

 the action of wind on the water surface. Such waves are characterized 

 primarily by two factors; the height which is the difference in elevation 

 between the trough and crest of the wave, and the period which is the 

 time between the passage of two consecutive crests past a fixed pointo 

 Other characteristics, such as wave length and wave velocity, may be 

 derived from the wave period The characteristics of the waves generated 

 in a particular storm depend on three factors: the fetch which is the 

 distance the wind blows over the water surface; the average speed of the 

 wind over the fetch; and the length of time that the wind blows „ In 

 general 3 the longer, farther, and faster the wind blows, the higher will 

 be the waves and the greater their period s length and velocity For a 

 particular fetch and wind speed there is a maximum wave height regardless 

 of how long the wind blows; or for a particular wind speedy either fetch 

 or wind duration might limit the maximum height,, 



On the Pacific Coast the height of the wave usually is limited by the 

 wind duration, because in the major genrating areas the fetches are so long 



