such a harbor is not only difficult, but the necessity to design the har- 

 bor to provide adequate protection for the larger ships from wave action 

 becomes more acute. In addition, the problem of keeping harbor and port 

 accommodations in balance with the requirements of "superships," now in 

 operation or proposed, is international in scope and importance. 



A great interest in small-boat ownership has developed in recent 

 years. About 50.5 million people in the United States participated in 

 recreational boating in 1976, more than 10 million boats used U.S. water- 

 ways and harbors, and about 6,000 small- craft harbors, and yacht and 

 boating clubs provided berthing spaces and other services to boat owners 

 (Cahners Publishing Co., Inc., 1977). 



The problems of harbor design in providing adequate protection from 

 wave action include: (a) Location of the harbor to ensure that the maxi- 

 mum possible protection from wave action is obtained; (b) determination 

 of the location, alinement, height, and type of breakwater required to 

 provide adequate wave protection; (c) determination of the best location, 

 orientation, and dimensions of navigation openings to provide vessels 

 safe and easy passage into and out of the harbor without impairing the 

 wave protection characteristics of the harbor works; and (d) the position- 

 ing of spending beaches and other forms of wave absorbers inside the har- 

 bor area. Except for the deepwater harbors required for the new and large 

 deep-draft vessels, either in use or proposed, the engineer is seldom con- 

 sulted in the selection of sites for large commercial harbors, since most 

 locations have been determined by industrial, transportation, and other 

 economic requirements. However, in the case of small-craft harbors, the 

 engineer is more likely to be employed at the start of the project, and 

 is in a good position to provide the proper technical input to the prob- 

 lems of site selection. The first step in the solution of harbor prob- 

 lems is to select the types of waves for which protection will be required, 

 and to obtain enough information relative to wave dimensions, directions 

 of approach, and frequency of occurrence to enable the judicious selec- 

 tion of design wave characteristics. The complexity of wave action phe- 

 nomena and the complicated geometry of most harbors cause difficulty in 

 obtaining adequate answers to design problems strictly by analytical 

 means. Thus, the hydraulic scale model is commonly used as an aid in 

 the planning of harbor development, and in the design and layout of break- 

 waters and wave absorbers to obtain optimum protection from wave action. 



In designing harbors, the engineer is concerned with the (a) short- 

 period waves generated by stormwinds (those generated by local or near- 

 local storms are usually referred to as "sea," and waves generated by 

 distant storms, when they arrive at or near shore, as "swell") with 

 periods from about 1 to 25 seconds and heights from about 1 to 40 feet 

 or more; (b) intermediate-period waves with periods from about 25 seconds 

 to 2 minutes; and (c) long-period waves from about 2 minutes to 1 hour. 

 The origins of the intermediate- and long-period parts of the wave spectra 

 that generate forced oscillations in harbor basins, which in turn may 

 cause troublesome or dcimaging ship or boat surging, are not specifically 

 known; however, the origins are believed to be the result of atmospheric 



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