In large marinas with entrance problems, it may be necessary to prohibit the tacking of 

 sailboats and require them to negotiate the entrance channel on auxiliary power under 

 peak -hour conditions. 



Although no criteria have been established for determining the width of an ocean 

 entrance channel where boat traffic is a controlling factor, a good practice is to provide a 

 navigable width of 300 feet for the first 1,000 boats, plus an additional 100 feet for every 

 additional 1,000 boats berthed in the harbor including the daily launching capacity of 

 operational ramps and hoists. In 1973, Marina Del Rey (see Sec. VIII) berthed about 6,000 

 boats; its entrance has a navigable width of about 700 feet (versus 800 feet by the above 

 rule), and has recently begun to experience an entrance-congestion problem on peak days. 

 The harbormaster has solved this problem successfully, by creating lanes to separate 

 powercraft and sailcraft entering and leaving the harbor. The system is not regulated by 

 ordinance, but requires the voluntary cooperation of the boaters. Newport Bay, Cahfornia 

 (Fig. 25) is a natural harbor with a jettied entrance channel of about the same length as that 

 of Marina Del Rey, but skewed to the general alinement of the coast so that the daily sea 

 breeze is quartering. The navigable channel width ranges from about 500 to 700 feet, and 

 the bay contains about 8,000 powercraft and sailcraft. Long reaches of cruising waters 

 within the bay satisfy many small sailboat owners so that they seldom use the entrance. 

 Assuming that 1,000 boats are in this class, the required entrance channel width would be 

 900 feet. Although the channel is overcrowded on peak days, its orientation with respect to 

 the prevailing winds reduces the requirement for sailboat tacking. Also, along a reach just 

 inside the 1,800-foot jetties, small sailboats can range well outside the marked channel 

 boundaries into marginal waters. Of general interest, Newport Bay traffic counts made 

 during typical summer weekends show that an average of about 27 percent of the harbor's 

 oceangoing fleet uses the entrance on Saturdays and 32 percent on Sundays. 



Every entrance has its own special characteristics that may modify the tentative entrance 

 width determined by the above general rule. A short reach of constricted channel with more 

 area for maneuvering at either end can be considerably narrower than would be desirable for 

 a long channel of uniform width. Where boating characteristics of the harbor tenants spread 

 the daily entrance-use pattern uniformly over several hours rather than to concentrate in a 

 few peak hours, a narrower entrance may be acceptable. At times, the need to exclude as 

 much wave energy as possible from the harbor may override the congestion consideration; 

 then, an exceptionally narrow entrance must be provided and its use restricted in some 

 manner during peak hours. However, if the harbor berths a high percentage of sailboats and 

 requires a long entrance channel that for geographic reasons must be ahned parallel to the 

 prevailing wind direction, the channel may have to be even wider than the general rule 

 would indicate. 



One method of entrance-congestion analysis (Ely, 1972) considers the passage of boats 

 through entrances by assuming each boat to have a rectangular "blockading area" larger 



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