to short-period, distant storm waves from the deepwater directions clock- 

 wise between west and northwest, and local storm waves from the north 

 (Fig. 6-23) . The magnitude of these waves is sometimes sufficient to 

 damage fishing boats and harbor facilities, causing mooring difficulties 

 for small craft in exposed areas of the harbor. It was proposed to en- 

 large the existing harbor by constructing one or more additional break- 

 waters to provide safe anchorage within the harbor. The problem of 

 concern in this study was the design of a tribar cover layer for a part 

 of the proposed north breakwater. It had been considered that a concrete 

 cap on the crown of a breakwater was needed if molded concrete armor units 

 were to be used for structures where overtopping was expected. However, 

 tests conducted in 1966 in connection with a proposed rubble-mound break- 

 water at Nassau Harbor, Bahamas (Hudson and Jackson, 1966), indicated that 

 tribar armor units do not necessarily require a concrete cap to ensure 

 that the overtopping waves do not damage the breakwater crown. There- 

 fore, a model study was considered necessary to check the stability of 

 the proposed Monterey Harbor breakwater since the crest elevation, inten- 

 sity of wave action, and the size of the armor units at Monterey Harbor 

 were not the same as those at Nassau Harbor. 



6^ Purpose of Model Study . This investigation was con- 

 ducted to determine the stability of the proposed cover layer and heights 

 of waves transmitted through and over the east end of the proposed north 

 breakwater at Monterey Harbor (Fig. 6-24) . It was desired to determine 

 the stability of the structure using the selected design wave in the 

 prototype studies (15-second wave, 18 feet in height), and the heights 

 of transmitted waves for the design wave conditions and for 17-second 

 waves up to 16 feet in height. 



1_ The Model . Stability and wave transmission tests 

 were conducted on a l:40-scale model of the proposed prototype section 

 in a flume 119 feet long, 5 feet wide, and 4 feet deep. The model was 

 designed and operated by Froude's law, and the linear scale was selected 

 on the basis of the size of armor units available compared with those 

 proposed for the prototype section (12 tons), the water depth in which 

 the prototype structure would be placed (36 feet MLLW) , and the capability 

 of the wave generator. The Stillwater level used for testing (MHHW) , , 

 which is +5.2 feet MLLW, was selected as being representative of condi- 

 tions normally expected to occur during severe storms. Both the damage 

 to the crest of a structure of the type being tested, and the heights of 

 waves generated on the harborside of the structure due to wave trans- 

 mission and overtopping, are larger for the higher Stillwater levels. 

 The maximum waves that can attack such a structure also increase as the 

 water depth increases. A plunger- type wave generator was used and wave 

 heights were measured using electrical wave gages and a recording 

 oscillograph. 



8^ Test Procedures . The test section (Fig. 6-25) was 

 subjected to waves, measured without the structure in place, of 15-second 

 period ranging in height from 2 to 21 feet and 17-second waves ranging 

 from 2 to 18 feet in height. During construction of the test section, 



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