(b) Rubble Mound Stability. 



Large scale tests on stability of rubble mound structures under wave 

 action were continued to spotcheck the results of the small scale test 

 program at the Waterways Experiment Station. Calibration of the tank to 

 obtain a precise determination of the wave heights at the structure location 

 without the structure in place were completed for the waves tested on the 

 1 on 1-1/2 slope rubble breakwater, having cap protection of approximately 

 1-foot diameter, 160-pound stone. The results of these tests appear to 

 indicate that the effects of scale, at least insofar as stability is con- 

 cerned, are small and essentially indistinguishable from effects caused by 

 differences in stone shape, placement, and degree of interlocking. Tests 

 have been initiated using a 75-pound, 4-legged concrete shape (a quadripod) 

 as the cap protection. This shape is somewhat similar to a tetrapod with a 

 flat base. Tests to determine the no-damage (or incipient damage) condition 

 have been completed for several wave periods. Tests involving larger, 

 damaging waves will be carried out in the spring of 1963. 



(c) Wave Run-up. 



Some large scale run-up data involving waves up to 3.5 feet in height 

 were gathered on a 1 on 1-1/2 rubble (quadripod) breakwater in conjunction 

 with tests on rubble mound stability. Additional run-up data involving 

 waves up to about 6 feet in height were gathered on smooth sand beaches 

 having a 1 on 15 slope in conjunction with beach deformation tests in the 

 large wave tank. 



In addition to correction curves for scale effect in wave run-up 

 published in the revised edition of Beach Erosion Board Technical Report 

 No. 4, a generalized run-up curve embodying an average scale correction was 

 included in a report "Freeboard Allowances for Waves in Inland Reservoirs" 

 and published in the American Society of Civil Engineers Waterways and 

 Harbors Division Journal. 



(d) Study of Sand Bypassing Operations. 



Efforts were continued to collect all available data on sand bypassing 

 operations (past, present, or planned) for correlation and study. Analysis 

 of the hydrographic survey data obtained in the Port Hueneme area in June 

 1959 is essentially complete. Comparison of this data with previous survey 

 data taken since the bypass dredging operation in 1954-55 reveals that 

 accretion north of the jetties slowed after the filling of the dredged 

 pocket and that the downcoast (southern) beaches continued to erode at an 

 average rate of approximately 1,200,000 cubic yards per year. 



The field observation program was continued in the vicinity of Ventura 

 County Harbor, California, in which an offshore breakwater (parallel to the 

 shore) forms a protected area serving as a sand trap. Use of 3 wave gages 

 at this location, each with different degrees of sheltering, permits some 



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