and stabilization of the jetty channel designed to accommodate super- 

 tankers, and diversion of currents causing the undermining of the north 

 jetty. For all plans tested, the entrance channel was maintained at the 

 authorized project dimensions (800 feet wide and 42 feet deep for the 

 inner bar channel, and 44 feet deep for the outer bar channel). The 

 fixed procedures developed in the verification phase of the study were 

 followed in the operation of all tests. The only variations between 

 the various tests were in the features of the plans of improvement. 



Before the beginning of each test, the movable bed of the model was 

 molded to conform to the prototype survey of 1960, and the selected plan 

 of improvement was installed in the model. The navigation channel was 

 dredged to project dimensions along the proposed realinement, and the 

 channel was maintained by annual dredging throughout the duration of the 

 test. Each of the channel realinement tests consisted of the simulation 

 of at least 12 prototype years in the model, 8 years of normal conditions, 

 and 4 years after a simulated storm condition. Detailed studies of the 

 paths of moving bed material were made during the various tests. The 

 model bed was surveyed and mapped at the end of each simulated year of 

 each test to determine the progressive changes in bed conditions, as 

 well as the final results of each test. Analyses and interpretations 

 of the results of the model tests were based on careful observations 

 during model operations and on survey studies of the model bed, in re- 

 lation to the qualifications and limitations of the model. 



(9) Summary of Test Results . Conclusions based on results of 

 the model tests were: 



(a) Entrance channel realinement plan 2 was superior to 

 the existing channel alinement because the plan provided a shorter and 

 straighter channel for navigation by supertankers, diverted the strong 

 ebb currents away from the north jetty and thus protected the jetty from 

 the undermining action of these currents, and provided a 4-foot-deeper 

 entrance channel for essentially the same maintenance dredging required 

 for the existing channel. 



(b) Construction of the plan 2 channel could be scheduled 

 over as long as 2 years without affecting overall shoaling in an 8-year 

 period. However, the shoaling rate during the first 2 years after com- 

 pletion of construction would probably be accelerated by normal adjust- 

 ment of channel side slopes. An important element of the construction 

 procedure is the disposal of dredged material in the abandoned part of 

 the existing channel to avoid enlarging the total cross-sectional area 

 between the jetties and thus reducing current strengths. 



(c) The outer 3,000 feet of the north jetty could be per- 

 mitted to degrade naturally to elevation -12.0 without detrimental effects 

 on shoaling in the realined channel. However, deterioration of appreciably 

 more than 3,000 feet of the north jetty would cause an undesirable change 

 in the overall flow patterns in the entrance, which in turn would cause 

 the inner shoal to again encroach on the inner bar channel. 



510 



