Base movable-bed tests were started with known model-bed configurations, 

 the model tide and wave generators were operated through a predetermined 

 schedule, and the model bed was surveyed periodically to record develop- 

 ments during the test. The movable-bed test for any plan was an exact 

 duplicate of the base test except that the alternative plan was installed 

 at the beginning of the test. The effects of the plan were determined by 

 comparing the configuration of the model bed at the end of the plan test 

 with the configuration of the model bed at the end of the base test. 



(9) Summary of Test Results . The verification period selected 

 for the Fire Island Inlet model was the 2 years immediately after con- 

 struction of the navigation channel in November 1964. A careful study 

 determined the following significant changes in prototype bed configura- 

 tions that occurred during this period: (a) A scour area developed just 

 north of the inner part of the navigation channel, (b) a shoal about 6 to 

 12 feet high developed in the inner part of the inlet channel, and (c) a 

 shoal about 6 to 12 feet high developed along the eastern edge of the 

 outer part of the navigation channel. After operating the model for 72 

 tidal cycles, it was found that the gross changes in bed configuration 

 in the model were very similar to those indicated by comparison of the 

 prototype surveys made 2 years apart. The bed movement during verifi- 

 cation of a movable-bed model is not expected to duplicate exactly all 

 changes in prototype bed configurations during the selected verification 

 period because (a) the trends in bed movement in the prototype are not 

 constant with time, although the model verification procedure constitutes 

 an attempt to reproduce such movement on an average basis, and (b) certain 

 observed changes in prototype bed configurations are mostly the result of 

 storms or other extreme conditions, which the model verification (neces- 

 sarily based on average conditions) cannot be expected to reproduce. In- 

 stead, the model-bed movement verification is an attempt to reproduce the 

 gross changes that occurred in the prototype between the beginning and 

 end of the verification period, and minor discrepancies of a local nature 

 (or which are attributable to unusual prototype conditions) may be neg- 

 lected. The deviations of the Fire Island Inlet model from the proto- 

 type conditions during a 2-year period are shown in Figure 7-12. 



Conclusions based on the results of hydraulic and movable-bed model 

 tests concerning proposed improvement plans for Fire Island Inlet were: 



(a) Plan 3A, which required a littoral reservoir dredged to 

 -34.0 feet, a deposition or rehandling basin to -28.0 feet when 

 filled, and a 28-foot-deep connecting channel, will result in a 

 safe and stabilized navigation channel with enough sand for by- 

 passing to the downdrift beaches. Maintenance dredging of the 

 littoral trap and connecting channel will be required about every 

 2 years; most of this dredging can be accomplished with conven- 

 tional dredging plants. Since deposition in the littoral trap 

 and connecting channel occurs in the form of a high bar, which 

 builds from east to west, a sidecast dredge or similar equipment 

 will probably be required to lower the bar crest enough for a 

 hopper dredge to restore the basin depths. 



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