lj-2 



were then established in the flimie containing the undistorted scale 

 models of the openings for detailed measurements of current velocity 

 distribution in the openings for these conditions. 



63. The effects of plan 35 on astronomical tide ranges and eleva- 

 tions for the two conditions tested are shown separately in table k. 

 The effects of this plan on hurricane tide elevations are shown in that 

 part of table h which presents astronomical spring tide data, since the 

 hurricane tide tests were run in combination with that tide. The effects 

 of the plan on times of high tide for conditions of both astronomical and 

 hurricane tides are shown in table 3- Spring astronomical tide ranges 

 at gages located upstream from the Lower Bay barriers were reduced by 

 an average of about kO per cent, while mean-tide ranges were reduced by 

 an average of about 37 pe^r cent. The maximum elevations of hurricane 

 tides at Providence were reduced from +I5.I ft mlw to +6.7 ft for condi- 

 tions of the 1938 hurricane tide and from +17.2 ft to +8.0 ft for condi- 

 tions of the 20-knot design h\arricane tide. 



6k. The effects of plan 35 on tidal current velocities throughout 

 the bay are shown in table 5» Base test current velocities in this 

 table were obtained for conditions of the normal spring tide and no 

 barriers, while plan test data were obtained for conditions of the same 

 tide with plan 35 installed in the model. The velocity measurements 

 presented in table 5 indicate that both flood and ebb current velocities 

 at stations located upstream from the Lower Bay barriers were reduced, 

 the maximum velocities being reduced by amounts ranging from about 20 

 per cent to about 60 per cent. 



65. Current velocities were measured in the East and West Passage 

 navigation openings of plan 35 for conditions of both spring and mean 

 astronomical tides. Measurements were made at the surface, one-quarter 

 depth, and one -half depth on the center lines of the openings and the 

 centers of the sills. Two additional verticals, located halfway be- 

 tween the center lines and the abutments and also on the centers of the 

 sills were used in the East Passage opening. Velocities observed at the 

 three depths on the center lines of the openings for each hour of a com- 

 plete tidal cycle are presented in table 6. The additional velocities 



