b. Lower Bay barriers . Barriers were tested for openings 

 ranging from 1,550 feet x 50 feet in the East Passage, 720 feet x 

 UO feet in the West Passage, and 1,000 feet x 50 feet in the East 

 Passage with gated openings in the West and Tiverton barriers. 

 All dimensions are referred to mean low water datvim, with ungated 

 openings having 1 on 1^ side slopes and gated openings having 

 vertical sides. With minimum openings, the September 1938 flood 

 indicated a rise of about one foot above predicted high tide at 

 Providence. 



Allowing for wind effect, water levels at Providence would be 

 about 6.5 feet above mean sea level. 



c. Fields Point barrier . Barriers with a gated navigation 

 opening were tested. A build-up of 0.5 foot (including 0,2 foot 

 from wind effect) is indicated south of the barrier for the design 

 tidal flood. Levels above the barrier would depend on pun5)ing 



of river flo\j from a 620-square-raile drainage area. 



d. Fox Point barrier . The model studies indicated a 

 relatively small build-up in flood levels south of the barrier. 



B-2I4. ANALYTICAL ROUTINGS 



In advance of hydraulic model studies analytical routing 

 calculations were made for numerous barriers in the bay with varia- 

 tions in dimensions of navigation opaiings. These data supplemented 

 studies at the Waterways Experiment Station, Calculations of velo- 

 cities and water surface elevations were based on the routings 

 predicated on storage in the 120-square-mile water area above the 

 barriers and the formula: 



C ■ coefficient of discharge, varying between 

 .6I4 and 0.80 



A « average cross-sectional area of opening 



g ■ acceleration of gravity, 32.2 feet per se'*''od 

 per second 



h » difference in water surface elevation between 

 ocean and bay 



A coefficient of 0,6ii was generally used for C and checked quite 

 closely with the model results for current velocities through 

 openings and effect on tidal fluctuations as to elevations and timing. 



B-2U 



