B-22, DESCRIPTION OF MODEL 



The model at the Vfeterways Experiment Station reproduces all 

 of Narragansett Bay and a portion of the Atlantic Ocean adjacent 

 to the bay entrance and consists of fixed-bed construction with 

 scale ratios, model to prototype, of 1:1000 horizontally and 

 1:100 vertically. Dimensions of the model are approximately 

 100 feet wide and 2^0 feet long, and cover about 1^,000 square 

 feet. An automatic tide^nerator is used to reproduce normal 

 tides throughout the model, and a separate automatic tide 

 generator is used to reproduce hurricane tides of the desired 

 characteristics at the bay entrance. Fresh water only was used 

 in the model during tests to determine the effectiveness of the 

 proposed barriers in reducing hurricane- tide damage. Appurtenances 

 that are used in the model consist of automatic and manually 

 operated tide gages to record hurricane- tide elevations at 

 critical points throughout the bay system. 



B-23. MODEL TESTING PROGRAM 



Following the construction of the model and tidal generators, 

 adjustments were made to reproduce normal tide conditions in 

 Narragansett Bay as well as the hurricane tides of September 21, 

 1938, September Ik, 19Uh, and August 31, 195U. The effect of 

 the various barrier plans on hurricane tide conditions in the bay 

 was then determined, using the September 1938 and the design 

 hurricane tidal floods. 



a. Middle Bay barriers . Barriers were tested with openings 

 ranging from 720 feet x UO feet in the East Passage, 1|00 feet 

 X 20 feet in the West Passage, and UOO feet x kO feet in the 

 East Passage with gated openings in the West and Tiverton 

 barriers. The latter test, for the 1938 hurricane conditions, gave 

 very effective protection with a rise of only one foot above 

 predicted high tide at Providence. Allowing 2 feet of wind 

 effect would result in a rise in elevation of about 6 feet at 

 Providence, idiich is below zero damage stage. At the same time, 

 however, the build-up south of the Middle Bay barriers was about 

 lo5 to 2.0 feet, diminishing to approximately 0.5 feet near 

 Newport. Thus tidal flooding would be increased in the area 

 below the barriers and the Middle Bay barriers were dropped 

 from further consideration. 



B-23 



