32 



hk. Prior to the above-described model tests, the Middle Bay 

 barrier site had been generally considered to be the optimum location 

 for barriers in Narragansett Bay for the following reasons: (a) the 

 Middle Bay site would afford protection to those portions of the bay 

 system which had experienced the greatest loss of life and property dur- 

 ing hurricane tides of record; and (b) provisions for navigation through 

 the structures by large naval vessels would not be involved, since the 

 major naval bases in the bay are located downstream from the Middle Bay 

 barriers. Because of the buildup downstream from the structures in- 

 dicated by the model tests, which amounted to as much as 2.0 ft for tests 

 involving the 1938 hurricane tide, the Middle Bay barriers were excluded 

 from further consideration and were not subjected to as detailed testing 

 as were some of the barrier plans tested subsequently. For example, the 

 Middle Bay barrier tests reported herein were made prior to and were not 

 tested with the refined model roughness adjustment described in para- 

 graph 29 of this report, nor were these barrier plans subjected to hur- 

 ricane tide tests for conditions of any of the design hurricane tides. 

 The deficiency in model roughness existing at the time of the Middle Bay 

 barrier tests probably resulted in slightly higher hurricane tides through- 

 out the bay system than would have occurred had the roughness been correct 

 (the addition of roughness lowered the I938 hurricane tide peak at 

 Providence by about O.5 ft). However, since the roughness deficiency 

 would have affected hurricane tide elevations in the same degree for both 

 base test and plan test conditions, it was concluded that the buildup 

 downstream from the model structures indicated by the model tests was of 

 the proper order of m-agnitude, and the Middle Bay barrier tests were not 

 repeated. 



Lower Bay Barriers 



U5. The locations of the various elements of the Lower Bay barrier 

 plan are shown on fig. 15 . The general features of the plan included 

 closure of the West Passage just downstream from the Jamestown Bridge 

 (West Lower Bay barrier), closure of East Passage at Bull Point (East 



