h9 



PART V: CONCLUSIONS 



Effects of Barriers on Tides 



72. Model test data presented herein are considered to be quan- 

 titative with respect to the effects of barriers on astronomical tide 

 ranges, elevations, and times, and also with respect to the effects of 

 harriers on the gravitational component of hurricane tides. To obtain 

 information on the absolute elevations that would be attained by hurri- 

 cane tides at various locations throughout the bay for conditions of the 

 barrier plans tested in the model, the effects of the local winds of the 

 hurricane in question must be applied to the model test data. As pointed 

 out above, all local wind-setup effects have been excluded from the model 

 tests on the basis of computations of this phenomenon by the New England 

 Division. Therefore, conclusions as to the absolute extent of the pro- 

 tection afforded by the barrier arrangements investigated will require 

 consideration of local wind-setup effects which are beyond the scope of 

 this report. 



Effects of Barrier Locations on Buildup 



73' The model tests indicated that barriers located in the central 

 region of the bay (Middle Bay barrier plans) would cause an appreciable 

 buildup in hurricane tide elevations downstream from the barriers. The 

 tests showed that no appreciable buildup would occur do\mstream from 

 barriers located near the upper extremity of the bay (Fields Point and 

 Fox Point barriers) nor downstream from those located near the bay en- 

 trances (Lower Bay barrier plans). The effects of barrier location on 

 buildup are illustrated on fig. 23, which shows the buildup in feet over 

 maximimi base test elevations that occurred immediately downstream from 

 each of the proposed barriers for conditions of the 1938 hurricane tide 

 (the negative buildup shown at the Field Point barriers was caused by 

 cutting off the upland discharge, as explained in paragraph 5^)« 



7^. The degree of gravitational buildup or attenuation of an 



