50 



f 



Fig. 23- Effect of barrier location on buildup for conditions 



of 1938 hurricane tide 



astronomical or hurricane- generated tidal wave as it passes through a 

 bay or estuary is affected by the depths^ widths, shapes, and other 

 physical characteristics of the system of channels involved. The extent 

 of buildup of hurricane tides in Warragansett Bay for existing condi- 

 tions may be illustrated by the fact that the gravitational component 

 of the 1938 hurricane tide reached a maximum elevation at Providence 

 (head of the bay) some 3'1 to 3-3 ft higher than at Newport which is 

 near the bay entrance. This same phenomenon occurs for conditions of 

 astronomical tides, since the mean elevation of high tide at Providence 

 is about 0.5 ft higher than at We-i'Tport. 



75 • Construction of a barrier in the bay results in the loss of 

 all or part of the storage (tidal prism) upstream from the barrier site, 

 and the effects of this reduction in storage are reflected by increased 

 elevations doimstream from the barrier over those that would obtain with- 

 out the structure. The reduction in storage effected by the Upper Bay 

 barriers was so small in relation to the total volumes of hurricane tides 

 in the entire bay that no measurable buildup occurred downstream from 



