sun and the noon. On the North Atlantic coast, it is generally 

 assumed that a drop in barometric pressure of one inch (of Kercury) 

 will cause about a one-foot rise in water level. Normal winds 

 within the bay hare little effect on the tide levels, but do have 

 noticeable influence on tilling. However, during a strong coastal 

 storm, such as a northeaster, tide levels often build up one to 

 two feet above the predicted elevations, When a severe storm 

 occurs over Narragansett Bay, with coincident low pressure and 

 strong southerly winds, the observed tide far exceeds predicted 

 elevations. Tidal data are given for iS locations in the Narra- 

 gansett Bay area in the yearly tide table publication of the U,S, 

 Departnent of Commerce, Coast and Geodetic Survey entitled "TTide 

 Tables, East Coast, North and South America," 



TABLE B-1 



ASTRONCMICAL TIDES 



NARRAGANSETT BAT 



Mean Range (ft.) 

 Mean Low Water (below m,8,l.) 

 Mean High Water (above m.s.l.) 

 Average Spring Tide Range (ft,) 

 Maxljnum Spring Tide (above m,s.l«) 

 Minimum Low Water (below m.s.l.) 



B-U. CmiRENTS 



Normal tidal curi?ent velocities over the greater part of Naira- 

 gensett Bay vary from zero, at slack water, to about 1,5 knots. 

 Velocities between 1 and 1,5 knots occur at the bridges in the See- 

 konk River, and velocities of more than 2,8 knots are experienced 

 at the highway bridge across the Sakonnet River. Current veloci- 

 ties during spring tide will often exceed the normal velocities 

 by 20 percent. Currents close to the surface, however, show a 

 wide variation when influenced by strong winds. For example, high 

 winds frcBi the northwest will reverse the direction of the flood 

 tide on the surface to produce a southerly current, while flood 

 currents below the surface have a strength of 0.5 knot toward the 

 north. Current charts for the Narragansett Bay are published 

 in Special Publication No, 208 of the Coast and Geodetic Survey 

 entitled, "Currents in Narragansett Bay, Buzzards Bay, and Nan- 

 tucket and Vineyard Sounds," Current observations in Nanragansett 

 Bay are contained in a report of the Narragansett Marine Laboratory 

 of the University of Rhode Island, 



B-2 



