k 



is no appreciable lag between the time of high tide at the entrance and 

 at the head of the bay^ the average time of high tide at Providence being 

 only about 10 to 20 minutes later than at the entrance some 25 miles away. 

 Tidal current velocities throughout the bay system produced by astronom- 

 ical tides are q^uite moderate^ ranging from maximums of about 2.5 ft per 

 sec in the East and West Passages to less than 1.0 ft per sec in the wide 

 sections. Only in a few restricted sections^ such as that under the 

 bridge near Tiverton^ do current velocities of astronomical tides exceed 

 about 2.5 ft per sec. 



6. The tides generated by tropical hurricanes moving north along 

 the Atlantic Coast are sometimes much greater in magnitude in the 

 Narragansett Bay area than the largest astronomical tides ^ especially 

 when the hurricane center moves inland to the west of Narragansett Bay^ 

 thus placing the bay in the path of the right front q^uadrant of the 

 storm. When the time phasing of the hurricane-generated tide is such 

 that its peak coincides with high water of the astronomical tide, as was 

 the case in September I938 and August 195^^ the flooding of low- lying 

 areas is especially severe and loss of life and damage to property may 

 be extensive. 



7. The tides generated by hurricanes moving inland on a coast 

 such as that at the entrance to Narragansett Bay are made up of two major 

 components: (a) the general rise in sea level produced by the low-pressure 

 area associated with the hurricane center; and (b) the wind setup, or the 

 additional rise in sea level produced by the mass transport of water 

 shoreward by the onshore winds of the right front quadrant of the storm 

 blowing over the fetch between the Continental Shelf and the shore . The 

 height of the surge component generated by the wind is dependent on the 

 wind velocity, fetch, the direction of the storm path with respect to 



the alignment of the shore, the bottom slope of the offshore region, and 

 many other factors. 



8. After a hurricane- generated tide enters a bay or estuary such 

 as Narragansett Bay, the resultant heights attained at various locations 

 are dependent on two major factors: (a) the gravitational component of 

 the ocean tide which moves through the entrance and thence through the 



