B-7* FLUSHING 



The flushing rate in Narragansett Bay, defined as the time 

 required for a particle in the vater to move from Proridence to 

 the mouth of the bay, varies during normal conditions from U2 

 to 59 days. It is described in detail in a report of the Narra- 

 gansett Marine Laboratory. A tabulation shoving a coiqparison of 

 the flusMng rates with and without the Lower Bay bairriers is 

 Included in paragraph B-33. 



B-8. SILTING 



Sedimentation studies were undertaken by the Nainragansett 

 Marine Laboratory in the spring and summer of 19^6 to detemdne 

 the general nature of the present bottom surface sediments in 

 Upper and Lower Narragansett Bay and in Mount Hope Bay. Of 

 sair^les of material taken in the Upper Bay and in Motmt Hope 

 Bay 80 to 95 percent was silt or clay. This is imdoubtedly due 

 to the deposition of large quantities of waste and sewage that 

 are carried down by the Providence and Taunton Rivers. The 

 results of the samples taken in the Lower Bay indicate, as may 

 be expected, that the percentage of coarser materials is 3 to 

 U times higher than the fine silt and clay. Maintenance of 

 dredged navigation channels in the Providence River indicates 

 about 0,1 foot per year of sedimentation. 



B-9. HECQEIDIHG TIDE GAGES IN NARRAGANSETT BAT 



Of the 15 locations in this area for which the U.S. Coast 

 and Geodetic Survey has published tidal data, two have permanent 

 recording gages. The information for the other localities was 

 established by making observations with temporary installations. 

 The principal recording tide gage, upon lAlch the tidal data 

 for the area are based, is the installation on Coasters Harbor 

 Island, Newport. This gage was established in September 1930, 

 and has been in operation since with the exception of brief 

 periods following the hurricanes of 1938 and 195U. The other 

 recording gage is located at State Pier No. 1 in Providence. 

 This was installed in June 1938, and was in operation imtll May 

 I9U7, except for several months after being damaged by the Sep- 

 tember 1938 hurricane. There has been no peraanent gage at this 

 point ftrcm May 19U7 until August 1956, when the location was 

 re-established. 



B-10. CORPS OF ENGINEERS' TIDE GAGE PROGRAM 



As part of its program of establishing recording and non- 

 recording tide gages Eilong the New Ehgland coast, the New England 

 Division, Corps of Engineers, has installed 16 recording gages, 



B-5 



