Narragansett Bay

Narragansett Bay is a bay and estuary on the north side of Rhode Island Sound covering 147 mi2 (380 km2), 120.5 mi2 (312 km2) in Rhode Island.[1] The Bay forms New England's largest estuary, which functions as an expansive natural harbor and includes a small archipelago.[2] Small parts of it extend into Massachusetts.

There are more than 30 islands in the Bay; the three largest ones are Aquidneck Island, Conanicut Island, and Prudence Island.[3] Bodies of water that are part of Narragansett Bay include the Sakonnet River, Mount Hope Bay, and the southern, tidal part of the Taunton River. The bay opens on Rhode Island Sound and the Atlantic Ocean; Block Island lies less than 20 miles (32 km) southwest of its opening. Narragansett Bay can be seen on NOAA Chart 13221.[4]

Coordinates: 41°36′N 71°21′W / 41.600°N 71.350°W

Narragansett Bay, boxed in red, in relation to Rhode Island


"Narragansett" is derived from the southern New England Algonquian word Naiaganset "(people) of the small point of land".[5]


Providence, at the head of the Narragansett Bay
Fall River skyline 2a
Fall River, at the northeast part of the Bay

Narragansett Bay comprises an area of about 147 miles (237 km). The watershed has seven river sub-drainage basins, including the Taunton, Pawtuxet, and Blackstone Rivers, and they provide freshwater input at approximately 2.1 billion gallons per day.[6] River water inflow has a seasonal variability, with the highest flow in the spring and the minimum flow in early fall.[7]

The bay is a ria estuary (a drowned river valley) which is composed of the Sakonnet River valley, the East Passage river valley, and the West Passage river valley. The bathymetry varies greatly among the three passages, with the average depths of the East, West, and Sakonnet River passages being 121 feet (37 m), 33 feet (10 m), and 25 feet (7.6 m) respectively.[8] Narragansett Bay is a ria that consists of a series of flooded river valleys formed of dropped crustal blocks in a horst and graben system[9] that is slowly subsiding between a shifting fault system.[10]

Providence is Rhode Island's capital and largest city and sits at the northernmost arm of the bay. Many of Providence's suburbs are also on the bay, including Warwick and Cranston. Newport is located at the south end of Aquidneck Island on the ocean, and is the home of the United States Naval War College, the Naval Undersea Warfare Center, and a major United States Navy training center. The city of Fall River, Massachusetts is located at the confluence of the Taunton River and Mount Hope Bay, which form the northeasternmost part of Narragansett Bay. The southwest side of the bay includes the seaside tourist towns of Narragansett and Wickford. Quonset Point, south of Warwick, gives its name to the Quonset hut. Roger Williams University is located in Bristol, Rhode Island overlooking the Bay.


Tidal patterns

Tides in the watershed are measured at six stations: Providence, Fall River, Quonset Point, Conimicut Light, Prudence Island, and Newport. In shallow water, sound waves are used to measure water height by precisely measuring the travel time of the waves. In deeper water, tides are measured with pressure-sensing tide gauges that are placed on the ocean floor to measure water height.

Rose island allegedly attributes its name to its rose shape at low tide.

The bay's tides are semi-diurnal, meaning that the region experiences two high and low tides daily. The tides range in height from 3.6 feet (1.1 m) at the bay's mouth, and 4.6 feet (1.4 m) at its head. The difference in water depth between high and low tide averages to about 4 feet (1.2 m). The lunar, semi-diurnal M2 tide occurs at a period of 12.42 hours, with two tides occurring in the watershed every 24 hours and 50 minutes. The watershed's neap and spring tides occur every 14.8 days. In Narragansett bay, the tides show a distinct double-peak flood during high tide and single peak ebb during low tide.[11]

Water circulation patterns

The movement of water within a system is its circulation. Estuaries are given a classification depending on the pattern of their circulations. The circulation classification can be well-mixed, partially mixed, salt wedge, or Fjord-type. For Narragansett, the circulation is mostly well-mixed; however, the Providence River does show some vertical stratification.

Narragansett Bay circulation is made up of forces provided by the winds, tides, and changes in water density within the watershed. Its circulation is the result of the flow of fresh water at the head interacting with salt water at the point where the bay meets the open ocean. Residence time of water due to the circulation of Narragansett Bay is 10–40 days, with an average of 26 days.[8] Tidal mixing is the dominant driver of circulation patterns in the bay, where currents can reach up to 2.5 feet per second. Non-tidal currents such as the flow of low salinity water at the surface out of the bay and high salinity deep water into the bay contribute to a current of about 0.33 feet per second.[8]

Winds also drive circulation patterns in the bay. In the winter, winds come from the northwest, helping move water towards the bay's mouth; in the summer, they are out of the southwest and move water towards the head of the bay. Wind-driven waves of over 4.25 feet (1.30 m) also help mix surface waters.

Density-driven forces are the third factor affecting circulation. Fresh water inflow comes from natural sources such as atmospheric precipitation and inflow from the many rivers that feed into the watershed, and man-made sources such as water treatment plants. Fresh and saltwater mixing results in a salinity range in the bay of 24 ppt in the upper Providence River area to 32 ppt at the mouth of the bay.

The bay's currents and circulation patterns greatly influence the sediment deposits within the region. The majority of the sediments within the bay are fine-grained material such as detritus, clay-silt, and sand-silt-clay. Scientists have been able to identify 11 types of sediment that range from course gravels to fine silts.[8] The bay's currents deposit fine materials through the harbors of the lower and middle sections of the bay, and the coarse, heavy materials are deposited in the lower areas of the bay where the water velocities are higher.

Early history

The Charles Blaskowitz Chart of Narragansett Bay published July 22, 1777 at Charing Cross, London

The first visit by Europeans to the bay was probably in the early 16th century. At the time, the area surrounding the bay was inhabited by two different Indian tribes: the Narragansetts occupied the west side of the bay, and the Wampanoags lived on the east side, occupying the land east to Cape Cod.

It is accepted by most historians that first contact by Europeans was made by Giovanni da Verrazzano, an Italian explorer who entered the bay in his ship La Dauphine in 1524 after visiting New York Bay. Verrazzano called the bay Refugio, the "Refuge". It has several entrances, however, and historians can only speculate as to the exact route of his voyage and the location where he laid anchor, along with a corresponding uncertainty over which tribe made contact with him.[12][13] Verrazzano reported that he found clearings and open forests suitable for travel "even by a large army".[14] Dutch navigator Adriaen Block explored and mapped the bay in 1614, and nearby Block Island is named in his honor.

The first permanent Colonial settlement was established in 1636 by Roger Williams, a former member of the Massachusetts Bay Colony. He was friends with Narragansett sachem Canonicus, who provided him with land on which to build Providence Plantations. Around the same time, the Dutch established a trading post approximately 12 miles (20 km) to the southwest which was under the authority of New Amsterdam in New York Bay. In 1643, Williams traveled to England and was granted a charter for the Colony of Rhode Island and Providence Plantations. He also wrote a dictionary of the Narragansett language which was published in England that same year.

The Gaspee Affair was an important naval event which moved the thirteen colonies toward the American Revolution. It occurred in Narragansett Bay in 1772 and involved the capture and burning of the British customs schooner Gaspee. The American victory contributed to the eventual start of the war at the Battles of Lexington and Concord in Massachusetts three years later. The event is celebrated in Pawtuxet Village as the Gaspee Days Celebration[15] in June which includes burning the ship in effigy.

Roger Williams and other early colonists named the islands[16] Prudence, Patience, Hope, Despair, and Hog. To remember the names, colonial school children often recited the poem: "Patience, Prudence, Hope, and Despair. And the little Hog over there."[17]

Water properties and phytoplankton distribution

Narragansett Bay is divided into two passages by Conanicut Island, east and west. Its average depth is 30 feet (9.1 m).[18] Surface temperatures vary seasonally from about 30° to 70°.[19] Surface salinity remains between 24.5 ppt and 31 ppt.[20] There is relatively high salinity water coming from the sea at the bottom and there is a seaward movement of fresher water in the surface.[19]


The Sakonnet River, a saltwater strait that forms part of Narragansett Bay
Providence from the Providence River at the head of Narragansett Bay


  1. ^ 1998 Journal-Bulletin Rhode Island Almanac, 112th Annual Edition, p. 36.
  2. ^ Keller, Aimee A.; Klein-MacPhee, Grace; Burns, Jeanne St. Onge (1 January 1999). "Abundance and Distribution of Ichthyoplankton in Narragansett Bay, Rhode Island, 1989–1990". Estuaries. 22 (1): 149–163. doi:10.2307/1352935. JSTOR 1352935.
  3. ^ "The Islands – City of Providence Website". Archived from the original on 2010-04-10. Retrieved 2010-04-03.
  4. ^ "Chart 13221" (61st ed.). Office of Coast Survey. June 2, 2017 [June 2016]. Archived from the original on June 25, 2017. Retrieved June 15, 2017.
  5. ^ Harper, Douglas. "Narragansett". Online Etymology Dictionary. Archived from the original on January 20, 2010. Retrieved June 15, 2017.
  6. ^ "Facts and Figures About Narragansett Bay - Save The Bay". Archived from the original on 9 October 2017. Retrieved 6 May 2018.
  7. ^ Spaulding, Malcolm L.; Swanson, Craig (1 January 2008). "Circulation and Transport Dynamics in Narragansett Bay". In Desbonnet, Alan; Costa-Pierce, Barry A. Science for Ecosystem-based Management. Springer Series on Environmental Management. Springer New York. pp. 233–279. doi:10.1007/978-0-387-35299-2_8#page-1 (inactive 2019-01-03). ISBN 9780387352985 9780387352992 Check |isbn= value: length (help) – via
  8. ^ a b c d "Ecological Geography of Narragansett Bay" (PDF). Archived from the original (PDF) on 6 September 2012. Retrieved 6 May 2018.
  9. ^ Robert L. McMaster, Jelle de Boer, and Barclay P. Collins, "Tectonic development of southern Narragansett Bay and offshore Rhode Island", Geology 8.10 (October 1980:496–500) (On-line abstract).
  10. ^ The faults produce earthquakes upon occasion, according to the USGS: "Rhode Island Earthquake History" Archived 2009-08-25 at the Wayback Machine..
  11. ^ "Physical Properties: Circulation: Tides, from Discovery of Estuarine Environments (DOEE)". Archived from the original on 2014-01-29.
  12. ^ "Archived copy". Archived from the original on 2003-01-23. Retrieved 2004-01-21.CS1 maint: Archived copy as title (link)
  13. ^ "Archived copy". Archived from the original on 2003-11-13. Retrieved 2004-01-21.CS1 maint: Archived copy as title (link)
  14. ^ W. Conon, Changes in the Land: Indians, Colonists and the Ecology of New England (New York) 1983.
  15. ^ DRC. "Gaspee Days Committee". Archived from the original on 2010-02-03. Retrieved 2010-04-03.
  16. ^ "Roger Williams Biography".
  17. ^ "Prudence Island Lighthouse History". Retrieved 2010-04-03.
  18. ^ Borkman DG and T Smayda (2009) Multidecadal (1959–1997) changes in Skeletonema abundance and seasonal bloom patterns in Narragansett Bay, Rhode Island, USA. J Sea Res 61(1–2): 84–94{[1]}.
  19. ^ a b HICKS,S.D.1953. Temperature and salinity.In: Inshore Survey Project Final Harbor Report, Narragansett Bay and its approaches, Physical Oceanography. Narragansett Marine Laboratory Ref. 53-12(mimeographed). 1959. The physical oceanography of Narragansett Bay. Limnol. Oceanogr., 4(3):316–327 ([2]).
  20. ^ Hulsizer, E.E. 1976. Zooplankton of lower Narragansett Bay, 1972–1974. Chesapeake Sci. 17(4): 260–270.url= .

External links

Aquidneck Island

Aquidneck Island, officially Rhode Island, is an island in Narragansett Bay and in the State of Rhode Island and Providence Plantations, which is partially named after the island. The total land area is 97.9 km2 (37.8 sq mi), which makes it the largest island in the bay. The 2000 United States Census reported its population as 60,870.

Aquidneck Island is home to three towns, from north to south: Portsmouth, Middletown, and Newport.

Barrington River (Rhode Island)

The Barrington River is a tidal extension of Runnins River in the U.S. states of Rhode Island and Massachusetts. It flows approximately 6 km (4 mi). There are no dams along the river's length.

Conanicut Island

Conanicut Island is the second largest island in Narragansett Bay in the US state of Rhode Island. It is connected on the east by the Claiborne Pell Bridge to Newport on Aquidneck Island, and on the west by the Jamestown-Verrazano Bridge to North Kingstown on the mainland. The island comprises the town of Jamestown, Rhode Island. The United States Census Bureau reported a land area of 24.46 km2 (9.44 sq mi) and a population of 5,622 as of the 2000 census.

Cornelius Island

Cornelius Island is a small uninhabited island in Wickford Harbor, Narragansett Bay, Wickford, Rhode Island.

Dyer Island (Rhode Island)

Dyer Island is an island in Narragansett Bay in Rhode Island, United States. It lies off the west coast of Aquidneck Island and is part of Melville CDP, which itself is part of the town of Portsmouth. The island lies between Melville and Prudence Island and is uninhabited and has a land area of 0.12 km² (29.65 acres) and is only 13 feet above sea level.

The salt marshes of Dyer Island are among the last remaining in Rhode Island without mosquito ditches, and the island is home to various shorebirds.

In the seventeenth century, Dyer Island was named after William Dyer, the husband of the Quaker martyr Mary Dyer. William Dyer was one of the founders of Rhode Island, and in 1638 he sailed past the island and requested that it be granted to him, which was done according to Roger Williams and other affiants. William Dyer died in 1676 in Newport, Rhode Island. He is buried in the family cemetery which was located on the family farm in Newport not on Dyers Island in Narragansett Bay. Upon his death the island comprising some 29 acres (0.12 km2); was given to his son William.In 2001 the Island was purchased by the state of Rhode Island and is now part of the Narragansett Bay National Estuarine Research Reserve, as well as JDSinc.

Hope Island (Rhode Island)

Hope Island is a 91-acre (0.368 km²) island located in Narragansett Bay in the State of Rhode Island. It is part of the Narragansett Bay National Estuarine Research Reserve, along with nearby Prudence Island and Patience Island, and home to colonial wading birds during their nesting season of spring and summer.

Jamestown, Rhode Island

Jamestown is a town in Newport County, Rhode Island in the United States. The population was 5,405 at the 2010 census. Jamestown is situated almost entirely on Conanicut Island, the second largest island in Narragansett Bay. It also includes the uninhabited Dutch Island and Gould Island. Jamestown is ranked as the 444th wealthiest place to live in the United States as of 2016, with a median home sale price of $1,229,039.

Lime Rock (island)

Lime Rock is an island 600 feet offshore in Newport Harbor, in Narragansett Bay, in the U.S. state of Rhode Island. It was made famous by Ida Lewis, who was the lighthouse keeper of the tower built on it in 1854 which is now known as Ida Lewis Rock Light. In 1927 the island was sold to a Yacht Club and was connected to Aquidneck Island by a small causeway. A steel tower light was placed in front of the building, which remained an active light until 1963.

List of rivers of Rhode Island

This is a list of rivers in the U.S. state of Rhode Island. Rivers in bold are considered major rivers either geographically or historically.

Little Narragansett Bay

Little Narragansett Bay is an inlet of the Atlantic Ocean and an estuary of the Pawcatuck River on the Rhode Island-Connecticut state line. It is sheltered by a curving peninsula, known as Napatree Point.

At the base of Napatree Point is the site of the resort village of Watch Hill, Rhode Island. The bay also contains the islands of Sandy Point, Elihu Island, and Barn Island. Sandy Point was once part of Napatree Point until the two were separated by the Hurricane of 1938. Since that time it has migrated north and west, and changed orientation. It now begins about 1/4 mile east of Stonington Borough, and runs approximately 1 1/2 miles east-southeast.

Narragansett, Rhode Island

Narragansett is a town in Washington County, Rhode Island, United States. The population was 15,868 at the 2010 census. However, during the summer months the town's population more than doubles to near 34,000. The town is colloquially known as "Gansett". The town of Narragansett occupies a narrow strip of land running along the eastern bank of the Pettaquamscutt River to the shore of Narragansett Bay. It was separated from South Kingstown in 1888, and incorporated as a town in 1901.

For geographic and demographic information on the village of Narragansett Pier, which is part of Narragansett, see the article Narragansett Pier.

Narragansett Bay National Estuarine Research Reserve

The Narragansett Bay National Estuarine Research Reserve is a Marine Protected Area of the United States located on Prudence, Patience, and Hope islands in Narragansett Bay in the state of Rhode Island.

It was established in August 1980 under the Coastal Zone Management Act.

The reserve encompasses 2,353 acres (9.5 km²) of land as well as 1,591 acres (6.4 km²) of water adjoining the islands out to a depth of 18 feet (5.5 m). During the colonial era, all three islands were used for farming. By the 20th century, farming had declined and Prudence Island began to attract summer residents. During World War II, the U.S. military established a presence on the island and remained until 1972, when the land was turned over to the state of Rhode Island.

It encompasses coastal, estuarine, and tidal habitats.

The reserve is managed by the Rhode Island Department of Environmental Management as a federal/state partnership in cooperation with NOAA.

Patience Island

Patience Island lies off the northwest coast of Prudence Island in the town of Portsmouth, Rhode Island. It has a land area of 0.33 sq mi (0.85 km2; 210 acres), making it the fourth-largest island in Narragansett Bay.

Point Judith, Rhode Island

Point Judith is a village and a small cape, on the coast of Narragansett, Rhode Island, on the western side of Narragansett Bay where it opens out onto Rhode Island Sound.

It is the location for the year-round ferry service that connects Block Island to the mainland and contains the fishing hamlet of Galilee, Rhode Island.

Providence River

The Providence River is a tidal river in the U.S. state of Rhode Island. It flows approximately 8 miles (13 km). There are no dams along the river's length, although the Fox Point Hurricane Barrier is located south of downtown to protect the city of Providence from damaging tidal floods.

The southern part of the river has been dredged at a cost of $65 million in federal and state funds to benefit nearby marinas and commercial shipping interests.The Dutch called the Providence River the Nassau River. It was the northeastern limit of Dutch claims in the colonial era, owing to Adriaen Block's exploration of Narragansett Bay, from 1614 until the Hartford Treaty of 1650. It can, therefore, be regarded as the original boundary between the English New England colonies and the Dutch colony of New Netherland.

Prudence Island

Prudence Island is the third-largest island in Narragansett Bay in the state of Rhode Island and part of the town of Portsmouth, Rhode Island. It is located near the geographical center of the bay. It is defined by the United States Census Bureau as Block Group 3, Census Tract 401.03 of Newport County, Rhode Island. As of the 2000 census, the population was 88 people living on a land area of 14.43 km² (5.57 sq mi).

Rabbit Island (Rhode Island)

Rabbitt Island is a small island in Wickford Harbor, Narragansett Bay, Wickford, Rhode Island. Roger Williams received the island from Chief Canonicus' wife as a gift for a place to raise his goats. Richard Smith, who built Smith's Castle, later owned the island.

Rose Island (Rhode Island)

Rose Island is an 18.5-acre (7.5 ha) island in Narragansett Bay off Newport, Rhode Island, United States. It is allegedly named "Rose Island" because at low tide the island appears to be shaped like a rose. The Island is only accessible by boat. The island and its lighthouse are run by the private, non-profit Rose Island Lighthouse Foundation.

Runnins River

The Runnins River is a river in the U.S. states of Massachusetts and Rhode Island. It flows approximately 14 km (9 mi).

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