Coastal Flooding
Tidal Flooding
King tide or high tide flooding occurs when the Sun, Earth, and Moon align to enhance the gravitational pull on the ocean. Low-lying locations along the coastline (i.e., beaches, docks, and roadways) are vulnerable to king tide flooding. If a king tide coincides with a storm system, the resulting flooding can be enhanced by storm surge and rainfall. King tides offer a glimpse of future tidal flooding as sea levels rise due to climate change.
Storm Surge
Storm surge occurs when a tropical storm, hurricane, or Nor’easter advances up the coast or makes landfall. Strong winds accumulate seawater at the center of the storm. When the storm nears land, the seawater is forced into low-lying coastal areas. The combination of storm surge and a high tide is called a storm tide. The Fox Point Hurricane Barrier was constructed to protect Providence from storm surge.
Sea Level Rise
As the atmosphere warms due to climate change, alpine glaciers and polar ice sheets around the world are melting at an unprecedented rate. Between 1900 and 2001, Greenland alone was estimated to have lost 587 cubic kilometers of ice, which is equivalent to enough meltwater to fill 235,000,000 Olympic-size swimming pools. Sea level rise is also caused by the thermal expansion of seawater. Earth’s oceans absorb 90% of heat generated by anthropogenic greenhouse gas emissions. Thus, the volume of the oceans are increasing since seawater occupies more space as it warms.
The tide gauges at Newport (established 1930) and Providence (established 1938) have documented sea level in Rhode Island. As of 2024, the sea level at Newport has risen 11.64” and the sea level at Providence has risen 10.32” since record keeping began. The extent of future global greenhouse gas emissions will dictate additional sea level rise in the state.
Newport Sea Level Trend
Providence Sea Level Trend
Newport Sea Level Projections
Providence Sea Level Projections
Significant Coastal Floods
Many coastal floods have occurred throughout Rhode Island’s history, and the following events are highlighted for their severity and impact along the state’s coastline. It is important to note the magnitude of coastal floods (i.e., storm tide, storm surge, etc.) were rarely quantified before the establishment of important infrastructure.
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August 1635 – The Great Colonial Hurricane of 1635
The first hurricane in recorded history to strike New England produced a storm surge of 14’-20’ in Narragansett Bay, per an account from Governor John Winthrop of the Massachusetts Bay Colony. Significant flooding likely occurred at the upper reaches of Narragansett Bay. It is unknown the extent of flood damage that occurred because Providence was not founded by Roger Williams until the following year. (5) Learn more.
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September 1815 – The Great September Gale
The first major hurricane to strike Rhode Island after statehood was the Great Gale of 1815, which made landfall near Old Saybrook, CT. Providence suffered a storm tide around 18 feet and downtown was completely inundated. An account of the storm’s impact on Bristol notes “…all the vessels were driven a great distance in on the land, and considerably injured. There the tide rose seven feet higher than it was ever known to rise before, and the wharves were completely swept away.” (2,4) Learn more.
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September 1938 – The Great New England Hurricane
The most destructive hurricane to strike Rhode Island in recorded history produced a storm surge of 12’-15’ in Narragansett Bay. At the time, the storm surge was referred to as a tidal wave because it coincided with the daily high tide. Providence suffered the greatest from this storm, as portions of downtown were submerged under 20’ of water. The south coast was devastated from significant coastal flooding that occurred from Westerly to Little Compton. This hurricane was so powerful it changed the geography of Napatree Point, Rhode Island’s westernmost point. (4) Learn more.
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August 1954 – Hurricane Carol
16 years after the Great New England Hurricane, Hurricane Carol followed a similar path up the East Coast and produced catastrophic damage in Rhode Island. Significant flooding occurred in downtown Providence, where a 13.7’ storm surge was recorded. Sea levels rose similarly to the 1938 hurricane, with Narragansett Bay rising 7.75’ in the last hour prior to the maximum storm tide – this equates to 1.5’ every 10 minutes. The flooding caused by Hurricane Carol spurred the construction of the Fox Point Hurricane Barrier, completed in 1966 (3,4) Learn more.
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August 1991 – Hurricane Bob
Hurricane Bob was the most recent hurricane to make landfall in Rhode Island. In Narragansett Bay, Hurricane Bob produced a storm surge of 6.5’, which resulted in a storm tide 10.4’ above flood stage in Providence. Coastal flooding was most extensive in the low-lying areas of Bristol County and along the Little Compton shore. Farther inland, Hurricane Bob dropped 7.01” of rain in Foster in 24 hours. Several gravel roads were washed out in Coventry and flooding occurred in Johnston along the Pocasset River. (3,4) Learn more.
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April 2007 – Patriot’s Day Coastal Storm
A powerful late-season coastal storm impacted Rhode Island from April 16-17, 2007. Minor to moderate coastal flooding was observed in Narragansett Bay and along the south coast. In Providence, the Fox Point Hurricane Barrier was closed to protect downtown from flooding during the astronomical high tide cycle. The most significant impact was felt in Newport County, where part of the earthen dam that holds back South Easton Pond, a source of Newport’s drinking water, washed away. Large boulders that washed on the shore had to be removed with snowplows. (7,9)
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October 2012 – Superstorm Sandy
In October 2012, a unique storm system made landfall along the coast of New Jersey. “Superstorm Sandy” was originally a hurricane that underwent a transition to an extratropical cyclone. Despite making landfall over 200 miles from Rhode Island, the south coast was hit with a storm surge of 3’-5’. The immediate coastlines of Westerly, Charlestown, South Kingstown were devastated. Post-event surveys conducted by the National Weather Service remarked coastal flood damage was consistent with a Category-1 hurricane, not seen since Hurricane Bob in 1991. (7) Learn more.
Impacts by County: (1) Bristol County, (2) Newport County, (3) Washington County and Block Island.
References
- Historic Storms of New England (Perley, 1891)
- Rhode Island Hurricanes and Tropical Storms: A Fifty-Six Year Summary 1936-1991 (Vallee, 1993)
- Southern New England Tropical Storms and Hurricanes: A Ninety-Seven Year Summery 1900-1996 (Vallee and Dion, 1997)
- Storm Tides in Twelve Tropical Cyclones (including Four Intense New England Hurricanes) (Jarvinen, u.d.)
- NCEI Storm Events Database – Coastal Flooding
- NCEI Storm Events Database – Inland Flooding
- Troubled Waters in Newport (Kuffner, n.d.)