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Reversing Falls of Saint John River

A number of rivers are known to have reversed the direction of their flow, either permanently or temporarily, in response to geological activity, weather events, climate change, tides, or direct human intervention.

Permanent reversals


River Original outlet Current outlet Continent Date of reversal Cause of reversal References
Amazon River Pacific Ocean Atlantic Ocean South America Cretaceous period Formation of Andes Mountains [1]
Wisconsin River Great Lakes Basin Mississippi River North America Pleistocene Epoch Pre-Illinoian glaciers [2]


River Original outlet Current outlet Continent Date of reversal Cause of reversal References
Chicago River Lake Michigan Mississippi River North America 1900 Construction of Chicago Sanitary and Ship Canal [1]

Temporary reversals


All tidal sections of rivers reverse their flow with the tide about twice a day (or semidiurnally), by definition. The following are notable examples.[3]

River Outlet Continent References
Hudson River Upper New York Bay North America [3]
Saint John River (Reversing Falls) Bay of Fundy North America [4]
Salmon River Bay of Fundy North America [5]
Channel of Vivari Straits of Corfu Europe [6]


River Outlet Continent Cause of reversal References
Krupa River Neretva River Europe High water levels of the Neretva River [7]
Petexbatún River Pasión River Central America Winter rain flooding of the Pasión River [8]
Qiantang River Hangzhou Bay Asia Tidal bore in Hangzhou Bay [9]
Tonlé Sap River Mekong River Asia Monsoon flooding of the Mekong River [10]


Hurricane storm surges often cause temporary reversals of coastal rivers.[1]

River Outlet Continent Date of reversal Cause of reversal References
Chicago River[a] Mississippi River North America 2017 and others[b] Storm surge [11]
Mississippi River Gulf of Mexico North America 1812 Tectonic uplift caused by New Madrid earthquakes [12]
2005 Storm surge from Hurricane Katrina [1]
2012 Storm surge from Hurricane Isaac [1][13]
2021 Storm surge from Hurricane Ida [14]
  1. ^ These reversals represent a return to the Chicago River's original natural outlet in Lake Michigan.
  2. ^ Reversals of the Chicago River have been increasing in frequency in association with global warming, and may soon occur at least once each year.[11]

See also


  1. ^ a b c d e Borneman, Elizabeth (November 24, 2014). "Rivers that Flow Backwards". Geo Lounge. Retrieved 18 March 2019.
  2. ^ "When the Wisconsin River Flowed East". 11 September 2018.
  3. ^ a b "The Hudson Estuary: A River That Flows Two Ways". New York State Department of Environmental Conservation. Retrieved 19 March 2019.
  4. ^ "Reversing Falls". Retrieved 18 March 2019.
  5. ^ Dinshaw, Fram (June 19, 2018). "What a bore! Truro's 'marvellous' tidal event a daily tourist draw | SaltWire". Retrieved 2023-02-06.
  6. ^ Butrint National Park - Combining Natural Park with Cultural Heritage Retrieved 8 May 2024.
  7. ^ Krupa River Retrieved 30 August 2022.
  8. ^ The Petexbatún eco-system (in Spanish) Retrieved 30 January 2021.
  9. ^ The Bore Tides of the Qiantang River Retrieved 30 January 2021.
  10. ^ Jennings, Ken (February 2, 2015). "Why the Tonle Sap River Is Unlike Any Other River in the World". Condé Nast Traveler. Retrieved 18 March 2019.
  11. ^ a b "How Climate Change Is Making This River Run Backwards". EcoWatch. Natural Resources Defense Council. June 4, 2017. Retrieved 19 March 2019.
  12. ^ Soniak, Matt (January 25, 2013). "Has a U.S. River Run Backwards Before?". Mental Floss. Retrieved 18 March 2019.
  13. ^ "Mississippi River Flows Backwards Due to Isaac". USGS Newsroom. United States Geological Survey. August 29, 2012. Retrieved 19 March 2019.
  14. ^ "Hurricane Ida Is So Strong It Reversed the Mississippi's Current". 2021-08-30. Retrieved 2021-08-30.