List of rivers that have reversed direction

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, or direct human intervention.

Permanent reversals

Construction of the Chicago Sanitary and Ship Canal

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]
Chicago River	Lake Michigan	Mississippi River	North America	1900	Construction of Chicago Sanitary and Ship Canal	[1]

Temporary reversals

The Reversing Falls of the Saint John River, flowing upriver

Intermittent reversals

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

River	Outlet	Continent	Date of reversal	Cause of reversal	References
Chicago River[lower-alpha 1]	Mississippi River	North America	2017 and others[lower-alpha 2]	Storm surge	[2]
Mississippi River	Gulf of Mexico	North America	1812	Tectonic uplift caused by New Madrid earthquakes	[3]
			2005	Storm surge from Hurricane Katrina	[1]
			2012	Storm surge from Hurricane Isaac	[1][4]

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.[2]

Regular reversals

All tidal sections of rivers reverse their flow with the tide about twice a day, by definition. The Hudson and the Saint John River are just examples.[5]

River	Outlet	Continent	Frequency of reversal	Cause of reversal	References
Hudson River	Upper New York Bay	North America	semidiurnal	Tide in Upper New York Bay	[5]
Petexbatún River	Pasión River	Central America	annual	Winter rain flooding of the Pasión River	[6]
Qiantang River	Hangzhou Bay	Asia	annually around August 15th	Tidal bore in Hangzhou Bay	[7]
Saint John River (Reversing Falls)	Bay of Fundy	North America	semidiurnal	Tide in the Bay of Fundy	[8]
Tonlé Sap River	Mekong River	Asia	annual	Monsoon flooding of the Mekong River	[9]

See also

• Stream capture, in which a stream or river is diverted from its own bed, and flows instead down a neighboring channel

References

1. Borneman, Elizabeth (November 24, 2014). "Rivers that Flow Backwards". Geo Lounge. Retrieved 18 March 2019.
2. "How Climate Change Is Making This River Run Backwards". EcoWatch. Natural Resources Defense Council. June 4, 2017. Retrieved 19 March 2019.
3. Soniak, Matt (January 25, 2013). "Has a U.S. River Run Backwards Before?". Mental Floss. Retrieved 18 March 2019.
4. "Mississippi River Flows Backwards Due to Isaac". USGS Newsroom. United States Geological Survey. August 29, 2012. Retrieved 19 March 2019.
5. "The Hudson Estuary: A River That Flows Two Ways". New York State Department of Environmental Conservation. Retrieved 19 March 2019.
6. The Petexbatún eco-system (in Spanish) Retrieved 30 January 2021.
7. The Bore Tides of the Qiantang River Retrieved 30 January 2021.
8. "Reversing Falls". New-Brunswick.net. Retrieved 18 March 2019.
9. 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.