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.
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] |
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 | [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] |
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] |