List of rivers that have reversed direction
# 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

### Natural

| 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 | |
| Wisconsin River | Great Lakes Basin | Mississippi River | North America | Pleistocene Epoch | Pre-Illinoian glaciers | |

### Artificial

| 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 | |

## Temporary reversals

### Daily

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

| River | Outlet | Continent |
| - | - | - |
| Hudson River | Upper New York Bay | North America |
| Saint John River (Reversing Falls) | Bay of Fundy | North America |
| Salmon River | Bay of Fundy | North America |

### Annual

| River | Outlet | Continent | Cause of reversal |
| - | - | - | - |
| Krupa River | Neretva River | Europe | High water levels of the Neretva River |
| Petexbatún River | Pasión River | Central America | Winter rain flooding of the Pasión River |
| Qiantang River | Hangzhou Bay | Asia | Tidal bore in Hangzhou Bay |
| Tonlé Sap River | Mekong River | Asia | Monsoon flooding of the Mekong River |

### Intermittent

Hurricane storm surges often cause temporary reversals of coastal rivers.

| River | Outlet | Continent | Date of reversal | Cause of reversal |
| - | - | - | - | - |
| Chicago River | Mississippi River | North America | 2017 and others | Storm surge |
| Mississippi River | Gulf of Mexico | North America | 1812 | Tectonic uplift caused by New Madrid earthquakes |
| Mississippi River | Gulf of Mexico | North America | 2005 | Storm surge from Hurricane Katrina |
| Mississippi River | Gulf of Mexico | North America | 2012 | Storm surge from Hurricane Isaac |
| Mississippi River | Gulf of Mexico | North America | 2021 | Storm surge from Hurricane Ida |

* ↑ These reversals represent a return to the Chicago River's original natural outlet in Lake Michigan.
* ↑ Reversals of the Chicago River have been increasing in frequency in association with global warming, and may soon occur at least once each year.
