A lot of New Yorkers treat the Hudson River like background scenery at best and a giant puddle to avoid at worst. But beneath that murky surface, the river is doing something wildly unusual: it changes direction about every six hours, flowing north and south in a daily tidal tug-of-war.
Instead of flowing only toward the Atlantic Ocean like most rivers, parts of the Hudson actually reverse course twice a day. The phenomenon affects more than 150 miles of the river and makes the Hudson one of the largest tidal estuaries in the United States.
Why does the Hudson River flow backward?
The lower half of the Hudson is controlled less by gravity and more by the Atlantic Ocean’s tidal pulse.
As the ocean tide rises, seawater pushes upstream into the river, forcing the current to move northward. When the tide falls, gravity takes over and the river resumes its southbound flow toward New York Harbor. This cycle repeats twice daily, creating a steady rhythm of reversing currents…