As Isaac Swept Ashore, Miss. River Flowed Backwards

Terrell Johnson Updated: Sep 11, 2012, 7:32 AM EDT weather.com

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Rare Reversal Last Occurred with Hurricane Katrina

FREDERIC J. BROWN/AFP/GETTYIMAGES

People brave the rain and strong winds for a walk along the banks of the Mississippi River in New Orleans early in the day on August 28, 2012 in Louisiana, where Hurricane Isaac made landfall. Starting in the late afternoon, the river reversed course and began flowing away from the Gulf of Mexico.

Most of the time, rivers large and small are as consistent as the tides, flowing from their headwaters to their mouths, where they empty into oceans, lakes, seas and valleys. For nearly 24 hours during Hurricane Isaac, however, exactly the opposite happened in the mighty Mississippi River.

The category 1 storm's intense winds and storm surge, which came ashore near New Orleans on Aug. 28, pushed salt water from the Gulf of Mexico up the fresh water river as far north as Baton Rouge, more than 200 miles from the mouth of the Mississippi, surging the river there more than 8 feet over its previous height.