Hurricane Ida was so powerful it reversed the flow of the Mississippi River

Ryan W. Miller – USA TODAY

As the powerful Hurricane Ida roared ashore in Louisiana on Sunday, the storm’s force was so strong it temporarily reversed the flow of the Mississippi River.

Hitting as a Category 4 storm, Ida’s winds snapped trees and tore roofs off buildings as its floodwaters blocked roads and submerged cars. The storm was expected to dump up to 2 feet of rain in some areas and bring up to 7 feet of storm surge. Over a million people in Louisiana were without power.

A U.S. Geological Survey gauge at Belle Chasse, south of New Orleans, detected the Mississippi’s flow moving backward around midday Sunday  because of the amount of water Ida whipped up.

U.S. Army Corps of Engineers spokesman Ricky Boyette confirmed engineers detected a “negative flow” on the Mississippi River as a result of storm surge.

In the days leading up to Ida’s arrival, the river, which flows into the Gulf of Mexico, had a discharge rate hovering around 300,000 cubic feet per second. At the peak of the reversal, it was flowing nearly 40,000 cubic feet per second upriver. The reversal occurred for just over a couple hours.

Although rare, the river changing course is not unprecedented, occurring during Hurricane Katrina in 2005 and Hurricane Isaac in 2012.

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The Mississippi River is seen ahead of Hurricane Ida on Aug. 29, 2021 in New Orleans.  Brandon Bell, Getty Images

“I remember, off hand, that there was some flow reversal of the Mississippi River during Hurricane Katrina, but it is extremely uncommon,” Scott Perrien, a USGS hydrologist told CNN.

Perrien told the news outlet the river gauge does not measure the entire river and it was possible deeper sections did not reverse flow.

According to the gauge, the river, which is normally between 8 to 10 feet, rose to over 16 feet.

“The river is feeling the effects of the storm over a large area,” Perrien told CNN.

Downgraded to a tropical storm, Ida was about 50 miles north-northeast of Baton Rouge on Monday morning. The storm still had 60-mph winds and was forecast to bring heavy rains and flooding to Louisiana and Mississippi.

New Orleans Police detective Alexander Reiter, looks over debris from a building that collapsed during Hurricane Ida in New Orleans, Monday, Aug. 30, 2021. Hurricane Ida knocked out power to all of New Orleans and inundated coastal Louisiana communities on a deadly path through the Gulf Coast that is still unfolding and promises more destruction. – Gerald Herbert, AP