Hurricane Ida Force Changes Mississippi River’s Course

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The storm and strong winds from Hurricane Ida disrupted the flow of the Mississippi River near New Orleans on Sunday and caused it to reverse – something the US Geological Survey says is “extremely unusual.”

The Ida touched down near Port Fourchon, Louisiana, early Sunday afternoon as an extremely dangerous Category 4 hurricane with 150 mph winds, said the National Hurricane Center (NHC). The hurricane arrived on the 16th anniversary of the historically devastating Hurricane Katrina.

“I remember from above that there was some reversal of Mississippi River flow during Hurricane Katrina, but it’s extremely unusual,” said Scott Perrien, a supervising hydrologist at the USGS Lower Mississippi Gulf Water Science Center in Baton Rouge, Louisiana, to CNN.

Perrien noted that the river level on Sunday rose about 7 feet due to the storm that pushed the river above the USGS gauge, located at Belle Chasse, about 20 miles south of New Orleans in southeastern Louisiana.

“During that time, the flow of the river has decreased from about 2 feet per second to about half a foot per second in the other direction,” Perrien said.

Perrien pointed out that the meter does not measure the flow of the entire river, so it is possible that the deeper portions of the river do not reverse flow directions.

“The river is feeling the effects of the storm over a large area,” Perrien told CNN. “All the way to Baton Rouge, the river has risen 1.5 feet in the last 12 hours as the storm pushes the river up. And the water level will probably rise further in the next few hours here in Baton Rouge.”

The Ida became a Category 4 storm early Sunday morning and tied as the most powerful storm in Louisiana with Hurricane Laura of 2020 and Last Island Hurricane of 1856 – all with 240 winds. km/h.

During Hurricane Laura, strong winds blew the upper Mississippi River upstream from the Gulf and slowed the main current of the river.

Hurricane Ida arrives on the anniversary of Hurricane Katrina, which hit Louisiana in 2005 as a Category 3 storm with sustained winds of 200 km/h. The storm wave with Katrina measured up to 24-28 feet, according to the NHC.

In comparison, Hurricane Ida is predicted to bring a smaller storm, 12-16 feet, to some areas of southeastern Louisiana, says the NHC.

Near New Orleans, it’s expected to be even lower: 8-12 feet outside of New Orleans and 5-8 feet along Lake Pontchartrain.

That’s because the wind field was larger for Katrina: 90 miles off center at the foot of the hurricane, compared to 50 miles for Ida.