The U.S. Geological Survey said storm surge and the force of winds caused by Hurricane Ida stopped and reversed the flow of the Mississippi River in Louisiana.

Ida, now a tropical storm, made landfall in Louisiana as a Category 4 hurricane with winds of up to 150 mph.

A USGS river gauge in Belle Chasse, Louisiana, about 20 miles north of New Orleans, recorded a 7-foot storm surge that pushed up the river, slowing the river’s flow from about two feet per second to half a foot per second in the opposite direction.

The USGS told CNN the flow reversal was extremely uncommon, with the last occurrence happening 16 years ago during Hurricane Katrina.

At least one person has died due to the storm, and more than a million homes and business are without power after “catastrophic damage” to the regional power provider’s electrical transmission system.

The National Hurricane Center said the rain and storm surge “resulted in catastrophic impacts along the southeast coast of Louisiana,” and the storm could still cause damage as it moves inland.

Scientists from the National Oceanic and Atmospheric Administration and other researchers have found that climate change is increasing the number of named storms per year and is probably increasing their intensity.

Last year, the Atlantic Ocean experienced the most named tropical storms ever, and the second-highest number of hurricanes on record.

Forecasters from the NOAA’s Climate Prediction Center said this year’s hurricane season is not expected to be as active as last year’s, but there is still a 60% chance of an above-normal season.