Almost 10,000 residents in Louisiana have been given a mandatory evacuation order as Tropical Storm Barry swells the Mississippi River to historic levels.

The National Hurricane Center (NHC) predicted that the storm, which is slowly approaching the Gulf Coast, could elevate river levels to the highest they have been since the year 1927.

New Orleans’ Bourbon Street and Royal Street in the historic French Quarter are among the areas that have experienced significant flooding after 8 inches of rain fell during a three hour period on Wednesday.

The NHC also said Thursday that winds had reached up to 40 mph and are expected to grow stronger in the next few days as the storm continues to move further inland.

Barry is moving at a slower pace, which means rainfall will continue to be significant, adding to the already dangerous flooding conditions.

“Barry is expected to produce total rain accumulations of 10 to 15 inches near and inland of the central Gulf Coast through early next week, with isolated maximum rainfall amounts of 20 inches across portions of eastern Louisiana and southern Mississippi,” the NHC said in a bulletin issued Thursday.

“A tornado or two are possible tonight and Friday across southern portions of Louisiana and Mississippi,” the bulletin concluded.

Louisiana Gov. John Bel Edwards declared a state of emergency Wednesday, encouraging the public not to take the storm lightly and to have supplies on hand. He said:

Now is the time to check your emergency supplies and get a gameplan for your family and pets. I urge the public to continue monitoring local media for weather developments and follow the directions of local officials. We expect multiple parishes to declare states of emergency, and we stand ready to assist our local partners with all available resources. My office is in constant communication with FEMA and we will continue to provide updates as necessary.

NHC Director Ken Graham said that floodwater is the most dangerous part of tropical storms such as Barry. “It’s the water that’s the most deadly part of these tropical systems — 90 percent of the fatalities in these tropical systems is the water,” he warned.

Reports state that if the tropical storm becomes a hurricane in the coming days, it will likely be a Category 1 storm.