MIAMI, United States (AFP) — Two more days of heavy rainfall are expected over parts of Texas and Louisiana as Tropical Storm Harvey churns offshore, preparing to make landfall again today.

“The single greatest threat continues to be the rainfall,” Dennis Feltgen, a spokesman for the Miami-based National Hurricane Center, told AFP, describing the situation as “catastrophic”.

“This is not over,” he said.

Already some 50 inches (127 centimetres) of rain have fallen over Houston since Harvey hit Friday as a Category Four hurricane, sparking massive floods across the densely populated metropolitan area.

“Relentless torrential rains continue over south eastern Texas and southwestern Louisiana,” the National Hurricane Center said.

Harvey is edging away from Houston and is currently in the Gulf of Mexico.

With neighbouring Louisiana squarely in the storm’s path, Harvey, now a tropical storm, is pressing eastward and is expected to make landfall again by early today.

New Orleans residents are bracing for heavy rain and flash floods over the next two days.

As of Tuesday morning, two inches of rain had already fallen over New Orleans.

“Flash flooding is expected to begin shortly,” said the National Weather Service in New Orleans.

The city famous for its jazz music and cuisine is particularly vulnerable because it lies below sea level.

New Orleans is also fresh off another major flood earlier this month that was exacerbated by problems with the city’s pumping system.

“It is really sort of a wild card right now,” meteorologist Eric Holthaus told AFP.

“There are some forecasts for up to 10 inches of rain over the next 36 hours or so for New Orleans. I would definitely not be surprised if it became more than that.”

Houston can expect two to four more inches of rain as the storm moves away, but flooded conditions will likely linger through the end of the week as the rainfall drains off, Holthaus said.

The National Hurricane Center said six to 12 inches of rain could accumulate by Friday over parts of upper Texas and south-western Louisiana.

Arkansas and Tennessee could see four to eight inches of rain as the storm heads inland.

Forecasters say Harvey will likely dissipate after it hits land again, and the rains should be all but over by Friday.

… Evacuation ordered as levee breaches south of Houston

HOUSTON, Texas (AFP) — Floodwaters have breached a levee south of the city of Houston, officials said yesterday, urging residents to leave the area immediately.

“The levee at Columbia Lakes has been breached!!” the Brazoria County government tweeted on its official feed. “GET OUT NOW!!”

The Columbia Lakes area lies south of Houston, large parts of which remain underwater four days after monster storm Harvey made landfall on the US Gulf Coast, triggering widespread flooding.

A statement on the official Brazoria County website said that County Judge Matt Sebesta “has issued a MANDATORY EVACUATION for all residents living WEST of State Highway 288 and SOUTH of State Highway 6.”

The statement said there was only one way out of the area.

“THERE ARE NO OTHER EVACUATION ROUTES OUT OF BRAZORIA COUNTY,” the statement said, adding that one state highway “WILL NOT be open indefinitely and will be unpassable with additional rains and river flooding.

“LEAVE NOW!”

The statement directed evacuees to a shelter at the Expo Center in Bell County — about 230 miles (370 kilometers) to the northwest — adding: “Pets are welcome!”