Hundreds of thousands of people in Texas and Louisiana were urged Friday to flee the path of Hurricane Harvey as the Gulf Coast braced for the most dangerous storm to hit the US mainland in over a decade.

Roaring towards land with winds whipping up to 110 miles (175 kilometers) an hour, the category two hurricane is predicted to smash into coastal Texas late Friday or early Saturday as a much more powerful category three storm, forecast to dump up to 35 inches (89 centimeters) of rain.

Harvey is on course to make landfall as the strongest storm since the devastating Katrina 12 years ago, triggering "catastrophic" floods in an area that processes some seven million barrels of oil a day -- in what could prove a major new test for President Donald Trump's administration. 

Several Texas counties ordered mandatory evacuation from coastal areas. 

Those residents not under mandatory orders were also urged to leave immediately, or bunker down for a storm that could stall over the area for four or five days, dropping historic amounts of rain and inflicting billions of dollars in damage that could take months to repair.

Local television footage showed supermarket aisles plucked bare, highways clogged with bumper-to-bumper traffic, and long lines snaking outside gas stations. 

"All the advice we can give is get out, and get out now," said Patrick Rios, the mayor of Rockport, Texas where an estimated 60 percent of the town's 9,500 residents had left.

Rios had blunt words for those determined to stay, telling them to "mark their arm with a sharpie pen, put their social security number" -- to be identified if found dead.

Coastal Texas is a fast-growing area, with some 1.5 million people moving into the area since 1999. Authorities said the combination of dense growth and a storm that could deposit a year's worth of rain in just days could prove deadly. 

"Texas is about to have a very significant disaster," Brock Long, director of the Federal Emergency Management Agency (FEMA), told CNN. "Their window to evacuate is rapidly coming to a close." 

The National Hurricane Center (NHC) warned of the "complete destruction of mobile homes," of many buildings "washing away," and some areas being left "uninhabitable for weeks or months."

Police in Montgomery County urged residents to unchain their dogs lest they risk drowning.

- Newborns evacuated -

Former president George W. Bush faced severe criticism in 2005 after FEMA appeared unprepared for the devastating damage inflicted by Katrina, and one Republican senator warned Trump to step up to the challenge at hand.

"Keep on top of hurricane Harvey don't make same mistake Pres Bush made w Katrina," Chuck Grassley urged the US leader in a tweet.

Trump tweeted that he had spoken with the governors of Louisiana and Texas and was "closely monitoring" developments.

In Texas, FEMA has prepositioned emergency supplies, and state authorities have mobilized some 700 army and air national guard troops to help with evacuation and recovery.

Corpus Christi -- a major oil refining center, where the hurricane was to make landfall early Saturday -- has issued voluntary evacuation orders, with CNN reporting a hospital there had evacuated 10 newborn infants to a facility inland due to the prospect of extended power outages.

Still, many Corpus Christi residents appeared bent on sitting the storm out, packing sandbags to protect their homes -- until the supply of sandbags ran out Thursday.

Evacuation was made mandatory in counties including Calhoun, San Patricio and Matagorda, as well as in the coastal towns of Port Arkansas, Rockport and Arkansas Pass.

Matagorda Sheriff Frank Osborne made clear he was not fooling around, telling TV station KHOU: "If you're in a mandatory evacuation area and you don't evacuate, don't call us. Because I'm telling you right now, I'm not going to put one of my deputies' life on the line to save somebody that didn't leave when they were asked to."

People east of the mammoth, three-mile (five-kilometer) seawall in Galveston Island were urged to evacuate. Galveston was the scene of the devastating 1900 hurricane that claimed an estimated 8,000 lives.

Officials in Houston, the biggest city in the storm's path, canceled school but did not anticipate an evacuation. 

Inland cities like San Antonio prepared to welcome evacuees, and some began arriving on Friday. 

- Refining hub -

Harvey, the first major storm of the annual Atlantic hurricane season, was bearing northwest at 10 miles per hour as of 10 am central time (1500 GMT) on Friday. 

FEMA chief Long said the most pressing danger was the storm surge, the high tides powered by powerful winds -- expected to reach between six and 12 feet (1.8 and 3.7 meters) in some areas -- but said many inland counties should prepare for a "significant inland flood event." 

Meteorologist Eric Holthaus told AFP the prospect of the storm stalling on the coast, lashing it with heavy rain for days, "is just terrifying."

"This is the sort of storm that meteorologists prepare for and think about for years," he said. "I'm not sure if everyone is really fully aware of how serious this storm is."

One-third of the US refining capacity is potentially under threat.

One oil drilling rig in the Gulf of Mexico has been evacuated, as well as 39 manned production platforms, according to the Bureau of Safety and Environmental Enforcement, representing an estimated 9.5 percent of oil output and 14.7 percent of natural gas output in the Gulf.

Should a refinery shut down, it could take a week to get it running again, said James Williams of WTRG Economics.

 

- New Orleans on alert -

Texas Governor Greg Abbott issued disaster declarations in 30 counties, allowing the state "to quickly deploy resources for the emergency response effort."

In neighboring Louisiana, where the storm was feared to deluge flood-prone New Orleans, Governor John Bel Edwards described the situation as "particularly dangerous."

Edwards issued an emergency declaration for his entire state.

In New Orleans, where Katrina killed more than 1,800 people, Mayor Mitch Landrieu said high-water rescue vehicles and boats were at the ready -- although there were no evacuations planned. 

source: AFP