The floodwaters deluging Houston -- America's fourth largest city and a major global oil hub -- also present Donald Trump with a significant long-term test of his presidential leadership.

Facing tropical storm Harvey, Trump plans to travel to "The Lone Star State" on Tuesday, a demonstration that he is on top of a disaster that is already posing a fierce challenge for local and federal responders.

The full impact of the ongoing storm is unknown, but up to 30,000 people are expected to need emergency shelter as -- thanks to plant-shutdowns -- gasoline prices surged four percent in early New York trade.

Since the crisis began on Friday, Trump has seized on his role marshalling the federal response, issuing a disaster declaration for Texas and neighboring Louisiana and deploying 8,000 officials throughout the flood zone.

During a busy weekend, the White House released photos of the president -- decked in a USA cap -- huddling with aides, liaising with cabinet secretaries to discuss what he called a "once in 500 year flood."

A steady stream of tweets have sought to show that the president, who spent the weekend at the bucolic presidential retreat of Camp David, was well apprised and in control.

"They're providing everything we've asked for" Texas's Republican governor Greg Abbott said describing Washington's response.

Trump's trip to Texas comes much more quickly than other presidents may have dared. Along with a high-impact presidential trip comes the risk of hampering recovery efforts and tying up resources.

First Lady Melania Trump is also expected to travel.

With the rain still falling, they will have to avoid the area around Houston that has been hardest hit. But the president seems determined to show leadership on the ground.

In responding to Harvey, Trump appears cognizant of the political pitfalls his predecessors found in their flawed responses to Hurricanes Katrina and Andrew, when the federal government came up short.

Images of George W. Bush looking safely from the window of Air Force One down at ravaged New Orleans in 2005 became an indelible image of his presidency.

Trump's display of decisiveness comes in stark contrast to Trump's prevarications in the face of a white supremacist rally that turned deadly two weeks ago in Charlottesville, Virginia.

His failure to condemn the extreme right shook an already fragile administration.

And despite his hands-on response, Trump has already been pilloried for making a series of controversial announcements just hours before Harvey hit.

As the storm barreled towards the Gulf Coast, Trump pardoned a sheriff who had been accused of racism and convicted of defying the courts and banning transsexuals in the military.

- Management tools -

Post-Katrina reforms give Trump more levers to manage the crisis, but he will still have to coordinate several agencies and work with Congress to unblock funds.

That could be made more difficult by Trump's poor relationship with Republican members of Congress and a contentious and already jam-packed legislative agenda in September.

In the wake of Hurricane Sandy in 2012, a large number of Republican senators blocked relief to the devastated and predominantly Democratic northeastern states.

Grudges over that episode remain, and could be exacerbated by tensions over the need to raise the government's debt ceiling and a vote on the 2018 budget.

Trump has demanded Congress provide funds for his unpopular border "wall," something many lawmakers are reluctant to do.

Beyond that, the scope and scale of the damage from Harvey may pose a durable challenge for a president who often seems to think in 140-character blocs.

The long-term economic impact could be as severe as the immediate humanitarian need, with small businesses in need of loans and insurance payouts to get the local economy back on its feet.

And Houston's role as an oil hub and major port makes the impact truly global in scale.

According to research from Goldman Sachs, the storm has put 16.5 percent of US refinery capacity offline and 11 percent of crude oil production, although many of the closures have been preventative.

"This is going to be a very long-term project, helping Texas dig out," governor Abbott told CNN.

Vice President Mike Pence tried to reassure Texans that the White House's focus would not be fleeting.

"We're very confident that, working with the Congress, we'll be there for the long haul," he said. "We'll see Houston all the way back and provide all of the appropriate support from the federal government."

Source: AFP