Donald Trump flew to Texas on Tuesday to view the trail of destruction from tropical storm Harvey that has killed at least 18 people, displaced tens of thousands and defied conventional measurements.

But Houston was braced for fresh damage as a vital dam began overspilling and more rain was forecast in the continued onslaught from one of the worst natural disasters in US history. On Tuesday evening, the city’s mayor, Sylvester Turner, announced a curfew between midnight and 5am “to ensure public safety” and “prevent potential criminal acts”.

Quick guide Tropical storm Harvey and climate change Show Hide Is there a link between the storm and climate change? Almost certainly, according to a statement issued by the World Meteorological Organization on Tuesday. “Climate change means that when we do have an event like Harvey, the rainfall amounts are likely to be higher than they would have been otherwise,” the UN organisation’s spokeswoman Clare Nullis told a conference. Nobody is arguing that climate change caused the storm, but it is likely to have made it much worse. How did it make it worse? Warmer seas evaporate more quickly. Warmer air holds more water vapour. So, as temperatures rise around the world, the skies store more moisture and dump it more intensely. The US National Weather Service has had to introduce a new colour on its graphs to deal with the volume of precipitation. Harvey surpassed the previous US record for rainfall from a tropical system, as 49.2 inches was recorded at Mary’s Creek at Winding Road in Southeast Houston, at 9.20am on Tuesday. Is this speculation or science? There is a proven link – known as the Clausius-Clapeyron equation – that shows that for every half a degree celsius in warming, there is about a 3% increase in atmospheric moisture content. This was a factor in Texas. The surface temperature in the Gulf of Mexico is currently more than half a degree celsius higher than the recent late summer average, which is in turn more than half a degree higher than 30 years ago, according to Michael Mannof Penn State University. As a result there was more potential for a deluge. Are there other links between Harvey and climate change? Yes, the storm surge was greater because sea levels have risen 20cm as a result of more than 100 years of human-related global warming. This has melted glaciers and thermally expanded the volume of seawater.



However, the curfew did not apply to “flood relief volunteers, those seeking shelter, first responders, and those going to and from work”.

Trump and Melania, the first lady, touched down on Tuesday morning for briefings on relief and response. The couple avoided Houston and the other hardest hit areas amid concerns that the logistics could hamper relief efforts.

Trump has been active on Twitter and is eager to avoid comparisons with George W Bush, who was much criticised for his response to Hurricane Katrina in New Orleans a decade ago.

Play Video 2:44 Tropical storm Harvey: the story so far – video report

The president said in Corpus Christi: “It’s a real team and we want to do it better than ever before. We want to be looked at in five years, in 10 years from now as, ‘This is the way to do it.’ This was of epic proportion. Nobody’s ever seen anything like this and I just want to say that working with the governor and his entire team has been an honour for us.”

He added: “We won’t say congratulations. We don’t want to do that. We’ll congratulate each other when it’s all finished.”

Greg Abbott, the Republican governor of Texas, expressed gratitude. He said: “About 10 days in advance of the hurricane, even coming in to the Corpus Christi area, members of the president’s cabinet and the president himself were in contact with me and my office pre-preparing for this catastrophe coming our way.”

Trump came out of the Annaville firehouse and got up on a ladder between two fire trucks. “Thank you,” he said to applause. “We love you, you are special, we are here to take care of you. It’s going well.” He then held up the Texan flag to loud cheers.

“What a crowd, what a turnout,” he added.

Later, Trump visited the Texas department of public safety where according to a pool report there was a sizable anti-Trump demonstration, with signs saying “Nyet” and “Impeach little hands”.

Wearing cap and raincoat, Trump told scores of disaster responders: “I will tell you, the whole country and the whole world is really seeing and gaining such respect for everybody. The job you have done is incredible, what we have done is under circumstances, I said before, the word ‘epic’ and ‘historic’, these are words used to describe this monster known as Harvey, but the job you have done is special.”

Accompanied by the housing and urban development secretary, Ben Carson, Trump could not resist passing comment on the name Harvey.

“Probably there has never been anything so expensive in our country’s history, we’ve never done anything so historic in terms of damage and in terms of ferocity as what we’ve witnessed with Harvey. It sounds like such an innocent name, Ben, right, but it’s not innocent.”

Harvey made landfall near Corpus Christi on Friday evening as a category 4 storm with 130mph winds. It has since been downgraded to a tropical storm but has set a new US record for rainfall from a tropical system, with some parts of Houston recording more than 40in (100cm) of rain and Cedar bayou, near Mont Belvieu, 33 miles east of Houston hitting 51.88in (132 cm) as of 3.30pm on Tuesday.

On Tuesday, boat crews raced to carry out dramatic rescues of residents stranded by “unprecedented” flooding in Houston, America’s fourth biggest city, and take them to shelters. Homes and other buildings in and around near Houston are semi-submerged, and major roads resemble rivers. The worst could be yet to come.

A pair of 70-year-old reservoir dams that protect downtown Houston and a levee in a suburban subdivision started overflowing. Jeff Lindner, a Harris County meteorologist, said water levels in the Addicks reservoir have reached 108ft and warned that neighbourhoods in the spillway zone would begin to see street and possibly structural flooding.

Facebook Twitter Pinterest A man walks with belongings after being rescued from a flooded neighborhood in Houston. Photograph: Brendan Smialowski/AFP/Getty Images

“We have never faced this before, we have uncertainty in how the water is going to react as it moves out of the spillway and into the surrounding area,” he said on Tuesday. “We are trying to wrap our heads around what this water will do.”

Linder named six subdivisions that appeared most at risk and told residents: “If you want to leave, now is the time to leave. The reason being, once the water comes into the street you’re not going to be able to leave.”

Another major dam and reservoir nearby, Barker, is also enduring exceptionally high water levels and some residents nearby are under voluntary evacuation orders and facing the possibility that their roads could be rendered impassable just as the storm’s precipitation appears to be decreasing in intensity.

Officials in Brazoria County said the levee at Columbia Lakes, just south of Houston, has been breached and tweeted a red warning sign that said: “GET OUT NOW!!” Trump retweeted it on his own feed. The levee was later fortified, but officials said they did not know how long the work would hold. A mandatory evacuation in some parts of the county was ordered two days ago.

The Houston region’s dramatic population growth – about a million new residents in the past decade – has seen extensive construction of new houses, offices and apartment complexes built around the dams in what once was empty grassland.

Houston police chief Art Acevedo told reporters that emergency personnel have conducted more than 3,500 rescues since Harvey’s floodwaters began overtaking the city.

Trump's rollback of flood protections risks further Houston-style calamity Read more

He also said armed robbers were arrested overnight and a “handful” of looters were also taken into custody. He warned that he will lobby judges and prosecutors to secure the most severe punishment Texas law allows. “This is Texas,” he said.

Acevedo told the Associated Press: “We know in these kinds of events that, sadly, the death toll goes up historically. I’m really worried about how many bodies we’re going to find.”

More than 17,000 people have sought refuge in Texas shelters, the American Red Cross said. Houston’s George R Brown convention centre was rapidly approaching double its original estimated capacity for evacuees: around 9,000 people have arrived at the centre. The Red Cross had 5,000 cots, leaving many people to sleep on chairs or the floor.

Meanwhile televangelist Joel Osteen opened his Houston megachurch, a 16,000-seat former arena, as a shelter after criticism on social media. Osteen announced the effort in a tweet, insisting that he and wife Victoria Osteen “care deeply about our fellow Houstonians”.

It could be weeks before they are able to return to their homes. Many hospitals in the city were closed and 100,000 people were without power.

The storm has dumped 9tn gallons on the region – as much in two days as it normally receives in a year. A further 20 inches of rain is forecast to fall by the end of the week, prompting a warning that flood levels will not peak in south-east Texas until Wednesday and Thursday.

At least 18 people have been killed in the storm. They include six members of the same family whose van was swept away in the flood water, a man in his 60s presumed drowned after trying to swim to safety, and police sergeant Steve Perez, 60, who drowned in his patrol car after he became trapped in high water while driving to work. Perez had been with the force for 34 years.

A weather station south-east of Houston reported 49.32in (125.27cm) of rain as of Tuesday morning. That breaks the previous record of 48in (122cm) set in 1978 in Medina, Texas, by tropical storm Amelia.

The Pentagon said there were about 3,500 national guard troops involved, including about 3,000 from the Texas national guard.

Concern is also mounting about destructive flooding in Louisiana, where the storm is heading next. Trump issued a federal state of emergency for the the state. The National Hurricane Center warned of “ongoing catastrophic and life-threatening flooding” spreading from Texas to Louisiana, with total rainfall of 50in (1.27 metres) in some parts.

The clean-up operation is expected to take years and cost billions of dollars. Federal Emergency Management Agency administrator Brock Long told the New York Times: “Texas is about to undergo one of the largest recovery housing missions the nation has ever seen.”