Officials have confirmed a levee south of Houston has been breached - warning residents to "get out now"
At least 11 people, including an on-duty police officer, have been killed in Texas as Tropical Storm Harvey continues to wreak havoc in the state.
Many others have been reported missing and authorities fear the death toll could rise significantly.
US President Donald Trump arrived into the area this evening to inspect the devastation caused by the slow moving storm.
On his arrival, President Trump said the flooding around the state was of "epic proportion."
He flew into into Corpus Christi, where the storm initially made landfall, where he surveyed some of the damage caused by the flooding.
He told rescue organisers: "This was of epic proportion, nobody has ever seen anything like this."
He went on to praise the officials in the coastal city - but added that it is too early to congratulate them:
"This has been a total cooperative effort," he said. "I will tell you; this is historic; it is epic what has happened; but you know what? It happened in Texas and Texas can handle anything."
White House press secretary Sarah Huckabee Sanders said the president's visit would focus on laying the groundwork for what is expected to be a long recovery effort.
She said the city of Houston was not on his itinerary because much of it remains impassable.
She said: "The president wants to be very cautious about making sure that any activity doesn't disrupt the recovery efforts that are still ongoing."
This afternoon, officials confirmed a levee south of Houston has been breached and two reservoir dams that protect the centre of the city have begun overflowing as floodwaters continue to rise following the storm.
Brazoria County authorities warned residents to "get out now!" after the levee at Columbia Lakes began overflowing following five consecutive days of heavy rain.
Engineers began releasing water from the 70-year-old Addicks and Barker reservoirs on Monday to ease the strain on the dams.
But the release was not enough to relieve the pressure after one of the heaviest downpours in US history, the Army Corps of Engineers said.
Jeff Lindner, of the Harris County Flood Control District, said the release of water means more homes and streets will flood, with some houses potentially under water for up to a month.
He said public safety is the number one concern for authorities, but warned “this is something we’ve never seen before.”
“The water in the reservoirs is rising rapidly and has significant potential to cause additional flooding impacts,” he said.
Around 30,000 people are expected to be made temporarily homeless in what is the first natural disaster of President Trump’s tenure.
Police have plucked more than 3,500 people from flooded neighbourhoods across the city, with the coastguard's boats and helicopters rescuing another 3,000.
More than 1,000 calls requesting assistance are being made to the coastguard every hour - and with further rain expected in the coming days, the authorities are worried the worst is yet to come.
Officials in Houston have warned that the number of deaths could rise dramatically once the floodwaters have receded.
Major General James Witham, of the US Air Force, said the rescue operation "will be a long effort."
"We will be doing life-saving and life-sustaining efforts for a much longer period due to the nature of this storm," he said.
Southwestern Louisiana is also preparing for potentially disastrous flooding, with hundreds of people already evacuated from chest-deep water after a heavy band of rain inundated Lake Charles on Monday night.
Forecasters say the storm will linger over the Gulf of Mexico, before heading back inland east of Houston on Wednesday- putting New Orleans potentially in its path.
US Secretary of State Rex Tillerson said the president travelled to Texas to reassure communities they will get the support they need:
“I think he has plans to go back a second time which I think indicates the seriousness of the situation but also the commitment of the federal government to provide all of the assets that the state of Texas needs to respond to what is going to be a very, very long rebuilding process,” he said.
Large parts of the area around Houston remain underwater today – with certain parts of the region having recorded nearly 50 inches of rain since the storm first arrived.
Additional reporting from IRN ...