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 storm Harvey.

Brazoria County authorities warned residents on Tuesday to "get out now!" after a 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.

President Trump arrives in Texas

But the releases were 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 under water for up to a month.


President Donald Trump has arrived in Texas to survey the damage caused by the storm in the first major natural disaster of his White House tenure.

He flew into Corpus Christi, where Harvey first made landfall, and will also meet rescue officials in Austin.

:: 'Biblical scale' flooding leaves Texans devastated

At least nine people have been killed by the slow-moving storm in Texas, but many others have been reported missing by worried loved ones.

Six members of the same family are feared dead after their van was submerged by a strong current as they tried to flee the storm.

Samuel Saldivar was trying to drive his elderly parents and their grandchildren to safety when the van was engulfed by violent floodwaters.

Image: A map showing the rain still hitting the Houston area. Pic: NWS

Although he managed to climb out of a window, no one else managed to escape - including four siblings aged between six and 16.

The coastguard has told the family they will not be able to search for the bodies until the water recedes.

:: Citizens help save lives amid Harvey chaos

Image: Six members of the Salvidar family are presumed drowned. Pic: Facebook

Parts of Houston, America's fourth-largest city, have seen 76cm of rainfall so far - and a further 61cm is forecast.

More than 3,500 people have been rescued by the National Guard following the storm. Up to 30,000 soldiers have been placed on standby to assist in rescue and recovery efforts.

Man rescued from submerged car in Houston floods

Major General James Witham, of the US Air Force, said the rescue operation "will be a long effort".

He said: "We will be doing life-saving and life-sustaining efforts for a much longer period due to the nature of this storm."

:: 'I fear I'll have no home to go back to'

Image: Boats replace vehicles on the roads in east Houston

The amount of water in Houston is so unprecedented that the National Weather Service has had to update its official rainfall maps, introducing new colours representing higher amounts to accurately record the torrential downpours.

Southwestern parts of Louisiana are also preparing for potentially disastrous flooding, and hundreds of people have already been 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.

It could move as far east as Mississippi by Thursday, meaning New Orleans could be in its path. Tuesday is the 12th anniversary of the day Hurricane Katrina hit the city in 2005.

:: Watch special report Houston Underwater on Sky News at 6.30pm and 9.30pm.