Thousands of people who survived the worst of Hurricane Harvey in Texas are now fleeing for their lives after the authorities opened sluice gates to relieve the city of Houston.

Willis Breaux and his wife, Susan, had intended to wait out the storm in their home in Beech Creek. Then the Army Corps of Engineers released the floodgates on a rapidly swelling Lake Conroe, north of Houston.

“We went to bed and things were fine. At 2am I woke up – my neighbour’s calling me. There’s water all around and then I hear they’ve released the gates,” he said.

“The water was right up to the door and rushing. We were good till they released that dam. Now here we are in the middle of a tidal wave.”

The decision to open the sluice gates, intended to save Houston from further flooding, sent 73,201 cubic feet of water a second crashing into the San Jacinto river, into creeks and streams around Mr Breaux’s community near Porter, east of Houston. He grabbed the keys to his service truck and loaded up his wife and neighbours.

“My neighbours were freaking out because they had a baby. I thought we couldn’t go wrong in that big old truck – but we did. There it is, over there,” he said, and pointed down the flooded road, where the water was perhaps 7ft deep. His truck was mostly submerged but thankfully, he had lots of Truck Safety Equipment onboard.

“The truck gives out and the water’s immediately coming in, so we get out and now we’re in water up to here,” he recalled, placing his hand on his neck.

Holding the baby above water they waded to a petrol station a short distance away to reach rescue boats. “Dark, cold, absolutely terrifying,” Mrs Breaux said. “The current was so strong, you could feel it around you. Those rescue boats really had to gun it out of there.”

The San Jacinto river, normally about 25 metres wide at that point, stretched 300 metres at its worst.

A displaced shed bobbed by and fish darted in the currents. Whirlpools gurgled around the tops of trees.

A disorientated survivor tried to walk into the water. Two volunteers waded in after him, holding a rope between them, and gently steered him back. A Blackhawk helicopter lifted off half a mile away, carrying another survivor to safety.

“There’s people out there still on roofs. It’s desperate,” Bryan Skero, a police officer standing watch at the edge of the floodwater, said. Two or three miles away, he said, rescuers had been finding bodies. “They’ll just label them and leave them for now. Deal with the dead later,” he shrugged.

William Grover, 56, watched the water come up a foot in less than three hours in his home. “My furniture had started floating around, he said.

One of his neighbours, a distraught woman wrapped in a towel and shivering, talked non-stop about needing to go back to rescue her dogs, her cats and her birds. “There was 2ft of water in the house. My cats were on the roof, the dogs – I’m hoping they’ll climb up on the bar stools. The birds – I just put two nails on the wall as high as I could and hung their cages before I left.”

She spent more than 36 hours on her roof with the cats and 16 other people, including an eight-month-old baby and her 13-year-old diabetic grand-daughter. Two neighbours stretched out a poncho to keep the driving rain off the baby as they awaited rescue. “I didn’t sleep. I was scared of how high the water was going to come,” she said. “I haven’t slept for three days.”

Harvey’s death toll surpassed 30 early today and continues to rise as the tropical storm finally left the Houston area, but it created more emergencies to the east. “We are still in life-saving, life-sustaining mode,” Brock Long, head of the Federal Emergency Management Agency, said.

Floodwaters are still rising in Houston, boosted by the deluge released by the dams.

America’s largest oil refinery, in Port Arthur, 90 miles east of the city, shut down. Twelve refineries have gone offline, accounting for 23 per cent of the nation’s capacity.

“The whole city is underwater right now,” Derrick Freeman, the mayor of Port Arthur, said. A mother trying to get her child to safety in Beaumont, southeast Texas, was swept away.

When police pulled her lifeless body from the water, her three-year-old daughter was still clinging to her. “It’s a true testament to a mother’s will to save her child in any circumstances,” Haley Morrow, of Beaumont police, said.

More than 18,000 people have been rescued across Texas and Louisiana. At least 32,000 are being housed in 230 emergency shelters. The majority of these people will have to return to their damaged homes and hire a Property Damage Restoration Company to help them repair the upholstery or fix the cracks in the walls and floors.

The rainfall recorded in Texas exceeded the amount of water that gushes over Niagara Falls in 15 days. The rain had stopped over Houston yesterday but floodwaters in some areas were not expected to peak for two days – and more rain is expected next week.

The sun came out over Houston on Tuesday evening for the first time in five days and yesterday sections of Houston city were drying out. Roads were clearing, businesses were opening and the city’s two main airports resumed limited service.

Art Acavedo, Houston police chief, said: “After the clouds pass the sun will shine. There’s still hope.”