Houston submerged, much more rain to come

Vast swathes of Houston are under water as authorities warned that Tropical Storm Harvey would dump a further 2 feet (60 centimeters) of rain, with sustained winds of up to 40 mph (65 kph).

Emergency services were already so swamped with calls they could only respond to life and death cases. That left many residents with the choice of staying in their homes with rising water levels or venturing into potentially deadly flood water.

According to the US Federal Emergency Management Agency (FEMA), around one-quarter of Texas's population has been affected, or some 6.8 million people, across 18 counties. At least two deaths have been reported.

The National Hurricane Center urged people to stay put if they were safe, although former directors of the service feared people would try their luck in the water over the next few days.

Read more: Hurricane Harvey disaster in Texas 'will be landmark event'

Mixed signals 

Before the storm, residents of Houston were given mixed signals on whether to evacuate, with the Texas governor and the Houston mayor advising different courses of action.

Desiree Mallard and her 2-year-old son arrived at an emergency shelter after escaping their apartment complex with an inflated air mattress. A Coast Guard vessel picked them up.

She told the Associated Press that she wished she had left before Hurricane Harvey approached the Texas Gulf Coast, but she saw on the news to stay in place.

"And then when it got bad, they said it's too late to evacuate," she said.

Mayor defends decision

Houston Mayor Sylvester Turner, who advised people not to evacuate, defended his advice on Sunday. 

"The decision that we made was a smart one. It was in the best interest of Houstonians," he said. "It was the right decision in terms of their safety and always we must put the interests of the city and Houstonians first. That's exactly what we did. We did what was the right thing to do."

He said factors that informed his decision included not knowing where Hurricane Harvey was headed, and the "crazy" logistics of evacuating a city of 2.3 million people within a couple of days.

Turner recalled the deaths of dozens of people in 2005 as they were stuck in 20 hours of gridlock trying to flee the city before Hurricane Rita hit. Rita changed course and made landfall elsewhere, but people died of heatstroke and in accidents in the chaos.

On Sunday Twitter users shared images of the disaster, showing the devastating effects of the flooding.

Wave bed sheets, residents told

The flooding in Houston was so comprehensive that authorities had trouble pinpointing the worst-hit areas. They urged survivors to go to their roofs and wave sheets or towels to attract attention.

People used inflatable beach toys, boats and even air mattresses to help get through the water to safety. The city's main convention center was quickly opened as a shelter.

Mayor Turner said authorities had received more than 6,000 calls for rescue. He urged drivers to stay off flooded roads to avoid adding to the number of those stranded.

"I don't need to tell anyone this is a very, very serious and unprecedented storm," Turner told a news conference. "We have several hundred structural flooding reports. We expect that number to rise pretty dramatically."

Volunteers joined emergency teams to rescue people from the water and their houses. Helicopters landed near flooded freeways, airboats buzzed across submerged neighborhoods and high-wheel vehicles drove through the water.

More rain to come

The National Weather Service warned that Houston and its suburbs could receive as much as 50 inches (1.3 meters) of rain, the most ever recorded in Texas. Some areas already received about half that amount on Sunday.

"The breadth and intensity of this rainfall is beyond anything experienced before," the National Weather Service said in a statement.

The center of Harvey, which started as a Category 4 hurricane (with sustained winds between130 and 156 mph), was still about 125 miles (200 km) from Houston and was forecast to move towards the city through Wednesday.

Texas Governor Greg Abbott told a news conference that new tornado warnings were expected.

Two people are confirmed to have died in the disaster, with that number expected to rise.

President Donald Trump plans to go to Texas on Tuesday to survey damage from the storm, a White House spokeswoman said.

aw/jm (Retuers, AP)