Houston devastated by deadly flooding from Tropical Storm Harvey, more rain ahead

Catastrophic flooding triggered by Tropical Storm Harvey inundated Houston on Sunday, forcing residents of the fourth most populous US city to flee in boats or hunker down in anticipation of several more days of "unprecedented" rainfall.

Harvey came ashore late on Friday as the most powerful hurricane to hit Texas in more than 50 years and has killed at least two people. The death toll is expected to rise as the storm triggers additional tidal surges and tornadoes, with parts of the region expected to see a year's worth of rainfall in the span of a week.

The storm turned roads into rivers and caused chest-deep flooding on some streets in Houston as rivers and channels overflowed their banks. More than 66 cm of rain had fallen in parts of Houston in the past 48 hours, the National Weather Service said on Sunday, with more on the way.

Harvey struck at the heart of the country's oil and gas industry, forcing operators to close several refineries and evacuate and close offshore platforms. The massive flooding knocked out 11 percent of US refining capacity and a quarter of oil production from the US Gulf of Mexico.

"What we're seeing is the most devastating flood event in Houston's recorded history. We're seeing levels of rainfall that are unprecedented," said Steve Bowen, chief meteorologist at reinsurance firm Aon Benfield.

Residents use a truck to navigate through flood waters from Tropical Storm Harvey in Houston, Texas, US August 27, 2017. Reuters

Total precipitation could reach 127 cm in some coastal areas of Texas by the end of the week, or the average rainfall for an entire year. The centre of Harvey was about 170 km from Houston and forecast to arc slowly toward the city through Wednesday.

Floodwaters rose swiftly in Houston and emergency services told the city's 2.3 million inhabitants to climb onto the roofs of houses, if necessary.

"The water was right at our door," said Jasmine Melendez, a 23-year-old mother of three, including a week-old infant. "We were also worried about the kids, especially the baby."

Disaster areas declared

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

Trump, facing the first big US natural disaster since he took office in January, signed a disaster proclamation on Friday, triggering federal relief efforts. Texas Governor Greg Abbott said on Sunday 54 counties had been declared state disaster areas.

A rescue helicopter hovers in the background as an elderly woman and her poodle use an air mattress to float above flood waters from Tropical Storm Harvey while waiting to be rescued from Scarsdale Boulevard in Houston, Texas, U.S. August 27, 2017. Reuters

People in Houston and other areas of Texas were asked not to leave their homes, even if they were flooded, because roads were impassable.

Houston's George Bush Intercontinental Airport, one of the nation's busiest, and William P Hobby airport halted all commercial flights on Sunday. Nearly 1,500 flights in and out of Houston were cancelled due to the storm, tracking service FlightAware.com said.

The Gulf is home to almost half of the nation's refining capacity, and the reduced supply could affect gasoline supplies across the US Southeast and other parts of the country. Shutdowns extended across the coast, including Exxon Mobil's Baytown refinery, the second largest US refinery.

Area residents use a kayak to rescue motorists stranded on Interstate highway 45 which is submerged from the effects of Hurricane Harvey seen during widespread flooding in Houston, Texas, U.S. August 27, 2017. Reuters

Gasoline futures rose as much as 7 percent in early trading on Sunday evening. Heating oil futures, a proxy for distillates like diesel fuel, were up as much as 3 percent, with supplies expected to be curtailed.

The outages will limit the availability of US crude, gasoline and other refined products for global consumers and further push up prices, analysts said.

All Houston port facilities will be closed on Monday because of the weather threat, a port spokeswoman said on Sunday night.

"It keeps raining"

Hundreds of people like Melendez and her children were sheltering at the downtown George Brown Convention Center, where they sought water, food and baby supplies. Some people were being brought to the centre in city dump trucks.

The Harris County Sheriff's Office rescued more than 2,000 people in the greater Houston area using vehicles including motorboats, airboats and humvees on Sunday, a spokesman said.

The US Coast Guard and Houston police rescued hundreds more as residents brought boats to staging centres to help.

Texas National Guard soldiers aid stranded residents in heavily flooded areas from the storms of Hurricane Harvey in Houston, Texas, U.S., August 27, 2017. Lt. Zachary West, 100th MPAD/Texas Military Department/Handout via Reuters

Forecasters could only draw on a few comparisons to the storm, recalling Hurricane Katrina, which devastated New Orleans and killed 1,800 people in 2005, and Tropical Storm Allison.

Flood damage in Texas from Hurricane Harvey may equal that from Katrina, the costliest natural disaster in US history, an insurance research group said on Sunday.

The Harris County Flood Control District said Harvey's impact would rival that of Allison, which dropped more than 102 cm of rain in Texas in June 2001, flooded 70,000 homes and caused $9 billion in damage.

Harvey hit Texas as a Category 4 hurricane with winds of 210 km per hour, the strongest storm to hit the state since 1961. About 70,000 customers were without power by Sunday evening, according to Centerpoint Energy.

Two deaths had been confirmed so far - one in Rockport, 50 km north of Corpus Christi, and one in west Houston on Saturday. The Twitter account for Harris County 911 said people should not call if their lives were not threatened.

Evacuees are unloaded from the back of an open bed truck at the George R. Brown Convention Center after Hurricane Harvey inundated the Texas Gulf coast with rain causing widespread flooding, in Houston, Texas, U.S. August 27, 2017. Reuters

Houston's schools were scheduled to close for the week, the school district said on Twitter. ConocoPhillips will close on Monday and Tuesday, the company said.

The Federal Emergency Management Agency said it had more than 400 rescue personnel in South Texas, and 500 others were in the state and expected to join rescue operations on Sunday night.

Jose Rengel, a 47-year-old construction worker who lives in Galveston, was helping with rescue efforts in Dickinson, southeast of Houston, where he saw water cresting the tops of cars.

"I am blessed that not much has happened to me, but these people lost everything. And it keeps raining," he said.

"The water has nowhere to go."