US President Trump visited flood victims in flood-soaked Houston, Texas, and Lake Charles in Louisiana Saturday as experts reiterated calls that local authorities rethink construction that leaves ground impervious.

Natural Resources Defense Council (NRDC) climate-change expert Joel Scata said Houston and its surrounding Harris County had been impacted hard by Hurricane Harvey because of shortfalls in urban planning.

"I am hoping that Harvey will be a wake-up call for how the US in general handles development," said Scata. "We don't have zoning restrictions in place so you don't have the best planning."

Researchers at Texas A&M [Agricultural and Mechanical] University said rapid urbanization of swamp lands since 1995 had drastically reduced the ability of local soils to absorb rainwater.

Harvey dumped an unprecedented 56 trillion liters, or 1.3 meters (51 inches) of rain over five days, inundating an estimated 136,000 buildings and led to the deaths of at least 44 people.

The storm's remnants have reached Ohio where it is forecast to merge with other weather systems on Sunday.

Back to school?

Up to 12,000 students would have to attend classes elsewhere when school resumed on September 11, Houston's school district Superintendent Richard Carranza announced Saturday while surveying damage as floodwaters receded.

Nearly a third, or 75, of the district's schools had suffered major or extensive damage and would not be ready to reopen for months, Carranza said.

Another 115 schools examined could be cleaned and would be ready to go. Damage was spread equally throughout the low-lying city, he said.

Houston Mayor Sylvester Turner, meanwhile, ordered evacuations of some 300 people remaining in western city areas still inundated by water being released from reservoirs.

In a semblance of normalcy Saturday, the Houston Astros baseball team returned to their home stadium, where a moment of silence was held for at least 44 people killed during the storm.

Congress to foot bill for clean-up

From Washington, the White House said in a statement that Trump had authorized a boost in the federal share of funding for hurricane aftermath debris removal and emergency protective measures from 75 percent to 90 percent.

The president had on Friday asked Congress for a $7.9-billion (6.6 million-euro) down payment - expected to be approved - toward Harvey relief and recovery efforts. The private meteorological agency AccuWeather estimated that Harvey's costs will exceed $190 billion, or about 1 percent of US gross domestic product.

Trump visits victims

Trump, who two weeks ago rescinded flood safety policy for federal infrastructure,  on Saturday visited a Houston shelter, alongside Texas Governor Greg Abbott, and chatted with displaced residents, including children - defying criticism from his first visit last Tuesday when he failed to meet with victims.

Trump on Saturday helped pass out relief supplies provided by Feed the Children and Red Cross, remarking to a volunteer coordinator: "I like doing this," and noting to first lady Melanie Trump, "This is good exercise."

"Is he going to help? Can he help," asked Devon Harris, 37, a construction worker sheltering at Houston's NRG convention center. "I've lost my home. My job is gone. My tools are gone. My car is gone. My life is gone. What is Trump going to do?"

President visits neighboring Louisiana

Arriving later at Lake Charles, Louisiana, where Harvey also dumped heavy rain, Trump told reporters that he hoped his request for immediate aid would be quickly approved by Congress when it returned from its five-week recess on Tuesday.

As water levels receded, numerous residents of Beaumont, a city of 120,000 east of Houston remained without piped water and waited in long vehicle queues to receive cases of bottled water.

Residents were urged to boil water before consumption.

Engineers are trying to restore service after two intakes of Beaumont's main water system were left damaged by the swollen Neches River.

Several hundred frustrated residents of Katy, a subdivision west of Houston, waved signs Saturday, demanding to be told when they would be able to return to their homes, which were still swamped because of reservoir releases of storm water.

The Associated Press quoted many as accusing authorities of sacrificing their homes to save others. Homeowner Sheetal Parwal, said her home was now a swamp and the family had less than when it immigrated from India 10 years ago.

Dioxin leaks from dump sites?

Focus also remained on more than a dozen petrochemical waste dumps outlying Houston, known as Superfund sites, designated as being among America's most contaminated places.

At Crosby, northeast of Houston and near the San Jacinto River, Associated Press said a small neighborhood between two Superfund sites had virtually disappeared.

Only a single house from among a dozen was still standing. A sinkhole the size of a swimming pool had opened up and swallowed two cars. Creosote odor filled the air, AP reported.

Another site east of Houston - the San Jacinto Waste Pits near the town of Highlands - had been covered by floodwaters so intense that an adjacent Interstate highway bridge had been closed in case it collapsed.

AP cited a federal Environmental Protection Agency (EPA) report of September last year which found that the riverbank site contained deposits of old paper mill waste containing dioxins and other long-lasting toxins that could become "highly mobile in a severe storm."

The EPA assessment said intense flooding could damage the site's protective cap, resulting in the "release of contaminants from the Site."

"If floodwaters have spread the chemicals in the waste pits then dangerous chemicals like dioxin could be spread around the wider Houston area, warned Kara Cook-Schultz of the consumer health and safety advocacy group TexPIRG.

ipj/sms (dpa, Reuters, AP, AFP)