In Harris county, where Houston is located, one-in-three residents live below the poverty line and many have homes built in low-lying areas that repeatedly flood. "Because this is Texas you'll probably do it in six months", he said, winning a roar of approval from the gathering.
Harvey has been blamed thus far for at least 42 deaths and tens of billions of dollars of damage.
Harvey made landfall Friday night and has since broken the U.S. record for rainfall from a single storm, CNN senior meteorologist Dave Hennen said - with some areas of the state seeing nearly 52 inches of rain. Local officials expect the grim discoveries of additional bodies once the floodwaters retreat and the streams, rivers and bayous go back into their banks. Yesterday we had water and today it's all swept up and cleared up.
As of Friday morning, the fund exceeded $13.5 million. "But still so much to do".
Long said 32,000 people were in 230 shelters, with another 1,800 people housed in hotels.
People in Texas had mostly positive things to say about the president's visit there, though at least one resident accused him of engaging in a publicity stunt.
People launch boats from an overpass into floodwaters in the aftermath of Tropical Storm Harvey in Kountze Texas
Removing debris was also essential, the Houston mayor said.
Mr Turner also asked the Federal Emergency Management Agency (FEMA) to provide more workers to process applications from thousands of people seeking government help. "You can't leave it out there".
Trump appeared relaxed as he posed for photographs with volunteers and chatted with those relocated to the shelter alongside Texas Governor Greg Abbott. He said 8,500 people had been rescued from the floodwaters.
Some of the affected houses have several metres of water in them, and the water reaches to the rooftops of others, district meteorologist Jeff Lindner said.
A major hospital in Beaumont began evacuating its 200-odd patients on Thursday after the water cut out and a dozen premature babies were airlifted out on Friday.
"We hope that these games can serve as a welcome distraction for our city that is going through a very hard time", Astros president Reid Ryan said.
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