Harvey dumped 19 trillion gallons of water on Houston

Reason:

"The real villains in Harvey flood: urban sprawl and the politicians who allowed it," reads a Guardian headline. "Houston is Drowning—In Its Freedom From Regulation" says Newsweek. Outlets like the Washington Post have pointed the finger at Houston's "wild west growth", spurred by a lack of comprehensive urban planning, as a reason for the severity of the recent floods.

The claim being made is the absence of zoning—making Houston unique among major American cities—has allowed developers to pave over with impermeable concrete otherwise absorptive prairie and wetlands, thus preventing them from soaking up storm water exacerbating flooding.

The idea's surface plausibility falls apart in the specifics.

According to one estimate, Houston's paving over of wetlands cost it the ability to absorb four billion gallons of water. Hurricane Harvey dumped 19 trillion gallons of water on the city.
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"The way that zoning has been used in most places is to deter density," Lehmann tells Reason. While Houston is the only major city to not have zoning regulation "most of the country looks like Houston, and, much like Houston, has sprawl."

When compared to other major U.S. cities, Houston actually has more permeable land, not less.

Only 39 percent of the city's land is taken up by impervious surface coverings according to U.S. Forest Service data. That's compares to 41 percent in New Orleans, 54 percent in Los Angeles, and 61 percent in New York City—all cities with traditional zoning regulations.

Houston's lack of zoning—far from causing damage to the city—may also help it rebuild faster than other cities seriously damaged by storms.

"I think it will actually be a more dynamic rebuilding which you wouldn't see in places that have a more traditional zoning code," says Vanessa Brown Calder, an urban policy analyst with the Cato Institute, tells Reason. "There is just a lot more ability to move and make changes given what they've learned from the damage associated with the storm."
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It is impossible to zone for a 19 trillion gallon rain fall anywhere. What is happening here is that liberals are trying to find a way to criticize one of the most dynamic cities in the world.  It looks like they are swinging and missing.