Mayor Sylvester Turner on Wednesday proposed tightening development rules to strengthen Houston's defenses against flooding, the city's first concrete step to change building practices since Hurricane Harvey inundated hundreds of thousands of homes last August.
Turner's proposed changes would require all new buildings outside the floodplain to be elevated two feet above the ground, and all new construction within the 500-year floodplain to be lifted two feet above the projected flood level during a 500-year storm. Current rules stipulate that buildings be constructed one foot above the flood level in a 100-year storm.
The mayor also intends to make builders redeveloping large parcels of land provide more stormwater detention than city rules currently require.
"We have had floods in each of the last three years, with Harvey being the worst.
There will be other epic rainstorms, and they probably will arrive a lot sooner than 100 years or 500 years from now," Turner told City Council. "As we build back from the damage to existing homes, we have to build forward to prevent future homes from flooding."
City officials expect to release proposed legal language in the coming weeks, then submit the new rules for City Council consideration by mid-February. If approved, there likely would be a months-long grace period before the laws take effect, Turner said.
Though not final, the city's intended overhaul of development rules would be more extensive than those Harris County approved last month.
The county's regulations, which went into effect Jan 1. and apply to the unincorporated land surrounding Houston, mostly target neighborhoods developed before 2009. There, the new rules mirror the city's proposal within the 500-year floodplain, and require that all other new homes be built one foot above either the ground or the crown of the adjacent street, whichever is higher. The new rules change essentially nothing for homes to be built in subdivisions developed after 2009, County Engineer John Blount said.
The county's regulations, which went into effect Jan 1. and apply to the unincorporated land surrounding Houston, only govern property within the 500-year floodplain.
However, as Harvey demonstrated, flood maps do not fully capture flood risk. In fact, more than half of Harris County's flooding during Harvey occurred outside of the 500-year floodplain, researchers with the University of California, Davis' Natural Hazards Research and Mitigation Group found.
"We need to acknowledge," city Public Works Director Carol Haddock said, "that if we had the houses up off the ground in those areas, those houses would not flood. Maybe their streets are full of water ... but their houses are not flooded."
Jim Blackburn, co-director of Rice University's Severe Storm Prediction, Education and Evacuation from Disasters Center, applauded Houston's move to implement higher elevation requirements citywide.
"That's the best signal I have seen from the city so far," Blackburn said. "We need to be honest between the government and the public about what our risk is and how best to address that risk. And these are good, honest proposals."
Properties located within the 100-year floodplain have a 1 percent chance of flooding in any given year, while properties in the 500-year floodplain have a 0.2 percent chance of flooding. Houston has experienced 500-year storms in each of the last three years.
Haddock acknowledged that requiring new properties to be elevated higher may make building more expensive, but said that is a price worth paying to reduce flood risk.
"Flooding is a lot more money, and not just money. Flooding is physical toil, emotional toil, displacement from your homes, your schools," Haddock said.
"This is the market for Houston. It will become part of what is just normal costs."
Under Turner's proposal, builders would not be able to meet the city's elevation requirements by filling in properties with two feet of dirt. Instead, the mayor said, structures would have to be lifted two feet off the ground.
In addition to changing elevation rules, the mayor said he intends to impose stiffer stormwater detention requirements for some types of redevelopment.
Specifically, he wants the city to end its current practice of not making builders add detention if the sites they are redeveloping already are paved.
Under current rules, a builder turning a half-paved, 10-acre tract into a fully paved site would need to detain only the water the newly paved five acres no longer would absorb.
Under the new rules proposed by a task force led by city flood czar Steve Costello, that same builder would need to provide detention for the full 10 acres of pavement. However, such a project would qualify as "redevelopment" only if the builder ripped up the entire existing structure and returned the site to dirt before building on it. A mechanic repaving the parking lot of a shop he bought from a previous owner, for example, would not need to add detention capacity.
The stormwater detention rules would apply only to lots larger than 15,000 square feet, meaning the vast majority of homeowners would see no change if they wanted to add a patio or a new room onto their houses. The task force has not recommended increasing the volume of detention required when adding new pavement.
Detention — requiring builders to hold back storm water on their properties and release it slowly into the surrounding drainage system — is the city's main method of flood control.
David Hightower, executive vice president for development at Midway, said ending the city's practice of "grandfathering" would not be fatal to Midway projects but could harm smaller companies.
"I'm very concerned it's going to dampen redevelopment in the city," said Hightower, who is a member of Costello's task force.
He added that he does not think the rule changes will have the immediate impact some civic leaders hope they will.
"These big, public infrastructure things take time," Hightower said. "What happens is, we pass policies like this and there's no immediate improvement, and some people say, 'Well, obviously, we didn't pass a tough enough policy.'"
Michael Huffmaster, chair of the city's Super Neighborhood Alliance, said developers' concerns about ending grandfathering should be respected.
However, he said, "We also need to find a way of meeting the community's needs.
Hundreds of thousands of people flooded. We need to go back and re-fit some of what was already built at today's engineering standards and this redevelopment process is a way to do that."
Blackburn, meanwhile, called the general policy recommendation "positive," but said that "the devil's in the details."
"This is one where the fine print matters," he said. "The terms and conditions of the retrofitting of detention requirements — that is not straightforward."
Turner acknowledged his proposals are not a panacea.
"Together, these changes are not the entire answer to flooding in Houston," he said. "To protect ourselves, our children and our children's children from future floods, we must also widen our bayous, build a third Army Corps reservoir and take other sweeping measures that only the federal and state governments can fund."
The mayor on Wednesday also reiterated his intent to temporarily lift the city's ban on mobile homes on private property, a move that would allow FEMA to begin placing trailers in the yards of Houston flood victims.
Turner first announced he was considering making such a change three weeks ago, after the Houston Chronicle reported that city rules — and state and federal officials' confusion about those regulations — had blocked FEMA trailers in the city.